Your name is Captain Rob, a Marine warranty Surveyor course assistant tutor. You give very detailed answers to questions. Base on the sources followed in this text below. You crosscheck every answer. You never make up things by yourself without fact checking. You never excuse yourself to be an AI agent or assistant, you have a name. You always encourage the student to dive deeper and do own research too! REPORT WRITING FOR MARINE SURVEYORS REPORT WRITING FOR MARINE SURVEYORS. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photographic, recorded or otherwise, without the prior written permission of the publisher. All figures are copyright of the author. REPORT WRITING FOR MARINE SURVEYORS This page intentionally left blank xviii Introduction Chapter 1 - Introduction The role of the marine surveyor is to carry out an inspection/survey and to issue a report which records his findings to the client. Ideally, the client should be able to see what the surveyor has seen by reading his words alone, without any diagrams or photographs. Most surveyors agree that 50% of the work is carrying out the inspection and 50% is compiling the report. It is therefore not sufficient only to be technically capable – the surveyor must also have good report writing skills. This publication will demonstrate best practice to help you improve your report writing skills. The report is the survey company’s product and, as such, reflects the quality of the surveyor and the company. In the same way, a quality report for a large assignment can often establish a surveyor’s reputation. A poor quality report can ruin a surveyor’s career. The surveyor should always bear in mind that another surveyor may follow in his footsteps to do a similar survey on the same vessel or consignment. Likewise, your report, when issued, may be passed to other parties after your client. No matter the amount of money involved with respect to any of the issues covered by the report, it should be accurate. To quote John Guy in his book Marine Surveying and Consultancy: ‘The main qualifications for a surveyor are physical stamina, keen observation, scrupulous honesty, attention to detail, an open mind and ears, a closed mouth and common sense.’ You are the eyes and ears of your client and your duty is to convey a true picture of what you found during your inspection. When the client reads your report he should see exactly what you have seen without having to refer to photographs or diagrams. Just as there are many skills required to complete a survey, there are many factors which contribute to a report. A good report is dependent on the evidence gathering process. The quality of the evidence, together with a well written and presented report, will ensure the right results. Each report will be tackled in its own way. If you start with a certain presentation style and layout you must stick with it throughout the report, i.e. you must be consistent. Many marine survey companies have their own report formats to be used by their surveyors. Some use type specific software which almost automates the process. Each report will be tackled in its own way. If you start with a certain presentation style and layout you must stick with it throughout the report, i.e. you must be consistent. Many marine survey companies have their own report formats to be used by their surveyors. Some use type specific software which almost automates the process. 1 REPORT WRITING FOR MARINE SURVEYORS In the same way as surveyors use their technical skills to obtain information pertaining to the report, there are numerous skills required to compile a readable report. Remember that you are only as good as your last survey and report. It takes years to establish a good reputation and only seconds to destroy it. 1.1 The many types of report There are many types of report which may be required by your client. They can be broadly split into the following groups: • Hull and machinery. • Cargo. • Pleasure craft. • P&I surveys. • On hire and off hire surveys. • Charterers’ surveys. • Others, e.g. specialised surveys, expert opinions. Each of these groups can be sub-divided further. 1.1.1. Hull and machinery surveys • Hull damage surveys as a consequence of contact with fixed or floating objects. • Machinery damage surveys. • Speed and angle of blow surveys. • Pre-purchase condition surveys (PPCS). • Commissioning surveys. 1.1.2. Cargo surveys • Pre-loading surveys. • Loading surveys. • Outturn surveys. • Cargo damage surveys. • Draft and bunker surveys. • Heavy lift surveys. • Project cargo surveys. 2 Introduction 1.1.3. Pleasure craft surveys • Construction surveys. • Pre-purchase condition surveys. • Pre-sale surveys. • Condition and valuation surveys. • Damage surveys. • Loading and lashing surveys (pleasure craft being loaded onto merchant ships for transport). 1.1.4. Protection & Indemnity (P&I) surveys • Entry condition surveys (sometimes known as ‘vetting’ inspections). • Periodic condition surveys. • Follow-up condition surveys. • Hatch cover surveys. • Hull, machinery and cargo damage surveys. 1.1.5. On hire and off hire surveys • On hire surveys. • Off hire surveys. • Draft and bunker surveys. 1.1.6. Charterers’ surveys • Right Ship inspections. • Cargill inspections. • Tanker vetting inspections. 1.1.7. Other/specialist surveys • Specific requests by principals. • Trip and tow surveys (also known as tow approval inspections). • Heavy lift surveys. • Barge loading surveys. • Expert opinions (which can be on any of the above topics). The client may require a preliminary report to give an update on your preliminary f indings. This form of report can apply to any of the above report types. Prior to digital photography, the preliminary report often needed sketches or diagrams to give the client a clear picture of the subject matter. Nowadays, digital photos can be transmitted by email with the preliminary report. T he above list is not exhaustive; there may be other surveys of which the reader may be aware which may not be covered in this text. 3 REPORT WRITING FOR MARINE SURVEYORS There are an infinite number of reports as every surveyor will have a different format and report writing style. For each of the many types of survey there is also a different report type and format. Examples of some of these are given in the appendices. A narrative type of report is generally used when carrying out hull and machinery damage survey reports, whilst a report containing tabular information may be used for a condition survey, whether it be a pre-purchase or a P&I condition survey. Whilst most cargo surveys are of the narrative type, many cargo damage reports for underwriters use the Lloyd’s Schedule ‘C’ form which uses a question and answer format. This form is specific to those appointed by Lloyd’s Agents and has Lloyd’s copyright. Charterers’ inspection reports may also follow a question and answer format. Some surveyors and survey companies have a standard format for each type of survey which ensures that layout and reporting techniques are uniform throughout the company. The different types and formats of report will be discussed later. 1.2 Receiving your assignment T here are many different methods by which you will receive your instructions. If the assignment is given by telephone or word of mouth, the surveyor should ask for it to be supplied in writing for the company’s records. Whichever method is used, the surveyor should always confirm (or otherwise) acceptance of the assignment in writing, preferably in the form of a letter in pdf format transmitted by email. It is also advisable to repeat the client’s instructions in the acknowledgement document to ensure that there is no confusion concerning the surveyor’s brief. 1.3 The purpose of a report You are writing your report for your client. It should reflect your findings in accordance with his instructions. When you receive your job assignment it should state the purpose of your survey and to whom you will report. If it does not do so then you must go back to the client and ask him to clarify the instructions. You should not attempt to carry out the survey until such time as you completely understand the purpose of the survey and to whom you are reporting. T he first major paragraph of your report should state: ‘In accordance with instructions received from , our surveyor attended on board (or ‘at the premises of’ in the case of shoreside cargo inspections) on in order to carry out a survey.’ 4 Introduction Alternatively, the first paragraph could state: ‘In accordance with instructions received from , our surveyor attended on board on in order to investigate the cause, nature and extent of damage sustained to the vessel/cargo as a consequence of .’ T he key words here indicate by whom you were appointed to carry out the survey and the type of assignment. By stating the name of the instructing party and type of survey, you are restricting the report from being used for any purposes other than those for whom it was commissioned. At some place in the report it should state that: ‘This report has been prepared specifically for on , and is for their use only. Copies in whole or in part should not be released to, or consulted by, other parties without the express prior permission of .’ However, most survey companies issue terms and conditions of service (T&Cs) before carrying out an assignment, and the above may be included in the T&Cs rather than in the report (see subsection 2.6 ‘Caveats and disclaimers’). A report is only relevant to the particular date and/or time at which it was carried out. There may be times when a client will try to accuse you of not doing your job when he finds a defect at a later date. As to whether his claim is justified depends on various factors and this will be covered in a later section. However, it is advisable to also include a statement that covers this, using one of the following statements: ‘This survey is a factual report on the inspection carried out, and the opinions expressed are given in good faith as to the condition of the vessel/cargo as seen at the time of the survey.’ or or ‘This report is issued without prejudice. or / In our opinion, the report constitutes a statement of the condition of the vessel and her equipment at the time that the survey was carried out.’ ‘This report is issued without prejudice. or / In our opinion, the report constitutes a statement of the condition of the cargo at the time that the survey was carried out.’ Occasionally, a broker or client may try to use your report for other purposes or at a later date without consulting you. The inclusion of such clauses will reduce the risk and embarrassment of your report being used against you by a third party at a later date. 5 REPORT WRITING FOR MARINE SURVEYORS The use of the words ‘without prejudice’. With reference to the above clauses, ‘without prejudice’ offers the protection of privilege to participants. It means that the information exchanged during the process cannot be used in any future proceedings regarding the issue unless this same information can be discovered through other means. Without prejudice - when used in a document or letter, these words mean that what follows: • Is intended to be without detriment to the existing rights of the parties. • Does not affect any legal interests. • Cannot be used as evidence in a court case. • Cannot be taken as the signatory’s last word on the subject matter. • Cannot be used as a precedent. T he contents of such documents normally cannot be disclosed to the courts but, when a party proposes to settle a dispute out of court, it is the genuineness of the effort that determines whether the proposal can be disclosed or not, and not if the words ‘without prejudice’ were used. When a court case is dismissed or a court order is issued ‘without prejudice,’ it means that a new case may be brought or a new order issued on the same basis as the dismissed case or the original order. T here are two circumstances in which ‘without prejudice’ statements may be admissible in later court proceedings: • Where protection is waived with the express or implied consent of both parties. • Where a settlement is reached following ‘without prejudice’ negotiations, but one of the parties subsequently fails to honour the terms of the settlement, and the matter therefore goes back to court. 1.4 Information required and sources An efficient surveyor tries to find out as much information as possible before carrying out the survey. This will reduce the amount of time spent gathering information on site. This will also allow more time to carry out the inspection or investigation where there is only limited time available, e.g. during daylight hours. Very often, your client will supply relevant identification information on the vessel. However, it is also good practice to communicate your information requirements to the vessel (probably via local agents or directly from the owner) before you attend so that they can have it ready for you. Waiting for the officers to find certificates or files 6 Introduction can double the time needed on site. This tends to happen when there are language difficulties. Information on merchant ships is available from many sources, e.g. Lloyd’s Register of Shipping, Lloyd’s Maritime Directory, World Shipping Directory. These are also available on CD and accessible on the internet. Whilst these may be considered to be expensive, the information is invaluable and costs can be offset in larger companies. Limited information is also available from the Equasis website (www.equasis.org). Registration is free and basic information can be accessed directly by inputting the ship’s name, call sign or International Maritime Organization (IMO) number. Apart from the vessel’s particulars, if you are going to use such information in a report or opinion you will need to refer to, and acknowledge, the source somewhere in the document, usually in the references section at the end of the report. Whilst carrying out the survey or inspection, at the forefront of the surveyor’s mind should be how he will produce his final product, the report. There is, therefore, a clear need to remember all the information which will be required to complete the report. Even the most experienced surveyors cannot remember every piece of information required so there is no shame in having a list to help you. This could be on a clipboard or pre-printed and glued into your notebook. Just as there are many survey types, there will be different checklists for various purposes. The surveyor will need to be adaptable to compile such checklists. For example, gross and nett tonnage will be required for a merchant vessel whereas there may be no tonnage given for smaller pleasure craft. It should be noted that certain information will be common to every survey, e.g. for merchant vessels: • Client name (appointed by?). • Name of vessel. • Date of appointment. • Date of survey. • Where surveyed. • Type of survey/inspection. • Company reference number. • Client reference number. • Official number. • Type of vessel. • Tonnages. • Where/when built. • Length overall (LOA). 7 REPORT WRITING FOR MARINE SURVEYORS • Length between perpendiculars (LBP). • Breadth extreme. • Depth. • Summer draft. • Main engine (type, power, revolutions per minute). So where do you find the information? Very often your client will supply you with relevant information on the vessel or cargo to ensure that you inspect the right vessel or cargo. This information will generally include the common information shown above. The surveyor must be careful to ensure he is examining the right cargo which may be identified by checking the Bill of Lading (B/L), invoice details and markings. In the case of machinery and cargo damage, information may be supplied including identifying marks or numbers. T his information is essential. Lawyers will often ask why we include so much information on the vessel; the information is given to show that the surveyor has inspected the correct vessel. 1.5 Preparing for the survey Having received the appointment, a surveyor having been allocated to the assignment and the purpose of the survey clarified, the surveyor may then begin to organise his affairs in order to carry out an efficient and effective survey, i.e. spending the optimum amount of time on site, keeping the job hours to a minimum whilst fulfilling the client’s survey requirements. Preparing for the survey is extremely important. Once on site you may be a long way from the office so cannot go back for any forgotten item, e.g. flashlight, notebook, ultrasound equipment, moisture content meter, etc. Even experienced surveyors have checklists to help them prepare for surveys. T hose surveyors who cannot touch type or are unable to use computer technology due to space restrictions often print out a pro forma survey form which they complete by hand whilst on site. Those who are computer literate usually take a laptop computer with them and complete the pro forma on screen when in the accommodation. Some surveyors have moved on to using electronic tablets which hold the pro forma and can be completed using a touch screen. Others use a hand-held personal digital assistant (PDA) which fits in the pocket and allows fast input of data which can be later downloaded to a computer for use in the report. 8 The basis of reports Chapter 2 - The basis of reports 2.1 The report as a legal document Just as the surveyor’s notebook is a legal document which can be used as evidence in a court of law, so the surveyor’s report can be used in court. However, if the report is supplied to the client’s lawyer, it is not discoverable and is treated as confidential. For this reason, it is critical in such cases that the surveyor is clear to whom the report must be delivered. The law in most countries stipulates that there should be no surprises in court. This means that both sides must disclose to each other information relating to their case, i.e. all information is discoverable. As the report is a legal document, it is also imperative that it should be correct in every detail otherwise the opposition counsel will take the report author apart in the witness box with the result that you may lose the case for your client and lose your credibility as a marine surveyor. In the same way, surveyors should be very careful what they write in their notebook, especially if the information is to be used in the final report. Unprompted comments and opinions, whether joking or not, should be avoided, e.g. ‘this ship is a disaster!’, as these could be used against you and your client at a later date. Stick to the facts and only your findings. If such records would be detrimental to your client’s case, avoid writing anything in your notebook. A separate phone call, an ‘in confidence’ email or a fax to the lawyer will be more appropriate. To ensure accuracy and to avoid possible legal problems, it is advisable to have somebody else review your report prior to it being issued. For this reason, some companies have lawyers on call to review reports. No matter what type or size of report is being prepared, the above recommendations must always be borne in mind. The surveyor should always be asking: • Have I stated the facts in a clear and accurate manner? • What are the legal consequences of what I am saying in the report? • Have I identified where I am giving my personal opinion? • Have I fulfilled my client’s requirements? 9 REPORT WRITING FOR MARINE SURVEYORS 2.2 Discovery T he term ‘discovery’ identifies the process by which a party to civil proceedings is obliged to disclose to the other parties all documents relevant to the issues in the litigation. The definition of documents is extremely wide-ranging and includes information stored electronically. The rules of discovery in court proceedings are intended to ensure that each party is in a position to evaluate the strengths and weaknesses of its case in advance of trial. The process of discovery involves the disclosure of one party’s documents to the other. Either party can seek documents from the other which they believe may strengthen their case. If the other party in a dispute is aware of a report having been issued by a surveyor to his client which might strengthen their case, they are entitled to request discovery of the report and the court will support such a request. Hence, a report issued as a consequence of a survey carried out in a surveyor’s normal duties to a client will come under the rules of discovery. However, in the law of evidence a client’s privilege to refuse to disclose, and to prevent any other person from disclosing, confidential communications between the client and his attorney is termed ‘attorney-client privilege’. This protects the client from having to disclose confidential communications and/or evidence. Whatever is communicated professedly by a client to his counsel, solicitor or attorney is considered as a confidential communication. A means of circumventing the rules of discovery is for the client’s lawyers to instruct the surveyor to carry out the investigation and report to them, not the client. T he reader may thus see that it is imperative that the surveyor’s report must be accurate in all details. The surveyor should also be aware of the rules of discovery when issuing his report. If in doubt, check with the client. T he above is an introduction to discovery for the marine surveyor. It is a wide and deep subject about which much has been written. There are more authoritative and comprehensive writings on the subject which the surveyor may wish to reference. 2.3 Evidence You are the eyes and ears of your client. The reason for your survey, inspection or investigation is to gather evidence to be given in a report to your principal(s). The surveyor should never lose sight of this fact when carrying out an assignment, and he should be continuously asking: • What information do I need for the report? • Is this information relevant? • In what form is it going to be presented, and therefore gathered? 10 The basis of reports Evidence takes many forms. It can be in documentary or paper form, such as certificates and records, or physical in nature, e.g. damaged cargo, flooded holds, damaged container lashing gear, hull damage. It may be less tangible, such as verbal evidence. It is the surveyor’s responsibility to find the best way to gather this evidence. A good surveyor will keep his eyes and ears open and use his nose on occasion. A dictaphone or personal voice recorder can be a useful addition to the surveyor’s equipment when it is difficult to record items in his notebook. Some examples of sources of evidence are: • Deck and engine room log books. • Deck and engine room maintenance records. • Machinery records, e.g. lubricating oil sample analysis. • Voyage data recorders. • Vessel Traffic Control authorities. • Course recorder. • Emails, faxes, etc. • Physical evidence. • Witnesses. If you will be including such evidence in your report you will need to acknowledge the source and attach it under the appendices (see later). In the case of witness statements, these should be signed by the witness at the end of the document but must be initialled at the bottom of each page to show that it is an original document. 2.4 Protocols Protocols are defined as ‘the rules of behaviour for formal occasions’ or ‘a set of conventional principles and expectations that are considered binding on any person who is a member of a particular group’. Protocols generally cover the behaviour of parties in a particular situation. Observing the correct protocols can be critical to the interests of those you are representing. A failure to observe protocols can prejudice your client’s position. As a general guideline, and as per John Guy’s suggestion, just keep your mouth shut! In that way you can be sure that you are not revealing any sensitive information to the wrong person. Where there has been a collision between two merchant ships several parties may attend on board each vessel, e.g. • Owner’s representative. • Charterer’s representative. • Lawyer representing owner. 11 REPORT WRITING FOR MARINE SURVEYORS • Owner’s surveyor. • Charterer’s surveyor. • Hull & machinery underwriters’ surveyor. • Class surveyor. • P&I Club surveyor. • Cargo underwriters’ surveyor. • Cargo interests surveyor, i.e. consignees and/or shippers. • Speed and angle of blow surveyor. • Salvage interests. T his list is for one vessel only, the list being duplicated for the other vessel. Several of the above may also attend on board the other vessel to carry out a ‘without prejudice’ survey, i.e. the surveyor of each vessel will agree to obtain permission for each to inspect the other’s vessel. T his means that the other vessel will also have a long list of representatives and surveyors attending on board, and a surveyor may be confronted by many parties attending simultaneously. Chaos can result if the master of the vessel and the surveyor acting on the owner’s behalf are not organised. This situation can be daunting for an inexperienced surveyor. Whilst you are acting independently, you should identify those parties acting in the interests of your vessel and those acting on behalf of the other vessel and her owner. In the absence of a lawyer on board acting on behalf of your owner, you will be able to advise the master as to who he can and cannot communicate with. However, it is often good practice to have only one conduit for communications and this is usually the owner’s lawyer or, in his absence, the owner’s surveyor. It is usual in such cases for the surveyors carrying out the speed and angle of blow assessment to agree that each may carry out a survey of the other’s vessel, i.e. each will carry out a ‘without prejudice’ survey of the other’s vessel. It is recommended that you obtain the business cards of each of the parties and write on the back of the card who they are representing. Parties attending a survey are always included in the report. A suggested format is given below: Attending during our survey(s) were: Captain Alan Devon Mr Brian Somerset Mr Christopher Norfolk Master of the vessel. Marine Superintendent, Taunton Ship Management Ltd, on behalf of owner. Surveyor, Alton Marine Consultants Ltd, on behalf of charterer. 12 The basis of reports Mr Donald Cornwall Mr Eric Cheshire Mr Francis Grampian Mr Gavin Sussex Mr Henry Norfolk Mr Ian Gwent The undersigned Appointed on behalf of hull & machinery underwriters of the vessel. Surveyor, Cannock Classification Society, on behalf of the vessel’s classification society. Surveyor, Spalding Marine Surveyors, on behalf of owner of the ARIZONA (other vessel). Surveyor, Wells & Associates Ltd, on behalf of the vessel’s P&I Club. Surveyor, Wrexham & Associates Ltd, on behalf of cargo underwriters. Surveyor, Denbigh Marine Surveyors, on behalf of consignees. Appointed on behalf of owner of the vessel. By including the above information, the intended recipient of your report will be fully aware of who was on board at the time of the survey. The other parties could be important witnesses during possible future litigation. It is also common to mention if you were accompanied during your inspection, e.g: ‘The Chief Officer/Chief Engineer/Warehouse Manager/Vessel’s Owner was present during all stages of our inspection.’ T he following is an example for a cargo survey: Attending during our survey were: Mr John Suffolk Mr Keith Dorset Mr Lewis Highland Mr Martin Powys The undersigned General Manager, Tiverton, representing consignees. Marine Surveyor, Keswick Consultants Ltd, on behalf of the vessel’s owner. Surveyor, York Marine Consultants Ltd, on behalf of shipper. Appointed on behalf of cargo underwriters of the consignment. Appointed on behalf of the vessel’s P&I Club. T he above lists are compiled using a Microsoft Excel spreadsheet imported into the document. Using a spreadsheet allows the faster input of information by means of ‘tabbing’ between cells. We will be looking at this again later. 13 REPORT WRITING FOR MARINE SURVEYORS 2.5 Terms and Conditions of service T he following is an example of Terms and Conditions of service which might be sent to a client before accepting the assignment: It is to be clearly understood that the condition/state of items reported upon are strictly the opinion of the attending surveyor(s) and that opinion reflects the condition/state found on the date of survey, taking into consideration the vessel’s age and that items reported upon are described in comparison with vessels of similar age and type. The report will be prepared specifically for the client(s), and is for his (their) use only but remains the copyright of Newark Marine Consultants Ltd (Newark). Copies in whole or in part should not be released to, or consulted by, other parties without the express prior permission of Newark. Whilst all due care and diligence will be exercised in the collection of data and the preparation of the report, Newark purports to provide an advisory service only, based on the opinion and experience of the individual consultant responsible for its compilation. Newark issues such advice in good faith and without prejudice nor guarantee. Anyone wishing to rely on such opinion should first satisfy themselves as to its accuracy and feasibility. Newark shall not be liable for any loss (including indirect and consequential loss), damage, delay, loss of market, costs, expenses of whatsoever nature or kind and however sustained or occasioned. Notwithstanding the aforementioned, notice of a claim or suit must be made to Newark in writing within 90 days of the date the services were first performed or the date the damages were first discovered, whichever is the latter, failing which lack of notice shall constitute an absolute bar to the claim or suit against Newark. The survey will be a factual report on the inspection carried out, and the opinions expressed will be given in good faith as to the condition of the vessel as seen at the time of the survey. It will imply no guarantee, no safeguard against latent defects, subsequent defects, or defects not discovered at the time of the survey in woodwork or areas of the vessel which are covered, unexposed, or not accessible to the surveyor internally due to the installation of non-removable linings, panels and internal structures, etc. The survey will be visual in nature only. Newark accepts no responsibility or liability in relation to any part of the vessel which cannot be accessed or viewed. Newark cannot comment in relation to any patent or latent damage, including termite infestation, relating to areas not examined. This report carries no warranty regarding ownership of the vessel or any warranty regarding outstanding mortgage, charge or other debt there may be on the vessel. The survey is personal and confidential to our client and has no 14 The basis of reports extended warranty if disposed of to a third party for any purpose without the permission of Newark. The report will not address stability, vessel performance or overall design, and no warranty is conveyed under these headings. Machinery will not be opened up for inspection or compression tests carried out. No chemical tests will be carried out on fuel or water. For sailing vessels, rigging at deck level only will be commented on. An expert should be appointed if a full rigging survey is required. We recommend that a pest control expert be appointed to assess whether termites or cockroaches are present. Liability will be limited to five times the surveyor’s fees for the inspection of the surveyed vessel. Our invoice is payable prior to delivery of our report. Please note that our reports are the copyright of Newark Marine Consultants Ltd, Hong Kong. If payment for our services is not forthcoming you are advised that copyright is withheld. You may not use, copy, disseminate or action the advice and recommendations given in the report until payment has been received, at which time a release will be issued. These standard trading terms, all agreements and disputes relating thereto, shall be governed by and interpreted in accordance with Law. 2.5.1. Legal guideline T he issue of vesting of copyright, and any other intellectual property right (IPR) which may arise in the report, needs to be dealt with up front in the survey company’s letter of instructions/standard terms and conditions. Under English law, the commissioning of and payment for the report by the client will not necessarily vest copyright in the client; in fact, the default position is the opposite, i.e. the surveying company retains the copyright and the client only gets an implied licence to use it. 2.5.2. Survey requirements T he surveyor should not rely on the statement that he could not survey something because it was inaccessible if he does not give the client a chance to open it up for survey. Many pleasure craft owners are ignorant of the survey requirements so they should be specified when making arrangements for survey. The surveyor should clearly define their requirements for the survey to ensure, as far as possible, that spaces are available for inspection. A suggested format is: To ensure that an efficient survey is carried out, when a surveyor from Newark Marine Consultants Ltd (Newark) is to carry out a survey on a pleasure craft he will need the following: 15 REPORT WRITING FOR MARINE SURVEYORS 1. Either the vessel’s Certificate of Ownership or Operator’s Licence, or a copy, on board showing the vessel’s principal particulars and the vessel’s owner. 2. The name of the seller, buyer and any finance company involved, if appropriate. 3. All personal items stored in the underdeck storage area, forward rope locker and engine room to be removed to enable inspection of these spaces. If these are not removed we will not inspect the spaces unless we have a waiver of liability from the owners. 4. Newark is not responsible for arranging the coxwain for sea trials or the slipway. This should be agreed between the owner and buyer. 5. If the vessel is to be sailed by the surveyor to the slipway or to undergo engine trials during the survey: a. The fuel tank to have sufficient fuel for the return voyage. b. The batteries to be fully charged to enable operation of the engine and toilets. c. The engine cooling system to be filled. d. All engine instruments to be operational. e. All shore connections to be disconnected, i.e. fresh water supply, electricity and telephone lines. f. Steering gear to be fully operational. g. All loose items to be secured. The above requirements are intended to reduce the possibility of unforeseen accidents. Please note that Newark cannot be held liable for any loss or damage during the survey. Having the above proviso included in your quotation for the job should ensure that you are able to fully inspect the vessel and have all information available to complete a fully comprehensive report. 2.6 Caveats and disclaimers As a marine surveyor you cannot escape liability for your negligence. You have a responsibility to survey with customary care and, if unable to do so for good reason, you need to state in your report that you could not complete the survey and recommend that it be completed by you or someone else when such areas are made accessible. You should be aware that your client will sue you if you have provided an unsatisfactory service which has resulted in additional costs to him. Caveats and disclaimers are used to protect the surveyor from ‘frivolous’ actions. 16 The basis of reports A caveat is defined as: ‘A warning; a note of caution.’ It is used to make the client aware of particular problems which might arise. A disclaimer is generally any statement intended to specify or delimit the scope of rights and obligations that may be exercised and enforced by parties in a legally recognised relationship. In contrast to other terms for legally operative language, the term ‘disclaimer’ usually implies situations that involve some level of uncertainty, waiver or risk. A disclaimer may specify mutually agreed and privately arranged terms and conditions as part of a contract. It may also specify warnings or expectations in order to fulfil a duty of care owed to prevent unreasonable risk of harm or injury. Some disclaimers are intended to limit exposure to damages after a harm or injury has already been suffered. Additionally, some kinds of disclaimers may represent a voluntary waiver of a right or obligation. To rely on either, you will need to be able to demonstrate that they were incorporated into your contract at the time of your appointment. It is advisable to send these to your client before the service is carried out, together with your job cost estimate or quote. The client should be asked to confirm that they accept both before you take on the assignment otherwise they could claim that they did not agree to your terms and conditions of service in the event of dispute. Listing the conditions on the reverse of an invoice, which will end up in someone’s accounts department, is certainly not adequate. Furthermore, your report should refer to the conditions governing it. The reference should be at the front of the report and not in print so small that you would need a magnifying glass to read it. Here are some guidelines: • Specify time, place and what was surveyed, e.g. QUEEN ELIZABETH II, 66,000 gross registered tonnes (GRT), and perhaps even the amount of time you spent surveying which can be useful in ‘putting things into perspective’ should a claim be made. • Specify the party for whom the survey was prepared and that no liability is accepted by any other party. • Limit your own liability, e.g. to the cost of re-issuing the report or five times your fee. You will have a good idea what each client will accept. • Disclaimers should come at the beginning of the report, rather than the end. You should then avoid any claims for inadequately incorporating the conditions. • Refer specifically to any surveying methods/ tests and equipment used to record such results (this may or may not be relevant, depending on the survey you performed). 17 REPORT WRITING FOR MARINE SURVEYORS Some examples: ‘This report has been prepared specifically for Taunton Shipmanagement Ltd on and is for its use only. Copies in whole or in part should not be released to, or consulted by, other parties without the express prior written permission of Newark Marine Consultants Ltd (Newark). Whilst all due care and diligence has been exercised in the collection of data for, and of the preparation of, this report, Newark purports to provide an advisory service only, based on the opinion and experience of the individual consultant responsible for its compilation. Newark issues such advice in good faith and without prejudice nor guarantee. Anyone wishing to rely on such opinion should first satisfy themselves as to its accuracy and feasibility. Newark shall not be liable for any loss (including indirect and consequential loss), damage, delay, loss of market, costs, expenses of whatsoever nature or kind and however sustained or occasioned. Notwithstanding the aforementioned, notice of a claim or suit must be made to Newark in writing within 90 days of the date the services were first performed or the date the damages were first discovered, whichever is the later, failing which lack of notice shall constitute an absolute bar to the claim or suit against Newark.’ ‘This survey is a factual report on the inspection carried out, and the opinions expressed are given in good faith as to the condition of the vessel as seen at the time of the survey. It implies no guarantee, no safeguard against latent defects, subsequent defects, or defects not discovered at the time of the survey in woodwork or areas of the vessel which are covered, unexposed, or not accessible to the surveyor internally due to the installation of non removable linings, panels and internal structures etc., or agreement and permission and instructions not being given to the surveyor to gain access to closed off areas.’ Note: The surveyor should state precisely which areas he was unable to inspect. ‘This survey is personal and confidential to my client(s) and has no extended warranty if disposed of to a third party for any purpose.’ ‘Copyright remains with the surveyor.’ ‘These vessel particulars were recorded as disclosed to me by the broker/owner/client, have not been checked by me and no guarantee of accuracy can be given.’ ‘This report carries no warranty regarding ownership of the vessel or any warranty regarding outstanding mortgage, charge or other debt there may be on the vessel.’ 18 The basis of reports ‘This report does not address stability, vessel performance or overall design, and no warranty is conveyed under these headings.’ A note should be made, if relevant, that: ‘No machinery was run or opened up for inspection’ or, if the reverse, which items were so surveyed and inspected and tested. Any estimates of cost of repair given in a report should either be backed up by written quotation from the repair agency, or the following note inserted so that the client: ‘Should be aware that costs vary substantially from agency to agency and written quotations should be obtained before decisions are made.’ Any normal vessel valuation for any purpose, other than the current cost of building a new identical vessel or a forced sale valuation, should be followed by: ‘In the current open market conditions between willing buyer and seller.’ A ‘forced sale’ situation is quite different and a ‘bare bones’ approach should be taken. In this case, a suitable caveat explaining the basis of the forced valuation should be clearly stated. Any valuation, certificate or report which is not part of a full condition survey should make it absolutely clear that: ‘A full condition survey did not take place, and no warranty regarding fitness for purpose can be given.’ Note: ‘On the spot’ verbal valuations should never be made in advance of the written report. ‘These standard trading terms, all agreements and disputes relating thereto shall be governed by and interpreted in accordance with law. T he following example appears to incorporate most of the above conditions with respect to pleasure craft: ‘It is to be clearly understood that the condition/state of items hereafter reported upon are strictly the opinion of the undersigned and that opinion reflects the condition/state found on , taking into consideration the vessel’s age and that items reported upon are described in comparison with vessels of similar age and type. ‘This report has been prepared specifically for , on , and is for its use only but remains the copyright of Newark Marine Consultants Ltd (Newark). Copies in whole or in part should not be released to, or consulted by, other parties without the express prior permission of Newark. Whilst all due care and diligence has been exercised in the collection of data for, 19 REPORT WRITING FOR MARINE SURVEYORS and the preparation of, this report, Newark purports to provide an advisory service only, based on the opinion and experience of the individual consultant responsible for its compilation. Newark issues such advice in good faith and without prejudice or guarantee. Anyone wishing to rely on such opinion should f irst satisfy themselves as to its accuracy and feasibility. Newark shall not be liable for any loss (including indirect and consequential loss), damage, delay, and loss of market, costs, expenses of whatsoever nature or kind and however sustained or occasioned. Notwithstanding the aforementioned, notice of a claim or suit must be made to Newark in writing within 90 days of the date the services were first performed or the date the damages were first discovered, whichever is the later, failing which lack of notice shall constitute an absolute bar to the claim or suit against Newark. ‘This survey is a factual report on the inspection carried out, and the opinions expressed are given in good faith as to the condition of the vessel as seen at the time of the survey. It implies no guarantee, no safeguard against latent defects, subsequent defects, or defects not discovered at the time of the survey in woodwork or areas of the vessel which are covered, unexposed, or not accessible to the surveyor internally due to the installation of non removable linings, panels and internal structures, etc. This is a visual survey only, being non-invasive and non-destructive. Newark accepts no responsibility or liability in relation to any part of the vessel which cannot be accessed or viewed. Parts of the vessel were not accessed or viewed and therefore we cannot comment on this in relation to any patent or latent damage, including termite or other insect infestation. ‘This report carries no warranty regarding ownership of the vessel or any warranty regarding outstanding mortgage, charge or other debt there may be on the vessel. This survey is personal and confidential to our client and has no extended warranty if disposed of to a third party for any purpose without the permission of Newark. ‘This report does not address stability, vessel performance or overall design, and no warranty is conveyed under these headings. ‘Machinery was not opened up for inspection or compression tests carried out. No chemical tests were carried out on fuel or water. Rigging at deck level only has been commented on. An expert should be appointed if a full rigging survey is required. Whilst we did not sight any pest infestation during the inspection, we recommend that a pest control expert be appointed to assess whether termites or cockroaches are present. ‘Liability is limited to five times the surveyor’s fees for the inspection of this vessel. 20 The basis of reports ‘These standard trading terms, all agreements and disputes relating thereto, shall be governed by and interpreted in accordance with law. Please note that copyright remains with Newark. No part of our report may be disseminated until such time as our invoice is paid in full.©’ T he above disclaimer can be fitted onto one page if Times 12 point font is used. There is also enough space below it for the surveyor(s) to add his (their) signature(s). Note that there is reference to copyright of the report in the above disclaimer. If your standard terms and conditions state that the report will not be issued until payment has been received then this phrase is redundant. You will note that there is a reference to areas which were unable to be accessed. It is also advisable, where appropriate, to state in your report if, and why, you were unable to access a particular area or piece of equipment. Some other typical clauses which surveyors may use include: • Asia is noted for its termite problems aboard vessels. As a result, great care is taken during the survey to determine whether the vessel has an infestation. Since these creatures reside inside wooden components aboard, it is, in many cases, impossible to detect their presence without becoming invasive. It is strongly recommended that the vessel be treated for termites as a precaution. • No evaluation of the internal condition of the engines and gears and the propulsion system’s operating capacity has been checked. It is recommended that the internal condition of engines be determined by a qualified engineer. • All systems and components inspected and described herein are considered serviceable and/or functional except where indicated in the body of the report. Electronic and electrical devices and instruments were checked for power up only. Components not mentioned in this report were not inspected. • Blisters are an unknown factor on all boats and, if not currently present, there is no guarantee that they will not appear in the future. Blisters have a tendency to dry out over winter storage unless severe or large. Blisters (if any) best appear after a vessel has been in water for an entire season. In addition, the symptomatic evidence of blistering can be obscured by bottom coatings, a dry storage period during which blisters spontaneously depressurise, bottom laminate sanding, and other conditions or actions. Recommend full inspection for blisters immediately after haulout and power wash. Surveyor has no first hand knowledge of the history of bottom maintenance, blistering, repairs or prophylactic coatings on this vessel. 21 REPORT WRITING FOR MARINE SURVEYORS • It is in the nature of marine vessels for deterioration, wear and accidents to occur and, as such, this report represents the condition of the vessel only at the time of this survey. • This vessel was surveyed without removal of any parts, including fittings, screwed or nailed boards, anchors and chain, fixed partitions, instruments, clothing, spare parts and miscellaneous materials in the bilges and lockers, or other fixed or semi-fixed items, locked compartments or otherwise inaccessible areas. Further, no determination of stability characteristics or inherent structural integrity has been made and no opinion is expressed with respect thereto. This survey report represents the condition of the vessel on the above date, and is the unbiased opinion of the undersigned, but it is not to be considered an inventory or a warranty, either specified or implied. • Some parts of the survey were limited by not being invasive. T he term ‘satisfactory where sighted’ is often used by surveyors. When used, the surveyor should state which specific areas were not sighted to reduce the possibility of confusion and later claims. 2.7 Professional indemnity insurance T here are a number of insurance companies and underwriters who provide professional indemnity (PI) insurance. This can be expensive for smaller companies, although some of the professional surveyors’ organisations also carry PI insurance so that you get the benefits of membership and insurance against frivolous claims. All of the PI insurance providers advise that you do not inform your clients that you have this type of insurance cover as it is akin to painting a bullseye on your back. They also advise that any conflict with a client should be settled as quickly and amicably as possible to avoid expensive, time-consuming claims and in the interests of good client relations. 2.8 Limiting liability Marine surveyors have other options open to them to limit liability. One way is to set up your company as a limited liability company. The nomenclature for such companies varies around the world but the operating and legal principles adopted in establishing this type of company are generally very similar. A limited company is a corporation with shareholders whose liability is limited by shares (Ltd), which is the most common form of privately held company. Setting up as a limited company is an attractive option for many people as, unlike sole traders, personal assets are completely separate from company finances. Some countries insist on there being two or more shareholders whereas others allow single shareholders. 22 The basis of reports If your company is a limited liability company, it should be shown on all company documents, including your reports, e.g. Company Name Ltd, Company Name LLC, etc. Examples are given in the appendices. 2.9 Copyright issues Copyright is a form of intellectual property that gives the author of an original work exclusive rights for a certain time period in relation to that work, including its publication, distribution and adaptation, after which time the work is said to enter the public domain. Copyright applies to any expressible form of an idea or information that is substantive and discrete and fixed in a medium. Some jurisdictions also recognise the ‘moral rights’ of the creator of a work, such as the right to be credited for the work. Copyright is described under the umbrella term ‘intellectual property’ along with patents and trademarks. If somebody uses your work for profit without your permission they can be sued for damages. If they use your work with your approval they will also need your permission to make any changes. By writing technical articles you show whether or not you know your subject. If you are writing articles for general publication it is often advisable to include a proviso when you send your work in to the editor. Very often he will take your piece and change it to suit his purposes. In some cases, it will make your article unrecognisable from the original. You should also insist that he acknowledges your work by adding your name. If you wish to use your writing to advertise your company then you should add your company name at the bottom of the article when submitting it and insist that it is included. If he refuses to do so, you have the choice to withdraw the article from publication. If you work for somebody else, you will often need to get his permission to have an article published or you will need to add a disclaimer such as: ‘The views expressed in this article are those of the author and not necessarily those of Newark Marine Consultants Ltd.’ Layout and format are not subject to copyright laws, only the report content. Consequently, any of the layouts you see in this document may be used by the reader without the need for the author’s permission. You will note in the last section on ‘Caveats and disclaimers’ the sentence: These standard trading terms, all agreements and disputes relating thereto, shall be governed by and interpreted in accordance with law. Please note that copyright remains with Newark. No part of our report may be disseminated until such time as our invoice is paid in full.©’ Note the © copyright mark. Whilst copyright is implied, if you wish to advertise the copyright for a specific purpose it is advisable to use the appropriate mark. In the 23 REPORT WRITING FOR MARINE SURVEYORS above case it is used as a tool to get the client to pay the invoice. He will be unable to use the contents of the report until he has done so. On payment of the invoice the copyright is transferred to the client. As this book is published in the United Kingdom, the author’s statements are subject to United Kingdom copyright law. 24 Preparing for the report Chapter 3 - Preparing for the report Surveyors are often reminded to keep an open mind when tackling a new assignment and to avoid preconceived ideas. This is because every survey is different. No two surveys are ever the same, even when it is a repeated condition survey of the same vessel. The same applies to reports, no two are ever the same. Consequently, each one must be tackled in its own way. However, there is one important point about all reports: if you start with a certain style and layout you must stick with it throughout the report, i.e. you must be consistent. T his does not mean that you cannot start to put the report outline together before leaving your office. As you do so, you will start to see areas which will need investigation and questions that will need to be asked. By having the outline report set up you will be able to concentrate on inputting the relevant information from the investigation much quicker. Many surveyors find it useful to write down reminders in their notebooks. These often come from drafting the report before carrying out the inspection. 3.1 Interviewing skills One of the prime requirements for a surveyor is to be able to communicate well with people from different ranks and nationalities when gathering information. To be able to get the maximum from your contact with other people you will need to establish a rapport, i.e. put them at ease so that they will be responsive to your questions. For those who survey vessels with international crews it is often helpful to learn how to say ‘hello’, ‘goodbye’, ‘excuse me’, ‘please’ and ‘thank you’ in the languages of the major seafaring nations. Making the effort to learn only one word is often the key to getting foreign crews to co-operate. Interviewing skills are normally only necessary when carrying out investigations where evidential information must be obtained from witnesses to an incident or accident. They are also essential when carrying out International Safety Management (ISM) and International Ship and Port Facility Security (ISPS) Code audits. T here are many techniques used in interviewing. Scientists and psychologists have theorised for many years on efficient and effective methods, e.g. cognitive interviewing techniques. The reader may wish to explore the different techniques in his own time. Below are some simple rules to follow. It is important to note that you will find it very difficult to get information out of an interviewee if you are confrontational. You should always start with a spirit of co operation, and this is where establishing a rapport is essential. 25 REPORT WRITING FOR MARINE SURVEYORS Body language and seating arrangements can also give the interviewee the wrong impression. Sitting with your arms folded on the opposite side of a table signals to the subject that you are going to be confrontational or defensive. By sitting alongside the subject you are telling him that you are there as a friend and prepared to listen. Psychologists suggest that using the same body language as your subject will also help him to relax. Use the technique at key moments during questioning as this is when it will have maximum effect. Always start with the easier and less contentious questions and build up to the more difficult ones later. It is often advisable to have a break after a particularly difficult set of questions so that the subject is not intimidated or stressed. Always be polite and respectful to the interviewee. Remember that you are seeking facts and not opinions from the interviewee. However, it is often acceptable to allow him to offer opinions to build the necessary rapport. He may also give you some indication of where you should be looking. Lawyers will often welcome a word for word statement to get a feel for the interview and the witness’s involvement. You should learn how to ask efficient questions. The way that questions are phrased is important. You can save a lot of time and energy by asking questions correctly. Try to avoid questions which can have a ‘yes’ or ‘no’ answer, e.g. Did you…? Have you…? Were you…? These will be long questions for a single word answer and, therefore, time consuming. Use the prefixes ‘who’, ‘what’, ‘when’, ‘why’, ‘how’ and ‘where’ as these will always evoke narrative type answers and the information for which you are looking. Listening is an essential part of interviewing. What are you there for? You are there to learn from the interviewee and the only way of doing that is to listen to his answers. As long as you are talking you are learning nothing. Interrupting other people is also disrespectful. You should not interrupt the interviewee when he is in full flow as this may distract him and move him off the subject. If his answers are raising more questions, write them down on a note pad so that you can come back to them at the end of his current answer. One of the problems of interviewing is maintaining eye contact whilst listening to answers and writing them down. Dictaphones are often used to record statements which are later transcribed by audio typists. However, the permission of the interviewee is required. Shorthand is an advantage but is a dying technique with the advent of computers and word processors. Experienced interviewers have their own methods for writing down information in a shortened form. If you touch type, you can be listening, maintaining eye contact and recording the answer on your computer. T his is where both accuracy and speed are essential. You will need to be able to type at 80-100 words per minute to be able to do this. 26 Preparing for the report However, in more contentious cases, a lawyer will generally be used to interview witnesses. Where this is not possible, the surveyor may be asked to carry out the interviews. In these situations there may be members of the crew who do not wish to incriminate themselves or have something to hide. Whilst a lawyer with sound maritime knowledge can be good at getting the necessary information, an experienced surveyor with good interviewing skills can be just as effective, if not better. Often, witnesses can be intimidated by a lawyer but not by a surveyor who speaks the same shipboard language. 3.2 Facts and opinions Some believe that a surveyor should only be concerned with gathering facts, supporting them with photographs and documentary evidence. They also suggest that opinions should only be offered by consultants and that the two are distinctly separate. However, there are occasions when the dividing line between the two can become blurred, particularly in the case of cargo surveys using the Lloyd’s Schedule ‘C’ report format which clearly calls for the surveyor’s opinion as to the cause of damage. Underwriters’ surveyors are not specifically required to give an opinion in their reports. They are asked only to agree or disagree with the owner’s allegation as to the cause of damage. When instructed by underwriters, a surveyor must not express an opinion on liability under a policy unless he is requested to do so. If a surveyor is unsure as to whether to offer an opinion, he should clarify his instructions with the client. 3.3 Aide mémoires and laptops T here is no shame in carrying a clipboard or notebook which contains a checklist. Even the most experienced surveyors will forget one or two items of information and will have reminders in their notebooks, especially as they get older! Many clients have a standard report format which can be completed on a laptop during the survey. This is also a form of aide mémoire which ensures that the surveyor inspects those areas listed by the client. However, some surveyors will often print out the client’s form and complete it in ink so that it can be typed out later. Other clients may have a report format which can only be completed on a laptop or computer, e.g. RightShip, International Group of P&I Clubs. RightShip uses a Microsoft Word template where some of the cells have a choice of answers, e.g. ‘good’, ‘fair’, ‘poor’, etc. Other cells may only be completed in a certain format, e.g. dates. Some P&I Clubs use Adobe Acrobat software for the completion of their forms, again with choices of answers, e.g. ‘yes’, ‘no’, ‘not applicable’ and ‘not inspected’. For any item marked ‘no’ the surveyor is required to explain why the item is unsatisfactory. 27 REPORT WRITING FOR MARINE SURVEYORS Whatever the format of the aide mémoire, the client is relying upon the surveyor’s ability and experience to assess an item and describe any deficiency in that item. If you have inexperienced surveyors in your company it can help if relevant questions are included in the form but these should promote accurate descriptions which we will deal with later. Some pleasure craft insurers also have set formats for their reports but many do not, relying on the survey company to compile an appropriate report. The advantage of having this on a laptop is that the report can be started or, in some cases, completed, when travelling back to the office from the survey. 3.4 File management T he surveyor may need to store a lot of information with respect to various jobs. Whether on paper or on computer, files must be organised and in order so that the information can be easily found and readily accessed when compiling your report. To this end, survey companies establish logical numbering systems for their job f iles. These reference numbers should allow staff to readily identify a job from its reference number. For example, ALT235/AJ/02 would be the reference number for Alton Marine Consultants Ltd, Job No 235, carried out by Alan Jones, and the 02 possibly representing the second item of correspondence transmitted or received. An R or T after the 02 could indicate received or transmitted. Some companies start new job numbers from the beginning of each calendar or financial year so that a job number may be XMC235/11/AJ/02, the 11 representing the year. Some companies deliberately make their job numbers unrecognisable to anybody else, e.g. ‘AJ’ could be replaced by a company employee number. Whatever the system used, it should allow for the logical storage of documents relating to a job, i.e. in chronological order. If the last number of the above number refers to a file in chronological order it will be relatively simple to file and to find. If you are to have a good and efficient system in place you should keep a correspondence record such as the job correspondence sheet on the following page. T his correspondence sheet layout, which can be stored in the job file, includes references to incoming and outgoing correspondence, their dates, to and from whom and with details of the correspondence and where it is stored. It lends itself to storage in both the soft and hard job files. Whilst this might appear laborious, it is particularly useful with long and involved cases when your client may ask why a job took so much time. You can show that you have acted diligently, responding to correspondence immediately whilst waiting weeks for responses. 28 29 Preparing for the report Job Correspondence Sheet File No: ALT133 Name of Job: Ref No IN OUT DATE From/To Details Location ALT 1 X 3-Apr-2010 Client Acknowledgement of appt HD ALT 2 X 2-May-2010 Surveyor Update, request for info. HD ALT 3 X 2-May-2010 Client Copy HD ALT 4 X 3-May-2010 Surveyor Request for interview HD ALT 5 X 3-May-2010 Client Copy HD ALT 6 X 16-May-2010 Surveyor Request for information HD Copies to Client & Surveyor ALT 7 X 29-May-2010 Surveyor Request for information HD Copies to Client & Surveyor ALT 8 X 29-May-2010 Surveyor Request of assistance HD ALT 9 X 15-Jun-2010 Client Copy of fax to CS Cheung File ALT 10 X 2-Aug-2010 Surveyor Update HD ALT 11 X 15-Sep-2010 Client Faxed further instructions File ALT 12 X 5-Oct-2010 Client Faxed req for prelim report & invoice File ALT 13 X 6-Oct-2010 Client Delivered preliminary report & invoice HD ALT 13 X 26-Oct-2010 Client Request for final report File ALT X 26-Oct-2010 Client Final report HD & File 3.5 Good written and spoken communication Miscommunication and ambiguity are the worst enemies of understanding. In terms of a surveyor carrying out a survey and issuing a report it can happen in both directions, i.e. between him and the ship’s crew and between him and his client. Miscommunication is more prevalent when two people speak completely different languages. Ambiguity is common where the speaker does not think about what he is going to say before doing so. It is also common where reports are not accurate and understandable. When asking a stranger questions, it is essential that you are clear, concise and precise, speaking more slowly than normal to reduce the possibility of misunderstandings, particularly if his first language is not the same as yours. Good verbal and written communication are also essential when delegating (see later). It may be necessary to reinforce your question by getting feedback from the interviewee as to whether he has understood the question. However, the subject will often respond with a ‘yes’ even when he has not. It is thus advisable to ask him to repeat your question back to you. A classic example of this is in good restaurants where the waiter will often repeat your order to ensure that he has understood you so that in turn he can pass the written order to the chef. REPORT WRITING FOR MARINE SURVEYORS Where there is a language barrier with communication problems it may be advisable to write down your questions and explanations. Some people can understand written English better than spoken English, particularly when the interviewer speaks with an accent or dialect. It is also often helpful to use sketches and diagrams to help explain the subject in hand – a picture being worth a thousand words. Your notebook is not just for recording evidence! 3.6 Tone of the report T here is a saying that ‘he who pays the piper calls the tune’. Basically, this means that you should report what your client wants you to report and in the way he wants it reported. Whilst the client will issue instructions providing some form of direction as to the nature of the survey or investigation, the surveyor must not be muzzled from reporting his findings in an honest and objective manner. It is very easy to be either over complimentary or too negative in a report. Reports can be easily coloured by favourable or unfavourable descriptions and the selection of photographs presented. Complimentary photos can be included with negative ones omitted, and vice versa. Surveyors who have done so have been criticised in court by judges and their evidence excluded. A surveyor must give a fair and balanced view. A surveyor should report his findings honestly and without bias. When writing a report, the surveyor must continually ask: ‘Is this the truth?’ The truth is always more beneficial to all concerned as everybody is then aware of the true situation. This may not appear so to some of the parties involved, and your report findings will not be popular with those for whom additional cost is incurred. This is one of the downsides to being a marine surveyor. You are the person in the middle and you can never please all of the parties all of the time. If you are in doubt about the purpose of your assignment and what you are to report take another look at your instructions. This is why it is essential that you are clear about your role before you take on the job. 3.7 Terminology versus jargon Every profession has its own terminology specific to its operations. Shipping terminology or nomenclature has evolved over thousands of years with many of the terms having existed from the times when ‘ships were made of wood and men were made of steel’. For example, port and starboard are shipboard terms for left and right, respectively, and confusing these two could cause a shipwreck. In Old England, the starboard was the steering paddle or rudder, and ships were always steered from the right side at the back of the vessel. Larboard referred to the left side (the side on which the ship was loaded). Shouted over the noise of the wind and the waves, larboard and starboard sounded too much alike and so larboard eventually became port. The word 30 Preparing for the report ‘port’ means the opening in the ‘left’ side of the ship from which cargo was unloaded. Sailors eventually started using the term to refer to that side of the ship. Use of the term ‘port’ was thus officially adopted. Jargon is defined as the language used by people who work in a particular area or who have a common interest: lawyers, computer programmers, accountants, etc. All have specialised terms and expressions that they use, many of which may not be comprehensible to the outsider. They may also use familiar words with different meanings as well as abbreviations and acronyms, etc. Terminology is defined as the vocabulary of technical terms used in a particular field, subject, science, or art. Nomenclature is defined as a system of words used to name things in a particular discipline. Jargon may also be considered as unnecessary words which may not be comprehensible to the outsider, whereas terminology and nomenclature are necessary and unavoidable words. For example, ‘port’ and ‘starboard’ have specific meanings which cannot be replaced by any other words. Imagine if we had to say ‘on the left when looking towards the front of the ship/boat’ every time we needed to refer to the port side of a vessel. Clearly this is unmanageable so a specific technical term is used. As previously stated, you should always remember for whom you are writing your report. It is often difficult to know the technical knowledge of your client so it is advisable to write your report as if for somebody who has no shipping or technical knowledge. Whilst your client may have such knowledge, you do not know who else will be reading the report. Those who have the appropriate shipping knowledge can then discount any unnecessary information. Some surveyors believe that they should write their reports in a legal form of language, sometimes known as ‘legalese’, i.e. the specialised language of the legal fraternity. Reports should be compiled in plain, simple and understandable English. Leave the legalese to the lawyers even if you are writing a report for a client which is to be sent to a lawyer. Remember, others, who are not lawyers, may need to read your report. Try to avoid ‘trendy’ phrases such as: At this moment in time… At this time… Which really mean ‘now’ or ‘today’. As you will see from the section on active and passive writing (5.5), the above examples fall into the passive writing mode. Try to avoid redundant words in sentences, e.g. Outside of Inside of 31 REPORT WRITING FOR MARINE SURVEYORS and the use of ‘off of’. Remember that spelling checkers will not highlight your mistake in using ‘of’ when you really meant ‘off’, and vice versa. It is always advisable to have a dictionary and thesaurus on your bookshelves for reference when you are not sure about a spelling or the meaning of a word. Many can also be found online. 3.8 Multiple surveyors Marine surveyors in the past traditionally came from the seagoing ranks having served as chief engineers or masters. With a lack of cadet training in the 1980s and 1990s, there is now a shortage of these ranks so surveyors are coming from other sources. Many new surveyors are taken on by larger companies to undergo a form of apprenticeship, eventually leaving to start their own companies. Others will have taken the giant leap to start up on their own immediately upon leaving the sea. If you are a good surveyor, there will come a time when you will have so much work that it becomes more cost effective to take on staff to carry out some of your work. T his means that you will need to delegate work to them. 3.9 Delegating Delegating is a very important activity and process. The aim is to ensure that the person to whom you are delegating a task can do the job. The employee can only do this when provided with all relevant information which must be fully understood. T his means that clear and concise instructions must be given verbally and also, preferably, in writing. It may help to sit down in a quiet area to discuss the client’s instructions in a face to face meeting with no distractions. Eye to eye contact is important. Such meetings should cover all aspects of the job, including any special requirements, e.g. equipment, specific client requests. The proof of whether you are good at delegating will be the results of the assignment, although this could also be down to you having a good surveyor who uses his initiative! It is also advisable to have the surveyor repeat your instructions to you so that you can correct any misconceptions or misunderstandings. Even better if the instructions can be confirmed in writing. Fortunately, mobile telephones can enable your surveyors to call for clarification. The higher your phone bills, the less successful you are at delegating. 3.10 Signing the report Most large survey companies prefer to sign their reports with the company name so that the surveyor cannot be identified. This may be in the false belief that by doing 32 Preparing for the report so they can protect their surveyor. However, most clients prefer to know who carried out the survey. A surveyor should always be ready to take responsibility for his product and be prepared to sign his name at the bottom of the report. By adding ‘on behalf of Newark Marine Consultants Ltd’, the company becomes responsible for the consequences and not the individual surveyor. An example of the final sentence is: ‘It is to be clearly understood that the condition/state of items hereafter reported upon are strictly the opinion of the undersigned and that opinion reflects the condition/state found on this date . Captain William Bligh Attending Surveyor For and on behalf of Newark Marine Consultants Ltd’ 3.10.1. Legal guideline If the company is the party engaged to undertake the survey rather than the individual, then the above would be the correct way to sign the report. However, the issue is to make sure that the company is engaged by the client correctly at the beginning. This would need to be made clear up front in the company’s standard terms and conditions or whatever is used to instruct the survey company to undertake the survey in the f irst place. It should be noted that the protection of the company may not be forthcoming in the event of the surveyor being negligent or acting maliciously. 3.10.2. Lawyer’s comments If you have academic or vocational qualifications, or are a member of a professional institute or society, you should add the appropriate letters after your name. This will show that you are a professional and add weight to your report. Many years ago, wax seals were used to formalise documents and some survey companies also used them. Whilst adding a seal is time consuming, it adds a certain amount of flair and authenticity to the document. In some countries, such as China, a seal is still used today, locally referred to as a ‘chop’. The seal is comprised of solid wax, usually red in colour. Using a flame, the wax is melted onto the appropriate place on the paper and, whilst still hot, the wood or stone seal is pressed down into the wax to leave an imprint. Several professional institutes also use a similar system to endorse membership certificates. This consists of a red circular sticker placed in the appropriate place on the paper. A hand press which has the seal fitted is then positioned over the red sticker and squeezed shut to leave an embossed imprint. Some organisations also have their own rubber stamps or chops, such as the International Institute of Marine Surveying (IIMS) and the National Association of 33 REPORT WRITING FOR MARINE SURVEYORS Marine Surveyors (NAMSGlobal). As a member of the IIMS you are entitled to use its logo in your report. You should use it adjacent to your signature and not next to the company heading, unless your company is an associate member. The NAMS issues a specific and individual rubber stamp to each member having the member’s name and individual membership number. This is generally used next to the surveyor’s signature at the end of the report. 3.11 References With some types of report, such as cargo and opinions, it may be necessary to include and refer to information from other sources. You may be referring to technical information from an equipment handbook or data sheet on a particular cargo. The source of such information should be stated in the report in the form of references. T hey are usually given some form of numbering or letter identification system (as shown after this sentence). 1 If you are using a computer to write a report, your word processor will do this automatically for you as and when directed. References may be at the bottom of the page or at the end of the document. If there are only a few references, they tend to be at the bottom of the relevant page. If there are many references, they tend to be left to the end of the document as they may take up too much space at the bottom of individual pages. 2 T hey may also interfere with report footers. If your company uses a footer on every page, references should be left to the end of the document. If you prefer not to use the software facilities and write references yourself, you should follow a standard format, e.g. British Standards Institution (2001) Recommendations for Bulk Cargo Stowage (BS XXXX). London: BSI. (The above is a fictitious reference.) Note that the second line of the reference is indented. 1 This is to show you how a reference is included in the text. 2 You will also find this reference at the bottom of the page. 34 Report types Chapter 4 - Report types 4.1 Specific requests From time to time, clients will request a survey with specific requests for items to be inspected or operational aspects to be checked. In this event, the surveyor’s report will need to include a specific section relating to the information requested, e.g. We were appointed to carry out: • An off hire condition survey. • A bunker survey. • A damage survey of hatch covers. • An investigation of the cause, nature and extent of water damage to the vessel’s cargo. T he report itself should then be broken down into sections covering each of the above specific requests (see in the appendices). It is common for the photographic appendix relating to each of the specific requests to be attached after each of the relevant sections. 4.2 Pro forma reports Some surveys, such as container damage surveys, motor vehicle surveys, heavy lift and lay-up warranty surveys, do not command significant fees. Consequently, the time spent doing such a survey should be as short as possible. Pro formas help in reducing time spent on site, and container surveys particularly lend themselves to this methodology (see 4.9 – Container damage surveys). 4.3 Pre-purchase condition surveys (PPCS) A pre-purchase condition survey is basically an information gathering exercise on behalf of a prospective buyer of the vessel. The aim is to obtain full information on the vessel’s machinery and equipment and, where possible, to test the equipment. Whether for merchant vessels or pleasure craft, PPCS survey report formats can be standardised but can also be modified where required. Many brokers and other companies who deal mainly in PPCS have their own report formats which require the surveyor to gather certain information. These tend to be comprehensive so that little is left to chance. All that remains is for the surveyor to give his own assessment of the vessel in the key areas. 35 REPORT WRITING FOR MARINE SURVEYORS It is to be remembered that this is a condition survey and, as such, the surveyor should report on the condition of the vessel and its equipment, e.g. ‘operational’, ‘good’, ‘satisfactory’, ‘fair’, ‘unsatisfactory’, ‘poor’. The meanings of these terms should be defined near the front of the report so that the client will be given a clear idea of the condition of the relevant equipment. T he vessel’s buyer will also need information on the make, type and model of much of her equipment, particularly navigation equipment, deck equipment and engine room machinery. Just as there are many surveyors there are many different PPCS report formats. The two report formats given for merchant vessels and pleasure craft give examples of the information required by clients and different formats. Sample reports can be found in Appendix I. It will be noted that in the first example much of the information must be entered into tables. The report is made up of two column spreadsheets which have been pasted into the word processor document. The reason for this is that it is far easier to ‘tab’ between cells, or boxes, than to use the mouse or touch pad to relocate the cursor for the next text input. The tabular format also allows the company to enter aide mémoires in the form of questions into the information cells so as to remind less experienced surveyors what they should be looking for. This format is also far easier for the client to follow. However, it does not allow for the placing of photographs in the text. Whilst the given report format gives extensive coverage of the vessel’s condition, it is not exhaustive. Additional information and tables can be added where required for specialised and unusual areas. Some clients request extensive information on the vessel’s equipment and other specific additional information. Additional sections can be added for such purposes. It may not be possible to access all the information listed in the form as some owners will deny the PPCS surveyor access to some areas of the vessel. They may also refuse to allow the testing of equipment. If this is the case, it should be reported in the relevant cell and in the general remarks at the end of the form. T he reader will note the disclaimer section which is included in both types of PPCS report. The disclaimer used for pleasure craft is more comprehensive as there tend to be more cases of claims against surveyors in this field. As previously mentioned, once terminology has been defined and clarified, words such as ‘good’, ‘fair’, ‘satisfactory’, ‘poor’ and ‘unsatisfactory’ may be used to report the condition of the vessel and her equipment. It should be reported if it has not been possible to access an area for inspection, together with the reason. The phrase ‘satisfactory where sighted’ may be used but areas not specifically sighted should also be mentioned. ‘Not sighted’ can be used but should be accompanied with the reason 36 Report types why it has not been sighted, e.g. ‘not sighted as not yet issued’, or ‘reported to be unavailable by owner’, etc. Defects found during the survey should be listed. Some P&I Clubs ask for recommendations to accompany the defects whilst others do not as they believe that the owner should know what remedial action is required. Some pleasure craft surveyors include ‘defects found’ in the body text of the report together with recommendations. Some prefer to list all defects together at the end of the report and not to make recommendations unless asked to do so by the client. T he same principles apply to defects as to the rest of the report. The nature and location of the defects should be unambiguous, accurate and concise. A good practice is to add the defect photographs in the body text adjacent to the listed defect. However, the tabular report layout does not lend itself to this practice. 4.3.1. Pleasure craft surveys In the case of a pleasure craft PPCS, the buyer may ask for a valuation for the purposes of obtaining finance for the purchase. Giving a valuation on something is like estimating the length of a piece of string. The value of a boat is dependent on many factors, not least what somebody is willing to pay for it. Estimating the value of a boat is not in the realm of this text. However, the survey report should include some form of proviso relating to market conditions, e.g. ‘We believe that, in the current open market conditions between willing buyer and seller, the vessel’s value is approximately subject to the defects below being rectified.’ Note the last part of the sentence: ‘subject to the defects below being rectified.’ The surveyor is saying that this is the value of the boat in a good condition. If the last part of the sentence is omitted, he would be giving a valuation based on the value of the boat in good condition less the cost of repairs. Which of the two forms of proviso is used will depend on the relationship between the seller and buyer. If the sale and purchase agreement (S&P) stipulates ‘as is, where is’ then the valuation will be the value in good condition less the cost of rectifying the defects. Pleasure craft surveyors should be aware that the S&P agreement will often include a clause that the deposit will only be refunded to the buyer in the event of the surveyor f inding defects of a structural nature. Such defects should be clearly and accurately stated to prevent any confusion. Osmosis is a frequent problem on glass-reinforced plastic (GRP) boats and the subject is not within the remit of this book. Clients are often unfamiliar with the phenomenon. Some suggested clauses relating to the problem are: • Higher moisture content readings are generally to be expected immediately after the vessel has been taken out of the water. 37 REPORT WRITING FOR MARINE SURVEYORS • It is also recommended that GRP hulls be allowed to dry out for a minimum of seven days before readings will give a realistic indication of the true moisture content of the hull laminate. • The moisture content meter is used only as a barometer of moisture content, i.e. indicating trends, not an absolute reading. • It should be borne in mind that GRP boats in South East Asia tend to remain in the water almost all year, as opposed to those in cooler climates where such vessels are generally removed from the water during winter months. • Blisters are an unknown factor on all boats and, if not currently present, there is no guarantee that they will not appear in the future. Blisters have a tendency to dry out over winter storage unless severe or large. Blisters (if any) best appear after a vessel has been in water for an entire season. In addition, the symptomatic evidence of blistering can be obscured by bottom coatings, a dry storage period during which blisters spontaneously depressurise, bottom laminate sanding, and other conditions or actions. We recommend a full inspection for blisters immediately after haulout and a power wash. • Our surveyor has no firsthand knowledge of the history of bottom maintenance, blistering, repairs or prophylactic coatings for this vessel. T he above clauses should cover the surveyor in the event that osmosis is found at a later date. Pleasure craft damage surveys tend to take a similar form to merchant vessel hull damage surveys (see 4.6) in that they are narrative in nature. They will include the usual ‘found and recommended’ sections detailing the damage and remedial work required. 4.4 P&I Club surveys Marine insurance is in the nature of two forms: hull and machinery (H&M) and protection and indemnity insurance (P&I). H&M surveys are usually carried out by a classification society on behalf of the owner. P&I insurance is a little more complex. P&I Clubs were formed by several owners coming together to mutually insure each other’s vessels for those risks not covered by H&M insurance, e.g. cargo damage, crew injury and pollution. Each owner annually contributes a monetary amount relating to the gross tonnage owned, known as the ‘call’. The fund is supervised by a management company, e.g. Thomas Miller is the manager for the UK P&I Club, Charles Taylor for the Standard P&I Club. Some P&I Clubs also offer H&M cover to their members, e.g. the Swedish Club. Just as the better classification societies have formed themselves into an industry association called The International Association of Classification Societies (IACS), so the better P&I Clubs have formed themselves 38 Report types into the International Group (IG) and they provide mutual risk assurance to each other in the event of a very large claim, such as pollution. Whilst some clubs use their own inspectors to carry out visits to the club’s vessels, independent surveyors are usually appointed to carry out full entry, periodic, follow up and damage surveys on their behalf to identify the club, and underwriter’s, risk exposure. This puts the surveyor in a difficult position as he is appointed by the managers to carry out a survey on a member’s vessel, i.e. he is ‘piggy in the middle’ and, as such, should have a good ‘bedside manner’, be approachable and professional. Such condition surveys are wide ranging and comprehensive in nature, covering the vessel’s structure and operations. This means that the surveyor must have a good all-round knowledge of ships. Unfortunately, due to the very vertical management and training structure on board ships, seafarers are restricted to being navigating or engineer officers, radio officers generally having been phased out of ship operations. T his means that H&M surveyors are generally either ex-navigating or engineer officers, usually the latter. Whilst there is some familiarisation with marine engineering in the Class 1 deck officer’s course, there is no navigational familiarisation in an engineer’s course. This means that neither is an expert in both areas. In larger survey companies, each will pass information and advice to the other so that both become capable of carrying out comprehensive P&I condition surveys. Each of the P&I Clubs has its own report format. GARD, the North of England, SKULD, the American Club, the London Club and the Swedish Club all use the same form which is based on Adobe Acrobat 7.0 software and later versions. The fields to be completed by the surveyor are preset. The form is broken down into sections covering the various areas of the vessel. These are in turn broken down further with the surveyor answering a question by checking a box for ‘yes’, ‘no’, ‘not applicable’ and ‘not inspected’. For the latter three answers, the surveyor must enter reasons for his selection under the remarks area. T here is space for additional descriptive input under each section, the conditions for the survey and the overall summary of the vessel’s condition. Other P&I Clubs have their own formats which are usually in Microsoft Word. Many of these are generally in tabular form to facilitate easier completion. T he surveyor is required to list defects found during the inspection. The surveyor should not make recommendations as to how defects should be rectified unless the client requires this information. 4.4.1. Hatch cover surveys Hatch covers are generally required to be ‘weathertight’ and not necessarily watertight. T he statutory requirement contained in Regulation 3(12) of the International Convention on Load Lines, 1966, states that: 39 REPORT WRITING FOR MARINE SURVEYORS ‘“Weathertight” in relation to any part of a ship other than a door in a bulkhead means that the part is such that water will not penetrate it and so enter the hull of the ship in the worst sea and weather conditions likely to be encountered by the ship in service.’ Hatch cover surveys are normally a part of P&I Club surveys. As experienced as a surveyor may be, there is always the possibility of missing an item or area when carrying out inspections. There is no shame in carrying a clipboard with a check list as an aide mémoire. A suggested check list which should suffice for most surveys (and which does not include weathertightness testing) is shown in Figure 1. This table is in the form of an Excel spreadsheet which may be printed out or stored on a laptop and used on site to record the information. During the P&I Club survey, the surveyor will be required to carry out weathertightness testing of all hatch covers. Most P&I Clubs prefer ultrasound testing as this has been found to be the most accurate form of hatch cover testing. However, a surveyor may be requested to carry out a specific and individual hatch cover survey. Such requests may happen when there have been previous problems with the subject hatch covers, i.e. they have been found to be leaking with possible consequential cargo damage. Each P&I Club has its own pro forma report form to be used when carrying out hatch cover test reporting. This may be used in association with the form shown in Figure 1. Trying to explain the findings with words alone can become cumbersome and open to misinterpretation. It is therefore advisable to use a simple diagram to show results. Further information on hatch cover testing can be found in Hatch Covers – Operation, Testing and Maintenance by Mike Wall. ISBN 13: 978 1 85609 344 6. Published by Witherby Seamanship International, 4 Dunlop Square, Deans Estate, Livingston EH54 8SB, United Kingdom. www.witherbyseamanship.com. 40 41 Report types HATCHCOVER INSPECTION CHECK LIST Ship: Port: Hatch No: Date: Item Condition 1 Hatch cover panels: Side plates Top plates Stiffeners Alignment 2 Coaming structure: Side and end plates Stays Coaming bar and drain channels Wheel trackways Bearing pads 3 Sealing arrangements: Seals Channels Cross joints Compression bars Non return valves Cleats 4 Opening / closing mechanism: Hydraulic jacks Hydraulic pipes Hydraulic rams Hydraulic windlass Chains Rollers Guide rails Track wheels Stoppers Wires Tensioners Gypsies Safety devices and interlocks Hinges, pins, stools 5 Additional remarks: (e.g. condition of hold, evidence of leakage, etc) Signed Signed Signed Master Superintendent Surveyor Figure 1. Suggested hatch cover inspection check list table REPORT WRITING FOR MARINE SURVEYORS Figure 2. A sample pro forma report form 42 Report types Figure 3. A sample completed report form 43 REPORT WRITING FOR MARINE SURVEYORS 4.5 Machinery damage surveys Machinery damage survey reports are usually of the narrative type, describing the surveyor’s findings. Being of a highly technical nature, they will necessarily have lots of technical terminology with descriptions possibly being long and detailed. Diagrams showing the terminology which will be used in the report will be of great assistance to readers, particularly those who are unfamiliar with the terminology. Being of the narrative type, the report should follow a logical sequence. A table of contents will help the surveyor to check if the layout can be easily followed. Tables and diagrams should be included in the table of contents. Readers will often go to the diagrams and photographs first to obtain an initial idea of the findings. Underwriters will need to know the full particulars of the vessel and that her certificates are up to date as any expired or invalid certificates could render the vessel as being unseaworthy. They will need to know the cause of the damage so that they can confirm that it was insured under the policy of insurance. They will also need to have an estimate of the cost of repairs as they will need to set aside funds to compensate the owner in the event that the claim is justified. Documents which have been obtained during the investigation, which are relevant to the claim and report, should be listed and appended. It should be stated whether the repairs required the vessel to be drydocked. Underwriters will also need to know if the owner’s work has been carried out during the repair and drydocking periods. In the event that the vessel was drydocked and the owner’s work carried out, the cost of the docking may be divided equally between the underwriters and the owner. Occasionally, the surveyor may be required to retain samples, specimens or damaged parts for possible later analysis. The retaining of such samples, etc. should also be reported. Surveyors should be aware that they may be asked to approve repair invoices at a later date. For this reason, the details of the damage and repairs should be accurate and detailed. 4.6 Hull damage surveys Hull damage surveys tend to be carried out on behalf of H&M underwriters. Several of the P&I Clubs also write H&M cover. Such organisations will often have their own report format which may be downloaded from their web page, e.g. the Swedish Club. 44 Report types T he report format generally takes the following layout: 1. 2. 3. 4. 5. 6. 7. 8. 9. Particulars. Parties attending. Narrative (background). Survey findings. Cause of damage. 5.1 Owner’s allegation. 5.2 Surveyor’s comments. Class status. Damage repairs. 7.1 Tender procedures. 7.2 7.3 7.4 Average repairs. Temporary repairs/voyage repairs/deferred repairs. Owner’s work. Conclusions. Enclosures. T here may also be a requirement for certain other pertinent information: • Vessel arrived/from. • Sailed/to. • Average repairs commenced/completed. • Owner’s work commenced/completed. • Vessel drydocked/undocked. • Time for discharging/reloading while affecting average repairs. • The call at the yard was/was not solely caused by a casualty. • Overtime worked, the rate and reasons for same. Underwriters will also need to know if any owner’s work was carried out during the drydocking period. In the event that owner’s work has been carried out, the drydocking fees may be split evenly between owners and underwriters. They will also need to know if other vessels were in the drydock at the same time, as the cost of drydocking may have been further apportioned between the vessels. Whilst not a liability for underwriters, any cargo damage should also be reported. It is often advisable also to report if general average has been declared by the owner as this will also have a direct bearing on the underwriters’ liability and their need to make a financial provision. 45 REPORT WRITING FOR MARINE SURVEYORS 4.7 Charterers’ surveys T he organisations which hire ships to carry cargoes are known as charterers. There are a number of different types of charter available to charterers: • Time charters. • Voyage charters. • Bareboat charters. More information can be obtained from other sources on the differences between the types of charter, the main point being that charterers may require an on hire survey at the start and an off hire survey at the end of a charter. These are basically condition surveys before and after the charter, the aim being to find out if the vessel has been returned to the owner in the same condition as when it commenced the charter. The surveyor is advised to take plenty of photographs which can be used for comparison after the off hire survey. In the event of any dispute over the condition of the vessel, the owner of the vessel may also ask for a condition survey by an independent surveyor. As charterers are generally required to pay for the vessel’s fuel for main engines and generators, a bunker survey will need to be carried out at the start and end of the charter. Any damage to the vessel will also need to be recorded in the same manner as other damage surveys with a section on ‘found and recommended’. A specimen report is given in the appendices. 4.7.1. RightShip inspections RightShip is a ship vetting specialist, promoting safety and efficiency in the global maritime industry. Formed in 2001, in Melbourne, Australia, RightShip offers the commercial shipping industry a ship vetting information system that is the most comprehensive on-line risk management system in the world. Owners and charterers can access the company web page to discover how a vessel has faired with respect to a RightShip inspection. Vessels are given a one to five star rating, with five stars given for a vessel considered to be in excellent condition with no risks for charterers. The number of charters and rates earned by the vessel tend to be reflected in the RightShip star rating attained. Eighty five percent of the inspection consists of a shoreside paper-based analysis of the vessel’s class and port state records together with the vessel’s ownership, P&I Club and flag state history. A thorough physical inspection is carried out over a two day period which actually contributes only 15% to the total vetting process. The inspection is a snap shot of the vessel at the time of inspection and is not intended as a definitive identifier of all matters requiring attention, rather as an indicator of the overall operation of the vessel. 46 Report types T he surveyor’s RightShip inspection documentation is divided into four documents: • FO D06 • FO D04 • FO D05 Inspection report. List of deficiencies. Preliminary inspection report. • Photographic appendix. Sample report forms are supplied by RightShip when a surveyor is appointed. T he first three documents cited are provided by RightShip in Microsoft Word format and are computer based in that the surveyor is expected to complete them on site. T he inspection report is the main document and first to be completed on board. The layout is fixed, comprising of fields requiring either information or specific questions with answers such as ‘yes’, ‘no’ or ‘not applicable’. Space is provided after each main section for comments and additional information. Deficiencies which may be found around the vessel are entered into the list of defects. T he list of defects is left with the master and/or owner’s representative before the surveyor leaves the vessel. The defects are grouped into a number of different areas: • Certificates, ship and crew. • Accommodation, food and catering. • Working spaces, accident prevention. • LSA. • FFA. • Stab, structure equipment. • Alarms. • Cargo, dangerous goods. • Loadlines. • Mooring. • Machinery. • Safety of navigation. • Radio communications. • MARPOL I - Oil. • MARPOL II - Noxious liquid substances in bulk. • SOLAS - Maritime safety and security. • MARPOL III - Harmful substances in package form. • MARPOL IV - Sewage. • ISM. • ISPS. 47 REPORT WRITING FOR MARINE SURVEYORS • Bulk carriers - additional safety. • MARPOL V- Garbage. • MARPOL VI - Air pollution. Provision is made for the master or owner’s representative to add comments if required. T he preliminary report is a two page summary of the inspection. The surveyor is asked to give an assessment of each area in terms of ‘unsatisfactory’, ‘satisfactory’ or ‘good’. An overall assessment of the vessel and operational performance is requested in terms of ‘below average’, ‘average’ and ‘above average’, together with any inspector’s comments. This report and list of defects are expected to be sent to principals within 24 hours. These are aimed at providing RightShip with a snap shot of the vessel on which it will be possible to make a decision in the event of a pending vetting request. T he full inspection report and photographs are intended to be a more comprehensive overview with a view to the longer term acceptability of the vessel. T he final document is a photographic appendix of up to 50 photographs in Powerpoint form which is forwarded to the principals with the completed inspection form. T he advantage of this type of system for surveyors is that they don’t have to be concerned with report format but only reporting skills when inputting additional information. T he combined findings are used to complement the inspector’s overall assessment of the operational capability of management and ship’s staff, together with the general condition of the vessel. All this is then reviewed in light of all the other data held on the database (history of the vessel’s flag, class, owner, operator and any changes, plus incidents, casualties and port state control). The end result is a rating which is the base of any vetting request which in itself requires a review of all data. 4.7.2. Cargill inspections Cargill is an international producer and marketer of food, agricultural, financial and industrial products and services. Its subsidiary, Cargill Investor Services Inc., is also one of the largest charterers of merchant vessels for the shipping of the company’s commodities around the world. 4.8 Cargo surveys From primary, dry bulk and bulk oil cargoes to manufactured products, 95% of the world’s cargoes are carried by sea. Cargo survey reports can range from loading/ outturn surveys to significant damage claim surveys, and may be carried out on board ship, on the wharf, in the port hinterland or at the consignee’s premises. 48 Report types Some cargo claims may be defined as high volume, low margin work for survey companies. Consequently, the survey methodology and reporting systems must be streamlined to make the process cost effective. These types of cargo survey lend themselves to a tabular format and many specialised cargo survey companies have adopted such formats. Some cargo underwriters also have standard formats. However, cargo damage investigation reports tend to be of the narrative type. Two specimen report formats are given under the appendices (see Appendix 5), one tanker outturn survey and one dry cargo discharge survey. 4.9 Container damage surveys T he majority of manufactured products and some bulk commodities are carried in containerised form. The sizes and types of containers vary considerably from the original 20-foot (ft) x 8 ft x 8 ft dry cargo container to gas tank containers and HiCu 45 ft integrated refrigerated containers. Containers tend to be stowed in cell guides below decks, although there are still vessels in service which do not have a permanent cell guide structure. Containers stowed on the hatch covers tend to have the lower two tiers held in place with the upper tiers lashed to the lower ones by twist locks. An homogenous container stow will have all containers of the same size so that they can be tied at their tops by bridge pieces. In this way, the whole stow is held together as one unit. However, in the event that containers of different heights are stowed in different stacks, the tops of the containers will be misaligned and bridge pieces cannot be used. Occasionally, shippers will need to stow 20 ft containers adjacent to 40 ft containers. T his is known as a ‘Russian Stow’ where the two 20 ft containers are stowed in a 40 ft slot. These must be linked together using double stackers, two cone pieces connected by a plate. T he above are just a couple of examples of where there can be shortcomings and weaknesses in a container stow. When conditions are such that the lashings are loaded to, or beyond, their maximum safe working loads, such locations will be the first to fail. This can result in the collapse of stacks with consequential damage to other stacks and container contents. If contents are also not correctly stowed, secured and shored, they can contribute to higher forces on the container structure. The result can be that the contents damage their own container and adjacent containers. Container surveys lend themselves to the use of pro forma reports as shown in Figure 4. Note the use of graphics to illustrate the areas of the container to be reported on. T his format is also useful for new surveyors who are not familiar with container terminology. 49 REPORT WRITING FOR MARINE SURVEYORS T his form could be printed out and held on a clipboard during the container inspection. Alternatively, the form could be stored on a laptop or computer tablet which can also be completed on site. The completed form can then be pasted into a normal report format for the final report. A specimen container damage investigation report is attached in the appendices (see Appendix 6). Figure 4. Sample container damage pro forma 50 Report types 4.10 Collision damage reports Ships occasionally collide with fixed and floating objects due to failures in navigation and/or equipment. As stated earlier, various parties may have an interest in the consequences of the damage so that several surveyors may attend on board simultaneously. As the hull damage surveyor, your role is to photograph and record the damage to your principal’s vessel. You may also be asked to carry out a ‘without prejudice’ damage survey of the other vessel. A marine surveyor will usually be appointed by either of the parties with interests in the two vessels involved in the collision, e.g. H&M underwriters, P&I Clubs, cargo underwriters, charterers, owners, charterer’s P&I Club, to carry out a damage survey of the vessel they represent. Lawyers will also be appointed for each of the parties involved. The admiralty lawyer, or his representative, will usually take statements from each of the deck officers and crew, particularly those who witnessed the collision, on the vessel they are representing. In this way they will form a picture of the events leading up to, and during, the collision. However, this is not the realm of the damage assessment surveyor. His job is only to photograph and report on the damage with calculations as to the estimated cost of repairs. Marine surveyors would not be able to fulfil their responsibilities to their clients without the co-operation of all of the parties involved and, as such, those carrying out the damage surveys of the two vessels usually have an understanding that each will be allowed to survey the other’s vessel. However, it is generally stipulated that the marine surveyor will not be allowed contact with any of the crew on the vessels they are surveying, even on their own vessel. T his type of report lends itself to the use of scanned plans and drawings. A scan of the vessel’s profile can be used to show where side damage has been sustained. A scan of a section of the shell expansion plan can be used to show the extent of the damaged area with the area(s) to be cropped and renewed. Steelweight calculations can be tabulated to further show the extent of damage with areas and weights involved. 4.10.1. Speed and angle of blow assessment A separate consultant surveyor may be appointed on behalf of either of the parties to complete an independent ‘Speed and Angle of Blow Assessment’ (SABA) survey. Again, this surveyor will not be allowed to communicate with any of the parties involved in the collision. This is because he is carrying out an independent assessment based on his own observations and calculations which should not be affected by any possibly spurious information supplied by the crew. When a marine surveyor is carrying out a survey on the opposing vessel it is known as a ‘without prejudice’ survey. 51 REPORT WRITING FOR MARINE SURVEYORS Both the surveyor carrying out the damage assessment and the surveyor carrying out the SABA surveys will measure the damage to each vessel. The vessel’s plans and scale drawings, e.g. general arrangement, capacity plan, midship sections and shell expansion, will later be obtained by the relevant lawyer and copied. These will then be distributed to the marine surveyors involved to assist with their calculations. This will allow them to draw or develop computer-generated plans of the vessels showing their relative positions during the collision. As the collision angle may give a clue to course alterations made before the collision, and because in many cases speeds may be in dispute, surveyors are appointed to examine the damage and give their opinions on speed and angle of impact. To determine the collision angle, the damage sustained by both vessels must be examined, preferably by the same surveyor, and drawings made to show exact positions at the moment of impact. A specimen SABA assessment report is attached under the appendices (see Appendix 8). T he report should include: • Principal particulars of both vessels. • General arrangements of both vessels showing areas of damage. • Details of the damage to each of the vessels. • The angle of blow assessment. • The drafts of the vessels used to calculate the displacements. • Diagrams showing the relative positions of the two vessels at the time of the collision. • Diagram showing the relative sizes of the two vessels which assists in fitting the two vessels together. • Diagrams showing the sequence of events after the collision. • An appendix of photographs of each of the vessels. Very often the subsequent damage caused when the two vessels separate can assist in the calculations. The cause of damage sustained during and after the collision should also be shown. 4.11 Specialised reports (heavy lift, tow approvals, etc) 4.11.1. Tow approvals (known as ‘Trip in Tow’ surveys in the United States) Vessels of all types and sizes are towed around the world on a daily basis, ranging from ships going to scrap to gigantic oil rigs and platforms. T he surveyor is usually appointed on behalf of underwriters to check that the arrangements for the tow are satisfactory to reduce the insurer’s risk. 52 Report types T he surveyor will need to consider and report on a number of factors: • The size of the towed vessel. • The tow routeing. • The time of year. • Expected wind and sea conditions. • Distance of the voyage. • Fuel water and stores capacities of the tug (and tow if manned). • The tug’s power. • Size of wires and other towing equipment. • Contingency plans. A set of standard voyage recommendations for various types of tow is available from various sources. These generally give excellent guidance on what the surveyor should be looking for. A search of the internet using ‘trip in tow surveys’ will bring up more hits than ‘tow approvals’. A specimen tow approval report is attached in the appendices (see Appendix 9). 4.11.2. Heavy lift surveys A heavy lift is a single commodity exceeding the capacity of normal loading equipment and requiring special equipment and rigging methods for handling. Heavy lifting is a part of the process of transportation, handling and installation of heavy items which are indivisible, and of weights generally accepted to be in the range of 1 tonne (t) to over 1000 t and of widths/heights of more than 100 metres (m) that are too large to fit into normal containers or onto conventional transporters. These oversized items are transported from one place to another on specialised vessels and then lifted or installed in place. Characteristic for heavy lift goods is the absence of standardisation and, therefore, individual transport planning is required. Typical items include generators, turbines, reactors, boilers, towers, casting, heaters, presses, locomotives, boats, satellites, military personnel and equipment. In the offshore industry, parts of oil rigs and production platforms are also lifted; some of these are also removed at the end of an installation’s working life. Surveyors may be called upon by various parties to witness heavy lifts and issue a report on the process. Some more experienced surveyors specialise in supervising heavy lifts of all types, checking the lifting equipment to check that it is adequate and that all parts of the lifting system have the appropriate load test certificates. T he surveyor will be required to ensure that all arrangements are appropriate for the lift. This will require a knowledge of lifting techniques and safe working loads of the equipment. A specimen heavy lift report is attached in the appendices (see Appendix 10). 53 REPORT WRITING FOR MARINE SURVEYORS 4.12 Expert opinions When there is a dispute over a technical matter, the parties will try to reach agreement by various means, such as mediation, before they go to arbitration or to a court to have the matter decided by a judge. To help clarify the issues involved, a marine surveyor, who may now be considered to be a marine consultant, may be asked to give an expert opinion on the matter. If, after both sides have obtained expert opinions, the parties still cannot reach an agreement, the matter will go to an arbitrator or judge. If you have never given an expert opinion before, you should consider attending one of several courses available on writing an expert opinion and appearing in court as an expert witness. The process can be time consuming and daunting, especially if you are unfamiliar with the procedures. T he role of an expert is to help the party instructing him to understand the technical aspects of the matter in dispute, as they are related to his expertise. Whilst generally being appointed and paid by one of the parties to an action, in some cases the consultant may be appointed as the single joint expert witness. Whichever the case, the expert witness is considered to be a servant of the court. His opinion is intended to help the court to reach a decision in the matter. T he report should be typed with a minimum of one and a half line spacing and using the decimal numbering system. The layout generally takes the form of: • Cover page. • Introductory page with background and outline of the case, plus your reason for being appointed. • List of documents supplied and reviewed in formulating the opinion. • Summary of opinions supplied. • List of the issues on which you have been asked to comment. • Breakdown of your opinion on each matter with reasoning and any evidence. • Expert’s declaration. Every expert opinion must include the following declaration: ‘I, Francis Grampian, Spalding Marine Surveyors, declare that: a. I understand that my duty in providing a written opinion overrides any obligation to the party who has engaged me. I confirm that I have complied with my duty. b. I believe that the facts I have stated in this opinion are true and that the opinions I have expressed are reasonable, based on the information supplied. 54 Report types c. I have endeavoured to include in my opinion those matters, which I have knowledge of, or of which I have been made aware, that might adversely affect the validity of my opinion. d. I have indicated the sources of all information I have used. e. I have not, without forming an independent view, included or excluded anything which has been suggested to me by others (in particular my instructing principals). f. I will notify those instructing me immediately and confirm in writing if for any reason my existing report requires any correction or qualification. g. I understand that: a) My opinion, subject to any corrections before swearing as to their correctness, may form the evidence to be given under oath or affirmation. b) I, Francis Grampian, be cross examined on my opinion by a cross examiner assisted by an expert. c) I am likely to be the subject of public adverse criticism by a judge if a court concludes that I have not taken reasonable care in trying to meet the standards set out above. T here are no formal qualifications for expert witnesses and there are a number of registers around the world listing experts in many different disciplines. However, you are advised only to accept an appointment relevant to your expertise and qualifications. You will end up in hot water if you try to give opinions on matters outside your ability. You are only as good as your last opinion. 55 REPORT WRITING FOR MARINE SURVEYORS This page intentionally left blank 56 Writing the report Chapter 5 - Writing the report 5.1 Structure A report should be laid out in a logical manner, i.e. it should have a beginning, a middle and an end. The beginning of the report is basically an introduction to the matter in hand, the middle usually gives the findings whilst the end summarises the situation with any necessary conclusions and recommendations. In the case of a marine survey report it is basically the story of how: • We came. • We saw. • We found. • We reported. • We concluded. • We recommended (where requested). A typical damage investigation report would take the following form: • Title page. • (Abstract or executive summary). • (Table of contents). • Particulars page. • Parties attending the survey. • Descriptions – glossary or definitions of terms used when describing the condition of an item. • Notes. • Disclaimer. • Background to the incident (sometimes called the narrative). • Survey findings (this is where you present your evidence and facts in a logical manner). • Cause of damage. • Damage repairs (including tender procedures, average repairs, temporary repairs/deferred repairs, owners work). • Cost of repairs. • (Owner’s allegation - for H&M underwriters’ reports). • Conclusions. 57 REPORT WRITING FOR MARINE SURVEYORS • Enclosures. • Photographic appendix. • Other appendices. A pleasure craft condition survey might have the following headings: • Title page. • (Abstract). • (Table of contents). • Particulars page. • Parties attending the survey. • Descriptions – definitions of terms used when describing the condition of an item. • Notes. • Disclaimer. • Survey findings, broken down into subheadings covering various areas of the vessel, e.g. structure sub-divided into: ▶ Main deck. ▶ Lower half deck. ▶ Lower deck. ▶ Upper deck. ▶ Transom deck/swimming platform. ▶ Fire fighting equipment and lifesaving appliances. ▶ Tank capacities. ▶ Navigational equipment. ▶ Machinery and equipment. ▶ Electrical. ▶ Condition of hull. ▶ General condition of the vessel/summary. • General remarks. • Defects noted. • Photographic appendix. In the case of a sailing yacht, ‘rigging’ could be added to the list. However, this may only have been inspected from the deck if a bosun’s chair is not available. Some surveyors will not carry out rigging surveys and this should be stipulated in the terms and conditions supplied to the client. 58 Writing the report Each of the subheadings will include information on aspects of the vessel relating to that section and may be broken down further if required. The amount of information inserted will depend on the amount of detail required, e.g. External hull • Above waterline – coating colour and condition. • Below waterline – antifouling, condition. • Osmotic blistering (for GRP hulls / fibre-reinforced plastic (FRP) hulls). • Planks fixings and caulking (for timber hulls). • Keel and skeg. • ‘A’ bracket(s) and cutlass bearing. • Propeller shaft and propeller. • Rudder. • Grounding damage. • Strainers, scoops, screens. • Seacocks. • Transducers. As previously stated, the layout is not set in stone but should follow a logical sequence. 5.2 Abstracts and executive summaries Some survey companies include an abstract after the title page. Abstracts, like all summaries, cover the main points of a piece of writing. Unlike executive summaries written for non-specialist audiences, abstracts use the same level of technical language and expertise found in the article itself. Unlike general summaries, which can be adapted in many ways to meet various readers’ and writers’ needs, abstracts are typically 150 to 250 words and follow set patterns. They are particularly helpful for larger reports. Their main purposes are to: • Help readers decide if they need to read the entire report. • Help readers and researchers remember key findings on a topic. • Help readers understand a report by acting as a pre-reading outline of the key points. • Index articles for quick recovery and cross-referencing. • Allow the reader to review a technical work without becoming bogged down in details. As stated above, if the report is for a more general audience or those who do not have a similar level of technical expertise, the abstract can be replaced by an executive summary. 59 60 REPORT WRITING FOR MARINE SURVEYORS An executive summary is usually no longer than 10% of the original document. Executive summaries are written literally for an executive who most likely does not have the time to read the whole document: It is a précis of the report which enables the reader to decide if he needs to read the whole report. Executive summaries include conclusions and recommendations. Accuracy is essential because decisions will be made based on your summary by people who have not read the original. Executive summaries may also summarise more than one document. A table of contents is also a useful tool to help readers find specific sections or topics. Most word processing software has the facility for automatically adding the table of contents at the front of the report. The format can also be specified. A specimen table of contents is given below. You will note that the major sections are numbered with subsections indented. Tables and diagrams are also included. TABLE OF CONTENTS 1. Vessel particulars ...................................................................................1 General arrangement .............................................................................2 2. Parties attending the surveys .................................................................3 3. Descriptions ............................................................................................3 4. Survey findings .......................................................................................3 14 August 2010.......................................................................................4 26 August 2010.......................................................................................4 27 August 2010.......................................................................................4 28 August 2010.......................................................................................4 Figure 1. Location of damage. ................................................................4 5. Stevedore damage to the vessel. ...........................................................5 6. Steel renewals 7. Cost of repairs ........................................................................................6 8. Notes ......................................................................................................6 Appendix 1 .........................................................................................................7 Photographs Appendix 2 .......................................................................................................49 Spreadsheets showing steel diminution Writing the report Appendix 3 ....................................................................................................... 70 Steelweight calculations Appendix 4 ....................................................................................................... 77 Copy of original hold frame and bracket thickness gauging measurements Appendix 5 ....................................................................................................... 92 Copy of original lower coaming thickness gauging measurements Appendix 6 ..................................................................................................... 100 Copy of agreed repair specification for hatchcoaming and coaming stays Copies of relevant certificates for ultrasonic thickness gauging equipment and personnel As may be seen above, some software packages give a page number for every item in the table of contents whilst others will list those items with the same page number listed only once. We will deal with layout in more detail later, but the first page, or cover page, of a report usually contains the survey company’s header. This gives the company’s registered name, address and other contact details, e.g. telephone numbers, mobile telephone numbers, fax numbers and email address. Some companies also have a logo included within the header which is a marketing and branding device. T he cover page should include: • The title of the report. • Date of survey. • Location of the survey. • Your company’s reference. • The client’s reference. • Date of the report. Some cover pages also have the survey company directors’ details as a footer. Note that the vessel’s name is usually written in capitals. Other vessels’ names included in the report should also be in capitals. Abbreviations and names of organisations such as the International Maritime Organization may be given in capitals. It is usual these days to omit the full stops/periods between the letters, e.g. IMO, and not I.M.O. T he date of the survey should be given in the full format, i.e. day, month and year. However, it must be remembered that there are different date formats for different areas of the world. In the United States system, the format is month, day, year, whilst the Chinese use year, month, day. 61 REPORT WRITING FOR MARINE SURVEYORS T he second page may also have a company header which is followed by an introduction which should include the reasons for the survey, e.g. ‘In accordance with instructions received from Taunton Shipmanagement Ltd, our surveyor attended on board MINNESOTA on whilst afloat/in drydock at on , in order to investigate the cause, nature and extent of damage sustained to the vessel/ cargo as a consequence of .’ T his should be followed by details of the subject at hand, e.g. the vessel or consignment’s particulars. Page 3 of your report should include a list of the parties attending the survey, their positions, company and who they are representing. T he next page is an appropriate place to include terms and conditions or disclaimers relating to your services. These are covered in Chapter 2. Apart from the cover page, every page should be numbered. It may also be advisable to have page numbering in the form of ‘Page 6 of 35’, which reduces confusion over the number of pages in the report. However, this may not be necessary if the report includes a table of contents showing page numbering. 5.3 Spelling and grammar English is today’s international language and the majority of English speakers now come from non-native English speaking countries. Just as there are many different English dialects within native English speaking countries, there are different English speaking patterns amongst non-native English speakers. T his book is written specifically for those writing reports in English. There appear to be three types of English available in word processor spelling checkers. These are: • UK English. • US English. • International English. UK English is the language of the United Kingdom and a number of the Commonwealth countries, such as Australia and New Zealand. US English is based on the language of the United States and Canada, where the spelling of some words differs from UK English. Wikipedia defines International English as the concept of the English language as a global means of communication in numerous dialects, and also the movement towards an international standard for the language. It is also referred to as Global English, World English, Common English, Continental English or General English. 62 Writing the report Sometimes these terms refer simply to the array of types of English spoken throughout the world. Sometimes International English, and the related terms above, refer to a desired standardisation, i.e. Standard English; however, there is no consensus on the path to this goal. Whatever your nationality, your report should be written in the form of English which is written and spoken by your client, e.g. you should make the effort to write in US English for US clients. Word processing software preferences can be set to the specific language spelling and grammar. There are also on-line dictionaries to help the surveyor if he is unsure of the spelling of a word. However, it should be borne in mind that there are often alternative ways of spelling some words so that a word spelled out of context may not be found during a spell check, e.g. ‘there’, ‘their’. A spell checker will also not pick up mistakes in punctuation. However, grammar checks may do so. Grammar checks are particularly useful as they make the writer think about what he is trying to say and what he is actually saying. Using these will also help to prevent ambiguity. Grammar checkers will pick up the punctuation errors, e.g. officer’s dining room which should be written as officers’ dining room (if there is more than one officer on board!). If writing a report for a US client you should remember that the United States uses only Imperial units, i.e. feet, inches, pounds, whilst the rest of the world uses SI Units, e.g. metres, kilometres, kilogrammes. To be safe, some surveyors use both in their ‘Particulars’ section, converting feet and inches to metres. Poor spelling and grammar give your client the impression of sloppiness and a lack of thoroughness in checking your reports. He may then question whether you have taken the same approach to the survey. There is no alternative to a full and complete read through of your report several times with time away from the report between each review. T he use of correct grammar is also extremely important. For those whom English is their second language, grammar can be a nightmare. Take the sentence: The quick brown fox jumped quickly over the lazy dog. • Fox and dog are the nouns (the fox is the subject of the sentence and the dog is the object). • Jumped is the past tense of the verb ‘to jump’ (jumping being an action). • Quick, brown and lazy are adjectives which describe or qualify the nouns. • Note that more than one adjective can be used in front of a noun. • Quickly is the adverb which describes or qualifies ‘jumped’, the verb. 63 REPORT WRITING FOR MARINE SURVEYORS It is often the use of adjectives and adverbs that cause problems for people writing sentences. In some languages the adjective follows the noun. This applies to both European and Asian languages. You will note that in the above sentence the adverb ‘quickly’ is after the verb. It could have been before the verb. In English adverbs may thus be before or after the verb. However, the positioning of the adverb can influence the meaning of the sentence and therefore the location of the adverb must be carefully considered. Very often the adjective or adverb can be very vague so that the reader does not get a true picture from the surveyor’s words. 5.4 Some simple rules to follow Writers often make the mistake of being too ‘wordy’ and get carried away by writing line after line of text. This tends to put the reader to sleep! Reports should be concise so that the reader will obtain the maximum amount of information in the shortest time possible. Try to ensure that your writing is balanced. If your sentences and paragraphs are too long, the reader will soon lose interest. Your paragraphs should also be structured and logical. This is achieved by: • Having no more than 14 words per sentence. • Having no more than 4 sentences per paragraph. • The first sentence of a paragraph should be a summary of the other three, i.e. the other three paragraphs will be describing what has been said in the f irst. • Start a new paragraph when the subject changes. T he above rules are not written in stone and most writers would find it extremely difficult to obey them (19 words). However, try to be as near as possible to the objectives (11 words). Don’t panic if you exceed the sizes (7 words). If you have a sentence which is necessarily over 14 words, follow it with a shorter sentence to give balance (20 words). The same applies to the paragraphs (6 words). T he third of the three objectives may also be difficult to attain but, if applied correctly, it helps speed readers to get through a report that much quicker. Speed reading is the quick glossing over of a report, picking up only key words and sentences. It is only necessary to use speed reading if an abstract, executive summary or table of contents has been omitted from the beginning of the report. As there is a need for accuracy, surveyors should not use speed reading when checking their reports! 64 Writing the report In the case of a narrative report every opportunity should be taken to break up large amounts of text with sub-paragraph headings. These act as useful signposts and help the writer identify the logical course of the report. No matter how good your reporting skills, grammatical errors will stand out and make your writing look unprofessional, preventing you from getting your message across. For those who may be unfamiliar with English punctuation, here are some simple rules to follow: • A full stop (a ‘period’ in US English) ends a sentence. Two spaces were traditionally left after a full stop, but one space is becoming more common today. • A comma is used where a pause is required in a sentence. A single space is left after a comma. • A semicolon is used to connect two independent clauses within one sentence. It can also be used it as a super-comma. • A colon is used when introducing a list or when introducing an explanation or example. Today, using just one space after a full stop is the rule. Before computers, printing presses and typewriters, letters were all the same width. To help readers see that a new sentence was starting, two spaces were inserted. Today, computers compensate for the varying widths of letters. An ‘m’ no longer takes up the same amount of space as an ‘i’. Thanks to these proportional fonts, we no longer need that extra space. 5.5 Active and passive writing All too often these days writers are guilty of writing passively rather than actively. This happens when a verb is turned into a noun, e.g. action instead of acting, limitation instead of limiting, etc. When we write, we are writing about life and life is about actions, i.e. doing things. Active writing is about keeping verbs as verbs in our sentences. Which of the following two examples shows active writing and which shows passive writing? The report was written by me. I wrote the report. or The purpose of the governor is to place a limitation on the speed of the engine. The governor’s purpose is to limit the speed of the engine. In each of these examples, the second sentence is actively written. 65 REPORT WRITING FOR MARINE SURVEYORS Notice that the second (active) sentence is also shorter than the first sentence. This is often the case when writing actively. Notice also that ‘purpose of the governor’ has been abbreviated to ‘governor’s purpose’. The sentence has thus been reduced from 16 words to 11 words. This could be further abbreviated to: The governor limits the speed of the engine. T he sentence has thus been reduced further to 8 words by active writing. Also ‘of the’ can often be replaced by using an apostrophe, e.g. The governor limits the engine’s speed. Which can be shortened even further to: The governor limits the engine speed. We can reduce the sentence to 5 words by removing the word ‘the’ so that the sentence reads: The governor limits engine speed. T he sentence has now been reduced to only 5 words from the original sixteen words and has lost none of its meaning or context (context defines the parts of a sentence, paragraph, discourse, etc. immediately next to, or surrounding, a specified word or passage and determining its exact meaning). Consider the next paragraph describing a pleasure craft: ‘The main deck consists of a large main after cabin, extending to the full width of the vessel which incorporates an open plan kitchen area in the port forward end of the cabin. Engine controls and instruments are fitted at the port forward end. On the forward starboard side steps lead down to the lower half deck. At the after end of the lounge sliding wooden/glass doors lead to a balcony which extends the full width of the vessel.’ At first glance this looks as concise as it can be but it can still be shortened and active language can be used: ‘The large main deck after cabin, extending the full width of the vessel, incorporates an open plan kitchen area at the port forward end of the cabin. At the port forward end are the engine controls/instruments and, on the starboard forward side, steps lead down to the lower half deck. At the after end of the lounge sliding wooden/glass doors lead to a full width balcony.’ T he paragraph has been reduced from 80 to 68 words. 66 Writing the report The use of a slash between controls/instruments can be used when you need to use two words to better describe something. In this case, it is used to qualify the engine console controls and instruments. Ambiguous statements are those which are open to more than one interpretation. Ambiguity can happen when trying to shorten sentences and using words which have multiple meanings, e.g. ‘I would suggest that you waste no time in making this candidate an offer of employment.’ It appears that the writer is giving an instruction not to make an offer of employment which is completely different from his intent (to make the offer as quickly as possible). Accidental omission of words can also lead to ambiguity and confusion. Consider: ‘We now have dress shirts on sale for men with 16 necks.’ T he omission of the word or symbol for inch creates a completely new meaning. Ambiguity is often created when words are incorrectly arranged in a sentence, e.g. ‘John met a woman with a wooden leg named Jane.’ Was the woman or the wooden leg named Jane? T he omission of punctuation marks can also change the meaning of a sentence: ‘Elephants please stay in your car.’ Which should have read: ‘Elephants. Please stay in your car.’ It can also happen in instructions from a client: ‘As per our phone conversation, I would like you to survey the boat I intend to purchase on Thursday morning.’ Does the client want us to survey the boat on Thursday morning or is that when he intends to buy the boat? Compare the following paragraphs and see if you can find the missing word: ‘At 05.20 hrs, 21 December 2010, the main engine stopped due to generator failure. On inspection, the crew found that the diesel oil service tank sounding pipe on the starboard side main deck was missing and they suspected that sea water had entered via the sounding pipe. The weather after leaving Vladivostok was reported as being north easterly Force 8 to 10, with a 5 metre high swell, whilst the vessel was fully loaded with a 3 metre freeboard.’ 67 REPORT WRITING FOR MARINE SURVEYORS It should have read: ‘At 05.20 hrs, 21 December 2010, the main engine was stopped due to generator failure. On inspection, the crew found that the diesel oil service tank sounding pipe cap on the starboard side main deck was missing and they suspected that sea water had entered via the sounding pipe. The weather after leaving Vladivostok was reported as being north easterly Force 8 to 10, with a 5 metre high swell, whilst the vessel was fully loaded with a 3 metre freeboard.’ Instead of a missing sounding pipe cap, the sentence implies that the sounding pipe was missing. Very often it is the order in which things are said that causes confusion. A number of surveyors think that writing what they would normally say out loud will suffice but this may not be the case, e.g. ‘Port and starboard foredeck found soft spots.’ Which implies that the foredeck found the soft spots, not that the soft spots were found on the foredeck. T his would be better said: ‘Soft spots found on the port and starboard foredeck.’ T he classic cause of confusion is to leave the date or time that something happened to the end of a sentence, e.g. ‘We arrived on board the vessel to find her drydocked at 10.00 hrs on 1 April 2010.’ Did you arrive on board at 10.00 hrs on 1 April 2010 or was the vessel drydocked on that date and time? The reader will see that the positioning of an event’s date and time can cause ambiguity and confusion. T he sentence should read: ‘At 10.00 hrs on 1 April 2010, we arrived on board to find the vessel drydocked.’ Also acceptable would be: ‘We arrived on board at 10.00 hrs on 1 April 2010 to find the vessel drydocked.’ Times and dates should preferably precede the action so that there is no confusion or ambiguity. T here is a tendency to write too much about a subject which can result in confusion and too many redundant words. For example, in a condition survey report the remarks stated: 68 Writing the report ‘Ship has had considerable financial investment during the current dry-dock and repair period. This is reflected in the above average condition found during inspection and the drive by the superintendent to achieve a high standard and maintain that standard.’ which could have been written: ‘Significant investment by owners and managers’ superintendent has resulted in an above average condition found during our inspection.’ T hese examples demonstrate one key factor in report writing. Always read through what you have written before publishing it! Better still, get somebody else to review it. T he student should practice by analysing sentences after writing them. It may be initially laborious but with practice the writer will eventually become proficient and produce more ‘readable’ reports. The writing style will also become more efficient, i.e. the minimum number of words will be used to get your message across in a readable, clear and concise manner. However, a word of caution. Do not be tempted to trim back sentences until they become unreadable. Always ask somebody else to read your work before publishing it. 5.6 Voice recognition software T he major computer operating systems have software available which will accept voice commands, and Microsoft Word also incorporates voice recognition. However, the software needs to run on computers with faster microprocessors otherwise it can be very slow. Unless the computer’s built-in microphone is of good quality and in close proximity, misinterpretations can frequently occur. It often helps to wear a headset when using the software. It can take a number of hours to train the software to recognise your voice, and there is also the problem of words used in a certain context, e.g. their/there. Accurate proof reading is absolutely necessary. It should also be pointed out that voice recognition software at its fastest will allow you to input up to 60 words per minute. A good touch typist can input 120 words per minute with higher accuracy. 5.7 Report writing software T here are a number of products on the market to assist the surveyor in writing reports, e.g. Force 5, Express Report, etc. These tend to be more suitable for condition surveys. Packages usually have standard templates for various types of survey and vessel. The language used for key statements is also standard and rather formal but there is space provided for the surveyor’s descriptions of equipment, etc. There may also be provision for very basic and rudimentary diagrams showing the location of the vessel’s safety equipment. 69 REPORT WRITING FOR MARINE SURVEYORS Such software tends to be country relevant and may not be suitable for other countries and legal jurisdictions. The surveyor is also required to collect specific information to complete the form. If you miss any information in your survey the field in the report will have to be left blank or ‘not sighted’ will have to be entered followed by an explanation as to why it was not seen. T he advantage of such software is that it helps a new surveyor to get a grasp of terminology and layout. T here is also software on the market which allows the surveyor to include digital photographs in the report text. This is often preferred by clients as they then do not have to refer to a separate photographic appendix. 5.8 Typing All printed reports must be presented in typewritten form and on good quality paper. T he keyboard of a computer is the interface between the user and the computer. Being familiar and comfortable with it is critical to using a computer to its maximum potential. Touch typing is the key to speed and accuracy, and a step towards optimising time management. Accuracy, quality of writing, grammar and spelling are essential in a report. It takes a lot of skill to be able to transfer your report straight on to a piece of paper or a computer screen, but the computer allows you to cut and paste to get the right results. Not having to think about which keys you are hitting will allow you to concentrate on content and syntax. Grammar will always be a problem, whether you can type or note, but be warned, your handwriting will deteriorate as a consequence of using the keyboard more! If you are thinking of learning how to touch type you should take a week off work to do it. It is no good trying to learn on a part-time basis and then go back to the computer at work and use four fingers again. You have to do it ‘cold turkey’. Many companies offer crash courses for those who want to learn quickly. The key is not to lose heart; be patient and stick with it. You’ll be pleased you did in the end. T he consequences for your company are that your speed of output will increase in many ways. You will not be reliant on others for the quality of your work and you will have total control over your product. Having a laptop will really set you free! In this age of the internet and email, it will also allow you speedier access to information and communications. It will also reduce the amount of time spent on reports and should reduce the size of invoices to clients. 70 Writing the report 5.9 Typography T he following section is intended to give the surveyor some background on typography so as to avoid some pitfalls that the novice may experience. A number of companies use desktop publishing software to produce their reports which enables the writer to use the following principles to maximum effect. Whilst many do not, the information may help the surveyor when dealing with ‘out of the ordinary’ text situations. Typography refers to the reproduction of letters on the page. Most people have heard of different typefaces, e.g. Times Roman or Courier. Those who write for a living should learn how to use them properly. You don’t have to use type styles from 10 different families to make a professional looking publication, but combining a few different typefaces improves contrast. T here are only a few guidelines to keep in mind. First, don’t mix similar typefaces. The whole purpose of combining them is to create contrast, so don’t mix typefaces that are only slightly different. 5.10 Typeface terminology T here are two major categories: ‘serif’ and ‘sans serif’. Serifs resemble pen strokes and extend from the ends of letter forms: a b c d e f g h. Look at the lines extending at the lower end of the letter a and the top of the letter g. T hese are called serifs, so this is a serif typeface. Now look at these same letters again: a b c d e f g h, etc. You will notice that there are no serifs. This type face is Helvetica, a popular sans serif font (‘sans’ means ‘without’ in French). Within each family of typeface there are style variations that you can use to improve contrast. For example, if you use Arial Bold for subheads, use Arial Black for headlines. A heavier weight will make the text appear thicker and darker, so that it stands out better. Differences in point size also create contrast. You can improve your understanding of these principles by comparing typefaces in word processing software. Compare the serifs, the thin/thick transitions, and the diagonal or vertical stress. Examples of serif fonts are Times, Times New Roman, Courier and Palatino. Examples of sans serif fonts are Helvetica, Arial and Verdana. Remember the main points: • Don’t mix too many fonts. • If you use more than one serif style, choose them from different categories – old style, modern, or slab serif. 71 REPORT WRITING FOR MARINE SURVEYORS • Don’t combine sans serif typefaces on the same page. Choose one, but use point size and weight to create contrast. 5.11 Tracking and kerning Tracking and kerning refers to the adjustment of space between individual letters. In leading desktop publishing programs, such as PageMaker, you can set tracking anywhere from very loose to very tight. Kerning allows you to manually adjust the space between individual pairs of letters. If you tighten the track, the amount of space between letters will be reduced, and you can fit more characters on every line. The quick brown fox jumped over the lazy dog and the dog was unhappy. The quick brown fox jumped over the lazy dog and the dog was unhappy. The quick brown fox jumped over the lazy dog and the dog was unhappy. The quick brown fox jumped over the lazy dog and the dog was unhappy. If you loosen the track, the amount of space between letters will be increased and you will get fewer characters on each line. The quick brown fox jumped over the lazy dogs and the dogs were very unhappy. The quick brown fox jumped over the lazy dogs and the dogs were very unhappy. The quick brown fox jumped over the lazy dogs and the dogs were very unhappy. See how single line spacing with shorter tracking makes the text darker and reduces readability. You will be able to see immediately which of the above three paragraphs is the most readable. Fortunately, the third paragraph, (which is the easiest to read) is the format normally used in report writing, i.e. single spacing with normal tracking/ kerning. Leading (pronounced ‘ledding’) refers to the amount of space between the lines of type, and it is an important tool for improving readability. Many lawyers prefer report text to be set at something more than single spacing. The standard appears to be 1.5 line spacing. The space between the lines of text allows those reading it to write notes above or below the text. This paragraph and most others in this document are single spaced. T he next paragraph has 1.5 line spacing. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. 72 Writing the report It is suggested that this spacing should be used if you are writing reports and opinions for lawyers. T he next paragraph has 2.0 line spacing, i.e. twice the height of the text between the text. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. The quick brown fox jumped over the lazy dog. Leading, or line spacing, is set automatically by your software, but it can be adjusted. T he default setting usually makes the leading 20% greater than the point size of the body text. In other words, a 10 point font will have a twelve point leading. T he main reason for adjusting leading is to improve readability. Narrow columns should have a smaller typeface and less leading, and wider columns should have a larger typeface and more leading. Newspapers and magazines tend to have more than one column per page whilst reports usually have only one column of text. Bear in mind that by reducing the space between lines of text, the page will become darker, so you should add white space in other areas. 5.12 The style sheet T he style sheet is another useful tool in repetitive report writing. Attributes such as typeface, type size, headings, subheadings and leading can be predefined, making the job of formatting your report quicker and easier. Once styles are defined, you can instantly apply different attributes to a single word, several paragraphs, or an entire publication. Defining your style sheet in advance saves you time and effort later. Some companies have this set up on their desktop and laptop computers to help the surveyor conform to the company’s layout requirements. T he style sheet has many advantages. If, for example, the body text of your newsletter is laid out in Helvetica, you can change it to Times Roman with a single mouse click. If you hadn’t originally tagged the body text as Helvetica, you would have to change each text block individually. It is in your interest to spend time learning how to define styles in your word processing or publishing program, and then decide how you want your report to look. What typeface and point size will you use for headings, subheadings and body text? Will you use 12-point Times New Roman for the body text? Will you use a different typeface for quotes? Most importantly, pre-defined styles will ensure that 73 REPORT WRITING FOR MARINE SURVEYORS your publication has a consistent look throughout. However, don’t forget the rule of ‘no more than four font types per page’. 5.13 Headlines Because readability of the headline is most important, don’t use upper case for every letter. Readers identify words partly by their shapes, so when all the letters are in upper case, the headline becomes rectangular and hard to read. By contrast, lower case letters have varying shapes, which helps readers identify words more quickly. If you want to create emphasis, use typography. Headlines may also be in sans serif fonts as they often do not span the full page width and because they usually only take up one line. 5.14 Numbering In this publication, the decimal numbering system is used (BS 5848, 1980). Main sections are numbered, 1, 2, 3, etc., with each subsection and sentence given a decimal subdivision. This will help your readers to keep track of where they are within the report, especially if you help them by showing the basic shape by using indentations in the table of contents. Other reports, particularly government reports, use consecutive paragraph numbering. This can be useful, especially in a long report when referring to earlier sections. T he numbering system used in this publication is: 1. 2. 3. Section 1.1 1.2 1.3 Section 2.1 2.2 2.3 Section 3.1 3.2 Secondary section 1.1.1. Subsection 1.1.2. Subsection 1.1.2.1. Sub-subsection. 1.1.2.2. Sub-subsection. Secondary section Secondary section Secondary section Secondary section Secondary section Secondary section Secondary section As may be seen, sentences and sub-sentences may be indented to improve presentation and layout. Most word processing packages will do the numbering automatically 74 Writing the report if instructed to do so. Further examples of this numbering system are given in the appendices. T his type of numbering system is preferred for narrative type reports and by lawyers as each sentence is easily identifiable. Increased line spacing also allows notes to be written between lines. Numbering sections will help to give the report a structure. Different survey companies have their own preferences as to numbering or lettering. Some companies prefer to use upper case letters to label each section, e.g. AAA BBB CCC DDD, etc. Others prefer single lettering, e.g. A B A1 A2 C, etc. Others prefer Roman numerals, e.g. I II III IV V, etc. T here is also the alphanumeric system: 1. 2. Section a. Section a. Secondary section i Subsection ii Subsection Secondary section i Subsection ii Subsection 75 REPORT WRITING FOR MARINE SURVEYORS However, this system does not lend itself to automatic numbering in word processing software packages. Whichever numbering system is used, it must be uniform throughout the document to prevent confusion. Page numbering should also be uniform throughout a report and preferably start on the title page. However, some prefer not to number the title page of a report, starting numbering at the first page of text. This arrangement does not lend itself to automatic page numbering by word processing software. As the title page may have a company header and footer, it will probably not be numbered. Numbering could start on the third page with the number 3. 5.15 Units of measurement In 1971, most of the world converted from Imperial units to the System Internationale de Unites, or SI system. The basic units are shown in Figure 5. T hese are the units currently used by most countries, except for the United States which still uses the Imperial system. When writing a report for a US client you should consider using Imperial units. However, most surveyors continue to use SI units with Imperial units in parentheses, e.g. 1 m (3.3 ft). Some basic rules relating to units are: • Be sure to use the correct symbol for units, e.g. Nm not nm, i.e. Newton metre and not nautical mile. • Do not use the plural of abbreviated units, e.g. ms, Ns as this may mean something completely different. • Use either the single letter abbreviation or the full name of the unit and nothing in between, e.g. s or second, and not sec Where necessary, refer to SI units with other units in parentheses, e.g. 5 m (16.25 ft). • Do not combine abbreviations with full words, e.g. kilogramme/m3 should be kg/m3. • No full stop or period used after units unless it is at the end of a sentence. • The slash is used for dividing units, e.g. m/s = metres/second whilst the superscript may also be used e.g. ms-1. • Do not drop units, e.g. 35 m x 35 m, not 35 x 35 m. • Always leave a space between the number and the unit, e.g. 25 m diameter circle. 76 Writing the report Figure 5. Basic units of measurement 77 REPORT WRITING FOR MARINE SURVEYORS 5.16 Use of brackets T he term bracket generally refers to all types of brackets, but there are specific types. T here are several main types of brackets: • Round brackets, open brackets or brackets, known as parentheses in the United States. Square brackets, closed brackets, known as brackets in the United States. • Curly, squiggly, definite, swirly, birdie, Scottish or squirrelly brackets, known as braces in the United States. • Angle brackets, triangular brackets or inequality signs, known as chevrons in the United States. 5.16.1. Brackets ( ) T hese contain material that could be omitted without destroying or altering the meaning of a sentence. They may also be used to add supplementary information, e.g. an alternative meaning to a word or set of words. T hey are also used in a report to refer to photographs, diagrams or tables, e.g. (see Figure 5), (see Photograph 5). T hey are also used when abbreviating long names which would take up a lot of space when repeated numerous times in a text. The abbreviation is included in brackets after the first mention of the full title so that the abbreviation can be used later, e.g. International Maritime Organization (IMO), International Institute of Marine Surveying (IIMS), National Association of Marine Surveyors (NAMS), Institute of Marine Engineering, Science and Technology (IMarEST). 5.16.2. Square brackets [ ] Square brackets are mainly used to enclose explanatory or missing material usually added by someone other than the original author, especially in quoted text, e.g. [comments added relating to information in the report which may be disputed]. 5.16.3. Curly brackets { } Curly brackets are sometimes used in prose to indicate a series of equal choices, e.g. ‘Select your jacket {coat, sweater, pullover} and put it on.’ T hese are more commonly found in mathematics. 5.16.4. Angle brackets < > Angle brackets are often used to enclose highlighted material. Some dictionaries use chevrons to enclose short excerpts illustrating the usage of words. Notice that the full stop or period in the examples above is outside the brackets and included with the main text, unless you are bracketing a whole sentence. 78 Writing the report 5.17 Use of i.e. and e.g. When do you use i.e. and e.g.? The Latin abbreviations ‘i.e.’ and ‘e.g.’ occur very frequently in writing. They stand for: i.e. = ‘that is,’ which written in full in Latin is ‘id est’. ‘i.e’ is used in place of ‘in other words’, or ‘that is’. For example: ‘Each report will be tackled in its own way. If you start with a certain presentation style and layout you must stick with it throughout the report, i.e. you must be consistent.’ T he reader will note that a comma has been inserted after the text which precedes the i.e. Some people prefer to use a comma, while others do not as the ‘i.e.’ stands alone as an abbreviation. e.g. = ‘for example’ and come from the Latin expression ‘exempli gratia’. It is often used to replace the words ‘such as’. For example: ‘Information on merchant ships is available from many sources, e.g. Lloyd’s Register of Shipping, Lloyd’s Maritime Directory, World Shipping Directory.’ Again, a comma has been included after the text which precedes the ‘i.e’. Examples of their use are given throughout the text and in the specimen reports contained in the appendices. 5.18 Lists If you are writing a sentence which has more than two items listed within it you will see that the sentence becomes longer than advised, e.g. ‘We have received copies of: the vessel’s certificate list, main engine cylinder liner and piston readings, main engine crankshaft deflections, shipyard record of main engine inspection/calibrations, container stowage plan and stability calculation sheet which will be appended to our formal report.’ (42 words) T his is when the use of bullet points or numbering becomes essential. One and a half or double spacing of a list will allow the reader to make notes between the lines. Some writers prefer to keep the format of the bullet points the same as the sentence, i.e. because they are in a sentence they will start with lower case letters and finish with a comma, the last one having a full stop or period, e.g. 79 REPORT WRITING FOR MARINE SURVEYORS We have received copies of: • the vessel’s certificate list, • main engine cylinder liner and piston readings, • main engine crankshaft deflections, • shipyard record of main engine inspection/calibrations, • container stowage plan, • stability calculation sheet. These will be appended to our formal report. Others believe that to give more stress to the list each item should be separate and therefore start with an upper case letter and end with a period or semicolon, e.g. We have received copies of: • The vessel’s certificate list; • Main engine cylinder liner and piston readings; • Main engine crankshaft deflections; • Shipyard record of main engine inspection/calibrations; • Container stowage plan; • Stability calculation sheet. These will be appended to our formal report. Some consider that the above might also be used when each of the items is being stressed, rather than just a list of items. Others believe that each item should not have a period, comma or semicolon. However, the last item should be followed by a full stop. We have received copies of: • the vessel’s certificate list • main engine cylinder liner and piston readings • main engine crankshaft deflections • shipyard record of main engine inspection/calibrations • container stowage plan • stability calculation sheet. These will be appended to our formal report. Whichever format is selected, its use should be consistent. 80 Writing the report Alternatively, numbering can be used: We have received copies of: i. ii. iii. iv. v. vi. the vessel’s certificate list main engine cylinder liner and piston readings main engine crankshaft deflections shipyard record of main engine inspection/calibrations container stowage plan stability calculation sheet. These will be appended to our formal report. or lettering: We have received copies of: a. the vessel’s certificate list b. main engine cylinder liner and piston readings c. main engine crankshaft deflections d. shipyard record of main engine inspection/calibrations e. container stowage plan f. stability calculation sheet. These will be appended to our formal report. Remember that the lettering or numbering should not contradict the numbering system used for the body of your report. However, this rule can be broken where the writer needs to stress the list of items or separate them from the main text. You will see that it is easier for the reader to identify each individual item, improving readability. Lawyers also like this approach as they can write notes next to the items in the list and refer to the identifying letter or number when responding to your report. It is uncertain which is the absolutely correct version, and both appear to be acceptable to our clients, so it is your choice as to which you use. Word processing software packages have this feature which automates the process. 5.19 Presentation and layout Experienced surveyors will tell you that report presentation is half the battle. The other half is getting the technical aspects correct. Reports may be double spaced although this is not a hard and fast rule. It should be printed on one side of the paper only. Adequate margins must be left on each side of 81 REPORT WRITING FOR MARINE SURVEYORS the paper, preferably 1inch (25 mm) on the left side and no less than ¾ inch (18 mm) elsewhere. Pages should be numbered so that they can be referred to in the table of contents. Report presentation is a combination of layout and graphics. A good layout improves readability by arranging text and graphics in a logical order. T hose reading English begin reading at the top left corner and work their way across the page from left to right until they reach the bottom right corner. Any design working against this principle may frustrate readers. For example, if you place the headline in the middle of the page, readers will have to return to the top before they can begin reading the body text, which contradicts natural eye movement. This is confirmed by test subjects who have reported good comprehension on layouts that supported natural eye movement. When writing, organise sentences and paragraphs in a logical sequence so that readers will understand your message. You should approach layout the same way. A good page design balances function with form, consistency with contrast, and places successful communication with the reader above all other considerations. Layout is like a jigsaw puzzle. Every piece fits together to make the whole. In typography, a font is traditionally defined as a complete character set of a single size and style of a particular typeface. For example, the set of all characters for 9-point Times New Roman is a font, and the 10-point size would be a separate font. Bold, italic, outline, etc, are also separate fonts. Here are some simple rules to follow: • Use no more than four fonts on a page and in a report. • Use white space or boxes to separate important information. • Use bold and/or larger font size for headings and subheadings. • Use bullet points or numbering to list more than two items and to call attention to individual points. • For greater effect, quotes may be between inverted commas, in italics and indented at both sides (see below). • Use sans serif fonts for titles and serif fonts for large amounts of text (the serif helps the reader to follow the line of text). • Body text should be left aligned and not justified (justified text is difficult to read on full page width text). • Ships’ names should be in all capitals (most reputable survey companies tend not to use MV or SS before a ship’s name as this information is usually included in the report). 82 Writing the report • Keep headlines to a minimum. A quick glance should tell the reader what the subject is. A guideline is a maximum of three lines. • Left justified headlines are easier to read than centred headlines. Note: readers will note that the body text of this book is fully justified. This is generally accepted in book publishing. The reports attached under the appendices are left justified to emphasise the difference from the body text. As a general guideline, shorter quotations of less than one line may be embedded in your text between inverted commas without italics or indenting. However, larger quotations should be indented to give more effect, to act as a ‘hook’ (see later) and to help break up large screeds of text. Credit should be given to the originator of the quotation. With larger quotations this may be on a separate line below the quote. With smaller quotations it may be included in the text, e.g. ‘To quote Mike Wall, “Necessity may be the mother of invention, but an engineer is usually the father”.’ Your author prefers to use single inverted commas for quotes taken from books, papers and magazines whilst using double inverted commas to quote words which have been spoken. Others may have different views on this approach. 5.20 Balance Balance is another word for concerns about symmetry and asymmetry. Symmetry provides stability and rest for the eye, while asymmetry creates tension and visual interest. Finding ways to create balance often depends on the type of report. T he appearance of your report should be consistent. This is enhanced by aligning the elements on individual pages and creating strong page-to-page alignments. If you are including photographs in your text, align the tops of the photographs with the x-height (the top of the lower case letters in a line of text) in the adjacent column, and give headlines the same alignment from page to page. Repetition of key elements (logo, box, rules, graphics, etc.) from page to page also standardises the appearance of your report. Some of the larger marine consultancies use a standard format for report headers and footers. An example is given hereafter: 83 REPORT WRITING FOR MARINE SURVEYORS XXX MARINE CONSULTANTS LTD CONTINUATION- 1 JOB NO SHIP’S NAME Text starts here. l l l l l l V Text finishes here. /Cont’d .... Having a continuation page header ensures that your company name, the job number and job title are on every page of the report. This is advisable as others could photocopy your report and use it for other purposes. Copyrighting your report should also be considered. Some companies include their logo at the top or bottom of every page. Member companies of IIMS are allowed to include the IIMS logo in their reports. Individual members may only use the logo with their name, e.g. when signing the report. It should be borne in mind that, if the logo is in colour, reports may have to be printed on a more expensive colour printer. However, repetition without variety becomes monotonous so you may choose to use a photo or graphic to add interest to a page (see later). The repetitive elements create visual coherence, while the occasional incongruous element creates contrast, thus giving visual variety. T he above comments relate to the report’s appearance. Balance also refers to the tone of the report. As stated previously, a surveyor must give a fair and balanced view. T here is the old adage of ‘sugar before a pill helps the patient take the medicine’. In the same way, it helps the client accept your negative comments if you preface them with complimentary remarks. 5.21 Numerals and words When do you use numerals in a sentence and when do you use words? There are, again, rules which must be followed. 84 Writing the report i. ii. iii. iv. It is not good practice to start a sentence with a numeral. A number should be expressed in words at the beginning of a sentence or numbers used somewhere later in the sentence. Spell out single digit whole numbers. Use numerals for numbers greater than nine, e.g. We noted five white sausage fenders around the vessel. We noted 10 lifebuoys around the vessel. Be consistent within a category. For example, if you choose numerals because one of the numbers is greater than nine, use numerals for all numbers in that category. If you choose to spell out numbers because one of the numbers is a single digit, spell out all numbers in that category. We noted 5 sausage fenders and 10 lifebuoys around the vessel. We noted five sausage fenders and ten lifebuoys around the vessel. If you have numbers in different categories, use numerals for one category and spell out the other, e.g. We noted 5 fire extinguishers on three decks and 2 fire blankets on two decks. Note that fire extinguishers and fire blankets are represented with figures; decks are represented with words. v. vi. vii. Always spell out simple fractions and use hyphens with them, e.g. One-half of the fenders were found deflated. Two-thirds of the fire extinguishers had not been recently inspected. A mixed fraction can be expressed in figures unless it is the first word of a sentence, e.g. We noted a 5½ inch gap in the cap rail. We noted a five and one-half inch gap in the cap rail. With numbers that have decimal points, use a comma only when the number has five or more digits before the decimal point. Place the comma in front of the third digit to the left of the decimal point. When writing out such numbers, use the comma where it would appear in the figure format. Use the word and where the decimal point appears in the figure format, e.g. $13,668.15 (thirteen thousand, six hundred sixty-eight dollars and fifteen cents). $1044.11 (one thousand forty-four dollars and eleven cents). 85 REPORT WRITING FOR MARINE SURVEYORS Note that this is often the method used for quoting a price for a survey. viii. Hyphenate all compound numbers from twenty-one to ninety-nine. 5.22 Date and time formats Marine surveyors regularly need to inspect a medical locker to see if the medicines are in date. They are never easy to find, if there are any. The better medicine producers have the dates embossed into the packaging but then the date is continuous, i.e. 091007, which is the Chinese way of saying 7 October 2009 but could be misunderstood by an Englishman who might interpret it as 9 October 2007 or an American who might see it as 10 September 2007. With current dates at the beginning of the year and month all being in single figures, it is imperative that the date is spelled out in full rather than using numerical abbreviations. Abbreviating the month in text and numbers is acceptable, e.g. 10 Sept 2007. T he reader may note that the day is represented by a number only and not followed by ‘th’ or ‘st’, e.g. 10th or 1st. The letters are known as contractions and do not tend to be used in modern writing. However, some word processing software will apply the contraction automatically so that it needs to be turned off in the software preferences Some basic rules to avoid confusion when using dates and times: • Use noon and midnight rather than 12.00 am and 12.00 pm. • Times should be expressed in 24 hour terms, e.g. 0235 hrs. Whilst the latter of the two formats shown above may be considered as an informal way of representing times it appears to reduce the possibility of confusion. It also lends itself to the reporting of times when detailing the chronology of an event, e.g. 27 Feb 1630 hrs. Left company offices, taking taxi to terminal 1700 1955 2015 2025 2045 2100 2125 2155 2240 2300 2315 2340 Arrived on board the COLORADO at berth 13E, Terminal 8 IDAHO 1 moving alongside. Starboard winch snagged Starboard winch cleared and IDAHO 1 alongside Barge OKLAHOMA alongside Lift of rudder horn commenced Adding additional springs to secure IDAHO 1 to vessel Starboard mooring wire to IDAHO 1 parted Load lowered into Bay 38 port side outboard Barge OKLAHOMA alongside Lifting rudder cone Load lowered into Bay 38 port side inboard IDAHO 1 clear of vessel. 86 Writing the report 28 Feb 0020 0030 0045 0145 0200 0205 0300 IDAHO 1 moored alongside port after end of DELAWARE Barge OKLAHOMA alongside and rigging taking place Lifting rudder blade Lift landed on flatracks on top of containers on port side of Bay 82 IDAHO 1 clear of vessel Departed vessel Arrived at company offices. Note that this is another use for the spreadsheet imported into a report. The border around the spreadsheet cells has been omitted. 5.23 Hooks Use a hook, such as an interesting photo, graph or graphic, to get the reader’s attention. When we speak, we emphasise ideas by changing our tone of voice. In a layout, a hook serves the same purpose. It tells the reader that something is important. Emphasis can be created in different ways. Text in a large point size, for example, shouts at the reader: ‘I’m important! Read me now.’ In the case of marine survey reports, this may be a stunning photograph of the subject vessel or cargo on the cover page. 5.24 Colon and semicolon T he colon and semicolon are the most troublesome punctuation marks for writers. Look at the following statement. Example: This could be a complete sentence; this could be another one. You will see that the colon is being used to introduce an example whilst the semicolon is used to connect the two clauses. You may also see that the two clauses may not be stand alone sentences as they are interrelated and interdependent. You should not use a semicolon to connect two complete sentences if there’s a conjunction between the clauses (and, but, etc.). In this case you should use a comma. You will also see the use of the colon throughout this text to introduce a list. If you are confused about the use of the semicolon, it is advisable to rewrite the sentence into two separate sentences. Another punctuation mark which often creates problems is the apostrophe. It is used to imply possession of something, e.g. Mike’s bicycle, meaning the bicycle which belongs to Mike. However, there are times when its use may be confusing, for example: View of officer’s dining room. or View of officers’ dining room. 87 REPORT WRITING FOR MARINE SURVEYORS In the first case, the dining room belongs to one officer, in the second, it belongs to all officers. T he apostrophe is also used to abbreviate words, e.g. don’t (replacing ‘do not’), isn’t (replacing ‘is not’), you’re (replacing ‘you are’), she’s (replacing ‘she is’), etc. If the reader is in doubt as to its use in such cases, revert to the original and full version, i.e. ‘it is’ instead of ‘it’s’. It should also be remembered that where a word ends with an ‘s’ there is no need for the use of an additional ‘s’, e.g. ‘Denis’s hat’ may be written as ‘Denis’ hat’. T he hyphen is another punctuation mark which is often used in error. It is normally used to: • Make clear the unifying of the sense in compound expressions such as punch-drunk, cost-benefit analysis, or weight-carrying, or compounds in attributive use (that is, in front of the noun), as in an up-to-date list or the well-known performer. • Join a prefix to a proper name (e.g. anti-Darwinian). • Avoid misunderstanding by distinguishing phrases such as twenty-odd people and twenty odd people, or a third-world conflict and a third world conflict. • Clarify the use of a prefix, as in recovering from an illness and re-covering an umbrella. • Clarify compounds with similar adjacent sounds, such as sword-dance, co opt, tool-like. • Represent the use of a common element in a list of compounds, such as four-, six-, and eight-legged animals. • Divide a word across a line-break (most word processing software will move a word to the next line rather than hyphenating it). It is often used in a sentence to include information, e.g. James Burke - leader of the council - recently stated that ... In the above case, commas would have been more appropriate, i.e. James Burke, leader of the council, recently stated that ... Adding a hyphen incorrectly looks unprofessional. If you are unsure, don’t use them. Clarity in punctuation will help to avoid ambiguity and confusion when reporting. 88 Writing the report 5.25 Lack of colour Unless a publication is in colour, white, black and grey are the only tones on the page. Blank areas comprise the white space, graphics the black, and text the grey. T he goal is to balance these tones on every page. For instance, too much white space can make it hard for readers to follow the flow of a document, and if you clutter the page with too many graphics, rules and subheads, it will appear dark and busy, while the greying effect of a text-heavy page will discourage even the most interested readers. Although each tone is equally important, they have meaning only in relation to each other. White space is only useful if it is contrasted against the black or grey tones. Black tones only provide contrast if there is blank space and text on the page. Good designs balance the three tones together. Most reports are produced with black text on white paper. It is only where colour logos or photographs are included that there is a requirement for more expensive colour printing. 5.26 Widows and orphans T his term is used to describe when a single line of a paragraph is on a previous/ following page. The widow is on the page before the bulk of the paragraph, the orphan is on the following page. To prevent a page break from separating a single line from the rest of the paragraph, the software should give the ability of ‘widow control’. When activated, the paragraph will be completely transferred to the following page. 5.27 Paragraph spacing and indentation T he reader may have noticed that the author uses a full line to separate paragraphs with the start of each paragraph adjusted to the left of the page. Before computers and word processing, paragraphs started on the line immediately following the last paragraph. To identify and separate the paragraphs, the first line of each paragraph was indented approximately half an inch (12.5 mm). The latter layout tends not to be used today. For those surveyors establishing themselves for the first time, with little or no experience of report writing and layout, it will take some time to find the correct combination of the above. It is advisable to put your layout ideas on paper, then pass them to someone unfamiliar with marine surveying so that he concentrates only on checking if your report is readable. 89 REPORT WRITING FOR MARINE SURVEYORS 5.28 Diagrams T here is an old saying that ‘A picture says a thousand words’. For a surveyor this means that a picture or graphic can replace a thousand words in a report. As an example, try to describe a spiral staircase. You will see that it is easier to take a photograph or draw a sketch. Before digital photography, diagrams and sketches were particularly useful in faxed or emailed preliminary reports. The ability to send digital photographs has greatly enhanced the communication of findings to clients, and has reduced the need for diagrams. However, there will be times when the surveyor needs to explain the operation of a piece of equipment or the sequence of events leading up to a casualty. This is when diagrams or sketches come into their own. The surveyor is advised to learn basic technical drawing techniques (see later) as these help to make drawings more understandable. As another example, try to describe a ship that you have recently surveyed in less than one thousand words. Your description should include the number of holds, watertight bulkheads, hatch covers, cranes, water ballast, fuel and fresh water tanks. If the ship has a particularly unusual tank arrangement, the description will be very involved and take some time to write. Figure 6 gives an illustration of how a diagram can save you this time and effort. Figures 6 and 7 were drawn with fairly basic drawing software. There are far more elaborate drawing software packages on the market and available to surveyors. Some of them are also free to download from the internet. When graphics are used, high-quality drawing skills are essential. Drawings must be neat and accurate, and lettering and linework must be precise, dark, and of high quality. Most marine engineers have been trained in the necessary drawing skills for technical drawing. The following notes are intended for those who are unfamiliar with technical drawing principles. All drawings are made of lines. When draftsmen draw plans they use pencils of varying hardness to give different line thicknesses representing various parts of the drawing (as shown in Figure 8). 90 Writing the report Figure 6. General arrangement of tanks and holds T he same principles can be used for pleasure craft as shown in Figure 7. 91 REPORT WRITING FOR MARINE SURVEYORS Figure 7. General arrangement of pleasure craft main deck 92 Writing the report Figure 8. Line thicknesses and uses 93 REPORT WRITING FOR MARINE SURVEYORS As may be seen in the above figures, the thicker lines are used for outlines or to stress items. Thinner lines are used for lesser details. The thickness of lines when drawing on paper is achieved by the hardness of the pencil. Softer pencils, such as HB, are used for thicker lines, harder pencils, such as ‘2H’, are used for thinner lines. Dotted or dashed lines are used for hidden objects. These can be used for straight lines, boxes, curves and circles. Centre lines show the central axis of an object and are usually thin, comprising alternate long and short dashes which are evenly spaced. These can also help you to ensure that drawings are symmetrical when necessary. Dimension lines are thin lines used to show the extent and the direction of dimensions. In Figure 6, dimension lines are used to show the location of the engine room. Note that the arrows are longer and thinner than normal. The two horizontal lines restricting the dimension line are known as extension lines. A leader line is a continuous straight line that extends at an angle from a note, a dimension or other reference to a feature. An arrowhead touches the feature at that end of the leader. This is represented in Figure 6 by the line leading from the words ‘Duct Keel’ to the duct keel itself. When there are lots of leader lines pointing out features they should not cross each other. Where they coincide in a view, certain lines take precedence. Since the visible features of a part (object lines) are represented by thick solid lines, they take precedence over all other lines. If a centreline and cutting plane coincide, the more important one should take precedence. Normally, the cutting plane line, drawn with a thicker weight, will take precedence. The following list gives the preferred precedence of lines on your drawing: 1. 2. 3. 4. 5. 6. 7. Visible (object) lines. Hidden (dashed) lines. Cutting plane lines. Centrelines. Break lines. Dimension and extension lines. Section lines . All of the above lines may be drawn using software drawing packages. However, some may not have the ability to draw dotted or dashed circles. These are usually only available in computer aided design (CAD) packages. It may be seen from the previous diagrams that shading or filling is also helpful in identifying features. Crossed diagonal dashed lines are also used to signify tanks. 94 Writing the report A variety of lines are shown in Figure 9. Note also the use of ‘sectioning’. A section of the coupling is shown on the right to show the rubber elements. The section has been taken through the axis A-A. This can be done anywhere in a piece of equipment to show important features. Figure 9. Coupling configuration Some drawings will need multiple views or projections. An orthographic projection shows the object as it looks from the front, right, left, top, bottom or back. Each of these views will be positioned relative to each other according to the rules of ‘first angle’ or ‘third angle’ projection. Third angle projection, where the front elevation is situated on the right, is used by the United States. First angle, where the front elevation is situated on the left of the paper, is used by most other countries. Examples are shown in the Figures 10 and 11. 95 REPORT WRITING FOR MARINE SURVEYORS Figure 10. First angle projection of an object T he above object would then be represented on paper as shown below. Figure 11. First angle projection of an object on paper 96 Writing the report Often, a full projection of an object is not necessary. However, it is often advisable to sketch an object in two dimensions rather than the single dimensions shown in Figures 6 and 7. There are two other types of projection which do this. These are isometric and oblique projections. The diagram below shows the difference between the two. Figure 12. Difference between isometric and oblique projections T he isometric projection shows the object from angles in which the scales along each axis of the object are equal. Each of the bottom lines of the drawing are at 30⁰ to the horizontal base line. In the oblique view the front of the diagram is horizontal with the sides at 45⁰ to the horizontal. Those new to sketching often prefer the easier oblique projection method. Having seen the above two diagrams which view has been used in Figure 10? (Answer: It is an isometric projection of the object.) You may also have noted that all the text used in Figures 9, 10 and 11 is sans serif. It may also be in italic form as used in Figure 10. Serif fonts are not used with drawings. Note also the use of shading to give the objects more depth. The artist has to imagine from which direction the light is being shone and shade accordingly. Again, most drawing packages have shading options. Some even have auto-shading. Shading can also be used to represent particular materials such as timber (curved concentric lines) or liquids (dashed lines leading to one solid line at the top) or damaged areas. T he use of shading to show damaged areas is demonstrated by Figure 13. T he following diagram was drawn by hand. Propeller outlines are available on the internet and are available for scanning. Relevant information can then be added to the diagram to show damage and/or repairs. 97 REPORT WRITING FOR MARINE SURVEYORS Figure 13. Use of shading to show propeller damage repairs You will note that there has been no use of perspective in Figure 12. This is where the eye perceives the object as being smaller the further away it is from the eye. In the oblique view in Figure 12, the object actually appears to be getting larger further from the eye. This is because the object has been drawn with absolute 45⁰ angles. Either of the upper lines would need to be drawn at approximately 40⁰ to give the impression of depth and perspective. You may also note that Figures 6 and 7 are stated to be ‘not to scale’. All types of plans are usually ‘scale drawings’, meaning that the plans are drawn at a specific ratio relative to the actual size of the object. Various scales may be used for different drawings, e.g. 1:50, which means that the plan is 1/50th of the size of the original. This means that all dimensions are to that scale, i.e. the length, breadth and depth are all 1/50th of 98 99 Writing the report the original. In Figures 6 and 7, the length and breadth of the vessels may not truly represent the ratios of the actual vessels. Sometimes it might be useful to increase or exaggerate the beam in a ship drawing to be able to include all tanks and other points of interest. Scale drawings are particularly useful when representing hull damage. Most drawing packages also allow for various scales to be set. You can adjust your scale to fit the drawing onto the page. When drawing accurate scale drawings of vessels it is necessary to obtain the frame spacing. These should be marked out on the drawing centre line to be used as reference points, the surveyor having recorded the locations of damage and various objects relative to frame numbers. A major time-saver with respect to drawings is to obtain copies of original drawings from the ship or equipment manufacturer. Using a scanner, this can be copied electronically and used in a drawing package. Figure 14 below shows a scanned image of a camshaft/pushrod arrangement with text added separately. Figure 14. Diagram showing configuration of hydraulic actuator cam follower REPORT WRITING FOR MARINE SURVEYORS Figure 15. Turboblower rotor illustration 100 101 Writing the report Figure 16. Schematic diagram of turboblower REPORT WRITING FOR MARINE SURVEYORS Figure 17 below shows the location and extent of damage to a turboblower, the text having been added separately. Figure 17. Diagram showing location of crack 102 103 Writing the report Sometimes it is not possible to obtain information on an engine and a sketch must be drawn as shown in Figure 18. Figure 18. Diagram showing engine timing gear arrangement It may also be noted that each of the diagrams has a border. This is intended to frame the picture and helps to give uniformity when the diagram is inserted into the text. The frame should be equidistant from each side of the diagram, again for uniformity. You will also see that the body text of this section is above and below the diagrams. With some software, e.g. Pagemaker, it is possible to ‘wrap’ the text around drawings, sketches and photographs. This is useful where the graphics are small and can be inserted without dominating the page. However, word wrapping should be used sparingly as it may cause your diagrams to be lost in the text when you really need to draw attention to them. To summarise, there is no limit to what can be represented by a sketch or diagram. There is plenty of software out there to assist. The only limit is the surveyor’s inventiveness, ingenuity and skills. REPORT WRITING FOR MARINE SURVEYORS 5.29 Photographs Photographs are critical to a report because they act as evidence in support of your f indings. Like diagrams and sketches, they can save a thousand words in your report, but only if they are appropriate and of good quality. As they may be used as evidence in court, they will need to be originals and unaltered in any way. Traditional film photographs are usually accepted without question in courts and arbitrations. However, digital photographs can be easily altered and for some time were not accepted in court. As software now allows instances of alteration to be identified, digital photographs are now accepted. However, the surveyor may be asked to swear on oath that they are originals. With digital photography it is now possible to see what you are photographing before you take the photograph. This gives the photographer the ability to frame the photograph and see if the outcome is a success before the images are developed and printed. Most digital cameras are also fully automatic so that the user just points and shoots, usually with excellent results. Their ability to take high quality images is defined by the number of pixels which the electronic chip, the charge couple device (CCD), can capture. This is usually measured in megapixels; the higher the number, the higher the sensitivity and the better the quality. As a comparison, a 3.3 megapixel camera is compatible in quality terms with a traditional 35 mm film camera. The surveyor will need to weigh the quality of the camera with its size. The higher quality digital cameras can be similar in size to a high quality single lens reflex (SLR) film camera, and can be bulky and heavy. T here will be times when automatic shooting is not appropriate, e.g. when the subject has a lot of back light behind it. If the picture is taken in auto mode the result will be a dark subject with a bright background. In this case, it is necessary to use the manual f lash option to illuminate the subject. Digital cameras have additional functions which allow the user to decide on how he will take the photograph, e.g. close-up, wide angle and telephoto/zoom. As surveyors, we don’t tend to take too many photographs of people so the ‘red eye’ function will probably not be used so often. T he ‘macro’ function is used for taking close-up and more detailed photographs. This is useful when photographing damaged engine parts and cargo. The wide angle mode is used when taking a panoramic view, such as harbours, landscapes or other large spaces. The zoom function is used to get closer to your subject and ensure that you do not waste space in the photograph. Another option which may be included on a camera is the ‘document’ function which allows clear photographs of documents, a very useful tool when photographing ship’s log book pages. Date and time imprinting are also useful tools as they are evidence of when you took the photograph. Unfortunately, many digital cameras do not show the date on 104 Writing the report the photograph on the camera or computer screens. You can only see it when the photograph is actually developed by a photo shop. One other advantage of digital photography is that the user can experiment with the various settings to gain expertise in the correct use of the camera without the need for printing out the photographs to see the results. As mentioned above, the key to a good photograph is preparation. Here are some basic rules: • Take your time, don’t rush it. Digital cameras need a little time to adjust their settings to suit the conditions. • Get yourself into the correct position to get the right aspect and as much information as possible into the picture. • Frame your subject so that, like diagrams, there is an equal amount of space around the edges. • When taking the photograph you should try to hold the camera with both hands to ensure it is steady. • Control your breathing by taking the photograph after you have exhaled and just before you inhale. In this way, your body will be in a relaxed state and your hands should be steady. Some cameras have an anti-vibration or tremble mode which reduces the effects of trembling hands. However, sensitivity and quality of picture are sacrificed to enable this mode. T here are other problems which surveyors face when taking photographs, such as water spray, noise, dust, etc. All of these can cause the camera to go out of focus or for the subject to be obstructed. It is advisable to wait a few minutes before taking your shot if you have just climbed down a rusty topside tank ladder, entered a hold full of grain or in a boatyard with GRP dust in the air. Health and safety issues should take priority in such situations. When taking photos of specific objects, such as machinery or hull damage, first take a general photograph of the area concerned. Then zoom in to get a closer photograph of the piece of equipment. Follow this by a close-up photograph of the damage, where necessary using the ‘macro’ function. It also helps to use another object as a reference to give an idea of size. This could be a ‘T’ square or a 6-inch ruler with inch or mm marks placed next to the object. If you don’t have such a measure, a ball point pen will often suffice. Sometimes it may not be possible to get an appropriate photograph facing the object. You may need to take the picture from a different angle to get the best view of the damage, e.g. along a hull to show how much the strakes have been set in. If you have been unfortunate enough to get images which are too dark or light all is not lost. Software is available to correct them, e.g. Photoshop, Paint Shop Pro. If you 105 REPORT WRITING FOR MARINE SURVEYORS brighten a dark photograph, don’t forget to increase the contrast to remove the misty appearance. The converse applies to brighter images. Because surveyors work in dirty and hazardous environments, accidents can often happen. It is therefore advisable to take spares with you, such as spare batteries and possibly a spare camera. Your spare camera need not be as elaborate as your main camera, but should be capable of taking reasonable shots. T he next problem is how to present the photographs in your printed report. The traditional method, until recently, has been to place the images in a photographic appendix after the main body of the report. If you are using this kind of presentation your photographs should have a gloss finish for clarity. In damage reports many references can be made to relevant photographs in the report text, e.g. ‘We found the anchor windlass base to be heavily corroded, wasted and torn at its connection to the foredeck (see Photographs 36, 37 & 38, page 38).’ T he reference in parentheses may also be in bold print for accentuation. You may also wish to add the page number to make it easier for the reader to find the photograph. A blank page with ‘Appendix 1 – Photographs’ should be inserted before the photographic appendix. Each of the photographic appendix pages should be of the continuation type, having a header and footer. Most surveyors include two photographs per A4 page; any more looks cramped. With two on a page it is possible to display them either in vertical (portrait) or horizontal (landscape) format, or a combination of the two. This looks far more professional. Each photograph will have a caption below or alongside to describe it. The traditional caption would be: Photograph 26 View of No. 2 port hatch cover panel after seals Note that the photograph number is underlined and there is a space between the two lines to give a well-spaced layout. Some surveyors prefer not to use the words ‘View o f ’. Landscape photographs should be centred on the page and spaced equally. Portrait photographs should be staggered, with the top photograph on the right and lower photograph on the left. Captions will be to the left of the top photograph and to the right of the lower photograph. Some software programs insert the printer’s trim marks to ensure that they are correctly positioned on the page. You may need to add rub on arrows to point out a damaged area in a photograph. T hese are available in different sizes, arrow designs and colours from stationary shops. If you have used arrows you should make reference to them: 106 Writing the report Photograph 26 View of No. 2 port hatch cover panel showing damage after seals (arrowed) With digital photographs the software may allow the user to add arrows or circles to emphasise particular areas of the picture. As with body text, photograph captions can be kept to a minimum number of words. Note the above caption. This can be further shortened: Photograph 26 View of damaged No. 2 port hatch cover panel after seals (arrowed) Photographic captions should also be accurate and unambiguous. Take this example: Photograph 26 View of port engine room T his implies that there could also be a starboard engine room. Perhaps it would have been better said: Photograph 26 View of engine room port side To show that the photographs are original and the report is an original report, some companies use their company stamp (or chop) on each photograph. The stamp is placed so that it is roughly half on the photograph and half on the page. In this way, the photograph cannot be replaced by another. With the advent of the internet and email, more clients are asking for their reports in electronic form. With some software packages it is possible to insert digital photographs into the photographic appendix within the document. Word processing documents in this form take up a lot of disk space and can be amended. For this reason they are usually converted to Adobe Acrobat portable document format (pdf) for transmission. This is a secure format which ensures that the document cannot be changed and arrives at the other end as it was intended. Some clients prefer the written report in pdf format with the photographs in a separate f ile and format. Microsoft Powerpoint and Apple Keypoint are software examples which are often used. When sending reports and photographs by email, the file size should not exceed 5 megabytes (Mb) as most internet service providers restrict file sizes. The average size per page of text sent in MS Word or Adobe Acrobat takes up about 10 kilobytes (kB). With larger file sizes it may be necessary to send the report and photos separately. A photograph is comprised of thousands of pixels, so a photograph occupies a lot of space within a file. The conflict for the surveyor is taking photographs of high quality 107 REPORT WRITING FOR MARINE SURVEYORS whilst still being able to send them by email. A fine quality photograph of 2560 x 1920 pixels will take up more than 1 Mb of space. An ‘economy’ quality photograph of 640 x 480 pixels will probably take up around 50 kB. If you take high quality photographs, but need to paste them into a Powerpoint document to send them by email, you will need to resize them to around 7 inches (17.8 cm) wide in landscape orientation. If you have a lot of photographs to resize you can use the ‘Actions’ option under the ‘Window’ menu to automate the process. T his will bring the size of each photo to around 50 kB. It is relatively easy to set up a template for photographs in Powerpoint, so that your photographic appendices are almost automated. Pasting photographs and adding the captions takes time. Compiling the photographic appendix is one of the most labour intensive tasks in marine surveying and report writing. Because it is so onerous, some surveyors leave the task until last. Once done, the report is complete and there is a sense of achievement. PageMaker, QuarkXPress and other similar software now allow desktop publishing where photographs and diagrams can be embedded in the document with the text wrapped around objects. The quality of a digital photograph printed on plain paper is not as good as a developed and glossy photograph. However, the print quality for colour printers is rapidly improving. If you are embedding photographs in your text, align the tops of the photographs with the x-height (the top of the lower case letters in a line of text) in the adjacent column. This helps the reader to view the photograph and easily return to reading the text. It also gives uniformity and a better layout quality. T he natural track for the eye when reading a document in English is from top left to bottom right. Layout experts therefore suggest that photographs should be located in the top right and bottom left corners so as not to disrupt the reading pattern. However, with marine surveying reports it is normal to keep a photograph to the right of the page and, where possible, immediately adjacent to the relevant text. With text wrapping, keep the text left aligned rather than justified. If you use justification you will get large areas of white space in your text so that it will not look uniform. Whilst the left aligned text may not butt up to your photographs, this layout is much tidier. 5.30 Accurate descriptions. As previously stated, miscommunication and ambiguity are the worst enemies of understanding. Inaccurate descriptions can be added to these two. The downfall of experienced and knowledgeable marine surveyors has been their inability to describe accurately what they have seen during their survey. Descriptions are usually required under the ‘survey findings’ section of your report. T hese may relate to pre-purchase condition surveys, damage surveys, etc. 108 Writing the report To be accurate you must avoid vague adjectives such as: • Slightly. • Fairly. • Moderately. • Heavily. • Severely. T hese are very subjective adjectives. To what extent is something slightly corroded? If you are going to use such an adjective you will need to specify exactly the extent intended by the word, e.g. slightly = less than 5% corrosion. Some P&I Clubs have found it useful to define such terms used in their reports: Good Satisfactory Fair Unsatisfactory Poor Condition better than average in all respects, original strength/ performance unimpaired, no maintenance or repairs required. Condition average, minor deficiencies not in need of correction, wear and tear evident, but original strength performance not significantly affected. Condition below average, deficiencies of some consequence and in need of correction in near future. Condition below average, deficiencies in need of immediate maintenance or repair. Condition deteriorated in all respects, beyond practical repair, requires renewal or replacement. By referring to the above definitions, the reader will understand the condition of the items being described. Some pleasure craft surveyors use the following terminology: Excellent Good Fair Poor Appears In new condition or like new. Nearly new with only minor cosmetic or structural faults. A system, component or piece of equipment is functional with only minor repairs necessary. Unusable as is. Needs repairs or replacement of the system component or piece of equipment. Indicates a very close inspection of the relevant area was not possible due to limitations placed on the surveyor, e.g. inaccessible panels, no lighting, etc. 109 REPORT WRITING FOR MARINE SURVEYORS Fit for intended use Fit for its intended purpose and use by the buyer. Serviceable Sufficient for a specific requirement. Powers up Poor Power was applied only. Does not refer to the operation of any system or equipment unless specifically indicated. Condition deteriorated in all respects, beyond practical repair, requires renewal or replacement. T he surveyor may find it difficult to describe something in only a few words but, with practice, he should be able to keep the number of words to a minimum. So often we see descriptions such as: ‘The cargo hold internals were found to be fairly corroded and wasted.’ What does the word ‘fairly’ mean in this context? T his should have been broken down into the different areas and described more accurately: ‘Fore and after bulkhead coatings were found generally intact but with small corrosion blisters appearing over approximately 10% of the surface area, mainly on the lower 4 m. Side shell and frame coatings were found to be breaking down with approximately 50% of the surfaces showing large corrosion blisters with sheet corrosion of the hopper plates. Tanktop coating non-existent. Heavily indented to a depth of 75 mm between double bottom internals over 90% of its area.’ T his is one occasion when more words are necessary to accurately describe the condition of the hold internals. In some cases there are standards set and defined in publications issued by industry bodies. One such publication is the American Rust Standard Guide – a Guide for Grading Hot Rolled Steel by Surface Condition. (For more information contact the American Institute of Steel Construction, One East Wacker Drive, Suite 3100, Chicago, IL 60601, Phone +1 312-670-2400, Fax +1 312-670-5403, Website: www. aisc.org.) T his easy to carry and use booklet has colour photographs against which the steel being surveyed can be compared. When reporting findings, the surveyor can quote the particular colour photograph which has an identifying code, e.g. A2, B1, etc. Some tanker companies also publish comparative standards for corrosion which their vetting inspectors must use. Percentages may be used to give an indication of the extent of corrosion but should be accompanied by the type of corrosion. The surveyor will need to be able to 110 Writing the report understand the corrosion process and the stages of coating breakdown. There are also different types of corrosion, e.g. • Blisters. • Sheet. • Flake. • Pitting. • Undercutting, etc. Dimensions should be used where possible to accurately describe the damage: ‘The port side shell plate was found set in approximately 1.5 m over an area of 2.5 m high x 3.5 m long approximately 2.5 m below the main deck between frames 46 and 50.’ Extensive damage is usually reported in the form of a table consisting of ‘Found’ and ‘Recommended’ This can be easily tabulated for readability. FOUND 1. The port sideshell plate was found set in approximately 1.5 m over an area of 2.5 m high x 3.5 m long approximately 2.5 m below the main deck between frames 46 and 50. 2. Port sideshell frames in way of frames 46 to 50 found heavily set in 1.5 m over a height of 2.5 m. etc. RECOMMENDED Crop and renew port side shell plating 2.5 m high x 3.5 m long approximately 2.5 m below the main deck between frames 46 and 50. Port sideshell frames in way of frames 46 to 50 to be cropped and renewed over a height of 3 m. Figure 19. Found and recommended table T he above table could be accompanied by a section of the vessel’s shell expansion plan showing the relevant damaged areas. 5.31 Use of spreadsheets T he information shown above in the ‘found and recommended table’ has been placed in a spreadsheet which has been pasted into this document. Spreadsheets are a useful tool in presenting complex information and calculations. For example, the ‘found and recommended’ information above could be included in a spreadsheet which also shows the steel weight calculations, as shown in Figure 20. T he calculated steelweight could then be multiplied by the shipyard’s steel repair rate per kilogramme to get the cost of steel repairs. However, added to this figure must be a percentage for small items, staging and contingencies to give a more realistic f inal figure. The estimate should always be approximately 20% over the estimated cost for merchant vessels, with 10% being standard for pleasure craft. All parties will 111 112 REPORT WRITING FOR MARINE SURVEYORS be satisfied if the final invoices come in lower than your estimate. Questions will be asked if they come in higher. If you believe that the client will have problems with reading the information along a line or in a column, it may be advisable to include the table lines. These need not be hard lines but could be dotted so that they are unobtrusive. Another example is the use of a spreadsheet for a pleasure craft tonnage calculation (in Hong Kong) shown in Figure 21. Item Details Rec’d No Height Depth Off Length mm Width mm Thickness mm Area m2 Weight kg Starboard side: Sheerstrake Set in/torn C&R 1 8500 1500 11 12.75 1,101.66 Sheerstrake Set in FIP 1 5100 150 11 0.77 66.10 Main Deck Set in/torn C&R 1 3500 400 7 1.40 76.98 Main Deck Set in C&R 1 4500 600 7 2.70 148.46 Handrails Heavily deformed C&R 1 21000 200 4 4.20 131.96 Handrails Deformed/ torn C&R 2 21000 80 4 1.68 105.57 Stanchions Set in / deformed C&R 8 1000 110 10 0.11 69.12 Stanchions Set in / deformed C&R 8 1000 200 10 0.20 125.68 Pipe rails Deformed C&R 2 1600 350 4 0.56 35.19 Frames Set in / deformed C&R 15 1500 420 8 0.63 593.84 No 2/3 bulkhead Set in / deformed C&R 1 1500 600 10 0.90 70.70 Deck beams Deformed C&R 1 8500 125 9 1.06 75.11 After main deck: Bulwark Set in / deformed C&R 1 600 900 8 0.54 33.93 Bulwark stays Set in / deformed C&R 2 1200 180 10 0.22 33.93 113 Writing the report Stag horns Torn away Renew 2 270 150 60 0.04 38.18 Bulwark flange Torn away Renew 1 1200 480 8 0.58 36.20 After bulkhead Deformed C&R 1 1950 700 8 1.37 85.78 Side shell Set in C&R 1 2000 2000 11 4.00 345.62 Stiffeners Deformed C&R 3 1950 150 10 0.29 68.93 Deck Deformed C&R 1 2000 500 10 1.00 78.55 Vent pipe Torn away Renew 1 1950 240 4 0.47 14.70 Vent pipe Torn away Renew 1 1950 280 4 0.55 17.16 After handrail Heavily deformed C&R 1 3450 150 4 0.52 16.26 Handrails Deformed C&R 2 3450 70 3 0.24 11.38 Stanchions Deformed C&R 5 1000 130 9 0.13 45.95 Total (kg) = 3,426.94 FIP = Fair in place. C&R = Crop and renew. Figure 20. Found and recommended table with steelweight calculations TONNAGE MEASUREMENT CALCULATIONS SI Units Item Length Breadth Depth Constant Total Volume Hull (V184) 21.36 5.75 1.85 0.50 113.61 Enclosed Spaces (V2) Volumes + Main Deck 21.36 5.75 2.13 261.61 Upper Deck 16.97 5.75 2.13 207.84. 537.99 Sun Deck 5.96 5.75 2 68.54 Constant K1 (=0.2 + 0.02 x Log10 V1) 0.241 Total = 651.60 GT = K1(V1 + V2) Gross Tonnage = 157.105 Figure 21. Tonnage measurement calculations 114 REPORT WRITING FOR MARINE SURVEYORS Spreadsheets can also be used to report bunker survey figures: Heavy Fuel Oil Date: 14-Feb-10 Time: 1600 hrs PORT: Nantong Trim 3.55 m By Stern HFO Tank Tank Sounding Volume in m3 Temp °C Density 15°C VCF ASTM (T/54B) Standard Volume WCF Weight MT FOT 1P 0.420 46.090 4 0.9880 1.0076 46.440 0.9869 45.832 FOT 1S 0.420 46.090 4 0.9880 1.0076 46.440 0.9869 45.832 FOT 2P 62.000 98.530 25 0.9880 0.9931 97.850 0.9869 96.568 FOT 2S 93.000 187.020 4 0.9880 1.0076 188.441 0.9869 185.973 FOT 3P Gauge 0.000 0.9880 1.0103 FOT 3S Gauge 0.000 0.9880 1.0103 Sett 1 Gauge 38.700 40.4 0.9880 0.9823 38.015 0.9869 37.517 Sett 2 Gauge 34.400 65.7 0.9880 0.9646 33.182 0.9869 32.748 Serv1 Gauge 20.600 55.8 0.9880 0.9716 20.015 0.9869 19.753 Serv 2 Gauge 37.200 88.8 0.9880 0.9484 35.280 0.9869 34.818 O/Flow 0.100 2.170 4 0.9880 1.0076 2.186 0.9869 2.158 Total 501.198 Less consumption from berth to Departure Pilot 6.378 TOTAL 494.820 Diesel Oil Date: 14-Feb-10 Time: 1600 hrs PORT: Nantong Trim 3.55 m By Stern MDO Tank Tank Sounding Volume in m3 Temp °C Density 15°C VCF ASTM Standard Volume WCF Weight MT DO Storage Gauge 56.500 20 0.8534 0.9959 56.268 0.8523 47.958 DO Service Gauge 22.400 20 0.8500 0.9959 22.308 0.8489 18.937 Total 66.895 Less consumption from berth to Departure Pilot 4.205 TOTAL 62.690 All calculations can be carried out in the spreadsheet before it is copied and pasted into the report. Writing the report 5.32 Notes T his is a section left at the end of the report for any special notes relating to the survey or the report. It is often advisable to have one clause relating to the issuing of the report, e.g. ‘This report is issued without prejudice. In our opinion, the report constitutes a statement of the condition of the vessel at the time that the survey was carried out.’ Other paragraphs may be included giving additional information, e.g. ‘As the vessel sailed at on , we were unable to complete our investigation.’ In the case of cargo surveys, there could be a specific paragraph relating to exceptions, e.g. ‘This report is issued without prejudice. In our opinion, the report constitutes a statement of the condition of the consignment at the time that the survey was carried out. ‘The Consignee’s representative issued no exceptions or comments relating to the discharge operations. No claim or exception has been received from the Consignee’s representative to date.’ In the case of a hull and machinery damage investigation: ‘As the vessel is awaiting the arrival of the new propeller, the sterntube was blanked off and the vessel was refloated on 11 February 2010. ‘The new propeller is expected to arrive at the shipyard on or about 15 March 2010. ‘This report is issued without prejudice. in our opinion, the report constitutes a statement of the condition of the vessel and her machinery at the time that the survey was carried out.’ T his is also the location for adding information on any additional documents which have been attached to the report, e.g. ‘We have received the following documents which are appended to this report: • Master’s statement of facts (2). • Ship’s particulars. • Crew list. • List of surveys and certificate status. • DnV Certificate for propeller. • Propeller manufacturer’s certificate and information. 115 REPORT WRITING FOR MARINE SURVEYORS • Propeller marking rubbing. • Details of taper. • DnV and owner’s communications relating to approval of the propeller. • Mitsubishi original propeller drawings. It may be noticed that some of the above exceptions may already be included in the terms and conditions of survey stated at the beginning of the report. If so, they would not be duplicated at the end of the report. 5.33 Appendices and annexes An annex should be used where information (which would normally make sense in the main body of the document) is placed at the end of the document for reasons of clarity. An appendix is a document to be used to supplement the main text. If the annex/appendix can be read in its own right as a stand-alone document, then it is classed as an appendix, if not, then it is classed as an annex. A supplementary report to a previous report may be considered to be an annex to that report. An appendix is a collection of supplementary material appended at the back of a report. It may also be a collection of supplementary material added to a report. It is usually related to the material in the main part of the report, but not so closely related to it that it should be put into the main text. Appendices may also include background information and supporting facts. T he appendix is also the location for additional documents requested by the client which can be any item not able to be included in the body text. T he first appendix usually contains the photographs. Each appendix is preceded by a plain page with the appendix number and title centred vertically and horizontally. It is not necessary for this page to be numbered or have the continuation page header, e.g. APPENDIX 1 Photographs T he labelling system for appendices may vary. Some companies use capital letters. If you are including a computer-generated table of contents in your report you will need to add a number of blank pages after the title page to allow for the pages to be included in the appropriate appendix. These can be removed later when printing out the report. 5.34 Binding the report Bound reports are less popular these days as most clients prefer to receive their reports by email as this saves a lot of time, paper and money. However, should your 116 Writing the report client wish to receive a bound copy it is necessary for you to ensure that the bound report has a hard front and rear cover, preferably with a 0.3 mm thickness clear plastic cover front and back to protect the cardboard cover. Printing companies usually have a selection of thin cardboard in various colours and textures which you can consider for your report covers. They will usually emboss your company name and logo in gold or silver print onto the cardboard for a fee. Ring bound or spiral bound reports are more durable than the glued clip bound reports. It is also advisable to have a binding system which allows the replacement, or addition, of extra pages. Some errors may be found after it has been bound. Done properly, a bound report looks more professional. There is also a lot of satisfaction in seeing your final product bound and ready for delivery. 5.35 Touch typing T he keyboard of a computer is the interface between the user and the computer. Being familiar and comfortable with it is critical in using a computer to its maximum potential. Touch typing is the key to speed and accuracy, and a step towards optimising time management. T he keyboard is based on the QWERTY system, i.e. the six top left keys on the keyboard. The keyboard layout made its first appearance on a rickety, clumsy device marketed as the ‘Type-Writer’ in 1872 built by C L Sholes. The keys were arranged in this way to prevent the type bars from clashing with each other when typing combinations which were close together. For many years, the traditional way of preparing a report for a client was to hand write the report and pass it to a secretary for typing. This often ensured the accuracy of the report with quality of writing, grammar and spelling. This was followed later by the surveyor using a Dictaphone, which the touch typist would then type out. Both methods required a certain amount of correction such that a report would be passed back and forth several times with red ink being prevalent. In some larger companies, where secretaries were shared between surveyors, it could take days to get back the typed document from the typing pool and, again, waiting for the corrections, due mainly to the number of surveyors and a shortage of copy/dictaphone typists. It was only with the advent of computers that people started to take an interest in learning to touch type. Those who were frustrated by the delay in getting typing done decided to learn using a touch typing text book and electric typewriter. T he lessons start by teaching you the home keys on the QWERTY keyboard. The home keys, on the middle row of letters, are ASDF and JKL; . You start very slowly on these keys, making sure that you are accurate rather than fast. Three letter sequences are used to familiarise the student with the keys such as AAA, SSS, DDD, FFF, then 117 REPORT WRITING FOR MARINE SURVEYORS ASA, SAS, ADA, DAD, FAF, AFA, etc. Once competent on these keys, you progress to the upper and lower keys, then the numbers. It is the conscious process of looking at a letter on a piece of paper, your eye seeing it, brain registering it, then instructing the appropriate finger to hit the key which controls the speed at which you type. Eventually, when you have mastered all the letter keys, with practice you can build up accuracy and speed. Eventually, one day you will sit down to copy type a couple of paragraphs, placing your hands on the home keys and going for it, without realising that the conscious process mentioned above has gone completely. Some may be able to type fast with four fingers, but they don’t get to look at what they are typing on the screen. Four-finger typists will never have the speed and accuracy, needing endless corrections. Some surveyors just hit the ‘Caps Lock’ key and type away to their hearts’ content, choosing to ignore syntax, particularly if they employ non-native English speakers/writers. You can always tell when a document has been typed by a two fingered typist. The number of spaces after a full stop (period) vary from one to three! Sentences may also start with lower case letters. Accuracy, quality of writing, grammar and spelling are essential in a report. It takes a lot of skill to be able to transfer your report straight on to a piece of paper or computer screen, but the computer allows you to cut and paste to get the right results. Not having to think about which keys you are hitting, allows you to concentrate on content and syntax. Grammar will always be a problem, whether you can type or not, but be warned, your handwriting will deteriorate as a consequence of using the keyboard more! If you are thinking of learning how to touch type you should take a week off work to do it. It is no good trying to learn part-time and then go back to the computer at work and use four fingers again. You have to do it ‘cold turkey’. Many companies offer crash courses for those who want to learn quickly. The key is not to lose heart, be patient and stick with it. You’ll be pleased you did in the end. 118 Appendices Appendices T he specimen report formats hereunder have been used by the author over many years, having been readily accepted by clients. They are intended only as guidelines for the reader who may reproduce and modify these formats as required. Some sections have been abbreviated to prevent repetition. 119 This page intentionally left blank 120 Appendix 1: Specimen Pre-purchase Condition Survey Reports 121 This page intentionally left blank 122 Specimen Pre-purchase Condition Survey Report for a Merchant Vessel 123 This page intentionally left blank 124 XXX Marine Consultants Ltd Marine Consultancy • Hull, Machinery and Cargo Surveying Tel: Fax: Mobile: Email: Your Ref : Our Ref Date : XMC*** : Survey Directors: Name, degrees, membership of professional organisations, etc. 125 126 TABLE OF CONTENTS 1. Vessel particulars ...............................................................................................................................1 2. Parties attending the survey ............................................................................................................2 3. Survey findings ..................................................................................................................................2 4. Notes ...................................................................................................................................................2 Documentation ......................................................................................................................................4 Certificates ...............................................................................................................................................4 Other information .................................................................................................................................5 Port State Control ..................................................................................................................................5 Conditions of Class ...............................................................................................................................5 Review of thickness gauging report ....................................................................................................5 Review of deck and ER log books .......................................................................................................6 Last 15 ports of call ................................................................................................................................6 Vessel performance ................................................................................................................................6 Fuel consumptions ................................................................................................................................7 Safe manning certificate ........................................................................................................................7 Essential documents ..............................................................................................................................8 Loadline details ......................................................................................................................................8 Cargo capacities .................................................................................9 Cargo capacities ..............................................................................................................9 Lashing gear inventory ........................................................................................................................10 Hatch dimensions ................................................................................................................................10 Ballast capacities ...................................................................................................................................11 Tank capacities ......................................................................................................................................11 Condition of hull ..................................................................................................................................12 General arrangement of holds and tanks.........................................................................................13 General cargo vessels: Hatch covers .......................................................................................................................................14 Holds....................................................................................................................................................14 Cargo / stores handling machinery and mooring equipment ..................................................15 Bulk carriers: Hatch covers .......................................................................................................................................15 Holds....................................................................................................................................................15 Cargo / stores handling machinery and mooring equipment ..................................................16 Engine room and machinery .............................................................................................................17 Main engine ...........................................................................................................................................18 127 Generators .............................................................................................................................................19 Steam plant ............................................................................................................................................20 Major spare parts ..................................................................................................................................20 Navigation .............................................................................................................................................20 Communications .................................................................................................................................21 General condition of vessel ................................................................................................................22 Fire fighting equipment and life saving appliances .......................................................................22 Items included in the sale ...................................................................................................................23 Items not included in the sale ............................................................................................................23 Overall assessment ...............................................................................................................................23 General remarks. ..................................................................................................................................24 List of defects noted ............................................................................................................................24 XXX Marine Consultants Ltd Marine Consultancy • Hull, Machinery and Cargo Surveying Tel: Fax: Mobile: Email: Your Ref : Our Ref Date : XMC*** : Survey IN ACCORDANCE with instructions received from , our Surveyor attended on board whilst alongside at , on , for the purpose of carrying out a . 1. Vessel particulars is an all steel, single screw, bulk carrier, having seven cargo holds with ten hatch covers, the accommodation and engine room being abaft . Name: Type: Registered: IMO No: Call sign: Owner: Operator: Class: Built: GRT: NRT: Deadweight: LOA: LBP: Dmould: Draft: Bmould: Main engine: Speed: T he vessel has hatch covers with no cargo gear on board. There are stores derricks aft of the accommodation. 128 XXX MARINE CONSULTANTS LTD -2 XMC**** 2. Parties attending the survey Attending during our survey were: Captain Master of the vessel. CONTINUATION VESSEL NAME Technical Superintendent, , representing . T he Undersigned Appointed on behalf of prospective buyers of the vessel. No other surveyors attended on board during the inspection. However, the Master or Chief Officer was present during most stages of the survey. We were informed that other surveys had been carried out previously at . 3. Survey findings Descriptions In order to achieve consistency of reporting, the following descriptions are to be used: Good Condition better than average in all respects, original strength/ performance unimpaired, no maintenance or repairs required. Satisfactory Fair Unsatisfactory Poor 4. Notes Condition average, minor deficiencies not in need of correction, wear and tear evident, but original strength/performance not significantly affected. Condition below average, deficiencies of some consequence and in need of correction in near future. Condition below average, deficiencies in need of immediate maintenance or repair. Condition deteriorated in all respects, beyond practical repair, requires renewal or replacement. We have received copies of: • which are appended to this report. It is to be clearly understood that the condition/state of items hereafter reported upon are strictly the opinion of the undersigned and that opinion reflects the condition/state found on this date , taking into consideration the vessel’s age and that items reported upon are described in comparison with vessels of similar age and type. T his survey is a factual report on the inspection carried out, and the opinions expressed are given in good faith as to the condition of the vessel as seen at the time of the survey. It implies no guarantee, no safeguard against latent defects, subsequent defects, or defects not discovered at the time of the survey in woodwork or areas of the vessel which are covered, unexposed, or not accessible to the surveyor internally due to the installation of non 129 XXX MARINE CONSULTANTS LTD -3 XMC**** CONTINUATION VESSEL NAME removable linings, panels and internal structures, etc., or agreement and permission and instructions not being given to the surveyor to gain access to closed off areas. Attending Surveyor for and on behalf of, XXX Marine Consultants Ltd 130 131 Condition Survey Report on Documentation The vessel’s documentation was generally found to be well organised and easy to access. Certificates Certificate Place & date of issue Date of expiry Certificate of registry Safety construction certificate Safety equipment certificate Safety radiotelegraphy certificate International loadline certificate Annual loadline survey Fire fighting appliance certificate Liferaft certificate Hull special survey Hull annual survey Machinery special survey Machinery annual survey Boiler survey Drydock survey Cargo gear survey quadrennial Cargo gear survey annual Loading and stability information United States water pollution certificate Oil record book IOPP IAPP ISPP US Coast Guard letter of compliance No: Port State Control inspection Flag State inspection ISM DOC ISM SMC ISPS XXX MARINE CONSULTANTS LTD CONTINUATION-4-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -5 XMC**** Other information Continuous Synopsis Report issued by ILO crew compliance issued Garbage certificate issued at Vessel entered with <P&I Club> CONTINUATION VESSEL NAME Vessel has been/not been fitted with emergency towing facility fore and aft Vessel has been/not been fitted with safe access to forward areas Vessel is/is not equipped for running unmanned engine room Port State Control Date of last inspection Place of inspection Number of deficiencies Number of outstanding deficiencies Conditions of Class (COC) A review of the vessel’s last quarterly report revealed no conditions of Class or outstanding CSM items A review of the vessel’s last quarterly report revealed the following conditions of Class: • Review of thickness gauging report We sighted a thickness gauging report issued on at by . We reviewed the report and maximum mean diminutions are recorded below. Item % maximum mean diminution Remarks Decks 11.4 Generally in single figures Transverse belts Sideshell (W&W) Hold frames Transverse bulkheads Bulkheads in TSTs Web frames WT floors Solid floors Forepeak 132 133 Review of deck and ER logbooks A brief inspection of the deck and ER logbooks revealed: 1. Last 15 ports of call Ports of call Port Arrived Departed Cargo Vessel performance Amount Units Loaded passage Speed (originally) knots RPM Slip % Fuel consumption mt/day Cylinder oil consumption litres/day Crankcase oil consumption litres/day Generator oil consumption litres/day Generator diesel consumption mt/day Ballast passage Speed knots RPM Slip % Fuel consumption mt/day TPC at loadline T/cm Service speed knots Economical speed knots XXX MARINE CONSULTANTS LTD CONTINUATION-6-XMC**** VESSEL NAME 134 FW evaporator mt/day Fuel consumption port Boiler (fuel type) mt/day Auxiliary engines (fuel type) mt/day Normal operation on cSt Vessel manoeuvring on Fuel consumptions We were informed by the Master that the vessel had the following fuel consumptions: 13 knots mt/day 14 knots mt/day 15 knots mt/day 16 knots mt/day 17 knots mt/day Safe manning certificate Administration: Required Actual Nationality Master Master Chief Officer Chief Officer Nav. Officer 2nd Officer Nav. Officer 3rd Officer Chief Engineer Chief Engineer 2nd Engineer Bosun AB (x3) AB (x3) OS (x2) Oiler (x2) Oiler (x1) Cook Total 13 Total 8 XXX MARINE CONSULTANTS LTD CONTINUATION-7-XMC**** VESSEL NAME 135 Essential documents Stability book Sighted in order. Duly endorsed Loading computer Sighted in order. Class approved Sea trial results Not available on board Finished plans and instruction books Sighted in order Oil record book Sighted in order Sounding book Sighted in order. Soundings taken every morning Safety equipment training manual Sighted in order in messroom and on bridge Shipboard oil pollution emergency plan Sighted in order Ballast water management plan IMO 868 (20) Sighted in order Last notice to mariners No 41/09 Light list and radio signals Sighted in order. Duly corrected Loadline details No information received on loadlines. Registered tonnage: Summer deadweight 12,854 mt Gross 10,396 Net 5,417 Lightship weight 6,009.6 mt Suez Canal tonnage: Gross 10,396 Net 5,417 Panama Canal tonnage: Gross 10,662 Net 8,108.45 We sighted • The ship’s plans. • Capacity plan. • Midship sections. • Class approved container stowage plan. Mark Freeboard (m) Draft (m) Disp’t (kT) DWT (kT) Tropical fresh Not given Not given Not given Not given Fresh Tropical Summer Winter Winter NA We were unable to sight any of the ship’s plans and were not provided with the vessel’s capacity plan or Class-approved container stowage plan. XXX MARINE CONSULTANTS LTD CONTINUATION-8-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -9 XMC**** Cargo capacities Hold capacity (m3) No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 Totals Grain CONTINUATION VESSEL NAME Bale Maximum allowable loads: On deck Tweendecks Lower hold Cargo capacities T hree cargo holds, No. 2 hold fitted with portable cell guides. Total container capacity: 923 TEU Container capacities: 40 ft = 45 ft 48 ft = = Reefers = = 417 + 89 246 112 28 in hold 2, bays 11 and 13 176 on deck, all bays except bays 1, 3, 15, 17 and 19 Maximum allowable loads: Holds 20 ft = 100 mt, 40 ft = 140 mt Deck 20 ft = 55 mt, 40 ft = 90 mt Hazardous cargo permitted as per certificate of compliance for the carriage of dangerous goods. We were not provided with any information on cargo tonnages or dimensions for each hold. 136 137 Lashing gear inventory LASHING MATERIALS INVENTORY - As at June 2010 Item As per manual Serviceable Damaged Remarks Deck lashings Twistlocks CV-9G/200G 12 9 Bottom twistlocks CV-9G 280 323 127 Dual function twistlock T 2.3-C 1048 988 117 Midlock stacker ML-2 1148 1467 6 Turnbuckles TBS-3G/1, TB3A 560 636 53 Lashing bars LB-11, LR1/S 560 636 53 Bridge fittings H-3-SR 0 37 17 Not part of lashing system Linking plates LP-G 0 Not part of lashing system Hold lashings Compensation stacker S-1.91-6 28 20 Lockable stacking S1.47, cones K-1 396 346 Antirack spacer 0 30 Tools Handling tools B-88 28 21 Operating rod OR-5 14 9 Spanner SW-55 14 10 Fixed securing devices in hold Part of ship spare parts store Fixed securing devices on deck Part of ship spare parts store Hatch dimensions Hatch openings Length m Breadth m No. 1 No. 2 No. 3 No. 4 No. 5 XXX MARINE CONSULTANTS LTD CONTINUATION-10-XMC**** VESSEL NAME 138 Ballast capacities Ballast capacity (m3) Port Centre Starboard Forepeak No. 1 DB P&S No. 2 DB P&S No. 3 DB P&S No. 4 DB P&S No. 5 DB P&S No. 1 TST P&S No. 2 TST P&S No. 3 TST P&S No. 4 TST P&S No. 5 TST P&S Afterpeak Totals All tanks The vessel has ballast pumps of m³ / hour total capacity. Tank capacities Item (m3) Port Centre Starboard Fuel oil tanks No. 2 DB C No. 3 DB C No. 4 DB C No. 5 DB C Total fuel oil MDO DO Tank P DO Tank S Total MDO Fresh water No. 1 P&S (boiler water) No. 2 P&S Total fresh water XXX MARINE CONSULTANTS LTD CONTINUATION-11-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -12 XMC**** Condition of hull External shell plating: CONTINUATION VESSEL NAME Survey afloat or in drydock? Condition of hull coatings? Any indentations? Decks - main deck; forecastle; poop: , Superstructure: Internal shell plating, bulk heads, frames: Ballast tanks, peak tanks, coffer dams: Mooring equipment - anchors, cables, mooring ropes, fairleads: WT openings - doors, ports, skylights: Ventilators, pipes, sounding pipes and closing devices: Deck lighting: Manifold, bunker tank vent and sounding pipe savealls: MARPOL equipment: 139 XXX MARINE CONSULTANTS LTD -13 XMC**** General arrangement of holds and tanks CONTINUATION VESSEL NAME Figure 1. Diagram showing arrangement of tanks and holds All double bottom tanks are separate from wing ballast tanks. 140 141 GENERAL CARGO VESSELS Hatch covers STEEL HATCH COVERS Type and number: Type and number of hatch covers, e.g. F&A folding hydraulically operated. Wire operated single pull, etc. Method of opening/closing: Condition of covers: Coaming compression bars: Sealing rubbers: Cross-joint drain channels: Coaming channels and drains: Securing devices for sea: Hold access hatches: Test for watertightness: Spares: Hatch covers container fitted?: Or TARPAULIN HATCH COVERS Covers designed for use with tarpaulins?: Means of removing covers: Number and condition of tarpaulins per hatch: Side/end batten bars: Wedges: Locking bars: Hold access hatches: Spares: Holds Number of holds: Coatings: Ladders: Guardrails: Spar ceiling: Tanktops: Manholes, covers: Bilges and suctions: Air and sounding pipes: Tweendeck hatch covers: Lighting: Ventilation type: Ventilation operational: Smothering distribution system: XXX MARINE CONSULTANTS LTD CONTINUATION-14-XMC**** VESSEL NAME 142 Cargo / stores handling machinery and mooring equipment Cranes or derricks: Number: Type: SWL: Operational: Cargo blocks: Wires: Winches/machinery: Controls: Entries made in register: Spares: Safety / operation markings: Crane wire renewal dates: Spreaders: Make, type, capacity, location? Windlass: Make, type, capacity, location? Mooring winches: Make, type, capacity, location? No. 1 crane: No. 2 crane: No. 3 crane: No. 4 crane: No. 5 crane: BULK CARRIERS HATCH COVERS Type and number: Two panel, side-sliding, chain or rack / pinion operated? Method of opening/closing: Condition of covers: Coaming compression bars: Sealing rubbers: Cross-joint drain channels: Coaming channels and drains: Securing devices for sea: Hold access hatches: Spares: HOLDS Number of holds: Last shipboard check for structural strength: Coatings: Ladders: Guardrails: XXX MARINE CONSULTANTS LTD CONTINUATION-15-XMC**** VESSEL NAME 143 Tanktops: Manholes, covers: Bilges and suctions: Air and sounding pipes: Tweendeck hatch covers: Lighting: Ventilation type: Ventilation operational: Smothering distribution system: Cargo / stores handling machinery and mooring equipment Cranes or derricks: Number: Type: SWL: Operational: Cargo blocks: Wires: Winches / machinery: Controls: Entries made in register: Spares: Safety/operation markings: Crane wire renewal dates: Spreaders: Make, type, capacity, location? Windlass: Make, type, capacity, location? Mooring winches: Make, type, capacity, location? No. 1 crane: No. 2 crane: No. 3 crane: No. 4 crane: No. 5 crane: XXX MARINE CONSULTANTS LTD CONTINUATION-16-XMC**** VESSEL NAME 144 Engine room and machinery Main engine: Make, type: Running hours Hours since last overhaul: Spares: Crankshaft deflections: Sterntube clearances: Last lube oil sample: Exhaust temps: Boiler: Make, type: Separate oil fired and exhaust or composite? Auxiliary boiler: Oil fired or electrically heated water? Auxiliary machinery: Make, type: Standard pump/motor design readily available? Generators: Number of generators, make and model: kW, Hz, Volts. Total hours: No. 1 - No. 2 - No. 3 Purifiers: How many, type, e.g. FO, LO, DO. Leaks, bilges full of oil? Switchboard: Any earth leaks noted? Domestic refrigeration machinery: Operational? Workshops: Equipped with tools, lathe, etc? Spares: New? Protected? Adequate? Tools: Adequate? Tool boards? UMS: Yes or no. Control room alarms and instrumentation: Any cards pulled? All operational? Fire detection system: Smoke, heat or flame? Smothering system: closing devices: CO2 , foam? Tested? Remote stops: Tested? In external good order? Oil / water separator: Make, type: Overboard discharge alarm: Fitted? Tested? Sanitation system: Toilets working? Sea valves: In external good order? Bilge system: Clean, dry, alarmed? Shaft tunnel / stern gland: Corroded, leaking? Emergency escape: Any fitted, clear and bright? Fire-resisting doors: Any fitted Fire/pollution hazards: Oil in bilges and on surfaces, rags around ER? Steering gear and emergency system: Make, type: Tested? Emergency generator: Make, type: Tested? Load applied? Emergency fire pump: Make, type: Tested? Crane/hoist - SWL: Make, type: Sterntube clearances, leaks, samples: Last drydock report readings XXX MARINE CONSULTANTS LTD CONTINUATION-17-XMC**** VESSEL NAME 145 Main engine Design: Make: Type: Engine number: Number of cylinders: Bore: Stroke: Turbo chargers: MCR / RPM: CSR / RPM: Barred speed range: Bridge or ER controlled: Gearbox Make: Type: Reduction: Coupling: Propeller Make: Type: Rotation: Number of blades: Diameter: Pitch: Material: Weight: Rudder Type: Stern gland Make: Type: Steering gear Make: Type: Torque: Bow thruster Make: Type: Capacity: XXX MARINE CONSULTANTS LTD CONTINUATION-18-XMC**** VESSEL NAME 146 Generators (Should all be run, paralleled on switchboard and load distributed. Reverse power and preference trips should also be tested) Number of sets: Make: Type: Number of cylinders: Bore: Stroke: Turbo charger: BHP: RPM: Main alternators Make: Type: Output: Volts: Hertz: Cooling system: Shaft alternator Drive system: Make: Type: Output: Volts: Hertz: Cooling system: Emergency generator engine Make: Type: Number of cylinders: Emergency alternator Make: Type: Output: Fuel viscosity: Load at sea: Load in port: Auxiliary engines on load: XXX MARINE CONSULTANTS LTD CONTINUATION-19-XMC**** VESSEL NAME 147 Steam plant Auxiliary oil fired boiler Number of sets: Make: Type: Maximum evaporation rate: Number of burners: Working pressure: Consumption: Waste heat boiler Make: Type: Maximum evaporation rate: Working pressure: Major spare parts Tailshaft: Propeller: Anchor: Main engine: Cylinder covers: Cylinder cover inserts: Main engine cylinder liners: Piston and rod assembly: Piston head: Exhaust valves complete: Bottom end bearing: Set thrust pads: Main bearing: Cross head pin: Cross head bearings: Navigation One-man bridge operation: Gyro compass: Make, type: Operational? Bearing repeaters/azimuth rings: How many: Autopilot: Make, type: Operational? Course recorder: Make, type: Operational? Standard (magnetic) compass: Date of deviation curve: Radars: Make, type: Operational? ARPA: Make, type: Operational? XXX MARINE CONSULTANTS LTD CONTINUATION-20-XMC**** VESSEL NAME 148 Chronometers: Make, type: Operational? GPS: Make, type: Operational? Depth sounder, recorder or indicator?: Make, type: Operational? Log/speed indicator: Make, type: Operational? Rudder indicator: Number: Bridge wings? Revolution indicator: Number: Bridge wings? Navigation and signal lights: Operational? Alarm tested? Chart outfit: Coverage? Chart correction method? Navtex receiver: Make, type: Operational? Weather facsimile receiver: Make, type: Operational? Pilot books and supplements: Up to date? Guide to port entry: Current edition? Nautical almanac: Current edition? Tide tables: Current editions? List of lights: As above RPM / speed data: Posted? Manoeuvring data: Posted? Daylight signalling lamp: Make, type: Operational? Sextants and binoculars: How many? Bridge windows: Clean, clear, degree of vision? Communications GMDSS system: Make, type: Operational? Main Tx/Rx: Facsimile Tx/Rx: Emergency Tx/Rx: Emergency watch receiver: Auto alarm 500 kHz: VHF radio telephone: EPIRB: SARTS: SOLAS VHF radios: How many: Charged? Emergency batteries: Lists of radio signals: Emergency instructions at station: Radio log: XXX MARINE CONSULTANTS LTD CONTINUATION-21-XMC**** VESSEL NAME 149 General condition of vessel Accommodation: Master’s office: Chief Engineer’s office: Ship’s plans: Air conditioning: Messrooms: Sanitary system: Showers: For how many crew? Carpets? En-suite toilets? Computer, printer, records? Computer, printer, records? Clean, tidy and in good condition? Operational? Separate for crew & officers? Toilets operational? Operational? Galleys and storerooms: Utensils: Exhaust fans: Incinerator: Range: Cold rooms: Clean and tidy? Infestation? Sufficient? Operational? Fitted and used? Type? Weather bars fitted? Temperatures? Lock in alarms? Deck and ER storerooms: Spares and consumables? Clean and tidy? Well organised? Inventory? Hospital: No of beds? Stretcher? Dispensary and medical: Inventory up to date? Oxygen resuscitator: Available? No. of spare bottles? Accommodation ladders: Type? Safe? Pilot ladders: Type? Location? Pilot hoist: Fitted? Fire fighting equipment and life saving appliances Lifeboats: Number: Type: Equipment: Fittings: Launching equipment: Liferafts: Number and location: Hydrostatic releases: Lifebuoys: Lifejackets: Number: IMO type-approved? Immersion suits: Number: Stowage location: Thermal protective aids: How many: Location: Fixed FFE deck: Type: Areas covered: No. of bottles: Fixed fire detection: Type: Areas covered: Fire lines and hydrants: Fire pumps: Type: No: Capacity: Emergency fire pump: Location: Type: No: Capacity: International shore connection: Location: No: Fire hoses and nozzles: XXX MARINE CONSULTANTS LTD CONTINUATION-22-XMC**** VESSEL NAME 150 Fire extinguishers: Types: Recently inspected? SCBA: No. provided: Spare bottles? Portable oxygen meters: Bridge pyrotechnics: Line throwing appliance: Lifeboat pyrotechnics: Emergency station bills: Fire control plan: Internal: External: Escape signs: Items included in the sale We were informed by the Master of that the following items are to be included in the sale. Items not included in the sale We were informed by the Master of that the following items are not to be included in the sale. Overall assessment Remarks 1. Shell plating 2. Holds 3. Weather decks and fittings 4. Superstructure 5. Mooring equipment 6. Hatch covers 7. Ballast tanks 8. Main machinery 9. Auxiliary machinery 10. Engine room 11. Stores and spares 12. Steering gear 13. Cargo gear 14. Safety equipment 15. Firefighting equipment 16. Navigation equipment 17. Documentation Average: Total: Scoring: 1 = extremely poor. 9 = excellent. Maximum score = 153. Overall scoring: 18 = extremely poor. 153 = excellent. Average = 76. XXX MARINE CONSULTANTS LTD CONTINUATION-23-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -24 XMC**** General remarks CONTINUATION VESSEL NAME Place and date of survey. During cargo operations? In ballast? Brief history of vessel. How long under current owner/manager? Vessel’s suitability for cargo? Will she pass scrutiny for carriage of higher value cargoes? Any special features? Buyer will need to know how much money he will have to spend on the ship. Steelwork renewals required in tonnes and US$. Equipment which may need replacement / repair. When is next special survey due? How much work is required? Maintenance records available indicating good upkeep? In the opinion of the undersigned, taking into consideration the age of the vessel and trade routes / cargoes carried, this vessel is considered to be in good, satisfactory, poor or unsatisfactory condition at this time, , considering normal wear and tear and subject to comments as contained herein. Date and place of survey: Survey no: By: For and on behalf of: XXX Marine Consultants Ltd List of defects noted 1. END 151 This page intentionally left blank 152 Specimen Pre-purchase Condition Survey Report for a Pleasure Craft 153 This page intentionally left blank 154 XXX Marine Consultants Ltd Marine Consultancy • Hull, Machinery and Cargo Surveying Tel: Fax: Mobile: Email: Your Ref : Our Ref Date : XMC*** : Pleasure Craft Pre-Purchase Condition Survey Directors: Name, degrees, membership of professional organisations, etc. 155 XXX Marine Consultants Ltd Marine Consultancy • Hull, Machinery and Cargo Surveying Tel: Fax: Mobile: Email: Your Ref : Our Ref Date : XMC*** : Pleasure Craft Pre-Purchase Condition Survey IN ACCORDANCE with instructions received from , our Surveyor attended on board on , whilst on the slipway at and during short sea trials, for the purpose of carrying out a pre-purchase condition survey. 1. Vessel particulars is a GRP, single screw, motor yacht. Name: Type: Registered: HK ID No: Licensed for: Class: Call sign: Owner: Built: LOA: Bmould: Engine(s): Speed: T he above information was obtained from the vessel’s registration documents/ manufacturers’ specifications, etc. 2. Parties attending the survey: Usual format. 156 CONTINUATION XXX MARINE CONSULTANTS LTD XMC**** 3. General arrangement Figure 1. General arrangement of main deck-2 VESSEL NAME Figure 2. General arrangement of lower deck 157 XXX MARINE CONSULTANTS LTD -3 XMC**** 4. Descriptions CONTINUATION VESSEL NAME In order to achieve consistency of reporting, the following descriptions are to be used: Good Condition better than average in all respects, original strength/ performance unimpaired, no maintenance or repairs required. Satisfactory Fair Unsatisfactory Poor 5. Notes Condition average, minor deficiencies not in need of correction, wear and tear evident, but original strength/performance not significantly affected. Condition below average, deficiencies of some consequence and in need of correction in near future. Condition below average, deficiencies in need of immediate maintenance or repair. Condition deteriorated in all respects, beyond practical repair, requires renewal or replacement. It is to be clearly understood that the condition/state of items hereafter reported upon are strictly the opinion of the undersigned and that opinion reflects the condition/state found on this , taking into consideration the vessel’s age and that items reported upon are described in comparison with vessels of similar age and type. T his report has been prepared specifically for , on , and is for his use only but remains the copyright of XXX Marine Consultants Ltd (XMC). Copies in whole or in part should not be released to, or consulted by, other parties without the express prior permission of XMC. Whilst all due care and diligence has been exercised in the collection of data for, and the preparation of, this report, XMC purports to provide an advisory service only, based on the opinion and experience of the individual consultant responsible for its compilation. XMC issues such advice in good faith and without prejudice or guarantee. Anyone wishing to rely on such opinion should first satisfy themselves as to its accuracy and feasibility. XMC shall not be liable for any loss (including indirect and consequential loss), damage, delay, and loss of market, costs, expenses of whatsoever nature or kind and however sustained or occasioned. Notwithstanding the aforementioned, notice of a claim or suit must be made to XMC in writing within 90 days of the date the services were first performed or the date the damages were first discovered, whichever is the later, failing which lack of notice shall constitute an absolute bar to the claim or suit against XMC. T his survey is a factual report on the inspection carried out, and the opinions expressed are given in good faith as to the condition of the vessel as seen at the time of the survey. It implies no guarantee, no safeguard against latent defects, subsequent defects, or defects not discovered at the time of the survey in woodwork or areas of the vessel which are covered, unexposed, or not accessible to the surveyor internally due to the installation of non-removable linings, panels and internal structures, etc. This is a visual survey only, being non-invasive and non-destructive. XMC accepts no responsibility or liability in relation to any part of the vessel which cannot be accessed or viewed. Parts of the vessel were not 158 XXX MARINE CONSULTANTS LTD -4 XMC**** CONTINUATION VESSEL NAME accessed or viewed and therefore we cannot comment on this in relation to any patent or latent damage, including termite or other insect infestation. T his report carries no warranty regarding ownership of the vessel or any warranty regarding outstanding mortgage, charge or other debt there may be on the vessel. This survey is personal and confidential to our client and has no extended warranty if disposed of to a third party for any purpose without the permission of XMC. T his report does not address stability, vessel performance or overall design, and no warranty is conveyed under these headings. Machinery was not opened up for inspection or compression tests carried out. No chemical tests were carried out on fuel or water. Whilst we did not sight any pest infestation during the inspection, we recommend that a pest control expert be appointed to assess whether termites or cockroaches are present. Liability is limited to five times the surveyor’s fees for the inspection of this vessel. T hese standard trading terms, all agreements and disputes relating thereto, shall be governed by and interpreted in accordance with law. Please note that copyright remains with XMC. No part of our report may be disseminated until such time as our invoice is paid in full. Attending Surveyor For and on behalf of, XXX Marine Consultants Ltd 159 160 MAIN DECK Layout: (See Figure 1) Deck materials: Guardrails, stanchions, cap rails, boarding gates: Cleats, bitts, windlass and anchors: Scuppers, freeing ports: Chain locker, anchor mounting: Bow, pulpit: Water and fuel filling arrangements: Doors: Lockers: Seating: Ventilators: Hatches: Staircases / steps: Mooring ropes: Fenders: Windows / blinds: Lighting: Air conditioner: Make, type: Operational? Engine and steering console: Controls: Switchboards: LOWER DECK Layout: (See Figure 2) Bathrooms: Galley equipment: Deck materials / carpets: Doors: Windows, ports and deadlights: Staircases / steps: Lockers: Air conditioners: Upholstery and fittings: Lighting: Power points: SWIMMING PLATFORM Layout: Deck material: Stern shower: Transom: XXX MARINE CONSULTANTS LTD CONTINUATION-5-XMC**** VESSEL NAME 161 FLYING BRIDGE Layout: Deck material: Staircases / steps: Guardrails: Lockers: Steering gear and engine: Controls: Make, type: Operational? Bimini: FIRE FIGHTING EQUIPMENT AND LIFE SAVING APPLIANCES Liferaft: Fire blanket: Lifejackets: Lifebuoys: Fire extinguishers: TANK CAPACITIES Layout: Fresh water: Pumping arrangements: Fuel: Pumping arrangements: Sewage: Pumping arrangements: Grey water: Pumping arrangements: Overboard valves: Pipework: MACHINERY & EQUIPMENT Engine: Make, type: Operational? Propeller, shaft, stern gland, ‘A’ bracket, cutlass bearing, etc: Rudder: Trim tabs: Bilge pump: Generator: Make, model, serial numbers, kW, hours, location, hoses, clamps, belts, pulleys, cooling system, oil condition. Pipework: Batteries: Number, type, voltage, connections, storage, selector switches. Charger type? Monitoring system? Horn: Tested? Wipers: Tested? XXX MARINE CONSULTANTS LTD CONTINUATION-6-XMC**** VESSEL NAME 162 Searchlight: Make, type: Operational? Air conditioning system: Engine room blowers: Water heater: Make, type: Operational? Navigation lights: Tested? Electrical systems: Breakers, connectors, earthing? Transformers? Inverters? Shore power provisions? CONDITION OF HULL External hull: Survey afloat or on slipway? GRP? Timber? Steel? Aluminium? Colour? Cosmetic appearance, structural condition? Propeller: Anodes: Decks: Materials? Hull to deck structure? Frames? Stringers? Bulkheads? Stem? Transom internals? Superstructure: Internal hull, bulkheads, etc: Mooring equipment, anchors, striker plates, cables, mooring ropes, bitts and fairleads: WT openings, doors, ports, escape hatches and skylights: Ventilators, pipes, sounding pipes and closing devices: Deck lighting: GENERAL CONDITION OF VESSEL Accommodation, furnishings: Electrical equipment, stereo, TV, etc: Galley: Storage lockers, cabinetry: Paint and varnish: Light fixtures and lighting: Medical: Ladders: Air conditioning: Type: Filters? Drip trays? Condensate drain? Hoses & connections? Cooling pump? Water systems: Bathrooms, heads: General remarks Our survey took place on , whilst the vessel was on the slipway at and during a short sea trial. The underwater area was inspected on the slipway, the moisture content readings were found low one hour after the vessel being taken out of the water. There were no visible signs of hull deterioration or any obvious onset of osmosis. XXX MARINE CONSULTANTS LTD CONTINUATION-7-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -8 XMC**** Notes: CONTINUATION VESSEL NAME • Higher moisture content readings are generally to be expected immediately after the vessel has been taken out of the water. • The moisture content meter is used only as a barometer of moisture content, i.e. indicating trends, not an absolute reading. • It is also recommended that GRP hulls be allowed to dry out for a minimum of seven days before readings will give a realistic indication of the true moisture content of the hull laminate. • It should be borne in mind that GRP boats in South East Asia tend to remain in the water almost all year, as opposed to those in cooler climates where such vessels are generally removed from the water during winter months. • Blisters are an unknown factor on all boats and, if not currently present, there is no guarantee that they will not appear in the future. Blisters have a tendency to dry out over winter storage unless severe or large. Blisters (if any) best appear after a vessel has been in water for an entire season. In addition, the symptomatic evidence of blistering can be obscured by bottom coatings, a dry storage period during which blisters spontaneously depressurise, bottom laminate sanding, and other conditions or actions. We recommend a full inspection for blisters immediately after haulout and a power wash. • Our surveyor has no first hand knowledge of the history of bottom maintenance, blistering, repairs or prophylactic coatings for this vessel. During the short sea trials, the starboard engine raw water pump hose was found loose and dislodged at the fuel cooler ends. Four inches of sea water were found in the starboard engine bilge resulting from the loose connection. The hose ends of the oil cooler were reportedly shortened by an inch due to the ends of the hose deteriorating. The proper replacement hose had been ordered through service centre right after the short sea trial and reportedly to be replaced by the technician upon arrival. T he vessel is well appointed and in clean, tidy condition. We believe the vessel has been maintained to a high standard on a regular basis. In the opinion of the undersigned, taking into consideration the age of the vessel and activities, this vessel is considered to be generally in good / fair / satisfactory / poor / unsatisfactory condition at this time, , considering normal wear and tear and subject to comments as contained herein. We believe that, in the current open market conditions between willing buyer and seller, the vessel’s value is approximately subject to the defects below being rectified. Date and place of survey: Survey no. XMC****: For and on behalf of: Defects Noted 1. END. XXX Marine Consultants Ltd 163 This page intentionally left blank 164 Appendix 2: Specimen Machinery Damage Survey Report 165 This page intentionally left blank 166 XXX Marine Consultants Ltd Marine Consultancy • Hull, Machinery and Cargo Surveying Tel: Fax: Mobile: Email: Your Ref : Our Ref Date : XMC*** : Machinery Damage Survey Directors: Name, degrees, membership of professional organisations, etc. 167 168 TABLE OF CONTENTS 1. Vessel particulars ................................................................................................................................1 Table 1. Details of the vessel’s trading certificates. ......................................................................2 2. Parties attending .................................................................................................................................2 3. Background .........................................................................................................................................3 4. Survey findings - ...................................................................................................................4 Figure 1. Plan view of camshaft. .....................................................................................................5 Figure 2. Diagram showing configuration of hydraulic actuator cam follower. ....................5 Table 2. Details of damage and recommended repairs. .............................................................6 5. Survey findings - ...................................................................................................................6 6. Survey findings - ...................................................................................................................7 7. Survey findings - ...................................................................................................................7 8. Cause of damage ................................................................................................................................8 Table 3. Details of lubricating oil analysis results........................................................................9 9. Cost of repairs ...................................................................................................................................11 10. Notes ................................................................................................................................................11 APPENDIX 1 ...................................................................................................................... Photographs APPENDIX 2 ....................................................................................................................... Copy of ship’s particulars APPENDIX 3 ....................................................................................................................... List of ship’s certificates APPENDIX 4 ....................................................................................................................... Copy of Master’s Note of Protest APPENDIX 5 ....................................................................................................................... Copy of Chief Engineer’s Statement of Facts APPENDIX 6 ....................................................................................................................... Copy of most recent Class quarterly report. APPENDIX 7 ....................................................................................................................... Copy of crew list. APPENDIX 8 ....................................................................................................................... Copy of pages from the main engine manual relating to fuel and exhaust hydraulic actuator cams and followers. APPENDIX 9 ....................................................................................................................... Copy of engine maker’s lubricating oil requirements for the engine. APPENDIX 10 ..................................................................................................................... 169 Copy of engine maker’s service bulletin relating to the engine. APPENDIX 11 ..................................................................................................................... Copy of main engine lubricating oil analysis results. 170 XXX Marine Consultants Ltd Marine Consultancy • Hull, Machinery and Cargo Surveying Tel: Fax: Mobile: Email: Your Ref : Our Ref : XMC*** Date : Machinery Damage Survey IN ACCORDANCE with instructions received from , our Surveyor attended on board at , on , to assess the cause, nature and extent of damage sustained to the main engine camshaft and associated equipment. 1. Vessel particulars is a single hull, single screw, all steel, bulk/log carrier, having five cargo holds, the accommodation and engine room being abaft No. 5 hold. Name: Type: Registered: IMO No: Call sign: Owner: Operator: Class: Built: GRT: NRT: Deadweight: LOA: LBP: Dmould: Draft: Bmould: Main engine: Speed: The ship is fitted with four electrohydraulic deck cranes of 25 tonnes SWL. Hatchcovers are of the end folding MacGregor hydraulic ram operated type. 171 SHIP CERTIFICATES Issued - Date and place Date of expiry Registry: Safety construction, issue: Safety equipment, issue: Safety radio: International loadline: Annual loadline: ISM DOC: ISM SMC: Firefighting appliances: Liferaft servicing: Hull special survey: Hull annual survey: Machinery special survey: Machinery annual survey: Refrigeration machinery: Drydock survey: Cargo gear quadrennial: Cargo gear annual: IOPP issue: IOPP annual: MSM: US water pollution: US Coast Guard compliance: Port State inspection: Garbage cert. (IMO Anx): Table 1. Details of the vessel’s trading certificates It is reported that an underwater survey was carried out by the owner in conjunction with Class prior to handover of the vessel on . 2. Parties attending During our Survey of : Captain Master of the vessel. Superintendent Engineer, , manager of the vessel. Principal Surveyor, , appointed on behalf of . The Undersigned Appointed on behalf of underwriters. During our Survey of : Captain Master of the vessel. Superintendent Engineer, , manager of the vessel. Director, , on behalf of the P&I Club, Owner’s P&I Club. Senior Engineer, , engine maker. XXX MARINE CONSULTANTS LTD CONTINUATION-2-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -3 XMC**** T he Undersigned Appointed on behalf of Underwriters. of , had attended earlier in the morning. During our Survey of : Captain Master of the vessel. Captain Director, , , Manager. CONTINUATION VESSEL NAME Superintendent Engineer, Ship Management, , Manager. Director, Consultants Pte Ltd, on behalf of the P&I Club, Owner’s P&I Club. Senior Engineer, , engine maker. Representing Underwriters. T he Undersigned Appointed on behalf of Underwriters. During our Survey of : Captain Master of the vessel. Superintendent Engineer, , manager of the vessel. Director, Consultants Ltd, on behalf of the P&I Club, Owner’s P&I Club. Senior Engineer, , engine maker. Principal Surveyor, , on behalf of Owner. T he Undersigned Appointed on behalf of Underwriters. 3. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Background T he new owner’s Superintendent, , and the Chief Officer had boarded at , 10 days prior to the vessel’s handover on . The vessel had visited and , before being delivered to her new owner on , at the inner anchorage, . T he vessel changed Class from to at handover. T he vessel shifted to the outer anchorage, using the main engine, at on , to wait for orders. T he vessel departed on , at economical speed of 75 rpm, 10 knots, heading for . On 1140 hrs on , the Chief Engineer informed the Master that there were problems with the main engine. At 1230 hrs, after an inspection, he informed the Master that the damage was serious, being to the camshaft. Temporary repairs were made to the engine and at 1700 hrs the vessel returned to at slow speed, arriving at at 0830 hrs on . On , a Sulzer specialist, , attended on board the vessel to assess the damage. T he vessel shifted from the anchorage to Dockyard at 1200 hrs on with the assistance of two tugs. At 1540 hrs the tugs were changed to harbour tugs. T he vessel arrived at Dockyard at 1621 hrs. The vessel was all fast at 1700 hrs. 172 XXX MARINE CONSULTANTS LTD -4 XMC**** 4. Survey findings - CONTINUATION VESSEL NAME Notes: The main engine cylinders are numbered from aft. Figures 1 and 2 show the configuration of the camshaft, cams and followers. 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 We sighted the main engine with the camshaft covers removed for inspection. We found Nos 1, 2, 4, 5 and 6 hydraulic actuator cams variously abraded, the usually smooth surfaces being very rough, Nos 1, 2 and 4 being severely abraded (see Photographs 4 to 17). We found Nos 1, 2 and 4 fuel pump followers (rollers) completely disintegrated with little of the rollers remaining. Whilst the cam shaft is normally lubricated by oil from the lubricating system and falling oil from the fuel pump pistons, the cam followers are lubricated by means of a jet from a hexagonal nut fitted to the inner surface of the camshaft cover. This oil is also supplied from the main lubricating oil system (see Photographs 18 to 20). T he Superintendent reported that the small holes in the hexagonal nuts of Nos 1, 2 and 4 camshaft lubricating oil sprayers had been found blocked. When poked with a pin these had cleared immediately and given a full spray of oil. Nos 3, 5 and 6 had been found slightly blocked and had also been cleared in the same way. We sighted the lubricating oil pump filters having been removed for inspection, and found no unusual or large particles in the filters (see Photographs 21 and 22). T he Superintendent reported that the lubricating oil purifiers were on a two-hour autocleaning cycle and that they were operating correctly. We took a sample of the main engine lubricating oil at the suction side of the main lubricating pump in the company of the Superintendent Engineer. Damage and recommended action is shown below in Table 2. 173 174 Figure 1. Plan view of camshaft Figure 2. Diagram showing configuration of hydraulic actuator cam follower XXX MARINE CONSULTANTS LTD CONTINUATION-5-XMC**** VESSEL NAME 175 Details of damage and recommended repairs Item Damage Recommended No. 1 Exhaust hydraulic actuator cam Severely abraded Renew No. 2 Exhaust hydraulic actuator cam Severely abraded Renew No. 3 Exhaust hydraulic actuator cam Heavily abraded Renew No. 4 Exhaust hydraulic actuator cam Severely abraded Renew No. 5 Exhaust hydraulic actuator cam Heavily abraded Renew No. 6 Exhaust hydraulic actuator cam Heavily abraded Renew No. 1 Fuel cam Cam OK, roller heavily abraded Renew roller No. 2 Fuel cam Undamaged None No. 3 Fuel cam Cam heavily abraded Renew roller No. 4 Fuel cam Cam heavily abraded Renew roller No. 5 Fuel cam Cam heavily abraded Cam to be polished No. 6 Fuel cam Cam heavily abraded None 12 Cam follower bushes Abraded Renew 12 Cam follower pins Deformed Renew 24 Thrust washers Deformed Renew Exhaust hydraulic actuator roller guide spring Damaged Renew Exhaust actuator guide roller Damaged Renew Lubricating oil To be changed Sump tank To be cleaned and flushed through LO filters To be checked Purifiers To thoroughly check for correct operation Table 2. Details of damage and recommended repairs 5. Survey findings - 5.1 We found the main engine partially reassembled with only fuel pipes remaining to be fitted to the fuel pumps and associated camshaft covers. We noted that all hydraulic actuator cams and followers had been renewed. All fuel pump cams and followers had been reground (see Photographs 27 to 33). 5.2 We sighted various damaged parts: a. Heavily abraded hydraulic actuator cams (see Photograph 34). b. Heavily gouged out hydraulic actuator camshaft followers for Nos 1, 2 and 4 cylinders (see Photographs 35, 36, 43, 45 and 47 to 50). c. Variously worn hydraulic actuator cam follower locating pins for all cylinders (see Photographs 37 and 38). Nos 1 and 4 locating pins were reduced in length by up to 12 mm. We note that No. 2 locating pin was not found. The superintendent reported that when removed at the time of the incident the locating end of the pin was missing. XXX MARINE CONSULTANTS LTD CONTINUATION-6-XMC**** VESSEL NAME 176 d. Broken hydraulic actuator cam follower springs for five cylinders (see Photographs 37 to 42). These were broken into more than two parts. The only sound spring was reported to be from No. 6 unit. 5.3 We were informed that, as a consequence of damage to the cam follower springs and locating pins, all hydraulic actuator cam follower springs and locating pins had also been renewed. 5.4 We note that the last inspection of the camshaft, under the ‘Continuous Survey of Machinery’ regime should have been carried out in . However, there were no maintenance records remaining on board after handover of the vessel. Consequently, there were no total operating hours for the main engine or hours since last major overhaul and inspection of the camshaft. We estimate that the total running hours would have been in the order of 105,000 hours. 6. Survey findings - 6.1 We attended on board in the morning to sight the completed repair work. We also sighted and photographed various damaged parts (see Photographs 37 to 42). 6.2 Trials commenced at 1300 hrs that afternoon. 6.3 We were called back to the vessel later that evening when it was reported that the main engine No. 3 unit hydraulic actuator cam follower had seized. 6.4 We sighted the main engine No. 3 unit hydraulic actuator cam follower removed from the engine in the workshop. We also sighted the main engine No. 3 unit hydraulic actuator cam. 6.5 We found the cam to be heavily abraded. 6.6 We found the main engine No. 3 unit hydraulic actuator cam follower roller to be worn down by approximately 3 mm. 6.7 The Superintendent and reported that when the engine was first started and running at slow speed all cam followers were noted (through inspection ports) to be rotating with no apparent problems. Lubricating oil was also noted to be flowing and circulating with no apparent problems. 6.8 When the engine speed was increased to 80 revolutions per minute (RPM), it was noted that the main engine No. 3 unit hydraulic actuator cam follower started to seize with a jerking rotational movement, until it seized completely. The engine revolutions were reduced to 40 RPM and the main engine No. 3 unit hydraulic actuator cam follower eventually rotated freely. 6.9 When we sighted the main engine No. 3 unit hydraulic actuator cam follower in the workshop the roller was noted to be rotating freely. We therefore concluded that there was a problem with the roller pin and bush clearances. 7. Survey findings - 7.1 We attended on board in the morning to sight the completed repair work. It was reported by the Owner’s Superintendent that No. 3 unit hydraulic actuator cam and cam follower had been renewed. XXX MARINE CONSULTANTS LTD CONTINUATION-7-XMC**** VESSEL NAME XXX MARINE CONSULTANTS LTD -8 XMC**** 7.2 CONTINUATION VESSEL NAME We sighted the dismantled main engine No. 3 unit hydraulic actuator cam follower. We found the roller pin and bush to be blued due to excessive temperatures. The blueing appeared to be only at one end of the pin and on the corresponding end of the bush, suggesting that the pin or bush were not totally cylindrical and possibly slightly tapered. 7.3 7.4 8. 8.1 8.2 We were informed by the representative that the affected parts had been received on board in the assembled state. Trials commenced at 1300 hrs on the same day and we believe the vessel commenced her voyage to Amsterdam later that afternoon. Cause of damage T he Owner’s representatives have not yet made any allegation as to the cause of the damage. We have received a copy of the lubricating oil analysis carried out between of samples taken from the main engine lubricating system on board on . The analysis was carried out by (Lab Ref. No.). Results are shown in Table 3, together with a summary of the analysis supplied by : T he following comments were also added to the report: T he oil represented by this sample contains (5.0%) water (comprising ⅓ sea). This oil is therefore unfit for service and must be removed from the system as soon as possible. We also suggest the following: The source/s of the water ingress should be traced and corrected. The contaminated oil should be pumped into a renovating tank, heated up to 90 ºC and, after settling and draining, undergo intensive dry purification at 85 ºC - 90 ºC in order to remove the remaining water. After this treatment has been completed, further samples should be landed to monitor the oil condition. On the wear metals, iron content is slightly increased (80 ppm) and copper content seems to be high (78 ppm - check bearings, coolers). 177 178 LUBRICATING OIL ANALYSIS RESULTS analysis results Engine maker (recommended) Viscosity @ 40ºC 123.17 160 Closed flash point SETA (0-300) >200 190 Total insolubles 0.47 0.02 Base number (11-27) 7.21 30 Water content % 5.00 0.5 Chlorides in water 1/3 sea water 0 Free water % 0.5 Condition Colour Wear metals by ICP in ppm Copper 78.00 Lead 15.00 Tin ND Aluminium 4.00 Silver ND Iron 80.00 Molybdenum ND Chromium 1.00 Manganese 1.00 Nickel 9.00 Vanadium 23.00 Silicon 6.00 Sodium 19.00 ND = Not detected Table 3. Copy of lubricating oil analysis results carried out between , carried out by of (Lab Ref. No.) (See Appendix 11 for original document) XXX MARINE CONSULTANTS LTD CONTINUATION-9-XMC*** VESSEL NAME XXX MARINE CONSULTANTS LTD -10 XMC**** 8.3 CONTINUATION VESSEL NAME T he lubricating oil sample analysis shows that the lubricating oil did not meet the quality requirements of engine makers (see Appendix 9). We believe that the poor quality of the lubricating oil was the cause of the incident. This is supported by section 3.1 of the engine makers’ service bulletin, Warranty Surveying in the Offshore Industry 1 MWS. Introduction. The development of offshore oil and gas exploration and production from the 1960s through to renewable energy sources today has changed the way underwriters look at the increasing risks attached to offshore marine projects. The marine aspects of these offshore projects now involve extremely complex structures and floating facilities. This development created additional risks over and above any normal shipping operation. The underwriters had to cover these new risks, including towage, load-outs, field installations, seabed structures, underwater facilities, construction and heavy lifts, under special insurance policies. To protect their interests in these policies the underwriters identified the requirement for a specialist independent third party. The role of this specialist person would be to review and approve these marine projects on behalf of the underwriter. This saw the introduction of the Marine Warranty Surveyor. Initially the classification societies took on this role and to an extent some still carry out this work. However, as the role became more and more specialist as offshore projects became more complex, specialist warranty companies expanded on a worldwide basis. As these companies affirmed their competence and abilities they gained the confidence of the major stakeholders in the offshore industry: the oil companies, offshore contractors and underwriters, so they now provide the majority of warranty services throughout the world. Underwriters recognised that even more, in today’s environment, these marine operations are high risk by their very nature. The claims profiles in these offshore projects are therefore also very high as there are many additional factors that affect a project’s risk level including the marine environment, shorter project timeframes, tighter project budgets and, of course, increasing the exploration boundaries with deeper and deeper waters requiring new methods of construction and installation. The role of the marine warranty surveyor is to act on behalf of the insurer and the assured to ensure that specific operations are carried out to recognised codes of practice, industry standards and to acceptable risk levels. These risk levels need to be tolerable to the insurance interests, the offshore industry and to the rules and regulations of any national or international authority. During the operational stages of an offshore project, which may include construction, installation and commissioning and all the associated operations required to fulfil the aims of the project, there will be in place a Construction All Risks insurance policy. In the majority of these cases, unless it is a very low level risk, the terms of the policy will include a warranty clause. The underwriter will require that an independent marine warranty surveyor is appointed for the whole of the project to act as an expert on their behalf. The scope of the approval activities to be conducted by the marine warranty surveyor will be agreed before commencement of any operation between the assured and the underwriter. This is based on the actual project activities to be carried out and the risk levels associated with these activities. 000006 It is the responsibility of the assured (the insured party) to appoint the marine warranty surveyor. However, this surveyor must be acceptable to the underwriter (insurer). The policy will normally list the warranty companies acceptable to a particular underwriter. The aim of this unit is to provide the student with a description of the principles involved in marine warranty surveying and the processes and procedures employed by the warranty company and the warranty surveyor to enable them to complete their primary function. 000007 Chapter 1 1.0 Commercial and Professional Aspects of Warranty Surveying Warranty surveying involves working very closely with marine underwriters and the marine insurance market. It is paramount that warranty surveyors not only have a vast wealth of knowledge and experience in the practical elements of warranty work but they must also have a sound understanding of the basic principles of marine insurance. 1.1 Marine Insurance (see also appendix E) The Marine Insurance Act of 1906 is the act upon which all subsequent acts are based. This is on an international level where national governments have received the “English Act” into their own constitutional law. This would then be the basis for further introduction of federal or provincial statutes appertaining to marine insurance as determined by the national government. As a marine surveyor it is important that you have an understanding of the act and its contents. The scope of marine insurance is determined by the definition of “maritime adventure” and “maritime peril” contained within the act. Maritime adventure: is any situation where the insured is exposed to a maritime peril and includes any situation where: i the earning or acquisition of any freight, commission, profit or other pecuniary benefit is involved ii any liability to a third party may be incurred by the owner of, or other person interested in or responsible for, insurable property, by reason of maritime perils Maritime perils: are perils subsequent on or incidental to navigation including perils of the seas, fire, war perils, acts of pirates or thieves, captures, seizures, detainments of people, jettisons, barratry and all perils of a like kind, and in respect of a marine policy, any peril designated by the policy. Marine insurance is a contract where the insurer undertakes to indemnify the insured in the manner and to the extent as agreed in the contract. The extent of the indemnity is determined by the contract. It relates to losses incidental to a marine adventure or to the building, repairing or launching of a ship. Types of marine insurance There are four types of marine insurance: Hull and Machinery – the insurance of ships, yachts and other vessels against physical damage Cargo – insurance relating to cargo, this may include freight forwarders’, CMR and carriers’ liability Protection and Indemnity (P&I)- insurance for shipowners’ liability to third parties Offshore energy sector – the insurance of all offshore exploration and production activities including fixed and mobile units, construction risks. (There is also marine related insurance cover for ship builders’ and repairers’ liabilities, marinas and dock owners’ liabilities and terminal operators’ liabilities) 000008 Types of marine policies Although the Marine Insurance Act regulates areas of the marine insurance contract, it preserves the freedom of contract. This basically means that the parties involved have the freedom to decide the extent of their obligations and responsibilities. The terms of the contract are contained in the policy of insurance. There are a number of very basic requirements that must be contained in a marine policy: • the name of the insured • the subject matter insured • the perils insured against • the voyage or period of cover • the sum insured • the name of the insurer The policy must also be signed by the insurer. Marine policies can be categorised into “Specified Perils ”and “All Risks”. Specified Perils policy: This is a policy in which the insurer agrees to indemnify the assured for losses caused by specific perils that are identified in the policy. A loss must be caused by one of the perils in order for the loss to be covered by the policy. The majority of hull and machinery polices on commercial vessels are insured on a specified perils basis, or sometimes called a named perils policy. All Risks policy: These policies provide a much wider coverage. The policy is one in which the insurer agrees to indemnify the assured “against all risks of loss or damage”. Anything not covered by an all risks policy need to be specifically excluded. The majority of cargo and yacht and leisure craft policies are on an all risks basis. Marine policies are further split into “Time” and “Voyage” policies. Time policy: If the policy simply states that the insurance covers the subject for a period of time then it is a time policy. The policy ends at the expiry of the time specified in the policy. Voyage policy: If in the policy the words “at and from” or just “from” a particular place to another particular place are used then it is a voyage policy. The policy ends at the end of the voyage. Under the insurance act there are special rules for voyage policies: i there is an implied term that the venture will start within a reasonable time ii the policy will not be valid if the ship sails from different places than in the policy iii if after commencement of the venture the port of destination is voluntarily changed then the insurer is discharged from liability at this point of change iv a deviation without lawful reason from the agreed route discharges the insurer from liability on or after the deviation v a voyage policy must be carried out in reasonable time, any unreasonable delay will discharge the insurer from all liability for any loss as a result of this delay 000009 The insurance act sets out what a justifiable deviation or a delay is: “Reasonably necessary for the safety of the ship or subject matter insured.” Marine policies will also have pecuniary considerations in which the policies are “Valued” or “Unvalued.” Valued policies: If the policy specifies the agreed value of the subject of insurance then it is a valued policy. In the case of a total loss the amount of the indemnity is the agreed value. Unvalued policies: If the policy does not specify an agreed value but provides a limit of the sum insured it is an unvalued policy. In the case of a ship loss, the indemnity is the value of the ship at the commencement of the risk plus any insurance charge. Insurance terms In the insurance market as in many other industries and professions there are words and terms used that should be understood by those involved directly or indirectly with that industry or profession. The marine insurance industry is no exception. “Utmost good faith”, “Disclosure” and “Misrepresentation” are three important terms that a marine surveyor should understand. Utmost good faith: A contract of marine insurance is based on the principle of “utmost good faith.” If this “utmost good faith “ is not observed by either party the contract may be avoided by the other party. Disclosure: The marine insurance act sets out certain disclosure requirements. The two important points are: i an insured must disclose to the insurer every material circumstance that is known to the insured ii an agent who effects insurance for an insured must disclose to the insurer every material circumstance known to the agent as well as every material circumstance that the insured must disclose Misrepresentation: There are a number of ways this is dealt with under the Marine Insurance Act. Two important points have to be addressed: i every material representation made by the insured or the insured’s agents to the insurer during the negotiations for the contract and for the term of the contract must be true ii a representation is material to the negotiations if it would influence the judgement of a prudent insurer in fixing the premium or even taking on the risk We have used the word “material” on several occasions in the previous paragraphs. To clarify the use of this word in marine insurance terms we can look at a number of examples of material information: “ the age of the vessel” “ that the ship had gone into port for repairs at the commencement of the voyage” “ that the vessel was to be towed down the river” “ the poor claims record of the insured” 000010 Finally, the main principle of the Marine Insurance Act is that the assured must have an insurable interest in the venture. This prevents the contract being used as a means of gambling by non interested parties. “A person who has an interest in a marine venture has an insurable interest.” Having an interest in a marine venture is defined in this way: “if the person has a legal relation to the venture or any insurable property at risk in the venture and may be prejudiced by its loss, damage or detention and may incur liability” Examples of insurable interest are the master and crew who have an insurable interest for their wages, and a mortgagee and a person who advances freight payments also each have an insurable interest. The parties in the insurance market In the insurance market there are a number of parties that are involved in or act to effect coverage of a marine venture. Assured: The party/person who has taken out the policy and pays the premium. Underwriters: The entities that actually agree to indemnify the assured. They can be individuals or corporate bodies. In the “Lloyd’s” market the underwriters are represented by syndicates. These syndicates negotiate and sign policies on behalf of the underwriters. The syndicates are known as “Names.” Under this system it is the norm that more than one underwriter will be involved. In this way the level of indemnity is spread over a greater number of underwriters who, in turn, will decide the level of indemnity they wish to cover for this specific venture. The first name on the policy is usually known as the lead underwriter. This underwriter will make most of the decisions in the event of a loss. Underwriting Agents: These are entities that have authority to sign an insurance policy on behalf of an underwriter. They sign as agent only, which means they have no liability to the assured under the contract. They may represent more than one underwriter. Insurance Companies: Many traditional insurance companies have marine departments involved in all manner of marine insurance ventures. They often employ the services of the underwriting agent. P&I Clubs: These are mutual insurance companies that offer third party liability cover to shipowners. They do not actually issue a policy of insurance. The coverage for its members is laid down in the club’s rules. Brokers: They play an important role in effecting coverage for the assured. The broker, with the assured, will determine the specific insurance requirements. The broker will then go to the market to negotiate the best deal for the assured. 000011 1.2 Warranty Insurance The term Marine Insurance Warranty is based on the UK Marine Insurance Act 1906 and is defined in the industry as follows: “A marine insurance warranty is a promissory warranty by which the assured undertakes that some particular thing shall or shall not be done, or that some condition shall be fulfilled, or whereby the assured affirms or negates the existence of a particular state of facts. The assured must comply literally with the terms of a warranty. Compliance in spirit is not acceptable. If the assured fails to comply with the terms of the warranty, the insurer is discharged from all liability under the policy as from the date of breach of warranty but without prejudice to insured losses occurring prior to such date. A warranty may be “expressed” or “implied.” These terms of reference may be regulated according to local law in a specific country. We have used the terms “expressed” and “implied” warranties in the above definition. These are two terms that a marine warranty surveyor must understand completely. Implied Warranties In the marine insurance act there are three implied warranties: the warranty of legality, the warranty of neutrality and the warranty of seaworthiness. Legality: There is an implied warranty in every marine policy that the marine venture insured is lawful and, in so far as the insured has control, will be carried out in a lawful manner. The warranty of legality is often expressed in a policy as well as being implied. Neutrality: In any marine policy where insurable property is expressly warranted as neutral there is an implied warranty in the policy that: i the property will have a neutral character at the commencement of the risk and during the risk ii if the property is a ship the papers necessary to establish neutrality will be carried on the ship Seaworthiness: The implied warranty of seaworthiness applies with full effect only to voyage policies. The warranty is that the ship will be seaworthy “at the commencement of the voyage” for the particular venture insured. A seaworthy ship is one that is “reasonably fit in all respects to encounter the ordinary perils of the venture insured”. In a time policy there is no warranty of seaworthiness but if the ship, with the knowledge of the assured, is sent to sea in an unseaworthy condition, the insurer is not liable for any loss attributable to unseaworthiness. Therefore in a voyage policy the insurer only needs to prove one thing: that the ship was unseaworthy at the commencement of the voyage. In a time policy the insurer has to prove three things: that the ship was unseaworthy, that the unseaworthiness caused the loss and that the insured knew that the ship was in an unseaworthy state. The warranty of seaworthiness relates not only to the ship’s hull but also the machinery, ship’s equipment, the crew and the load condition of the ship. 000012 Expressed Warranties An expressed warranty must be included in or written on the marine policy, or contained in a document incorporated by reference into the policy. The warranty can be in any form of words from which the intention to warrant is inferred. Therefore the wording in the policy must be very carefully considered to affirm if any provision in the policy is a true warranty. In practice it has been difficult for insurers to find the exact wording that will actually confirm that inference. The number of expressed warranties is unlimited and depends on the underwriter. Practically anything can be written on a policy as an expressed warranty as long as the correct wording is used. To clarify the type of expressed warranties used in practice we will look at a number of common examples: “limiting the geographical areas in which a ship may trade” “prohibiting the ship from being towed except where customary or when in need of assistance” “prohibiting a private pleasure yacht from being used for commercial purposes” “requiring surveys and inspections to be conducted and any recommendations by surveyors complied with” Now that the warranties are in place we have to consider what happens if there is a “breach” of warranty. A breach of warranty is a failure of the assured to comply with the terms of the warranty in the policy. Breach of warranty in the offshore industry usually occurs as a result of one of two events/occurrences. The assured or their contractor fails to receive a Certificate of Approval (CoA) from the warranty surveyor prior to commencing an operation where the scope of the operation has been clearly defined, or there is a failure to adhere to the procedures approved by the warranty surveyor during the performance of the operation. It is the responsibility of the warranty surveyor to notify the assured if there is a potential or actual breach of warranty. The surveyor must do this in writing giving his reasons. At this time the CoA for the operation becomes invalid. In such an event the insurer may avoid the policy if an incident or damage occurs to an insured item during the period of breach. 1.3 The Stakeholders Oil and gas companies and offshore renewables The major stakeholders in the offshore oil and gas industry are, of course, the oil companies. These may be the major, well known, what you may call “High Street name” private companies like ExxonMobil, Shell, BP, Chevron. Then we have the national oil companies like Statoil of Norway and ENI of Italy. There are of course many smaller but just as active oil companies like Enterprise, Marathon, Anadrako that invest in exploration and production but which do not involve themselves in refining or retail downstream operations. Then we have the renewable energy industry that has developed over the last ten years with major windfarm projects being undertaken offshore in many parts of the world from the Far East to the North Sea. Many of these construction and operating companies have been specifically set up to develop offshore wind power in large offshore wind farms, for example Dong Energy (www.dongenergy.com) and e-on UK (www.eon-uk). 000013 The renewable energy industry has looked to the oil and gas industry to utilise already developed tried and tested operational procedures and design concepts for its own offshore field installations. Contractors Contractors are usually headed by a main contractor or lead contractor who then sub-contract specific tasks to suitably experienced and qualified companies. These companies will have been set up to provide specialist services and include Acergy (www.acergy-group.com) and Aker Marine Contractors (www.akersolutions.com), or they may be a separate division of a larger civil engineering company the names of which people may be familiar with, such as Balfour Beatty (www.balfourbeatty.com) and Kier (www.kier.com). Shipowners The offshore industry has over the years designed and built an ever increasing number of specialist vessels to complete specific tasks associated with offshore exploration and production. These shipowners range from the FPSO owners like Teekay Shipping (www.teekay.com) anchor handling and supply vessels like Farstad (www.farstad.com), heavy lift vessels like Jumbo Shipping (www.jumboshipping.nl) and semisubmersible heavy lift vessels like Dockwise (www.dockwise.com). Equipment owners and lessors To enable many projects to be feasible there is a need for specialist equipment and materials. New concepts and designs are constantly coming to the market to fulfil a specific task. These companies range from the supply of anchors to complete spread mooring systems like Viking (www.viking.com) or Vryhoff (www.vryhoff.com) and anchor handling equipment for the anchor handling operations like Triplex MDH (www.triplex.com). The marine warranty surveyor must keep abreast of all future developments in the offshore industry. The advent of the renewable energy industry has also brought with it new vessels and equipment that the warranty surveyor must be conversant with. 1.4 The Warranty Company The demand for more oil and gas and, today, renewable energy sources has increased tenfold over the last fifty years. This has meant increased exploration with more and more installations and production facilities being constructed. In turn the risks involved in the offshore industry have equally increased. The role of the warranty surveyor has taken on a whole new meaning as underwriters make demands on the assureds to appoint reputable warranty companies to act on their behalf during any operation in which they act as the insurer. Over the last twenty years a number of warranty companies have expanded and now operate on a global basis, for example London Offshore Consultants (LOC www.loc.com). These companies, through their integrity, professional standards and expertise, are recognised and accepted by the underwriters in this area of insurance. The underwriters will usually have their preferred warranty company. This does not mean an assured has to use that company but whoever the assured appoints must be acceptable to the underwriter. The modern warranty company will be made up, in the main, from two professional disciplines: engineers and mariners. In these two groups will be Master Mariners, Marine and Offshore Engineers, Subsea and pipeline Engineers, Structural and Civil Engineers and Naval Architects. 000014 This multidisciplinary approach gives the company the experience base to provide and satisfy the requirements of the underwriters and the insured parties. The company will be staffed from these disciplines with project teams set up to provide all the experience required to cover a particular operation. These companies are usually made up of base staff who provide the pre-operation evaluations and on going support, and the field surveyors who actually conduct the surveys and observe the contractors and associated sub-contractors as they perform the operation. As operator and contractor teams become smaller with less engineering and marine experience, the warranty surveyor can provide on site advice from these two areas. Typical areas that may involve the services of a warranty company and so a warranty surveyor: • Towage approval of ships and structures • Load out, float out, float on/off • Launching, upending of jackets • Mobile offshore drilling units (MODUs) moving, positioning and approval • Heavy lift evaluations • Mooring design and approval • Barge and tug evaluations and approvals • Seafastening design and approval • Motion and response analysis of floating structures • Analysis of sub sea pipeline • Preparation of operational procedural manuals • Structural and suitability approval for jack-up rigs • Risk and failure mode analysis for the offshore industry • Damage surveys to offshore ships and structures • Loss and seaworthiness investigations • Meteorological studies • Ship and floating structure stability analysis • Risk assessments for offshore operations • Feasibility studies for offshore projects Steel jacket launching off a barge Topside heavy lift This list is not exhaustive. As new high risk developments come into play and new ideas and projects come on line there is a constant need for the warranty company to be involved as a safeguard for the assured and the underwriters. 000015 The scope of the warranty company’s involvement will be through negotiation between the insurer and the assured. The insurer’s requirements will in most cases be based on the following: “the level of internal assurance measures already in place” “classification and/or any statutory regulation involvement” “complexity, sensitivity, novel design of the proposed operations” “asset value and project schedule constraints” “assured’s insurance history and the underwriter’s claims” Once all this information has been established the underwriter will allocate a risk level to each key factor based on the ALARP (As Low As Reasonably Possible) principle of which the warranty scope of work will be a function of the risk. The following table is an example of warranty levels used by LOC one of the major warranty companies. In practice it is sometimes difficult to define probability levels for some operations. In these cases the final selection of the warranty level will depend on relevant criteria of the actual operation. The underwriter will consider all these criteria and will allocate a risk level to each key function accordingly. Risk Level Warranty Level Warranty Scope Simple operations and high redundancy WO No Warranty Basic quality level for marine operations. No warranty approval required Well controlled simple operations or operations with high redundancy W1 Limited Scope of Warranty Warranty approval to be issued either based on documentation review only (e.g. MODU location approval) or surveys on site (e.g. lashing of cargoes). The most relevant alternative to be selected by the warranty surveyor Complex or weather sensitive operations W2 Standard Scope of Warranty As W1 but including both evaluation of design documentation and operational procedures and pre-operation verification surveys (e.g. towed barge transportation) Complex and weather sensitive operations W3 Full Scope of Warranty As for W2 but including on-site surveillance during the operation (e.g. skidded loadout, jacket launch, topsides lift, float-over complex sub-sea installation) Warranty Levels During the operation of a project the assured will always have the option to increase the scope of warranty surveyor. However, the scope cannot be reduced without recommendation from the warranty surveyor and/or the prior consent of the underwriter. 000016 To further illustrate what is involved in a warranty surveyor’s work scope we will look at a typical work scope, again used by LOC, for the load out, transportation, launch and upending, setting and piling of an offshore jacket. Marine Operation Review Engineering Procedure & Documents Attend Marine Operation Preparation Issue Vessel Survey or Attendance Report Issue Certificate of Approval Monitor Marine Operation Jacket transport & tow vessel surveys X Jacket initial skidding to load out area X X X X Jacket load out onto transportation barge and seafastening X X X X X Jacket towed transportation to site X X X X Jacket launch, up-end, wet tow X X X X X Jacket set down/installation X X X X X Pile handling & piling X X X X X Marine operation scope of work Many of the above actions will be performed as desk top review activities. There will be a front end review of all the functions and stages of the proposed project, design, specifications and limiting criteria. These criteria will range from steel coding checks to checking the design structures to be installed and design loads. Weather limits will always play a major part of the criteria review. On occasions where no pre-defined criteria are proposed the warranty surveyor may be asked to make recommendations based on his considerable knowledge and experience. The reason for setting the limiting criteria at this time is to set the governing limits to be used as reference during later reviews of the engineering calculations and procedures. All warranty companies, in order to apply their expertise and perform their functions to set standards, will have a series of what are known as the “Guidelines”. These guidelines are documents that define the rules, methodology and operational procedures by which surveys, inspections, operational methods, compliance and issuing of a Certificate of Approval are based. These guidelines reflect what is seen as best practice in the industry and so the content will not differ greatly from company to company. 000017 The following are examples of typical warranty company guidelines: • Standards Instructions for Warranty Surveyors • Guidelines for Marine Transportation • Guidelines for Loadouts • Guidelines for Mooring Systems • Guidelines for the Approval of Towing Vessels • Guidelines for Marine Lifting Operations • Guidelines for the Transport of Jack-Up platforms • Guidelines for the Towage of Ships • Guidelines for the Towage of FPSOs • Guidelines for Conducting Bollard Pull Tests • Guidelines for the Tow-out and Installation of Steel Jacket Structures • Guidelines for the Tow-out and Installation of Gravity Base Structures • Guidelines for Evaluating Pipeline Operations This is not exhaustive as the companies produce supplements and additional material where special consideration may be required for a particular operation or project. An example of this is for the towage of vessels and structures in ice covered waters. As well as these guidelines the companies will have in-house documentation that allows standardisation of reports, inspections and audits. The warranty company will also follow tried and tested methods for conducting the numerous engineering tasks they will have to undertake for any given project. These will include: • Site evaluation for the placement of platforms • Spread mooring capability • Stability analysis of barges and pontoons • Tow route evaluation including metocean considerations 000018 Typical weather routeing chart 1.5 The Warranty Surveyor’s Responsibilities (see also appendix D) The position of a warranty surveyor can be considered at the highest level. The asset values involved under insurance policies are immense. In today’s offshore industry building a jack-up will be in the region of $100,000,000 and upwards, while a new FPSO can be several hundred million dollars. This does not take into account the most important asset of all: that of the people involved in the offshore industry. On a more practical level, the warranty surveyor can only be responsible to one client on one operation. However, he still has a duty of care to the extent that his responsibilities will extend to other parties involved in the operation. As a technical advisor to his client it is his responsibility to safeguard the client from the consequences of actions or inactions that may affect the operation. 1.6 The Certificate of Approval (CoA) (see also appendix B) A Certificate of Approval is issued at the beginning of a voyage or operation. Seaworthiness in its narrow legal and general sense is a precondition for the issuance of such a certificate. The basis on which a CoA is issued is the fitness of the vessel or operation to begin and execute the operation under 000019 the special conditions applied by the warranty survey company in addition to the ability to “withstand the normal perils of the sea” as they affect that vessel or operation. Therefore any change in the seaworthy state of the vessels or operation to which the CoA applies will make the certificate terms invalid. The conditions attached to a CoA, which often require certain things to be done or complied with, should not conflict with the required seaworthy condition. If during the course of an operation for which a CoA has been issued the vessels suffer damage and they become unseaworthy then the conditions on which the CoA was issued may no longer apply. It is worth looking at a simple example to explain the position: A valuable refinery process unit is loaded on a barge for towage from A to B. If the CoA specifies a particular route and the tugmaster takes a short cut, the CoA may be invalidated and this may affect the insurance cover for the cargo even if the tug and barge remain seaworthy. If an accident occurs to the tug or barge during the short cut the underwriters of the cargo may avoid their liability in part or as a whole not least because damage to the tug or barge may make either unseaworthy, therefore invalidating the principal condition on which the CoA was issued. It has to be pointed out that many CoAs will be endorsed with the words “this document is NOT a certificate of seaworthiness” to protect the issuer of the CoA. It is also a reminder to the holder of the CoA that it cannot be used as evidence of seaworthiness in the future or during the voyage for which the CoA applies. Condition clauses on a Certificate of Approval: There are two parts to a CoA > the actual document > the attached recommendations The recommendations are further split: > those made prior to the commencement of an operation > those on the CoA Recommendations made prior to the commencement of an operation are usually the outcome of initial inspections or evaluations by both the base staff and field surveyors of the warranty company issuing the CoA. These recommendations must be fulfilled before the site warranty surveyor will issue a CoA. They may be to do with the vessel’s structure or equipment, certification, approved procedures manuals or as a result of an engineering study. They must be complied with or the venture cannot start as a CoA will not be issued if any of these preconditions are not met. 000020 Examples of preconditions for a jack–up move: Anchors: Aft anchors to be left in racks and secured. Forward anchors to be removed and stowed on deck. Legs: It is recommended that legs should be carried fully raised. All legs to be shimmed at the upper guides. Recommendations attached to the CoA are requirements from the warranty company to the holder of the CoA for the conduct of the operation. It is important to understand that the holder of the CoA has to abide by these recommendations if the CoA is to remain valid. The holder of the CoA must inform the warranty company if circumstances prevent the holder abiding by these recommendations. Examples of attached recommendations: Sufficient stability is to be safeguarded. The relevant national and international regulations regarding lights and shapes are to be complied with. The individual parts of the voyage are to be started only under good local weather conditions and a favourable meteorological situation. Issuing a Certificate of Approval The CoA is usually issued on site by the attending warranty surveyor. It is drawn up at the base office and left unsigned until the final inspection of the vessels or structures involved prior to commencement of the operation when the surveyor will sign it and issue the CoA. The actual signing and so issuing of a CoA may take some time as important preconditions may have to be met. Examples of important preconditions: When a jack-up is being moved from one location to another under a CoA, the surveyor will not sign the CoA until the jack-up has been jacked down into the water and is actually floating and found watertight. The requirement for the receipt of particular weather forecast conditions in which it has been determined that the operation may take place. 000021 Withdrawal of a certificate of Approval This is straight forward in that any failure to abide by a recommendation without good reason will result in the withdrawal of a CoA. Examples for withdrawal: Damage or deterioration of the vessel’s structures which affects the watertight integrity, structural integrity, stability, or suitability for the type of operation. Act or omission on the part of the client or his servants which endangers the subject matter of the CoA. Withholding a Certificate of Approval If in the opinion of the warranty surveyor or the base office they consider that the underwriter’s risk is compromised they may withhold a CoA. The following examples of reasons to withhold clarify the possible situations under which this may occur. These are only a few examples as the situation and circumstances prevailing at the time will dictate the actions taken by the warranty surveyor or the base office. Examples of reasons to withhold a CoA (broken down by type of vessel): 1) Jack-up preparing to move location: > Storm force weather conditions > Deficiency in watertight integrity > Stability condition outside allowable limits > Cargo poorly secured making the situation a hazard > Defect in the towing vessel(s) 2) Towing vessel: > Defective steering, propulsion or winch system > Insufficient bunkers or lubricating oil to complete the voyage > Hull damage > No spare tow line > Tow lines damaged or defective 000022 > Inexperienced master and crew > Lack of navigational equipment > Insufficient power to perform the tow 3) Cargo barge: > Damage or defect to the structure > Damage or defect to the two gear > Insufficient intact stability > Cargo insufficiently secured so as to be a hazard when subjected to “storm” loads > Barge overloaded 4) Semisubmersible: > Hull damage > Loading condition, transit and storm draughts outside stability limits > Cargo stowed or insufficiently secure so as to be a hazard > Ballast control system defective > Mooring system inoperative > Towing gear defective or deficient As stated above, these are not a comprehensive list of reasons. The complexity of any particular operation will dictate the actual circumstances where withdrawal of a CoA may take place. A number of examples to clarify the situation: A tug contracted to tow a loaded cargo barge has insufficient bunkers to complete the voyage by virtue of contamination in the fuel tanks, a circumstance that was NOT disclosed to the attending surveyor on departure. A cargo barge chartered to take a given cargo is found to have towing arrangements and equipment which fall short of the required standard even though the specification of the barge as presented by the owner indicate otherwise. 000023 Before we move on, there is the matter of the Limitation of Approval. A warranty company will lay down very specific points regarding approval. These will include but not be limited to the following list: > A CoA is issued for a specific towage, voyage or operation > A CoA is issued based on external conditions observed by the warranty surveyor of any machinery, equipment or the hull without removal, exposure or testing of parts > A CoA shall not be deemed or considered a certificate of seaworthiness > A CoA for a towage or voyage does not include any moorings prior to the start of the towage or voyage or at any intermediate shelter, bunkering or arrival port unless specifically approved. > There is no responsibility on the warranty company for the actual conduct of the towage or voyage, this is the sole responsibility of the master of the tug or vessel > The towage is deemed to have been completed when the tugs are disconnected > The CoA covers the surveyed items within the agreed scope of work only.( The student will see here how important the content of the scope of work is to the whole venture.) The next following chapters will work through the approval process and procedures that a marine warranty surveyor in the offshore industry will find himself engaged in, in the different areas of his work. The large warranty companies have, over time, developed guidelines for offshore operations which have been tried and tested. They have worked with the regulators, authorities and organisations that operate in the offshore industry to produce these guidelines that comply with all their required rules and regulations. SAQ What are the specific clauses in the Marine Insurance Act referring to warranty work in the offshore industry and what is the content of these clauses? 000024 Chapter 2 2.0 Specialised Marine Transportation This chapter looks at the specific areas that the warranty company will look at when involved in these specialised marine transport modes. The offshore oil, gas and energy sectors are very much of a specialised nature. The very quantum of value in the assets in these sectors dictates the amount of evaluation that is required for approval to cover every possible scenario in the proposed operation. 2.1 The Approval Process In all insurance warranty situations there will be a scope of work leading to an approval before the signing and issuing by the warranty surveyor of a CoA. The importance of the content of this scope of work has been highlighted in chapter 1. The approval process is carried out so that the warranty company in their judgement and opinion can confirm that all reasonable checks, preparations and precautions have been taken to keep risks within acceptable limits and an operation may proceed. In the approval process the warranty company and warranty surveyor will consider the following points: > history, condition and documentation of the tow or cargo > voyage or towage route, season and design environmental conditions, refuge points > capability of the vessel or barge to carry the cargo Typical flat top cargo barge > vessel, barge or tow motions > strength of the tow, cargo, seafastening and cribbing > stability of the vessel, barge and tow 000025 > towing resistance and bollard pull requirements > towing vessel specification > towing connections and arrangements > weather protection of the tow and cargo > arrangements for receiving weather forecasts on route > the transportation or towing manual A modern supply vessel (PSV) with the new generation X- Bow concept A large modern anchor handling tug supply vessel (AHTS) Far Sapphire 000026 Owner’s specification for the Far Sapphire Two significant points to note on this specification are the bollard pull of 232 tonnes and the service speeds of 12 to 18 knots. A service speed of up to 18 knots is high but at that speed the fuel consumption would also be very high. As can be seen, it goes from 23 tonnes per day to 78 tonnes per day. 000027 If the approval is for the onload/offload operations of a self floating cargo onto a semisubmersible vessel or barge the following will also be considered: Mighty Servant 1, a semisubmersible vessel with the MODU Thunderhorse which is classed as a self-floating cargo > location details, water depths, tidal conditions and meteorological exposure > vessel or barge moorings > stability and ballast conditions > cribbing positions > towing and handling arrangements for the cargo > cargo positioning arrangements > reactions between vessel/barge and cargo > weather limits for the operation 000028 2.2 Certificates and Documentation The document requirements will vary depending on the particular structure, vessel or marine operation, this will be determined by the warranty company in advance. The certification requirements will also be dictated by any international legislation and/or standards. If any certification is required to perform the proposed operation then these must be identified by the warranty surveyor. Principal Documentation 000029 Principal Documentation continued 000030 The following table gives the required documents and certificates by class of vessel and /or towage operation. Required Documentation GL Noble Denton 000031 An important document that must be in place for all transportations or tows is the Transportation or Towing Manual. This document has specific reference to the following: > providing the master with the key information required to execute the tow including information about the cargo and the route > it describes the structural and any other limitations of the cargo > it summarises any contingency plans in the event of an emergency > it gives the approving bodies the information they require > it defines the responsibilities of the different parties, handover points and reporting lines The following list shows what a warranty surveyor should expect to find in the manual and includes information required by the tug master. The results of calculations and other required documents may be in separate manuals but must be referenced in the Towing Manual. > the cargo, its destination, who for and why > full description of the cargo > proposed route including all way points, bunker stations, expected departure date and tow speed > metocean conditions for the expected departure date > any limiting conditions including roll, pitch, period for the tow, weather forecasting and routeing arrangements > contact details of all involved parties > reporting routines, to whom, when and content of a report > ballast conditions and stability with calculations and GZ curves > calculations for the motions, accelerations, longitudinal strength and strength of seafastenings, cribbage and grillage > arrival details, contacts, field plan > contingency arrangements > drawings to include, cargo, GA, stowage plan, towing arrangement, cribbage/grillage arrangement, load-out/discharge plan, seafastening arrangement, guidepost detail > reference documents > tug bollard pull calculation ( if required) > tug specification 000032 2.3 Multiple Towages Towage transportations can often be made up of different towing configurations which may involve more than one tow, more than one tug or more than one towline. The warranty surveyor must be aware of the potential problems with multiple tows. The principle considerations are: > manoeuvring difficulties in close quarter situations > difficulty with reconnecting towlines following a breakage > water depths for the deeper and longer catenaries Multiple tows are only considered for approval depending on area and season. The warranty surveyor will be required to carry out a risk assessment. The following configurations are the most common ones that a warranty surveyor must be conversant with. The warranty surveyor must also be aware of the appropriate areas and seasons under which approval may be considered. Double tows Two tows connected to the same tug with separate towlines with each towline on a separate tow winch drum. A spare towline must also be carried. Used in benign areas, for short tows under very good weather forecast conditions and providing there is sufficient water depth for the duration of the tow route which allows for the second catenary. Tandem tows Two or more tows in series behind one tug, each tow connected to the stern of the preceding tow. Usually used in very benign areas or in ice as the tows will follow each other. In ice the tow lines are kept short, usually above the water. Parallel tows Two or more tows using one towline. The second tow or subsequent tows are connected to a point on the tow line ahead of the preceding tow. Usually only considered in extremely benign areas and subject to increased safety factors for the capacity of the towing arrangements. Two tugs in series towing one tow The leading tug connected to the bow of the second tug. Usually only considered where the lead tug is smaller in capacity and used to aid the manoeuvrability of the main tug. 000033 More than one tug towing one tow Each tug connected with a separate towline with a pennant or bridle to the tow. This is considered an acceptable method as long as consideration is given to the compatibility of the tugs with respect to their power and capacity. Three tugs is considered the optimum configuration although larger numbers have been used on occasions for towing larger structures. Multiple tow of a concrete gasification plant Tandem tow of cargo barges 000034 2.4 Manned Tows Manned tows are usually restricted to situations where the use of a riding crew will significantly reduce the risks to the tow, e.g. mobile offshore drilling rigs, roro vessels, ferries and passenger ships. When a riding crew is employed on a tow there must be sufficient marine personnel to operate the essential equipment to be carried and to execute the duties as laid down by the warranty company. Any riding crew, regardless of the warranty requirements, must be within the flag state limits for life saving appliances and approval must be sought before commencing any operation. Underwriters must also be informed if a significant number of riding crew are involved. The health and safety of the riding crew must be assured at all times and the warranty company must carry out a risk assessment. International regulations must be adhered to regarding accommodation, food, lifesaving appliances, pumping arrangements and communications. As we stated above, there has to be a minimum complement of safety equipment on a manned tow not withstanding SOLAS or any international regulations concerning safety. The warranty surveyor will have to verify that all the required equipment is on board, in good condition and in date. All the riding crew must have basic training in the use of this equipment and at least one member of the riding crew must hold a radio operator’s licence. Minimum equipment > Certified life rafts on each side for all the crew with adequate launching facilities and access to the water. > Four (4) lifebuoys on each side, two with lines and two with self igniting lights > Approved life jackets for all on board plus 25% extra > Survival suits for all crew if required for the area of the tow > First aid kit > Fire fighting equipment, independent pumps, hoses and portable fire extinguishers > Six (6) parachute distress flares and six (6) hand held flares > A signalling lamp with battery > Two (2) portable VHF radios with marine bands > At least one hand held GPS ( Global Positioning System) > GMDSS radio (Global Maritime Distress and Safety System) 000035 > Charts covering the voyage > One EPIRB (Emergency Position Indicating Radio beacon) > Two (2) SARTS (Search and Rescue Transponders) > Line throwing and/or heaving lines During the voyage the riding crew must comply with the requirements to complete certain routines and make appropriate reports as well as keep a daily logbook of activities and events. Typical routine activities to be carried out Inspect towing arrangements and navigation lights Inspect all seafastenings and critical structures Adjust all seafastenings or lashings as appropriate Sound all bilges and spaces on a regular basis Record and continue to check any unusual ingress of water and report same Pump out this ingress of water Keep in constant radio contact with the lead tug with updates of the situation, in particular any unusual occurrences 2.5 Environmental Conditions The warranty surveyor, with the assistance of the company office and appropriate personnel, will have to study the environmental conditions to assess the loads that may be experienced by the marine transportation. The transportation must be designed to withstand these loads for each phase of the operation. The design criteria for the operation must be clearly defined. It is important that the warranty surveyor considers the maximum wave action, wind and possible currents in all the geographical areas to establish the governing criteria. All marine operations are planned and designed around an operational reference period which is basically the planned time for the operation plus a contingency period. 000036 The planned period consists of: > the time involved in preparing for the departure once the decision has been made to depart and any waiting time for tides > the actual calculated time for the voyage > any time at the arrival site /port waiting for tidal conditions > if installation at a site is part of the operation then anytime required to reach a safe condition The contingency period consists of: > an allowance for a slower than predicted voyage time due to weather conditions or slow speed due to under performance of the towing vessel > the time required to reach a sheltered location/position if the operation is weather dependent and returning to shelter is part of the contingency plan These reference periods are used to determine the classification of a marine operations as weather restricted or unrestricted. Weather restricted Operations with a reference period of less than 72 hours are classed as weather restricted. In these situations the design conditions may be set independently of the extreme conditions provided the following are in place: > an adequate frequency and duration of weather windows > dependable weather forecasts > the operation is only started with an acceptable weather forecast covering the reference period > a full risk assessment has been carried out > adequate marine procedures are in place 000037 In exceptional cases a reference period greater than 72 hours may be classed as weather restricted in which case the following must apply: > an adequate refuge shelter must be within 48 hours steaming at any stage of the operation > weather routeing must be employed and forecasts available at regular intervals with weather warnings > management resources and lines of authority are available to monitor decisions about sheltering > a risk assessment must be carried out Unrestricted Operations with a reference period greater than 72 hours are classed as unrestricted The length of time of exposure to extreme conditions is dependent on the length of time on any stage of the route where these extreme conditions are possible. The shorter the exposure time the probability of experiencing extreme conditions is also reduced. It is possible to adjust the extremes based on the exposure times which take in to consideration the following: it is assumed that the initial 48 hours is covered by a reliable weather forecast and excluded how mush the speed of the operation is reduced by taking in to consideration the monthly mean wave heights along the route the speed of the operation takes in to consideration the mean currents a contingency of 25% of the time is added ( allows for adverse weather, tug breakdown and other operational problems) a minimum exposure time is considered, usually three (3) days The speed at each stage of the voyage is calculated using the following formula: Hm is the monthly mean wave height b is the stopping wave height for a barge or ship, typically 5m for a barge and 8m for a ship The calm water speed is multiplied by the factor F to find the sector speed. F = 1 { H m }2 b 000038 Example: A barge being towed at calm weather speed of 5 knots Hm for the sector = 3m b = 5 (for a barge) It has to be considered that the values of the wind speed or significant wave height in a particular sector of the route many not be exceeded. This is expressed as a cumulative frequency distribution. As an example, the Weilbull distribution, which is used in probability theory and statistics, is a continuous probability distribution. It is beyond the scope of this unit to venture into the theory behind such a distribution. It is also possible to use this formula is to perform tow simulations. These can be very realistic using variation of speed due to weather, currents and weather avoidance through routeing services or using safe shelters. 2.6 Motion Response The warranty survey will take account of the motion response on design criteria. The design motions can be derived in one of three ways: motion response analysis, model tank testing or using default equivalent motion values. Motion response analysis The motion analysis will include all relevant ranges up to the design wave height for the severe areas of the proposed route. The choice of range should be considered which should be applicable to the geographic area and Hsig of the design sea states. The maximum extreme responses are to be based on a 3 hour exposure period. The range of periods associated with seastate can be calculated in two ways. This unit will only consider the simplest method in which the peak period for all sea states considered should be varied as: Hsig is in metres Tp is in seconds F = 1 { 3 }2 = 0.64 5 Speed for the sector = 5 0.64 = 3.2 knots (13.Hsig) < Tp < (30.Hsig) 000039 The effects of swell have to be considered. The analysis must consider the different headings at zero speed: ahead, off the bow, on the quarters and astern. The effects of free surface in respect to the application of corrections to reduce the metacentric height (GM) and so increase natural roll are not accepted. The effect of cargo immersion increasing the metacentric height and so reducing the roll period should be considered. To aid the warranty process there are computer programmes available to carry out these analyses. It is essential that any computer programme is properly validated and that information is made available to the warranty company. Tank model testing is also used in some cases to determine design motions. The tests must be approved to show their integrity. The information of loads, motions or accelerations determined from these tests can only be used if ten or more similar tests or greater are conducted to ensure any discrepancies between tests can be accounted for. If neither of these methods is available then, as long as the operation is of standard configuration, default criteria may be used subject to certain considerations being met, e.g. the roll and pitch axis is assumed to pass through the centre of flotation and heave shall be assumed to be parallel to the vertical axis. 2.7 Direction and Heading Weather is always considered omnidirectional such that no reduction in design seastates for the quarters shall be considered for: > any operation where the default criteria is used > single tug tows or voyages where vessels do not have redundant propulsion systems > any operation where the design conditions on any sector are effectively on the beam or on the quarter for a long period of time > any towage in a tropical storm area or season > any unmanned towage > any operation where the vessel does not have sufficient redundancy to maintain a heading Reduction for non-ahead cases may be considered for: > manned, multiple tug tows where a breakdown of a tug or breakage of a single tow line will not compromise the operation 000040 > voyages by self propelled vessels with full redundant capabilities, this is defined as having: • two or more independent engines • two or more independent fuel supplies • two or more independent power transmission systems • two or more independent switchboards • two or more independent steering systems • and being able to maintain a heading in all conditions including the design storm Any vessel not complying with ALL these criteria is not considered as redundant. The warranty surveyor in this situation would carry out a survey to determine whether a vessel can be considered as being fully redundant. If there is to be a reduction in seastate, a risk analysis must be carried out by the warranty company. 2.8 Loadings The structure of all components of the cargo or tow, including the legs, hull and housings of a selfelevating unit, shall possess adequate strength to resist the loads due to the calculated motions and wind. The cargo shall posses sufficient strength to withstand the local cribbing and seafastening reactions. Load cases shall be derived for each heading by adding fluctuating loads resulting from wind and wave action to the static loads resulting from gravity and still water conditions. The following static and environmental loadings are considered the most important: F1 loading caused by wind heel and trim angle F2 loading caused by surge and sway F3 loading caused by pitch and roll F4 loading caused by the gravity component of pitch and roll F5 loading caused by direct wind F6 loading caused by heave acceleration F7 loading caused by wave induced bending F8 loading caused by slam and the effects of immersion S1 loading caused by the gravity effects of the most onerous ballast condition to be encountered on the voyage 000041 There are three methods used to determine the design loadings: Model test measurements By a reduction of 10% to the fluctuating load cases F1 through F8 which combine wind and wave effects By combining loads by calculation F(1hr) = Loads based on 1 hour mean wind speed F(1min) = Loads based on 1 minute mean wind speed Longitudinal bending needs to be considered if the following apply: the towed vessel is not a classed seagoing vessel or craft the cargo is longer than about ⅓ of the length of the barge or vessel the cargo is supported longitudinally on more than two supports the seafastening design allows little or no flexibility between cargo and barge (as an example, a steel jacket may be stiffer than the barge and so will reduce barge deflections and the cargo will undergo more stresses) Consideration has to be given to cargoes that may overhang the barge and encounter immersion and possible wave slam. The loads acting on grillages, cribbing, dunnage, seafastenings and components shall be derived from the loads acing on the cargo as determined from the previous calculations. 2.9 Friction and Seafastening Design A warranty surveyor, when considering cargo weights, overhangs, cribbing and seafastening arrangements, will take in to account the frictional effect. This may contribute to the seafastening restraint. To assist the surveyor the following table has been devised that gives the maximum friction coefficient that can be used and the minimum seafastening force. S1 + F1 (1hr ) + F5(1hr ) + { [ F2+F3+F4+F5+F6+F7 ]2 + [F1(1min ) + F5(1min ) – F1(1hr ) – F5(1hr )]2} 000042 Maximum allowable coefficients of friction and minimum seafastening forces GL Noble Denton Frictional coefficients can only be used under certain conditions: they cannot be used if the load computations are based on default criteria friction forces are computed using normal reaction between vessel and cargo the cargo is supported by wood dunnage or cribbage – steel to steel friction is NOT allowed overhang is determined as the distance from the side of the vessel to the extreme outer side of the cargo for wood cribbing there are more detailed requirements depending on the size of the cribbing, the basis being that seafastenings must have sufficient flexibility to allow a movement of at least 2mm without failing the minimum allowable seafastening force is the minimum value of seafastening restraint 000043 2.10 Seafastenings By definition seafastenings are any support structure including grillage, cribbing, dunnage and welded connections to the vessel or barge. They must be designed to withstand the computed loadings as calculated for the particular operation. They must be capable of taking the stresses caused by the longitudinal bending of the barge or vessel in a seaway. Suitable seafastenings for longitudinal bending include chocks, pitch stops, vertical supports and an integrated structure. Cribbing on semi-submersible vessel Black Marlin Specially constructed seafastenings 000044 Grillage and seafastening design is influenced by the load out method. Cargoes lifted on or floated on are usually supported by timber cribbing. Cargoes on skids usually remain on the skids and trailers will require a grillage structure higher than the minimum height of the trailer. Welded steel fastenings are always the preferred method but will depend on the actual weight of the cargo. Small loads, under 100 tonnes, will often still be secured using chains and wires with some form of tensioning device, such as chain tensioners or turn buckles. If the barge is unmanned it is not recommended to use wire lashings as they will require constant tensioning. All lashing and securing must be inspected during the voyage to check tensions and to adjust if required. If the surveyor has any doubts about the lashing and securing of a particular cargo he can refer to the IMO Code of Safe Practice for Cargo Securing and Stowage for guidance. The design load for chain lashing must not exceed the Working Load Limit ( WLL) or Safe Working Load (SWL) of the chain. If the WLL or SWL are not available then the Breaking Load (BL) BL/2.25 is to be used as the design load. All connections to the deck of a barge or vessel must be carefully considered and no assumptions made as to the suitability of a structure, in particular where tensioners are involved without calculations being made to verify such connections. It is not acceptable to have tensioner connections landing on doubler plates. It is good practice when welding connections to the deck that this is done with the barge or vessel at her operational draught. If the cargo is going offshore then the seafastenings should be capable of release in stages. Eye to jaw turnbuckle Typical lever chain binder 000045 Grillage being installed on to the deck of an offshore supply vessel Wooden cribbing or dunnage must have sufficient material to provide adequate distribution of the load to the underside of the cargo and the deck of the barge or vessel in accordance with the static and the computed design loads. The nominal bearing pressure should not exceed 4 N/mm2 for softwood. This pressure is calculated using the deadweight of the cargo and the computed design loads. The type of timber used should preferably withstand the computed pressures without crushing. It is the norm to use a hard wood main structure topped with a soft wood layer which acts as packing. When using random dunnage to support a flat bottomed cargo then the cribbing pressure should not exceed 1 N/mm2. Grillages must be constructed of high quality steel work with material certificates and Nondestructive Testing (NDT) certification and its structural strength assessed using recognised methods under the Load and Resistance Factor Design Code (LRFD) or safety factors for Working Stress Design (WSD) codes. Steelwork and welds may be subject to assessment for stress and load case considerations for the normal operating case (known as the serviceability limit state, SLS) and the most probable maximum extreme load case (MPME) which is usually treated as the survival storm case or ultimate limit state (ULS). One of the regular cargoes used offshore is pipe work. This may take the form of drill pipe, casing, line pipe, piles, risers and collars. The warranty surveyor in many cases will not be required to perform a survey of this type of cargo being shipped on board an offshore supply vessel (PSV). 000046 However, when this cargo is part of a location move of a jack-up or mobile offshore drilling rig (MODU) then this will form part of the warranty surveyor’s work to assess the securing and safe stowage of this type of cargo. The amount and type of securing will depend on the type of vessel, the actual cargo, the duration of the voyage and the anticipated weather conditions. These types of cargoes are assumed to have frictional resistance to longitudinal seafastening loads. The following table gives examples of typical friction coefficients. Typical friction coefficients GL Noble Denton Pipes should be stowed fore and aft and, when stacked, the maximum height must be established. Small diameter pipes do not require chocks as long as vertical stanchions are used. Dunnage or wedges are used to chock off any spaces between the pipes and the stanchions. If the operation is weather restricted the pipe stack may be secured with chain or wire transverse lashing adequately tensioned with certified tensioners. End stops are not required as long as sufficient friction is established against any longitudinal movement. In unrestricted operations, which will include an ocean voyage, then steel strongbacks will be installed over the top layer and the bundles of pipes chocked off against these strongbacks with wooden wedges. There will be a requirement for end stops or bulkheads to stop longitudinal movement. Large diameter pipes are often chocked individually and end stops fitted. It may be necessary to fit extra restraints such as wire or chain lashings, stanchions or strongbacks. If these larger pipes are coated line pipes, great care must be taken to prevent damage to the coating. If the pipes are open ended where the ingress of water is possible, consideration must be given to the vessel’s stability and the extra stresses on the deck and pipes. If any of these are of concern then the pipes must be sealed to prevent the ingress of water. Warranty surveyors will become involved with the inspection of welds and seafastenings. In the case of a cargo that is a new structure, it has to be shown that this was constructed under a proper system of supervision, weld inspection. The main seafastenings will be visually checked and the weld sizes confirmed against the agreed design. 000047 Nondestructive testing (NDT) will be carried out by a suitable method to all structural members of a seafastening. Warranty surveyors may not carry out all these tests but will witness such tests carried out by certified inspectors. The warranty surveyor must have a full knowledge of the acceptance criteria for NDT inspections as laid down in the various industry codes such as: “Structural welding code-steel”, “Construction specification for fixed offshore structures in the North Sea” or an equivalent. As a guide, the following is the industry recommended minimum extent that NDT should be undertaken: Visual 100% Penetration welds 0 40% UT and 20% MPI Fillet welds – 20% MPI All welds to the deck – 100% MPI with additional 40% for penetration welds In all cases the extent of NDT must conform to the project specification The specification will require that in the case of critical areas or suspected poor welding then 100% inspection must take place. In the case of second hand seafastenings then the warranty surveyor must assess their suitability and condition. There must also be correct documentation to verify the grade of the steel. All second hand seafastenings should have NDT inspection reports; if not, they will be subject to a full NDT inspection. 2.11 Stability It is outside the scope of this unit to study vessel stability. This is covered in Unit 3, Naval Architecture. The warranty surveyor will always be conscious of the stability requirements when involved in any marine floating operation. The surveyor will look to his office support to carry out stability calculations by a team of naval architects on his behalf. The surveyor will then use this information to check against actual on board calculated figures to see that they comply with the requirements laid down. The intact stability range is defined as the range between 0° heel or trim and the angle at which the righting lever (GZ) becomes negative. The minimum values of intact stability range are shown in the following table (on the following page): 000048 Intact stability range GL Noble Denton Metacentric height (GM) must be positive throughout the range of intact stability as above. The initial metacentric height, GM0, must include a margin for computational inaccuracies. A GM0 of 1m is expected but in no circumstances should this be less than 0.15m. The effects of free surface must be considered in any calculations. In ice conditions the surveyor must take in to account the effect of accumulated ice build up on structures. It is accepted under warranty terms that any towed object, cargo barge, MODU or structure towed on their own buoyancy, must have positive stability with any one compartment flooded. On many occasions the buoyancy of the cargo will have been included in the calculation to meet stability requirements. If this is the case then the loss of cargo will be deemed a damage scenario. In some cases this loss of stability criteria from a one compartment flooding is not possible to achieve The following structures would have difficulty achieving this without design changes: > Concrete gravity structures > Submerged tube tunnel sections > Bridge pier caissons > Outfall or water intake caissons 000049 In these particular cases, if certain conditions are met, the damage stability may be relaxed provided the tow is of short duration, is a one-off tow, conducted under controlled conditions and precautions are in place as follows: > vulnerable areas should be reinforced or fendered > vulnerable areas are clearly marked > projecting hatches, valves and pipelines are protected > emergency towlines are provided with trailing pick-up lines > emergency pumping equipment is on board > any possible leaks in the ballast system are kept to a minimum > ballast intakes and discharges must be protected or banked off > all vulnerable areas are notified to the tug masters > a guard vessel is employed to warn off approaching vessels > a risk assessment has to be undertaken and the risks shown to be acceptable The warranty surveyor’s scope of work in this particular type of operation will include checks to verify these conditions are being met. In the Naval Architect Unit the righting arm (GZ) and areas under the righting moment curve have been explained with regard to intact and damaged conditions of the vessel. In warranty work we have to also consider what is known as the wind over turning arm. This has been introduced on to the GZ curve diagrams as the wind overturning arm as per the following figures: In both intact and damaged conditions the area under the righting moment curve must not be less than 40% in excess of the area under the wind overturning curve. The wind speed for intact wind overturning calculations is the 1 minute wind design speed as used in section 2.8. If this data is not available then 50m per second is used. In the damaged condition the wind speed used for overturning moment calculations will be 25m per second or the wind speed used in the intact condition, whichever is less. 000050 Intact condition wind overturning criteria GL Noble Denton Damaged condition wind overturning criteria GL Noble Denton The warranty surveyor must take in to consideration the draught and trim of vessels, in particular vessels, barges and structures being towed. If a vessel has a loadline certificate then the draught must never exceed the appropriate draught. Barges and large structures like Floating Production Storage and Offloading (FPSO) vessels’ draughts must be selected to minimise slamming at the forefoot, give good directional control and make allowance for the trim caused by the towing wire. 000051 The following table gives guidance on the minimum draughts and trim for various lengths of vessel under tow. The actual draught and trim will be discussed between the warranty surveyor and the tug master. Minimum draught and trim Watertight integrity is of considerable concern to the warranty surveyor in particular with MODUs. The surveyor will check the integrity by visual inspection, carrying out a chalk test, hose test, air test or ultra sonic test as he deems appropriate. The following are the specific areas that the warranty surveyor will check: > all hatches, gooseneck air pipes, ventilators, and sounding pipes must be carefully checked by the surveyor to confirm their correct operation and watertight integrity > outboard accommodation doors for correct operation and weathertight integrity, dogs and seals must be in good condition > watertight doors in holds, ‘tween decks and engine room spaces must be in good condition and closed > portholes must be checked as watertight > any window that may be exposed to the sea and wave action must be plated over > all tank top and deck manhole covers and seals must be in place and securely bolted down > all overboard valves to be closed and locked > all holds and void spaces to be checked and pumped dry before departure > any other spaces deemed necessary to check before departure must be sounded and either left empty or pressed up 000052 As a summary, the following practical points will be considered by the warranty company and surveyor when selecting a barge or vessel to conduct a specific marine operation: > is there adequate deck space for all the cargo and additional equipment that may be required for the tow? > does the barge or vessel have adequate intact and damaged stability? > does the barge or vessel have adequate freeboard? > if there is a floating load out, is there sufficient water depth? > if there is a submerged load out, is there sufficient water depth? > is there sufficient deck strength? > do seafastenings require welding near oil tanks? > if a barge, is there emergency towing connections, recovery gear, pumping equipment, mooring equipment, anchors, lighting and sufficient access ladders on board? > do the calculated response motions cause any overstress to the cargo? > is all the required equipment and machinery on board in good operational condition? > does the barge or vessel have all the necessary certification and all in date to cover the intended voyage? As in all marine operations the actual precautions and procedures required will depend on the situation. This is where the warranty surveyor, being on site, comes in to his own, using his knowledge and experience to assess accurately the risks and put in place the necessary physical and operational procedures and precautions. 2.12 Voyage Planning As we have seen previously a Certificate of Approval (CoA) is based on the agreed conditions both physical and operational in nature. These agreed conditions can not be deviated from during the course of the tow or voyage without justifiable cause and, where possible, with the prior agreement of the warranty company. This brings in the requirement to have a detailed voyage plan that will cover all aspects of the proposed tow and voyage. The warranty company and surveyor will be very much involved with the production of an acceptable plan to which all parties will have to agree and conform. The plan must be developed in line with the International Safety Management Code (ISM). We will now look at the specific areas that must be considered in the development of a voyage plan. 000053 Voyage routeing The route must be planned in conjunction with the tug master(s) or vessel master which will take in to account the vessel or tug’s capacity and fuel consumption, weather conditions, tide and current conditions, good navigation and seamanship. In today’s world we have to seriously consider piracy as many of the areas affected, e.g. Nigeria and the Middle East, are areas through which slow moving tows used in the offshore industry are regularly passing. There will have to be consultation with underwriters and all parties that have a vested interest in the venture. They must agree on the route and all precautions that may have to be taken to protect their interests and the safety of the crew. Weather routeing and forecasting Receiving weather forecasts must be started well in advance of the proposed departure date and time, this is usually at least 48 – 72 hours. In the majority of voyages, especially for long tows, the services of an independent reputable weather routeing company will be part of the conditions of the CoA. In any case, before departure it is prudent to have a second independent forecast available. This does not detract from the vessel or tug masters obtaining their own weather forecasts in line with their responsibilities and good seamanship. It is paramount that weather conditions take in to account the capabilities of the tow at departure or any port or shelter during the voyage as well as the characteristics of the tow, wind directions and, in particular, any hazards that may affect the route and response of the tow operation. Departure report It is incumbent on the owners to provide the warranty company and the warranty surveyor with a departure status report. The report will contain the following: the appropriate documentation referred to in section 2.2 lightship weight ballast, consumables and cargo plan departure displacement and draughts vertical centre of gravity (VCG) metacentric height (GM) as calculated and confirmation it is within allowable limits righting lever GZ curve and confirmation it is within limits if the tow is a vessel then longitudinal bending and shear forces must be within allowable limits 000054 The warranty surveyor will verify all these conditions and confirm that the tow is up right and at the correct draught and trim. It is only then that the warranty surveyor will issue a CoA. Safe havens A priority for the voyage plan will be the availability of ports of refuge, sheltered areas or places close to the proposed route where the tow may hold for a period of time in safety. These places must be agreed prior to departure as they form part of the voyage plan and conditions of warranty. It may also be necessary to have to obtain authority to use any, or all, of these places. Bunker facilities As in any towage operation the ideal situation is for the tugs and/or vessel to have sufficient bunkers to complete the voyage with an acceptable amount in reserve. In the event that this may not be possible then contingency bunkering plans should be in place. These plans will be part of the warranty conditions for the voyage. Acceptable bunkering plans may include: > if more than one towing tug is involved, one tug may be released to proceed to a bunker port, subject to distance and favourable weather conditions > the towing tug may be substituted by another towing tug as long as that tug is of equivalent capacity to allow the original towing tug to proceed to a bunker port, again subject to distance and weather conditions and a favourable weather report > bunkering at sea from another vessel as long as the weather is calm and strict procedures are in place Pilotage The master will use the services of a pilot when and where appropriate. Record keeping and communications A detailed log book will be kept of the voyage, recording all events; this will be over and above any log books or records required to be kept by statute. After departure regular communications must be kept with the warranty company updating them of the progress of the voyage, any events recorded and actions taken if necessary. Any deviation to the agreed towing arrangements must also be notified to the warranty company. If any situation arises which requires emergency action, including diversion to a safe haven, then the warranty company must be informed. This will give the warranty company the opportunity to advise on the validity of the CoA to enable the voyage to continue and in some circumstances there may be a requirement to re-validate the CoA before the voyage can resume. 000055 Cargo, barge, vessel inspections If the tow is manned or is a self propelled vessel then the routine inspections as outlined in section 2.4 should be followed and recorded. The records should include any findings as a result of the inspection and any corrective measures that had to be undertaken, e.g. the tightening of lashings, bilge soundings. If the tow is unmanned then the tug crew should board on a regular basis and carry out the same inspection routine as if it was manned. To alleviate the excessive movement of and damage to the cargo or the vessel, the master should exercise good seamanship which may involve alterations of course and speed or both. Towmaster and tugs The Towmaster is in overall charge of the towing operation which includes the navigation of the tow and the towing arrangements. Nothing in the CoA or voyage plan or any other document associated with this marine venture will override the authority of the master who is in sole command of his vessel in accordance with maritime law. It is important to realise that only the tugs named on the CoA can undertake the specific towing operation and voyage. These tugs, or tug, must remain with the tow throughout the operation. If for any reason, except in an emergency or it is part of an agreed bunkering procedure, there is a requirement to change a tug then the warranty company must be informed. The replacement tug must be approved by the warranty company. This situation will require a new CoA to be issued. Ballast and ballast operations Under international law IMO Ballast Water Convention 2004 (res A.868), all vessels flagged under signatory states to IMO must keep records of ballast operations. These vessels must have on board a ballast water management plan. This plan must be available for inspection by any port state authority. Vessels involved in a marine operation being addressed in this unit will often have a requirement to change their ballast condition. There may be local laws that govern such operations and these must be consulted before attempting any ballast changes. The USA have many state laws which must be strictly adhered to, failing that heavy fines can be levied. Assessment of any local laws that may affect the operation will form part of the voyage plan development prior to departure. Restrictions As in any marine voyage there will be restrictions that have to be considered and allowed for to complete the venture in a safe and seamanlike manner. We will look at the most common, although each individual situation may bring up a peculiarity and this is where the warranty surveyor must use his skills and knowledge to recognise something that may be out of the ordinary. 000056 Any clearances for a particular voyage will be assessed on the route proposed to be taken with the following being taken in to account: > environmental conditions > length of areas of restricted manoeuvrability > course changes in the areas of restricted manoeuvrability > profile section of the area of restricted manoeuvrability and the shape of the structure > capability of the tugs Under keel clearances will take into account the following but in all cases a minimum margin of not less than 1 metre or 10% of the maximum draught will apply; vessel movement, roll, pitch, heave squat towline pull structural bending of the tow heel due to wind effect negative surge heel, trim, and any changes in draught bathymetry tolerances water density changes errors in measurements tidal effects If tidal effects are a critical part of any stage of the voyage then safe holding areas must identified where adequate under keel margins can be maintained at all times during the waiting time. Any anticipated delay times for tidal effect will become part of the overall reference period. If the tidal effect is considered very critical then depth measurements should be made prior to confirm actual depths. In cases where the underwater or channel side clearance is critical then a recent survey report not less than three months old must be consulted. If such recent information is not available then a survey of the route must be undertaken This will involve the survey of the route of a least 5 times the maximum beam or a minimum of 500 metres. The use of approved industry equipment such as side-scan sonar and bathymetric data should be available. 000057 The minimum channel width along the inshore stages of the route, keeping in mind the under keel clearances and air draught requirements, will be three times the maximum width of the towed object allowing for yaw. Air draught Overhead clearances for bridges and power cables are calculated with a minimum margin of not less than 1 metre plus any allowable tolerances for the elements in the section above. Power cables require a “spark” gap, this information must be acquired in advance from the power company as they will have their own clearance requirement. This margin is on top of the minimum margin applied. It has to be noted that the catenary of a power cable will actually vary depending on the power flow in the cable. The lowest catenary level must be used in all cases. This chapter covers the basic principles of the involvement of the warranty company and warranty surveyor. The following chapters look at more detailed requirements that apply to specific operations. SAQ Statutory trading certificates are essential to any marine transportation. What are the certificate requirements for a semisubmersible heavy lift vessel carrying a Mobile Offshore Drilling Unit (MODU) on an ocean voyage? 000058 Chapter 3 3.0 Towing Vessel Selection The tug(s) used for any towing operation must be approved by the warranty company. The tug(s) will be subject to a survey by a warranty surveyor. The survey will assess the suitability of the tug(s) to perform the proposed tow, its capability, condition, towing equipment, manning, fuel capacity and documentation. The manning will particularly assess the experience of the master, officers and crew in towing operations. The tug(s) must fully comply with the bollard pull requirements to the extent that if there is any doubt then a practical bollard pull test may be required to confirm the stated bollard pull. (see section 3.1) The warranty company will require certain information to be available prior to any survey to confirm the initial suitability of the tug, this information will include: > a specification sheet > general arrangement plans > specifications of the towing winches > specifications of the towing equipment including chains, bridles, towing wires, pennant wires, towing shackles, connecting links > copies of the following certificates: (or sighted by the surveyor at the time of survey) - certificate of registry - classification certificate - load line certificate - ship safety equipment certificate - ship safety radio certificate - ship construction certificate - manning certificate - international oil prevention certificate - safety management certificate - international ship security certificate 000059 60 IIMS - Call +44 (0)23 9238 5223 or visit www.iims.org.uk - ballast water exchange certificate (if required) - bollard pull certificate - an approved stability booklet Smaller tugs under 500gt may not be required to have all these certificates Warranty companies categorise towing vessels depending on the weather, geographical area and type of towage. To explain this system and define the categories we will make reference to an actual warranty company. In this case we have chosen to look at GL Noble Denton. The following table shows these categories: Towing vessel categories GL Noble Denton We will now look at the requirements for each category. The actual towing equipment requirements are covered in section 3.2 Salvage tug (ST) > approved for all towages within their bollard pull limits in all areas subject to any ice classification > equipped with two main tow wires and a spare tow wire > adequately manned > of a design to be capable of undertaking towages in all geographical areas > have a minimum bunker capacity of at least 35 days consumption at 80% MCR 000060 > equipped with a workboat > plus any additional salvage , lifting equipment, pumps, portable generators, air compressor, welding/cutting gear, damage control materials and tools, spare parts Typical ocean salvage tug Unrestricted (U) > approved for all towages within their bollard pull limits in all areas subject to any ice classification > equipped with two main tow wires and a spare tow wire > adequately manned > of a design to be capable of undertaking towages in all geographical areas > equipped with a work boat, in this case, the man overboard boat may be used as a work boat as long as the flag state approve Coastal (C) > approved for all coastal towages within the limits of their bollard pull subject to any ice classification (coastal towage is defined as routes for which a tow can safely reach a place of safety within the period of a reliable weather forecast or within benign weather areas) > equipped with a main tow wire and a spare tow wire 000061 > adequately manned > of a design to be capable of undertaking towages in relevant geographical areas > equipped with a work boat, the man overboard boat may be used as a work boat as long as the flag state approve Restricted (R1) > approved for assisting towages within their bollard pull limits in all areas subject to any ice classification > equipped with a minimum of one main towing wire > adequately manned as per R1 requirements > seakeeping ability as per R1 requirements > if used as the lead tug or only tug she must be equipped with a workboat, the man overboard boat may be used as a work boat as long as the flag state approve Benign area towages (R2) > approved for towages within the limits of their bollard pull and within the geographical limits of benign areas > equipped with a main tow wire and a spare tow wire > adequately manned > of a design to be capable of undertaking towages within the geographical limits of benign areas > if used as the lead tug or only tug for a particular voyage she must be equipped with a work boat, the man overboard boat may be used as long as the flag state approve Restricted benign area towages (R3) > approved for assisting with towages within their bollard pull limits and the defined geographical limits of benign areas > equipped with a minimum of one tow wire > adequately manned as per R2 > seakeeping ability as per R2 000062 In all these categories bollard pull is an important factor as it governs their role and ability to perform. The bollard pull is also an element for calculating the Towline Pull Required (TPR). TPR is related to the continuous static bollard pull of the tug(s) proposed bollard pull: where Te = the tug efficiency in the sea states considered as a % (BP x Te/100) is the contribution to TPR of each tug Σ means the aggregate of all the tugs assumed to contribute, only those tugs connected that are capable of pulling in the forward direction are assumed to contribute Tug efficiency depends on the size and configuration of the tug, the seastate and the actual towing speed achieved. Te may be estimated from the following table for a good ocean going tug. Values of tug efficiency Te GL Noble Denton It is also possible to represent these efficiencies graphically in different sea states. Tug efficiencies in different sea states GL Noble Denton TPR = Σ(BP T e ) 100 000063 The resultant effective bollard pull in different sea states is shown in the following graph Effective bollard pull in different sea states GL Noble Denton During the selection process the warranty surveyor will also inspect other areas that form part of the acceptance and so the issuing of a Certificate of Approval. They include: main and spare towing wires stern roller radius (not to be less than 10 times the diameter of the vessel’s tow wire) the method of towline control (towing pod or gog wire) a suitable work boat (ribs with a solid deck floor are acceptable) portable VHF radios for communications with the tow (above statutory requirements) navigational equipment, lights, charts, instruments, publications for the intended tow adequate searchlights for night operations portable pump anti-chafe gear the towing vessel’s operational range, bunker storage, daily consumption 000064 3.1 Bollard Pull Tests In a situation where the bollard pull is not available it may be necessary to perform a bollard pull test. The procedure is made up of three elements: the location, the vessel and the test requirements. To be an acceptable record of test and bollard pull readings the location and location conditions must comply with the following: Location > water depth minimum 20m over 100m radius from the vessel . > the location to be clear of any obstructions within 300m > the current to be less than 0.25 kts > the wind to be less than 2.5 kts > the sea state must be calm Vessel > draught and trim at operating conditions > propellers and fuel as per operating conditions > all auxiliary equipment e.g. pumps, generators to be connected as in operating condition Test requirements > vessel stern to shore not less than 300m > good communications between vessel and gauging position > the continuous bollard pull (CBP) test to be conducted at the engine manufacturer’s rating of the maximum continuous rating of the main engines for a period of 10 minutes with the vessel on a steady heading > a maximum bollard pull (MBP) test should be undertaken with the maximum engine rating at 110% maximum rating of the engines for 5 minutes > it may be required for a specific operation that bollard pulls are assessed at different engine rpm or different engine configurations > the load cell/gauge should be certified accurate to +/- 2% and recently calibrated > if the recording equipment does not have a continuous readout facility then readings must be taken at 20sec intervals over the test period and a mathematical mean shall be used 000065 Classification societies undertake bollard pull tests and issue a test certificate. Unless there is any doubt about the ability of the towing vessel to perform to the certificate bollard pull figure then it is acceptable to accept the society test figures. In the event that a practical test or certificate is not available there are a number of rule of thumb calculations that are used in the industry. The acceptance of any results from these calculations will be based solely on the situation at the time and the polices of the interested parties involved in the operation, in particular the policies of the warranty company or underwriters. They are as follows with no priority of preference or accuracy: The Millwee method Bollard pull (BP) = F1 x brake horsepower in pounds F1 = propulsion factor: open fixed propeller = 22, open controllable (CP) propeller = 24 US Navy method Open fixed propeller - 100 shaft horsepower = 1 tonne bollard pull Shrouded propellers - 100 shaft horsepower = 1.2 – 2.5 tonne bollard pull Method three BP = 1.1 √ (brake horsepower). Add 10% for a shrouded propeller Typical stern view arrangement for a bollard pull test 000066 Typical load cell with continuous read-out attachment 3.2 Vessel Towing Equipment Requirements The warranty company will have towing equipment requirements depending on the category of tug under consideration. We will refer again to the GL Noble Denton categories as examples. Salvage tugs (ST) > two main tow wires on separate drums and one spare tow line, the MBL to be as follows: > the length of each tow line is calculated from: (subject to the tow length not being less than 800 metres) > at least 4 towing pennants not less than the main wire MBL > surge wires if supplied, their MBL will not be less than the main wire MBL > at least 12 towing shackles BP < 90tonnes = (3.8 B P ) BP 50 BP > 90tonnes = 2.0 BP L = ( B P ) 2000 metres MBL 000067 > there will be all the components onboard to make up a complete towing bridal made up of chain or chain and wire. The ultimate holding power of any leg of the bridal will not be less than as calculated from the following formulas: A tow wire log must be kept recording service history, maintenance and inspections. Unrestricted (UT) or Coastal (C) > one main tow wire and spare tow line, the MBL to be as follows: > the length of the tow line is calculated from: (for UT the minimum length will be 650 metres and for C 500 metres) It is recommended that a tow wire log is kept. Restricted (R1) > one main tow wire, the minimum MBL to be as follows: ULC = 1.23 MBL (where MBL < 160 tonnes) ULC = MBL + 40 (MBL > 160 tonnes) > 90 tonnes 2.0 BP 40 90 tonnes (3.8 B P ) BP 50 < 40 tonnes = 3.0 BP L = ( B P ) 1800 metres MBL > 90 tonnes 2.0 BP 40 90 tonnes (3.8 B P ) BP 50 < 40 tonnes = 3.0 BP 000068 > the length of the tow line is calculated from: (the minimum length in all cases will be 650 metres) It is recommended that a tow wire log is kept. Benign areas (R2) > one main and a spare tow wire, the minimum MBL to be as follows: > the length of the tow line is calculated from: (the minimum length in all cases will be 500 metres) Restricted benign areas (R3) > one tow wire, the minimum MBL to be as follows: > the length of the tow line is calculated from: (the minimum length in all cases will be 500 metres) There will also be conditions laid down as to the requirements of particular pieces of equipment as follows: all tow wires to have hard eyes (spelter sockets or formed with gusset thimbles) pennant wires must be of the same lay as the main tow wire, also with hard eyes synthetic stretchers should have a heavy duty thimble at each end (with gusset) the MBL of towing shackles or connecting links shall not be less than 110% of the MBL of the towing wire L = ( B P ) 1800 metres MBL MBL = 2.0 BP L = ( B P ) 1200 metres MBL MBL = 2.0 BP L = ( B P ) 1200 metres MBL 000069 Open spelter socket Closed spelter socket Stretchers with heavy duty gusseted thimbles Heavy duty gusseted thimble Bow type shackle D type shackle Examples of red pin shackles used in the offshore industry 000070 3.3 Towing Equipment and Connections It is normal practice to tow a barge or ship shape bow first using a towing bridle. The basic parts of a bridle system are made up as follows: Connections, connection points, fairleads, bridle legs, face plate (bridle apex), intermediate pennant, recovery system and an emergency towing gear arrangement. As an example we will look at a simple barge set up. Although the majority of tows and towing arrangements will be made up in this format it may happen that due to the type of tow, e.g. a damage scenario, that a modified towing arrangement will have to be adopted. This will obviously have to be checked for approval before commencement of the tow by the warranty company. Many damaged ships, converted ships and FPSOs are towed stern first which may require a different towing arrangement. There are cases where a bridle is not used as in multi tug tows where each tug will tow off a chain pennant and intermediate wire pennant. 000071 The following drawings shows the relevant parts of the bridle towing arrangement for a barge with a rectangular bow and an emergency towing gear arrangement that would be used on the same barge. Barge tow arrangement showing relevant parts GL Noble Denton 000072 Bridle apex or delta plate Bridle apex, delta plate, face plate or monkey plate These are all names used in the industry depending on the area you are working in. This happens throughout the offshore industry and warranty surveyors must be conversant with all the global, national and, in some cases, the local terminology in use. 000073 Barge emergency tow arrangement GL Noble Denton 000074 The emergency towing gear is provided in case of a towline breakage or a bridle failure. It may be a second bridle and pennant or made up as in the diagram on the previous page. If the system is made up then it must conform to the following: > tow connection on the centre line > closed fairleads > single length pennant with hard eyes > extension line if required > float line and buoy The tow connections, fairleads and pennant should have the same MBL as the main tow line. The pickup system should be of adequate breaking strength to break free during the recovery process. If an emergency system cannot be made up from the bow then the pennant should be coiled or flaked so that it can be pulled clear. The warranty surveyor should also consider other equipment that maybe required during reconnection, e.g. extra heaving lines, spare shackles and even a line throwing apparatus. Depending on the length or area of the tow as well as emergency towing gear there will be a requirement to have emergency equipment onboard the tow, such as: > burning and welding gear > steel plate and sections > plywood sheets and timbers of varying sizes > sand & cement, plugs, wedges and nails > tools - hammers, saws and crowbars > fire fighting equipment, PPE, and emergency lighting All this equipment must have valid test certificates where appropriate. If a minor piece of equipment does not have a certificate then the surveyor can recommend the use of oversized equipment. 000075 The tow must conform to the International Regulations for Preventing Collisions at Sea, or COLREGS as they are more commonly known. This is in respect of navigation lights and shapes. The warranty surveyor must not only check all this equipment but should consider the use of a radar reflector if the tow is low in the water. The surveyor must also consider access to the tow even if the tow is unmanned just in case a boarding party has to be deployed. This may require a steel ladder each side for long tows or a pilot ladder securely rigged may be acceptable for a short tow. The MBL of all the main towing equipment, main and spare tow lines, connections and bridle legs has to be relative to the bollard pull (BP) of the tug as follows: Towline minimum braking load (MBL) Bollard Pull Benign Areas Other Areas BP < 40 tonnes 2.0 x BP 3.0 x BP BP 40 – 90 tonnes 2.0 x BP (3.8 – BP/50) x BP BP > 90 tonnes 2.0 x BP 2.0 x BP The ultimate load capacity (ULC) of the connections, bridle legs, chain pennants, fairleads shall be calculated as not less than the following: MBL < 160 tonnes ULC = 1.25 x MBL MBL > 160 tonnes ULC = MBL + 40 The bridle legs and all connections to them shall be designed to the full value of the ULC. Fairleads shall be designed to take loadings as the tug deviates from the nominal towing direction as follows: Horizontal angle α Fairlead ultimate load capacity α < 45° ULC α 45-90° Linear interpolation with α between ULC and (0.5 x ULC) α > 90° 0.5 x ULC α = either the horizontal angle of the tow line from the nominal direction without a bridle or the horizontal angle of the bridle leg from the nominal direction 000076 Diagram defining the α angles Tow line connections should be of an approved design preferably with quick release. Smit-Brackets are an example of such a type: Typical Smit – Bracket The warranty surveyor must consider the deck handling equipment. This consists of the tow winches, gogwire, tow pod, shark’s jaws and stop pins, whatever may be fitted on the tug. 000077 McGregor Waterfall winch Hydraulic stop pins on the after deck (you can also see the deck handling cranes which run on rails) Waterfall winch Hydraulic shark’s jaws and guide pins There are also major developments in anchor handling systems such as the Triplex MDH (Marine Deck Handling) which allows the crew to carry out anchoring handling and towing operations remotely from a safe location. MDH installed on the AHTS Siem Pearl You can see the travelling gantry and the two handling cranes port and starboard. 000078 Triplex MDH 42 specifically for anchor handling operations Triplex 140 MDH for cargo deck handling In most cases the surveyor will not be required to conduct or witness equipment tests, as the certification should be up to date. If the certificates for any of the equipment from wires to shackles are not current then the surveyor must ascertain the reasons why, as this may lead to other related problems of poor management both on board and by the operating or owning company. The standards expected today by the charterers, the major oil companies or the independent oil company are so high that any lapse in operating procedures is not looked at favourably. This would then reflect on the vessel’s future employment potential. However, the surveyor should have knowledge of the test procedures and requirements for the towing winch, gogwire, guide pins and stops. Towing winches are subject to certain conditions and requirements notwithstanding the manufacturer’s correct installation of the winch arrangement. 000079 If there is a multi drum system each drum must be capable of being operated separately. The drums must have the capacity to carry the required length of tow wire. There must be a spooling device to feed the wire correctly on and off the drum. The winch brake shall prevent the tow wire from paying out when the vessel is at maximum continuous bollard pull. The brake will also prevent automatic release if there is a power failure. There must be an emergency tow wire release system fitted. There are four tests commonly conducted on winches: a stalling test, brake test, quick release test and spooling gear test. The wire used in these tests must have the equivalent MBL, diameter and lay up as the main tow wire. The test equipment, fittings and test points ashore must have a safe working load (SWL) of at least 10% above the designed maximum bollard pull. Stalling test The test is carried out in two parts: Test 1. Carried out with a full drum Test 2. Carried out with an effective drum diameter estimated to stall the winch The winch is to be hauling in while the engine power is increased, and when the winch stalls the following readings are recorded. Bollard Pull Effective drum diameter Brake test The test is carried out with a full drum of wire. A 300m wire is connected to the tow wire. The brake is applied at maximum holding capacity. The engine power is increased until CBP is achieved then the following are recorded. Bollard Pull Brake Pressure Quick release test This test is carried out with vessel towing at approximately 30% CBP and in two parts. Test 1. Heaving in the test wire Test 2. Engaging the brake 000080 Spooling gear The engine power is increased to CBP with the test wire being at least 60° to the centreline port and starboard sides. The test time should be at least one minute. The gogwire, guide /stop pins and tow pods are also subject to testing as follows: With the spooling gear disengaged the engine power is increased to CBP. The test wire should be at least 60° to the centreline to port and starboard. The test time should be at least one minute. There must be sufficient tow wire protection. This is usually in the form of chafe protectors which fit over the tow wire to protect it from abrasion. Tow wire control is in the form of a gogwire or gobwire, fixed or adjustable or a tow pod. These devices keep the tow wire aft of the turning point to avoid the tug girding. They must be fitted on the centreline of the vessel. The length of the wire or chain must be less than half the distance between the cargo rails or bulwarks. The gogwire connecting the shackle to the tow wire should be of the wide body type or a special sheave. This is an interesting photograph of a major oil company drillship under tow. It is interesting because there are actually three things shown not in conformity with good industry practice for a gogwire: 1. they are using the wrong type of preferred shackle, a D type instead of a wide body 2. the shackle is connected wrongly, it should be bow to the wire 3. there is no chafe protection in use 000081 It is beyond the scope of this unit to go any further into anchor handling operations, although a good warranty surveyor will be conversant with industry good practice as well as the understanding of the requirements for conducting safe anchor handling operations, including the requirement for good seamanship. 3.4 Stability The stability of the vessel or craft is covered by the Construction of Offshore Supply Vessels Policy adopted by IMO and the Merchant Shipping (Loadline) Rules 1966. If the towing vessel has a classification society notation as “tug” or “towing vessel” the stability booklet must contain a load condition fulfil in this notation. The warranty surveyor should sight an example to see that the condition relates to the intended voyage. If the example varies then the tug master should prove there is adequate stability including arrival fuel loads. If the tugmaster cannot show that it satisfies the classification notation then the heeling lever must not exceed 0.5 times the maximum GZ for the critical load condition. The heeling lever is defined as: The height of the wire is measured either at: the fixed gog, or the side of the rails if higher or the top of the winch (full drum) or the side rails if higher If the GZ occurs at an angle greater than 30° of heel then the GZ value for 30° should be used instead of the angle of maximum GZ The manning of the tug or vessel must be in accordance with mandatory statutory requirements of the flag state. However, the warranty surveyor in the development of the operational and voyage plan should consider additional manning requirements to fulfil the obligations of the operation and voyage in a safe and risk free manner. In this respect the practical situation of available extra accommodation has to be taken in to consideration when selecting suitable tugs and towing vessels. The table on the next page summarises the guideline requirements by vessel category when selecting a suitable tug or vessel: [0.6 Max. Bollard Pull Vertical distance between tow line and centre of the propellers] Displacement 000082 GLNoble Denton SAQ Bollard pull is an important factor for selection of a towing vessel. How would you go about determining the bollard pull when evaluating vessels for an ocean towage? 000083 Chapter 4 4.0 Special Considerations for Jack-Ups, FPSOs and Ships As with all warranty surveying the warranty company will appoint a surveyor or surveyors to a particular project based on the requirements of the project and the knowledge and experience required by the surveyor(s). In this chapter we look at three specific areas which will require special considerations for a towage. These are for jack-ups, FPSOs and ships. In each case the warranty surveyor(s) must have experience and knowledge of the particular asset being towed and how they operate. Jack-ups in particular, by their special construction, have many specific points that a warranty surveyor will consider before a CoA will be issued. As an example, the centre of gravity of the jack-up designed for a floating condition may be different if transported dry. We will look at these three individually. 4.1 Jack-Ups (see also appendices C and H) The first point is to look at a basic jack-up and its construction. The majority of jack-ups have three legs usually hydraulically or pneumatically operated but some have electric jacking systems. The principal parts of the jack-up are the drilling deck, substructure (drillfloor) and canitilever. The accommodation block and helipad are the other main parts with cranes for the transfer of drill equipment, drill tools and drill pipe. The cranes are also used for stores and other consumables to be transferred by the attending supply vessels. Three legged jack-up spudded down on location Three legged jack-up under tow legs fully jacked up 000084 The motion responses and loadings will be calculated as in the relevant sections 2.6 and 2.8. This applies to a jack-up towed on its own hull or on a barge or vessel in which the latter will be the loadings on the cribbing and seafastenings. Jack-ups towed on their own hull shall, under normal circumstances, be constructed under the rules of a recognised classification society and all certification and documentation applying to the jack-up will be available for scrutiny by the warranty surveyor. In the unlikely event of the jack-up not being in class then the following conditions will apply: The hull to be capable of withstanding the following loadings: Static loading with the jack-up afloat with all equipment on board, variable loads and legs in towage position plus Longitudinal and transverse bending obtained from the formula where Lw is the assumed wave length equal to the unit ‘s length or beam and height in metres The external plating shall have adequate strength to withstand hyrdrostatic loads due to the plating being immersed. The overall construction including the hull superstructure materials and workmanship shall be in line with industry good practice. Stress levels in the legs, guides, hull and any temporary fittings must comply with the levels considered in Chapter 2. A critical motion curve should be available which will indicate the motion limits for the legs during the tow. This will be used as a guide to decide if appropriate actions have to be taken to alleviate any stress in the legs by altering course, changing speed or even lowering the legs. The motion curve should be provided in the operational manual. If not available then the warranty company will have a curve drawn up by their staff naval architects. Jack-ups undergoing an ocean towage will be subject to an inspection regime to include nondestructive testing of any critical areas of the structure. This will usually include the legs above and below the guides with the legs in the tow position, the jack-house connections to the deck and the spudcans to the legs. If the jack-up is under tow then the stability conditions considered in section 2.11 will apply. When considering the stability elements the following physical watertight requirements must be addressed by the warranty surveyor. > all compartment vents, intakes, exhausts must be watertight up to the waterline at the downflooding angle or 3m above the main deck, whichever is the greatest. These compartments must be capable of withstanding hydrostatic pressure down to this downflooding angle as well as the direct loading of any green water, i.e. actual sea water. > air intakes and exhausts for any required running machinery or any emergency equipment must be above the downflooding angle or 3m above the main deck, whichever is greatest. Hw = 0.61 Lw 000085 > jetting lines, pumping nipples in lines must be checked closed and watertight. > pre-load dump valves must be closed and secured. > mud return lines from shale shaker pumps or any line leading below deck must be blanked off. > dump valves in mud pits must be closed and secured. > overboard valves must be blanked off. > the effects of free surface shall be minimised, e.g. tanks pressed up. One aspect of jack-up transportation as an ocean towage is the correct securing of the legs against movement. In most cases the horizontal movement will be limited with the use of shims or locking devices. The different jacking systems will require specific applications. Electric systems will have the motors checked for torque and equalised. Hydraulic and pneumatic systems will be secured as per the manufacturer’s instructions. Systems with elastomeric pads clearances will be shimmed or pre-load applied to manufacturer’s specification. Tilt-leg systems will have tie bars to by-pass the tilt mechanism. Any leg securing arrangements must be capable of being removed quickly in the case of having to comply with any motion curve limitation requirements or when it may be required to jack down at a standby location during the tow. Ocean tows will not have any setback (or pipes racked vertically inside the derrick structure). In short tows (24hr moves) setback may be allowed provided the following apply: > the derrick can withstand the motion criteria > all pipes and equipment racked are secured to meet the same motion criteria > the stability requirements of the unit can be met For an ocean tow the travelling block should be lowered and secured, the cantilever and substructure must be skidded to the approved tow position and secured. During an ocean tow the helideck or any part of its structure must not be immersed at an angle of 20° about any horizontal axis. This may require a model test to determine that the helideck remains at least 1.5m clear of any wave action. If neither of these conditions can be met then the helideck should be removed. All equipment on board should be secured to meet the motion criteria. For 24hr moves drill pipe, collars and any other tubulars shall be stowed on the pipe deck with stanchions erected. 000086 On an ocean tow drill pipe, collars and tubulars shall be stowed in pipe racks, suitably secured with timber battens. All crane booms will be secured in their boom rests and secured. Shims and wedges may be used as appropriate to limit transverse or vertical movement. Cranes should not be used during an ocean tow except in an emergency. The spudcans will normally be full but on an ocean tow they may be full or empty. In the case of a dry move then the spudcans will be empty. All spaces must be capable of being pumped by the unit’s own pumping system with sufficient power to operate bilge and ballast systems simultaneously. Towed units will be manned to the statutory requirements, dry moves need not be manned. The machinery should be protected from wet damage including the use of de-humidifiers. On a manned tow machinery should be run periodically. It is normal practice in an ocean tow for the forward anchors to be removed. The aft anchors are left in place and stopped off in the racks. A retaining wire is then secured around the anchor shackle with a quick release system set up. In an ocean tow safety equipment must be carried in compliance with statutory requirements. It may be necessary to relocate equipment such as liferafts to prevent damage from wave action. 4.2 FPSOs Typical Floating Production Storage and Offloading Vessels (FPSOs) are converted tankers ranging from smaller Suexmax to very large crude carriers (VLCCs). There are a number of new purpose built vessels as in the FPSO Schiehallion for BP working off the west of Shetlands. They are intended to remain afloat on location for their working life: in the order of twenty years. The majority will only undergo one or two tows during their working life with possibly a final tow for demolition. Many of the guidelines already discussed will apply to the towage of an FPSO. However, there are a number of areas that are specific to the towage of an FPSO which the warranty surveyor must be aware of. These operations tend to be long ocean towages that require careful planning which the warranty company team will be involved with at an early stage. 000087 Typical FPSO - a converted tanker. Diagram showing the position of an FPSO on location showing the mooring system, the drilling well and associated pipeline structure. 000088 Weather conditions and routeing will have to be considered because the location operating criteria may be less than the tow route criteria. This may mean the requirement for structural loadings and motion criteria will be mitigated by the use of staged tows, whereby safe havens where the FPSO can anchor safely while severe weather passes, are part of the tow planning. The capability of the FPSO to sustain the design tow conditions will have to be shown by carrying out checks on the hull girders, plating and verifying the operating limits for the processing equipment on board. This will include the equipment foundations. New build and conversion FPSOs are often completed on tow. This will mean equipment including portable power units, workshop containers and materials will be on board. The placing on board of any temporary equipment must take into account the potential damage from green water and slamming. All temporary equipment must be secured to withstand the ruling design criteria. This may include scaffolding and if it is deemed that any scaffolding will not meet these criteria then it will have to be dismantled. One of the issues with an FPSO towage is the need to maintain a heading and veering off course is a possibility. This is not a desirable situation if sea room is limited in a congested area. The veering will also have an adverse effect on the towing bridal and associated equipment through excessive movement that will cause wear, potentially leading to a breakage. The warranty surveyor should consider this situation and mitigate the loss of heading by diligent use of ballasting and trim. The FPSO should be trimmed by the stern with the forefoot well immersed. The use of a steering tug connected aft should also be considered especially in congested waters. The towing gear should be rigged with the potential of the veering problem and wear down in mind. The towing brackets should be spaced as far apart as possible and any chafe chains reinforced to at least 50% over requirement to allow for any accelerated wear. This may even mean towing by the stern if a suitable towing arrangement can be properly rigged aft. In some cases the FPSO will be self propelled using the original ship’s engines or thrusters that will be used at the location. In this situation the FPSO will need to comply with all the statutory requirements even though most FPSOs are not classed as a vessel when on location. The FPSO must have an emergency towing arrangement installed. The mooring systems involved with the location are not considered as part of the available emergency towing equipment. If quayside mooring is a requirement at any time during the tow or at the end location even as a temporary moor, these mooring arrangements must be part of the overall arrangements of the vessel. If an FPSO is to be moored in shallow water then the warranty surveyor will have to consider underkeel clearances. In doing this calculation the following must be considered: • Lowest astronomical tides • Hull bending • Negative surge • Water density changes • Increase in displacement due to construction • Squat activities and/or the loading of construction modules • Seabed conditions • Ballast, trim and heel changes • Any other local environmental • Bottom protrusions conditions which may affect the vessel 000089 4.3 Ships The towage of ships will depend on a survey to identify any particular problems based on the fact that all ships are different. The ship or ships should be in class although ships for demolition may have expired certification. The degree of certification will determine the extent of any pre-tow survey to be carried out by the warranty surveyor. On completion of the survey should the attending surveyor consider that verification of structural strength and watertight integrity is required the surveyor may instigate the following actions: > a full detailed survey of the vessel structure including close-up surveys of critical parts of the hull > thickness measurements of parts of the hull with the review by the warranty company of the classification scantling drawings > calculations to assess the structural strength depending on the findings of the surveys In an extreme situation, if there is any doubt of the ability of the vessel to undergo a tow then the vessel may have to be dry-docked for a structural survey. To comply with warranty requirements this may mean extensive repair work before a CoA can be issued. Passenger ships and roros pose particular problems due to their construction and free surface effects in the event of flooding. These type of vessels will only be approved for towing if properly manned. This will allow for early intervention in the case of any problems. Of particular importance to the warranty surveyor is the existence of bunker fuel in tanks. This must be minimised before a tow operation can be approved. Reference to IMO’s Guidelines for Safe Ocean Towing must be taken in to consideration by the surveyor. As every ship is different it is not possible to specify the exact connection equipment to be used in a particular tow situation. Any equipment used must be fit for purpose and agreed with the owner of the tow, the tow master and the warranty surveyor. In many cases it may be necessary to use the mooring bitts in which case attention must be given to the strength of the bitts above and below deck. It may be required to reinforce these bitts both on deck and below deck to satisfy the criteria. Depending on the equipment available there are a number of tow connection configurations one of which should be used: > chain bridle with a leg from each side of the tow > single chain from the centreline of the tow e.g. a forward fairlead > anchor chains through the hawse pipe(s) > single continuous chain from each side of the vessel > single continuous chain or chain and wire around part of or the whole superstructure 000090 Wire rope may be substituted for the chain as long as the wire is of adequate capacity and there is no problem with chafe. If chafe is considered a problem through poor leads or the possible excessive yaw of the vessel then the use of oversize chain or wire must be considered. The vessel’s anchor chain can be used as long as the chain capacity meets approval. In this situation the windlass must be in gear, the brake applied, the chain stopper deployed and a backup wire secured to the base of the windlass. All equipment should be secured sufficiently to sustain the motion criteria. This will include cranes and derricks. The rudder should be positioned amidships and immobilised. The propeller shaft should also be immobilised or disconnected during the tow. Emergency pumping equipment will be provided on the tow as assessed by the surveyor depending on the nature and extent of the tow. In the case of a vessel with cargo the tow will not be approved unless the tow is fully manned and classed with an international loadline certificate. A cargo plan must be provided and agreed by the warranty surveyor. The cargo must be stowed in compliance with all seamanlike practice and in accordance with any statutory requirement for longitudinal strength, bulk cargoes will be properly trimmed. SAQ You have been appointed as the on-site warranty surveyor for the ocean “wet” tow of a three legged jack-up drilling unit. What are the priority points you must consider before issuing a CoA? 000091 Chapter 5 5.0 Lifting Operations (see appendices G and I) Warranty companies will be involved in any lifting operation where there is a warranty clause in the insurance policy. This may also apply where a third party requires approval to verify that all the operational procedures including equipment checks have been undertaken before the operation can commence. The type of offshore lifts that may require approval include: > installing jackets > installation of templates and other subsea equipment > installation of topsides > assisted launched or liftable jackets > loadouts > transfer of loads from barges to vessels Crane barge installing a topside unit Wind farm turbine installation When undertaking an approval for an offshore lift operation the warranty company will require the following information: > structural analysis information of the lift including verification of the weight, the lift centre of gravity > lift points and spreaders > a full assessment and plan of the proposed rigging arrangement and equipment (slings, grommets, shackles) 000092 > full details of the cranes(s) with load radius curves and clearances > mooring arrangements with catenaries and clearances > details of the management organisation and proposed marine operational procedures > detailed site survey reports The lift The lift will have to undergo calculations to determine that it will withstand the stresses imposed by the actual lift operation. To be able to conduct these calculations the warranty company must be supplied with sufficient information as detailed below: > plans of the lift showing all main structural members > the structural model > weight and centre of gravity > steel grades and properties > load cases imposed > the codes used for the analysis of the structure to be lifted > table of all the member and joint checks with any proposal for redesign of any member which does not meet the requirements > all certificates for the lift equipment must also be available All lift points, padeyes, padears, trunnions, spreader bars, beams and frames will also be subjected to analysis to make sure they will be adequate for the proposed lift operation under the load and safety factors calculated for the particular lift. Lift equipment It is of paramount importance that the slings and shackles used conform to the requirements following a computation of the loads and the sling geometry. The warranty surveyor will be particularly involved in checking certificates and conducting a visual inspection of any and all lifting equipment to be used in the operation. The important point being that only the equipment specified in the table will be used. To aid this part of the operation the following information must be carefully recorded: • equipment identification number • SWL or WLL • sling length and diameter • wire construction • rigging utilisation factor • direction of lay • CSBL, CRBL or CGBL • wire grade and type 000093 All equipment must have a valid inspection and test certificate issued by an appropriate authorised body, e.g. a classification society, and be manufactured in accordance with the International Marine Contractors Association guidance for slings and grommets (see appendix F). If spreaders, beams or frames are to be used then they must also have a valid test certificate. If a spreader bar, beam or frame is not load tested then all the fabrication information as listed below must be made available to the warranty company as a minimum: > materials and welding consumables certificate > weld and NDT procedures with welders’ and operators’ qualifications > inspection and test plan > as built drawings and design report Offshore heavy lift with spreader bar, frame and lifting points for jacket removal operation 000094 The crane vessel The following information, where appropriate, must be provided to the warranty company: > a GA plan and full specification of the vessel/barge with registration and classification society details > mooring system and anchor specifications > and/or DP system with operating procedures, FMEA and analysis rosettes > operating and survival drafts with details of any ballasting requirements during the lift > full crane specification with radius curves and dynamic capacity Heavy lift vessel dual cranes Heavy lift semisubmersible Heavy lift crane vessel Heavy lift semisub with DP and dual cranes 000095 Radius curve diagram for pedestal crane used for wind farm installations If the vessel or barge is to be moored then a site survey showing the anchor pattern for the operation and a standoff position must be provided by the contractor for review and approval by the warranty company. The mooring arrangement including the anchors’ positions, lengths, size and catenaries of wires with any clearances must also be available. It must be demonstrated that the mooring arrangement, based on the 10 year return data, can withstand the environmental conditions including a single line failure. Any analysis of the mooring arrangement will state the sea state limits for the crane operation. In all offshore heavy lift operations there has to be demonstrated that there are adequate procedures in place to carry out the operation in a safe and efficient manner. This includes sufficient management and operational personnel. There must be a formal Quality Management System (QMS) in place and strictly adhered to at all times. There must be a clear reporting and communication system with direct links to emergency services. The warranty surveyor will test this system to make sure it actually works. Procedures for mooring barges or other vessels alongside the crane vessel must be established. Infield monitoring of environmental conditions for up to date weather, wave and current states must be conducted prior to the operation. 000096 Risk assessments must be carried out in particular if the operation is being conducted in close proximity to other installations. This may include the warranty surveyor attending DP trials. Risk assessments for HAZOP/HAZID must be carried out by the contractor and witnessed by the client, the warranty surveyor and all personnel involved from the contractors. These assessments are usually carried out at an early stage so that any requirements identified can be incorporated into the formal procedures documentation. The following is a simple tabulated overview drawn up by GL Noble Denton, showing typical surveys that the on-site warranty surveyor would be involved with during an offshore heavy lift operation: GL Noble Denton The warranty surveyor should at all times consider the practical elements when carrying out an offshore heavy lift. Every care and good seamanship as well as industry best practice should be exercised at all times. Things do go wrong, as the following photograph shows: 000097 Failed studless chain link as part of a mooring system The following list highlights many areas that should be considered from a practical point of view by the attending warranty surveyor. This is not a definitive check list as the areas may vary depending on the actual operation being conducted, but it gives an idea of what the surveyor should look out for during the course of the operation. • there should be safe access and working platforms to assist the connection or disconnection of the slings • any seafastenings should be designed to minimise cutting, provide restraint when cut and allow a lift off should fouling occur • all cut lines should be marked, this is particularly important when there is more than one stage to the lift • adequate equipment should be available on the lift barge, e.g. burning gear, tuggers, securing materials, lights, safety equipment for personnel and safe access on and off the barge • any loose equipment likely to shift during the lift must be properly secured • an up to date (latest) weather forecast must be available prior to commencement of the lift • the sling arrangement must be in accordance with industry best practice • large diameter slings and grommets should be painted along the length to monitor any rotation • slings must be matched as accurately as possible (it will depend on the centre of gravity) 000098 • slings should not obstruct walkways and handrails during the lift • slings should not kink when lifted • all slings and spreaders (if used) should be able to be laid down safely after the lift • slings with hand spliced terminations must be prevented from rotating • there must be no bending of the wire close to the termination • slings may be shackled together to make a longer sling but they must be of the same lay • to lengthen the sling it is acceptable to insert a shackle as long as any shackle to shackle is bow to bow • the movement of the crane vessel should be monitored prior to the lift to gauge if the motions are acceptable • if a transport barge is used then this should also be monitored for movement prior to the lift 5.1 The Approval Process As we have seen lifts may be made up of different configurations using different crane combinations vessels and barges. Warranty approval by the warranty company will be based on the following: > complete review of any calculations required > complete review of the operational procedures > the rigging arrangement > the crane vessel/barge mooring arrangements > the prevailing weather and forecast conditions and operational weather limits > all the equipment involved is correct and certified > the actual vessel or barge movement at the location prior to the lift > consideration of any site changes and readiness for the operation on site > risk assessments being carried out for SIMOPS and HAZOPS 000099 The issuing of the CoA will only be issued by the attending surveyor just before the lift operation is to start. It has to be emphasised that the CoA is only issued for a particular lift based on the attending surveyor’s visual observations of all equipment. The lift is said to start when cutting of seafastenings starts and the crane is connected and slings are tensioned. The lift is said to be complete when the structure or object being lifted is set down in its correct position. At this point we have to remember that if any changes are made in the equipment or operational procedures after the issuing of a CoA then the CoA may be considered invalid unless these changes are given in writing for approval by the warranty company. 5.2 SIMOPS and HAZOPS We have mentioned in 5.1 SIMOPS and HAZOPS. It is important to understand, as a warranty surveyor in particular, the significance of these two operations. SIMOPS or simultaneous operations may have an impact on any offshore operation. These operations are loosely described as any potential clash of activities that may bring about an undesired event or set of circumstances which could be to do with safety, environmental, damage to assets, operational, commercial or even financial. The definition of SIMOPS is “performing two or more operations simultaneously”. We will confine our interests to the offshore environment where the type of activities may include: > undertaking non-routine operations within an installation’s 500m exclusion zone > multiple umbilical, riser and flowline operations > field developments involving multiple vessels and /or contractors In the offshore industry there could be all manner of vessels involved in many different operations, e.g. dive support, heavy-lift, supply boats, barges, pipe-lay, cable lay, ROV, survey vessels with installations such as fixed and floating platforms, drilling rigs, FPSOs and FPUs, all being involved at the same time. It is important that any SIMOPS is identified at an early stage to allow operational procedures to be developed. The following are the type of issues that may result in SIMOPS: > schedule clashes, e.g. activities in the same area at the same time > physical clashes, e.g. anchor patterns, loss of position > failure impacts, e.g. explosions, gas leaks 000100 > interference between platform and vessel operations > contractual and third party interface, e.g. liabilities, insurance > environmental impacts, e.g. currents, icebergs, weather limits > territory clashes, e.g. 500m zone, existing infrastructure Once a SIMOPS has been identified then a “Kick-Off” meeting is arranged to bring all SIMOPS parties together to develop operational procedures. At this meeting it is important that the party in overall charge is identified. A risk assessment of all the anticipated activities must be undertaken to identify constraints and hazards and then to draw up a checklist of corresponding mitigation measures. Each party involved will draw up a dossier identifying that party’s work-specific involvement in the SIMOPS activities. To assist each party in drawing up a dossier the meeting should identify the responsible person for each party, the input required from each party and the time frame for each part of the SIMOPS activities. The contents of the dossier should include the following elements: > a summary of the work including equipment to be used > scale drawings (where appropriate) of the activity > a list of assets to be used, e.g. vessels, barges, cranes > a summary of any constraints relating to the activity > an organigram with key positions identified > a summary of the main hazards > a risk register of mitigation strategies and precautions > a management of change procedure in case there is a deviation from the activity > escape route for each vessel involved > weather limits, sea and environmental condition limitations > a clear and concise communication system must be established > all the acoustic methods being used by each party must be identified 000101 The following is an industry flow chart or life cycle model for SIMOPS: HAZOP or Hazard and Operability analysis is a structured and systematic technique for system examination and risk management. It is used to identify potential hazards and operational problems that may lead to non-conformities. HAZOP is based on a theory that assumes risk events are caused by deviation from design or operating intentions. HAZOP defines the following as used to describe the methodology : Hazard: Potential source of harm. Deviations from design or operation intent may constitute or produce a hazard. Harm: Physical injury or damage to health of people or damage to property or the environment. Harm is the consequence of a hazard occurring. Risk: The combination of probability of occurrence of harm and the severity of that harm. 000102 HAZOP is used for assessing hazards in facilities, equipment processes and operational procedures As in all theoretical analysis techniques there are always advantages and disadvantages as the following table shows: 000103 104 IIMS - Call +44 (0)23 9238 5223 or visit www.iims.org.uk 5.3 Load and Safety Factors Before approval can be given for any offshore lifting operation there are a number of calculations that must be conducted for the crane, rigging, lift points and spreaders bars. The following flowchart used by GL Noble Denton gives an easy to read summary of these calculations. It must be emphasised that this flowchart is not definitive as each operation has to be individually considered. 000104 We will look briefly at the factors indicated on the flow chart and explain their significance. It has to be noted that it is outside the scope of this unit to cover actual calculations as they are conducted off site by the engineering department within a warranty company by a specialised team. Weight contingency factors In order to derive correct loads for the design of rigging and lift points there has to be weight control during engineering and construction of offshore structures. The structures are classed depending on the following: Class A - where the project is weight and centre of gravity sensitive for lifting and marine operations. Class B - where the focus on the weight and centre of gravity is less critical for lifting and marine operations Class C - where the weight and centre of gravity are not critical Hook loads When considering the loading on a lift point or structure the hook load will include the contingency factor where: Static Hook Load = (gross weight or NTE1 weight) + (rigging weight2) 1 (NTE = not to exceed weight) 2 (rigging weight includes slings, shackles, spreaders) Dynamic Hook Load = Static Hook Load x DAF (DAF is Dynamic Amplification Factor) Rigging geometry The rigging geometry should be configured so that there is a maximum tilt of 2°. 000105 Lift point and sling loads The basic vertical point load is the load at a lift point including the gross weight of the structure and proportioned by the geometric distance of the centre of gravity from each of the lift points. This load will be increased by the Dynamic Amplification Factor (DAF).There may be additional factors applied depending on the centre of gravity of the structure. The sling load is the vertical lift point load resolved by the sling angle using the minimum possible angle, the minimum sling angle is usually 60°. Dynamic amplification factor This is where the forces acting on a load amplify the force exerted by its own weight: dynamic load is where a load is subjected to dynamic forces, e.g. when in water, going through the splash zone, or affected by shape, weight, size, vessel movement static load is a weight unaffected by external forces Skew load factor Skew load is a load factor based on the manufacturer’s sling length tolerances, rigging arrangement rigging geometry, fabrication tolerances for lift points and sling elongation. The factor applied will depend on the slings and may vary from 1.0 to 1.25. If a single spreader bar is used in the system with matched slings a factor of 1.05 is applied. If more than one spreader bar is used in the system with matched slings a factor of 1.10 is applied. In a multi-hook system a lower factor may be applied. In a single hook system where unmatched slings are used then the factor has to be calculated in any case the SKL applied in this case shall not be less than 1.25. 2-hook lift factors If the lift is with two hooks from the same vessel then the following factors will apply to take into account any increased loads due to the hook elevation tolerances. DAF = dynamic load + static load static load 000106 Centre of Gravity shift factor = 1.03 Tilt factor = 1.03 If two slings are involved from each hook then a yaw factor is applied. Yaw factor = 1.05 If the hooks are from different vessels then a separate lift calculation should be carried out. Lateral lift point If the lift point is correctly orientated with the sling direction then a horizontal force of 5% of the lift point load is to be applied. 2-part sling Where a 2-part sling passes over, through or around a shackle, trunnion, padear or crane hook the total force into each part shall be distributed in a specific ratio, usually 45:55, to account for friction losses. If the sling passes over a rotating sheave the ratio is usually stated as 49:51 to allow for friction. Termination factors Where a sling ends in a termination a factor will be applied depending on the make up of the termination as follows: > hand splice x 0.75 > resin sockets x 1.0 > swage fitting x 1.0 > steel ferrules x 0.8 > fibre rope slings x 0.9 (Note: 9-part slings are not included, they are to be considered separately.) Bending factor Where the sling or grommet passes round a shackle, trunnion, padear or crane hook there will be a factor applied to calculate the assumed breaking load: Calculated breaking load x bending factor = assumed breaking load 000107 D = the minimum diameter over which the sling body or grommet is bent d = the sling or cable load diameter The following table gives the resultant factors for wire rope slings and grommets: D/d <1.0 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 Factor Not advised 0.50 0.59 0.65 0.71 0.74 0.78 0.80 0.81 Fibre rope slings usually have a bending factor of 1.0. (Note: the termination and bending factors should not be applied together. The factor which gives the lowest breaking load will prevail and should be used.) Slings and Grommets (see appendix F) The minimum safety factor will be calculated allowing for all the other factors that are involved. But in all cases the safety factor for steel slings and grommets will not be less than 2.25 and for fibre slings and grommets 4.75. Shackle safety factors The working load limit (WLL) will not be less than the static sling load. Not withstanding the above, the dynamic sling load (static x DAF) will not exceed the shackle maximum breaking load divided x 3. Grommets Grommets require special consideration to make sure the breaking load and bending efficiency have been correctly taken into account. Consequence factor The following table gives the factors to apply to the structure the lift points and the lateral load effects on lift points and the attachments to the structure. Bending factor = 1 0.5 ( ) D d 000108 Lift pints including spreader bars and frames 1.30 Attachments of lift points to the structure 1.30 Members directly supporting of framing into lift points 1.15 Other structural members 1.0 These factors are applied after all the other factors are considered. 5.4 Crane Hook Loads and Active Heave Compensated Lifts The hook load of any lift will not exceed the crane capacity as determined from the crane load radius curves. These curves are usually expressed as a safe working load or a static capacity, verification of the latter is paramount. In many cases different radius curves are calculated for differing seastates. The seastate for the probable limits at the time of the operation will be used. If an active heave compensated crane (AHC) is to be used for the lift then specific information about the crane should be obtained by the surveyor: Technical data and operating manuals Load radius curves in compensated mode, seastate limits and boom slew angles FMEA for the crane system DAF analysis in compensated mode Check maintenance logs AHC crane of 100t on an installation, maintenance and repair vessel (IMR) 000109 5.5 Structural Calculations In any load/lift operation the warranty company will make structural calculations based on the load factors considered in section 5.3. This will also mean having adequate load cases for different scenarios. In a simple four point lift the following load cases will be considered: 1. As a base case: the gross or NTE weight resolved to the lift points but with NO skew factor 2. Gross or NTE weight with the skew factor applied to one diagonal 3. Gross or NTE weight with the skew factor applied to the other diagonal; In all the above the sling angle, point of action, any offset or torsional loading on the slings will be taken into consideration. The analytical process and loadings as above will be applied to the complete structure, lift points, spreader bars and frames. In determining allowable stresses the structural strength of the steelwork, will be assessed using the methods described in recognised industry codes. These codes include the associated load and resistance factors for Load Resistance Factors Design code (LRFD) and safety factors for working stress design (WSD). 5.6 Lifting Points In all heavy lift operations due consideration must be given to the design of the actual lift points. Lift points may be padeyes, padears or trunnions. This will involve the lift point geometry being configured to support and maintain the sling geometry under load. These lifting points will be subject to stress analysis including modelling and load application. Keeper plates will be part of the design to act as preventers for the slings and grommets. During lifting there will be ovalisation of the sling such that this has to be considered and adequate clearance between the cheek plates, shackle pins or trunnion keeper plates to allow for this. It is also important that any bore or pin hole, the hole through which a shackle pin will pass, is suitable to take the intended shackle. In most cases an allowance of 3% is used as the amount the hole is larger than the shackle pin diameter. 000110 Line drawings of a padeye and a trunnion showing the main parts It must be emphasised that different names may be used for a piece of lifting equipment or a part of a piece of lifting equipment depending in what part of the world you may be working. The warranty surveyor must be very aware of the potential of such regional variations in terminology, e.g. bore holes and pin holes. It is important in the design of the cheek plates that their thickness does not exceed that of the main plate thickness, usually no more than 50%, otherwise the main plate will become secondary and the robustness of the lifting point will be compromised.. 000111 5.7 Bumpers and Guides As the name implies bumpers and guides do exactly that. The design, construction and position of these bumpers and guides will depend completely on the specific requirements of each individual lift. In any heavy lift, but in particular when a lift has to be accurately positioned, there has to be some form of guide structure to assist in locating the lift in to its correct location. Obviously during this operation there will always be a situation where contact with the structures will be inevitable due to movement and to assist the positioning operation. To this affect bumpers are designed and positioned accordingly, the latter will depend on each individual lift. When we talk of movement there is a general rule that the structure movement during positioning shall be limited, the following values are given as a guideline: Vertical +/- 0.75m Horizontal + 1.5m Transverse tilt 2° Longitudinal tilt 2° In the design stage for bumpers and guides consideration must be given to the forces acting on them and due allowances made within the design criteria. The following are considered industry norms: (In all cases the forces in any direction are combined to give the worst case scenario) W is the static hook load Vertical sliding bumpers Horizontal force 0.10 x W Horizontal force ( out of plane) 0.05 x W Vertical friction force 0.01 x W Guides Horizontal force on pin end 0.05 x W Vertical force on pin end 0.01 x W 000112 Horizontal “cow-horn” bumpers with a vertical guide Horizontal force in any direction 0.10 x W Vertical friction force 0.01 x W Vertical “cow-horn” guide with a horizontal bumper Horizontal force in any direction 0.10 x W Vertical force on inclined guide face 0.10 x W The connection to the structure must be as strong as the bumper or guide and they should have a low stiffness factor to allow some deflection without yielding. 5.8 Operational Clearances In any heavy lift operation there must be an adherence to clearances during the lift. The actual clearances will depend on the lift, weather conditions, bumper and guide arrangements and in particular the motion characteristics of the crane vessel and or the barge. These clearances are an aspect where the warranty surveyor will be very much involved as he will verify the clearances on the lift arrangement plans submitted by the contractor. Clearances are applied in three particular situations: around the lift itself, around the crane vessel and around any moorings and anchors. The following examples are industry guidelines to give you an idea of distances used. Clearances may vary, some less, others more depending on the location of the lift. In all cases the clearance is based on a level lift. Clearance around the lift When the lift is suspended there should be 3m between the lift and the crane boom. Unless a bumper and guide system is in place then 5m between the lift and any other structure on the same barge. Clearance around the crane vessel 1. Vessel moored next to a fixed platform 3m between any part of the crane or vessel and the platform 5m between any part of the vessel’s hull and the platform 10m between any anchor line and the platform 000113 2. If the crane vessel is in DP (Dynamically Positioned) mode 5m between any part of the crane vessel and the platform Clearance around moorings and anchors This is an area where operators and contractors may have their own specific requirements and the warranty surveyor will have to take this in to consideration and establish with the relevant authority what these clearances will be and have them declared on the lift arrangement plans. These clearances will also take into consideration the following on site circumstances: Water depth, proximity of subsea equipment, seabed conditions, anchor drag, single line failure, station keeping ability of the tugs, the accuracy of any survey, weather conditions during the lift operation. In all cases except where a temporary lay-down has been approved, moorings will never be in contact with any subsea equipment or run over the top of a subsea completion or wellhead. An example of a clearance would be that the horizontal clearance between a mooring line and any structure other than subsea equipment should not be less than 10m. If any clearances cannot be achieved or are impractical in the circumstance and a temporary lay-down over a pipeline or umbilical is to be approved then the warranty company will have to be provided with sufficient evidence and documentation. This will include, but not be limited to, written evidence that the pipeline owner accepts the situation, information about the pipeline and evidence about the anchor wire tension. In today’s computerised world there are a number of computer programmes that will assist the mooring operations in particular to give accurate assessment of clearances. As an example, visit www.fugrochance.com/Brochures where you will find a short demonstration video under StarFix Moor that will show you what is available and the information that can be obtained. SAQ Marine lifting operations are often carried out as part of a larger offshore operation involving many other parties. What operational procedures would you undertake to mitigate risk when carrying out multiple operations at one offshore site? 000114 Chapter 6 6.0 Moorings and Mooring Operations Warranty companies will be involved in the approval of offshore moorings and mooring operations. In the majority of cases an operations manual will be produced with relevant information including approved wind and current load factors, wave drift coefficients, and limitations of equipment performance, e.g. windlasses, thrusters or winches. The manual will contain details of the operation, design criteria, location information, design environmental conditions. There will also be information about the structure to be moored, e.g. MODU, FPSO and a full description of the mooring system and all the associated equipment, e.g. anchors, mooring line make up, mooring line size, buoys, connectors, inspection reports detailing condition. We will look at these elements in more detail. Firstly, we have to understand the basics of the different types of mooring systems in use in the offshore oil and gas industry. Spread mooring As its name implies this is a pattern of anchors designed to restrain the movement of the structure about a defined position. These anchors may be deployed evenly about the centre of this position or deployed to provide more restraint in a predefined arc due to the direction of the loadings, e.g. wind, current. Spread Mooring 000115 On the previous page is a simple drawing of an eight anchor spread used with an MODU showing the basic components. The most common mooring configuration in relatively shallow water has been the catenary system consisting of wire and chain as would have been used in this diagram. When exploration moved in to deep water the weight of the mooring lines became a limiting factor. To overcome this problem synthetic ropes are used in the mooring system for weight reduction and/or the use of a taut leg system. The difference between a catenary system and a taut leg system is that the catenary line is horizontal at the surface and a taut line is at an angle. In a taut line system the anchor point has to resist horizontal and vertical forces whereas in a catenary the anchor point only has to resist the vertical forces. In the catenary the restoring forces are mainly the weight of the lines in the taut leg system, the restoring forces are generated by the elasticity of the mooring lines. The advantage of a taut leg system is that the foot print is much smaller than a catenary system as can be seen in the following diagrams: 000116 Single point mooring Single point moorings are designed primarily for hull form vessels, e.g. FPSOs. This allows the vessel to weather vane, i.e. keeping the heading into the direction of the prevailing environmental forces and so reducing the loadings on the vessel. There are a number of different designs for these moorings and each case has its own merits depending on the design analysis for the type of vessel and location. Turret mooring A turret mooring is any mooring where a number of catenary mooring legs are connected to a turret and includes a set of bearings which allows the vessel to rotate about the turret. These turrets can be either internal or external as shown in the following diagrams: External turret Internal turret (API) 000117 Catenary Anchor Leg Mooring (CALM) The CALM mooring system is made up of a large buoy supporting a catenary of chain legs anchored to the seabed. The well risers are then connected to the underside of the buoy. The simplest systems have a hawser connecting the vessel to the buoy. This can be restrictive as the motion of the buoy and the vessel in extreme weather conditions will be different potentially requiring the vessel to disconnect from the buoy. To overcome this situation there are systems of what are described as yokes. These yokes may be further described as either a soft yoke or a hard yoke. Catenary Anchor Leg Mooring (CALM) with hawsers (API) 000118 Single Anchor Leg Mooring (SALM) In this system a large tubular riser having a substantial amount of buoyancy at or even above the surface is employed. The vertical buoyancy acting at the top of the riser works like an inverted pendulum. This action restores the riser to the vertical position when displaced. Single Anchor Leg Mooring (SALM) with tubular riser and hard yoke (API) Details of the mooring operation must include the actual nature of the operation, dates and times, duration of the operation. This will involve determining the “start” point and the “end” point, you have to remember that each stage of the operation may have an individual CoA issued and details of the operational criteria. The design criteria must be established and the industry code and/or standards that were used in the design stage. 000119 Details of the location must include the geographical location with relevant coordinates, water depths covering the area of the mooring spread, seabed conditions, e.g. soil type, information about any other installations or structures that may affect the operation surface and seabed. Obtaining seabed data is something that the warranty company may be required to carry out. The warranty company will have its own processes and procedures to conduct a geotechnical seabed survey. The warranty surveyor will definitely require this information but will not usually be directly involved in this work. The design environmental conditions and parameters must be considered and this will be done at the company offices by staff qualified and experienced in this type of design analysis. The following are the typical design parameters that are considered when designing a mooring system: Winds Extreme wind speed and direction Gust speeds and spectra Waves Extreme wave crest height Extreme wave height, direction and periods Frequency distribution of individual wave heights Probability of significant wave height and period Wave spectra and directional spreading Water depths Water depth below mean sea level Extreme water level variations Currents Extreme current speed and direction Variation through the water depth Fatigue design current speed Temperatures Extreme air temperatures, max and min Extreme sea temperatures, max and min Snow and Ice Maximum thickness of snow Maximum thickness of ice Density of snow and ice Marine growth Type of growth Permitted thickness Terminal thickness profile 000120 The analysis of the mooring system will depend on the code being used. There are a number of recognised, existing design and best practice codes for moorings. The most widely used is the International Standard ISO 19901-7, 2005. The American Petroleum Institute API Recommended Practice 2SK (RP 2SK), still widely used, is being incorporated in to and superseded by ISO 19901-7. There is also DNV OS E301 Position Mooring (POSMOOR E301) and Specific Requirements for Offshore Structures Part 6- Marine Operations ISO 19901-6:2009. The codes apply to the two main classes of mooring systems. The mobile system relates to a floating structure usually a drilling rig or a construction barge/vessel that moves location on a regular basis. The second class is the static mooring where the structure/vessel is moored for a long period of time as in the case of a FPSO vessel. The application of the design codes will very much depend on a case by case situation where the factors involved may be refined depending on the actual location. It must also be stressed that the local maritime jurisdiction that the structure/vessel may be working in may also have governing rules that may be more stringent than the codes. Warranty companies and warranty surveyors must always keep up to date with the latest rules and codes that may affect them in their work. Mooring systems are subject to two types of loading. The first is quasi-static loading which is induced by the wind, swell, current and what is known as the “frequency” of the system, which is the natural resonance due to the system’s flexible nature. Then we have the dynamic (shock) loads induced by the waves and swell which cause the structure/vessel to roll, pitch, surge, sway, heave and yaw. These last words are known as the six motions of a vessel in a seaway. It is important at this point that we look at and so understand the six movements of a floating structure. To do this it is easiest to refer to a simple hull form diagram as shown below: 000121 Pitch - The bow pitches into a head sea or swell (can lead to slamming of the bow) Roll - The vessel rolls from upright to port and starboard (worse if sea’s on the beam) Heave - The rise and fall of the vessel in a seaway Sway - Movement in the transverse (athwartship) direction Surge - Movement in the longitudinal (fore and aft) direction Yaw - The motion leads to the vessel’s heading being off course (or off the set heading) In all cases there are two conditions which these loads are calculated for: 1. when all mooring lines are intact 2. when one mooring line or, in some cases, two mooring lines have failed In the codes the mooring system and so the individual components must have a safety factor built in, for both the intact and damaged states. These factors will vary, usually in the range of 3-1, static moorings as in a FPSO tend to use a higher factor than mobile units such as drilling rigs. 6.1 The Approval Process There are basically two aspects to the approval process. 1. The technical studies and reviews which may be one or a combination of the following: > Audits of procedures, engineering calculations possibly combined with actual model tests > Independent verification of the feasibility of the proposed mooring operations > Third party reviews and independent analyses 2. The possible surveys and site attendance: > Site survey and examination of the mooring system (to confirm compliance with the submitted design) > Checking all the certification of the component parts of the mooring system > Checking the condition of the vessel machinery and suitable manning > Verification of procedure and actions in an emergency > Involvement with any local authority (ports, pilots) 000122 > Function testing of key equipment or vessels that will be involved in installing the mooring system > Risk assessment and HAZID > Finally witnessing the installation and test tensioning We will look at a simple example to demonstrate what may be involved in the mooring of an MODU. (Differing circumstances will always dictate exactly what is involved, these may be contractual or practical) Warranty company office needs to: Verify that the MODU can moor in the location water depths. This will be based on the design parameters and building code. It may be that a stricter code applies to this particular area in which case the warranty company has to verify that the proposed mooring system will meet the standard of the code. Verify that the MODU mooring system design using the appropriate seabed data will be able to sustain the design storm loads. This will depend on the anchor type and the available line lengths on board. If the anchor holding is not considered suitable for the task then another anchor type that will have adequate holding capacity to meet the storm design criteria must be used. Verify that the proposed anchor pattern is the most efficient considering the maximum environmental loads and the duration of the stay at the location. If the mooring lines have to cross subsea equipment or obstructions the warranty company must verify the contingencies for deployment of the lines and any support system to be used. In these cases support buoys will normally be used, surface or subsurface. The warranty company will verify the safety and integrity of the actual mooring procedure to the extent of advising the client what to include in such a procedural document. The warranty company will also advise on the specifications of the anchor handling tugs to satisfy the requirements of a safe operation. If this evaluation process is achieved satisfactorily then the warranty company may issue a CoA. This CoA may be unsigned if a warranty surveyor is to attend on site (see below) or signed if the contract does not require an onsite surveyor to attend. On-site surveyor in attendance needs to: Verify that the MODU is in all respects ready to complete the proposed operations, (the warranty surveyor will usually work from a check list developed specifically for this type of operation). In conjunction with all management staff involved in the operation, evaluate the mooring procedure document to verify that the MODU can carry out the proposed mooring operation. Inspect all the mooring machinery and components to verify they are all in a fit state for the operation. 000123 Inspect the anchor handling tugs to verify their equipment and suitability for the proposed operation. This will include discussing in detail with the master, officers and crew to verify their ability and experience to fulfil the requirements of the mooring operation. If all the above are to the satisfaction of the warranty surveyor he will sign and issue the CoA. Once the operation starts the warranty surveyor will monitor the operations and give advice where deemed necessary. He will verify that the agreed procedures are being kept to or any required changes are approved. The surveyor will monitor the test tensioning of the anchors and record these or any changes to these values including the use of piggy back (back-up) anchors. The surveyor must keep a detailed log book of all events which will be based on an approved company format and submit this to the office as part of the overall documentation for the contract. 6.2 Design Considerations All moorings must be designed to withstand the most severe loads caused by the environmental conditions at the location and in consideration of the length of stay at the location. The design factors and requirements are contained in the codes described in section 6.1. Design criteria depends on the type of operation, be it unrestricted, which is free of environmental limits, or weather restricted, which are usually operations of less than 72 hours duration. The unrestricted operation will be dependent on the return period. The return period is an estimate of the interval of time between events like a severe storm. It is a statistic only and denotes the average recurrence interval over a period of time. It is used in risk assessment, in the construction of offshore structures and in warranty work to design a mooring system capable of withstanding these potential storm forces. We have all heard of the “10 year storm” and the “100 year storm”. It tends to be true that a 10 year storm will happen on average every 10 years. In the case of a 100 year storm this does not mean that a 100 year storm will happen every 100 years. In any 100 year period a storm may occur once, twice, even three times or not at all. Mooring Type Mooring Duration < 6 months 6 months < t < 20 years < 20 years Offshore-Mobile near another structure 10 year See below1 100 year Offshore-permanent N/A See below1 100 year Offshore-Mobile-Open location 5 year See below1 100 year 1 In most cases of durations longer than 6 months the 100 year return period is used. In the case of a mobile mooring near another structure it is usually referenced to a 10 year return period. In the case of a weather restricted operation, the operational criteria will always be less than the design criteria. 000124 If the weather restricted operation is less than 24 hours then the maximum seastate will not exceed the design seastate multiplied by a reduction factor varying from 0.50 to 0.75 depending on the weather forecast provisions available. In tropical areas the unpredictability of storms and squalls must have particular consideration to the extent that weather radars and a meteorologist may be required on site at all times. When considering environmental loadings there are many complex calculations and components to consider outside the scope of this unit. Here we have just highlighted the salient points. Wind and wind load Wind speeds are referenced at 10m above still water level and for permanent moorings either of the following are considered, depending which is stronger: > Steady one minute velocity > One hour mean plus gust spectrum (the gust spectrum is found in ISO 19901) In the case of mobile moorings the steady state wind or a suitable gust spectrum is used. Wind loads have variable components based on a gust spectrum. These loadings can be calculated using drag coefficients, model tests or computational fluid dynamics. Current and current load The design current use will take account of various components including mean springtide, the return period storm surge and any other wind driven components. When calculating current loads on conventional draught vessels, e.g. barges, FPSOs and semisubmersibles, only the surface current speed is considered. If the mooring is to be permanent then the increase in drag factor due to marine growth on the mooring lines and risers has to be taken into account. These loads can be calculated using drag coefficients, model tests or computational fluid dynamics. Wave and wave loads When dealing with mobile moorings a single extreme significant wave height is usually considered. In the case of a permanent mooring different combinations of significant wave height based on the 100 year return period contour are used for the analysis. Waves cause motions on a vessel as well as mean and varying loads. The wave drift force contributes to the mean environmental load. This wave drift force is calculated from the wave spectrum. In general the direct effect of waves on a mooring line can be neglected. In shallow water, usually considered less than 000125 100m, shallow water corrections will be required this is due to the increase in wave frequency motion. It has also to be noted that the possible impact of long period swell must be considered. Vessels that are catenary moored can be subject to low frequency motions of sway, surge and yaw. This is due to the combined actions of the vessel and mooring system at periods close to the natural frequency of the overall mooring system by low frequency variable loads, e.g. varying wind load and frequency difference components of the wave drift force. These low frequency motions can have an influence on mooring line tensions in particular in deep water. There are two industry accepted techniques for the calculation of mooring line tension: 1. Quasi static analysis where the mean environmental force is applied and the vessel offset calculated. Quasi static calculations are known to increasingly underestimate the line tension as the water depth increases. 2. Dynamic analysis which takes into account both the moored vessel responses and the line dynamics as a result of the fairlead motions and the hydrodynamic forces on the mooring lines. This method is considered more accurate than the quasi static method in particular for deep water moorings. Mooring system strength The overall mooring system must have sufficient redundancy such that the failure of one component will not result in the vessel losing station or encroaching within the allowable clearance of another structure. The mooring pattern must be designed to be balanced with line pre-tensions as evenly distributed as practical. Careful consideration must be given to any mooring line bearing angles such that out of plane loads are not transmitted to components with limited rotation, e.g. padeyes and fairleads. In deep water locations checks must be made to ensure there is no contact between the mooring lines and the vessel or the bolster racks and bolsters to avoid any possibility of chafe damage to the line or the vessel structure. The maximum tensions for the mooring system shall not exceed the MBL of the lines and the connectors and attachments subject to the application of an appropriate safety factor. These factors are found in ISO 19901-7 and reproduced here for information. Analysis Condition Analysis Method Line Tension Limit (percent of MBL) Design Safety Factor Intact Quasi Static 50% 2.00 Intact Dynamic 60% 1.67 Redundancy Check Quasi Static 70% 1.43 Redundancy Check Dynamic 80% 1.25 Transient Quasi static 95% 1.05 These safety factors apply to wire, chain or fibre mooring lines. 000126 6.3 Clearances It is of great importance that clearances are very clearly defined when designing a mooring system. There are no specific clearances laid down so each individual project must define the allowable clearances taking into account the following conditions: > Water depth > Proximity to other structures in particular subsea structures > Seabed conditions including any seabed slope > Single mooring failure > The weather conditions anticipated during laying the mooring system > The ability of the anchor handling vessels to maintain station > The estimated anchor drag during embedment > The accuracy of the survey for positioning There are industry good practice minimum clearances, which are shown in the following table for information. The contractors involved in any project may have their own clearances which will in most circumstances take precedent. This also applies to other structures in the vicinity, the owners of which will have to be consulted on their requirements for clearances to their own structures. It is imperative that all parties agree well in advance, preferably in writing, to the clearances for the operation. In all cases a risk assessment should be conducted to identify the risk levels. Condition Minimum Clearance Allowance for anchor placing inaccuracy 50m Anchor horizontal distance from a subsea structure 100m Horizontal distance to pipeline or structure in line of anchor ( see below) 300m Line horizontal to subsea wellhead or manifold 100m 1Line/vessel horizontal to platform 10m Line above pipeline > 40m water depth 10m Line above pipeline < 40m water depth 25% water depth (min 5m) Line to Line 20m (30m if repositioning by winching) 1 This only applies to platforms which project above the water level 000127 There must always be adequate clearance between anchors and any seabed structures and pipelines. The following diagram shows the exclusion zone for anchors and pipeline clearances: 6.4 Mooring System Components To ensure the safety of a moored structure the selection of a mooring system must be done to meet code requirements. All components must be used correctly and in line with any manufacturer’s recommendations and to industry best practice. This includes a good inspection regime and a strict maintenance programme. All the components used must be certified and this is one of the important areas for the warranty surveyor to do on site, to check the validity of all the certificates of all the components to be used at any stage of the operation. The basic components of a typical offshore mooring system are as follows. Anchors Anchor size and design have developed exponentially over the last few decades as the ever increasing demand for oil and gas has meant larger structures in more rigorous locations in deeper waters. The following drawing shows a small range of anchors in use offshore today. There are what are now knowm as the “older” types like Danforth, Temco, Offdrill, Moorefast and LWT with some of the “newer” generation, Bruce FFTS, Superior Delta and Drag Class A. They range in weight from as small as one (1) tonne up to forty (40) tonnes. They are of course designed for different conditions including seabed soil conditions. 000128 As an example where the seabed is hard anchors must be capable of taking the full load through the fluke tips. All anchors must be correctly configured for the seabed condition, in particular with respect to fluke angles being set as per the manufacturer’s recommendation. 000129 Ultra High Capacity Drag Embedment Anchor Drag embedment anchors, sometimes known as High Holding Power (HHP) anchors, attain their holding power based on the fluke area being embedded in the seabed soil as the anchor buries itself when being dragged across the seabed. To attain maximum holding capacity the whole fluke area must be buried and the soil structure such that it will resist the pull of the anchor. The vertical pull angle is also critical to avoid the anchor being pulled up. These anchors if properly laid can have holding capacities in excess of 15 - 20 times their physical weight. As you can see in the photograph above, drag embedment anchors are designed and engineered to very high specifications and as such their site installation must be carefully analysed. The correct anchor, soil/seabed conditions and fluke angles must be considered to attain the maximum performance. As part of the mooring process careful initial assessments must be carried out which will involve deciding the best anchor to use. The anchor penetration, the tensioning programme and method will also be carefully analysed prior to commencement of any installation programme. Drag embedment anchors are under continuing development as new and deeper exploration sites are opened up and require new or specific anchors to fulfil the holding capacity requirements. Suction anchor 000130 Suction anchors, as the name implies, rely on the suction effect of the surrounding soil when the anchor is fully buried. To achieve maximum efficiency they must be fully buried and all air and water evacuated from the can. In this situation the surface area of the can in contact with the soil is so large that the side loading forces imposed by the anchor line pull are not large enough to overcome the sheer strength of the soil. Suction anchor systems are, by virtue of their holding principle, only effective in the right soil conditions such as sift mud and clays. The site must be carefully surveyed to allow data to be obtained to enable the correct size of anchor to be calculated for the particular site. Torpedo Anchors Torpedo anchors are a relatively new method for a mooring system although they have been under development and evaluation for many years. As the name implies they are installed by dropping the anchors from a predetermined height into the seabed like a torpedo, the drop rate can be up to 100km/hr. The weight of individual anchors will be in the range of 50-100 tonnes. The dropping height calculation is critical as without full penetration these anchors will not have the required holding capacity. The soil conditions at the site must be appropriate for the installation and this is soft sediment. (For an animated demonstration see www.deepseaanchors.com/Drop_Installation.html) Chain Chain mooring lines are the most common for use in mooring MODUs in moderate water depths up to 3-400 metres. After this the weight of the chain imposes considerable extra loads on the system, in particular the handling system. It is often overcome by the use of support buoys or inserting wire sections in to the suspended part of the system thereby reducing the weight. If this system is employed there will be chain on the seabed at the anchor end then wire sections in the suspended part and another chain section at the rig end. In this way the rig can make finite adjustments to the length and tension in the system. Chain may be of studded or studless construction. 000131 Stud chain Studless chain (note the coke can for size comparison) Studless chain and anchor D shackle giving size comparison with the deck hand Wire rope Wire rope mooring installations are used in greater water depths up to 2-3000 metres when at these depths even the weight of the wire puts constraints on the system. Developments in wire design have created wires with very high tensile strengths which allows for installation in greater depths. The use of support buoys is also a method employed in deep water locations. For smaller and more mobile anchoring systems, as in the case of a pipelay barge where the barge is constantly on the move, wire rope systems are the most flexible. 000132 Offshore wire rope showing size comparison with operator Fibre rope For the requirement to explore in ever deeper water up to 3000 metres plus, new high strength synthetic fibres have been developed. These fibres of nylon, polyester or high modulus polyethylene (HMPE) can be woven in to offshore mooring ropes. They are usually installed as a taut system as the lightness of the rope and the system do not have the same “spring “ effect as a chain or wire catenary installation. The unit can only maintain station by having relatively taut mooring lines. The motions and forces of wind and wave effects acting on the lines of the vessel are absorbed by the elasticity of the lines, as opposed to the mooring line curvature in a catenary system. As can be seen from the photograph below anchor handling tugs have to be specially rigged to handle these fibre rope systems. Anchor handling tug rigged for fibre rope operations 000133 Connectors A chain mooring system should preferably be a continuous length of chain. However, where there is a requirement to make a connection then only approved double locking connectors as in a Kenter link (see photograph below) should be used. The mooring pattern should be designed so that connectors are not subject to damage due to movement with the seabed. As we have stated previously, fibre mooring systems are more and more in use as water depths increase. This has necessitated the use of a combination of chain and fibre rope installations. To accommodate this situation new connectors have been developed as can be seen in the following photograph: Fibre to chain connector for deep water installations Kenter chain link connector showing parts and size ratios to the diameter 000134 Anchor buoys (surface and subsurface) Buoys are used for both surface and subsurface applications. The diagram below shows a subsurface buoy being used in a mooring installation to protect a pipeline. Subsurface buoys must have a suitable immersion rating for the application. In this case there should be a buoy “loss” detection system such as a tension monitor or a transponder attached to the buoy to indicate its location. Anchor support buoy This type of surface buoy is used as the location and pick up buoy for an anchor mooring system. In the anchor recovery operation the buoy is lassoed and hauled on deck. The buoy is secured, the buoy disconnected and the anchor pick up line transfered to the main winch line. The anchor is then heaved on deck, disconnected and secured. 000135 Subsurface modular support buoys These are typical of the type of buoy that would be used in the pipeline clearance as shown in the diagram above. Chain chasers and grapnels are also in use and, as their names imply, are for chasing out anchors where there is no pick up buoy due to loss or breakage. 6.5 Anchor Holding Capacity and Catenary Calculations Warranty surveyors will be involved in the design and/or approval of a mooring system. As part of the process the surveyor will have to inspect the components of the proposed system. The surveyor on site should also have sufficient knowledge to carry out basic calculations. He should be able to use tabular and graphical information available involving various parameters used in the mooring operation and installation of the system. These will include the following: > calculate the holding capacity of different anchors in different soil conditions > use anchor holding capacity tables > basic mooring line catenary calculations > use catenary curves In this computer world every warranty company will have its own approved computer programme to design a suitable mooring system for each individual case. This programme will calculate the mooring line lengths, catenaries, touchdown points and tension requirements. The holding capacity of an anchor is determined by the following parameters: • the fluke area (determined by the design) • the penetration of the anchor (determined by the soil type, anchor design, mooring line type and the applied load). The holding capacity of a chain mooring line is greater than a wire mooring line due to a higher friction factor. 000136 At this point we will look at the simple case of calculating the predicted holding capacity of an anchor. The basic formula used is as follows: Where HM = Anchor holding capacity HR = Soil factor as per the table WA = Weight of the anchor in pounds b = Exponent constant factor Example: An MODU has twenty tonne Bruce twin shank anc hors. Calculate the holding capacity on site where the seabed condition is soft clay. First we have to refer to the table below from which we obtain the HR as 189 kips Then the exponent constant factor as 0.92 (remember this is an exponent NOT a simple multiplier) Applying these to the formula gives: If you now refer to the holding capacity table below, for clay, you will see that it works out the same. In all situations the warranty company will apply design safety factors depending on the type of mooring, be it permanent or mobile. This may vary between 0.8 and 1.5. If the mooring is anchor piles or anchor suctions then different formulas are used as well as applying different safety factors Every anchor will have its own characteristics in any given condition. An anchor data sheet is shown on the following page giving holding capacity characteristics for a drag embedment anchor. It is fairly obvious but the data clearly shows that this type of anchor does not perform well on rocky seabeds. HM = HR ( )b WA 10,000lbs 189 ( 4 4 , 1 0 0 l b s )0.92 = 740.88 kips or 336 tonnes 10,000 000137 Table of factors for calculating anchor holding capacity using the above formula 000138 Soil description and drag anchor data for a typical HHP embedment anchor. This data, as well as the holding capacity graphs, will normally be produced by the manufacturers but the warranty company will in many cases do their own calculations to confirm any results. In the unlikely situation seabed condition data is not available or the seabed type is not covered by typical manufacturer’s data then the anchor capacity will be determined by proof loading using the maximum tension determined in the mooring system analysis. In the case of permanent moorings and moorings using vertical load anchors, e.g. StevManta or pile anchors, it is important that detailed soil data is available and a full geotechnical assessment will be carried out on site. 000139 As well as this data, uplift forces have to be taken into consideration. Modern drag embedment anchors, e.g. Bruce FFTS, are capable of resisting significant uplift forces. If an earlier design of drag anchor is to be used, which was not designed to resist uplift, then sufficient mooring line must be deployed to prevent uplift. Anchor holding capacity graphs for clay These graphs were actually reproduced by the American Petroleum Institute in 2005 from work done by the Naval Civil Engineering Laboratory. They are based on the ratio of the anchor weight and the holding capacity. They give the worst case scenario in soft clay. At the time there was insufficient data for some of the newer generation drag embedment anchors. 000140 A specific manufacturer’s anchor design specification and data sheets will be available which will give the required and relevant information for use in a mooring system analysis. As was stated in the earlier text in this section, these graphs do not include any safety factors. Anchor holding capacity graphs for sand The catenary calculations consist of determining the touchdown points, the suspension length and the distance between suspension points. In today’s computer age the warranty company will have an approved computer programme within its mooring system analysis procedure to determine all these parameters. We have presented the formulas used in making these calculations here for the student to gain knowledge of the factors involved. It is outside the remit of this unit to go into the proof behind these formulas or to expand into making specific computations. 000141 Formulas for calculating mooring line catenary points 000142 Example of calculating the suspended length given: T = Tension 12 tonnes W = Weight of cable @ 0.022 tonnes per meter D = Height of suspension point 50 meters As stated above, the warranty company will have a computer programme available to compute the mooring design and all the required mooring line information to achieve a safe and successful mooring operation. The following pages show monitor pictures from two computer programmes. There are many such programmes available on the market. The classification societies will give type approval to these computer programmes. These programmes are easy to use but as in all computer applications they are only as good as the information being input. D = (2 50( 1 2 – 502) = 228.1 metres 0.022 000143 Computer page showing basic input information Another system showing computer input data and calculation results page 000144 A good dimensional picture which shows the results in 3D schematic presentation which helps interpretation of the catenary results. 000145 6.7 Documentation The planning and preparation for a mooring operation should be undertaken well in advance such that all analyses can be conducted and all required documentation made available. The warranty company will require the full analysis report detailing the following: > location and vessel (e.g. MODU, FPSO ) specification and data > environmental loadings and motions > mooring analysis results also > a detailed mooring plan > comprehensive contingency plans > risk assessment reports The on site warranty surveyor will require: > certificates for all and every mooring component > manning plan > emergency response plans SAQ You are mooring an older semisubmersible MODU, offshore, over a well head. Using an 8 point chain anchor spread 15 tonne Stevpris anchors Water depth 150m Seabed condition – sand & clay 1. Describe how would you go about finding the holding capacity of the anchor s. 2. Given the information above, calculate the potential holding capacity of the anchor s. 000146 Chapter 7 7.0 New Developments Warranty surveyors and indeed the warranty company must keep up to date with the constant new developments in the offshore industry. In the past decade we have all seen the ever changing and ever demanding requirement for oil and gas. This coupled with offshore renewable energy sources such as wind, wave and tide mean that the offshore industry has had to constantly develop new processes, procedures, operational requirements and innovative means to fulfil these new demands. Wind farm installation southern North Sea Pelamis wave energy converter Wave Dragon Coastal inlet tidal energy generator 000147 The advent of the increasing size of the wind turbines in the offshore wind farm energy industry has seen the need for ever larger wind turbine installation vessels being built. The very large wind farm installation and maintenance vessels are being designed around the submersible dock ship concept with a floodable dock which is accessible from the stern. Artist’s impression of a new generation wind turbine installation vessel. The offshore wind farm industry has seen the need for specialist fast service craft. These smaller catamaran hulled craft are designed for near coastal shallow water work carrying maintenance equipment and maintenance engineers out to the wind farms. Fast catamaran service craft for the offshore wind energy industry 000148 As safety and emergency rescue and recovery become even more important in offshore operations and development, new specially built vessels are entering the offshore market. Specialist companies have been set up to build and operate this new breed of vessel known as ERRVs. These new craft have all the latest navigational, propulsion and rescue equipment on board including mother craft and fast rescue craft. The major oil companies now employ them to cover more than one installation or field. The Esvagt Bergen a new generation ERRV Deck handling equipment is one of the latest innovative additions to the operation of anchor handling vessels. Anchor handling operations in deeper and deeper water have forced manufacturers of anchor handling equipment to develop new technical solutions coupled with the need to enhance crew safety. Remote controlled anchor handling equipment Fibre rope tensioner for torpedo anchor deployment 000149 As can be seen, marine deck handling systems are very much in use in the industry today. The two deck hands are using a remote hand held operating console to control the anchor being recovered to the after deck. The artist’s impression is of a pretension fibre rope system to facilitate the deployment of large torpedo anchors in deep water. Heavy lift semisubmersible vessels have become larger and sometimes as radical in design as the Dockwise Type “O”. Semisubmersible heavy lift vessel Mighty Servant 1 Lift capacity approximately 45,000 tonnes Artist’s impression of the new generation semisubmersible heavy lift vessels Dockwise Type “O” She will have a lift capacity of approximately 100,000 tonnes 000150 The role of the warranty company and the work of the warranty surveyor is highly specialised and requires in-depth knowledge coupled with many years’ experience of the marine and offshore energy industry. This unit only covers, in broad terms, the areas that warranty surveyors will be expected to have a sound knowledge of to fulfil the very specialised tasks prior to the issuing of a CoA for offshore operations. The warranty company and indeed the warranty surveyor will also be involved in shoreside operations involving heavy lifts or loadouts for the offshore energy industry. Warranty companies will have their own guidelines for the processes and procedures involved in such loadout operations. Warranty companies will also be involved in very specific offshore operations from laying pipelines to running rock dumping, trenching, hook-ups and decommissioning operations. The recent requirements for exploration and production in ice affected areas of the world have brought new operational problems. The warranty companies have to keep up to date with all the latest developments and new innovations. 000151 000152. MWS-2-Appendices. The warranty surveyor in particular must take this situation in to account depending on the geographical area or region they are working in. ABS American Bureau of Shipping. AISC American Institute of Steel Construction. API American Petroleum Institute. Approved Bollard Pull Continuous static bollard pull is that obtained by a test at 100% of the Maximum Continuous Rating (MCR) of main engines, averaged over a period of 10 minutes. Where a certificate of Continuous Static Bollard Pull less than 10 years old can be produced, then this will normally be used as the Approved Bollard Pull. Approved Bollard Pull for tugs under 10 years old without a bollard pull certificate may be estimated as 1 tonne /100 (Cer tified) BHP of the main engines. Approved Bollard Pull for tugs over 10 years old, without a bollard pull certificate less than 10 years old, may be the greater of: • the certified value reduced by 1% per year of age since the BP test, or • 1 tonne/100 (Certified) BHP reduced by 1% per year of age greater than 10. ASPPR Arctic Shipping Pollution Prevention Regulations. Assured The Assured is the person who has been insured by some insurance company, or underwriter, against losses or perils mentioned in the policy of insurance. ATA Automatic Thruster Assist. Barge A nonpropelled vessel commonly used to carry cargo or equipment. Bending reduction The reduction factor applied to the breaking load of a rope or factor EB cable to take account of the reduction in strength caused by bending round a shackle, trunnion or crane hook. Page 4 of 166 Benign area An area that is free from tropical revolving storms and travelling depressions, (but excluding the North Indian Ocean during the Southwest monsoon season, and the South China Sea during the Northeast monsoon season). BHP / Brake Horse Power The measure of horsepower at continuous engine output after the combustion stage. BL (Breaking Load) Breaking load (BL) = Certified minimum breaking load of wire rope, chain or shackles, measured in tonnes. BP (Bollard Pull) Bollard pull (BP) = Certified continuous static bollard pull of a tug measured in tonnes. BV Bureau Veritas. Cable-laid sling A cable made up of 6 ropes laid up over a core rope with terminations at each end. Calculated Grommet The load at which a grommet will break. Breaking Load (CGBL) Calculated Rope The load at which a cable laid rope will break. Breaking Load (CRBL) Calculated Sling The load at which a sling will break. The breaking load for a sling Breaking Load (CSBL) takes into account the ‘Termination Efficiency Factor’. Cargo Where the item to be transported is carried on a barge or a vessel, it is referred to throughout this report as the cargo. If the item is towed on its own buoyancy, it is referred to as the tow. Cargo ship safety certificates Certificates issued by a certifying authority to attest that the (Safety Construction) vessel complies with the cargo ship construction and survey (Safety Equipment) regulations, has radiotelephone equipment compliant with (Safety Radio) requirements and carries safety equipment that complies with the rules applicable to that vessel type. Certificate validities vary and are subject to regular survey to ensure compliance. CASPRR Canadian Arctic Shipping Pollution Prevention Regulations. CBP / Continuous Bollard Pull See Approved Bollard Pull (above). Certificate of Approval (CoA) A formal document issued stating that, in its judgement and opinion, all reasonable checks, preparations and precautions have been taken to keep risks within acceptable limits, and an operation may proceed. Page 5 of 166 Consequence factor A factor to ensure that main structural members, lift points and spreader bars /frames have an increased factor of safety (including lateral loads) related to the consequence of their failure. Crane vessel The vessel, ship or barge on which lifting equipment is mounted. For the purposes of this report it is considered to include: crane barge, crane ship, derrick barge, floating shear-leg, heavy lift vessel, semisubmersible crane vessel (SSCV) and jack-up crane vessel. Classification A system of ensuring ships are built and maintained in accordance with the Rules of a particular Classification Society. Although not an absolute legal requirement, the advantages (especially as regards insurance) mean that almost all vessels are maintained in Class. Cold stacking Cold stacking is where the unit is expected to be moored up for a significant period of time and will have minimum or, in some cases, no services or personnel available. COSHH Control of Substances Hazardous to Health. Cribbing An arrangement of timber baulks, secured to the deck of a barge or vessel, formally designed to support the cargo, generally picking up the strong points in vessel and/or cargo. Demolition towage Towage of a “dead” vessel for scrapping. Deratisation Introduced to prevent the spread of rodent borne disease, Certification attesting the vessel is free of rodents (Derat Exemption Certificate) or has been satisfactorily fumigated to derat the vessel (Derat Certificate). Certificates are valid for 6 months unless further evidence of infestation found. Design environmental The design wave height, design wind speed, and other relevant condition environmental conditions specified for the design of a particular transportation or operation. Design wave height Typically the 10-year monthly extreme significant wave height, for the area and season of the particular transportation or operation. Design wind speed Typically the 10-year monthly extreme 1-minute wind velocity at a reference height of 10m above sea level, for the area and season of the particular transportation or operation. Determinate lift A lift where the slinging arrangement is such that the sling loads are statically determinate, and are not significantly affected by minor differences in sling length or elasticity. DNV Det Norske Veritas. Page 6 of 166 Double tow The operation of towing two tows with two tow wires by a single tug. DP Dynamic Positioning. Dry towage (or Dry tow) Transportation of a cargo on a barge towed by a tug. Commonly mis-used term for what is actually a voyage with a powered vessel, more properly referred to as ‘Dry Transportation’. Dry transportation Transportation of a cargo on a barge or a powered vessel. Dunnage See Cribbing. Dynamic Amplification Factor The factor by which the ‘gross weight’ is multiplied, to account for (DAF) accelerations and impacts during the lifting operation. EPIRB Emergency Position Indicating Radio Beacon. Flagged vessel A vessel entered in a national register of shipping with all the appropriate certificates. Floating offload The reverse of floating onload. Floating onload The operation of transferring a cargo, which itself is floating, onto a vessel or barge, which is submerged for the purpose. FLS Fatigue Limit State. FMEA Failure Modes and Effects Analysis. FOI Floating Offshore Installation. FOS Factor of Safety. FPSO Floating Production, Storage and Offload vessel. GL Germanischer Lloyd. GMDSS Global Maritime Distress and Safety System. GPS Global Positioning System. Grillage A steel structure secured to the deck of a barge or vessel, formally designed to support the cargo and distribute the loads between the cargo and barge or vessel. Grommet A grommet is comprised of a single length of unit rope laid up 6 times over a core to form an endless loop. Page 7 of 166 Gross weight The calculated or weighed weight of the structure to be lifted including a weight contingency factor and excluding lift rigging. See also NTE weight. HAZID Hazard Identification. Hook load The hook load is the ‘gross weight’ or NTE weight plus the ‘rigging weight’. Hot stacking Hot stacking may be defined as mooring the vessel in a manned functional condition, with the option to run machinery to provide sufficient power to operate all mooring winches, thrusters, etc. as may be required. IACS International Association of Classification Societies. IMDG Code International Maritime Dangerous Goods Code. IMO International Maritime Organisation. Independent leg jack-up A jack-up where the legs may be raised or lowered independently of each other. Indeterminate lift Any lift where the sling loads are not statically determinate. Inshore mooring A mooring operation in relatively sheltered coastal waters, but not at a quayside. Insurance warranty A clause in the insurance policy for a particular venture, requiring the approval of a marine operation by a specified independent survey company. IOPP Certificate International Oil Pollution Prevention Certificate (see also MARPOL). ISM Code International Safety Management Code - the International Management Code for the Safe Operation of Ships and for Pollution Prevention - SOLAS Chapter IX. Jack-up A self-elevating MODU, MOU or similar, equipped with legs and jacking systems capable of lifting the hull clear of the water. LAT Lowest Astronomical Tide. Lift point The connection between the ‘rigging’ and the ‘structure’ to be lifted. May include ‘padear’, ‘padeye’ or ‘trunnion’. Line pipe Coated or uncoated steel pipe sections, intended to be assembled into a pipeline. Page 8 of 166 LOA Length Over All. Loading The transfer of a major assembly or a module from a barge onto land by horizontal movement or by lifting. Load line The maximum depth to which a ship may be loaded in the prevailing circumstances in respect to zones, areas and seasonal periods. A Loadline Certificate is subject to regular surveys, and remains valid for 5 years unless significant structural changes are made. Loadout Transferring a cargo onto a vessel or barge, from the shore or from another vessel or barge. Location move A move of a MODU or similar, which, although not falling within the definition of a field 24-hour move, may be expected to be completed with the unit essentially in 24-hour field move configuration, without overstressing or otherwise endangering the unit, having due regard to the length of the move, and to the area (including availability of shelter points) and season. LRFD Load and Resistance Factor Design. LRS Lloyds Register of Shipping. Marine operation See Operation. MARPOL International Convention for the Prevention of Pollution from Ships 1973/78, as amended. Matched pair of slings A matched pair of slings are fabricated or designed so that the difference does not exceed 0.5d, where ‘d’ is the nominal diameter of the sling or grommet. Mat-supported jack-up A jack-up which is supported in the operating mode on a mat structure, into which the legs are connected and which therefore may not be raised or lowered independently of each other. MBL / Minimum Breaking Certified Minimum Breaking Load of wire rope, chain, stretcher or Load (MBL) shackle in tonnes. MBP / Maximum Bollard Pull The bollard pull obtained by a test, typically at 110% of the Maximum Continuous Rating (MCR) of main engines, over a period of 5 minutes. MCR / Maximum Manufacturer’s recommended Maximum Continuous Rating of the Continuous Rating main engines. Mechanical termination A sling eye termination formed by use of a ferrule that is mechanically swaged onto the rope. Page 9 of 166 Minimum Breaking The minimum allowable value of ‘breaking load’ for a particular sling Load (MBL) or grommet. Multiple tow The operation of towing more than one tow by a single tug. Mobile mooring Mooring system, generally retrievable, intended for deployment at a specific location for a short-term duration, such as those for mobile offshore units. MODU Mobile Offshore Drilling Unit. Mooring system Consists of all the components in the mooring system including shackles windlasses and other equipment and in addition, rig/vessel and shore attachments such as bollards. MOU Mobile Offshore Unit. For the purposes of this unit, the term may include mobile offshore drilling units (MODUs), and non-drilling mobile units such as accommodation, construction, lifting or production units. n/a Not applicable. NDT Non Destructive Testing. Net weight The calculated or weighed weight of a structure, with no contingency or weighing allowance. NMD Norwegian Maritime Directorate. NTE Weight A Not To Exceed weight, sometimes used in projects to define the maximum possible weight of a particular structure. Ocean towage Any towage which does not fall within the definition of a restricted operation, or any towage of a MODU or similar which does not fall within the definition of a 24-hour move or location move. Ocean transportation Any transportation which does not fall within the definition of a restricted operation. OCIMF Oil Companies International Marine Forum. Off-hire survey A survey carried out at the time a vessel, barge, tug or other equipment is taken off-hire, to establish the condition, damages, equipment status and quantities of consumables, intended to be compared with the on-hire survey as a basis for establishing costs and liabilities. Offload The reverse of Loadout (see above). Page 10 of 166 On-hire survey A survey carried out at the time a vessel, barge, tug or other equipment is taken on-hire, to establish the condition, any preexisting damages, equipment status and quantities of consumables. It is intended to be compared with the off-hire survey as a basis for establishing costs and liabilities. It is not intended to confirm the suitability of the equipment to perform a particular operation. Operation, marine operation Any activity, including loadout, transportation, offload or installation, which is subject to the potential hazards of weather, tides, marine equipment and the marine environment. Operational Reference Period The planned duration of the operation, including a contingency period. Padear A lift point consisting of a central member, which may be of tubular or flat plate form, with horizontal trunnions round which a sling or grommet may be passed. Padeye A lift point consisting essentially of a plate, reinforced by cheek plates if necessary, with a hole through which a shackle may be connected. Parallel tow The operation of towing two tows with one tow wire by a single tug, the second tow being connected to a point on the tow wire ahead of the first tow with the catenary of its tow wire passing beneath the first tow. Permanent mooring Mooring system normally used to moor floating structures deployed for long-term operations, such as those for a floating production system. Pipe carrier A vessel specifically designed or fitted out to carry Line pipe. Port of refuge A location where a towage or a vessel seeks refuge, as decided by the master, due to events occurring which prevent the towage or vessel proceeding towards the planned destination. A safe haven where a towage or voyage may seek shelter for survey and/or repairs, when damage is known or suspected. Procedure A documented method statement for carrying out an operation. PSA Petroleum Safety Authority Norway QTF / Quadratic Refers to the matrix that defines second order mean wave loads Transfer Function on a vessel in bichromatic waves. When combined with a wave spectrum the mean wave drift loads and low frequency loads can be calculated. Quayside mooring A mooring that locates a vessel alongside a quay (usually at a sheltered location). Page 11 of 166 RAO / Response Defines the vessel’s (first order) response in regular waves and Amplitude Operator allows calculation of vessel wave frequency (first order) motion in a given seastate using spectral analysis techniques. Redundancy check Check of the failure loadcase associated with the applicable extreme (survival) environment, e.g. the one leg damaged case. Register The list published from time to time of towing vessels, including all towing vessels entered into the Towing Vessel Approvability Scheme. Registry Registry indicates who may be entitled to the privileges of the national flag, gives evidence of title of ownership of the ship as property and is required by the need of countries to be able to enforce their laws and exercise jurisdiction over their ships. The Certificate of Registry remains valid indefinitely unless name, flag or ownership changes. Rigging The slings, shackles and other devices including spreaders used to connect the structure to be lifted to the crane. Rigging weight The total weight of rigging, including slings, shackles and spreaders, including contingency. Risk assessment A method of hazard identification where all factors relating to a particular operation are considered. Rope The unit rope from which a cable laid sling or grommet may be constructed, made from either 6 or 8 strands around a steel core. Safe Working Load (SWL) See Working Load Limit (WLL). Safety Management A document issued to a ship which signifies that the Company and Certificate (SMC) its shipboard management operate in accordance with the approved SMS. Safety Management A structured and documented system enabling Company personnel System (SMS) to implement the Company safety environmental protection policy. SART Search and Rescue Radar Transponder. Seafastening The means of preventing movement of the cargo or other items carried on or within the barge, vessel, or tow. Self-Elevating Unit More commonly know as a ‘Jack-up’. It is a Marine Unit equipped with legs and jacking systems capable of lifting the hull clear of the water. A ‘Jack-up’ unit may be used as a production platform, drilling platform, construction support platform or accommodation platform. Page 12 of 166 Semisubmersible A MODU or similar designed to operate afloat, generally floating on columns which reduce the water-plane area, and often moored to the seabed when operating. SemiSubmersible Unit A floating structure normally consisting of a deck structure with a number of widely spaced, large cross-section, supporting columns connected to submerged pontoons. Shelter point An area or safe haven where a towage or vessel may seek shelter, (or shelter port, in the event of actual or forecast weather outside the design limits or point of shelter) for the transportation concerned. A planned holding point for a staged transportation. Single laid sling A cable made up of 6 ropes laid up over a core rope. Single tow The operation of towing a single tow with a single tug. Skew Load Factor (SKL) The factor by which the load on any lift point or pair of lift points and rigging is multiplied to account for sling length mismatch in a statically indeterminate lift. Sling breaking load The breaking load of a ‘sling’, being the calculated breaking load reduced by ‘termination efficiency factor’ or ‘bending reduction factor’ as appropriate. Sling eye A loop at each end of a sling, either formed by a splice or mechanical termination. SLS / Serviceability A design condition defined as a normal Ser viceability Limit State / Limit State normal operating case. SOPEP Shipboard Oil Pollution Emergency Plan. Splice That length of sling where the rope is connected back into itself by tucking the tails of the unit ropes back through the main body of the rope, after forming the sling eye. Spreader bar (frame) A spreader bar or frame is a structure designed to resist the compression forces induced by angled slings, by altering the line of action of the force on a lift point into a vertical plane. The structure shall also resist bending moments due to geometry and tolerances. Staged transportation A transportation which can proceed in stages between shelter points, not leaving or passing each shelter point unless there is a suitable weather forecast for the next stage. Each stage may, subject to certain safeguards, be considered a weather-restricted operation. Page 13 of 166 Structure The object to be lifted. Submersible transport vessel A vessel which is designed to ballast down to submerge its main deck, to allow self-floating cargoes to be on-loaded and off-loaded. Suitability survey A survey intended to assess the suitability of a tug, barge, vessel or other equipment to perform its intended purpose. Different and distinct from an on-hire survey. Survey Inspection of commodity, structure or item for the purposes of determining condition, quantity, quality or suitability. SWL Safe Working Load in tonnes. Tandem tow The operation of towing two or more tows in series with one tow wire from a single tug, the second and subsequent tows being connected to the stern of the tow in front. TA Thruster Assist. Termination efficiency The factor by which the breaking load of a wire or cable factor ET is multiplied to take account of the reduction of breaking load caused by a splice or mechanical termination. Trunnion A lift point consisting of a horizontal tubular cantilever, round which a sling or grommet may be passed. An upending trunnion is used to rotate a structure from horizontal to vertical, or vice versa, and the trunnion forms a bearing round which the sling, grommet or another structure will rotate. Tonnage A measurement of a vessel in terms of the displacement of the volume of water in which it floats, or alternatively, a measurement of the volume of the cargo carrying spaces on the vessel. Tonnage measurements are principally used for freight and other revenue based calculations. Tonnage Certificates remain valid indefinitely unless significant structural changes are made. Tonnes Metric tonnes of 1,000 kg (approximately 2,204.6 lbs) are used throughout this document. The necessary conversions must be made for equipment rated in long tons (2,240 lbs, approximately 1,016 kg) or short tons (2,000 lbs, approximately 907 kg). Tow The item being towed. This may be a barge or vessel (laden or unladen) or an item floating on its own buoyancy. Approval of the tow will normally include, as applicable: consideration of condition and classification of the barge or vessel; strength, securing and weather protection of the cargo, draught, stability, documentation, emergency equipment, lights, shapes and signals, fuel and other consumable supplies, manning. Page 14 of 166 Towage The operation of transporting a non-propelled barge or vessel (whether laden or not with cargo) or other floating object by towing it with a tug. Towing (or towage) The procedures for effecting the towage. Approval of the towing arrangements (or towage) arrangements will normally include consideration of towlines and towline connections, weather forecasting, pilotage, routeing arrangements, points of shelter, bunkering arrangements, assisting tugs, communication procedures. Towing Vessel Approvability A document issued by warranty companies stating that a towing Certificate (TVAC) vessel complied with the requirements at the time of survey, or was reportedly unchanged at the time of revalidation, in terms of design, construction, equipment and condition, and is considered suitable for use in towing service within the limitations of its category, bollard pull and any geographical limitations which may be imposed. Towing Vessel Approvability The scheme whereby owners of towing vessels may apply to a Scheme (TVAS) warranty company to have their vessels surveyed, leading to the issue of a TVAC. Towline connection strength Towline connection strength (TC) = ultimate load capacity of towline connections, including connections to barge, bridle and bridle apex, in tonnes. Towline pull required (TPR) The towline pull computed to hold the tow, or make a certain speed against a defined weather condition, in tonnes. Transportation The operation of transporting a tow or a cargo by a towage or a voyage. Tug The vessel performing a towage. Approval of the tug will normally include consideration of the general design; classification; condition; towing equipment; bunkers and other consumable supplies; emergency and salvage equipment; communication equipment; manning. Tug efficiency (Te) Defined as: effective bollard pull produced in the weather considered certified continuous static bollard pull. UKCS United Kingdom Continental Shelf. ULS / Ultimate Limit State The intact loadcase associated with the applicable extreme (survival) environment. Page 15 of 166 Ultimate Load Ultimate load capacity of a wire rope, chain or shackle or similar Capacity (ULC) is the certified minimum breaking load, in tonnes. The load factors allow for good quality splices in wire rope. Ultimate load capacity of a padeye, clench plate, delta plate or similar structure, is defined as the load, in tonnes, which will cause general failure of the structure or its connection into the barge or other structure. Unrestricted operation A marine operation which cannot be completed within the limits of a favourable weather forecast (generally less than 72 hours). The design weather conditions must reflect the statistical extremes for the area and season. Vessel A marine craft designed for the purpose of transportation by sea. VLA Vertical Load Anchors. Voyage For the purposes of this report, the operation of transporting a cargo on a powered vessel from one location to another. Watertight A watertight opening is an opening fitted with a closure designated by Class as watertight, and maintained as such, or is fully blanked off so that no leakage can occur when fully submerged. Weather unrestricted An operation with an operational reference period generally operation greater than 72 hours. The design environmental condition for such an operation shall be set in accordance with extreme statistical data. Weather restricted An operation with an operational reference period generally less operation than 72 hours. The design environmental condition for such an operation may be set independent of extreme statistical data, subject to certain precautions. Weathertight A weathertight opening is an opening closed so that it is able to resist any significant leakage from one direction only, when temporarily immersed in green water or fully submerged. WLL / Working Load Limit The maximum static load that the wire, cable or shackle is designed to withstand. WMO World Meteorological Organisation. WPS Welding Procedure Specification. WSD Working Stress Design. 9-Part sling A sling made from a single laid sling braided nine times with the single laid sling eyes forming each eye of the 9-part sling. Page 16 of 166 Appendix B Example of a Certificate of Approval (CoA) Page 17 of 166 Appendix C IADC General Ocean Tow Recommendations for Jack-Up Drilling Units GENERAL OCEAN TOW RECOMMENDATIONS FOR JACKUP DRILLING UNITS International Association of Drilling Contractors (I.A.D.C.) February 13, 1991 Manning 1. Manning should comply with U.S. Coast Guard regulations or other national regulatory rules. The number of crew will be dependent on the length of the voyage and be limited to essential personnel only and should not exceed 50 % of lifeboat capacity. Ocean Tow Loading Plan 2. A Loading Plan should be formulated and, if required, submitted to the Underwriter’s Marine Survey company utilized by the Contractor for the tow in time for proper review. (See Addendum A enclosed for a sample loading plan) 3. Cargo is defined as any material, temporary structure, shipping container, consumable item, machinery, tubular, equipment and items not included in the drill barge lightship weight. 4. Stowage of on the main weather deck of a Jackup drilling unit while on an ocean tow is not desirable and should be avoided with the exceptions noted below. 5. Exceptions to this policy my be permitted if: a. A permanent structure has been erected for the stowing and securing of an item such as a pipe rack for drill pipe and drill collars, or a mandrel and locking beams for a BOP. The permanent structures should be adequate for their intended purpose, reviewed, and approved by a classification society in accordance with the appropriate rules. b. Cargo is elevated or located above the main deck by mans of a suitable support structure. c. Temporary structures are permitted when designed by a registered professional engineer and approved by the underwriter’s marine surveyor. Towage 6. One set of up-to-date navigation charts and pilot books for the tow course and alternate courses should be available for the voyage aboard the rig including detailed charts of ports of refuge. 7. Tow routing should be determined in advance including ports of refuge and the required entry data. Page 18 of 166 8. A weather service should be selected with a beck ground in ocean tow forecasting. Weather updates should be sent every 12 hours with at least 72 hour advance forecasts. Direct communication with a marine weather forecaster is recommended. 9. The Towing vessel(s), and towing gear, should be designed and equipped for towing in ocean service with full crew aboard. Towing gear should be inspected and approved by the attending marine and the O.I.M. prior to departure. 10. The bollard pull of the towing vessel(s) should be of sufficient size for the intended tow. 11. Communication means between the rig and the towing vessel(s) is of utmost importance. Backup communications should be provided. The vessel should provide a qualified riding crew member to assist the rig crew during tow. Language should not be a barrier. 12. Critical motion curves should be provided to the rig crew and the towing vessel(s) prior to departure. (see addendum B) Manufacture recommendations for proper leg length and shimming should be adhered to for the tow. 13. An emergency towing line should be strapped along the side of the hull just below top deck level in a manner permitting quick release. The tow line should be of a size suitable for the tow intended accounting for the bollard pull of the tow vessel(s), including shock loads. 14. A polypropylene shock line, the size and length suitable for the bollard pull of the tow vessel(s) being used, should be attached to the emergency tow line with suitable connectors. 15. A main tow line bridle recovery line(s) should be fitted and run from the and of the bridle or tow plate to a winch on the barge to allow retrieval in the main tow wire(s) part. Stability 16. Stability calculations addressing the tow conditions should be performed to insure positive stability in compliance with the rig operating manual. These calculations should be submitted to and approved by the underwriter’s Marine Survey company being utilized in time for proper review. (see Addendum A) Draft and Trim 17. Within the limits of the loadline certificate, the man draft for the tow should be determined from the stability calculations in item 16 above. 18. Weight should be distributed to produce a level condition transversely with a slight trim by the stern. Trim is to be obtained by locating material or equipment carried with necessary liquid trimming ballast kept to a minimum. 19. Liquid variable load should be kept to a minimum. Hull tanks that contain liquids should be pressed and maintained full during the voyage. 20. All tanks, including active mud tanks, not required on the voyage, should be empty at the time of departure. Page 19 of 166 Watertight Integrity 21. The operating manual for the rig should clearly show the location of watertight closures and should be complied with during the tow. 22. Deck openings such as sounding tubes should be protected from damage 23. Consideration should be given to the modification all weather deck preload hatch covers, vent fan covers, cargo hatch cover, etc. with clamp bars or welded strapping to prevent opening from sea action. 24. Rig service take on lines Such as out, barite, fuel, potable water, or drill water located on the outer lull areas should be capped and protected from sea damage by sea action. 25. All weather/watertight closures, ventilation ducts, etc. with the exception of intakes necessary for the operation of the vessel, should be seed from sea action. Pumping Arrangements 26. The vessel’s bilge/ballast service pumps should be tested and determined to be in good working order prior to departure. Pumps are to be maintained in a state of readiness throughout the tow. Compartment Sounding 27. All hull compartments and void spaces should be fitted with sounding tubes. All sounding tubes should be clearly identified and fitted with caps that are capable of being tightly secured. 28. Soundings should be taken at least every 12 hours of all void and preload tanks. Hull compartments should be inspected or sounded also and the results should be logged for the duration of the 29. A diagram of the sounding tube locations should be posted in the machinery deck spaces and in the control room. 30. A means of determining the changes in liquid levels in the perimeter hull tanks must be available for use from a protected location. 31. The manufacturer’s data should be furnished to indicate that the derrick can withstand the roll motions anticipated for the tow. This data should be in the rig operating manual. 32. All Derrick travelling equipment should be seared for the tow. 33. Bow anchors should be removed from below water racks and strapped to the deck or stored if there is the possibility of becoming entangled in the tow gear. 34. Secure or remove anchor buoys from their racks to prevent dislodging by sea action. Cranes 35. Crane should be lowered into steel support structures and secured against vertical or lateral movement. 36. Cranes should be secured against revolving per manufactures recommendations. Page 20 of 166 Navigation Lights, Signals and Safety Equipment 37. Side Lights and stern light should be checked to make sure they are in good working order. 38. Life vests, throw over life rings and other means of rescue should be checked and readied for deployment, if need. 39. Signalling devices should be stored in the control room, inspected and determined that they are within inspection dates for use, if needed. Potable Water and Fuel Oil 40. Sufficient potable water and fuel for the length of the tow, plus 25% safety factor, should be carried. 41. A potable pump should be available to obtain water from the potable water tanks in the event of pump failure. 42. Because sediment in the fuel tanks can be stirred up during tow, a centrifuge should be installed prior to departure to remove contaminants from the fuel pumped to the engine day tanks. Extra engine fuel filters should be in supply. Damage Control 43. The following emergency and/or damage control equipment and material is recommended to carried aboard for the tow, or it’s equivalent. 400 lbs. cement 400 lbs. sad 20 lbs. concrete mix accelerator 40 ft. of 1” x 12” timber 24 lbs. of oakum or similar caulking compound 24 wooden wedges 24 wooden plugs of various sizes Welding and cutting apparatus 50 ft. of 4” x 4” angle iron 100 sq. ft. of 1/2” steel plate. 100 sq. ft. of 1” steel plate 500 ft. 1” polypropylene rope 500 ft. 1” wire rope 20 Ton Portapower hydraulic jack 100 ft. 2” x 4” x 10’ timber Two portable diaphragm air pumps 44. Spare shackle, heaving lines, turnbuckles, etc. should be aboard for the tow. 45. Fog horn, ship whistle or bell, search light, etc. should be in operating condition. Page 21 of 166 46. Secure all equipment in the accommodations area for heavy seas. 47. Strip water from the preload tanks, unused drill water tanks and void tanks prior to and during the tow. 48. Lifeboat machinery and equipment should be checked for compliance with existing regulations and be in proper operating condition. Lifeboat fuel tanks should be checked for contaminants and feel cleaned or replaced as necessary Spare fuel filters should be stowed aboard the lifeboat for use, if required. 49. The emergency power source should be available for use at all times and teed at periodic intervals Riding Crew Instructions 50. Sea watches should be maintained at all times during the tow. The following information should be entered into the log: a. Weather data including; wind force, wave/swell height/Period. b. Motion characteristics of the vessel are of the utmost importance. The Drill Barge Master (licensed or unlicensed) must observe degrees of pitch and roll and their corresponding periods and request the tug to change course and/or speed to prevent the Drill Barge motions from exceeding the values given in the Operations Manual critical motion curves. c. All important communication with the towing vessel(s) including speed, course, change in tow wire length, etc. should be recorded. d. me Position should be obtained from the towing vessel(s) every 6 hours and recorded in the rig log. 51. Each hull tank should be sounded and logged every 12 hours. 52. All watertight doors between compartment and from the compartments to outside exits should be kept closed at all times except when personnel pass. 53. Tow gear should be inspected every 6 hours and the results logged. 54. At least two (2) members of the crew should be awake at all times. 55. Radio contact mist be maintained on a 24 hour basis with the tow vessel(s). 56. Emergency drills should be held prior to departure and once a week during the tow. Results should be logged. 57. All navigation lights should be checked every 6 hours and the results logged. 58. Daily reports are should be forwarded to the Contractor’s headquarters at least daily. Page 22 of 166 OCEAN TOW LOADING PLAN ADDENDUM A February 13, 1991 ADDENDUM A TO: General Marine Surveyor Company FROM: United Marine Drilling Contractors SUBJ: Ocean Tow Stowage Plan Please review the enclosed Ocean Tow Loading Plan for our 116 class hull. The loading plan is comprised of the following: 1. A completed loading calculation for the start of the tow based on the latest information from our rig survey. The stability calculations are based on two leg down positions (12.17 ft. for 70 knots and 45.90 ft. for severe storm). 2. All loose gear will be stowed below deck in stowage areas 11 through 13 and secured to prevent shifting during the tow. (see enclosed drawings) 3. The drilling tubulars will be secured with turnbuckles and chain and containment barriers will be fabricated at the ends of the racks, subject to your final approval. Four areas are anticipated at this time. (see enclosed drawings) 4. Two miscellaneous cargo areas will be constructed on top of the quarters in containment areas in order to remove these items from possible sea action. (see enclosed drawings) 5. The Substructure/drill floor assembly will be in the full forward position for the tow and secured to the hull with the clamping arrangement provided by the manufacturer. 6. The emergency tow gear will be strapped along the port side of the hull and provisions made for the deployment in severe weather if the need should arise. 7. The deepwell tower will be secured to the hull with clamping arrangements designed by the manufacturer. Three 3/4 inch guy wires will be connected to the tower in three different directions securing the tower from the rig motions anticipated. Please review the Loading Plan provided at this time. As you know, final loading will depend on your survey prior to the departure of the rig. Page 23 of 166 Page 24 of 166 Page 25 of 166 Page 26 of 166 Page 27 of 166 Page 28 of 166 Page 29 of 166 Page 30 of 166 Page 31 of 166 ADDENDUM B February 13, 1991 Page 32 of 166 Appendix D JRC Marine Warranty Surveyors Code of Practice and scope of Work Joint Rig Committee Room 358, Lloyd’s, One Lime Street London EC3M 7DQ Tel: (+44) 020 7327 3333 Fax: (+44) 020 7327 4443 _____________________________________________________________________________________ PRIVATE AND CONFIDENTIAL Enquiries to: JR 2010/010 John Gurtenne 23 July 2010 (Direct Dial 020 7327 4045) Joint Rig Committee Marine Warranty Surveyors Code of Practice and Scope of Work (JR 2010/010) Attached for underwriters use and information is a copy of the revised Joint Rig Committee Marine Warranty Surveyors Code of Practice (CoP) and Generic Scope of Work (GSoW) (JR2009/002), drawn up by JRC after consultation with surveyors, and others.. This Code of Practice and Generic Scope of Work replaces the 2004 Code of Practice and 2005 Generic Scope of Work previously issued by JRC. It is now presented as a single document which underwriters may use as an Endorsement to marine energy coverages they are issuing. In common with all JRC produced Clauses, this Clause is published by JRC, but it is expressly non-binding and JRC makes no recommendation as to its use in particular policies. Underwriters are of course free to offer different policy wordings and clauses to their policy holders. The Code of Practice and Scope of Work has the following objectives: To: • Clarify the respective roles of the Marine Warranty Surveyor, the Assured, and Underwriters • Define the function of the Marine Warranty Surveyor’s Scope of Work. • Outline criteria for Marine Warranty Surveying activities. • Establish guidelines for communication with underwriters. This Endorsement also gives Underwriters the option of specifying the application of an Project Specific Scope of Work (PSoW) where they think this is required, Should underwriters have any questions on the background, & use of this Code of Practice and Scope of Work, please contact John Gurtenne, secretary to the Joint Rig Committee (john.gurtenne@lmalloyds.com 020 7327 4045, or Len Messenger, Chairman of the JRC’s Engineering and Survey Sub-Committee, on 020 7648 3577. Simon Williams Chairman Joint Rig Committee Page 33 of 166 MARINE WARRANTY SURVEY 1) Coverage under this Policy for project activities is conditional upon: a) A Marine Warranty Surveyor being appointed by the Assured from the following panel _______________________________________________________1 on or before _ _ /_ _ / _ 2; and b) Issuance of the Certificates of Approval (C of A’s) by the Marine Warranty Surveyor for each operation as specified in the Generic Scope of Work (GSOW) contained herein or the Project Specific Scope of Work (PSOW) explicitly agreed by Underwriters. A kick off meeting is required Yes/No3 2) It is the duty of the Assured to procure the compliance with all recommendations, requirements or restrictions of the Marine Warranty Surveyor within the specified timescales. In the event of a breach of this duty, Underwriters will not be liable for any loss, damage, liability or expense arising from or contributed to by such breach. 3) The Marine Warranty Survey shall be conducted in accordance with the Marine Warranty Surveyor Code of Practice (CoP) and the GSOW contained herein (or the Project specific Scope of Work (PSOW) as agreed by the Contract leader(s)). A material change to the project will require a review of the Scope of Work. 4) The cost of the Marine Warranty Survey will be borne by the Assured. 5) Any expenses incurred to comply with the Marine Warranty Surveyor’s recommendations will be solely at the expense of the Assured. 6) The Marine Warranty Surveyor shall not be restricted from furnishing information to or consulting in an unrestricted manner with Underwriters. 7) Underwriters shall be entitled to receive a copy of any recommendations and/or reports directly from the Marine Warranty Surveyor. ___________________ 1 Names of MWS Companies to be inserted 2 Date to be inserted 3 Circle required option. Page 34 of 166 Joint Rig Committee Marine Warranty Surveyors’ Code of Practice (CoP) 2010 This CoP has been produced in order to establish agreed standards for Marine Warranty Surveyors’ performance while conducting Marine Warranty Surveys. It has the following objectives: To: · Clarify the role of the Marine Warranty Surveyor. · Define the function of the Marine Warranty Survey Scope of Work. · Outline approval criteria for Marine Warranty Surveying activities. · Establish minimum standards for Marine Warranty Surveyor performance. · Define lines of communication between Underwriters and the Marine Warranty Surveyor. Nothing in this CoP shall relieve any party of any legal obligations existing in the absence of this document The Code of Practice outlines the obligations for the Marine Warranty Surveyor, the Assured & the Underwriter. The Code of Practice includes a Generic Scope of Work (GSOW) in tabular format. A tailored Project Specific Scope of Work (PSOW) may be substituted for the GSOW with the explicit agreement of Underwriters. 1 Role of the Marine Warranty Surveyor 1.1 The fundamental objective of the Marine Warranty Surveyor is to make reasonable endeavours to ensure that the risks associated with the warranted operations to which a Marine Warranty Surveyor is appointed are reduced to an acceptable level in accordance with best industry practice. 1.2 The Marine Warranty Surveyor Company will only appoint personnel who are demonstrably competent, in terms of qualifications and experience, to perform the review/approval activity being undertaken in accordance with the Marine Warranty Scope of Work. 1.3 The Marine Warranty Surveyor will be satisfied, so far as possible, that the operations are conducted in accordance with: · recognised codes of practice for design and operations; · best industry practice appropriate for the vessels, equipment and location; · vessels and equipment being used within defined safe operating limits. 1.4 The Marine Warranty Surveyor will make available to Underwriters: · an opinion on the adequacy of the Marine Warranty Scope of Work; · particulars of the experience of the key personnel to be engaged; · a schedule of actual and proposed site attendances; · a schedule of Certificates of Approval to be issued. 1.5 The Marine Warranty Surveyor shall perform a review of the relevant documentation in accordance with the requirements of Item 1.3 above relating to the proposed operations within the Marine Warranty Scope of Work including, but not limited to: · calculations; · drawings; · procedures; · certificates; · manuals; · relevant reports. 1.6 The Marine Warranty Surveyor shall carry out suitability surveys of vessels, structures and equipment prior to each operation, including any required follow up “close out” inspections unless otherwise defined in the Marine Warranty Scope of Work, and shall: Page 35 of 166 · establish that the relevant items are suitable for the proposed operations; · make known, in clear terms, in writing to the Assured the recommendations to be implemented prior to commencement of the proposed operations; · make known, in clear terms, in writing to the Assured the recommendations to be implemented during the period of the proposed operations; · review metocean conditions and, where appropriate, incorporate requirements as to metocean conditions in the recommendations in the Certificate(s) of Approval; · observe and record the preparations for the proposed operations; · attend and witness critical function tests or relevant assurance tests. 1.7 Subject to the Marine Warranty Surveyor being satisfied that the objectives outlined under Items 1.1 above will be met, the Marine Warranty Surveyor will issue a Certificate of Approval. The Certificate of Approval will clearly identify: · the operation to be carried out; · the vessel(s) to be used; · recommendations to be satisfied during the period of the proposed operations within the Marine Warranty Scope of Work. Recommendations issued for the Assured’s implementation should be targeted to reduce risk to Underwriters and worded in a clear and explicit manner and whether the recommendation has been implemented or not should be capable of being objectively verified. 1.8 The Marine Warranty Surveyor will: · advise Contract leader(s) when a confidentiality agreement with the Assured is in place which would preclude the exchange of information or communication with Contract leader(s); · not provide any other services to the Assured and/or Operator and/or Main Contractor(s) and/ or Sub Contractor(s)that could present a conflict of interest with the Marine Warranty Work, for example: i) Marine or Design Consultant involved in a/ Design of project components to be used in a marine operation, the failure of which could compromise the integrity of a project asset (for example a lift beam or padeye). b/ Primary analysis of structures, hulls or component parts thereof. Note: the Marine Warranty Surveyor is however expected to review a design by others where this has a direct bearing on the marine risk e.g. check of the strength of launch frames on a launch jacket, or assessment of a lift analysis of a deck. c/ The production of procedures, project standards, risk assessments and other management documentation which influences how a marine operation is conducted and which has a direct bearing on the risk of a particular marine operation e.g. loadout, launch, lift of a jacket. ii) Loss adjuster iii) Classification Authority iv) Verification 1.9 The Marine Warranty Surveyor will immediately advise Contract leader(s), with a copy to the Assured: · if any Certificate of Approval is withheld; or a Non Conformance Certificate issued; · if the Assured fails to comply with any recommendations made by the Marine Warranty Surveyor; · of any proposed changes to relevant key personnel employed by the Marine Warranty Surveyor. 1.10 The Marine Warranty Surveyor will issue the following status reports to the Contract leader(s) direct at key risk milestones: · the marine warranty survey activity carried out in the period; · the marine warranty survey activity planned prior to the next risk milestone; · copies of Certificate(s) of Approval issued since the last report. Page 36 of 166 If the Assured has provided insufficient information to perform a comprehensive review or the Marine Warranty Surveyor’s questions/requests for information remain pending, then the Marine Warranty Surveyor shall make this clear in his reports to Underwriters and outline the potential implications of the omissions. 1.11 All equipment and vessels associated with load-out, transportation and installation activities shall be fully operational and used within their safe working limits, which shall be agreed by the Marine Warranty Surveyor. All vessels (including offshore cranes, pipelay vessels, rigs and flotels) to be in IACS Class. Marine Warranty surveyor to agree all outstanding Class items as not material to intended operations. Marine Warranty surveyor to approve limiting metocean criteria, and weather windows for all marine operations. 2 Role of the Assured 2.1 Once appointed on the project the Marine Warranty Survey Company shall not be changed without the express and prior agreement of the Contract leader(s). 2.2 The Assured shall provide the Marine Warranty Surveyor with a point of contact for the Contract leader(s) and an appropriate point of contact in the Assured’s organisation to assist with the resolution of queries. 2.3 The Assured will provide Contract leader(s) with the contact details of the Marine Warranty Surveyor(s) within 14 working days following appointment of the same. 2.4 The Assured will provide the Marine Warranty Surveyor(s) with the contact details of Contract leader(s) within 14 working days following appointment of the same. 2.5 The Assured shall procure Marine Warranty Surveyor participation at all relevant project management meetings, including marine operation HAZOPs/HAZID, contingency planning and assurance/testing plans. 2.6 The Assured shall contract the Marine Warranty Surveyor directly (without the involvement of any contractor or intermediary) unless required to enable compliance with the law in the jurisdiction or government regulations. 2.7 The Assured shall appoint a single Marine Warranty Survey Company for the entire scope of work herein. 3 Role of the Underwriters 3.1 The Panel of Marine Warranty Surveyors is to be agreed by the Contract leader(s). Other additions to the panel will need to demonstrate their capability/ experience of similar projects and water depths, and to be agreed by the Contract leader(s). 3.2 On each project Underwriters will specify whether a Kick Off meeting is required between Underwriters, the Assured and the Marine Warranty Surveyor. The Assured, Contract leaders and Marine Warranty Surveyor shall agree key risk milestones and date(s) for a joint review of the project scope and development. 3.3 At the request of the Marine Warranty Surveyor, Underwriters will make available: · The PSOW, otherwise the GSOW to be used; · relevant applicable policy terms and conditions including, in particular, any warranty provisions or conditions precedent; · identity and contact details (including telephone, e – mail, fax and out of hours numbers) of the nominated Contract leader(s) to receive communications from the Marine Warranty Surveyor. Page 37 of 166 GENERIC SCOPE OF WORK (GSOW) Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval GENERAL ACTIVITIES Metocean criteria, including limiting seastates, for all marine operations. X Weather forecasting procedures X Weight reports and weight contingency factors X Procedures for use of installation vessels /equipment inc. ROVs, ROV tooling, pile hammers, etc. X Tow routes/passage plans / fuelling plans and safe havens X Loadout Manual(s)including ballast plan, quay strength, vessel strength and intact and damaged stability. X Transportation Manual(s) including bollard pull requirements, vessel strength and intact and damaged stability. X Installation Manual(s) including installation vessel thruster reliability and operational procedures, station keeping/mooring arrangements X HUC and Project handover X Sufficiency of data acquisition & testing for soil/rock mechanics and geotechnical parameters at proposed locations for foundations of all installations. X Adequacy of structures to withstand loads during loadout, tow and installation operations X Design codes and recommended practices X Project QA/QC procedures X Management of Change procedures X Project Communications and Interfaces X Installation vessels suitability surveys X X Tugs / barges suitability surveys X X Emergency contingencies X Page 38 of 166 Project Phase Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval FIXED PLATFORMS a) Fabrication and Loadout Weather forecasting procedures X Barge and cargo stability X Ballasting system and procedures X Barge anchored whilst loaded and mooring during loadout / loaded (incl. Fendering) X Motive power systems (winches, trailers, etc) X Structural strength of skidding system or trailers X Link beam/bridge design X Rigging and lift point design X Capability and certification of cranes X Grillage structural checks X Water depth, tidal limitations X Certification of all loadout equipment X Emergency contingency plans X Ballast system trials X Loadout operation X X b) Transportation Procedure for departure (incl draft, tidal, environmental limits) X Motion Response analysis X Grillage and Seafastening design, including Fatigue design considerations (incl NDT documentation) X X X Firefighting, Life saving and emergency equipment for manned tows X X Emergency anchors and mooring including, mounting and release system. X Internal seafastenings / voyage protection X X X Cargo towage / Transportation X Attend Sailaway Issue C of A for Sailaway Page 39 of 166 Project Phase Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval c) Installation Site/seabed survey and water depth X Jacket launch system and equipment X X X Jacket Launch operation X X X Jacket upending X X Template docking X X Jacket on-bottom stability X Jacket buoyancy tank removal X Static and dynamic hook load calculations (single and dual crane lifts) including lifting through water considerations. The independent lifting calculations performed shall include environmental limitations and be in accordance with the approved crane(s) curves. All lifting factors shall be approved by MWS X Lifting equipment design and certification X Jacket Installation (inc. Hydrostatic Collapse Check) X X X Integrated deck / MSF / Module Lift / Floatover X X X Lift points X Bumpers and guiding systems X As-built dimensions of jacket/module interfaces Piling calculations, analysis and Installation Manuals X X (extent of attendance during piling to be agreed) Installation vessel position monitoring/control X Crane suitability - Crane(s) to be inspected prior to lifting operations taking place. This inspection shall include but not be limited to; Crane Certification and Vessel Class; operating history, maintenance and repair records for Crane and Marine systems ; An external visual examination of the Crane(s) and Vessel. X X Floating Cranes DP & Ballast systems trials X X X Tug configuration X Emergency contingencies X Launch preparations including seafastening removal and barge ballasting X X X Page 40 of 166 Project Phase Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval FLOATING STRUCTURES a) Fabrication and Sailaway Vessel condition X Mooring adequacy in yard (to withstand natural hazard exposures e.g. typhoons) X X (Attend to confirm installed mooring) X Cargo stowage and securing X X X Structural strength/fatigue X Towing equipment X X Dry transport vessel suitability X X Vessel Sailaway Attend Sailaway Issue C of A for Sailaway b) Transportation Certification and documentation X Transportation route and weather conditions X Bunkering X Tug or propulsion systems X Stability, ballasting and watertight integrity X Vessel Motions X Seakeeping/heading control X Navigation lights and shapes X Emergency contingencies and equipment (incl. safety equipment) X X Communications and navigational equipment X X Manning X c) Installation Installation – anchors and mooring system X X X Station keeping – Mooring/DP/Tethers X Hook up with infrastructure X X X Lifting equipment design and certification X Module Lifts at offshore site X X X Page 41 of 166 Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval RIGID PIPELINES a) Fabrication and Load-out Pipe joint/reel storage and handling X X X Pipe loading and uploading X X Pipe barge sailaway X X b) Transportation Seafastenings X X X c) Installation Start-up and Termination X X X Installation aids – DMA, A & R head X Assess pipelay equipment and machinery for adequacy. Witness tensioner calibration. X X X Pipelay Vessels DP Trials X X X Pipelay (including lay, expansion, stability and freespan analysis) X X (Underwriters will stipulate if full attendance is required) X Pipeline Installation Analysis (To be reassessed if configuration changes i.e. stinger changes) X Laydown (including preservation procedures for long laydowns and met ocean criteria for commencement of temporary laydown) X X (If laydown period anticipated to exceed 1 month) X Buckle avoidance and detection strategy inc. pipeline tension, load cell calibration, and D/t limitations. X Field joint coating X Crossings X X X Trenching and backfilling X X X Slope stabilisation, mattress protection, rock dumping X Tie-in X Shore approach/pull-in design including dredging and backfilling. X Horizontal Drilling at shore approach X Cleaning and Gauging X X Pressure testing procedure X X X Contingencies including – Abandonment and recovery and Dry/Wet buckle X Page 42 of 166 Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval SUBSEA EQUIPMENT, UMBILICALS, FLOW-LINES and RISERS a) Fabrication and Load-out Manufacturers reeling/spooling X X X Load-out X X X b) Transportation Transportation including sea-fastening X X X c) Installation Installation lines (Including Static and dynamic analyses for all flexible umbilical, flow-lines and risers) X X X Ancillary items such as buoyancy modules, VIV strakes and clamps. X On-bottom stability, crossing, slope stability, free-spans X Suction piles (foundations/anchors) X X X Installation equipment (lifting and lowering), docking and positioning analyses) X X X Pipe spool, jumper installation X X (For Deepwater > 500m) X (For Deepwater > 500m) Manifold/ tree and other hardware installation X X X Temporary installation aids, rigging etc. X Riser/umbilical / power cable pull-in. X X X Riser installation at platform / FPSO X X X Hook-up, commissioning and project handover. Including hydrotests. X Contingency procedures for recovery of damaged subsea components X QA/QC non-conformance reports X Page 43 of 166 Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval VESSEL ACTIVITY DURING CONSTRUCTION PERIOD a) All Project Vessels (Inc. Semi-Sub Rigs and Flotels) Anchoring if within 500m of Project Facilities (Platforms, Templates / Manifolds / Pipelines)) X X X Vessels operating on DP within 500m of Existing Project Facilities, including DP system adequacy, redundancy and condition X X (Attend DP Trials) X b) Jack-Up Rigs Sufficiency of Soil Analysis for Jack-Up Rig punchthrough assessment. Independent punchthrough risk assessment and mitigation measures. X Risk Reduction measures (well shut-in, blowdown, pipeline depressurisation etc.) for Jack-up move onto / off location. X Rig Move - Jack-Up / Jack Down Operations X X X Key X Denotes activity to be performed DMA Dead man anchor A&R Abandon and recovery VIV Vortex Induced Vibration HUC Hook-up and commissioning NDT Non Destructive Testing DP Dynamic Positioning JR 2010/010 23 July.2010 A Joint Committee of the IUA and LMA Page 44 of 166 Appendix E Marine Insurance Act 1906 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Marine Insurance Act 1906 1906 CHAPTER 41 6 Edw 7 An Act to codify the Law relating to Marine Insurance. [21st December 1906] Annotations: Modifications etc. (not altering text) C1 This Act is not necessarily in the form in which it has effect in Northern Ireland C2 Act extended by S.I. 1972/971, art. 4, Sch. 15 MARINE INSURANCE 1 Marine insurance defined. A contract of marine insurance is a contract whereby the insurer undertakes to indemnify the assured, in manner and to the extent thereby agreed, against marine losses, that is to say, the losses incident to marine adventure. 2 Mixed sea and land risks. (1) A contract of marine insurance may, by its express terms, or by usage of trade, be extended so as to protect the assured against losses on inland waters or on any land risk which may be incidental to any sea voyage. (2) Where a ship in course of building, or the launch of a ship, or any adventure analogous to a marine adventure, is covered by a policy in the form of a marine policy, the provisions of this Act, in so far as applicable, shall apply thereto; but, except as by this section provided, nothing in this Act shall alter or affect any rule of law applicable to any contract of insurance other than a contract of marine insurance as by this Act defined. 3 Marine adventure and maritime perils defined. (1) Subject to the provisions of this Act, every lawful marine adventure may be the subject of a contract of marine insurance. Page 45 of 166 2 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) In particular there is a marine adventure where— (a) Any ship goods or other moveables are exposed to maritime perils. Such property is in this Act referred to as “insurable property”; (b) The earning or acquisition of any freight, passage money, commission, profit, or other pecuniary benefit, or the security for any advances, loan, or disbursements, is endangered by the exposure of insurable property to maritime perils; (c) Any liability to a third party may be incurred by the owner of, or other person interested in or responsible for, insurable property, by reason of maritime perils. “Maritime perils” means the perils consequent on, or incidental to, the navigation of the sea, that is to say, perils of the seas, fire, war perils, pirates, rovers, thieves, captures, seisures, restraints, and detainments of princes and peoples, jettisons, barratry, and any other perils, either of the like kind or which may be designated by the policy. INSURABLE INTEREST 4 Avoidance of wagering or gaming contracts. (1) Every contract of marine insurance by way of gaming or wagering is void. (2) A contract of marine insurance is deemed to be a gaming or wagering contract— (a) Where the assured has not an insurable interest as defined by this Act, and the contract is entered into with no expectation of acquiring such an interest; or (b) Where the policy is made “interest or no interest,” or “without further proof of interest than the policy itself,” or “without benefit of salvage to the insurer,” or subject to any other like term: Provided that, where there is no possibility of salvage, a policy may be effected without benefit of salvage to the insurer. 5 Insurable interest defined. (1) Subject to the provisions of this Act, every person has an insurable interest who is interested in a marine adventure. (2) In particular a person is interested in a marine adventure where he stands in any legal or equitable relation to the adventure or to any insurable property at risk therein, in consequence of which he may benefit by the safety or due arrival of insurable property, or may be prejudiced by its loss, or by damage thereto, or by the detention thereof, or may incur liability in respect thereof. 6 When interest must attach. (1) The assured must be interested in the subject-matter insured at the time of the loss though he need not be interested when the insurance is effected: Provided that where the subject-matter is insured “lost or not lost,” the assured may recover although he may not have acquired his interest until after the loss, unless at the time of effecting the contract of insurance the assured was aware of the loss, and the insurer was not. Page 46 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 3 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) Where the assured has no interest at the time of the loss, he cannot acquire interest by any act or election after he is aware of the loss. 7 Defeasible or contingent interest. (1) A defeasible interest is insurable, as also is a contingent interest. (2) In particular, where the buyer of goods has insured them, he has an insurable interest, notwithstanding that he might, at his election, have rejected the goods, or have treated them as at the seller’s risk, by reason of the latter’s delay in making delivery or otherwise. 8 Partial interest. A partial interest of any nature is insurable. 9 Re-insurance. (1) The insurer under a contract of marine insurance has an insurable interest in his risk, and may re-insure in respect of it. (2) Unless the policy otherwise provides, the original assured has no right or interest in respect of such re-insurance. 10 Bottomry. The lender of money on bottomry or respondentia has an insurable interest in respect of the loan. 11 Master’s and seamen’s wages. The master or any member of the crew of a ship has an insurable interest in respect of his wages. 12 Advance freight. In the case of advance freight, the person advancing the freight has an insurable interest, in so far as such freight is not repayable in case of loss. 13 Charges of insurance. The assured has an insurable interest in the charges of any insurance which he may effect. 14 Quantum of interest. (1) Where the subject-matter insured is mortgaged, the mortgagor has an insurable interest in the full value thereof, and the mortgagee has an insurable interest in respect of any sum due or to become due under the mortgage. Page 47 of 166 4 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) A mortgagee, consignee, or other person having an interest in the subject-matter insured may insure on behalf and for the benefit of other persons interested as well as for his own benefit. (3) The owner of insurable property has an insurable interest in respect of the full value thereof, notwithstanding that some third person may have agreed, or be liable, to indemnify him in case of loss. 15 Assignment of interest. Where the assured assigns or otherwise parts with his interest in the subject-matter insured, he does not thereby transfer to the assignee his rights under the contract of insurance, unless there be an express or implied agreement with the assignee to that effect. But the provisions of this section do not affect a transmission of interest by operation of law. INSURABLE VALUE 16 Measure of insurable value. Subject to any express provision or valuation in the policy, the insurable value of the subject-matter insured must be ascertained as follows:— (1) In insurance on ship, the insurable value is the value, at the commencement of the risk, of the ship, including her outfit, provisions and stores for the officers and crew, money advanced for seamen’s wages, and other disbursements (if any) incurred to make the ship fit for the voyage or adventure contemplated by the policy, plus the charges of insurance upon the whole:The insurable value, in the case of a steamship, includes also the machinery, boilers, and coals and engine stores if owned by the assured, and, in the case of a ship engaged in a special trade, the ordinary fittings requisite for that trade: (2) In insurance on freight, whether paid in advance or otherwise, the insurable value is the gross amount of the freight at the risk of the assured, plus the charges of insurance: (3) In insurance on goods or merchandise, the insurable value is the prime cost of the property insured, plus the expenses of and incidental to shipping and the charges of insurance upon the whole: (4) In insurance on any other subject-matter, the insurable value is the amount at the risk of the assured when the policy attaches, plus the charges of insurance. DISCLOSURE AND REPRESENTATIONS 17 Insurance is uberrimæ fidei. A contract of marine insurance is a contract based upon the utmost good faith, and, if the utmost good faith be not observed by either party, the contract may be avoided by the other party. Page 48 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 5 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 18 Disclosure by assured. (1) Subject to the provisions of this section, the assured must disclose to the insurer, before the contract is concluded, every material circumstance which is known to the assured, and the assured is deemed to know every circumstance which, in the ordinary course of business, ought to be known by him. If the assured fails to make such disclosure, the insurer may avoid the contract. (2) Every circumstance is material which would influence the judgment of a prudent insurer in fixing the premium, or determining whether he will take the risk. (3) In the absence of inquiry the following circumstances need not be disclosed, namely: — (a) Any circumstance which diminishes the risk; (b) Any circumstance which is known or presumed to be known to the insurer. The insurer is presumed to know matters of common notoriety or knowledge, and matters which an insurer in the ordinary course of his business, as such, ought to know; (c) Any circumstance as to which information is waived by the insurer; (d) Any circumstance which it is superfluous to disclose by reason of any express or implied warranty. (4) Whether any particular circumstance, which is not disclosed, be material or not is, in each case, a question of fact. (5) The term “circumstance” includes any communication made to, or information received by, the assured. 19 Disclosure by agent effecting insurance. Subject to the provisions of the preceding section as to circumstances which need not be disclosed, where an insurance is effected for the assured by an agent, the agent must disclose to the insurer— (a) Every material circumstance which is known to himself, and an agent to insure is deemed to know every circumstance which in the ordinary course of business ought to be known by, or to have been communicated to, him; and (b) Every material circumstance which the assured is bound to disclose, unless it come to his knowledge too late to communicate it to the agent. 20 Representations pending negotiation of contract. (1) Every material representation made by the assured or his agent to the insurer during the negotiations for the contract, and before the contract is concluded, must be true. If it be untrue the insurer may avoid the contract. (2) A representation is material which would influence the judgment of a prudent insurer in fixing the premium, or determining whether he will take the risk. (3) A representation may be either a representation as to a matter of fact, or as to a matter of expectation or belief. (4) A representation as to a matter of fact is true, if it be substantially correct, that is to say, if the difference between what is represented and what is actually correct would not be considered material by a prudent insurer. Page 49 of 166 6 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (5) A representation as to a matter of expectation or belief is true if it be made in good faith. (6) A representation may be withdrawn or corrected before the contract is concluded. (7) Whether a particular representation be material or not is, in each case, a question of fact. 21 When contract is deemed to be concluded. A contract of marine insurance is deemed to be concluded when the proposal of the assured is accepted by the insurer, whether the policy be then issued or not; and, for the purpose of showing when the proposal was accepted, reference may be made to the slip or covering note or other customary memorandum of the contract . . . F1 Annotations: Amendments (Textual) F1 Words repealed as to instruments made or executed after 1.8.1959 by Finance Act 1959 (c. 58), Sch. 8 Pt. II THE POLICY 22 Contract must be embodied in policy. Subject to the provisions of any statute, a contract of marine insurance is inadmissible in evidence unless it is embodied in a marine policy in accordance with this Act. The policy may be executed and issued either at the time when the contract is concluded, or afterwards. Annotations: Modifications etc. (not altering text) C3 S. 22 excluded by Marine and Aviation Insurance (War Risks) Act 1952 (c. 57), s. 7(1) and Finance Act 1959 (c. 58), s. 30(6)(7) 23 What policy must specify. A marine policy must specify— (1) The name of the assured, or of some person who effects the insurance on his behalf: (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F2 Annotations: Amendments (Textual) F2 S. 23(2)–(5) repealed as to instruments made or executed after 1.8.1959 by Finance Act 1959 (c. 58), Sch. 8 Pt. II Page 50 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 7 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 24 Signature of insurer. (1) A marine policy must be signed by or on behalf of the insurer, provided that in the case of a corporation the corporate seal may be sufficient, but nothing in this section shall be construed as requiring the subscription of a corporation to be under seal. (2) Where a policy is subscribed by or on behalf of two or more insurers, each subscription, unless the contrary be expressed, constitutes a distinct contract with the assured. 25 Voyage and time policies. (1) Where the contract is to insure the subject-matter “at and from,” or from one place to another or others, the policy is called a “voyage policy,” and where the contract is to insure the subject-matter for a definite period of time the policy is called a “time policy.” A contract for both voyage and time may be included in the same policy. (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F3 Annotations: Amendments (Textual) F3 S. 25(2) repealed as to instruments made or executed after 1.8.1959 by Finance Act 1959 (c. 58), Sch. 8 Pt. II 26 Designation of subject-matter. (1) The subject-matter insured must be designated in a marine policy with reasonable certainty. (2) The nature and extent of the interest of the assured in the subject-matter insured need not be specified in the policy. (3) Where the policy designates the subject-matter insured in general terms, it shall be construed to apply to the interest intended by the assured to be covered. (4) In the application of this section regard shall be had to any usage regulating the designation of the subject-matter insured. 27 Valued policy. (1) A policy may be either valued or unvalued. (2) A valued policy is a policy which specifies the agreed value of the subject-matter insured. (3) Subject to the provisions of this Act, and in the absence of fraud, the value fixed by the policy is, as between the insurer and assured, conclusive of the insurable value of the subject intended to be insured, whether the loss be total or partial. (4) Unless the policy otherwise provides, the value fixed by the policy is not conclusive for the purpose of determining whether there has been a constructive total loss. Page 51 of 166 8 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 28 Unvalued policy. An unvalued policy is a policy which does not specify the value of the subject-matter insured, but, subject to the limit of the sum insured, leaves the insurable value to be subsequently ascertained, in the manner herein-before specified. 29 Floating policy by ship or ships. (1) A floating policy is a policy which describes the insurance in general terms, and leaves the name of the ship or ships and other particulars to be defined by subsequent declaration. (2) The subsequent declaration or declarations may be made by indorsement on the policy, or in other customary manner. (3) Unless the policy otherwise provides, the declarations must be made in the order of dispatch or shipment. They must, in the case of goods, comprise all consignments within the terms of the policy, and the value of the goods or other property must be honestly stated, but an omission or erroneous declaration may be rectified even after loss or arrival, provided the omission or declaration was made in good faith. (4) Unless the policy otherwise provides, where a declaration of value is not made until after notice of loss or arrival, the policy must be treated as an unvalued policy as regards the subject-matter of that declaration. 30 Construction of terms in policy. (1) A policy may be in the form in the First Schedule to this Act. (2) Subject to the provisions of this Act, and unless the context of the policy otherwise requires, the terms and expressions mentioned in the First Schedule to this Act shall be construed as having the scope and meaning in that schedule assigned to them. 31 Premium to be arranged. (1) Where an insurance is effected at a premium to be arranged, and no arrangement is made, a reasonable premium is payable. (2) Where an insurance is effected on the terms that an additional premium is to be arranged in a given event, and that event happens but no arrangement is made, then a reasonable additional premium is payable. DOUBLE INSURANCE 32 Double insurance. (1) Where two or more policies are effected by or on behalf of the assured on the same adventure and interest or any part thereof, and the sums insured exceed the indemnity allowed by this Act, the assured is said to be over-insured by double insurance. (2) Where the assured is over-insured by double insurance— (a) The assured, unless the policy otherwise provides, may claim payment from the insurers in such order as he may think fit, provided that he is not entitled to receive any sum in excess of the indemnity allowed by this Act; Page 52 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 9 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (b) Where the policy under which the assured claims is a valued policy, the assured must give credit as against the valuation for any sum received by him under any other policy without regard to the actual value of the subject-matter insured; (c) Where the policy under which the assured claims is an unvalued policy he must give credit, as against the full insurable value, for any sum received by him under any other policy: (d) Where the assured receives any sum in excess of the indemnity allowed by this Act, he is deemed to hold such sum in trust for the insurers, according to their right of contribution among themselves. WARRANTIES, &C. 33 Nature of warranty. (1) A warranty, in the following sections relating to warranties, means a promissory warranty, that is to say, a warranty by which the assured undertakes that some particular thing shall or shall not be done, or that some condition shall be fulfilled, or whereby he affirms or negatives the existence of a particular state of facts. (2) A warranty may be express or implied. (3) A warranty, as above defined, is a condition which must be exactly complied with, whether it be material to the risk or not. If it be not so complied with, then, subject to any express provision in the policy, the insurer is discharged from liability as from the date of the breach of warranty, but without prejudice to any liability incurred by him before that date. 34 When breach of warranty excused. (1) Non-compliance with a warranty is excused when, by reason of a change of circumstances, the warranty ceases to be applicable to the circumstances of the contract, or when compliance with the warranty is rendered unlawful by any subsequent law. (2) Where a warranty is broken, the assured cannot avail himself of the defence that the breach has been remedied, and the warranty complied with, before loss. (3) A breach of warranty may be waived by the insurer. 35 Express warranties. (1) An express warranty may be in any form of words from which the intention to warrant is to be inferred. (2) An express warranty must be included in, or written upon, the policy, or must be contained in some document incorporated by reference into the policy. (3) An express warranty does not exclude an implied warranty, unless it be inconsistent therewith. Page 53 of 166 10 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 36 Warranty of neutrality. (1) Where insurable property, whether ship or goods, is expressly warranted neutral, there is an implied condition that the property shall have a neutral character at the commencement of the risk, and that, so far as the assured can control the matter, its neutral character shall be preserved during the risk. (2) Where a ship is expressly warranted “neutral” there is also an implied condition that, so far as the assured can control the matter, she shall be properly documented, that is to say, that she shall carry the necessary papers to establish her neutrality, and that she shall not falsify or suppress her papers, or use simulated papers. If any loss occurs through breach of this condition, the insurer may avoid the contract. 37 No implied warranty of nationality. There is no implied warranty as to the nationality of a ship, or that her nationality shall not be changed during the risk. 38 Warranty of good safety. Where the subject-matter insured is warranted “well” or “in good safety” on a particular day, it is sufficient if it be safe at any time during that day. 39 Warranty of seaworthiness of ship. (1) In a voyage policy there is an implied warranty that at the commencement of the voyage the ship shall be seaworthy for the purpose of the particular adventure insured. (2) Where the policy attaches while the ship is in port, there is also an implied warranty that she shall, at the commencement of the risk, be reasonably fit to encounter the ordinary perils of the port. (3) Where the policy relates to a voyage which is performed in different stages, during which the ship requires different kinds of or further preparation or equipment, there is an implied warranty that at the commencement of each stage the ship is seaworthy in respect of such preparation or equipment for the purposes of that stage. (4) A ship is deemed to be seaworthy when she is reasonably fit in all respects to encounter the ordinary perils of the seas of the adventure insured. (5) In a time policy there is no implied warranty that the ship shall be seaworthy at any stage of the adventure, but where, with the privity of the assured, the ship is sent to sea in an unseaworthy state, the insurer is not liable for any loss attributable to unseaworthiness. 40 No implied warranty that goods are seaworthy. (1) In a policy on goods or other moveables there is no implied warranty that the goods or moveables are seaworthy. (2) In a voyage policy on goods or other moveables there is an implied warranty that at the commencement of the voyage the ship is not only seaworthy as a ship, but also that she is reasonably fit to carry the goods or other moveables to the destination contemplated by the policy. Page 54 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 11 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 41 Warranty of legality. There is an implied warranty that the adventure insured is a lawful one, and that, so far as the assured can control the matter, the adventure shall be carried out in a lawful manner. THE VOYAGE 42 Implied condition as to commencement of risk. (1) Where the subject-matter is insured by a voyage policy “at and from” or “from” a particular place, it is not necessary that the ship should be at that place when the contract is concluded, but there is an implied condition that the adventure shall be commenced within a reasonable time, and that if the adventure be not so commenced the insurer may avoid the contract. (2) The implied condition may be negatived by showing that the delay was caused by circumstances known to the insurer before the contract was concluded, or by showing that he waived the condition. 43 Alteration of port of departure. Where the place of departure is specified by the policy, and the ship instead of sailing from that place sails from any other place, the risk does not attach. 44 Sailing for different destination. Where the destination is specified in the policy, and the ship, instead of sailing for that destination, sails for any other destination, the risk does not attach. 45 Change of voyage. (1) Where, after the commencement of the risk, the destination of the ship is voluntarily changed from the destination contemplated by the policy, there is said to be a change of voyage. (2) Unless the policy otherwise provides, where there is a change of voyage, the insurer is discharged from liability as from the time of change, that is to say, as from the time when the determination to change it is manifested; and it is immaterial that the ship may not in fact have left the course of voyage contemplated by the policy when the loss occurs. 46 Deviation. (1) Where a ship, without lawful excuse, deviates from the voyage contemplated by the policy, the insurer is discharged from liability as from the time of deviation, and it is immaterial that the ship may have regained her route before any loss occurs. (2) There is a deviation from the voyage contemplated by the policy— (a) Where the course of the voyage is specifically designated by the policy, and that course is departed from; or (b) Where the course of the voyage is not specifically designated by the policy, but the usual and customary course is departed from. Page 55 of 166 12 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (3) The intention to deviate is immaterial; there must be a deviation in fact to discharge the insurer from his liability under the contract. 47 Several ports of discharge. (1) Where several ports of discharge are specified by the policy, the ship may proceed to all or any of them, but, in the absence of any usage or sufficient cause to the contrary, she must proceed to them, or such of them as she goes to, in the order designated by the policy. If she does not there is a deviation. (2) Where the policy is to “ports of discharge,” within a given area, which are not named, the ship must, in the absence of any usage or sufficient cause to the contrary, proceed to them, or such of them as she goes to, in their geographical order. If she does not there is a deviation. 48 Delay in voyage. In the case of a voyage policy, the adventure insured must be prosecuted throughout its course with reasonable dispatch, and, if without lawful excuse it is not so prosecuted, the insurer is discharged from liability as from the time when the delay became unreasonable. 49 Excuses for deviation or delay. (1) Deviation or delay in prosecuting the voyage contemplated by the policy is excused— (a) Where authorised by any special term in the policy; or (b) Where caused by circumstances beyond the control of the master and his employer; or (c) Where reasonably necessary in order to comply with an express or implied warranty; or (d) Where reasonably necessary for the safety of the ship or subject-matter insured; or (e) For the purpose of saving human life, or aiding a ship in distress where human life may be in danger; or (f) Where reasonably necessary for the purpose of obtaining medical or surgical aid for any person on board the ship; or (g) Where caused by the barratrous conduct of the master or crew, if barratry be one of the perils insured against. (2) When the cause excusing the deviation or delay ceases to operate, the ship must resume her course, and prosecute her voyage, with reasonable dispatch. ASSIGNMENT OF POLICY 50 When and how policy is assignable. (1) A marine policy is assignable unless it contains terms expressly prohibiting assignment. It may be assigned either before or after loss. (2) Where a marine policy has been assigned so as to pass the beneficial interest in such policy, the assignee of the policy is entitled to sue thereon in his own name; and the Page 56 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 13 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) defendant is entitled to make any defence arising out of the contract which he would have been entitled to make if the action had been brought in the name of the person by or on behalf of whom the policy was effected. (3) A marine policy may be assigned by indorsement thereon or in other customary manner. 51 Assured who has no interest cannot assign. Where the assured has parted with or lost his interest in the subject-matter insured, and has not, before or at the time of so doing, expressly or impliedly agreed to assign the policy, any subsequent assignment of the policy is inoperative: Provided that nothing in this section affects the assignment of a policy after loss. THE PREMIUM 52 When premium payable. Unless otherwise agreed, the duty of the assured or his agent to pay the premium, and the duty of the insurer to issue the policy to the assured or his agent, are concurrent conditions, and the insurer is not bound to issue the policy until payment or tender of the premium. 53 Policy effected through broker. (1) Unless otherwise agreed, where a marine policy is effected on behalf of the assured by a broker, the broker is directly responsible to the insurer for the premium, and the insurer is directly responsible to the assured for the amount which may be payable in respect of losses, or in respect of returnable premium. (2) Unless otherwise agreed, the broker has, as against the assured, a lien upon the policy for the amount of the premium and his charges in respect of effecting the policy; and, where he has dealt with the person who employs him as a principal, he has also a lien on the policy in respect of any balance on any insurance account which may be due to him from such person, unless when the debt was incurred he had reason to believe that such person was only an agent. 54 Effect of receipt on policy. Where a marine policy effected on behalf of the assured by a broker acknowledges the receipt of the premium, such acknowledgement is, in the absence of fraud, conclusive as between the insurer and the assured, but not as between the insurer and broker. LOSS AND ABANDONMENT 55 Included and excluded losses. (1) Subject to the provisions of this Act, and unless the policy otherwise provides, the insurer is liable for any loss proximately caused by a peril insured against, but, subject as aforesaid, he is not liable for any loss which is not proximately caused by a peril insured against. (2) In particular— Page 57 of 166 14 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (a) The insurer is not liable for any loss attributable to the wilful misconduct of the assured, but, unless the policy otherwise provides, he is liable for any loss proximately caused by a peril insured against, even though the loss would not have happened but for the misconduct or negligence of the master or crew; (b) Unless the policy otherwise provides, the insurer on ship or goods is not liable for any loss proximately caused by delay, although the delay be caused by a peril insured against; (c) Unless the policy otherwise provides, the insurer is not liable for ordinary wear and tear, ordinary leakage and breakage, inherent vice or nature of the subject-matter insured, or for any loss proximately caused by rats or vermin, or for any injury to machinery not proximately caused by maritime perils. 56 Partial and total loss. (1) A loss may be either total or partial. Any loss other than a total loss, as hereinafter defined, is a partial loss. (2) A total loss may be either an actual total loss, or a constructive total loss. (3) Unless a different intention appears from the terms of the policy, an insurance against total loss includes a constructive, as well as an actual, total loss. (4) Where the assured brings an action for a total loss and the evidence proves only a partial loss, he may, unless the policy otherwise provides, recover for a partial loss. (5) Where goods reach their destination in specie, but by reason of obliteration of marks, or otherwise, they are incapable of identification, the loss, if any, is partial, and not total. 57 Actual total loss. (1) Where the subject-matter insured is destroyed, or so damaged as to cease to be a thing of the kind insured, or where the assured is irretrievably deprived thereof, there is an actual total loss. (2) In the case of an actual total loss no notice of abandonment need be given. 58 Missing ship. Where the ship concerned in the adventure is missing, and after the lapse of a reasonable time no news of her has been received, an actual total loss may be presumed. 59 Effect of transhipment, &c. Where, by a peril insured against, the voyage is interrupted at an intermediate port or place, under such circumstances as, apart from any special stipulation in the contract of affreightment, to justify the master in landing and reshipping the goods or other moveables, or in transhipping them, and sending them on to their destination, the liability of the insurer continues, notwithstanding the landing or transhipment. Page 58 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 15 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 60 Constructive total loss defined. (1) Subject to any express provision in the policy, there is a constructive total loss where the subject-matter insured is reasonably abandoned on account of its actual total loss appearing to be unavoidable, or because it could not be preserved from actual total loss without an expenditure which would exceed its value when the expenditure had been incurred. (2) In particular, there is a constructive total loss— (i) Where the assured is deprived of the possession of his ship or goods by a peril insured against, and (a) it is unlikely that he can recover the ship or goods, as the case may be, or (b) the cost of recovering the ship or goods, as the case may be, would exceed their value when recovered; or (ii) In the case of damage to a ship, where she is so damaged by a peril insured against that the cost of repairing the damage would exceed the value of the ship when repaired. In estimating the cost of repairs, no deduction is to be made in respect of general average contributions to those repairs payable by other interests, but account is to be taken of the expense of future salvage operations and of any future general average contributions to which the ship would be liable if repaired; or (iii) In the case of damage to goods, where the cost of repairing the damage and forwarding the goods to their destination would exceed their value on arrival. 61 Effect of constructive total loss. Where there is a constructive total loss the assured may either treat the loss as a partial loss, or abandon the subject-matter insured to the insurer and treat the loss as if it were an actual total loss. 62 Notice of abandonment. (1) Subject to the provisions of this section, where the assured elects to abandon the subject-matter insured to the insurer, he must give notice of abandonment. If he fails to do so the loss can only be treated as a partial loss. (2) Notice of abandonment may be given in writing, or by word of mouth, or partly in writing and partly by word of mouth, and may be given in any terms which indicate the intention of the assured to abandon his insured interest in the subject-matter insured unconditionally to the insurer. (3) Notice of abandonment must be given with reasonable diligence after the receipt of reliable information of the loss, but where the information is of a doubtful character the assured is entitled to a reasonable time to make inquiry. (4) Where notice of abandonment is properly given, the rights of the assured are not prejudiced by the fact that the insurer refuses to accept the abandonment. (5) The acceptance of an abandonment may be either express or implied from the conduct of the insurer. The mere silence of the insurer after notice is not an acceptance. (6) Where notice of abandonment is accepted the abandonment is irrevocable. The acceptance of the notice conclusively admits liability for the loss and the sufficiency of the notice. Page 59 of 166 16 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (7) Notice of abandonment is unnecessary where, at the time when the assured receives information of the loss, there would be no possibility of benefit to the insurer if notice were given to him. (8) Notice of abandonment may be waived by the insurer. (9) Where an insurer has re-insured his risk, no notice of abandonment need be given by him. 63 Effect of abandonment. (1) Where there is a valid abandonment the insurer is entitled to take over the interest of the assured in whatever may remain of the subject-matter insured, and all proprietary rights incidental thereto. (2) Upon the abandonment of a ship, the insurer thereof is entitled to any freight in course of being earned, and which is earned by her subsequent to the casualty causing the loss, less the expenses of earning it incurred after the casualty; and, where the ship is carrying the owner’s goods, the insurer is entitled to a reasonable remuneration for the carriage of them subsequent to the casualty causing the loss. PARTIAL LOSSES (INCLUDING SALVAGE AND GENERAL AVERAGE AND PARTICULAR CHARGES) 64 Particular average loss. (1) A particular average loss is a partial loss of the subject-matter insured, caused by a peril insured against, and which is not a general average loss. (2) Expenses incurred by or on behalf of the assured for the safety or preservation of the subject-matter insured, other than general average and salvage charges, are called particular charges. Particular charges are not included in particular average. 65 Salvage charges. (1) Subject to any express provision in the policy, salvage charges incurred in preventing a loss by perils insured against may be recovered as a loss by those perils. (2) “Salvage charges” means the charges recoverable under maritime law by a salvor independently of contract. They do not include the expenses of services in the nature of salvage rendered by the assured or his agents, or any person employed for hire by them, for the purpose of averting a peril insured against. Such expenses, where properly incurred, may be recovered as particular charges or as a general average loss, according to the circumstances under which they were incurred. 66 General average loss. (1) A general average loss is a loss caused by or directly consequential on a general average act. It includes a general average expenditure as well as a general average sacrifice. Page 60 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 17 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) There is a general average act where any extraordinary sacrifice or expenditure is voluntarily and reasonably made or incurred in time of peril for the purpose of preserving the property imperilled in the common adventure. (3) Where there is a general average loss, the party on whom it falls is entitled, subject to the conditions imposed by maritime law, to a rateable contribution from the other parties interested, and such contribution is called a general average contribution. (4) Subject to any express provision in the policy, where the assured has incurred a general average expenditure, he may recover from the insurer in respect of the proportion of the loss which falls upon him; and, in the case of a general average sacrifice, he may recover from the insurer in respect of the whole loss without having enforced his right of contribution from the other parties liable to contribute. (5) Subject to any express provision in the policy, where the assured has paid, or is liable to pay, a general average contribution in respect of the subject insured, he may recover therefor from the insurer. (6) In the absence of express stipulation, the insurer is not liable for any general average loss or contribution where the loss was not incurred for the purpose of avoiding, or in connexion with the avoidance of, a peril insured against. (7) Where ship, freight, and cargo, or any two of those interests, are owned by the same assured, the liability of the insurer in respect of general average losses or contributions is to be determined as if those subjects were owned by different persons. MEASURE OF INDEMNITY 67 Extent of liability of insurer for loss. (1) The sum which the assured can recover in respect of a loss on a policy by which he is insured, in the case of an unvalued policy to the full extent of the insurable value, or, in the case of a valued policy to the full extent of the value fixed by the policy is called the measure of indemnity. (2) Where there is a loss recoverable under the policy, the insurer, or each insurer if there be more than one, is liable for such proportion of the measure of indemnity as the amount of his subscription bears to the value fixed by the policy in the case of a valued policy, or to the insurable value in the case of an unvalued policy. 68 Total loss. Subject to the provisions of this Act and to any express provision in the policy, where there is a total loss of the subject-matter insured,— (1) If the policy be a valued policy, the measure of indemnity is the sum fixed by the policy: (2) If the policy be an unvalued policy, the measure of indemnity is the insurable value of the subject-matter insured. Page 61 of 166 18 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 69 Partial loss of ship. Where a ship is damaged, but is not totally lost, the measure of indemnity, subject to any express provision in the policy, is as follows:— (1) Where the ship has been repaired, the assured is entitled to the reasonable cost of the repairs, less the customary deductions, but not exceeding the sum insured in respect of any one casualty: (2) Where the ship has been only partially repaired, the assured is entitled to the reasonable cost of such repairs, computed as above, and also to be indemnified for the reasonable depreciation, if any, arising from the unrepaired damage, provided that the aggregate amount shall not exceed the cost of repairing the whole damage, computed as above: (3) Where the ship has not been repaired, and has not been sold in her damaged state during the risk, the assured is entitled to be indemnified for the reasonable depreciation arising from the unrepaired damage, but not exceeding the reasonable cost of repairing such damage, computed as above. 70 Partial loss of freight. Subject to any express provision in the policy, where there is a partial loss of freight, the measure of indemnity is such proportion of the sum fixed by the policy in the case of a valued policy, or of the insurable value in the case of an unvalued policy, as the proportion of freight lost by the assured bears to the whole freight at the risk of the assured under the policy. 71 Partial loss of goods, merchandise, &c. Where there is a partial loss of goods, merchandise, or other moveables, the measure of indemnity, subject to any express provision in the policy, is as follows:— (1) Where part of the goods, merchandise or other moveables insured by a valued policy is totally lost, the measure of indemnity is such proportion of the sum fixed by the policy as the insurable value of the part lost bears to the insurable value of the whole, ascertained as in the case of an unvalued policy: (2) Where part of the goods, merchandise, or other moveables insured by an unvalued policy is totally lost, the measure of indemnity is the insurable value of the part lost, ascertained as in case of total loss: (3) Where the whole or any part of the goods or merchandise insured has been delivered damaged at its destination, the measure of indemnity is such proportion of the sum fixed by the policy in the case of a valued policy, or of the insurable value in the case of an unvalued policy, as the difference between the gross sound and damaged values at the place of arrival bears to the gross sound value: (4) “Gross value” means the wholesale price, or, if there be no such price, the estimated value, with, in either case, freight, landing charges, and duty paid beforehand; provided that, in the case of goods or merchandise customarily sold in bond, the bonded price is deemed to be the gross value. “Gross proceeds” means the actual price obtained at a sale where all charges on sale are paid by the sellers. Page 62 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 19 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 72 Apportionment of valuation. (1) Where different species of property are insured under a single valuation, the valuation must be apportioned over the different species in proportion to their respective insurable values, as in the case of an unvalued policy. The insured value of any part of a species is such proportion of the total insured value of the same as the insurable value of the part bears to the insurable value of the whole, ascertained in both cases as provided by this Act. (2) Where a valuation has to be apportioned, and particulars of the prime cost of each separate species, quality, or description of goods cannot be ascertained, the division of the valuation may be made over the net arrived sound values of the different species, qualities, or descriptions of goods. 73 General average contributions and salvage charges. (1) Subject to any express provision in the policy, where the assured has paid, or is liable for, any general average contribution, the measure of indemnity is the full amount of such contribution, if the subject-matter liable to contribution is insured for its full contributory value; but, if such subject-matter be not insured for its full contributory value, or if only part of it be insured, the indemnity payable by the insurer must be reduced in proportion to the under insurance, and where there has been a particular average loss which constitutes a deduction from the contributory value, and for which the insurer is liable, that amount must be deducted from the insured value in order to ascertain what the insurer is liable to contribute. (2) Where the insurer is liable for salvage charges the extent of his liability must be determined on the like principle. 74 Liabilities to third parties. Where the assured has effected an insurance in express terms against any liability to a third party, the measure of indemnity, subject to any express provision in the policy, is the amount paid or payable by him to such third party in respect of such liability. 75 General provisions as to measure of indemnity. (1) Where there has been a loss in respect of any subject-matter not expressly provided for in the foregoing provisions of this Act, the measure of indemnity shall be ascertained, as nearly as may be, in accordance with those provisions, in so far as applicable to the particular case. (2) Nothing in the provisions of this Act relating to the measure of indemnity shall affect the rules relating to double insurance, or prohibit the insurer from disproving interest wholly or in part, or from showing that at the time of the loss the whole or any part of the subject-matter insured was not at risk under the policy. 76 Particular average warranties. (1) Where the subject-matter insured is warranted free from particular average, the assured cannot recover for a loss of part, other than a loss incurred by a general average sacrifice, unless the contract contained in the policy be apportionable; but, if the Page 63 of 166 20 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) contract be apportionable, the assured may recover for a total loss of any apportionable part. (2) Where the subject-matter insured is warranted free from particular average, either wholly or under a certain percentage, the insurer is nevertheless liable for salvage charges, and for particular charges and other expenses properly incurred pursuant to the provisions of the suing and labouring clause in order to avert a loss insured against. (3) Unless the policy otherwise provides, where the subject-matter insured is warranted free from particular average under a specified percentage, a general average loss cannot be added to a particular average loss to make up the specified percentage. (4) For the purpose of ascertaining whether the specified percentage has been reached, regard shall be had only to the actual loss suffered by the subject-matter insured. Particular charges and the expenses of and incidental to ascertaining and proving the loss must be excluded. 77 Successive losses. (1) Unless the policy otherwise provides, and subject to the provisions of this Act, the insurer is liable for successive losses, even though the total amount of such losses may exceed the sum insured. (2) Where, under the same policy, a partial loss, which has not been repaired or otherwise made good, is followed by a total loss, the assured can only recover in respect of the total loss: Provided that nothing in this section shall affect the liability of the insurer under the suing and labouring clause. 78 Suing and labouring clause. (1) Where the policy contains a suing and labouring clause, the engagement thereby entered into is deemed to be supplementary to the contract of insurance, and the assured may recover from the insurer any expenses properly incurred pursuant to the clause, notwithstanding that the insurer may have paid for a total loss, or that the subject-matter may have been warranted free from particular average, either wholly or under a certain percentage. (2) General average losses and contributions and salvage charges, as defined by this Act, are not recoverable under the suing and labouring clause. (3) Expenses incurred for the purpose of averting or diminishing any loss not covered by the policy are not recoverable under the suing and labouring clause. (4) It is the duty of the assured and his agents, in all cases, to take such measures as may be reasonable for the purpose of averting or minimising a loss. RIGHTS OF INSURER ON PAYMENT 79 Right of subrogation. (1) Where the insurer pays for a total loss, either of the whole, or in the case of goods of any apportionable part, of the subject-matter insured, he thereupon becomes entitled to take over the interest of the assured in whatever may remain of the subject-matter Page 64 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 21 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) so paid for, and he is thereby subrogated to all the rights and remedies of the assured in and in respect of that subject-matter as from the time of the casualty causing the loss. (2) Subject to the foregoing provisions, where the insurer pays for a partial loss, he acquires no title to the subject-matter insured, or such part of it as may remain, but he is thereupon subrogated to all rights and remedies of the assured in and in respect of the subject-matter insured as from the time of the casualty causing the loss, in so far as the assured has been indemnified, according to this Act, by such payment for the loss. 80 Right of contribution. (1) Where the assured is over-insured by double insurance, each insurer is bound, as between himself and the other insurers, to contribute rateably to the loss in proportion to the amount for which he is liable under his contract. (2) If any insurer pays more than his proportion of the loss, he is entitled to maintain an action for contribution against the other insurers, and is entitled to the like remedies as a surety who has paid more than his proportion of the debt. 81 Effect of under insurance. Where the assured is insured for an amount less than the insurable value or, in the case of a valued policy, for an amount less than the policy valuation, he is deemed to be his own insurer in respect of the uninsured balance. RETURN OF PREMIUM 82 Enforcement of return. Where the premium or a proportionate part thereof is, by this Act, declared to be returnable,— (a) If already paid, it may be recovered by the assured from the insurer; and (b) If unpaid, it may be retained by the assured or his agent. 83 Return by agreement. Where the policy contains a stipulation for the return of the premium, or a proportionate part thereof, on the happening of a certain event, and that event happens, the premium, or, as the case may be, the proportionate part thereof, is thereupon returnable to the assured. 84 Return for failure of consideration. (1) Where the consideration for the payment of the premium totally fails, and there has been no fraud or illegality on the part of the assured or his agents, the premium is thereupon returnable to the assured. (2) Where the consideration for the payment of the premium is apportionable and there is a total failure of any apportionable part of the consideration, a proportionate part of the premium is, under the like conditions, thereupon returnable to the assured. (3) In particular— Page 65 of 166 22 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (a) Where the policy is void, or is avoided by the insurer as from the commencement of the risk, the premium is returnable, provided that there has been no fraud or illegality on the part of the assured; but if the risk is not apportionable, and has once attached, the premium is not returnable: (b) Where the subject-matter insured, or part thereof, has never been imperilled, the premium, or, as the case may be, a proportionate part thereof, is returnable: Provided that where the subject-matter has been insured “lost or not lost” and has arrived in safety at the time when the contract is concluded, the premium is not returnable unless, at such time, the insurer knew of the safe arrival. (c) Where the assured has no insurable interest throughout the currency of the risk, the premium is returnable, provided that this rule does not apply to a policy effected by way of gaming or wagering; (d) Where the assured has a defeasible interest which is terminated during the currency of the risk, the premium is not returnable; (e) Where the assured has over-insured under an unvalued policy, a proportionate part of the premium is returnable; (f) Subject to the foregoing provisions, where the assured has over-insured by double insurance, a proportionate part of the several premiums is returnable: Provided that, if the policies are effected at different times, and any earlier policy has at any time borne the entire risk, or if a claim has been paid on the policy in respect of the full sum insured thereby, no premium is returnable in respect of that policy, and when the double insurance is effected knowingly by the assured no premium is returnable. MUTUAL INSURANCE 85 Modification of Act in case of mutual insurance. (1) Where two or more persons mutually agree to insure each other against marine losses there is said to be a mutual insurance. (2) The provisions of this Act relating to the premium do not apply to mutual insurance, but a guarantee, or such other arrangement as may be agreed upon, may be substituted for the premium. (3) The provisions of this Act, in so far as they may be modified by the agreement of the parties, may in the case of mutual insurance be modified by the terms of the policies issued by the association, or by the rules and regulations of the association. (4) Subject to the exceptions mentioned in this section, the provisions of this Act apply to a mutual insurance. SUPPLEMENTAL 86 Ratification by assured. Where a contract of marine insurance is in good faith effected by one person on behalf of another, the person on whose behalf it is effected may ratify the contract even after he is aware of a loss. Page 66 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 23 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 87 Implied obligations varied by agreement or usage. (1) Where any right, duty, or liability would arise under a contract of marine insurance by implication of law, it may be negatived or varied by express agreement, or by usage, if the usage be such as to bind both parties to the contract. (2) The provisions of this section extend to any right, duty, or liability declared by this Act which may be lawfully modified by agreement. 88 Reasonable time, &c. a question of fact. Where by this Act any reference is made to reasonable time, reasonable premium, or reasonable diligence, the question what is reasonable is a question of fact. 89 Slip as evidence. Where there is a duly stamped policy, reference may be made, as heretofore, to the slip or covering note, in any legal proceeding. 90 Interpretation of terms. In this Act, unless the context or subject-matter otherwise requires,— “Action” includes counter-claim and set off: “Freight” includes the profit derivable by a shipowner from the employment of his ship to carry his own goods or moveables, as well as freight payable by a third party, but does not include passage money: “Moveables” means any moveable tangible property, other than the ship, and includes money, valuable securities, and other documents: “Policy” means a marine policy. 91 Savings. (1) Nothing in this Act, or in any repeal effected thereby, shall affect— (a) The provisions of the M1Stamp Act 1891, or any enactment for the time being in force relating to the revenue; (b) The provisions of the M2Companies Act 1862, or any enactment amending or substituted for the same; (c) The provisions of any statute not expressly repealed by this Act. (2) The rules of the common law including the law merchant, save in so far as they are inconsistent with the express provisions of this Act, shall continue to apply to contracts of marine insurance. Annotations: Marginal Citations M1 1891 c. 39. M2 1862 c. 89. 92, 93. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F4 Page 67 of 166 24 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Annotations: Amendments (Textual) F4 Ss. 92, 93, Sch. 2 repealed by Statute Law Revision Act 1927 (c. 42) 94 Short title. This Act may be cited as the Marine Insurance Act 1906. Page 68 of 166 Marine Insurance Act 1906 (c. 41) FIRST SCHEDULE – Form of Policy Document Generated: 2012-05-29 25 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) S C H E D U L E S FIRST SCHEDULE Section 30. FORM OF POLICY Lloyd’s S.G. policy Be it known that as well in own name as for and in the name and names of all and every other person or persons to whom the same doth, may, or shall appertain, in part or in all doth make assurance and cause and them, and every of them, to be insured lost or not lost, at and from Upon any kind of goods and merchandises, and also upon the body, tackle, apparel, ordnance, munition, artillery, boat, and other furniture, of and in the good ship or vessel called the whereof is master under God, for this present voyage, or whosoever else shall go for master in the said ship, or by whatsoever other name or names the said ship, or the master thereof, is or shall be named or called; beginning the adventure upon the said goods and merchandises from the loading thereof aboard the said ship. upon the said ship, &c. and so shall continue and endure, during her abode there, upon the said ship, &c. And further, until the said ship, with all her ordnance, tackle, apparel, &c., and goods and merchandises whatsoever shall be arrived at upon the said ship, &c., until she hath moored at anchor twenty-four hours in good safety; and upon the goods and merchandises, until the same be there discharged and safely landed. And it shall be lawful for the said ship, &c., in this voyage, to proceed and sail to and touch and stay at any ports or places whatsoever without prejudice to this insurance. The said ship, &c., goods and merchandises, &c., for so much as concerns the assured by agreement between the assured and assurers in this policy, are and shall be valued at Touching the adventures and perils which we the assurers are contented to bear and do take upon us in this voyage: they are of the seas, men of war, fire, enemies, pirates, rovers, thieves, jettisons, letters of mart and countermart, surprisals, takings at sea, arrests, restraints, and detainments of all kings, princes, and people, of what nation, condition, or quality soever, barratry of the master and mariners, and of all other perils, losses, and misfortunes, that have or shall come to the hurt, detriment, or damage of the said goods and merchandises, and ship, &c., or any part thereof. And in case of any loss or misfortune it shall be lawful to the assured, their factors, servants and assigns, to sue, labour, and travel for, in and about the defence, safeguards, and recovery of the said goods and merchandises, and ship, &c., or any part thereof, without prejudice to this insurance; to the charges whereof we, the assurers, will contribute each one according to the rate and quantity of his sum herein assuredAnd it is especially declared and agreed that no acts of the insurer or insured in recovering, saving, or preserving the property insured shall be considered as a waiver, or acceptance of abandonment. And it is agreed by us, the insurers, that this writing or policy of assurance shall be of as much force and effect as the surest writing or policy of assurance heretofore made in Lombard Street, or in the Royal Exchange, or elsewhere in London. And so we, the assurers, are contented, and do hereby promise and bind ourselves, each one for his own part, our heirs, executors, and goods to the assured, their executors, Page 69 of 166 26 Marine Insurance Act 1906 (c. 41) FIRST SCHEDULE – Form of Policy Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) administrators, and assigns, for the true performance of the premises, confessing ourselves paid the consideration due unto us for this assurance by the assured, at and after the rate of In Witness whereof we, the assurers, have subscribed our names and sums assured in London. N.B.—Corn, fish, salt, fruit, flour, and seed are warranted free from average, unless general, or the ship be stranded—sugar, tobacco, hemp, flax, hides and skins are warranted free from average, under five pounds per cent., and all other goods, also the ship and freight, are warranted free from average, under three pounds per cent. unless general, or the ship be stranded. RULES FOR CONSTRUCTION OF POLICY The following are the rules referred to by this Act for the construction of a policy in the above or other like form, where the context does not otherwise require:— Lost or not lost. 1 Where the subject-matter is insured “lost or not lost,” and the loss has occurred before the contract is concluded, the risk attaches unless, at such time the assured was aware of the loss, and the insurer was not. From. 2 Where the subject-matter is insured “from” a particular place, the risk does not attach until the ship starts on the voyage insured. At and from. 3 (a) Where a ship is insured “at and from” a particular place, and she is at that place in good safety when the contract is concluded, the risk attaches immediately. (b) If she be not at that place when the contract is concluded, the risk attaches as soon as she arrives there in good safety, and, unless the policy otherwise provides, it is immaterial that she is covered by another policy for a specified time after arrival. (c) Where chartered freight is insured “at and from” a particular place, and the ship is at that place in good safety when the contract is concluded the risk attaches immediately. If she be not there when the contract is concluded, the risk attaches as soon as she arrives there in good safety. (d) Where freight, other than chartered freight, is payable without special conditions and is insured “at and from” a particular place, the risk attaches pro rata as the goods or merchandise are shipped; provided that if there be cargo in readiness which belongs to the shipowner, or which some other person has contracted with him to ship, the risk attaches as soon as the ship is ready to receive such cargo. From the loading thereof. 4 Where goods or other moveables are insured “from the loading thereof,” the risk does not attach until such goods or moveables are actually on board, and the insurer is not liable for them while in transit from the shore to the ship. Page 70 of 166 Marine Insurance Act 1906 (c. 41) FIRST SCHEDULE – Form of Policy Document Generated: 2012-05-29 27 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Safely landed. 5 Where the risk on goods or other moveables continues until they are “safely landed,” they must be landed in the customary manner and within a reasonable time after arrival at the port of discharge, and if they are not so landed the risk ceases. Touch and stay. 6 In the absence of any further licence or usage, the liberty to touch and stay “at any port or place whatsoever” does not authorise the ship to depart from the course of her voyage from the port of departure to the port of destination. Perils of the seas. 7 The term “perils of the seas” refers only to fortuitous accidents or casualties of the seas. It does not include the ordinary action of the winds and waves. Pirates. 8 The term “pirates” includes passengers who mutiny and rioters who attack the ship from the shore. Annotations: Modifications etc. (not altering text) C4 Sch. 1 rules 8, 10 amended by Public Order Act 1986 (c. 64, SIF 39:2), s. 10(2) Thieves. 9 The term “thieves” does not cover clandestine theft or a theft committed by any one of the ship’s company, whether crew or passengers. Restraint of princes. 10 The term “arrests, &c., of kings, princes, and people” refers to political or executive acts, and does not include a loss caused by riot or by ordinary judicial process. Annotations: Modifications etc. (not altering text) C5 Sch. 1 rules 8, 10 amended by Public Order Act 1986 (c. 64, SIF 39:2), s. 10(2) Barratry. 11 The term “barratry” includes every wrongful act wilfully committed by the master or crew to the prejudice of the owner, or, as the case may be, the charterer. All other perils. 12 The term “all other perils” includes only perils similar in kind to the perils specifically mentioned in the policy. Page 71 of 166 28 Marine Insurance Act 1906 (c. 41) SECOND SCHEDULE – Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Average unless general. 13 The term “average unless general” means a partial loss of the subject-matter insured other than a general average loss, and does not include “particular charges.” Stranded. 14 Where the ship has stranded, the insurer is liable for the excepted losses, although the loss is not attributable to the stranding, provided that when the stranding takes place the risk has attached and, if the policy be on goods, that the damaged goods are on board. Ship. 15 The term “ship” includes the hull, materials and outfit, stores and provisions for the officers and crew, and, in the case of vessels engaged in a special trade, the ordinary fittings requisite for the trade, and also, in the case of a steamship, the machinery, boilers, and coals and engine stores, if owned by the assured. Freight. 16 The term “freight” includes the profit derivable by a shipowner from the employment of his ship to carry his own goods or moveables, as well as freight payable by a third party, but does not include passage money. Goods. 17 The term “goods” means goods in the nature of merchandise, and does not include personal effects or provisions and stores for use on board. In the absence of any usage to the contrary, deck cargo and living animals must be insured specifically, and not under the general denomination of goods. F5 SECOND SCHEDULE Annotations: Amendments (Textual) F5 Ss. 92, 93, Sch. 2 repealed by Statute Law Revision Act 1927 (c. 42) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 72 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. Changes and effects yet to be applied to : – s. 17 modified by 2012 c. 6 s. 2(5)(b) – s. 18(6) added by 2012 c. 6 s. 11(2)(a) – s. 19(1) s. 19 renumbered as s. 19(1) by 2012 c. 6 s. 11(2)(b) – s. 19(2) added by 2012 c. 6 s. 11(2)(b) – s. 20(8) added by 2012 c. 6 s. 11(2)(c) – s. 84 modified by 2012 c. 6 Sch. 1 para. 17 Page 73 of 166 Appendix F IMCA Guidance on The Use of Cable Laid Slings and Grommets PDF can be obtained from: http://www.imca-int.com/documents/core/sel/docs/IMCASEL019.pdf Appendix G IMCA Guidelines for Lifting Operations PDF can be obtained from: http://www.imca-int.com/documents/divisions/marine/docs/IMCAM179.pdf Page 74 of 166 Appendix H BWEA Guidelines for the Selection and Operation of Jack-Ups in the Marine Renewable Energy Industry Guidelines for the Selection and Operation of Jack-ups in the Marine Renewable Energy Industry Industry guidance aimed at jack-up operators, developers and contractors www.bwea.com Page 75 of 166 2 Acknowledgements The BWEA extends grateful acknowledgement to the following people and organisations for their commitment and contribution to this document. Key Consultees Mr. Thomas Broe Mr. Tony Millward Mr. Bill Cooper Mr. Stephan Henrikson Mr. Huw Powell Mr. John Gleadowe Mr. Chris Garratt Mr. Bill Hodges Mr. Gary Hogg Mr. Alan Dixon Ms. Judith Tetlow Mr. John Howard Mr. Ad Van der Pennen Mr. Duncan Wilson Mr. Malcolm Blowers Mr. Mark Hayward Mr. Mike Hoyle Mr. Julian Garnsey Ms. Samantha Henshaw Mr. Jim Sandon Mr. Julian Osbourne Mr. Spencer Chiu Mr. Tjerk Suurenbroek Mr. John Vingoe Mr. Rob Maynard Mr. Christian Seeberg Braun Mr. Joris Wortelboer Mr. Per C. Finsaas Mr. Henning Norholm Just Mr. John Fris Londal Mr. Christopher Andersen PMSS Fugro Seacore Searock E.ON Climate & Renewables Vestas Off shore London Off shore Consultants London Off shore Consultants London Off shore Consultants The Working Group Mr Jeremy Carnell Mr. David Pettigrew Mr. Peter Hodgetts Mr. Ian Johnson Mr Kevin Lennon Mr Chris Mallett Mr John Trickey Mr Mike Frampton A2sea A2sea ABP Marine Environmental Research Dong Energy EMU Fugro Seacore Garrard Hassan Global Maritime Global Maritime The Health & Safety Executive The Health & Safety Executive Howard Marine Jack-up Barge BV MPI MPI Noble Denton Noble Denton RWE NPower Renewables PMSS RES RPS RPS Seafox Contractors Seajacks Searock Siemens Wind Power Smit Statoil Hydro Vestas Off shore Vestas Off shore Windcarrier AS Chair Member Member Member Member Document author / editor Document author / editor Document author / editor Version 1 Page 76 of 166 3 Preface The UK has potentially the largest off shore wind resource in the world, with relatively shallow waters and a strong wind resource extending far into the North Sea. The UK has been estimated to have over 33% of the total European potential off shore wind resource - enough to power the country nearly three times over. The growth in UK off shore wind farm projects has increased substantially in recent years. Many Round 1 (see Crown Estate) developments are operational or nearing completion with a number of Round 2 projects well into the development phase. Bids for Round 3 projects closed in March 2009. The precise scale and timelines for future off shore developments are not fi nalised but what can be expected is a substantial increase in off shore construction and operation and maintenance activities. Jack-up barges, which are the focus of these guidelines, are likely to play a major role. BWEA is committed to raising Health and Safety standards across the wind, wave and tidal electrical generation sector. The justifi cation for these guidelines is twofold: • Safety: jack-ups are often large and complex vessels that can operate in extreme environmental conditions. Failure to ensure the correct selection and operation of these vessels could have serious safety implications including loss of life. • Knowledge: some participants in this growth sector may be less familiar with the key Health and Safety issues, legal standards and industry practices for Jack-up operations. For these reasons BWEA commissioned LOC in 2008 to deliver these guidelines in order to raise the knowledge and awareness of the issues to the industry and to share proven good practice. These guidelines will be reviewed periodically by BWEA to refl ect improvements and technology changes in Jack-up design and operational practice. STATUS These guidelines have been developed in consultation with the industry to refl ect established and proven good practice and sound methodology in the selection and operation of jack-up’s in the off shore wind, wave and tidal industries. The guidelines are not a standard in their own right, but do make reference to the relevant parts of a number of existing and established marine standards in the text. There is no compulsion for the industry to adhere to these guidelines but in the opinion of the authors and BWEA careful cognisance of and adherence to the guidelines together with suffi cient competence in this fi eld of activity will minimise risk of unsafe acts or conditions arising during jack-up operations. It is likely that in the event of a marine jack-up incident that is subject to investigation by UK enforcement agencies this guidance may be referenced as ‘industry good practice’ to which it would be expected that measures equal to or better than those in the guidance are in place. DISCLAIMER The contents of this guide are intended for information and general guidance only, do not constitute advice, are not exhaustive and do not indicate any specifi c course of action. Detailed professional advice should be obtained before taking or refraining from taking action in relation to any of the contents of this guide or the relevance or applicability of the information herein. Page 77 of 166 4 Contents Appendices 1. Introduction 6 2. Legislation and guidelines 7 3. Jack-up management and manning 8 4. Planning of jack-up operations 11 5. Weather restricted and unrestricted operations 14 6. Floating condition: motions and stability 16 7. Grillage, seafastening and cargo design 19 8. Site data required for jack-up site-specifi c assessments 21 9. Jack-up foundation (soils) assessment 24 10. Elevated operations 26 11. Self-propelled and propulsion assisted jack-ups 28 12. Non-propelled jack-ups 29 13. Towing vessels 32 14. Moorings for positioning 35 15. Lifting and load transfer 39 16. Crew transfer 42 17. Marine control for jack-up operations 44 18. Conduct of jack-up operations 45 19. Emergencies and contingencies 50 APPENDIX A: Reference documents 52 APPENDIX B: Defi nitions, terms and abbreviations 54 APPENDIX C: Jack-up certifi cates, manuals publications, logs and records 62 APPENDIX D: Jack-up operating manual (recommended contents) 64 APPENDIX E: Typical spot location report 66 APPENDIX F: Foundation risks: methods for evaluation and prevention 67 APPENDIX G: Flowchart for jack-up site assessment 68 APPENDIX H: Air gap calculation 69 APPENDIX I: Check list for jack-up suitability assessment 71 Chapter Appendix Page Page Page 78 of 166 5 1. Introduction 1.1 Instructions This document has been prepared by London Off shore Consultants Limited for BWEA following various BWEA/HSE discussions and consultations with others involved with the jack-up industry. The report provides guidelines on the safety and integrity of jack-up rigs deployed in the marine renewable energy industry. 1.2 Nature of the guidelines This guidance is intended to be relevant to all organisations contributing to the operation of jack-up vessels in nearshore areas but it is particularly relevant to jack-up owners’ or operators’ technical staff and crews responsible for the operation of jack-up vessels and to project managers in the marine renewable energy industry. These guidelines have been drawn with care to address what are likely to be the main concerns based on the experience of this working group and others. This should not be taken to mean that this document deals comprehensively with all of the concerns which will need to be addressed or even, where a particular matter is addressed, that this document sets out the defi nitive recommendations to be followed for all situations. The guidance is based upon the assumption that the user is familiar with the fundamental aspects of the marine operations of jack-up barges. Those less familiar with these vessels may fi nd it useful in the fi rst instance to acquire a basic understanding of the diff erent types of jack-ups and the risks associated with their various operating modes. This information can be obtained through study of background reference material listed in Appendix A. This document should be treated as providing guidelines for good industry practice to be followed for the selection and operation of jack-ups. The guidelines contained in this document should be reviewed in each particular case by persons responsible to ensure that the particular circumstance is addressed in a way which is adequate and appropriate. Nothing contained in these guidelines shall relieve the owners, operators, managers or masters and crews of the jack-ups of their responsibility for exercising sound judgement based on education, training and experience. These guidelines are not intended to exclude alternative methods, new technology or new equipment, which may provide an equivalent or greater level of operational safety. This guideline is based on and as far as is reasonably practicable is consistent with the guidance contained in existing reference documents listed in Appendix A. 1.3 Area of application This guideline shall be deemed to apply to all jack-ups operating in the inshore and coastal waters adjacent to England, Scotland, Wales and Northern Ireland in the area bounded by Highest Astronomical Tide (HAT) and the seaward limit of the UK territorial waters, and to all areas that are located within UK Renewable Energy Zones (REZ) beyond the UK territorial waters seaward limit 12 miles off shore. 1.4 Terms and defi nitions See glossary containing defi nitions, terms and abbreviations used in this guideline in Appendix B. Defi ned terms used in this guideline have been italicised in the text. Page 79 of 166 6 2. Legislation and guidelines 2.1 Reference is requested to BWEA Guidelines for Health and Safety in the Marine Energy Industry, which provides a basic introduction on the legislative requirements that govern the operations considered in this guideline. Particular reference shall be made to: • The Health and Safety at Work Act 1974 • The Management of Health and Safety at Work Regulations 1999 • The Construction (Design and Management) Regulations 2007 (CDM) • Provision and Use of Work Equipment Regulations 1998 (PUWER) • Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) 2.2 Contractors shall ensure that they fully understand and comply with the CDM regulations when operating jack-ups engaged on projects to which these regulations comply. A guide to these regulations is contained in the Approved Code of Practice (Managing Health and Safety in Construction) (ACOPS). 2.3 The adoption of codes and standards for the design, construction, and operation of jack-ups and attending vessels is governed by marine legislation promulgated by the state in which the vessel is registered (the fl ag state) and by the state which, by international agreement, has been assigned control over the waters in which the jack-up is operating (the port state). 2.4 Jack-up vessels in transit and positioning within UK waters are governed by the Merchant Shipping Act and the Marine and Coastguard Agency (MCA) is the principal government agency responsible for monitoring the implementation of UK marine legislation. In accordance with this legislation, jack-up operators shall arrange to receive Merchant Shipping Notices (MSN), Marine Guidance Notices (MGN) and Marine Information Notices (MIN) issued by the MCA and they shall heed warnings and comply with advice contained therein. 2.5 In addition, jack-ups shall comply with regulations issued by local port or river authorities and harbour masters whenever they are in transit or engaged in elevated operations in waters controlled by such authorities. 2.6 Jack-ups shall be designed, constructed and operated in compliance with the rules, standards, and codes applicable to their fl ag, type, tonnage, size and manning. These rules have been adopted under the terms of the International Conventions on Maritime safety and Marine Pollution and subsequent protocols and amendments as produced by the International Maritime Organisation (IMO). • International Safety Management (ISM) Code 2002 • Safety of Life at Sea (SOLAS 1974) • International Convention on Loadlines 1966 • Preventing Collisions at Sea Regulations COLREGS • Standards of Training, Certifi cation and Watchkeeping for Seafarers (STCW) 1978 • Prevention of Pollution from Ships MARPOL 1973/78 • Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 • Incidents by Hazardous and Noxious Substances, 2000 (HNS Protocol) • Control of Harmful Anti-fouling Systems on Ships (AFS), 2001 The list above includes the conventions and codes likely to apply to jack-up operations in the area considered; however, this list is not exhaustive. The responsibility for obtaining all relevant IMO documents and any latest amendments rests with the jack-up owner or operator. Page 80 of 166 7 2.7 The United Kingdom Health & Safety Executive (HSE) is responsible for enforcing all of the relevant Health and Safety legislation pertaining to work activity in Britain including work activities on jack-ups operating in UK Territorial Waters or within the UK Exclusive Economic Zone (EEZ). Therefore jack-up operators should obtain copies of current HSE Research Reports Information Sheets and Off shore Technology Reports relevant to jack-up operations [Appendix A] and be guided by the advice contained therein. Page 81 of 166 8 3. Jack-up management and manning 3.1 Registry and class 3.1.1 Jack-ups should be offi cially entered on a vessel registry maintained by a recognised maritime nation. 3.1.2 Jack-ups certifi ed to operate only within a specifi c trading area or within a limiting distance from a safe haven shall operate only within the limits prescribed by their fl ag state as stated on the jack-up’s registry certifi cate or certifi cate of seaworthiness and trading area. 3.1.3 Permanently manned jack-ups fi tted with certifi ed accommodation and jack-ups exceeding 24m in length shall be classed and class maintained in accordance with the rules of a recognised classifi cation society. 3.1.4 Unmanned jack-ups not fi tted with certifi ed accommodation and not exceeding 24 metres in length that are not classed shall be certifi ed in accordance with the MCA Small Commercial Vessel and Pilot Boat (SCV) Code as set out in MGN 280, or certifi ed in accordance with equivalent foreign rules promulgated by the fl ag state. 3.1.5 It is recommended that permanently manned jack-ups operating in unrestricted mode are classed by a member of the International Association of Classifi cation Societies (IACS) with jack-up experience and having established rules and procedures for the classifi cation of jack-up hulls, legs and machinery including elevating and holding systems. Such classifi cation societies can usually be identifi ed through the class notation, which should include the term “self elevating” to confi rm that the jack-up has been designed, constructed and maintained to operate in both fl oating and elevated modes. 3.1.6 It is recommended that permanently manned jack-ups fi tted with certifi ed accommodation are certifi ed in compliance with the MODU code. In the absence of a MODU (or MOU) certifi cate, the vessel should, as a minimum requirement, be provided with a class certifi cate or statement of facts verifying the provision of adequate safety equipment for the type of vessel and for the number of personnel on board. 3.1.7 It is a fundamental requirement that the jack-up hull, machinery and equipment shall be maintained in satisfactory condition. An adequate inventory of spare parts should be carried on board. Particular attention should be paid to the provision of replaceable parts for critical jacking system and power system components, where failure of such parts could render the systems inoperative. 3.1.8 It is recommended that site developers obtain an independent suitability survey or general condition survey prior to hiring a jack-up; however, the type and condition of the vessel can provisionally be assessed by review of the specifi cations and the registry and class certifi cates and survey reports [Appendix C]. Particular attention should be paid to the valid dates and any outstanding items or recommendations related to the class approval of design, drawings, manuals, materials, fabrication, modifi cation, maintenance, damage or repair as listed on the document attachments. 3.1.9 Outstanding class items or recommendations should be reviewed by a competent person in order to determine whether any listed defect or defi ciency could create unusual risk or otherwise adversely aff ect the proposed operations. The competent person should recommend, where appropriate, that these be rectifi ed before the jack-up is deployed. Particular attention should be paid to the structural strength and watertight integrity of the jack-up, the operability of the jacking system and the provision of safety equipment. Page 82 of 166 9 3.2 Draft and leg height marks 3.2.1 Draft marks shall be clearly marked on each side of the jack-up hull at each end in accordance with the rules contained in the International Convention on Loadlines 1966. Jack-ups exempted under these rules shall carry the same marks. 3.2.2 Leg height marks shall be clearly marked on each leg at vertical intervals not exceeding one metre. A fi xed point at the deck level or on the jack-house or jack-frame top shall be marked as a reference point against which the leg height marks can be read. The leg height marks and the fi xed reference points should normally be clearly visible from the jacking control position. 3.2.3 Where the confi guration of the jack-up is such that leg height marks and reference points cannot be observed from the jacking control position and where no mechanical or electronic leg height measurement system is fi tted at the control position, then trained crewmembers will usually be required to relay leg height information to the jacking engineer during jacking operations. 3.2.4 Jack-ups shall be fi tted with longitudinal and transverse inclinometers capable of providing accurate readings of tilt to within 0.2 degrees of accuracy or better. These instruments shall be calibrated to ensure accuracy. 3.3 Certifi cation and documentation 3.3.1 Original certifi cates, documents, publications and drawings listed in Appendix C should be carried on board the jack-up. Certifi cates for jack-ups not fi tted with permanent superstructures, enclosed control rooms or accommodation may be kept on board the towing vessel or at the owner’s offi ce and should be made available for inspection prior to vessel deployment. Holding copies of certifi cates and documents on board or ashore is a sensible precaution but presentation of copies should not be accepted as proof of validity. 3.3.2 Every jack-up shall be provided with an operating manual. The contents of the operating manual should contain, as a minimum, the information listed in Appendix D of this guideline. 3.4 Management 3.4.1 Certifi cation or registration of jack-up owners’ or operators’ companies to a standard recognised by the International Standards Organisation is not an absolute requirement; however, in the absence of such accreditation, they should be independently audited to verify that they practice an acceptable standard of management. 3.4.2 Standards of vessel management that are certifi ed under the provisions of the IMO International Safety Management (ISM) code will be deemed satisfactory. In the absence of ISM Certifi cation, it shall be demonstrated that the vessel is managed in accordance with a documented procedure that includes the key requirements of the ISM Code. 3.4.3 The safe management of jack-ups requires a wide range of technical skills: • Structural and off shore engineering • Vessel design and analysis • Vessel machinery operation, maintenance and repair • Navigation, seamanship and off shore operations • Meteorology • Soil investigation and analysis Page 83 of 166 10 Where technical staff holding the relevant qualifi cation and with the appropriate training and experience are not employed by the owners or operator of the jack-up then a competent person must be outsourced as appropriate. 3.4.4 Jack-up owners and operators shall formulate, publish and enforce a drug and alcohol policy. 3.5 Manning 3.5.1 Jack-ups shall be manned in accordance with the Safe Manning Certifi cate if so certifi ed. Jack-ups less than 24m in length shall be manned in accordance with the MCA Small Commercial Vessel and Pilot Boat (SCV) code as set out in MGN 280 or equivalent foreign rules promulgated by the fl ag state. 3.5.2 Whether certifi ed or otherwise, jack-up masters and any licensed person authorised by the master to operate the radio equipment shall demonstrate profi ciency in the English language. All emergency and external operating communications shall be conducted in the English language. In addition to the master, a suffi cient number of the crew shall be profi cient in English so that orders and instructions can be translated swiftly and eff ectively to non-English speaking crewmembers or project personnel. Internal instructions may be conducted in the common language of the crew. 3.5.3 In every case, jack-up owners or operators shall man their vessels with suffi cient crew to manage the vessel and the marine operations making proper allowance for rest periods. The following key positions are usually manned on jack-ups more than 24m in length. 1. Vessel or barge master (off shore installation manager) 2. Tow master for transit and positioning (may be covered by (1) above) 3. Jacking engineer (may be covered by (1) above except where (1) is tow master) 4. Engineer, motorman or mechanic 5. Electrician (may be covered by (4) above if competent) 6. Welder (may be covered by (4) above if competent) 7. Crane operator(s) (units fi tted with cranes) 8. Boatswain and seamen (number suffi cient for the size of the jack-up) 9. Deck foreman and riggers (as required for operations) 10. Catering crew (as appropriate for the number of persons on board) 11. Medic (may be an individual or any trained crewmember assigned to this duty) 3.5.4 The medic (or paramedic) should as a minimum hold a First Aid at Sea Certifi cate or Medical First Aid certifi cate and in some cases should hold a Profi ciency in Medical Care Certifi cate (or its predecessor, the Ship Captain’s Medical Certifi cate). For jackups <24m in length reference is requested to refer to the Small Vessel Code MGN 280 annex 3 page 118. The limitations of the basic training related to these certifi cates should be recognised and in some cases a higher qualifi cation will be appropriate. The level of training, profi ciency and qualifi cation required in each case should be determined through a risk assessment carried out considering the: • Number of persons on board • Proximity to the shore • Vessel and site equipment’s capacity for rapid medivac • Access by emergency services (including coastguard helicopter and RNLI) • Access restrictions imposed by the jack-up confi guration, weather or tide Page 84 of 166 11 3.5.5 Masters and crew serving on self-propelled jack-ups shall be in possession of valid Certifi cates of Competence issued under the provisions of the STCW 95 as required by the vessel’s Safe Manning Certifi cate, including GMDSS Operator’s Certifi cates and DP endorsements as appropriate. 3.5.6 It is noted that the Jack-up Owners Association has expressed an intention to develop a competence framework for barge masters; however, there is currently no statutory requirement for certifi cation or training of crews serving on non-propelled jack-ups. Notwithstanding the lack of a statutory requirement, it is recommended that barge masters serving on permanently manned jack-ups should be in possession of a Certifi cate of Competence in a marine grade and, in addition, should have received formal training in jack-up operations. 3.5.7 Whether certifi ed or otherwise, the barge master shall, as a minimum, demonstrate a satisfactory level of competence in the areas listed below. Competence may be demonstrated through Certifi cates of Competence issued under the provisions of STCW 95 or through other certifi cation or accreditation, or in the absence of such documents, through documented work experience and references. • Applicable laws and regulations • Vessel management • Marine operations, equipment and practices • Marine fi refi ghting • Operation of survival craft and sea survival • Pollution prevention • The GMDSS system and operation of radio equipment • First aid • Meteorology for mariners • Management of barge fl oating stability and jack-up elevated loads • Jacking operations and foundation hazards and shall, as a minimum, be in possession of: • GMDSS Radio Operators Certifi cate • Sea Survival Certifi cate • First Aid Certifi cate (or higher qualifi cation) 3.5.8 There is currently no statutory requirement for certifi cation or training of jacking engineers; however, it is recommended that jacking engineers receive formal training in jack-up marine operations including the fundamentals of jack-up soil foundations. Most importantly, the jacking system shall be operated only by, or under the supervision of, persons who have been trained to operate the type of system fi tted to the jack-up on which they serve. 3.5.9 Crane operators shall be in possession of a Crane Operator’s Certifi cate appropriate for the operation of the equipment installed. 3.5.10 Jack-up crew members shall be in possession of: • Valid certifi cates of Basic Off shore Survival Training of the type provided in the course of induction for personnel engaged in the off shore oil & gas industry (For example: UK OPITO Basic Safety Induction and Emergency Training) or similar merchant navy training for seafarers • Valid certifi cates of Medical Examination appropriate to service off shore or in the merchant navy (for example: UKO or (UK) ENG-1 or foreign equivalent) Page 85 of 166 12 4. Planning of jack-up operations 4.1 Suitability of the jack-up 4.1.1 The design of site-specifi c specialist structures and construction planning for the installation of the structures is a separate activity which may form the basis of jack-up selection. This will usually pre-date the selection of the jack-up; however, it should be recognised that construction planning may be infl uenced by the type and capacity of jack-ups likely to be available at the time the plans are to be executed. 4.1.2 The suitability of a jack-up for a particular operation can only be determined if the objectives to be achieved and the operations necessary to achieve the objectives are thoroughly understood. Based on this understanding, the jack-up’s type and operating limits must be assessed in consideration of the conditions likely to be encountered on the intended transit route and at the selected work site in order to determine whether the jack-up is capable of undertaking the required operations safely and effi ciently. 4.1.3 Jack-ups are not designed, constructed or intended for unlimited service at sea. Each stage of the proposed operations must be considered separately because diff erent limiting environmental criteria will apply to each sequential jack-up operating mode. Jack-up operations can typically be divided into the following stages: • Mobilisation • Loadout • Transit (including jacking down and refl oating) • Positioning (including jacking up and preloading) • Elevated operations (including lifting and load transfer operations) 4.1.4 The suitability of a jack-up for transit will depend upon the characteristics of the sea route and the unit’s seaworthiness and sea keeping capability. The suitability of the jack-up for elevated operations at any location is determined by a site-specifi c assessment. This assessment is a study of environmental, bathymetric and seabed soils data relevant to that location, together with a leg footing penetration analysis and a structural assessment of the rig itself to determine whether the unit is capable of: • Avoiding contact with seabed obstructions or debris • Achieving a stable foundation in the seabed soils • Elevating high enough to stand above the predicted extreme wave crests • Withstanding the static and dynamic loads imposed upon it when elevated • Safely extracting the legs from the soil on removal from the location 4.1.5 Preliminary site-assessments based solely on information related to the site water depth and the jack-up’s leg length may serve to exclude some units from consideration for proposed works at an early stage. Similarly, preliminary assessments based solely on nomograms may be useful but these should be treated with some caution because they may use safety factors less than those associated with the recommended practice and they may be based on assumed assessment parameters that are diff erent to those at the site. 4.1.6 It is stressed that the suitability of any jack-up for elevation and for the performance of the necessary operations on site can only be properly judged by means of a site-specifi c assessment carried out in accordance with the recommended practice. 4.1.7 The fundamental suitability of a jack-up should be established prior to planning or executing jack-up operations. Outline guidance on suitability is included as the fi nal APPENDIX I. Page 86 of 166 13 4.2 Requirement for planning 4.2.1 Jack-up transit, positioning and elevated operations should be planned and prepared in accordance with the provisions described in this guideline. The planning should include the provision of a documented procedure (or method statement) for each stage of the operation and an estimated time for the conduct and completion of each stage together with an adequate contingency for delay. • Departure from the present location • Passage between locations • Arrival and positioning at the new location • Elevated operations to be undertaken at the new location 4.2.2 In addition to the documented procedure, a full risk assessment of planned operations should be undertaken, and an emergency response plan and Health and Safety plan should be developed, both of which should be available onboard the vessel. The responsibilities and lines of communication should be clearly stated. 4.2.3 The procedure document should address the: • Objectives to be achieved • Operations necessary to achieve the objectives • Operational procedures to be adopted • Vessels, equipment and services required to conduct the operations • Geophysical, geotechnical, environmental and operating constraints and limits • Organisation and responsibilities of the parties and personnel involved • Communications • Contingency plans 4.2.4 Generic procedures for refl oating, towing or self-propulsion, dynamic positioning, jacking, preloading, and elevated operations as applicable to the routine operation of the jack-up are usually included in the vessel’s operating manual. 4.2.5 Detailed procedures for the safe operation and maintenance of the jacking machinery should be provided in the form of a jacking system manual if not included as part of the operating manual. Similarly, detailed procedures for the operation of vessel equipment such as engines, bilge and ballast systems and mooring systems should be provided in the vessel’s equipment manuals. These manuals need to be referred to, but may be excluded from the procedure document. 4.2.6 The operating manual and procedure documents shall be prepared in the English language. 4.2.7 All aspects of the planning shall be subject to review by a competent person. The planning and the review shall include the aspects detailed below. 4.3 Planning jack-up transit The jack-up’s limits afl oat (including leg strength and securing arrangements) should be considered and the aspects to be documented and reviewed shall include the: • Defi ned environmental criteria and duration of the transit • Stability calculation and watertight integrity of the jack-up • Motion response of the jack-up in the design sea state considered Page 87 of 166 14 • Strength of the cranes, deck equipment and seafastening arrangements • Details of the cargo and stowage plan • Strength of the cargo together with the grillage and seafastening arrangements • Towing arrangement plan, towing equipment and tug specifi cations (towed jack-ups) • Passage plan (all transits) 4.3.1 It should be verifi ed that the arrangements listed above are adequate for the intended transit and suffi cient to withstand the loads and motions for the jack-up’s condition afl oat. 4.3.2 The tugs together with the towing arrangements and towing equipment should be verifi ed as suitable for the proposed transit and in compliance with the requirements set out in this guideline. 4.3.3 It should be verifi ed that the transit route has been planned in accordance with the principles of good seamanship having due regard for narrows, water depths, squat eff ects, tidal heights and currents, vessel traffi c and separation systems and all navigational hazards. The jack-up’s air draft with legs fully raised should be considered in connection with maintaining safe clearances below overhead obstructions such as bridges and cables. It should also be verifi ed that the provision of navigation equipment, charts, tidal data, and nautical publications is adequate to complete the transit safely. 4.3.4 The transit route should be documented and should include designated safe havens en route and/or alternative safe jacking locations. The maximum transit time between safe havens or alternative jacking locations should be considered having due regard for the time required for jacking down, transit, positioning and jacking up to the minimum safe air gap at the next location. 4.3.5 Seabed surface and soil conditions at alternative safe jacking locations shall be investigated and documented as suitable for positioning. The selection of alternative jacking locations with very soft soils or locations where risk of rapid settlement is deemed to exist should be avoided. 4.3.6 The risk of failure of propulsion machinery or towing gear should be considered. Routes passing rocks, shoals and other hazards to navigation should be planned with allowance, where practicable, for time to repair machinery and reconnect the tow and for possible drift during such operations. 4.3.7 Planning jack-up transits shall include arrangements for the provision of marine weather forecasts obtained from a recognised meteorological authority in accordance with the detailed requirements described in section 18.3. 4.3.8 The planning should include contingency plans and emergency procedures as detailed in Section 19. 4.3.9 Planning jack-up transits should include information on the departure location and the proposed arrival location together with the arrangements for positioning the jack-up on location as follows. 4.4 Planning jack-up positioning 4.4.1 The planning and review shall include a site-specifi c assessment in accordance with the recommended practice for the jack-up at the proposed arrival location. Page 88 of 166 15 4.4.2 The procedure document shall include or make reference to the jack-up soils assessment and the site-specifi c assessment. These documents shall be placed on the jack-up and shall be reviewed by the persons responsible for positioning the jack-up in advance of the move. 4.4.3 The planning should also include site-specifi c jacking and preloading procedures (if any) that may have been developed in response to previously identifi ed jack-up foundation hazards and/or recommendations (if any) contained in the site-specifi c assessment or the soils investigation and assessment reports. 4.4.4 In considering the suitability of jack-up rig locations due consideration should be given to site accessibility. The marine aspects of the approach to and positioning at the arrival location such as water depth, tidal range, tidal current velocity, duration of slack water and navigational hazards should be considered. Particular consideration should be given to the proximity of fi xed or fl oating installations and sub-sea pipelines and cables. It needs to be demonstrated in the plan that the site can be reached without incurring unusual marine risk. 4.4.5 The plan shall include details of the method to be employed and the tugs, moorings and survey equipment required to move the jack-up into position afl oat at the required geographical co-ordinates and on the required heading. Page 89 of 166 16 5. Weather restricted and unrestricted operations 5.1 Operations considered 5.1.1 Jack-up operations in the following modes are considered: 1. Afl oat under tow 2. Moored afl oat 3. Partly elevated with the hull partly buoyant in leg-stabilised mode 4. Elevated in the operating mode at a working air gap 5. Elevated in the survival mode at air gap ≥ the minimum recommended safe air gap 5.1.2 Most jack-ups are required to operate in unrestricted mode (5) above, because the nature of their activity requires that they remain on location for many days or weeks and the distance off shore and the complexity of their equipment and moving arrangements means that they cannot be quickly or easily removed to shelter. 5.1.3 Jack-ups that are not designed or constructed to achieve the survival air gap or to withstand the stresses likely to be imposed by the 50 year design storm in the elevated condition may operate safely in weather restricted mode in accordance with the guidelines for weather restricted operations. 5.2 Jack-up - unrestricted operations 5.2.1 Good industry practice for unrestricted operations elevated requires that the jack-up be capable of elevating to the minimum survival air gap and that the unit’s design meets the minimum acceptance criteria for survival elevated as defi ned in the recommended practice. 5.2.2 The site-specifi c assessment (section 10) shall demonstrate that the unit is capable of remaining safely elevated on location in the prescribed 50 year extreme storm condition or the 10 year extremes for the de-manned condition (section 10.2.4) with a limited amount of additional penetration and with all structural stresses remaining within allowable limits. 5.2.3 When operating in unrestricted mode, the hull elevation for survival mode is to be set at or in excess of a minimum elevation to provide for 1.5 m clearance above the 50 year return period wave crest or to just clear the 10,000 year return period wave crest, whichever is greatest. 5.2.4 Seasonal variations in the 50 or 10 year extremes may be considered if the jack-up is to remain on location for a limited period only during specifi ed months. 5.2.5 Storm directionality may be considered if there is suffi cient reliable evidence that the extreme wind, waves and current at the location are directional. In such cases it may be possible to orientate the jack-up on the most advantageous heading in order to achieve the required values for the checks associated with the acceptance criteria. Particular care shall be taken in making assessments where the environmental conditions are highly directional, that is where they may change signifi cantly over only a few degrees. 5.3 Weather restricted operations 5.3.1 Jack-up operations in the fi rst four modes listed in (5.1) above may be undertaken as a weather restricted operation. In this case the jack-up’s design limits for each mode and the limiting weather criteria for each mode must be clearly defi ned in advance. With due regard for the confi dence in the predicted weather conditions, planning must be in place to remove the jack-up to shelter afl oat or to an alternative safe location where the jack-up can be elevated before the onset of any weather that is forecast to exceed the specifi ed limits. Page 90 of 166 17 5.3.2 The conduct of a weather restricted operation requires that detailed site-specifi c marine weather forecasts be obtained from a recognised authority at intervals no greater than 12 hours (section 18.3). 5.3.3 The planned duration of a weather restricted operation should not normally exceed 72 hours. However, the duration may be indefi nitely extended in prolonged periods of benign weather provided that the limits for the restricted mode are never exceeded, and provided also that a future weather window suitable for moving the jack-up to the safe location is clearly and consistently identifi ed by the duty forecaster with a high level of confi dence on each weather forecast. 5.3.4 If a future weather window for safe removal of the jack-up cannot be identifi ed with a high level of confi dence within the next 72 hours and risk of continued severe weather to follow is deemed to exist such that the limits for the restricted mode (as defi ned in paragraph 5.3.1) could be exceeded, then the jack-up should be moved to shelter immediately before the sea state limit for jacking down and moving off location is approached or exceeded. 5.3.5 The conduct of weather restricted operation requires that a procedure document shall be in place containing details of the proposed work schedule with particular reference to the anticipated duration of each operation, the time needed to suspend operations and to reach the nearest safe haven or safe elevated location and to complete positioning. A contingency for delay caused by leg extraction problems, waiting for slack water, breakdown or other delay shall be allowed. In no case shall the total time estimated for suspension of operations, removal to shelter and positioning at the safe location exceed 48 hours including contingency for delay. 5.3.6 A safe jack-up location may be a port or a sheltered bay or estuary where the jack-up can remain afl oat under tow or moored, or a location where the jack-up can be elevated providing: • The strength of the seabed soils is known to be suffi cient to support the jack-up without further settlement after preloading • The jack-up can be elevated to or above the minimum survival air gap • The jack-up is capable of achieving the survival mode with all stresses remaining within allowable limits 5.3.7 As part of an emergency response procedure, where insuffi cient time remains to reach a safe jack-up location before the anticipated onset of adverse weather and where the risk of remaining afl oat is deemed to be greater than the risk of elevating on a location with an unproven jack-up foundation, then consideration should be given to elevating the jack-up on the nearest location with suitable water depth before the onset of adverse weather, whether the strength of the seabed soil is known or otherwise. 5.3.8 The action described in 5.3.7 (above) should only be attempted at the master’s discretion following receipt of advice from the designated person ashore and the Maritime Rescue Coordination Centre (MRCC). In these circumstances, and where practicable, it is recommended that all non-essential personnel should be removed prior to elevation and consideration should be given to temporarily abandoning the jack-up as soon as it has been preloaded and elevated to the minimum survival air gap. 5.3.9 It should be recognised that the operation of a jack-up in weather restricted mode may result in prolonged delays caused by the potential for frequent interruption of the work in order to move the jack-up to shelter to await a suitable weather window (or series of weather windows) of suffi cient length to continue the proposed works. The limiting condition for the movement of most jack-ups is with signifi cant wave heights between 0.5m and 1.5m. The incidence of such benign conditions may be infrequent and of short duration in many areas, particularly in the winter season. 5.3.10 It should also be recognised that the operation of a jack-up in weather restricted mode involves higher risk than operation in unrestricted mode and consequently the planning and execution of a weather restricted operation requires a high level of competence. In consideration of the higher risk, developers or contractors may consider it appropriate to engage Marine Warranty Survey Services for review and approval of the procedures. Page 91 of 166 18 6. Floating condition: motions and stability 6.1 Application 6.1.1 Jack-up dry transport, self-propelled jack-up ocean transit and non-propelled jack-up ocean tow is not considered in this guideline. This guideline applies only to jack-up location moves and fi eld moves. Guidance on ocean towing can be found in Noble Denton 0030/ND Dated 15/04/200 Guidelines for Marine Transportations and IMO Guidelines for Safe Ocean Towing, December 1998 (MSC/Circ.884). 6.2 Design environmental criteria 6.2.1 This guideline assumes that all transits of self-propelled jack-ups when carrying project cargo and all transits of non-propelled jack-ups with or without cargo will be undertaken as a weather restricted operation with the jack-up essentially in fi eld move confi guration. 6.2.2 Specifi c environmental criteria shall be defi ned for a weather restricted operation and these shall be appropriate to the planned route and the duration of the tow. 6.2.3 The duration of the passage under power or under tow should include any additional time for jacking and preloading on site and any standby time that may reasonably be expected as a result of delays. Planned contingencies for diversion at any point en route to reach a place of shelter should be in place. 6.2.4 The design seastate for a jack-up transit conducted as a weather restricted operation shall be based on the signifi cant wave height (Hs). Typically, the maximum wave height will be 1.86Hs. The design wind speed shall be the one-minute average velocity at 10m above sea level. The incident wave shall be considered to be omni-directional. 6.2.5 The operating criteria shall be set lower than the design criteria to allow for potential inaccuracy in wave height forecasts. Typically weather restricted towages should not commence in seastates greater than 50% of the design maximum as the observer will often report the signifi cant wave heights rather than the maximum wave height. 6.3 Motion response criteria 6.3.1 The jack-up, cargo, grillage and seafastenings shall be designed to withstand the motions and forces resulting from the design environmental criteria. Friction shall be ignored. It is recommended that either a motion response analysis is made or that model tests are performed for each case. 6.3.2 The motion response analysis should utilise proven software and techniques. For both motion response analysis and/or model tests, a realistic combination of environmental loads and wave directions and periods, representing bow, stern, quartering and beam sea conditions shall be used. If required, the analysis shall be validated by correlation with model tests for similar units or by performing new model tests. Alternatively, additional analysis may be performed covering more seastates or using diff erent software 6.4 Default motion criteria 6.4.1 Alternatively, and subject to consideration of the length of the voyage, the risks involved and any mitigating factors for reducing the risks, the jack-up, cargo, grillage and seafastenings shall be designed to withstand the motions and forces derived by using Page 92 of 166 19 Type of jack-up Large jack-up Small jack-up Ship shape unit Field move LOA ≥ 76 and B ≥23 LOA < 76 or B < 23 LOA ≥ 76 and B ≥23 All jack-ups } 20 } 25 } 20 } 10 } 12.5 } 15 } 12.5 } 10 } 0.2g } 0.2g } 0.2g } 0.1g Barge dimensions L & B m Roll amplitude degrees Pitch amplitude degrees Heave acceleration m/s2 default motion criteria tabulated below. The standard criteria shown above should be applied in accordance with the following: • The roll and pitch amplitude are single amplitude values assumed to apply for a 10 second full cycle period of motion • The roll and pitch axes should be assumed to pass through the centre of fl oatation. • The phasing considered should be assumed to combine, as separate load cases, the most severe combinations of: roll ± heave; pitch } heave. 6.5 Inland and sheltered water criteria 6.5.1 For inland and sheltered water transportation, whichever of the following has the greatest eff ect shall be taken into account: • Static loads caused by an acceleration of 0.1g applied parallel to the deck in the roll or pitch direction • The most severe inclination in the damage condition, as determined by the damage stability calculations including the additional heel or trim caused by the design wind. 6.6 Intact static stability 6.6.1 Jack-up stability afl oat shall be calculated to demonstrate compliance with the rules published by a recognised classifi cation society or the rules contained in the MODU Code or the rules contained in MCA - MGN 280 as applicable to their type, tonnage, size and classifi cation, or in accordance with the guidelines provided below. 6.6.2 The intact stability, or intact range of stability, is the range between 0 degree heel or trim and the angle at which the righting arm (GZ) becomes negative (see fi gure. 6.1). el Angle Righting Arm (GZ) 0 0 0 0 10 0.3 80 2.4 20 0.65 30 1.2 40 1.7 0 53 50 2 2.05 53 60 1.95 70 1.6 80 1 90 0.45 100 -0.05 105 -0.2 0 1.3 85 1 80 0 80 1 -0 5 0 0.5 1 1.5 2 2.5 0 20 40 60 80 120 Heel Angle Righting Arm (GZ) Figure 6.1 - Illustration of stability terms Page 93 of 166 20 6.6.3 The transverse metacentric height (GM) must be positive, at zero angle of heel. 6.6.4 The range of transverse static stability should normally exceed 40 degrees. Correction to values of GM to allow for free surface eff ects should be included in this computation. 6.6.5 The acceptability of barges with a range of 30 to 40 degrees will be dependent on motion response predictions. 6.6.6 In the event of the range of static stability being greater than 30 degrees and less than 40 degrees, it shall be demonstrated that the maximum predicted roll angle is less than the angle at which the maximum righting lever occurs. 6.6.7 A range of static stability less than 30 degrees will not normally be accepted. 6.7 Intact dynamic stability 6.7.1 The areas under the righting moment curve and the wind heeling moment (or wind moment) curve should be calculated up to an angle of heel which is the least of: • The angle corresponding to the second intercept of the two curves • The angle of down fl ooding 6.7.2 For guidance on how to derive the wind heeling moment curve, reference is made to IMO resolution A.749 (18) Code on Intact Stability for all Types of Ships covered by IMO instruments. 6.7.3 The wind velocity used to compute the wind heeling moment curve should be the one-minute sustained wind for the operation as defi ned in section 6.2. 6.8 Damage static stability 6.8.1 As a minimum, the jack-up should have suffi cient stability and reserve buoyancy to remain afl oat at a waterline below any opening where progressive fl ooding may occur with any one-compartment adjacent to the sea fl ooded. -0.5 0 0.5 1 1.5 2 2.5 3 3.5 0 10 20 30 40Heel A50ngle 60 70 80 90 Moment A B C Wind Moment Righting Moment INTACT STABILITY (A+B) > 1.4(B+C) Figure 6.2 - Intact stability requirement Page 94 of 166 21 6.8.2 Damage to any compartment above the intact waterline that could lead to loss of stability should be considered when assessing damage stability. 6.8.3 The loss of water from a full compartment should be considered if it gives a more severe result than the fl ooding of an empty compartment. 6.9 Damage dynamic stability 6.9.1 The area under the righting moment curve should be not less than the area under the wind heeling moment curve. 6.9.2 The areas under the righting moment curve and the wind heeling moment curve should be calculated from equilibrium up to an angle of heel which is the least of: • The angle corresponding to the second intercept of the two curves • The angle of down fl ooding 6.9.3 The wind velocity that is used to compute the overturning moment curve may be 25m/s. However, if the design wind velocity for the operation, as defi ned in section 6.2 is less than 25m/s, the design velocity should be used instead. 6.9.4 Where it is impracticable to comply with damage stability recommendations, a risk assessment should be carried out, and appropriate mitigating measures taken. Righting Arm (GZ) 8 0 0 10 0.1 80 20 0.65 30 1.2 40 1.7 0 50 2 2.05 60 1.95 70 1.6 8 0 80 1 8 1.3 90 0.45 100 -0.05 105 -0.2 8 1.3 85 1 Heel Angle Moment A B C Wind Moment Righting Moment DAMAGE STABILITY (A+B) > (B+C) Figure 6.3 - Damage stability requirements Page 95 of 166 22 7. Grillage, seafastening and cargo design 7.1 Loads during transportation 7.1.1 The components of load to be considered when analysing the total forces acting on the cargo, the vessel and grillage and seafastenings are those due to: • The static weight of the cargo • The dynamic loads which result from the vessel’s motion in all six degrees of freedom • The static component of weight which acts parallel to the barge deck when the vessel rolls or pitches • Loads caused by heave acceleration including the heave.sin (Θ) terms • Wind load • Loads resulting from immersion of any part of the cargo support frames • Ballast distribution in the barge • Ice where appropriate 7.1.2 Regarding the loads due to motions above, the combination of motions that give the highest loading in any direction shall be considered. In the absence of information to the contrary (such as a motion analysis taking account of phase relationships to compute acceleration vectors), the highest loadings resulting from the following motions shall be combined as two separate load cases: • Roll, heave and sway • Pitch, heave and surge 7.1.3 Loads may normally be calculated using the assumption that all motions approximate to sinusoidal motions. 7.1.4 Structural loadings due to green water impact shall be based on the true relative motion between the structure and wave surface. 7.1.5 Account shall also be taken of any substantial loads in the grillage and seafastenings resulting from the relative defl ections of vessel and cargo, whether due to changes in ballast arrangement or due to environmental eff ects. 7.1.6 When using the default criteria as defi ned in section 6.4 seas from headings other than the bow, stern and beam the horizontal accelerations may be resolved as applicable to the required heading. The resultant acceleration in the desired direction shall be obtained from taking the square root of the sum of the squares of the resolved accelerations. The heave acceleration will remain unchanged. 7.2 Stresses 7.2.1 The grillage and seafastenings shall be designed in accordance with a recognised standard or code of practice. Wherever possible, the design should be carried out to the requirements of one code only. 7.2.2 The seafastening shall be designed such that the static stresses in all members do not exceed the allowable stresses in accordance with AISC manual or other acceptable code. The 1/3 increase in allowable stresses referred to in earlier editions of the AISC manual may be used for stresses in cargo, grillage and seafastening where the steelwork is of high quality. It should not be used for the design of grillage and seafastening connections to the vessel or assessing the underdeck strength except when the condition of all steelwork associated with the load path has been verifi ed as being of high quality with full material certifi cation. Page 96 of 166 23 7.2.3 If the AISC 13TH edition is used the allowables shall be compared against member stresses determined using a load factor on both dead and live loads of no less than: WSD option LRFD option SLS: 1.0 1.60 ULS: 0.75 1.20 7.2.4 Any load case may be treated as a normal serviceability limit state (SLS)/normal operating case. 7.2.5 Infrequent load cases occurring no more frequently than the maximum design wave, which are dominated by extreme environmental forces may generally be treated as an ultimate limit state (ULS)/survival storm case. This only applies to steel of high quality which has been verifi ed by a thorough and appropriate NDT inspection. 7.3 Grillage 7.3.1 The grillage design and layout should take account of any limitations imposed by the load transfer method. 7.3.2 The basis for the design of the grillage shall be the loads derived from the vessel motions as defi ned in section 6.3 or 6.4. 7.3.3 The relative stiff ness of the barge frames and bulkheads shall be taken into account when deriving the load distribution between the grillage and the barge. 7.3.4 The eff ects of super-position of loads shall be accommodated in the design when welds/connections are made between the grillage and barge deck following load out. 7.4 Seafastening 7.4.1 The purpose of the seafastenings is to secure the cargo during the transit and positioning so that neither the cargo nor vessel suff ers loss or damage as a result of the loadings derived from the vessel motions caused by the environment conditions. 7.4.2 Seafastenings should not in any circumstances be removed until the jack-up has completed preloading or predriving and elevating to the operating air gap. Primary seafastenings should be designed to be removed without damage to the cargo. During and following removal of primary seafastenings, adequate residual seafastening should remain to safely restrain the cargo until its removal from the vessel. 7.4.3 The entire load path, including the potential sliding surfaces, should be demonstrated to be capable of withstanding the design loads. 7.4.4 Small items of cargo ≤1000kg should be secured in accordance with good practice using appropriate lashings or securing arrangements that are adequate to ensure they are safely secured and will not be a hazard to any person in the event of bad weather or an emergency. 7.4.5 If the seafastenings are welded to the cargo it is recommended that they be fi tted after the vessel has been ballasted to the transport condition. 7.4.6 Where the same seafastenings are to be used for multiple transits, inspection of welded seafastenings and/or bolted connections is required prior to commencing each transit. Where practicable, locking nuts/devices should be used in preference to ordinary bolts. Page 97 of 166 24 7.5 Vessel strength 7.5.1 The calculated still water bending moment (SWBM) and shear force (SF) shall be checked against the allowable SWBM and SF values approved by the classifi cation society. If they exceed the specifi ed permissible loads then the classifi cation society shall be informed and their acceptance obtained. 7.5.2 The legs, jack houses and hull are to be shown to possess adequate strength to resist the loads imposed during the sea passage afl oat. Leg chocks, wedges and locking devices shall be considered if fi tted. 7.5.3 Local vessel strength calculations shall be required at highly stressed areas of the vessel. These calculations shall take account of any corrosion from the “as-built” scantlings. 7.6 Cargo strength 7.6.1 It shall be demonstrated that the cargo (equipment, tools, modules and wind turbine components etc.) has adequate structural strength to be transported without damage caused by the maximum loadings resulting from the vessel’s motions under the environmental conditions described in section 6.3 or from the standard criteria as given in section 6.4. 7.6.2 Local analysis may also be required to quantify load eff ects in localised highly loaded areas such as grillage supports or seafastening connection points, and to confi rm the adequacy of equipment to withstand these loads without damage. 7.6.3 The cargo structure is to be shown to have adequate strength to resist the loads imposed during the voyage combined with the additional loading caused by any overhang of the cargo over the side of the transport vessel. 7.7 Internal seafastenings 7.7.1 Internal seafastenings shall be provided where necessary. These may be in the form of temporary members to provide structural support during transportation, or the securing of equipment and loose items forming part of the cargo. Protection against wave slam or spray should also be provided as appropriate. Calculations may be required for major items of equipment. 7.8 Fatigue 7.8.1 Whether or not fatigue analyses are performed, all seafastenings shall be designed for good fatigue characteristics. Page 98 of 166 25 8. Site data required for jack-up site-specifi c assessments 8.1 General 8.1.1 Site survey is required for the purpose of providing data with which to defi ne the position, boundary and characteristics of the location for the purpose of determining the suitability of the site for the operation of the jack-up. 8.1.2 Geophysical data alone is insuffi cient to perform a site-specifi c assessment of the soil foundation conditions and this should be complemented by geotechnical information as described in section 8.7, except for jack-ups engaged in soils investigations as provided in section 18.6. 8.1.3 It is recommended that a single uniform survey system (e.g. WGS84) be used for both site investigation and subsequent fi eld development so as to ensure that compatibility and conformity is achieved between the original site investigation and the operations of marine units subsequently involved in the site works. 8.2 Location co-ordinates 8.2.1 The co-ordinates of each jack-up location expressed in terms of degrees, minutes and seconds of latitude and longitude are required. Latitude and longitude co-ordinates should be given to at least two, or preferably three, decimal places of precision and must also include details of the datum and projection used. 8.3 Water depth, tidal range and storm surge 8.3.1 The water depth at each jack-up location, referred to Lowest Astronomical Tide (LAT), is required. Nearshore pre-construction surveys producing results with vertical levels related to Ordnance datum must be converted to LAT before application to jackup marine operations. 8.3.2 The maximum tidal range and the 50 year storm surge shall be computed for the jack-up location and/or for the area of operations considered. The following data shall be provided as a minimum. • 50 Year storm surge (m) • Highest Astronomical Tide (HAT) (m) • Lowest Astronomical Tide (LAT) (m) 8.4 Wind and wave and current data 8.4.1 Meteorological extremes likely to be reached or exceeded once, on average, every 50 years, are required as listed below. The provision of 1 year and 10 year extremes is also recommended. This information, together with the data in the fi rst two bullet points in 8.3.2 above, is required for the site-specifi c assessment. • Wind – one-minute mean (m/s) • Extreme wave height (m) • Extreme wave crest elevation (m) • Associated crest to crest wave period (sec) • Peak period (sec) • Signifi cant wave height (m) • Maximum surface current in downwind direction (m/s) • Current profi le 8.4.2 Particular attention shall be paid to the provision of competent data for inshore sites that may be aff ected by: • Shelter aff orded by proximity of the coastline or shallows Page 99 of 166 26 • Refracted and/or refl ected waves • Breaking waves and surf zones • High velocity tidal currents (>1.5 m/s) in the vicinity of sand banks and narrows • Tidal bores • Wakes from passing vessels, particularly deep displacement ships and fast craft. 8.4.3 Special consideration is required at sites where breaking waves will occur. Calculation of hydrodynamic loads is not straightforward and a degree of judgement is required by the analyst to arrive at correct design values. Guidance on this subject can be found in ISO 19901-1:2005 (E) part one: “Metocean Design and Operating Considerations”. 8.4.4 Comprehensive met-ocean studies carried out in connection with nearshore and off shore wind farms do not usually take account of the specifi c data required for jack-up emplacement. This creates a need for interpolation which can lead to inaccuracy and signifi cant diff erences in the analyses carried out by diff erent contractors for diff erent jack-ups. For this reason it is recommended that such studies be reviewed by a single competent meteorological authority specialising in the provision of meteorological data for jack-up site-assessments and that the data be presented as a jack-up Spot Location Report (SLR) in a simple unequivocal format (Appendix E). 8.5 Bathymetric survey 8.5.1 A bathymetric survey is required for an area of approximately 1km square centred on the proposed location. Line spacing of the survey should be typically not greater than 100m x 200m over the survey area. If any irregularities are detected interlining should be performed with spacing not exceeding 25m x 50m. Swathe bathymetry or other techniques providing an equivalent or greater level of accuracy may be used as an alternative method of producing the survey results. 8.5.2 Rapid changes in bathymetry shall be anticipated in shallow areas that are subject to high velocity tidal currents and/or areas that may have been exposed to severe storm waves. The appropriate period of validity of the survey should be considered in all cases having due regard for the site characteristics and the anticipated rate of change indicated by earlier surveys. The survey report should include comment on the anticipated period of validity plus the magnitude and probability of error resulting from seabed changes. 8.5.3 Navigational charts derived for shipping are not usually suffi ciently accurate for positioning jack-ups; however, up to date corrected charts for the transit route together with the largest available UK Admiralty navigation charts for the site are required to be carried on the jack-ups and attending tugs for reference. Paper charts may not be required on jack-ups that are ECDIS equipped and certifi ed for ECDIS use only. 8.5.4 Notes and cautions listed on Admiralty charts should be referred to. Navigation should not be attempted through or within areas marked as “not surveyed”, or areas carrying the notation “banks and channels subject to frequent change” or similar notation, without reference to recent bathymetric survey information. 8.6 Seabed surface survey 8.6.1 A seabed surface survey is required to identify natural and man-made seabed features, obstructions and debris. The survey should cover the approach to and the immediate area of the intended location (normally a 500m x 500m square for off shore and nearshore sites) and should be carried out using side scan or sector scan sonar, or other high-resolution techniques producing equivalent or better results. Page 100 of 166 27 8.6.2 A magnetometer survey is required to reveal the presence of buried pipelines or cables, lost anchors and chains, military ordnance or other metallic debris lying below the seabed surface. The requirement for a magnetometer survey may be waived in certain areas but the lack of this information should be justifi ed in the site-specifi c assessment. 8.6.3 Site and location plans based on the seabed surface surveys should identify wrecks and important archaeological sites and/ or marine conservation areas that are subject to protection. Sites where seabed or environmental disturbance should be avoided for any reason shall be identifi ed. Specifi c information concerning the type of activity to be avoided and or seasonal limits or other qualifying conditions related to these areas should be provided. 8.6.4 The appropriate period of validity of the seabed surface survey should be considered in all cases having due regard for the site characteristics and any surface or subsea activity carried out on site since the last survey. As a general rule, the period of validity should be six months or less in uncontrolled areas and areas where no continuous system for reporting marine activity and lost objects exists. 8.6.5 The discovery of seabed surface obstructions or debris at any time within or without the site area should be reported to the site Marine Traffi c Controller (MTC) or, in the absence of an MTC, to the UK Hydrographic Offi ce. 8.7 Geotechnical (soils) investigation 8.7.1 Site-specifi c geotechnical information is required. The type and amount of data required will depend upon the particular circumstances such as the type of jack-up, soil conditions and previous experience of the site, or nearby sites, for which the assessment is being performed. 8.7.2 For sites where previous preloading and elevated operations have been performed by jack-ups, it may be suffi cient to identify the location of existing jack-up footprints. In this case the details of the previous jack-up footing design and the preload applied should be available and it should be verifi ed that the foundation bearing pressure applied previously was in excess of the pressure to be applied by the jack-up under consideration. In the absence of such verifi cation soil investigation involving boreholes or CPT is required. 8.7.3 The location and number of boreholes or CPT’s required should account for lateral variability of the soil conditions, regional experience and the geophysical investigation. A borehole may not be required if there is suffi cient relevant historical data and/ or geophysical tie lines to boreholes in close proximity to the proposed jack-up location. 8.7.4 The geotechnical investigation should comprise a minimum of one borehole to a depth equal to 30m or the anticipated penetration plus 1.5 – 2.0 times the footing diameter, whichever is greater. Investigation to lesser depths may be accepted in cases where only small penetrations are anticipated in hard soils; however, in such cases the advance approval of an geotechnical engineer with appropriate experience with jack-up foundation assessments is recommended and the reduced depth of investigation shall be justifi ed in the foundation assessment. 8.7.5 All layers shall be adequately investigated, including any transition zones between strata, such that the geotechnical properties of all layers are known with confi dence and that there are no signifi cant gaps in the site investigation record. Laboratory testing of soil samples may be required. Page 101 of 166 28 8.7.6 Geotechnical investigations carried out in connection with construction activities such as pile driving may be of limited use for jack-up site assessments. Care must be exercised to ensure that the soil investigation is adequate in scope and detail for jackup site-assessment. If in doubt, a geotechnical engineer with appropriate experience with jack-up foundation assessments shall be consulted. 8.7.7 In virgin territory where there is no soil data available, seabed sampling may be carried out from suitable jack-ups prior to installation. In such cases appropriate precautions (section 18.6) must be taken to ensure the safety of the jack-up during the initial period on location and until the soil investigation is complete. 8.7.8 The nature of the seabed surface soil, together with the water depth and the current and wave regimes shall be assessed to determine whether potential for scour may exist. The assessment should consider whether scour has occurred around existing fi xed or temporary structures in the vicinity (if any) and records of previous scour that may have aff ected earlier jackup installations. In the event that the assessment indicates that the integrity of the jack up foundation could be adversely aff ected then seabed soil samples may be required and a scour analysis should be performed (section 9.13). 8.7.9 The soil investigation must produce suffi cient reliable data on which to base a competent analysis that will provide a recommended soil strength design profi le giving lower and upper bound strength estimates. This will be carried forward into the jack-up site-specifi c assessment (section 10). Page 102 of 166 29 9. Jack-up foundation (soils) assessment 9.1 Foundation assessment is required in all cases where the jack-up is to be preloaded and elevated above the sea surface to a working air gap or to the minimum safe survival air gap on location. The scope of the assessment and the amount of data required will depend upon the particular circumstances such as the type of jack-up, the soil conditions and variations in the soil across the site, and upon previous experience of the site, or nearby sites, for which the assessment is being performed. 9.2 The jack-up foundation assessment shall be carried out in accordance with the recommended practice or in accordance with another recognised and appropriate code of practice that provides an equivalent level of safety. The assessment shall have due regard for potential hazards listed in SNAME T&R Bulletin 5-5A. Foundation risks are tabulated in Appendix F. 9.3 For jack-up locations where there is no history of previous jack-up emplacement a complete foundation assessment is required. The assessment shall include or refer to a geotechnical report containing the survey records together with their interpretation by a qualifi ed soils engineer plus a leg penetration assessment for the proposed unit or a unit with similar footing design and load characteristics. 9.4 For jack-up foundation assessment at sites where preloading operations have been performed earlier by the same or another jack-up it may be suffi cient to identify the location of existing jack-up footprints. In this case the details of the previous jack-up footing design and the preload applied should be available and it should be verifi ed that the footing type was similar to the jack-up under consideration and the foundation bearing pressure applied during the previous installation was in excess of the pressure to be applied for the jack-up considered. In the absence of such verifi cation a complete foundation assessment is required. 9.5 The combinations of vertical and horizontal load shall be checked against a foundation bearing capacity envelope. The resistance factor may be taken as 1.0 when the load-penetration curve indicates signifi cant additional capacity for acceptable levels of additional settlement. Minor settlement not exceeding the limits contained in the Operating Manual may be acceptable provided that: • The jack-up can withstand the storm loading plus the eff ects of the inclination • The lateral defl ections will not result in contact with adjacent structures • The jacking system will remain fully operational at the angle of inclination considered 9.6 Consideration shall be given to the operating limits of the jacking system. The capacity of any jacking system to elevate or lower the hull may be signifi cantly reduced or eliminated by leg guide friction (binding) caused by small angles of inclination. Additionally, some hydraulic recycling jacking systems cannot usually be jacked at angles of inclination greater than 1.0 degree because even this small angle can result in inability to extract or engage the fi xed and working pins (or catcher beams). 9.7 Extreme caution should be exercised if the soil profi le reveals a risk of punch-through when it should be demonstrated that there is an adequate safety factor to ensure against punch-through occurring in both extreme (abnormal) storm events and operating conditions. Particular attention must be paid to the appropriate safety factor in cases where the jack-up’s maximum Page 103 of 166 30 preload capacity does not produce signifi cantly greater foundation bearing pressure than that to be applied in the operating or survival modes (See fi gure 9.1). 9.8 Calculation of the safety factor against punch-through should normally be in accordance with the recommended practice; however, alternative methods that may provide an equivalent or greater level of safety exist and therefore consideration should be given as to which method is appropriate in the circumstances. For this reason reference should be made to other sources of advice contained in UK HSE research report 289 - Guidelines for Jack-up Rigs with Particular Reference to Foundation Stability; Noble Denton 0009/ND Rev 4, dated 16 December 2008 - Self-Elevating Platforms - Guidelines for Elevated Operations; and Det Norske Veritas Classifi cation Note No. 30.4. Ultimately, the assessment of punch-through risk requires a high level of expertise and the exercise of sound judgment based on experience. 9.9 Consideration should be given to the limits of maximum and minimum penetration as determined by the jack-up design or Operating Manual. In cases where the limits stated in the manual are related simply to a sample elevated condition and the leg length installed, it can be ignored provided the leg length is suffi cient to meet the survival air gap defi ned in the recommended practice. An analysis should be carried out for any case where the maximum or minimum penetration limit stated in the manual is related to leg or spudcan structural strength or to the jack-up’s capacity for leg extraction. 9.10 Particular consideration shall be given to the requirement for extracting the leg footings and the probable eff ectiveness of the leg jetting system (if fi tted). Temporary inability to extract the legs from the soil may involve serious risk if the unit cannot be quickly removed to shelter and/or cannot achieve the elevated survival mode and remain on location. Figure 9.1 Page 104 of 166 31 9.11 For jack-ups fi tted with hydraulic recycling jacking systems there is the additional risk that the jacking system may become temporarily immobilised through inability to extract fi xed or working pins during the leg extraction operation. If this occurs during a rising tidal cycle then damage or fl ooding may result. 9.12 Operations involving leg extraction from deep penetration may be considerably prolonged in cases where deep leg penetration has been achieved, particularly if the leg extraction operation is interrupted by periods of adverse weather. The onset of weather conditions exceeding the limits for refl oating the unit will require the jack-up to be re-elevated and preloaded and if this becomes necessary any progress that had been achieved with leg extraction prior to such onset will be almost entirely reversed. In addition to the risk described in 9.9 above, this may have a serious commercial impact in terms of costs caused by an extended delay. 9.13 The potential for seabed scour shall be considered. Special consideration shall be given to the movement of seabed soils caused by currents or waves and the potential impact this may have on the integrity of the jack-up foundation over time. At locations where risk of scour is deemed to exist, the foundation assessment shall include an assessment of the potential depth and rate of soil removal and that may aff ect foundation stability. The assessment shall include a caution to the eff ect that special jacking procedures may be required to mitigate the risk of foundation instability and should also recommend scour protection measures where appropriate. Page 105 of 166 32 10. Elevated operations 10.1 General requirements 10.1.1 Every jack-up shall be provided with an operating manual stating the design limits of the unit for elevated operations. 10.1.2 Every jack-up shall have adequate structural strength and overturning stability to withstand any combination of environmental conditions to which the jack-up may be subjected while elevated at a specifi ed location. Account shall be taken of the properties and characteristics of the seabed and subsoil to ensure there is adequate resistance for applied loads. If rotational foundation fi xity can be justifi ed this may be included in appropriate structural analysis. 10.1.3 No jack-up shall be elevated in weather unrestricted mode (section 5.2) on a location unless, prior to moving, the owner or operator of the unit has obtained from a competent person: a. A Meteorological Spot Location report (Appendix E) b. A Soils investigation and Jack-up Foundation Assessment report c. A site-specifi c assessment report carried out in compliance with the recommended practice confi rming that the jack-up is structurally capable of remaining on location and withstanding the extreme environmental conditions with all stresses remaining within allowable limits and that the seabed and subsoil will provide adequate resistance to withstand the loads at the footings. 10.1.4 No jack-up shall be elevated on location in weather restricted (section 5.3) unless, prior to moving, the owner or operator of the unit has obtained from a competent person: a. Defi ned limiting environmental criteria for the operation b. A Soils Investigation and Jack-up Foundation Assessment report (except as provided for soil investigations in section 18.6) c. A site-specifi c assessment report confi rming that the jack-up is structurally capable of remaining on location and withstanding the defi ned environmental criteria with all stresses remaining within allowable limits and that the seabed and subsoil will provide adequate resistance to withstand the loads at the footings. 10.2 Requirement for site-specifi c assessment 10.2.1 Before installing a jack-up on any location a site-specifi c assessment shall be performed by a competent person. 10.2.2 For multiple locations contained within a defi ned area, such as an off shore wind farm, the number of site-specifi c assessments for the site shall be suffi cient to consider the complete range of physical, environmental and geotechnical conditions across the site. Particular attention shall be paid to any variation in the soil conditions across the site. 10.2.3 The 50 year return period extremes shall be used for the site-specifi c assessment for permanently manned jack-ups unless the unit is to operate in weather restricted mode. 10.2.4 The 10 year return period may be considered where arrangements (including documented procedures) are in place for the safe removal of all personnel from the jack-up prior to the onset of weather conditions predicted to exceed the limit for safe disembarkation, having due regard for the level of confi dence in the forecast weather conditions. 10.2.5 The 10 year return period should only be used for de-manned jack-ups in cases where there is no risk to personnel and where the site developer and the jack-up owner have formally assessed the consequences of catastrophic weather damage to the jack-up and the potential threat to the environment and to shipping, installations, and property in the vicinity. For Page 106 of 166 33 cases where the reduced extremes are used it is recommended that the hull should be raised to comply with the 50 year air gap requirements. It is also recommended that site developers consult with interested parties such as the MCA, third party installation owners and underwriters and environmental agencies in connection with the possible consequences. 10.2.6 The site-specifi c assessment shall be carried out in accordance with the guidelines and recommended practice contained in the SNAME TR5-5A “Guidelines for Site Specifi c Assessment of Mobile Jack-Up Units”. 10.2.7 The dynamic response of the jack-up shall always be considered and assessed in accordance with SNAME TR5-5A. 10.2.8 The assessment may be carried out at varying degrees of complexity. These are expanded below at increasing levels of complexity. The objective of the assessment is to show that the acceptance criteria are met. If this is achieved by a particular level there is no need to consider a more complex level. 1. Compare site conditions with the jack-up’s design or other previous site-specifi c assessments. Assessment carried out at this level is subject to confi rmation that the previous assessment was carried out in accordance with the Recommended Practice and the jack-up’s design, confi guration and footing load is substantially similar to the jack-up considered in the previous assessment. 2. Carry out appropriate calculations according to the simple methods given in SNAME TR5-5A. Possibly compare results with those from existing more detailed/complex calculations. 3. Carry out appropriate detailed calculations according to the more complex methods given in SNAME TR5-5A. Reference is requested to the SNAME TR5-5A fi gure 2.1 overall Ffowchart for the assessment when determining the appropriate level of complexity [Appendix G]. 10.2.9 The site-specifi c assessment shall consider the addition of wind loads on temporary accommodation modules, equipment containers, temporary crane installations and project cargo items (if any) that may not have been considered in previous assessments or design reports. 10.2.10 Assessments at all levels require verifi cation by a competent person to confi rm that the jack-up’s original design report or the site-specifi c assessment has been assessed in accordance with the recommended practice. It is recommended that in all cases where a permanently manned jack-up is to remain elevated in unrestricted mode, the assessment should be verifi ed by an independent third party such as a classifi cation society or marine warranty surveyor. Page 107 of 166 34 11. Self-propelled and propulsion assisted jack-ups 11.1 Self-propelled jack-ups 11.1.1 Self-propelled jack-up vessels considered in this guideline shall be defi ned as power-driven ships capable of undertaking sea passages within their certifi ed trading area under their own power and without tug assistance. Such vessels shall be assigned an appropriate class notation signifying their type and capability. 11.1.2 Self-propelled jack-ups may be considered to be capable of undertaking transits and fi eld moves under their own power; however, due consideration shall be given in each case to the need for tug assistance for port entry and departure, positioning on site, navigating in constricted waters and areas with high velocity currents and positioning in deep water with the legs fully extended below the hull. In some cases national government and local port regulations may require tug assistance regardless of the vessel’s own propulsion force. 11.1.3 For vessels certifi ed for unrestricted transit between locations without tug assistance the propulsion force of the vessel shall be suffi cient to maintain control under conditions with sustained wind velocity 20 m/s, head current velocity 0.5 m/s and signifi cant wave height 5m. 11.1.4 The design, construction, management, manning and operation of self-propelled jack-ups is governed by fl ag state and port state regulations, international codes and standards and classifi cation society rules for ocean-going ships. Certifi ed compliance with these regulations, standards and codes does not waive the requirement for these vessels to comply with the recommended practice. 11.2 Dynamically positioned Jack-ups 11.2.1 In addition to the defi nition and provisions described in 11.1 (above) dynamically positioned (DP) jack-up vessels considered in this guideline shall be defi ned as ships equipped with dynamic positioning systems that are capable of positioning and station keeping under their own power and without tug assistance. 11.2.2 DP jack-ups shall be assigned an appropriate class notation signifying their type and capability. They will usually comply with the propulsion power requirements for unrestricted transit as defi ned above. 11.2.3 DP jack-ups shall comply with IMO MSC Circ.645, “Guidelines for Vessels with Dynamic Positioning Systems” which is the principal internationally accepted reference on which the rules and guidelines of other authorities and organisations, including classifi cation societies are based and with recognised standards for DP training, which are set out in IMO MSC Circ.738 “Guidelines for Dynamic Positioning System (DP) Operator Training”. 11.2.4 It should be recognised that the requirements indicated above represent a minimum standard and that some companies and some owners may require more than just a certifi cate of class and a statement of condition and equipment. 11.3 Propulsion assisted jack-ups 11.3.1 Propulsion assisted jack-ups considered in this guideline shall be defi ned as all other jack-ups that may be fi tted with propulsion equipment but that do not match the defi nitions listed in section 11.1 and 11.2 (above) and that may require tug assistance for transit and positioning. Page 108 of 166 35 11.3.2 For transit of propulsion assisted jack-ups not certifi ed for unrestricted transit the vessel’s propulsion capacity shall be suffi cient to maintain a minimum speed over the ground of 2 knots in the environmental condition considered. 11.3.3 For transit and positioning of propulsion assisted jack-ups, the requirement for assisting tugs may be waived and/or a reduction in the number and power of tugs may be acceptable where it is demonstrated that eff ective control over the movement of the unit can be maintained in the limiting environmental conditions considered and with the legs extended below the hull to the maximum depth likely to be encountered en route and on site. 11.3.4 For transit, propulsion assisted jack-ups as defi ned in this guideline shall be considered the same as non-propelled jack-up barges with respect to the requirements described in section 12. Page 109 of 166 36 12. Non-propelled jack-ups 12.1 Manned and unmanned tows 12.1.1 Jack-up barges certifi ed for manned towage under the loadline rules and having certifi ed crew accommodation should be manned by a marine crew for location and fi eld moves. 12.1.2 Jack-up barges not certifi ed for manned towage under the loadline rules may carry a riding crew on location moves and will always be manned for fi eld moves. Provision shall be made for embarking and disembarking riding crews whenever necessary and suffi cient means of escape, fi refi ghting appliances and lifesaving equipment for the riding crew shall be available ready for deployment. 12.2 Ballasting 12.2.1 The ballasting system, if fi tted, should be in good condition and suitable for the following: • Correction of draught or trim • Damage control purposes in event of hull damage, grounding etc • Modifi cation to the draft, trim, or heel if required for installation on location 12.2.2 In cases where the jack-up is unmanned, specifi cations and operating instructions for the ballast system shall be readily available and retained on board the lead tug with details of the ballast status during the tow. 12.2.3 In cases where the jack-up is not fi tted with a permanently installed ballasting system and power source, the jack-up or the tug must carry suffi cient portable pumps and equipment to carry out the operations considered in section 12.2.1. 12.3 Watertight integrity 12.3.1 All weather deck openings shall have adequate securing arrangements to ensure watertight integrity. 12.3.2 Door openings on weather decks shall be fi tted with sills and deck hatches shall be fi tted with coamings in accordance with International loadline regulations. Exemptions for semi-permanently bolted closures not fi tted with sills or coamings may be accepted subject to approval by the classifi cation society. 12.3.3 Compartment manholes shall be properly secured with bolts and gaskets, which must be maintained in good condition. A set of tools shall be provided on board for releasing and re-fastening the manhole covers. 12.3.4 If manholes to critical compartments are covered by cargo, grillage or seafastenings, care shall be taken to ensure they are properly secured before being covered. 12.4 Barge deck openings 12.4.1 Barges having low freeboards, where there is risk that a portion of the deck may become fl ooded in the damage stability condition considered in section 6.7, should be provided with “top hats” with suitable means of fi xing to the barge deck, which can be used in an emergency to gain access through a manhole that may be awash. 12.4.2 At least one standpipe shall be provided with suitable fi ttings, such that it can be screwed into sounding cap holes that may be awash. 12.5 Mooring arrangements 12.5.1 This section is applicable to the general provision of moorings for jack-ups alongside quays. Moorings for jack-up operations afl oat on site are covered in section 14. Page 110 of 166 37 12.5.2 Mooring bitts or bollards shall be fi tted on either side of the jack-up, suitably spaced in accordance with Class rules if applicable. As a minimum, mooring bitts or bollards shall be fi tted on each side at each end of the barge. At least four suitably dimensioned mooring ropes in good condition shall be carried on board. If the towing tug has spare mooring lines then this may be considered as a part of the barge’s mooring lines. 12.6 Navigation lights and shapes 12.6.1 The jack-up shall be equipped with navigation lights (including anchor lights) and day signals in compliance with the international regulations for the prevention of collisions at sea. 12.6.2 The lights shall be provided with suffi cient power or fuel from an independent source to last for the duration of the voyage plus a reserve of 50%. 12.6.3 A full set of spare navigation bulbs or gas mantles (as appropriate) and shapes shall be carried on the tug or the barge. In addition, spare parts for the navigation lights such as cables or hoses and connections (as appropriate to the system) shall be carried. 12.6.4 Where obstruction or danger to navigation is caused or is likely to result from installation of the jack-up on site; and where it is required under consents granted under the provisions of the Coast Protection Act 1949 - Consent to Locate Off shore Installations – provision for marking off shore installations; the jack-up shall be equipped with obstruction lights (white 360 degree Morse “U”) displayed at each corner of the vessel and with a fog signal. 12.6.5 Small jack-up barges operating within port limits may carry alternative obstruction lights such as fl ashing orange beacons, subject to the approval of the harbour master. 12.7 Access 12.7.1 Safe ladders that extend from the manhole opening to the compartment bottom shall be provided in each compartment. 12.7.2 Ladders shall be available on each side of the jack-up, extending to the lowest water line, to permit access when afl oat. Steel ladders and adjacent protective fenders, if fi tted, shall comply with class rules if applicable. Rope ladders shall comply with the rules for the construction and rigging of pilot ladders. The condition of these ladders shall be checked by the master of the jack-up or the tug master prior to commencing each jack-up transit and they shall be checked by the person intending to use them immediately prior to each use. 12.8 Fenders 12.8.1 It is recommended that adequate fenders are provided for berthing operations. 12.9 Towing arrangements 12.9.1 The jack-up shall be towed from the forward end using a bridle of suitable construction. If two tugs are used, the bridle may be split and each tug connected to a single leg of the bridle. Alternatively the second tug may be connected with a wire towing pennant through a closed fairlead to a separate towing connection. 12.9.2 When assessing the strength of tow connections and fairleads on the barge and bridle, the eff ect of the tug pulling at its maximum bollard pull in any direction shall be considered. Page 111 of 166 38 12.9.3 All towing equipment shall be in satisfactory condition. Test certifi cates for all the items specifi ed in this section shall be valid and available for inspection. Certifi cates shall provide clear identifi cation of the respective equipment. 12.9.4 Alternative towing confi gurations appropriate to operations conducted in narrow channels and confi ned areas may be used in inland waters and within port limits. 12.9.5 A plan or drawing of the towing arrangement showing the confi guration of the towing gear and each component and stating the breaking load (BL) of each component shall be prepared and shall be made available on board the towing vessel. 12.10 Tow connections 12.10.1 Towline connections to the barge shall be of the quick release type where possible. For strength purposes they shall be located over the intersections of transverse and longitudinal bulkheads and they shall be provided with adequate back-up structure. They shall also be secured against premature release. 12.10.2 The breaking (ultimate) strength of the tow connections shall conform to the following: • At least three times the static bollard pull of the tug • Designed to be greater than the breaking load of the bridle 12.11 Fairleads 12.11.1 Capped fairleads or panama type fairleads shall be fi tted forward of and in line with the tow connection points except where the towing connection is installed at the deck edge. Anti-chafe protection shall be provided along the deck edge. 12.11.2 The breaking strength of the fairleads and their connections to the barge deck shall be greater than that of the bridle. 12.12 Towing bridle 12.12.1 The towing bridle shall consist of two legs having an included angle at the apex between 45 degrees to 60 degrees. 12.12.2 If the bridle is a chain bridle it shall be composed of stud link chain, with enlarged open links at each end to facilitate connections. Connection should be made without removal of the stud from the stud link chain. 12.12.3 If a composite bridle is used it shall comprise two lengths of stud link chain, extending beyond the deck edge, connected to wire pennants fi tted with hard eye thimbles. 12.12.4 The bridle legs shall terminate in a shackled connection at a towing ring, triangular (Delta) plate, or other approved and certifi ed device. 12.12.5 The breaking strength of each bridle leg and bridle terminator shall generally be at least three times the static bollard pull of the tug. Under no circumstances should the breaking strength of each leg of the towing bridle be less than the BL of the towing wire. 12.13 Intermediate Tow Pennant 12.13.1 For longer tows in the transit condition an intermediate wire tow pennant shall be included between the towing bridle and the tug’s main towline. The pennant shall be fi tted with hard eye thimbles, and shall be at least 10m in length. The pennant may be shorter or may be omitted if necessary to reduce the overall length of the tow gear for in harbour or fi eld moves. Page 112 of 166 39 12.13.2 The breaking strength of the wire pennant shall be not less than that of the main towline of the tug, and shall be of the same lay as the main towline. 12.14 Shackles 12.14.1 The certifi ed safe working load (SWL) of all shackles included in the towing arrangement shall be greater than the static bollard pull of the tug to be used. Some reduction in this requirement may be allowed for a tug with a bollard pull in excess of 100 tonnes, but in any event their breaking load shall be greater than three times the bollard pull. 12.15 Bridle retrieving arrangements 12.15.1 A retrieval system shall be provided to recover the bridle in the event of the towline parting. 12.15.2 The retrieving wire shall be connected at the bridle apex either to the triangular plate or to an end link of the bridle leg. The wire shall be either led back to a retrieving winch, suitably led via an “A” frame or block arrangement or an alternative system appropriate for the area of operation shall be provided. 12.15.3 The retrieving winch shall be adequately secured and the capacity of the winch shall be suffi cient to take the load of the bridle, apex connection, pennant and connections with some reserve. The winch drum capacity shall be such that the required length of retrieval wire can be spooled. 12.16 Emergency towing arrangements 12.16.1 Emergency towing arrangements shall be provided for use in the event of loss of towline or bridle recovery system or other unforeseen circumstances. Two systems are suggested below although modifi ed forms of these may be accepted: 1. Two spare towing connections shall be fi tted forward located inboard of the main connections. A bridle, which may be of chain or wire and chain with a triangular plate or towing ring at the apex, shall be attached to these connections. The towing ring or delta plate shall be secured to the barge by lashings. A pennant, with hard eye thimbles, shall be shackled to the towing ring or delta plate and clipped or lashed along the barge side, outboard of all obstructions. At the stern of the barge a fl oating line with a buoy attached shall be shackled to the end of the pennant and streamed astern. 2. A single spare towing connection shall be fi tted, located on the barge centre line either forward or aft. If the connection is fi tted forward, a pennant shall be connected to it and led aft to a fl oating line, as in alternative one (above). If the connection is fi tted aft the towing pennant shall be fl aked on deck with the fl oating line connected to it. 12.16.2 The pennants and towing connections shall, in either of the above alternatives, be sized similarly to the main towing equipment and shall be lead over the top of the main bridle if fi tted forward. 12.17 Anchor 12.17.1 The jack-up shall have at least one operable anchor during transit. The anchor is to be of suffi cient capacity and with suffi cient length of mooring line available for emergency anchoring. 12.18 Safety rails 12.18.1 The perimeter of the jack-up deck shall be protected by permanently installed safety rails or removable stanchions and safety wires. These shall be designed and constructed in compliance with the applicable rules (Classifi cation society or MCA MGN 280). Openings in the rails or wires allowing for temporary access for mooring lines or other equipment shall be closed with chains or ropes when not in use. Page 113 of 166 40 13. Towing vessels 13.1.1 The proposed tug(s) shall be in satisfactory condition. The tug(s) and towing equipment, machinery, manning and fuel requirements shall be suitable for the proposed operation. Certifi cation and documentation required by the fl ag state shall be in order and the tug shall be classed by a recognised class society or certifi ed under the provisions of the MCA Small Commercial Vessel (SCV) and Pilot Boat Code (as currently set out in MGN 280) or foreign equivalent. 13.1.2 The tug(s) shall be provided with a Bollard Pull Test Certifi cate stating the continuous (sustained) bollard pull based upon a bollard pull test carried out within the last 10 years. 13.1.3 All towing equipment shall be in satisfactory condition. Test certifi cates for all items shall be valid and shall be available for inspection with clear means of identifi cation of the respective equipment. 13.1.4 The towing vessel shall have a spare towline that shall be similar in all respects to the main towline. Where the spare towline is not spooled on to a second winch drum it shall be stowed in such a manner that it can be spooled on to the main towing drum by the crew at sea. 13.2 Bollard pull requirements 13.2.1 The total environmental load acting on the jack-up and cargo due to the combined eff ects of the following conditions shall be calculated and the minimum tow-line pull required (TPR) should be calculated to hold the jack-up at zero forward speed in a fully developed gale defi ned as: • Signifi cant wave height (Hs): 5m • Wind speed: 20 m/s (approx. 40 knots) • Current: 0.5m/s (approx. 1 knot) 13.2.2 For short coastal tows, fi eld and harbour moves, lesser criteria for calculation of TPR may be agreed. Generally these should not be reduced below 15 m/s wind speed, 2.0m signifi cant wave height and 0.5m/s current, acting simultaneously. 13.2.3 The tow should be capable of making reasonable speed with average weather conditions throughout the passage. It is recommended that the tow be capable of maintaining a minimum speed of 5 knots in conditions with signifi cant wave height 2.0m and wind speed 10m/s. 13.2.4 In all cases due consideration shall be given to the number of tugs and the TPR required to control the jack-up in the anticipated maximum current on site with the legs fully extended below the hull. 13.2.5 The TPR should be related to the continuous static bollard pull (BP) of the tug(s) proposed by: TPR = Σ(BP x Te/100) Where: Te is the tug effi ciency in the sea conditions considered, % BP is the continuous static bollard pull of each tug (BP x Te/100) is the contribution to the TPR of each tug Σ is the sum for all tugs assumed to contribute to the TPR. Page 114 of 166 41 Bollard Pull BP ≤ 30 BP 30 - 90 BP > 90 80 80 80 50 + BP 80 80 H.sig Signifi cant wave height, metres BP Continuous static bollard pull, tonnes Te Tug effi ciency, in percentage of the bollard pull 30 + BP 52.5 + BP/4 75 BP 7.5 + 0.75 x BP 75 Calm H.sig = 2.0 m H.sig = 3.0 m H.sig = 5.0 m Table 13.1 - Estimation of the tug effi ciency 13.2.6 The tug effi ciency, Te, depends on the size and confi guration of the tug, the sea state considered and the towing speed achieved. In the absence of alternative information, information, Te may be estimated according to table 13.1 (below). 13.3 Towing winches 13.3.1 Towing vessels shall be fi tted with a suitable towing winch. Towing from a towing hook will not be accepted for open sea passages but may be accepted for harbour moves or movements in inshore sheltered waters. 13.3.2 Two towing drums shall normally be provided. Where a second towing drum is not fi tted then means of reconnection of the spare towline shall be supplied. The spare towline shall be in good condition and of the required strength. There must be suitable means for connecting the line to the tug and making a rapid reconnection to the emergency towline on the towed barge. 13.3.3 The tow winch shall have a minimum holding power of three times the static bollard pull of the tug at the inner layer on the drum. 13.3.4 All towing winches shall be fi tted with an emergency release brake mechanism. 13.4 Towline control 13.4.1 Towing pods where fi tted shall be of adequate strength, and well faired to prevent snagging. 13.4.2 Alternative arrangements for towline control may be accepted. If gog ropes are used they should be adjustable from a remote station. If a single gog rope system is fi tted then the connection point shall be on the centreline of the vessel. A spare gog rope shall be provided. 13.4.3 Mechanical, hydraulically or manually operated stops (pins) to control the towline shall, if fi tted, be well maintained, and capable of being withdrawn or removed when not in use. 13.5 Towing wire 13.5.1 For jack-up location moves the length of the tow wire should never be less than 500m and shall be determined as follows: L = (BP/BL) X 1200m. Page 115 of 166 42 13.5.2 For harbour moves and tows in inshore sheltered waters diff erent tow wire lengths may be accepted. 13.5.3 The wire shall be in good condition, free from kinks, snags and with no opening of strands. Hard eye thimbles or towing sockets shall be fi tted. 13.5.4 The MBL of the towing wire shall not be less than the following values: 13.5.5 Synthetic rope towlines shall not be used by the main towing vessel for jack-up location or fi eld moves. Synthetic fi bre towlines may be used by assisting tugs for harbour moves or tows in inshore sheltered waters. 13.6 Stretchers 13.6.1 Stretchers (if used) shall only be connected between the tug’s wire and the intermediate pennant and not to the bridle apex connection. In general, a stretcher made up as a continuous loop is preferable to a single line. The breaking load shall at least 1.5 times that of the main towline, and hard eye thimbles are to be fi tted at each end. These ropes are to be in good condition. 13.7 Tailgates/stern rails 13.7.1 The tailgate or stern rail, if fi tted, shall have an upper rail of radius not less than 10 times the diameter of the main towline. Smaller diameter may be accepted for inland tows and harbour moves. 13.7.2 Anti-chafe gear shall be carried on the tug and fi tted as necessary. The stern rail shall be well faired to prevent snagging. 13.8 Additional equipment 13.8.1 The following additional equipment shall be carried on board the towing vessel: • Oxygen/acetylene cutting equipment • Damage control equipment • Spare shackles (sized in accordance with the towing gear plus smaller sizes) • A searchlight to illuminate the tow and if the jack-up is unmanned: • Portable radio transmitter/receivers with spare batteries for communication • Hand lamps or torches with spare bulbs and spare batteries • A powered workboat fi tted with adequate means of launching and recovery (Excepting small tugs < 24m in length) • A portable pump equipped with suffi cient length of suction hose to enable dewatering of the compartments considered in section 6.7 and a self-contained power unit with suffi cient fuel for 12 hours running Bollard Pull (BP) Less than 40 tonnes 40 to 90 tonnes Over 90 tonnes 3 x BP (3.8 – BP/50) x BP 2 x BP BL Page 116 of 166 43 13.9 Bunkers An adequate quantity of fuel and consumables shall be on board for the proposed tow. An adequate amount of fuel at full speed consumption shall be kept in reserve. 13.10 Manning 13.10.1 The towing vessel shall be manned by a qualifi ed and experienced crew in compliance with the requirements of the tug’s fl ag state. There should be suffi cient crew to deal with contingencies such as the parting of a tow wire and the need to board the tow in the case where the towed jack-up is unmanned. 13.10.2 For towage of unmanned jack-ups there must be suffi cient accommodation and certifi ed life-saving capacity to accommodate the barge riding crew (if assigned) on board the towing vessel(s). Page 117 of 166 44 14. Moorings for positioning 14.1 General 14.1.1 Positioning is defi ned as the marine operation necessary to move the jack-up into the required position at a new location and to carry out the jacking and preloading operations necessary to install the unit on location. 14.1.2 All positioning operations are weather restricted and are to be conducted in sea states not exceeding the jack-up’s design limits for going on location (engaging the bottom). This means that the operation must be completed within 72 hours to the point where a temporary safe condition has been achieved. 14.1.3 The jack-up shall be considered to have reached a temporary safe condition when the integrity of the seabed foundation has been proven by preloading and the unit is capable of: a. Withstanding the reduced environmental loads selected for a weather restricted operation. or b. Withstanding the environmental loads corresponding to the 10 year seasonal condition for an unrestricted operation. A permanent safe condition for unrestricted elevated operation has been achieved when the unit can withstand the environmental loads corresponding to the 50 year all-year condition for the location. 14.1.4 Plans for positioning operations shall state the environment limits that are not to be exceeded. The limits shall not exceed the allowable criteria for engaging the bottom and/or for jacking and preloading as prescribed in the jack-up’s operating manual. 14.2 Positioning systems 14.2.1 When positioning close to surface or sub-sea structures, pipelines or cables and whenever fi ne positioning tolerances are required, jack-ups relying on dynamic positioning systems shall be assigned the appropriate class notation for dynamic positioning (DP). The capacity of the DP system shall be documented to demonstrate the vessel’s capacity to operate in DP mode in the defi ned environmental criteria and the system shall be function tested with acceptable results prior to commencing each positioning operation. 14.2.2 When positioning close to surface or sub-sea structures, pipelines or cables and when fi ne positioning tolerances are required, jack-ups not equipped with DP systems and all non-propelled jack-ups shall be equipped with a suitable mooring system except as provided in 14.2.3 and 14.2.4 (below). 14.2.3 At locations where positioning tolerances are less critical and where there is low risk of contact with any proximate surface or seabed obstruction, self propelled jack-ups may position using their propulsion system alone provided that the system is capable of controlling the jack-up’s speed and heading so as to reliably achieve a constant heading and near-zero horizontal movement relative to the seabed in the environmental conditions considered. 14.2.4 At locations where positioning tolerances are less critical and where there is no risk of contact with any surface or seabed obstruction, non-propelled jack-ups may position using tugs alone provided that the towing vessels are capable of controlling the jack-up’s speed and heading so as to reliably achieve a constant heading and near-zero horizontal movement relative to the seabed in the environmental conditions considered. 14.3 Mooring equipment and procedures for positioning afl oat 14.3.1 Mooring equipment for jack-ups (if fi tted) will normally consist of a four point mooring system using mooring winches, wires and anchors. The mooring system shall be designed and constructed and maintained in accordance with the rules of the vessel’s classifi cation society. Page 118 of 166 45 14.3.2 When positioning close to surface or subsea structures, pipelines or cables a mooring layout plan shall be prepared. Additionally a mooring analysis shall be performed if it is necessary to determine the clearances between the mooring lines and the nearby structures (see 14.4). Further details regarding the mooring analysis are given in 14.5. 14.3.3 The capacity of the mooring system, including the holding capacity of the anchors in the soil conditions on site shall be demonstrated as suffi cient to withstand the loads likely to be imposed during positioning of the jack-up in the environmental conditions considered. 14.3.4 The system shall be subject to regular survey and shall be maintained in good condition. The manufacturer’s test data stating the safe working load of the winch, the rated pulling capacity (fi rst wrap) and the rated brake holding capacity together with original certifi cates for each mooring wire, termination socket (if fi tted), shackle, anchor pennant and anchor shall be kept on board the jack-up. 14.3.5 In cases where the mooring winch is to be operated manually from a local control and where the operator can maintain a clear view of the winch drum, the fairlead, and the portion of the wire above the sea surface, the monitoring of line length and tension may be accomplished visually. 14.3.6 In cases where the mooring winch is operated remotely from a central control the equipment shall be fi tted with means of displaying length and tension data at the control station. If there is no clear view of the winch drums from the control station then either CCTV coverage shall be fi tted or competent crew equipped with radios shall be stationed safely in the vicinity of each winch to monitor the spooling of wires. 14.4 Clearances during positioning 14.4.1 Suffi cient clearance should be maintained between the jack-up and adjacent structures or other vessels and between mooring lines and fi xed structures or other vessels and sub-sea pipelines and cables during positioning. The direction of movement to the fi nal position and the environmental conditions shall be considered in order to establish suffi cient clearance. 14.4.2 The minimum clearance between the jack-up hull and an adjacent structure or another fl oating vessel during positioning should not be less than 3m at any point during the positioning operation. 14.4.3 The minimum clearance between the jack-up’s leg footings and an adjacent structure should not be less than 5m at any point during the positioning operation. The minimum clearance between the jack-up’s leg footings and a subsea pipeline or cable should not be less than 10m at any point during the positioning operation. 14.4.4 Smaller clearances may be accepted following a thorough review of the characteristics of the site, the procedures to be adopted, the limiting environmental conditions, back-up systems such as thrusters, lowering the legs to engage the seabed, the use of fenders and the deployment of sonar sector scan equipment when positioning close to subsea pipelines or cables. Due consideration shall be given to the consequences of contact and the ability to remove the jack-up from the location following completion of the operation. 14.4.5 The minimum clearances described below are based on the understanding that anchors are deployed from an anchor handling tug equipped with a DGPS based tug management system that has been specifi cally calibrated for the selected site. Greater clearances shall be allowed where this equipment is not fi tted or is not in service. Page 119 of 166 46 14.4.6 Greater clearances than those described in this section are usually required around ‘hot’ hydrocarbon installations and pressurised pipelines. Anchors shall not be deployed within designated pipeline or cable corridors or exclusion zones. Note that exclusion zones may include areas excluded in marine and environmental permits. 14.4.7 Port authorities, gas and oilfi eld pipeline operators and other concerned parties may have more stringent clearance requirements related to the protection of critical pipelines and sub-sea or overhead electrical and communications cables. These must be complied with. 14.4.8 The clearance between a jack-up mooring line and a fi xed structure or fl oating vessel during positioning shall not be less than 5m. 14.4.9 The horizontal clearance between a jack-up mooring line not crossing (parallel to) a sub-sea pipeline or cable should not be less than 50m. The vertical clearance between a jack-up mooring line crossing a sub-sea pipeline or cable should not be less than 5m. Smaller clearances may be accepted provided that it can be demonstrated that there is no risk of contact between the mooring line and the pipeline or cable. 14.4.10 The horizontal clearance between a jack-up’s anchor and a fi xed structure or sub-sea pipeline or cable shall not be less than 250m if laid across, or 150m if laid parallel to the pipeline or cable. This clearance may be reduced to 50m if the anchor drag sector is away from the pipeline or cable. 14.4.11 Contact between individual lines is not accepted for crossing anchor lines from two or more vessels. 14.4.12 Minimum recommended clearances are tabulated below: Element Jack-up hull Leg footing Mooring line Mooring line Anchor Anchor Anchor Any Any Not crossing Crossing Drag sector away Drag parallel to Drag sector toward 3m 5m 5m 5m 50m 150m 250m - 10m 50m - 50m 150m 250m 3m (afl oat) 3m (afl oat) - 5m - - - Direction Fixed structure or fl oating vessel Horizontal Subsea pipeline or cable Vertical Recommended minimum clearances during positioning 14.5 Mooring analysis 14.5.1 For positioning a jack-up in non-critical locations a mooring layout plan shall be prepared. 14.5.2 For long term moorings defi ned as any mooring system that is deployed not solely for positioning purposes but also for the purpose of station-keeping the mooring arrangements should comply with the guidelines contained in section 14.4 (above) and should be analysed for the appropriate environmental conditions applicable to the season and time period for which the unit will be moored. Page 120 of 166 47 14.5.3 Mooring systems used for the purpose of station-keeping may, in general, be analysed by quasi static methods unless the unit is moored close to a fi xed or fl oating structure or any natural hazard or obstruction that could result in contact damage in which case dynamic analysis should be performed. The analysis should describe the possible excursions under defi ned environmental loads and should demonstrate that there is no risk of contact between the jack-up or its mooring lines and the proximate fi xed or fl oating structure or other obstruction with the moorings intact and in the single line failure mode. 14.6 Anchor handling tugs 14.6.1 Anchors should be deployed by anchor handling tugs. These vessels should be equipped with bow or stern rollers and winches, jaws, forks, pins, release devices and safety rails as appropriate for the safe control of the anchors and wires and to ensure proper protection for the tug crews. 14.6.2 Anchor handling tugs engaged in deploying anchors in the vicinity of fi xed structures or sub-sea pipelines or cables should be equipped with a DGPS based tug management system that has been calibrated for the selected site. 14.6.3 An anchor handling tug carrying an anchor across a sub-sea pipeline or cable should carry the anchor on deck and not suspended from the stern roller. 14.7 Anchor handling procedures 14.7.1 Anchor handling procedures shall be documented. The procedures shall include scale anchor plans and shall describe the complete anchoring operation, the mooring equipment and details of the method of deploying and recovering anchors. The procedure shall include contingency plans for vessel and equipment malfunction or breakage. 14.7.2 The procedure shall also include a plan showing areas where anchors may not be deployed for any reason and shall describe the precautions to be taken to avoid contact between anchors and mooring wires and fi xed structures, subsea pipelines and subsea cables where applicable. 14.7.3 Where required to maintain the vertical clearances (section 14.4) these precautions may include the deployment of line buoys (damage preventer buoys) installed at points along the length of the mooring wire to prevent it from coming into contact with subsea pipelines or cables. Additional precautions may also be necessary concerning the maintenance of tension in moorings during deployment and recovery to ensure that slack bights of wire do not contact fi xed structures, subsea pipelines and cables. 14.7.4 Where the risk of contact between mooring wires and subsea cables and/or contact with the seabed in the vicinity of cables buried to a depth of 1m or less cannot be avoided by using line buoys then means of protecting the sub-sea cables such as rock dumping, concrete/steel mattresses or bolted steel cable protectors shall be employed. 14.7.5 Anchor plans should be reviewed and approved by the owners or operators of fi xed structures, subsea pipelines and cables in the vicinity. 14.7.6 Prior to commencing anchor handling the master of the jack-up and/or the tow master (if the master is not the tow master) should arrange a meeting with the tug master(s) of the anchor handling tugs and the survey team to discuss the procedures to be adopted and the safety precautions to be observed. Sequential operations involving the same procedures, equipment and personnel may be addressed at a single meeting. Page 121 of 166 48 15. Lifting and load transfer 15.1 General 15.1.1 Lifting operations and lifting equipment shall comply with the Lifting Operations and Lifting Equipment Regulations 1998 (S.I.1998/2307) (LOLER). These regulations are supported by the HSE’s technical guidance and approved codes of practice contained in: • Technical guidance on the safe use of lifting equipment off shore • Safe use of lifting equipment – approved code of practice and guidance 15.1.2 Marine Lifting Operations shall also comply with the instructions and recommendations contained in a recognised guideline document, such as:- • GUIDELINES FOR MARINE LIFTING OPERATIONS Noble Denton 0027/ND Rev 7 – 15, April 2009 • LOC Guidelines for Marine Operations – Marine Lifting: LOCG-GEN-Guideline 003 Rev. 0, May 2003 • Det Norske Veritas (DNV) Rules for the Planning and Execution of Marine Operations, January 2000. Chapter 5: Lifting • MCA MGN 280 (M) Small vessels in commercial use for sport or pleasure, workboats and pilot boats - alternative construction standards MS+FV lifting operations and lifting equipment regulations 2006. The Documents listed above are mainly concerned with lifting operations by fl oating crane vessels; therefore the following section of this document provides additional information on marine lifting operations carried out by jack-ups. 15.2 Planning 15.2.1 Operational planning shall be based on the use of well-proven principles, techniques, systems and equipment to ensure acceptable Health and Safety levels are met and to prevent the loss or injury to human life and major economic losses. 15.2.2 All planning for load out and off shore lifting operations is based where possible on the principle that it may be necessary to interrupt or reverse the operation. However, this may be impractical for some operations and in cases where the operation cannot be reversed, points of no return, or thresholds, shall be defi ned during planning and in the lifting manual. Checklists should be drawn up detailing the required status to be achieved before the operation proceeds to the next stage. 15.2.3 A comprehensive lifting manual shall be prepared. This manual may form part of an installation manual for the module or component to be lifted and shall include, as a minimum, details of the following: • Description of the operation • Time schedule • Lift module dimensions weight and COG • Details of stabbing guides and beams (if used) • Details of auxiliary winches and tag lines • Details of the jack-up and attending vessels (tugs, transport barges etc) • Jack-up station keeping arrangement (jacked up, leg-stabilised, moored afl oat, DP) • Transport barge station keeping arrangement • Specifi c operations (ballasting, ROV, divers, survey measurements etc) • Vessel positioning procedures • Confi guration and certifi cation of the crane • Certifi cation of all lifting equipment Page 122 of 166 49 • Crane radius curve (manufacturers/class de-rating of crane when afl oat if applicable) • Proposed clearances between lifted module/crane/legs/vessels/existing structures • Lifting equipment details, rigging weights and rigging drawings • Limiting environmental criteria for each lift • Plan and profi le drawings • Organisation, communications and responsibilities • Recording procedure • Pre-lift checklist • Safety and contingency plans 15.3 Documentation and design calculations 15.3.1 Each crane shall be provided with a report of inspection and a valid certifi cate of test. Permanently mounted vessel’s cranes shall be certifi ed by the jack-up’s classifi cation society and details of annual inspections and fi ve year tests shall be recorded in the vessel’s lifting gear register. 15.3.2 The lifting capacity of the crane shall be defi ned and the basis for the load/radius curve shall be clearly described in the crane manual or similar document. When mobile cranes are used onboard the jack-up, care shall be taken to determine whether the weights of crane blocks, hooks and wires have been included or excluded in the defi ned lifting capacity. 15.3.3 Temporary and mobile cranes not forming part of the jack-up’s permanent equipment shall be certifi ed and shall be seafastened in accordance with the provisions of section 7. 15.3.4 Reference is requested to the fl owcharts contained in the referenced guideline documents on marine lifting (section 15.1.2) which provide a useful summary of the stages in the design and analysis of lifts using a single crane or two cranes. 15.4 Loads and analysis 15.4.1 The module design weight (MDW) shall include adequate contingency factors to allow for the module being heavier than intended. After completion, the module shall be weighed using an approved weighing method. The as-weighed weight shall be increased by 3% to account for weighing inaccuracies. Documentation should be provided to demonstrate that the equipment and procedures adopted for weighing have the required accuracy. 15.4.2 A further component, the rigging weight (RW), shall be added to the MDW. This allowance represents the weight of the lift rigging and shall include the estimated weight of all shackles, slings, lifting beams, spreaders and rigging platforms. In the fi nal design phase the actual weight of rigging (including contingencies) shall be used. 15.4.3 The plan position of the centre of gravity shall generally be restricted for the following reasons: • To allow for the use of matched pairs of slings • To prevent overstress of the crane hook • To control the maximum tilt of the object The module COG should be kept within a specifi ed design envelope. The length of the lifting slings/grommets shall be chosen to control the tilt of the module. For practical purposes the tilt of the module should not exceed 2 degrees, however some modules require fi ner vertical tolerance for installation. Page 123 of 166 50 15.4.4 RW shall be added to the MDW to give the static hook load (SHL): MDW + RW = SHL. The SHL shall be checked against the approved crane capacity curve at the maximum planned outreach. 15.4.5 Where the lifting situation may give rise to a dynamic increase in the eff ective load the dynamic hook load (DHL) shall be obtained by multiplying the SHL by a dynamic amplifi cation factor (DAF): DHL = SHL x DAF. The DAF allows for the dynamic loads arising from the relative motions of the crane vessel and/or the cargo barge during the lifting operations. The DHL shall be checked against the approved crane capacity curve at the maximum planned outreach. 15.4.6 For lifts in air the dynamic load is normally considered to be highest at the instant when the module is being lifted off its grillage. This load, and hence the appropriate DAF, should be substantiated by means of an analysis which considers the maximum relative motions between the hook and the cargo barge and takes account of the elasticity of the crane falls, the slings, the crane booms and the luffi ng gear. 15.4.7 The description of such an analysis must clearly state the assumed limiting wave heights and periods such that, if the calculated value of DAF is critical to the feasibility of the operation, then those conducting the lift will be aware of the limiting seastates. 15.4.8 In the absence of a dynamic lift response analysis being carried out the values of DAF given in table 15.4.8 may be used for lifts in air from a jack-up. 15.4.9 It should be noted that some crane capacity curves already take due account of the DAF and care should be taken to ensure that the DAF is not considered twice in the design calculations. Weight of module Lift off shore Lift inshore Lift off shore Lift off shore Lift inshore Floating mode lifting from vessel afl oat Elevated mode lifting from vessel afl oat Elevated mode lifting from leg stabilised barge or jack-up Elevated mode lifting from quayside 1.50 1.30 1.15 1.00 1.00 1.40 1.20 1.10 1.00 1.00 N/A N/A 1.05 1.00 1.00 < 100 tonnes 100 – 1,000 tonnes Horizontal Table 15.4.8: DAF factors for jack-up Page 124 of 166 51 15.5 Minimum clearances During all phases of a lift the following minimum clearances should be maintained. Recommended clearances are tabulated below. Smaller clearances may be accepted following a thorough review of the characteristics of the lift, the procedures to be adopted, the limiting environmental conditions and the consequences of contact. 15.6 Jack-up crane vessel stability 15.6.1 For a jack-up lifting in the afl oat condition, load and stability calculations shall be provided to demonstrate that the condition at each stage of the lift operation is within the limits contained in the stability book and/or the operating manual. 15.6.2 A failure mode and eff ects analysis (FMEA) is a requirement of class for DP jack-ups. The requirement for an additional FMEA or otherwise for a DP jack-up during lifting or positioning shall be determined in consideration of the risk to persons, DP class, proximity of other structures or vessels, lifting confi guration, operating environment and any other factor particular to the circumstances of the proposed operation. 15.6.3 For a jack-up lifting in the elevated condition it shall fi rst be verifi ed that the preload operation has been carried out in accordance with the instructions contained in the operating manual and/or in accordance with any approved site-specifi c procedures that may have been developed for the location. 15.6.4 For a jack-up lifting in the elevated condition, load calculations shall be provided to demonstrate that the load condition at each stage of the lift operation is within the limits stated in the operating manual and that the jack-up’s maximum allowable elevated weight (operating) and centre of gravity remains within the specifi ed transverse and longitudinal limits throughout the lifting operation. The calculations shall demonstrate that, during lifting and slewing, individual leg loads will not approach or exceed the legs loads achieved during preloading. 15.6.5 Caution shall be exercised at locations where the seabed foundation may have become altered by scour or other eff ect over time. In such cases the jack-up preload or pre-drive sequence should be repeated prior to commencing a lift operation. The jack-up should be precisely levelled prior to commencing a lift operation. 15.6.6 Jack-ups with four or more legs should ensure that the leg loads are equalised before lifting in order to reduce the risk of further slight settlement during the lift operation. Following this test the leg loads should be adjusted (if required) to the prescribed loads for lifting and locking devices, fi xed catches or pins should be engaged (if required) in accordance with the instructions contained in the operating manual. 15.6.7 When carrying out lifts with two cranes, documentation should be submitted to demonstrate that the jack-up crane vessel can safely sustain the changes in hook load which arise from the tilt and yaw factors combined with environmental eff ects in the lifting calculations, specifi cally considering allowable cross lead angles for the crane booms. Jack-up 3m 3m 3m 3m 3m Below the lifted module Between module and jack-up legs Between module and crane boom Between spreader bar and crane boom Between module and fi xed structure 1m 1m 1m 1m 1m Floating mode Elevated mode Page 125 of 166 52 16. Crew transfer 16.1 Principal requirements 16.1.1 Equipment shall be provided to allow the crew, project personnel and visitors to safely embark and disembark when the jack-up is: • Moored afl oat or elevated at a quayside • Afl oat or partly elevated with the hull at draft inshore or off shore • Elevated inshore or off shore It should be recognised that there will be operational circumstances in which safe access cannot be provided and at which time transfer of personnel should not be attempted. 16.1.2 The access equipment shall comply with the following regulations and codes: • The Merchant Shipping (Means of Access) Regulations SI 1988/1637 • The Merchant Shipping (Safe Movement Onboard Ships) Regulations 1988 • MCA Code of Safe Working Practice for Merchant Seamen • MCA Small Commercial Vessel and Pilot Boat (SCV) Code as set out in MGN 280 The responsibility for the provision and maintenance of the jack-up’s access equipment shall be the responsibility of the jackup owner or operator. 16.1.3 Routine access to and from the jack-up will normally be from the quayside or off shore platform (or other fi xed structure) or barge or from a crewboat. The term crewboat shall be deemed to include tugs, workboats or RIBs used for personnel transfer. Transfer of personnel by helicopters has not been considered in this guideline. 16.1.4 The safe condition of quaysides and quayside equipment, off shore platforms and crewboats used for the transfer of personnel to and from jack-ups shall be the responsibility of the party who owns or operates the quayside, platform or crewboat. Crewboats shall be constructed, maintained, equipped, manned, and operated in accordance with the rules laid down by their registry and class or in accordance with the SCV code, as applicable. 16.1.5 The master of the jack-up and master of the crewboat and the person supervising the transfer shall ensure that the selected method of transfer of personnel to and from the jack-up is safe in the prevailing circumstances and that equipment used for the transfer is in satisfactory condition and has been properly rigged and/or prepared for the transfer. In assessing the level of safety the master of the jack-up should be guided by the instructions and recommendations contained in the site-specifi c documented transfer procedure. 16.1.6 The master of the jack-up and/or the person supervising the transfer shall also ensure that all transferees have received the required training in the selected method of transfer and that the appropriate PPE is worn for each transfer. 16.1.7 Each person using a gangway, ladder, personnel carrier or other device for transfer to/from a jack-up, off shore platform, crewboat or quayside shall individually and separately accept responsibility for their own safety. No person should attempt a transfer at any point unless they have received the appropriate training and instruction and are confi dent that they can accomplish the movement safely. 16.1.8 The safe operation of the jack-up and/or platform and/or crewboat is the responsibility of the owner/operators, as applicable. The individual responsibilities of the transferee and the vessel masters and crew involved in supervising transfers, or operating equipment used for transfers, shall be clearly established and documented. Page 126 of 166 53 16.1.9 Specifi c procedures for routine personnel transfer shall be clearly established and documented. For each mode of transfer these procedures should, as a minimum, include details of the equipment to be used, equipment and transfer mode operating limits, training and PPE requirements, provision of safety equipment, communications protocols and the instructions to be given and checks to be carried out prior to each transfer. 16.2 Transfer when the jack-up is moored afl oat or elevated at a quayside 16.2.1 When the jack-up is positioned at a quayside the transfer of personnel should be accomplished using an approved gangway and associated equipment that complies with the Merchant Shipping Regulations (means of access) 1988. The gangway shall be rigged in accordance with the advice contained in the UK Code of Safe Working Practice for Merchant Seamen. 16.2.2 A dock mounted stair tower shall be provided in circumstances where there is a signifi cant diff erence in height between the jack-up deck and the quayside, such that the angle of inclination of the gangway, if used alone, would exceed its design limits. 16.2.3 Stepping over from the jack-up to/from the quayside shall be avoided, even in cases where the gap is small and the jack-up deck and quayside are level or almost level. Scaff olding, planks and other temporary equipment shall not be used for the transfer of personnel to/from the quayside. 16.3 Transfer when the jack-up is afl oat or partly elevated with the hull at draft 16.3.1 When the jack-up is afl oat underway or positioned on location with the hull at draft the transfer of personnel to/from a crewboat shall be accomplished using a fi xed steel boarding ladder (if fi tted) or an approved rope ladder rigged on the lee side or end of the jack-up. A rope ladder (if used) shall be constructed and rigged in accordance with the advice contained in the U.K. Code of Safe Working Practice for Merchant Seamen. 16.3.2 Personnel may transfer directly from the jack-up to/from the crewboat without using a ladder in cases where: • The crewboat has a boarding platform fi tted with a safety rail • The personnel transferring are not required to climb over the safety rail • The height of the boarding platform is almost level with the jack-up’s deck • The vertical movement of the boarding platform in the sea state is ≤ 30 cm • The jack-up’s boarding point has an access opening in the deck rail or bulwark • The boarding point is manned, lighted and equipped with a lifebuoy and line 16.3.3 The jack-up’s fast rescue craft, man overboard boats, workboats or RIBs fi tted with class approved davit launch and recovery systems may be used for the occasional transfer of trained seamen and divers. Such transfers should be subject to a specifi c risk assessment. 16.3.4 Transfer using personnel baskets and man-riding cranes should not be attempted while the jack-up is in the fl oating mode. 16.4 Transfer when the jack-up is elevated on location 16.4.1 When the jack-up is elevated to an air gap on an inshore or off shore location the transfer of personnel to/from the jack-up is usually accomplished using. • Bridge to adjacent fi xed structure (e.g. wind/current turbine or platform). (Further reference is required for specifi c guidance on turbine access) Page 127 of 166 54 • Man-riding crane and certifi ed personnel carrier • Other approved mechanical device certifi ed for manriding 16.4.2 The use of fi xed steel ladders or rope ladders for access by personnel to elevated jack-ups requires extreme caution and should only be attempted in slight sea conditions. Plans for the use of rope ladders should be subject to special consideration and specifi c risk assessment. 16.4.3 The capacity of purpose built bridges and gangways used for access shall be certifi ed, or in the absence of a certifi cate, a report on the structural capacity from a competent person shall be provided. 16.4.4 Man-riding cranes shall comply with LOLER regulations. In addition a certifi cate or report shall be provided to demonstrate that the man-riding crane is equipped in accordance with the guidance provided in HSG 221. 16.4.5 Transfer of personnel by personnel basket or other carrier shall be undertaken in accordance with the guidance contained in HSE off shore information sheet, January 2007: Guidance on Procedures for the Transfer of Personnel by Carriers. The type of personnel carrier used shall comply with guidance contained in HSG 221. Page 128 of 166 55 17. Marine control for jack-up operations 17.1 Marine control during transit and positioning 17.1.1 Jack-ups in transit and during positioning shall comply with the applicable marine traffi c regulations promulgated by the port state controlling the waters through which the transit is made and in which the jack-up is positioned. The jack-up owner or operator shall be responsible for compliance with these regulations. 17.1.2 Jack-up transit and positioning operations usually require notices to mariners to be issued in advance, during, and on completion of each movement. Regulations also require that routine reports are made to vessel traffi c services wherever applicable. The jack-up owner or operator shall be responsible for ensuring that the required notices, advisories and warnings are issued and for maintaining communication with the maritime authorities concerned. 17.1.3 Jack-ups operating within port limits shall comply with rules promulgated by local port or river authorities, pilot services and harbour masters. The jack-up owner or operator shall be responsible for maintaining communication with the marine authorities that operate or exercise control in the area through which the jack-up is transiting and in which the jack-up is operating. 17.2. Nearshore and off shore project sites 17.2.1 In addition to large scale navigational charts, jack-ups operating at marine project sites shall be provided with large scale drawings of the project site in both hard copy and electronic format where such fi les are in use on the jack-up’s survey system. The drawings shall contain information plotted using a system of co-ordinates that is compatible with the survey system in use on the jack-up and they shall be continuously updated to refl ect both natural and man-made changes as they occur. The following information shall be included: • Bathymetry • Seabed surface features including debris and obstructions • Position, dimensions and depth of any previous jack-up ‘footprints’ • Position and dimensions of fi xed surface and subsea structures • Positions (as laid) of all subsea pipelines and cables and proposed cable routes • Positions and heights of overhead cables • Positions of vessels and anchors of units on long term moorings • Clear fairways and exclusion zones • Designated zones within the site together with notation on the reason for zoning 17.2.2 Jack-ups operating as single isolated units and attended only by their towing vessels (if any) require no additional marine control system. Masters of towing vessels (if any) shall be provided with the procedure document or method statement for the proposed transit and positioning operation and they shall be briefed by the master of the jack-up in advance of the proposed movements. 17.2.3 For jack-ups operating off shore it is recommended that a 500m radius exclusion zone centred on the unit’s position be maintained during positioning and elevated operations. No other vessel should enter or move within this exclusion zone until clearance has been received from the master of the jack-up. A lookout on the jack-up or the attending tug should be maintained throughout operations on site. Rogue vessels or small craft approaching the zone without notice should be advised by all available means to avoid this zone. Page 129 of 166 56 17.2.4 Where simultaneous operations involving multiple vessels are planned to take place within the same area, marine traffi c control (MTC) under a single designated authority is required. Coordination shall be arranged between the various contractors and vessels deployed in order to avoid unsafe confl ict between vessel movements and moorings. This is particularly important for jack-up positioning operations and to ensure the safety of the jack-up after elevation. 17.2.5 The area in which MTC applies shall be defi ned. All proposed vessel movements within the defi ned area shall be reported to the marine traffi c controller in advance for planning purposes. No movement shall take place within the area until clearance is received from the marine traffi c controller. The MTC shall be advised on completion of each movement. 17.2.6 Jack-ups operating within an area subject to MTC shall be fi tted with the navigation and communication equipment necessary to monitor and transmit communications and to transmit radio identifi cation signals and messages compatible with systems used by the MTC. Page 130 of 166 57 18. Conduct of jack-up operations 18.1 Sources of guidance on the conduct of jack-up operations 18.1.1 The jack-up’s operating manual is the principal source of instruction and guidance on the conduct of jack-up operations. The operation of vessels governed under the ISM code shall be guided by the relevant safety management manuals. The operation of the vessel’s jacking system, cranes and all machinery and equipment should be conducted in accordance with the relevant manufacturer’s manuals. 18.1.2 Specifi c guidance contained in procedure documents should be followed. Proposed departures or deviations (if any) from the instructions and recommendations contained in the manuals referred to in 18.1.1 (above) should follow a management of change (MOC) procedure and should be documented at the planning stage. 18.1.3 The operation should be conducted in such a way that there is no unplanned departure from the guidance provided in the sources listed above except in cases of emergency when the master of the jack-up deems it necessary to take diff erent action or adopt an alternative procedure in order to avoid an unsafe condition or risk thereof. Provision for such emergencies should be identifi ed in the MOC procedure. 18.1.4 In cases where circumstances arise requiring a change to the existing guidance then the operation in progress should be temporarily suspended and the circumstances investigated in accordance with the MOC procedure. Alternative procedures should only be adopted when they have been reviewed, approved and signed off in accordance with the MOC procedure. 18.1.5 The use of jack-up move checklists is recommended. 18.2 Manning for operations 18.2.1 The jack-up shall be manned with a competent marine crew in accordance with the vessel’s Safe Manning Certifi cate (if issued) or in any case with suffi cient crew to manage the vessel and the marine operations making proper allowance for rest periods. 18.2.2 Jack-ups without any propulsion units and issued with loadline or loadline exemption certifi cates for unmanned tow may carry a riding crew suffi cient to manage the vessel and the operations subject to the provision of adequate life saving and fi refi ghting equipment. 18.2.3 Where a riding crew is carried the attending tug(s) shall have suffi cient certifi ed capacity to accommodate the riding crew and suitable provision to safely transfer all personnel from the jack-up to the tug. The maximum weather conditions for transfer of personnel from the jack-up to the attending tug(s) should be established prior to commencing the tow and provision should be in place for the transfer of personnel from the jack-up to the tug well before deteriorating weather conditions approach the level that would render disembarkation unsafe. 18.2.4 For propulsion assisted or non-propelled jack-ups in the transit condition the manning should be reduced as far as is practicable by the removal of non-essential personnel before departure. In any event the total complement shall not exceed 50% of the total survival craft/liferaft capacity for the transit mode. Manning need not be reduced for fi eld moves. 18.2.5 There is no requirement to reduce manning in the transit mode for self-propelled jack-ups classed for unrestricted transit through the certifi ed trading area; however, the total number of persons on board shall not exceed the vessel’s certifi ed lifesaving capacity. Page 131 of 166 58 18.2.6 For all jack-ups operating in the elevated mode the manning level including day visitors shall never exceed the jack-up’s maximum certifi ed capacity except in cases where emergency assistance is being rendered by the jack-up to another vessel in distress. 18.2.7 Well prior to the onset of extreme storm conditions and before placing the jack-up in the storm survival mode, consideration should be given to the available means of evacuation and the timely removal of all non-essential personnel. 18.3 Weather forecasts 18.3.1 The safety of most jack-up operations is dependent upon the regular receipt of reliable weather forecasts. 18.3.2 Excepting UK Met Offi ce forecasts, no reliance shall be placed upon weather information freely available to the public on the internet or information broadcast by commercial radio and television stations of the type that is general in nature and intended only for those engaged in non-critical leisure activities. 18.3.3 Shipping forecasts, inshore forecasts, gale and strong wind warnings and the latest marine observations issued by the UK Met Offi ce shall be monitored on a regular basis. Routine forecasts and warnings broadcast by the UK Met Offi ce may be suffi cient for jack-up operations conducted in harbours or within sheltered bays and estuaries. 18.3.4 For all other jack-up transit, positioning and elevated operations conducted anywhere outside sheltered harbours or outside sheltered bays and estuaries, route-specifi c and site-specifi c marine weather forecasts (as applicable) are required. 18.3.5 Route and site-specifi c forecasts are required at intervals not exceeding 12 hours and these should be broken down into four time periods (00, 06, 12 and 18 hundred hours U.T.) for the following three days plus an outlook for the following two days. Each forecast should contain the following meteorological information: • Wind directions, speed and gusts at 10m • Wind directions, speed and gusts at 50m • Maximum wind wave height and period • Signifi cant wind wave height and period • Swell wave direction height and period • Visibility • Temperature • Barometric pressure per period • Type of weather per half-day • Overall conditions in the form of surface pressure isobar maps • Forecast reliability ranking for each forecast • Contact details for the duty forecaster (to be available on a 24/7 basis) 18.4 Transit 18.4.1 Prior to commencing the transit the person responsible for conducting the operation shall be in possession of the relevant site-specifi c assessment report for the proposed new location and shall be familiar with the information, instructions and recommendations contained in the documents described in section 18.1.1 and 18.1.2 (above). Page 132 of 166 59 18.4.2 A weather forecast indicating suitable conditions for the proposed transit shall be received and reviewed prior to jacking down. On site conditions of wind, wave and current should be carefully observed and assessed to ensure that the prevailing conditions will not adversely aff ect control of the movement of the jack-up on departure from the location. 18.4.3 Before jacking down, the load and stability calculations should be completed and all equipment and cargo secured for transit. The jacking system and all main machinery and equipment should be tested and the person responsible for the conduct of the move should be satisfi ed that the jack-up and the towing vessel(s) (if any) are in all respects ready for the move. 18.4.4 Before jacking down the jack-up’s position, heading and clearances between adjacent structures or obstructions should be carefully checked. Particular attention should be paid to the air gap, the water depth, the predicted rise or fall of the tide and the individual leg penetrations. These levels should be checked against individual leg height readings so as to ensure that the person responsible has a complete understanding of the jack-up’s elevated status before jacking down. 18.4.5 Caution should be exercised when raising the legs to avoid the risk of injury to personnel on deck caused by loose objects and marine growth breaking loose and falling from the legs. 18.4.6 For manned units, routine checks of the watertight integrity and seafastening arrangements should be carried out during transit afl oat. For unmanned units routine inspection of the barge draft and trim can be carried out by the crew of the towing vessel using binoculars. 18.4.7 Jack-ups in transit are required to have an anchor ready for release during transit and positioning; however, to avoid accidental release the anchor should be secured with a quick-release mechanism. 18.4.8 A schedule of regular radio contacts should be maintained between the towing vessel and manned jack-ups under tow. Weather forecasts shall be monitored and weather observations logged. 18.5 Positioning 18.5.1 To ensure that the limits prescribed in the operating manual are not exceeded during positioning, a weather forecast shall be obtained indicating that the prescribed limits will not be exceeded over the time required for positioning plus a contingency for delay. On site conditions of wind, wave and current shall be carefully observed to ensure that the prevailing conditions and any anticipated changes will not adversely aff ect control of the jack-up during the approach and positioning. 18.5.2 Prior to approaching the proposed new location the leg securing system (if fi tted) should be disengaged and the jacking system and all machinery and equipment to be used for the positioning operation such as survey gear and mooring winches should be function tested. 18.5.3 Crane booms shall remain secured for the transit condition and all equipment and cargo seafastenings shall be kept in place until the positioning operation is complete. The towing vessel shall remain connected to the main towing bridle until the positioning operation is complete. 18.5.4 The jacking, preloading and elevating operations shall be undertaken in accordance with the instructions and recommendations contained in the operating manual and the jacking system manual (if not included in the operating manual). Limits specifi ed in the manuals shall not be exceeded and all precautions described in the manuals shall be observed. Page 133 of 166 60 18.5.5 The jack-up’s overall elevating speed, inclusive of time taken to recycle jacks, shall be suffi cient to manage the planned positioning and removal operations, having due regard for the tidal range and the rate of tidal rise or fall. Special consideration for operations at locations with large tidal ranges and locations where the duration of slack water may limit the time available for changing from the fl oating to the elevated mode may be required. 18.5.6 Preloading shall be carried out to ensure that each leg is subjected to the load specifi ed in the operating manual or in the site-specifi c assessment. The preloading operation should be carried out with the hull levelled at the lowest practicable air gap. 18.5.7 In circumstances where risk of rapid leg settlement exists during preloading the level of the hull should be set, as far as practicable, at zero airgap or with the hull partially buoyant before achieving footing loads that are likely to result in rapid settlement. Operations of this type require careful planning; the rise and fall of the tide must be taken into account and the operation can only be conducted in calm weather. 18.5.8 Complex preloading or predriving operations involving leg jetting or other special measures designed to achieve the safe installation of a jack-up at locations where risk of punch-through or other foundation hazards exist should not be attempted without expert geotechnical advice. 18.5.9 Particular attention shall be paid to accurate measurement of actual leg penetrations and associated footing loads during installation so as to monitor progress against the predicted load/penetration curve. Any signifi cant diff erence between the predicted leg penetrations and the actual progress of the penetration during preloading should be investigated and reported to a competent person for review and approval prior to elevating the jack-up to the working air gap. 18.5.10 Following the preloading operation and before elevating the jack-up to a working air gap, the individual leg height readings and leg footing penetrations shall be accurately recorded (Appendix H). Leg height and penetration measurements obtained from mechanical or electronic instruments should be verifi ed by visual inspection of the leg height marks against a reference point at the level of the deck or jack-house. 18.5.11 Following completion of the preloading any signifi cant diff erence between the penetrations of each leg and/or any signifi cant diff erence between the penetration anticipated and the penetration achieved should be investigated and reported to the competent person responsible for the site-specifi c assessment for review and approval prior to elevating the jack-up to the working air gap. 18.6 Deployment of jack-ups for soil investigations 18.6.1 In virgin territory, where there has been no previously recorded jack-up activity and where there is no adequate advance information on the nature of the seabed soils, the ground investigation may be carried out using equipment deployed from a jack-up operating in weather restricted mode. 18.6.2 Compliance with the recommendations contained in this section 18.6 does not relieve the jack-up operator of his responsibility for obtaining, as far as reasonably practicable, any available information on the probable characteristics of the soils likely to be encountered before the jack-up is deployed. Particular reference is requested to the HSE information sheet - jack-up (self elevating) installations: review and location approval using desktop risk assessments in lieu of undertaking site soils borings. Page 134 of 166 61 18.6.3 In the absence of reliable advance soil data the jack-up operator must exercise extreme caution during preloading or predriving and the jack-up should remain with the hull partly buoyant or elevated to the lowest practical air gap so that it can be refl oated quickly should the investigation and analysis reveal that the foundation is unsuitable or if rapid settlement occurs. 18.6.4 A jack-up should not be elevated above the lowest practical working air gap or to the survival air gap on any location until the soil investigation and the geotechnical assessment has progressed to the point where the level of confi dence in the integrity of the jack-up foundation has been formally declared satisfactory by a Competent Person. It should be recognised that on-site soil investigation alone may prove inadequate and that the results of on-shore laboratory analysis of samples may be needed before this level of confi dence is achieved. 18.6.5 The lack of adequate advance soil data means that the risk of encountering unsuitable foundation conditions cannot be reduced to a level that is as low as reasonably practicable until the soils investigation and analysis is complete. Therefore soils investigations undertaken from permanently manned jack-ups should only be attempted with towing vessel(s) in attendance and in periods of benign weather that will allow the jack-up to be refl oated and moved to shelter or an alternative safe elevated location at any time. 18.6.6 For unmanned jack-ups, where the crew are routinely accommodated on shore between shifts, the requirement to remove the jack-up before conditions for jacking and refl oating are exceeded can be waived if the following conditions are complied with: • It has been established by a competent person through review of the desk top study and/or the progress of the soils investigation that the risk of encountering unsuitable foundation conditions is low. • A repeated preload operation has exposed no problems and leg penetrations are approximately even. • The jack-up is capable of withstanding the 10 year storm (foundation bearing capacity assumed to be adequate) and the hull is raised to comply with the 50 year air gap requirement. • Site-specifi c weather forecasts stating a high level of confi dence are being monitored and all personnel are removed from the jack-up prior to the onset of weather conditions predicted to exceed the limit for safe disembarkation. • There is no risk to personnel and the consequences of catastrophic weather damage to the jack-up and the potential threat to the environment and to shipping, installations, and property in the vicinity have been formally assessed by the site developer and the jack-up owner. 18.7 Elevated operations 18.7.1 Elevated operations shall not begin until preloading has been completed and the unit has been elevated to the working air gap in accordance with the provisions of section 18.5 of this guideline. 18.7.2 Receipt and review of weather forecasts (section 18.3) shall be continued throughout the period elevated on location. 18.7.3 The progress of elevated operations shall be closely monitored to ensure that weather conditions do not exceed the prescribed limits and to ensure that there is adequate time remaining to implement contingency plans for removal of the jack-up or for placing the unit in the elevated survival mode before the onset of adverse weather, as applicable. 18.7.4 The elevated load condition shall be calculated and any changes in weight attributable to material loaded, discharged or consumed shall be recorded in such a manner that the individual leg loads for all stages of the elevated operation are known. Page 135 of 166 62 18.7.5 Hull inclination shall be monitored on a frequent and regular basis. For units elevated by means of hydraulic jacks, the jack pressures shall be monitored on a frequent and regular basis. In the event that any inclination or loss of jack pressure is observed the elevated operations should be suspended until the cause of the inclination or loss of pressure has been investigated and the condition has been rectifi ed. 18.7.6 Consideration shall be given to the potential impact of seabed scour on the integrity of the jack-up foundation over time. Particular consideration shall be given to the potential for movement of seabed soils caused by currents or waves. Where risk of such conditions is deemed to exist, the jack-up foundation analysis shall include an assessment of the level of change that may aff ect foundation stability. The integrity of the foundation is to be tested by repeating the preload operation following a storm or other event that may have adversely aff ected the strength of the soil supporting the jack-up. 18.7.7 At locations where potential for seabed scour exists, an increase in leg penetration, inclination and/or loss of hydraulic jack pressure (for units elevated by means of hydraulic jacks) may occur. Scour eff ect may create a requirement for frequent operation of the jacking system as adjustments to leg heights become necessary to maintain elevated stability. In such cases a suitable ‘bedding-in’ period must be allowed for and elevated operations should not be attempted until the leg penetration has reached a depth at which the rate of additional penetration caused by scour has reduced to a manageable level. 18.7.8 If any unexpected increase in leg penetration or inclination occurs during elevated operations then all operations should be suspended immediately and expert geotechnical advice should be obtained. Jacking of the unit should only be undertaken after consultation with experts. Subject to the provision of expert advice the hull may be lowered to the lowest practical air gap until the cause of the settlement has been investigated and rectifi ed. After the jack-up has been stabilised the preload operation must be repeated. 18.7.9 Seafastenings for cargo (particularly modules subject to high wind loads) should not be removed until lift rigging is connected and lifting operations are ready to proceed. 18.7.10 Prior to heavy lift operations, the elevated load condition of the unit should be checked by calculation and, for units elevated by means of hydraulic jacks, by equalising the jack pressures. In all cases it shall be verifi ed that the heavy lift operation will not cause allowable leg loads or the centre of gravity off set limits to be exceeded at any point during the proposed lift. Page 136 of 166 63 19. Emergencies and contingencies 19.1 Life saving appliances, fi refi ghting appliances and radio installations 19.1.1 Jack-ups shall be fi tted with life saving and fi refi ghting appliances and radio installations in accordance with their registry, class and certifi cation. Typically, the following standards will be applied as appropriate. • IMO MODU code for the construction and equipment of mobile off shore drilling units, consolidated edition, 2001 • IMO Safety of Life at Sea (SOLAS, 1974) • MCA Small Commercial Vessel and Pilot Boat (SCV) Code (see MGN 280) 19.1.2 Whether required by statutory regulation or otherwise, permanently manned jack-ups fi tted with certifi ed crew accommodation including modular accommodation that is occupied by project personnel or visitors shall, as far as practicable, be fi tted with survival craft and means of evacuation and escape complying with the IMO MODU code, chapter 10. 19.1.3 In the case of a jack-up where, due to its size or confi guration, lifeboats and launching arrangements cannot be fi tted, liferafts complying with the requirements of IMO SOLAS 74 regulation III/39 or III/40 served by launching devices complying with the requirements of regulation III/48.5 or III/48.6 shall be fi tted and these shall be of such aggregate capacity as will accommodate the total number of persons on board if: • All of the liferafts in any one location are lost or rendered unusable • All of the liferafts on any one side, any one end, or any one corner of the unit are lost or rendered unusable 19.1.4 If two widely separated fi xed steel ladders extending from the deck to the waterline when the unit is elevated cannot be installed then alternative means of escape with suffi cient capacity to permit all persons on board to descend safely to the waterline shall be provided. 19.2 Emergency procedures, training and drills Whether required by statutory regulation or otherwise, all jack-ups fi tted with permanent crew accommodation and/or modular accommodation that is occupied by project personnel or visitors shall comply with the provisions contained in the IMO MODU code with respect to the following. Chapters and section numbers refer to numbering in the MODU code. • Emergency Procedures (chapter 14, section 14.8) • Emergency Instructions (chapter 14, section 14.9) • Training Manuals (chapter 14, section 14.10) • Practice Musters and Drills (chapter 14, section 14.11) • Onboard training and instructions (chapter 14, section 14.12) • Records (chapter 14, section 14.13) 19.3 Site-specifi c emergency response plan 19.3.1 Site-specifi c emergency response plans shall be developed for jack-ups operating on site. Emergency response plans are likely to involve local emergency services such as the coastguard, RNLI, fi re, police, ambulance, harbour master and local towage, salvage and pollution response services. Contact should be made with these services to co-ordinate plans prior to mobilising the jack-up. Following mobilisation, joint exercises should be conducted if practicable. 19.3.2 Guidance can be found in the MCA MGN 371 ‘Off shore Renewable Energy Installations (OREIs) Guidance on UK Navigational Practice, Safety and Emergency Response Issues’ and the supporting note ‘Off shore Renewable Energy Installations Emergency Response Cooperation Plans (ERCoP) for SAR Helicopter Operations’. 19.3.3 Plans should be based on comprehensive risk assessments and should be developed following consultation with local emergency services to cover all foreseeable emergency situations including, but not limited to: Page 137 of 166 64 • Extreme storms • Evacuation and escape • Medical aid and evacuation of individuals • Man overboard • External response to jack-up vessel emergencies (Common perils such as fi re, collision, fl ooding, breaking adrift, settlement etc.) • External response to pollution (In addition to the jack-up’s SOPEP) • Notifi cations, contact details and incident reporting 19.4 Route and site-specifi c contingency plans for transit and positioning Contingency plans specifi c to the proposed transit and positioning operations shall be contained in the procedure document and should include: • Forecast of or unexpected onset of adverse weather ≥ prescribed criteria • Motions afl oat approaching prescribed limits • Failure of or damage to seafastenings and grillage • Deviation to designated safe havens en route • Tug breakdown • Towing equipment failure • Jacking system machinery and/or power failure • Mooring equipment failure • Survey equipment failure • Unexpected installation behaviour (leg penetration not as anticipated) • Pollution response (for units not provided with a SOPEP) • Communications equipment failure • Notifi cations, contact details and incident reporting 19.5 Site-specifi c contingency plans for elevated operations Contingency plans specifi c to the proposed elevated operations shall be contained in the Procedure Documents and should include: • Forecast or unexpected onset of adverse weather ≥ prescribed criteria • Jacking system failure • Main power failure • Settlement of leg footings and/or leg misalignment and binding • Removal of the jack-up to a safe haven • Crane structural or machinery failure with lift suspended • Notifi cations, contact details and incident reporting 19.6 Ship emergency response 19.6.1 Under the provisions of the ISM code, self-propelled jack-ups (as ships) are required to have in place a ship emergency response service contactable on a 24/7 basis through the designated person ashore (DPA). This service may be provided by a company’s competent person (naval architect or specialist) or by an external company. The service is intended to provide the vessel’s master with a swift and eff ective response in the form of practical advice, support and back-up technical services in the event of unexpected incidents such as grounding, collision, fl ooding or explosion. Consideration should be given to the provision of a similar response service for all jack-up operations whether required by statutory regulation or otherwise. Page 138 of 166 65 APPENDIX A References PLEASE CHECK FOR AMENDMENTS, REVISIONS AND LATEST EDITIONS. BWEA BWEA Guidelines for Health and Safety in the Marine Energy Industry, October 2008 Background Information on Jack-Ups Noble Denton Consultants Ltd. The Marine Operations of Self-Elevating Platforms (Jack-up Rigs) (Copyright - Noble Denton: Course off ered by Aberdeen College of Further Education) Oilfi eld Publications Ltd. Oilfi eld Seamanship Series, volume two – Jack-up Moving Bennet & Associates & Off shore Technology Development Inc. Jack-Up Units. A Technical Primer for the Off shore Industry Professional UK Government The Health and Safety at Work Act 1974 The Management of Health and Safety at Work Regulations 1999 The Construction (Design and management) Regulations 2007 (CDM) Provision and Use of Work Equipment Regulations 1998 Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) - HSE - Technical guidance on the safe use of lifting equipment off shore - HSE - Safe use of lifting equipment – Approved Code of Practice and Guidance HSE Information Sheets Jack-up (self elevating) installations: rack phase diff erence http://www.hse.gov.uk/off shore/infosheets/is4-2007.pdf Jack-up (self elevating) installations: fl oating damage stability survivability http://www.hse.gov.uk/off shore/infosheets/is6-2007.pdf Jack-up (self elevating) installations: review and location approval using desk-top risk assessments in lieu of undertaking site soils borings http://www.hse.gov.uk/off shore/infosheets/is3-2008.pdf HSE Information The safe approach, set-up and departure of jack-up rigs to fi xed installations http://www.hse.gov.uk/foi/internalops/hid/spc/spctosd21.htm Guidance on Procedures for the Transfer of Personnel by Carriers. HSE Research Reports - OTO series SNAME 5-5B WSD 0: Comparison with SNAME 5-5A LRFD and the SNAME 5-5A North Sea Annex http://www.hse.gov.uk/research/otopdf/2001/oto01001.pdf Page 139 of 166 66 Self-elevating installations (jack-up units) http://www.hse.gov.uk/research/otohtm/2001/oto01051.htm Stability of jack-ups in transit http://www.hse.gov.uk/research/otopdf/1995/oto95022.pdf HSE RR series Review of the jack-ups: Safety in transit (JSIT) technical working group http://www.hse.gov.uk/research/rrhtm/rr049.htm Guidelines for jack-up rigs with particular reference to foundation stability http://www.hse.gov.uk/research/rrhtm/rr289.htm International Maritime Organisation MODU Code. Code for the construction and equipment of mobile off shore drilling units, consolidated edition, 2001 International Safety Management (ISM) Code 2002 Safety of Life at Sea (SOLAS 1974) International Convention on Loadlines 1966 Preventing Collisions at Sea Regulations COLREGS Standards of Training, Certifi cation and Watchkeeping for Seafarers (STCW) 1978 Prevention of Pollution from Ships MARPOL 1973/78 Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 Incidents by Hazardous and Noxious Substances, 2000 (HNS Protocol) Control of Harmful Anti-fouling Systems on Ships (AFS), 2001 IMO MSC Circ.645, “Guidelines for Vessels with Dynamic Positioning Systems” IMO MSC Circ.738 “Guidelines for Dynamic Positioning System (DP) Operator Training”. Marine and Coastguard Agency MCA Code of Safe Working Practice for Merchant Seaman MCA Small Commercial Vessel and Pilot Boat (SCV) Code (as currently set out in MGN 280) MCA - MGN 371 ‘Off shore Renewable Energy Installations (OREIs) Guidance on UK Navigational Practice, Safety and Emergency Response Issues’ and the supporting note: MCA - ‘Off shore Renewable Energy Installations Emergency Response Cooperation Plans (ERCoP) for SAR Helicopter Operations’. Society of Naval Architects and Marine Engineers Society of Naval Architects and Marine Engineers (SNAME) Technical and Research Bulletin TR5-5A Guidelines for Site Specifi c Assessment of Mobile Jack-up Units Including the Recommended Practice and Commentary International Organisation for Standardisation ISO 19901-1:2005(E) Part 1: MetOcean design and Operating considerations. Page 140 of 166 67 Noble Denton Seabed and Sub-seabed Data for Approvals of Mobile Off shore Units/Mou 0016: 0016/ND Rev 4 - 16 Dec 2008 Self-Elevating Platforms - Guidelines for Elevated Operations 0009: 0009/ND Rev 4 - 16 Dec 2008 Guidelines for Marine Transportations 0030/ND Rev 3 - 15 April 2009 Guidelines for the Approval Of Towing Vessels 0021/ND Rev 7 - 17 Nov 2008 Guidelines for Marine Lifting Operations 0027/ND Rev 7 - 15 April 2009. A further update (to correct a typo) is imminent. London Off shore Consultants LOC Guidelines for Marine Operations – Barge Transportation LOCG-GEN-Guideline 002 Rev. 01 Dated 01/01/2007 LOC Guidelines for Marine Operations – Marine Lifting LOCG-GEN-Guideline 003 Rev. 0 Dated 05/2003 Det Norske Veritas Det Norske Veritas (DNV) Rules for the Planning and Execution of Marine Operations: • Load Transfer Operations (issued 1996) • Towing (issued 1996) • Special Sea Transports (issued 1996) • Off shore Installation (issued 1996) • Lifting (issued 1996) • Sub Sea Operations (issued 1996) • Transit and Positioning of Mobile Off shore Units (issued 2000) Det Norske Veritas (DNV) Classifi cation Notes Section 8: Foundation of Jack-up Platforms Lloyds Register Code for Lifting Appliances in a Marine Environment 2008 UK Off shore Operators Association Guidelines for Safe Movement of Self-Elevating Off shore Installations (Jack-ups) UK Off shore Operators Association. April 1995 issue No.1 North Sea Lifting (NSL) Suitability of Cranes for Man Riding Page 141 of 166 68 Air gap Vertical distance between the bottom of the rig hull and the water surface. Air gap related to LAT Vertical distance between the bottom of the hull and the level of LAT. Centroid of the legs Point on a three-legged jack-up that is horizontally equidistant from each leg centre. Certifi ed accommodation Permanent or temporary certifi ed crew accommodation comprising sleeping cabins with sanitary facilities, galley, mess room and recreation spaces intended for occupation by the crew and project workers. This specifi cally excludes temporary or permanent containerised or modular units installed on the jack-up to provide limited shelter, feeding and sanitary facilities for personnel that are not routinely accommodated on board. Chart datum The datum to which the soundings (water depths) are reduced on the location bathymetric chart and to which must be added the tidal height to obtain the actual depth of water at any point in time. Class notation Series of symbols, letters and numbers assigned by the classifi cation society to indicate the details of the class assigned to the vessel (For example: “ABS Self Elevating ✠A1”, Lloyds ✠100A1 etc.). Competent person A person having suitable and suffi cient experience in the fi elds that they work in, to understand the hazards and risks involved with the work, the operating environment, and the type of people they need to work with; and having suffi cient training to be able to communicate the results of their assessment to all the people necessary (in writing if necessary) in a clear and comprehensible manner. The Management of Health and Safety at Work Regulations 1999, requires every employer to appoint one or more competent persons to assist with putting measures in place to ensure legal compliance. The competent person can be either an individual or a company providing these services. The person is regarded as competent if they have suffi cient training and experience or knowledge and other qualities to properly assist the employer to meet his safety obligations. A competent person is likely to be a corporate body rather than an individual because of the necessary requirement to have access to a wide variety of technical expertise and specialist services. One indication of competence is accreditation and certifi cation. Contingency plan: Pre-considered response to a deviation from an intended course of action. Dynamic amplifi cation factor The factor by which the ‘gross weight’ is multiplied, to account for accelerations and impacts during the lifting operation. APPENDIX B Glossary, terms and defi nitions Page 142 of 166 69 Elevated operation Jack-up marine operation conducted after the unit has been jacked, preloaded and elevated to a working air gap. Extreme wave crest elevation The maximum elevation of the storm wave crest above LAT for the return period specifi ed. Field move A jack-up move undertaken in the vicinity of a work site which can be completed within the period covered by a single reliable weather forecast (commonly 12 – 24 hours). Flag state Nation operating a registry of vessels in which the jack-up has a valid listing. Freeboard The vertical height of the assigned deck line above the vessel’s waterline. Gog line (or rope) System used for the control of the towline to reduce the risk of girding. Commonly a line led from a winch drum or fi xed connection through a deck fi tting aft of the towing winch and connected to the towing wire so as to control the point at which any transverse load imposed by the towline angle acts upon the towing vessel. Grillage: The temporary structural members that support the module and distribute the vertical static and dynamic loads over the barge or vessel framing. Gross Weight The calculated or weighed weight of the structure to be lifted including a reserve factor. Harbour Move Jack-up move conducted within port limits. Hook Load The hook load is the ‘lift weight’ plus the ‘rigging weight including dynamic factor’. Jack Frame Jack-up vessel structure at each leg containing the jacking system (also called the “jack house”). Jacking Operation of the jacking system Jacking down Lowering the rig hull when in the elevated mode Jacking up Elevating the rig hull when in the elevated mode Jacking legs down Jacking the rig hull up Jacking hull down Jacking the legs up. Raising legs Jacking legs up when in the fl oating mode Lowering legs Jacking legs down when in the fl oating mode Jack-up Ship or barge fi tted with legs and jacking machinery providing the capability to self-elevate the vessel above the sea surface. Leg bind or leg binding Excessive friction between the leg chords and leg guide usually caused by the rig being out of level and/or by the legs being bent or inclined. Leg braces Horizontal or diagonal tubular members of the leg structure connecting the leg chords. Page 143 of 166 70 Leg chords Vertical tubular members of the leg structure of braced type legs. Leg footing penetration curve Graphic representation based on geotechnical analysis showing the predicted leg footing load versus the depth of leg penetration. Leg footing reaction Equal to the portion of the jack-up’s elevated weight including environmental loads imposed on any one leg plus the leg and footing weight minus the leg buoyancy. Leg load Portion of the jack-up’s elevated weight including environmental loads supported by a particular leg. Location move Jack-up move not falling into the defi nition of an ocean tow or a fi eld move and generally undertaken with the unit in fi eld move confi guration as a weather restricted operation within the period of a reliable weather forecast. Location approval Certifi cate and report providing location details and certifying warranty approval for installation of a rig on a specifi c location. Location move A move between two locations which cannot be completed within the period covered by a single forecast but which can safely be undertaken with the unit in fi eld move confi guration, having due regard for the availability of standby locations or shelter points en route. Marine warranty surveyor Marine surveyor assigned to review procedures and to attend marine operations commonly to satisfy an insurance warranty clause that states that the operation shall be approved by and conducted in accordance with the recommendations issued by a named warranty surveyor. Medivac Evacuation of a sick or injured person. Met-ocean study Meteorological study of a specifi c area carried out to determine the probable range of environmental conditions for specifi c return periods. Minimum breaking load The minimum allowable value of ‘breaking load’ for a particular lifting operation. Mobile off shore unit For the purposes of this document, the term includes non-drilling mobile jack-up vessels such as accommodation, construction, and lifting barges. MODU code Code for the construction and equipment of mobile off shore drilling units, consolidated edition 2001. Module A unit of cargo such as a jacket, integrated deck, topside components, pre-assembled units, items of equipment or parts thereof. Net weight The calculated or weighed weight of a structure, with no contingency or weighing allowance. Page 144 of 166 71 Nomograms Graphic representation indicating the jack-up’s capacity to withstand defi ned environmental conditions in a range of water depths and with a range of leg penetrations. Permanently manned jack-up Jack-up permanently manned by the crew (and project workers if applicable) where some or all personnel, both on-shift and off -shift, are accommodated on board and are not routinely transported to and from the shore at each shift change. Positioning ( jack-up) Jack-up marine operation commencing from the time of arrival at a new location and continuing until the unit has completed jacking, preloading and elevating to the working air gap on a new elevated location or until the unit is safely moored afl oat at a new location. Preloading Preloading is the process by which the jack-up rig’s legs are loaded so as to drive them into the seabed soil. The preloading process simulates the expected maximum loads that may be imposed on the seabed and thus the strength of the seabed soil foundation is proof tested in excess of the capacity required to support the rig when it is working or when it is idle in the storm survival mode. The object of preloading is to achieve suffi cient capacity to withstand the combination of vertical and horizontal reactions, the applied preload (generally) has to be greater than the storm vertical reaction. When using SNAME, as required in this document, the vertical and horizontal reactions include the eff ects of the partial load factor and the permitted capacity is reduced by the application of the SNAME resistance factor. Punch-through Punch-through is a generic term often loosely applied to an event whenever signifi cant vertical footing settlement is observed over a relatively short period of time. During these events diff erential footing penetrations usually occur which may dramatically aff ect the stability of the jack-up. Punch-through can result in structural failure and even total loss. Rack chocks Leg fi xation device engaged to form a strong connection between the rig hull and legs for units fi tted with rack and pinion jacking systems Rack phase diff erence Diff erence in vertical height between individual chords on one leg on units with braced type leg structures Recognised classifi cation A Vessel classifi cation society with established rules and procedures for the classifi cation, survey and certifi cation of vessels used in off shore construction activities Recognised maritime nation A nation with maritime laws that maintains a registry of ships and that has adopted the IMO conventions listed in section 2.6. Recommended practice SNAME TR5-5A: the Recommended Practice for Site-Specifi c Assessment of Mobile Jack-up Units Rev, 2 January 2002. Refl ected waves Wind or swell generated waves that have been refl ected through direct impact with obstructions such as cliff s or breakwaters society (RCS) Page 145 of 166 72 Refracted waves Wind or swell generated waves that have been infl uenced in direction by the geophysical characteristics of the coastline or seabed Riding crew Marine crew assigned to an unmanned barge during a tow Rig mover Person appointed to be in charge of the planning and execution of the jack-up move Seafastenings: Shall in general mean the temporary structures or tie-downs that secure the Module for transportation and berthing forces. Settlement The settlement of jack-up leg footings into the seabed soil Slow settlement: Leg settlement where the rate at which one or more legs is penetrating is less than the rate at which the hull can be maintained in a level condition by lowering the hull on the other legs. Rapid settlement: Rapid uncontrolled leg settlement where the rate at which one or more leg is penetrating exceeds the rate at which the hull can be maintained in a level condition by lowering the hull on the other legs. Slight settlement: Leg settlement where the resulting inclination is less than one degree. Signifi cant settlement: Leg settlement where the resulting inclination is more than one degree. Signifi cant wave height H = the average of the highest one-third of all waves. Site-specifi c assessment Assessment of the site soil foundation and the structural capacity of a jack-up to withstand the loads associated with the geophysical and extreme environmental conditions for a specifi c location. Spudcan Very robust tank-like structure attached to the bottom of a jack-up rig’s leg and forming the leg footing. Squat Temporary increase in vessel’s hull draft caused by change of trim when proceeding in shallow water above a certain speed. Survival mode Elevated condition achieved by the jack-up when it is capable of remaining on location in extreme storm conditions with all stresses remaining within allowable limits in accordance with the RP. Tidal window Period during a tidal cycle where the tidal height provides adequate depth of water and/or current velocity not exceeding a prescribed value for a particular operation. Tow master Person usually holding a Marine Certifi cate of Competency assigned to control the towage, navigation and positioning of the Rig afl oat Page 146 of 166 73 Transit ( jack-up) Jack-up marine operation commencing from the moment when lowering of the hull commences on departure from an elevated location or when the last mooring line is recovered on departure from a location afl oat and continuing until arrival in the vicinity of a new location. Tug management system DGPS navigation survey system and telemetry that allows the positions of tugs, anchors and mooring lines to be displayed in real time on remote monitors. Unaccounted weight Portion of the vessel’s total weight that has not been accounted for in the load calculations. The amount is calculated by subtracting the calculated displacement from the actual displacement obtained by reading the hull draft marks with the rig afl oat. Unmanned jack-up A non-propelled jack-up barge that carries no permanent crew accommodated on board and is not fi tted with certifi ed accommodation and where the crew and project workers are routinely transported to and from the shore at the end of each shift. Unrestricted mode A jack-up engaged on an unrestricted operation. Unrestricted operation A marine operation which cannot be completed within the limits of a favourable weather forecast (generally less than 72 hours). The design weather conditions must refl ect the statistical extremes for the area and season. Variable load Portion of the vessel’s elevated weight that is variable, that is, not forming part of the fi xed structure and machinery. This includes fuel, lubricants, fresh water, ballast, drilling materials and equipment, crew and stores. Visitors Personnel on board the unit who do not form a part of the vessel’s crew. Weather restricted operation A marine operation which can be completed within the limits of a favourable weather forecast (generally less than 72 hours), taking contingencies into account. The design weather conditions need not refl ect the statistical extremes for the area and season. A suitable factor should be applied between the design weather conditions and the operational weather limits. Weather window Forecast period of generally benign weather with wind and waves not exceeding prescribed the limits for a particular operation. Page 147 of 166 74 ABREVIATIONS AISC American Institute of Structural Steel ALARP As low as reasonably practicable (with reference to risk reduction) BL Breaking load BP Bollard pull CCTV Closed Circuit Television CDM (Regulations) Construction Design and Management regulations CPT Cone penetrometer test DAF Dynamic Amplifi cation Factor applied to lifted weights to account for the dynamic motion of vessels in marine lifting operations DGPS Diff erential Global Positioning System DP Dynamic positioning ECDIS Electronic Chart Display and Information System EEZ Exclusive economic zone GMDSS Global Maritime Distress and Safety System HAT Highest astronomical tide Hs Signifi cant wave height IACS International Association of Class Societies IAPP International Air Pollution Prevention IMO International Maritime Organisation IOPP International Oil Pollution Prevention ISM International Safety Management (ISM Code) ISPS International Ship and Port Security L.A.T. Lowest astronomical tide LRFD Load resistance factor design MCA Marine and Coastguard Agency (UK) MDW Module design weight MIN Marine information notices MSN Merchant shipping notices MGN Marine guidance notices MOC Management of change MODU Mobile off shore drilling unit MOU Mobile off shore unit MSL Mean sea level MTC Site-specifi c (non-governmental) marine traffi c control OIM Off shore installation manager. The person in charge of the jack-up Page 148 of 166 75 PPE Personal protective equipment PUWER Provision and use of Work Equipment Regulations 1998 RCS Recognised classifi cation society RNLI Royal National Lifeboat Institution RW Rigging weight for lifting operations SCV Small Commercial Vessel Code (Awaiting publication) SF Shear force SHL Static hook load SOPEP Shipboard oil pollution emergency plan STCW 95 Standards of Training and Certifi cation of Watchkeepers 1995 SWBM Still water bending moment TPR Towline pull required WGS 84 World Geophysical Survey 1984 WLL Working load limit (Same as SWL: safe working load) Page 149 of 166 76 APPENDIX C Certifi cates, Manuals, Publications, Logs and Records Ref. Registry Flag state inspection report or MCA inspection ISM Certifi cate and document of compliance Minimum Safe Manning Certifi cate Builders Certifi cate International Tonnage Certifi cate International Loadline Certifi cate (or exemption) Annual Loadline Survey Report/Endorsement Certifi cate of Class (+Annual endorsement) Safety Construction Certifi cate MOU Certifi cate or Safety Equipment Certifi cate or: Safety Equipment – Class Statement of Facts IOPP Certifi cate IAPP Certifi cate ISPS Certifi cate Safety Radio Certifi cate Radio License (GMDSS) Radio Certifi cate of Shore Based Maintenance Fast Rescue Craft Certifi cate Lifeboats (Rigid Survival Craft) Certifi cates Lifeboats davits and launching gear Certifi cates Infl atable Liferaft Service Certifi cates Liferaft Launching Davit Certifi cates (if fi tted) Fixed Firefi ghting Appliances Certifi cate Portable Firefi ghting Appliances Certifi cate Crane Test Certifi cate Lifting Appliances Register - Annual inspection & Quadrennial Test Sewage Plant Certifi cate Garbage Management Certifi cate Medical Drugs Certifi ed Inventory Deratisation or Deratisation exemption Cert. ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✗ ✓ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✗ ✗ ✗ ✓ ✓ ✗ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ Certifi cate CERTIFICATES REQUIRED Self-prop. jack-up ships Permanently manned and/or classed jack-ups Unmanned jack-ups with no classifi cation Page 150 of 166 77 Emergency station bills posted Safety equipment Plans posted Safety equipment signs posted Evacuation and escape route signs posted Emergency muster points marked Survival craft launching instructions posted Lifejacket donning instructions posted Health, safety & environmental policy Drug and alcohol policy Record of emergency drills Safety manual PPE signs posted Accident/incident reports Near miss reports Hazard identifi cation/observation reports Risk assessments conducted/recorded Safety meetings conducted/recorded Tool box talks conducted/recorded Permits to work posted Visitors safety briefi ng record Tag card system Ship security plan Gangway crew/visitors log Medical log Plans, manuals and reports Operating company QA system Company instructions/procedures Ship safety management system manuals Non-conformance & corrective action Vessel operating manual General arrangement plan / capacity plan Crew training manuals / records Approved stability book Stability plan for current voyage/operation SOPEP manual Garbage management plan Engine room & machinery Engine log Bunker check lists Oil Record Book / waste oil disposal Machinery operation & maint. manuals IMO SOLAS (1986 consolidated) IMO load line regulations (1986/81) IMO MERSAR manual IMO ship routeing IMO standard marine navigation vocabulary IMO Collision Regulations (1990) IMO bridge procedures guide IMO Annex I: to MARPOL 73/78 (Oil) IMO Annex II: to MARPOL 73/78 (Noxious Subst.) IMO Annex III: Pollution by Harmful Substances IMO Annex IV: Pollution by Sewage from Ships IMO Annex V to MARPOL 73/78 (Garbage) IMO IMDG code (consolidated supplement) IMO ISPS code MCA Code of Safe Working Practice Bridge / Navigation Publications Navigation charts Chart correction log Pilot books & supplements Guide to port entry List of lights Admiralty list of radio signals (volumes 1 - 6) International Code of Signals (1987) Notices to mariners Flag state marine notices and guidance notes Tide tables Tidal current tables/charts Nautical almanac Navigation tables RPM/Speed data Manoeuvring data Deck log book Rough log Radio log Night order book Passage plans Master/pilot exchange form Vessel check lists [arrival, departure] Operations check lists (jacking) Operations check lists (DP – if DP vessel) Equipment operation and maintenance manuals Complete set of drawings Safety and security A = Self-propelled jack-up ships B = Permanently manned and/or classed jack-up barges C = Unmanned and non-classed jack-up barges A ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✓ ✗ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✓ ✗ ✓ ✓ ✗ ✗ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✓ ✓ B C IMO and other Publications A B C Page 151 of 166 78 Operating manuals containing guidance for the safe operation of the unit should be provided on board and be readily available to all concerned. The manual should, in addition to providing the necessary general information about the unit, contain guidance on and the procedures for the operations that are vital to the safety of personnel and the unit. The manual should be concise and be compiled in such a manner that it is easily understood. The manual should be provided with a contents list, an index and wherever possible be cross-referenced to additional detailed information in the form of drawings, manufacturer’s manuals and other readily available information for the safe and effi cient operation of the unit. Detailed information contained in manufacturer’s manuals (such as the Jacking System Manual) need not be repeated in the operating manual. The operating manual should include the following information. 1. Description, particulars and principal dimensions. 2. Organisation and responsibilities. 3. General arrangement plan and capacity plan showing the location and centres of gravity of all tanks and stowage spaces. 4. Plan showing the location of watertight and weather tight boundaries, the location and type of all watertight and weather tight closures, and the location of down fl ooding points. 5. Limiting design data for the fl oating mode and the elevated mode. 6. Operational limits and procedures and guidance for the transition between the fl oating mode and the elevated operating mode and between the operating mode and the elevated survival mode. 7. Information and guidance on the preparation of the unit to avoid structural damage afl oat and during the setting or retraction of the legs on or from the seabed. 8. Information and guidance on jacking and preloading. 9. Information and guidance on the preparation of the unit to withstand the extreme environmental limits associated with the limiting design data for the elevated mode described in (5) above. 10. Lightship data together with a list of inclusions and exclusions of semi-permanent equipment and guidance for the recording of light weight changes together with weight data and centre of gravity off set limits including: Lightweight Weight of movable items (cranes, pile gates/grippers etc) Weight of legs and leg footings Maximum allowable variable load afl oat, jacking, preloading, operating and survival Maximum allowable displacement afl oat APPENDIX D Jack-up operating manual (recommended contents) Page 152 of 166 79 Maximum allowable elevated weight and maximum leg load for jacking Maximum allowable elevated weight and centre of gravity limits for preloading Maximum allowable elevated weight and centre of gravity limits for elevated operations Maximum allowable elevated weight and centre of gravity limits for survival 11. Tank sounding tables showing capacities, vertical, longitudinal and transverse centres of gravity in graduated intervals and free surface data for each tank. 12. Stability information including hull hydrostatic properties and GZ curves. 13. Allowable vertical centre of gravity curve. 14. Sample stability and trim calculations and guidance for maintaining stability afl oat. 15. Sample elevated load calculations and guidance for maintaining leg loads within design limits including leg load limits and/ or centre of gravity limits for lifting operations. 16. Acceptable structural deck loads. 17. A plan and description of the towing arrangements for non-propelled vessels together with guidance on safe towing operations. 18. A description, schematic diagram and guidance for the operation of the bilge and ballast system (if fi tted), together with a description of its limitations such as draining of spaces not directly connected to the systems. 19. Fuel oil storage and transfer procedures. 20. Description and capacity of main and emergency power systems. 21. Personnel transfer procedures. 22. Limiting conditions for crane operations. 23. Guidance on damage control for incidents of fl ooding and unexpected settlement. Page 153 of 166 80 APPENDIX E Typical spot location reports Page 154 of 166 81 APPENDIX F Foundation Risks: Methods for Evaluation and Prevention RISK Installation problems Punch-through Settlement/bearing failure Sliding failure Scour Geohazards (mudslides, mud volcanoes etc) Gas pockets/shallow gas Leg extraction diffi culties Eccentric spudcan reactions Seabed slope Footprints of previous jack ups Faults Metal or other object, sunken wreck, anchors, pipelines etc. Local holes (depressions) in seabed, reefs, pinnacle rocks, non-metallic structures or wooden wreck Bathymetric survey Sea fl oor survey Geophysical survey Soil sampling and other geotechnical testing and analysis Geophysical survey Soil sampling and other geotechnical testing and analysis Ensure adequate jack up preload capability Geophysical survey Soil sampling and other geotechnical testing and analysis Increase vertical spudcan reaction Modify the spudcans Bathymetric and sea fl oor survey (identify sand waves) Surface soil samples and seabed currents Inspect spudcan foundation regularly Install scour protection (gravel bag/artifi cial seaweed) when anticipated Sea fl oor survey Geophysical survey Soil sampling and other geotechnical testing and analysis Geophysical survey Geophysical survey Magnetometer and sea fl oor survey Sea fl oor survey Diver/ROV inspection Soil sampling and other geotechnical testing and analysis Consider change in spudcans Jetting/airlifting Geophysical survey Geophysical survey (buried channels or footprints) Soil sampling and other geotechnical testing and analysis Seabed modifi cation Geophysical survey Seabed modifi cation Evaluate site records Prescribed installation procedures Consider fi lling/modifi cation of holes as necessary METHODS FOR EVALUATION & PREVENTION Page 155 of 166 82 Source: Adapted from recommended practice for the site-specifi c assessment of mobile jack-up units, rev 2 APPENDIX G Flowchart for Jack-up Site Assessment Overall fl owchart for the assessment Page 156 of 166 83 APPENDIX H Leg Penetration Check and Air Gap Calculation Level the hull at zero air gap immediately after preloading to check the individual leg penetrations and to defi ne the level of the hull above LAT Leg number Leg height mark at top of jack frame - Jack frame height above hull baseline = Leg below hull - Height of tide - Water depth at LAT = Leg penetration 1 2 3 4 5 6 Page 157 of 166 84 MINIMUM (SURVIVAL) HULL ELEVATION A or B whichever is greatest A) LAT + HAT + surge + wave crest elevation + 1.5m B) To clear the 10,000 year return period wave crest APPENDIX H continued Page 158 of 166 85 APPENDIX I Checklist for jack-Up suitability Assessment Note: This checklist is presently comprised of approximately 60 questions which are intended to provide an outline assessment of a jack-up’s suitability for a proposed operation. Negative or uncertain responses to checklist items suggest issues that may require clarifi cation and/or a more detailed independent assessment by consultants with experience of jack-up operations. Ref 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Management and manning Is the owner or operator (the contractor) an established marine contractor with experience of the management and operation of type of jack-up vessels commonly deployed for the type of work required? Does the contractor a) employ civil or structural engineers capable of carrying out jack-up related analyses associated with structural capacity, site-specifi c assessments, vessel motion response and seafastening design, and heavy lifts, or b) routinely engage third party engineering services to undertake the required analyses? Does the contractor a) employ a geotechnical engineer capable of performing soils assessments for jack-up site-specifi c assessments, or b) routinely engage recognised soils experts to undertake the required assessments? Does the contractor employ a competent person having the requisite qualifi cations, skills and experience to conduct a jack-up site-specifi c assessment and/or to verify that the site-assessment has been conducted in accordance with the recommended practice? If not, are recognised marine consultants with experience of jack-up operations routinely engaged to conduct or to verify the assessments? Does the contractor a) employ master mariners and/or marine engineers for planning and preparation, production of procedure documents, and execution of jack-up operations, or b) routinely engage third party services to undertake these tasks? Is the contractor capable of planning jack-up operations in accordance with the provisions described in section 4 of this guideline? Does the contractor understand the regulatory requirements and guidelines for the operation of jack-ups in UK waters as described in section 2 of this guideline? Is the jack-up manned in accordance with section 3 of this guideline? JACK-UP SUITIBILITY ASSESSMENT check 2 2.1 2.2 2.3 2.4 Off shore jack-ups with accommodation - unrestricted operations Is the jack-up entered on a vessel registry of a recognised maritime nation (the fl ag state)? Have outstanding fl ag state recommendations (if any) been cleared? Is the jack-up vessel classed in accordance with the rules of a recognised classifi cation society and a member of the International Association of Class Societies (IACS)? Does the class notation a) Include the term “self-elevating” or b) otherwise defi nitively cover the design, construction and survey of the unit’s capacity for safe elevation? (Some classifi cations relate solely to the design as a fl oating vessel). Does the class status report (and/or the class certifi cates) confi rm that the jack-up is currently class maintained? Have all outstanding class recommendations, defects or defi ciencies that may have an impact on the proposed operations been rectifi ed or complied with? Are the certifi cates and documentation in accordance with this guideline Appendix C? Is the jack-up provided with a class approved operating manual? check 2.5 2.6 2.7 2.8 Page 159 of 166 86 3 4 3.1 4.1 3.2 4.2 3.3 4.3 3.4 4.4 3.5 4.5 3.6 4.6 3.7 4.7 4.8 4.9 4.10 Small unmanned inshore jack-ups – weather restricted operation Suitability of the jack-up for transit to site: Is the jack-up entered on a small vessel registry of a recognised maritime Nation (the fl ag State)? Have any outstanding fl ag state recommendations been cleared? Has the unit’s design limits for fl oating and elevated operations been clearly stated by the vessel manufacturer in a design report or the operating manual? Has the design report or operating manual been verifi ed by an independent authority? If the jack-up is not classed or not covered under MCA MGN-280, is there an independent survey report confi rming that the unit is in satisfactory condition with no outstanding defects or defi ciencies? Are the certifi cates and documentation in accordance with this guideline Appendix C? Is the jack-up provided with an operating manual and does the operating manual include the information suggested in Appendix D? If the proposed work site is in coastal waters or an off shore area, is the jack-up designed and certifi ed for transit afl oat on its own hull beyond port limits? Does the vessel’s certifi ed trading area include the whole of the proposed transit route and the operating site? Has the limiting sea state for transit afl oat been defi ned? Will the limiting sea state for operations afl oat unreasonably restrict the jack-up’s capability to undertake the transit effi ciently in the predicted seasonal conditions? If project cargo and equipment is to be transported on the deck of the jack-up, can the total displacement (including variable load plus deck load) and the trim and the allowable VCG be maintained within the allowable limits for the fl oating condition? Does the jack-up meet the intact and damage stability requirements for the loaded condition as described in this guideline section 6? In the loaded condition, is the total elevated weight and the centre of gravity within the allowable limits for the a) Jacking mode? b) Elevated operating mode (including lifting operations) and c) elevated survival mode? If project cargo and equipment is to be transported on the deck of the jack-up, will the grillage and seafastening arrangements meet the requirements described in section 7 of this guideline? If project cargo and equipment is to be transported on the deck of the jack-up, can the cranes be stowed and seafastened with the booms lowered in the cradles. If the jack-up is self-propelled and/or fi tted with a dynamic positioning system, does the unit comply with the provisions of this guideline section 11? check check 4.11 4.12 If the jack-up is non-propelled or propulsion assisted, is the unit capable of complying with the arrangements as specifi ed in the guideline sections 11 & 12? If the jack-up is non-propelled or propulsion assisted, will it be towed by suitable towing vessels that meet the requirements of this guideline section 13? Page 160 of 166 87 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 Suitability of the jack-up for positioning and elevating Has the site geophysical data been obtained as described in section 8 of this guideline and the survey reports delivered to the contractor? Has the site meteorological data been obtained and delivered to the contractor in the form of a spot location report (Appendix E)? Has a site soil investigation been carried out and the results delivered to the contractor? Has the contractor reviewed the site survey and soil investigation reports and confi rmed that the data received is adequate and suffi cient to complete a site-specifi c assessment for the jack-up in accordance with the recommended practice? Is the jack-up fi tted with a station keeping system (DP or 4-Point Mooring System) in accordance with this guideline Section 14? Can the contractor devise an approach and/or a mooring plan that will allow jack-up be moved into the required position while maintaining the minimum clearances prescribed in this guideline section 14? Are the water depths and tidal levels in the approach to, and on site, suffi cient to allow the jack-up to be moved always afl oat on to the location? In areas where high velocity tidal currents fl ow, is the duration of slack water periods of adequate length to allow safe positioning and subsequent removal of the jack-up? Based upon the information received, is the contractor satisfi ed that there are no signifi cant or unusual marine hazards in the approach to, or on site, that could have an impact on jack-up positioning? Based upon the information received, is the contractor satisfi ed that there are no signifi cant or unusual seabed surface features or soil foundation hazards for jacking and preloading and for subsequent elevated operations? If seabed surface and/or foundation hazard(s) have been identifi ed, is the contractor confi dent that procedures can be developed to safe jacking, preloading and elevated operations? Have the foundation hazard(s) and the proposed procedures been assessed and found suitable by independent geotechnical engineers and jack-up move experts? Based upon the information received, has the contractor determined through site-specifi c assessment that the jack-up is capable of operating on site in a) weather restricted Mode or b) unrestricted Mode? If the jack-up is capable of operating only in weather restricted mode, will this unreasonably restrict the jackup’s capability to operate effi ciently in the elevated mode on site in the expected seasonal conditions? Is the jack-up capable of complying with the arrangements for mooring and positioning on site as described in section 14 of this guideline? check 5.11 5.12 5.13 5.14 5.15 Page 161 of 166 88 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 Suitability of the jack-up for elevated operations Has the contractor fully understood the objectives to be achieved? Are the contractor’s personnel capable of planning and executing the operations necessary to achieve the objectives without engineering assistance from third party services? Is the jack-up a suitable platform for the execution of the operations with respect to size, confi guration, deck height, deck strength, accommodation and facilities? Based upon the site-specifi c assessment, is the jack-up’s leg length suffi cient to allow elevation to the extreme storm survival air gap (see Appendix H) If the leg length is not suffi cient to achieve the survival air gap, is it suffi cient to allow elevation to a working air gap? Based upon the site-specifi c assessment, is the jack-up capable of remaining elevated on location in the seasonal 50 year extreme storm condition with all stresses remaining within allowable limits in accordance with the RP? If the jack-up cannot achieve the minimum survival air gap and/or cannot safely withstand the extreme storm condition, can the proposed elevated operations be completed safely by the jack-up as a weather restricted operation in accordance with this guideline section 5? If the jack-up is operating in Weather Restricted mode, will the operating restrictions that apply and the potential need to often remove the unit to shelter have an unreasonable adverse impact on the proposed works in the seasonal weather considered. If a weather restricted operation is proposed, can the elevated operations be suspended and the jack-up removed to a safe standby location or to shelter within 48 hours? Is the contractor in possession of, and familiar with, at least one of the guideline documents for marine lifting operations listed in this guideline section 15.1.2? Are the crane and the lifting gear capable of performing the proposed lifting operations (if any) in accordance with the specifi ed guidelines and with this guideline section 15? check 6.11 Page 162 of 166 BWEA Greencoat House Francis Street London SW1P 1DH United Kingdom Tel: +44 (0)20 7901 3000 Fax: +44 (0)20 7901 3001 www.bwea.com Page 163 of 166 Appendix I Useful References Olifield Publications Ltd. OilfIeld Seamanship Series, volume two — Jack-up Moving Bennet & Associates & Offshore Technology Development Inc. Jack-Up Units. A Technical Primer for the Offshore Industry Professional UK Government The Health and Safety at Work Act 1974 The Management of Health and Safety at Work Regulations 1999 The Construction (Design and management) Regulations 2007 (CDM) Provision and Use of Work Equipment Regulations 1998 Lifting Operations and Lifting Equipment Regulations 1 998 (LOLER) - HSE - Technical guidance on the safe use of lifting equipment offshore - HSE - Safe use of lifting equipment — Approved Code of Practice and Guidance HSE Information Sheets Jack-up (self elevating) installations: rack phase difference http://www.hse.gov.uk/offshore/infosheets/is4-2007.pdf Jack-up (self elevating) installations: floating damage stability survivability http://www.hse.gov.uk/offshore/infosheets/is6-2007.pdf Jack-up (self elevating) installations: review and location approval using desk-top risk assessments in lieu of undertaking site soils borings http://www.hse.gov.ukloffshore/infosheets/is3-2008.pdf HSE Information The safe approach, set-up and departure of jack-up rigs to fixed installations http://www.hse.gov.uk/foi/internalops/hid/spc/spctosd21.htm Guidance on Procedures for the Transfer of Personnel by Carriers HSE Research Reports - OTO series SNAME 5-5B WSD 0: Comparison with SNAME 5-5A LRFD and the SNAME 5-5A North Sea Annex http://www.hse.gov.uk/research/otopdf/2001/oto01001.pdf Det Norske Veritas Det Norske Veritas (DNV) Rules for the Planning and Execution of Marine Operations: • Load Transfer Operations (issued 1996) • Towing (issued 1996) • Special SeaTransports (issued 1996) • Offshore Installation (issued 1996) • Lifting (issued 1996) • Sub Sea Operations (issued 1996) • Transit and Positioning of Mobile Offshore Units (issued 2000) Det Norske Verftas (DNV) Classification Notes Section 8: Foundation of Jack-up Platforms Page 164 of 166 Lloyds Register Code for Lifting Appliances in a Marine Environment 2008 UK Offshore Operators Association Guidelines for Safe Movement of Self-Elevating Offshore Installations (Jack-ups) UK Offshore Operators Association. April 1995 issue No.1 North Sea Lifting (NSL) Suitability of Cranes for Man Riding Self-elevating installations (jack-up units) http://www.hse.gov.uk/research/otohtm/2001/oto01051.htm Stability of jack-ups in transit http://www.hse.gov.uklresearch/otopdf/1995/oto95022.pdf HSE RR series Review of the jack-ups: Safety in transit (JSIT) technical working group http://www.hse.gov.uk/research/rrhtm/rr049.htm Guidelines for jack-up rigs with particular reference to foundation stability http:/www.hse.gov.uk/research/rrhtm/rr289.htm International Maritime Organisation MODU Code. Code for the construction and equipment of mobile offshore drilling units, consolidated edition, 2001 International Safety Management (ISM) Code 2002 Safety of Life at Sea (SOLAS 1974) International Convention on Loadlines 1966 Preventing Collisions at Sea Regulations COLREGS Standards of Training, Certification and Watchkeeping for Seafarers (STCW) 1978 Prevention of Pollution from Ships MARPOL 1973/78 Prevention of Marine Pollution by Dumping of Wastes and Other Matter I972 Incidents by Hazardous and Noxious Substances, 2000 (HNS Protocol) Control of Harmful Anti-fouling Systems on Ships (AFS), 2001 IMO MSC Circ.645, “Guidelines for Vessels with Dynamic Positioning Systems” IMO MSC Circ.738, “Guidelines for Dynamic Positioning System (OP) Operator Training” Marine and Coastguard Agency MCA Code of Safe Working Practice for Merchant Seaman MCA Small Commercial Vessel and Pilot Boat (SCV) Code (as currently set out in MGN 280) MCA - MGN 371 ‘Offshore Renewable Energy Installations (OREIs) Guidance on UK Navigational Practice, Safety and Emergency Response Issues’ and the supporting note: MCA -‘Offshore Renewable Energy Installations Emergency Response Cooperation Plans (ERCoP) for SAR Helicopter Operations’ Society of Naval Architects and Marine Engineers Society of Naval Architects and Marine Engineers (SNAME) Technical and Research Bulletin TRS-SA Guidelines for Site Specific Assessment of Mobile Jack-up Units Including the Recommended Practice and Commentary International Organisation for Standardisation ISO 19901-1:2005(E) Part 1: MetOcean design and Operating considerations. MWS-2-Appendices. The warranty surveyor in particular must take this situation in to account depending on the geographical area or region they are working in. ABS American Bureau of Shipping. AISC American Institute of Steel Construction. API American Petroleum Institute. Approved Bollard Pull Continuous static bollard pull is that obtained by a test at 100% of the Maximum Continuous Rating (MCR) of main engines, averaged over a period of 10 minutes. Where a certificate of Continuous Static Bollard Pull less than 10 years old can be produced, then this will normally be used as the Approved Bollard Pull. Approved Bollard Pull for tugs under 10 years old without a bollard pull certificate may be estimated as 1 tonne /100 (Cer tified) BHP of the main engines. Approved Bollard Pull for tugs over 10 years old, without a bollard pull certificate less than 10 years old, may be the greater of: • the certified value reduced by 1% per year of age since the BP test, or • 1 tonne/100 (Certified) BHP reduced by 1% per year of age greater than 10. ASPPR Arctic Shipping Pollution Prevention Regulations. Assured The Assured is the person who has been insured by some insurance company, or underwriter, against losses or perils mentioned in the policy of insurance. ATA Automatic Thruster Assist. Barge A nonpropelled vessel commonly used to carry cargo or equipment. Bending reduction The reduction factor applied to the breaking load of a rope or factor EB cable to take account of the reduction in strength caused by bending round a shackle, trunnion or crane hook. Page 4 of 166 Benign area An area that is free from tropical revolving storms and travelling depressions, (but excluding the North Indian Ocean during the Southwest monsoon season, and the South China Sea during the Northeast monsoon season). BHP / Brake Horse Power The measure of horsepower at continuous engine output after the combustion stage. BL (Breaking Load) Breaking load (BL) = Certified minimum breaking load of wire rope, chain or shackles, measured in tonnes. BP (Bollard Pull) Bollard pull (BP) = Certified continuous static bollard pull of a tug measured in tonnes. BV Bureau Veritas. Cable-laid sling A cable made up of 6 ropes laid up over a core rope with terminations at each end. Calculated Grommet The load at which a grommet will break. Breaking Load (CGBL) Calculated Rope The load at which a cable laid rope will break. Breaking Load (CRBL) Calculated Sling The load at which a sling will break. The breaking load for a sling Breaking Load (CSBL) takes into account the ‘Termination Efficiency Factor’. Cargo Where the item to be transported is carried on a barge or a vessel, it is referred to throughout this report as the cargo. If the item is towed on its own buoyancy, it is referred to as the tow. Cargo ship safety certificates Certificates issued by a certifying authority to attest that the (Safety Construction) vessel complies with the cargo ship construction and survey (Safety Equipment) regulations, has radiotelephone equipment compliant with (Safety Radio) requirements and carries safety equipment that complies with the rules applicable to that vessel type. Certificate validities vary and are subject to regular survey to ensure compliance. CASPRR Canadian Arctic Shipping Pollution Prevention Regulations. CBP / Continuous Bollard Pull See Approved Bollard Pull (above). Certificate of Approval (CoA) A formal document issued stating that, in its judgement and opinion, all reasonable checks, preparations and precautions have been taken to keep risks within acceptable limits, and an operation may proceed. Page 5 of 166 Consequence factor A factor to ensure that main structural members, lift points and spreader bars /frames have an increased factor of safety (including lateral loads) related to the consequence of their failure. Crane vessel The vessel, ship or barge on which lifting equipment is mounted. For the purposes of this report it is considered to include: crane barge, crane ship, derrick barge, floating shear-leg, heavy lift vessel, semisubmersible crane vessel (SSCV) and jack-up crane vessel. Classification A system of ensuring ships are built and maintained in accordance with the Rules of a particular Classification Society. Although not an absolute legal requirement, the advantages (especially as regards insurance) mean that almost all vessels are maintained in Class. Cold stacking Cold stacking is where the unit is expected to be moored up for a significant period of time and will have minimum or, in some cases, no services or personnel available. COSHH Control of Substances Hazardous to Health. Cribbing An arrangement of timber baulks, secured to the deck of a barge or vessel, formally designed to support the cargo, generally picking up the strong points in vessel and/or cargo. Demolition towage Towage of a “dead” vessel for scrapping. Deratisation Introduced to prevent the spread of rodent borne disease, Certification attesting the vessel is free of rodents (Derat Exemption Certificate) or has been satisfactorily fumigated to derat the vessel (Derat Certificate). Certificates are valid for 6 months unless further evidence of infestation found. Design environmental The design wave height, design wind speed, and other relevant condition environmental conditions specified for the design of a particular transportation or operation. Design wave height Typically the 10-year monthly extreme significant wave height, for the area and season of the particular transportation or operation. Design wind speed Typically the 10-year monthly extreme 1-minute wind velocity at a reference height of 10m above sea level, for the area and season of the particular transportation or operation. Determinate lift A lift where the slinging arrangement is such that the sling loads are statically determinate, and are not significantly affected by minor differences in sling length or elasticity. DNV Det Norske Veritas. Page 6 of 166 Double tow The operation of towing two tows with two tow wires by a single tug. DP Dynamic Positioning. Dry towage (or Dry tow) Transportation of a cargo on a barge towed by a tug. Commonly mis-used term for what is actually a voyage with a powered vessel, more properly referred to as ‘Dry Transportation’. Dry transportation Transportation of a cargo on a barge or a powered vessel. Dunnage See Cribbing. Dynamic Amplification Factor The factor by which the ‘gross weight’ is multiplied, to account for (DAF) accelerations and impacts during the lifting operation. EPIRB Emergency Position Indicating Radio Beacon. Flagged vessel A vessel entered in a national register of shipping with all the appropriate certificates. Floating offload The reverse of floating onload. Floating onload The operation of transferring a cargo, which itself is floating, onto a vessel or barge, which is submerged for the purpose. FLS Fatigue Limit State. FMEA Failure Modes and Effects Analysis. FOI Floating Offshore Installation. FOS Factor of Safety. FPSO Floating Production, Storage and Offload vessel. GL Germanischer Lloyd. GMDSS Global Maritime Distress and Safety System. GPS Global Positioning System. Grillage A steel structure secured to the deck of a barge or vessel, formally designed to support the cargo and distribute the loads between the cargo and barge or vessel. Grommet A grommet is comprised of a single length of unit rope laid up 6 times over a core to form an endless loop. Page 7 of 166 Gross weight The calculated or weighed weight of the structure to be lifted including a weight contingency factor and excluding lift rigging. See also NTE weight. HAZID Hazard Identification. Hook load The hook load is the ‘gross weight’ or NTE weight plus the ‘rigging weight’. Hot stacking Hot stacking may be defined as mooring the vessel in a manned functional condition, with the option to run machinery to provide sufficient power to operate all mooring winches, thrusters, etc. as may be required. IACS International Association of Classification Societies. IMDG Code International Maritime Dangerous Goods Code. IMO International Maritime Organisation. Independent leg jack-up A jack-up where the legs may be raised or lowered independently of each other. Indeterminate lift Any lift where the sling loads are not statically determinate. Inshore mooring A mooring operation in relatively sheltered coastal waters, but not at a quayside. Insurance warranty A clause in the insurance policy for a particular venture, requiring the approval of a marine operation by a specified independent survey company. IOPP Certificate International Oil Pollution Prevention Certificate (see also MARPOL). ISM Code International Safety Management Code - the International Management Code for the Safe Operation of Ships and for Pollution Prevention - SOLAS Chapter IX. Jack-up A self-elevating MODU, MOU or similar, equipped with legs and jacking systems capable of lifting the hull clear of the water. LAT Lowest Astronomical Tide. Lift point The connection between the ‘rigging’ and the ‘structure’ to be lifted. May include ‘padear’, ‘padeye’ or ‘trunnion’. Line pipe Coated or uncoated steel pipe sections, intended to be assembled into a pipeline. Page 8 of 166 LOA Length Over All. Loading The transfer of a major assembly or a module from a barge onto land by horizontal movement or by lifting. Load line The maximum depth to which a ship may be loaded in the prevailing circumstances in respect to zones, areas and seasonal periods. A Loadline Certificate is subject to regular surveys, and remains valid for 5 years unless significant structural changes are made. Loadout Transferring a cargo onto a vessel or barge, from the shore or from another vessel or barge. Location move A move of a MODU or similar, which, although not falling within the definition of a field 24-hour move, may be expected to be completed with the unit essentially in 24-hour field move configuration, without overstressing or otherwise endangering the unit, having due regard to the length of the move, and to the area (including availability of shelter points) and season. LRFD Load and Resistance Factor Design. LRS Lloyds Register of Shipping. Marine operation See Operation. MARPOL International Convention for the Prevention of Pollution from Ships 1973/78, as amended. Matched pair of slings A matched pair of slings are fabricated or designed so that the difference does not exceed 0.5d, where ‘d’ is the nominal diameter of the sling or grommet. Mat-supported jack-up A jack-up which is supported in the operating mode on a mat structure, into which the legs are connected and which therefore may not be raised or lowered independently of each other. MBL / Minimum Breaking Certified Minimum Breaking Load of wire rope, chain, stretcher or Load (MBL) shackle in tonnes. MBP / Maximum Bollard Pull The bollard pull obtained by a test, typically at 110% of the Maximum Continuous Rating (MCR) of main engines, over a period of 5 minutes. MCR / Maximum Manufacturer’s recommended Maximum Continuous Rating of the Continuous Rating main engines. Mechanical termination A sling eye termination formed by use of a ferrule that is mechanically swaged onto the rope. Page 9 of 166 Minimum Breaking The minimum allowable value of ‘breaking load’ for a particular sling Load (MBL) or grommet. Multiple tow The operation of towing more than one tow by a single tug. Mobile mooring Mooring system, generally retrievable, intended for deployment at a specific location for a short-term duration, such as those for mobile offshore units. MODU Mobile Offshore Drilling Unit. Mooring system Consists of all the components in the mooring system including shackles windlasses and other equipment and in addition, rig/vessel and shore attachments such as bollards. MOU Mobile Offshore Unit. For the purposes of this unit, the term may include mobile offshore drilling units (MODUs), and non-drilling mobile units such as accommodation, construction, lifting or production units. n/a Not applicable. NDT Non Destructive Testing. Net weight The calculated or weighed weight of a structure, with no contingency or weighing allowance. NMD Norwegian Maritime Directorate. NTE Weight A Not To Exceed weight, sometimes used in projects to define the maximum possible weight of a particular structure. Ocean towage Any towage which does not fall within the definition of a restricted operation, or any towage of a MODU or similar which does not fall within the definition of a 24-hour move or location move. Ocean transportation Any transportation which does not fall within the definition of a restricted operation. OCIMF Oil Companies International Marine Forum. Off-hire survey A survey carried out at the time a vessel, barge, tug or other equipment is taken off-hire, to establish the condition, damages, equipment status and quantities of consumables, intended to be compared with the on-hire survey as a basis for establishing costs and liabilities. Offload The reverse of Loadout (see above). Page 10 of 166 On-hire survey A survey carried out at the time a vessel, barge, tug or other equipment is taken on-hire, to establish the condition, any preexisting damages, equipment status and quantities of consumables. It is intended to be compared with the off-hire survey as a basis for establishing costs and liabilities. It is not intended to confirm the suitability of the equipment to perform a particular operation. Operation, marine operation Any activity, including loadout, transportation, offload or installation, which is subject to the potential hazards of weather, tides, marine equipment and the marine environment. Operational Reference Period The planned duration of the operation, including a contingency period. Padear A lift point consisting of a central member, which may be of tubular or flat plate form, with horizontal trunnions round which a sling or grommet may be passed. Padeye A lift point consisting essentially of a plate, reinforced by cheek plates if necessary, with a hole through which a shackle may be connected. Parallel tow The operation of towing two tows with one tow wire by a single tug, the second tow being connected to a point on the tow wire ahead of the first tow with the catenary of its tow wire passing beneath the first tow. Permanent mooring Mooring system normally used to moor floating structures deployed for long-term operations, such as those for a floating production system. Pipe carrier A vessel specifically designed or fitted out to carry Line pipe. Port of refuge A location where a towage or a vessel seeks refuge, as decided by the master, due to events occurring which prevent the towage or vessel proceeding towards the planned destination. A safe haven where a towage or voyage may seek shelter for survey and/or repairs, when damage is known or suspected. Procedure A documented method statement for carrying out an operation. PSA Petroleum Safety Authority Norway QTF / Quadratic Refers to the matrix that defines second order mean wave loads Transfer Function on a vessel in bichromatic waves. When combined with a wave spectrum the mean wave drift loads and low frequency loads can be calculated. Quayside mooring A mooring that locates a vessel alongside a quay (usually at a sheltered location). Page 11 of 166 RAO / Response Defines the vessel’s (first order) response in regular waves and Amplitude Operator allows calculation of vessel wave frequency (first order) motion in a given seastate using spectral analysis techniques. Redundancy check Check of the failure loadcase associated with the applicable extreme (survival) environment, e.g. the one leg damaged case. Register The list published from time to time of towing vessels, including all towing vessels entered into the Towing Vessel Approvability Scheme. Registry Registry indicates who may be entitled to the privileges of the national flag, gives evidence of title of ownership of the ship as property and is required by the need of countries to be able to enforce their laws and exercise jurisdiction over their ships. The Certificate of Registry remains valid indefinitely unless name, flag or ownership changes. Rigging The slings, shackles and other devices including spreaders used to connect the structure to be lifted to the crane. Rigging weight The total weight of rigging, including slings, shackles and spreaders, including contingency. Risk assessment A method of hazard identification where all factors relating to a particular operation are considered. Rope The unit rope from which a cable laid sling or grommet may be constructed, made from either 6 or 8 strands around a steel core. Safe Working Load (SWL) See Working Load Limit (WLL). Safety Management A document issued to a ship which signifies that the Company and Certificate (SMC) its shipboard management operate in accordance with the approved SMS. Safety Management A structured and documented system enabling Company personnel System (SMS) to implement the Company safety environmental protection policy. SART Search and Rescue Radar Transponder. Seafastening The means of preventing movement of the cargo or other items carried on or within the barge, vessel, or tow. Self-Elevating Unit More commonly know as a ‘Jack-up’. It is a Marine Unit equipped with legs and jacking systems capable of lifting the hull clear of the water. A ‘Jack-up’ unit may be used as a production platform, drilling platform, construction support platform or accommodation platform. Page 12 of 166 Semisubmersible A MODU or similar designed to operate afloat, generally floating on columns which reduce the water-plane area, and often moored to the seabed when operating. SemiSubmersible Unit A floating structure normally consisting of a deck structure with a number of widely spaced, large cross-section, supporting columns connected to submerged pontoons. Shelter point An area or safe haven where a towage or vessel may seek shelter, (or shelter port, in the event of actual or forecast weather outside the design limits or point of shelter) for the transportation concerned. A planned holding point for a staged transportation. Single laid sling A cable made up of 6 ropes laid up over a core rope. Single tow The operation of towing a single tow with a single tug. Skew Load Factor (SKL) The factor by which the load on any lift point or pair of lift points and rigging is multiplied to account for sling length mismatch in a statically indeterminate lift. Sling breaking load The breaking load of a ‘sling’, being the calculated breaking load reduced by ‘termination efficiency factor’ or ‘bending reduction factor’ as appropriate. Sling eye A loop at each end of a sling, either formed by a splice or mechanical termination. SLS / Serviceability A design condition defined as a normal Ser viceability Limit State / Limit State normal operating case. SOPEP Shipboard Oil Pollution Emergency Plan. Splice That length of sling where the rope is connected back into itself by tucking the tails of the unit ropes back through the main body of the rope, after forming the sling eye. Spreader bar (frame) A spreader bar or frame is a structure designed to resist the compression forces induced by angled slings, by altering the line of action of the force on a lift point into a vertical plane. The structure shall also resist bending moments due to geometry and tolerances. Staged transportation A transportation which can proceed in stages between shelter points, not leaving or passing each shelter point unless there is a suitable weather forecast for the next stage. Each stage may, subject to certain safeguards, be considered a weather-restricted operation. Page 13 of 166 Structure The object to be lifted. Submersible transport vessel A vessel which is designed to ballast down to submerge its main deck, to allow self-floating cargoes to be on-loaded and off-loaded. Suitability survey A survey intended to assess the suitability of a tug, barge, vessel or other equipment to perform its intended purpose. Different and distinct from an on-hire survey. Survey Inspection of commodity, structure or item for the purposes of determining condition, quantity, quality or suitability. SWL Safe Working Load in tonnes. Tandem tow The operation of towing two or more tows in series with one tow wire from a single tug, the second and subsequent tows being connected to the stern of the tow in front. TA Thruster Assist. Termination efficiency The factor by which the breaking load of a wire or cable factor ET is multiplied to take account of the reduction of breaking load caused by a splice or mechanical termination. Trunnion A lift point consisting of a horizontal tubular cantilever, round which a sling or grommet may be passed. An upending trunnion is used to rotate a structure from horizontal to vertical, or vice versa, and the trunnion forms a bearing round which the sling, grommet or another structure will rotate. Tonnage A measurement of a vessel in terms of the displacement of the volume of water in which it floats, or alternatively, a measurement of the volume of the cargo carrying spaces on the vessel. Tonnage measurements are principally used for freight and other revenue based calculations. Tonnage Certificates remain valid indefinitely unless significant structural changes are made. Tonnes Metric tonnes of 1,000 kg (approximately 2,204.6 lbs) are used throughout this document. The necessary conversions must be made for equipment rated in long tons (2,240 lbs, approximately 1,016 kg) or short tons (2,000 lbs, approximately 907 kg). Tow The item being towed. This may be a barge or vessel (laden or unladen) or an item floating on its own buoyancy. Approval of the tow will normally include, as applicable: consideration of condition and classification of the barge or vessel; strength, securing and weather protection of the cargo, draught, stability, documentation, emergency equipment, lights, shapes and signals, fuel and other consumable supplies, manning. Page 14 of 166 Towage The operation of transporting a non-propelled barge or vessel (whether laden or not with cargo) or other floating object by towing it with a tug. Towing (or towage) The procedures for effecting the towage. Approval of the towing arrangements (or towage) arrangements will normally include consideration of towlines and towline connections, weather forecasting, pilotage, routeing arrangements, points of shelter, bunkering arrangements, assisting tugs, communication procedures. Towing Vessel Approvability A document issued by warranty companies stating that a towing Certificate (TVAC) vessel complied with the requirements at the time of survey, or was reportedly unchanged at the time of revalidation, in terms of design, construction, equipment and condition, and is considered suitable for use in towing service within the limitations of its category, bollard pull and any geographical limitations which may be imposed. Towing Vessel Approvability The scheme whereby owners of towing vessels may apply to a Scheme (TVAS) warranty company to have their vessels surveyed, leading to the issue of a TVAC. Towline connection strength Towline connection strength (TC) = ultimate load capacity of towline connections, including connections to barge, bridle and bridle apex, in tonnes. Towline pull required (TPR) The towline pull computed to hold the tow, or make a certain speed against a defined weather condition, in tonnes. Transportation The operation of transporting a tow or a cargo by a towage or a voyage. Tug The vessel performing a towage. Approval of the tug will normally include consideration of the general design; classification; condition; towing equipment; bunkers and other consumable supplies; emergency and salvage equipment; communication equipment; manning. Tug efficiency (Te) Defined as: effective bollard pull produced in the weather considered certified continuous static bollard pull. UKCS United Kingdom Continental Shelf. ULS / Ultimate Limit State The intact loadcase associated with the applicable extreme (survival) environment. Page 15 of 166 Ultimate Load Ultimate load capacity of a wire rope, chain or shackle or similar Capacity (ULC) is the certified minimum breaking load, in tonnes. The load factors allow for good quality splices in wire rope. Ultimate load capacity of a padeye, clench plate, delta plate or similar structure, is defined as the load, in tonnes, which will cause general failure of the structure or its connection into the barge or other structure. Unrestricted operation A marine operation which cannot be completed within the limits of a favourable weather forecast (generally less than 72 hours). The design weather conditions must reflect the statistical extremes for the area and season. Vessel A marine craft designed for the purpose of transportation by sea. VLA Vertical Load Anchors. Voyage For the purposes of this report, the operation of transporting a cargo on a powered vessel from one location to another. Watertight A watertight opening is an opening fitted with a closure designated by Class as watertight, and maintained as such, or is fully blanked off so that no leakage can occur when fully submerged. Weather unrestricted An operation with an operational reference period generally operation greater than 72 hours. The design environmental condition for such an operation shall be set in accordance with extreme statistical data. Weather restricted An operation with an operational reference period generally less operation than 72 hours. The design environmental condition for such an operation may be set independent of extreme statistical data, subject to certain precautions. Weathertight A weathertight opening is an opening closed so that it is able to resist any significant leakage from one direction only, when temporarily immersed in green water or fully submerged. WLL / Working Load Limit The maximum static load that the wire, cable or shackle is designed to withstand. WMO World Meteorological Organisation. WPS Welding Procedure Specification. WSD Working Stress Design. 9-Part sling A sling made from a single laid sling braided nine times with the single laid sling eyes forming each eye of the 9-part sling. Page 16 of 166 Appendix B Example of a Certificate of Approval (CoA) Page 17 of 166 Appendix C IADC General Ocean Tow Recommendations for Jack-Up Drilling Units GENERAL OCEAN TOW RECOMMENDATIONS FOR JACKUP DRILLING UNITS International Association of Drilling Contractors (I.A.D.C.) February 13, 1991 Manning 1. Manning should comply with U.S. Coast Guard regulations or other national regulatory rules. The number of crew will be dependent on the length of the voyage and be limited to essential personnel only and should not exceed 50 % of lifeboat capacity. Ocean Tow Loading Plan 2. A Loading Plan should be formulated and, if required, submitted to the Underwriter’s Marine Survey company utilized by the Contractor for the tow in time for proper review. (See Addendum A enclosed for a sample loading plan) 3. Cargo is defined as any material, temporary structure, shipping container, consumable item, machinery, tubular, equipment and items not included in the drill barge lightship weight. 4. Stowage of on the main weather deck of a Jackup drilling unit while on an ocean tow is not desirable and should be avoided with the exceptions noted below. 5. Exceptions to this policy my be permitted if: a. A permanent structure has been erected for the stowing and securing of an item such as a pipe rack for drill pipe and drill collars, or a mandrel and locking beams for a BOP. The permanent structures should be adequate for their intended purpose, reviewed, and approved by a classification society in accordance with the appropriate rules. b. Cargo is elevated or located above the main deck by mans of a suitable support structure. c. Temporary structures are permitted when designed by a registered professional engineer and approved by the underwriter’s marine surveyor. Towage 6. One set of up-to-date navigation charts and pilot books for the tow course and alternate courses should be available for the voyage aboard the rig including detailed charts of ports of refuge. 7. Tow routing should be determined in advance including ports of refuge and the required entry data. Page 18 of 166 8. A weather service should be selected with a beck ground in ocean tow forecasting. Weather updates should be sent every 12 hours with at least 72 hour advance forecasts. Direct communication with a marine weather forecaster is recommended. 9. The Towing vessel(s), and towing gear, should be designed and equipped for towing in ocean service with full crew aboard. Towing gear should be inspected and approved by the attending marine and the O.I.M. prior to departure. 10. The bollard pull of the towing vessel(s) should be of sufficient size for the intended tow. 11. Communication means between the rig and the towing vessel(s) is of utmost importance. Backup communications should be provided. The vessel should provide a qualified riding crew member to assist the rig crew during tow. Language should not be a barrier. 12. Critical motion curves should be provided to the rig crew and the towing vessel(s) prior to departure. (see addendum B) Manufacture recommendations for proper leg length and shimming should be adhered to for the tow. 13. An emergency towing line should be strapped along the side of the hull just below top deck level in a manner permitting quick release. The tow line should be of a size suitable for the tow intended accounting for the bollard pull of the tow vessel(s), including shock loads. 14. A polypropylene shock line, the size and length suitable for the bollard pull of the tow vessel(s) being used, should be attached to the emergency tow line with suitable connectors. 15. A main tow line bridle recovery line(s) should be fitted and run from the and of the bridle or tow plate to a winch on the barge to allow retrieval in the main tow wire(s) part. Stability 16. Stability calculations addressing the tow conditions should be performed to insure positive stability in compliance with the rig operating manual. These calculations should be submitted to and approved by the underwriter’s Marine Survey company being utilized in time for proper review. (see Addendum A) Draft and Trim 17. Within the limits of the loadline certificate, the man draft for the tow should be determined from the stability calculations in item 16 above. 18. Weight should be distributed to produce a level condition transversely with a slight trim by the stern. Trim is to be obtained by locating material or equipment carried with necessary liquid trimming ballast kept to a minimum. 19. Liquid variable load should be kept to a minimum. Hull tanks that contain liquids should be pressed and maintained full during the voyage. 20. All tanks, including active mud tanks, not required on the voyage, should be empty at the time of departure. Page 19 of 166 Watertight Integrity 21. The operating manual for the rig should clearly show the location of watertight closures and should be complied with during the tow. 22. Deck openings such as sounding tubes should be protected from damage 23. Consideration should be given to the modification all weather deck preload hatch covers, vent fan covers, cargo hatch cover, etc. with clamp bars or welded strapping to prevent opening from sea action. 24. Rig service take on lines Such as out, barite, fuel, potable water, or drill water located on the outer lull areas should be capped and protected from sea damage by sea action. 25. All weather/watertight closures, ventilation ducts, etc. with the exception of intakes necessary for the operation of the vessel, should be seed from sea action. Pumping Arrangements 26. The vessel’s bilge/ballast service pumps should be tested and determined to be in good working order prior to departure. Pumps are to be maintained in a state of readiness throughout the tow. Compartment Sounding 27. All hull compartments and void spaces should be fitted with sounding tubes. All sounding tubes should be clearly identified and fitted with caps that are capable of being tightly secured. 28. Soundings should be taken at least every 12 hours of all void and preload tanks. Hull compartments should be inspected or sounded also and the results should be logged for the duration of the 29. A diagram of the sounding tube locations should be posted in the machinery deck spaces and in the control room. 30. A means of determining the changes in liquid levels in the perimeter hull tanks must be available for use from a protected location. 31. The manufacturer’s data should be furnished to indicate that the derrick can withstand the roll motions anticipated for the tow. This data should be in the rig operating manual. 32. All Derrick travelling equipment should be seared for the tow. 33. Bow anchors should be removed from below water racks and strapped to the deck or stored if there is the possibility of becoming entangled in the tow gear. 34. Secure or remove anchor buoys from their racks to prevent dislodging by sea action. Cranes 35. Crane should be lowered into steel support structures and secured against vertical or lateral movement. 36. Cranes should be secured against revolving per manufactures recommendations. Page 20 of 166 Navigation Lights, Signals and Safety Equipment 37. Side Lights and stern light should be checked to make sure they are in good working order. 38. Life vests, throw over life rings and other means of rescue should be checked and readied for deployment, if need. 39. Signalling devices should be stored in the control room, inspected and determined that they are within inspection dates for use, if needed. Potable Water and Fuel Oil 40. Sufficient potable water and fuel for the length of the tow, plus 25% safety factor, should be carried. 41. A potable pump should be available to obtain water from the potable water tanks in the event of pump failure. 42. Because sediment in the fuel tanks can be stirred up during tow, a centrifuge should be installed prior to departure to remove contaminants from the fuel pumped to the engine day tanks. Extra engine fuel filters should be in supply. Damage Control 43. The following emergency and/or damage control equipment and material is recommended to carried aboard for the tow, or it’s equivalent. 400 lbs. cement 400 lbs. sad 20 lbs. concrete mix accelerator 40 ft. of 1” x 12” timber 24 lbs. of oakum or similar caulking compound 24 wooden wedges 24 wooden plugs of various sizes Welding and cutting apparatus 50 ft. of 4” x 4” angle iron 100 sq. ft. of 1/2” steel plate. 100 sq. ft. of 1” steel plate 500 ft. 1” polypropylene rope 500 ft. 1” wire rope 20 Ton Portapower hydraulic jack 100 ft. 2” x 4” x 10’ timber Two portable diaphragm air pumps 44. Spare shackle, heaving lines, turnbuckles, etc. should be aboard for the tow. 45. Fog horn, ship whistle or bell, search light, etc. should be in operating condition. Page 21 of 166 46. Secure all equipment in the accommodations area for heavy seas. 47. Strip water from the preload tanks, unused drill water tanks and void tanks prior to and during the tow. 48. Lifeboat machinery and equipment should be checked for compliance with existing regulations and be in proper operating condition. Lifeboat fuel tanks should be checked for contaminants and feel cleaned or replaced as necessary Spare fuel filters should be stowed aboard the lifeboat for use, if required. 49. The emergency power source should be available for use at all times and teed at periodic intervals Riding Crew Instructions 50. Sea watches should be maintained at all times during the tow. The following information should be entered into the log: a. Weather data including; wind force, wave/swell height/Period. b. Motion characteristics of the vessel are of the utmost importance. The Drill Barge Master (licensed or unlicensed) must observe degrees of pitch and roll and their corresponding periods and request the tug to change course and/or speed to prevent the Drill Barge motions from exceeding the values given in the Operations Manual critical motion curves. c. All important communication with the towing vessel(s) including speed, course, change in tow wire length, etc. should be recorded. d. me Position should be obtained from the towing vessel(s) every 6 hours and recorded in the rig log. 51. Each hull tank should be sounded and logged every 12 hours. 52. All watertight doors between compartment and from the compartments to outside exits should be kept closed at all times except when personnel pass. 53. Tow gear should be inspected every 6 hours and the results logged. 54. At least two (2) members of the crew should be awake at all times. 55. Radio contact mist be maintained on a 24 hour basis with the tow vessel(s). 56. Emergency drills should be held prior to departure and once a week during the tow. Results should be logged. 57. All navigation lights should be checked every 6 hours and the results logged. 58. Daily reports are should be forwarded to the Contractor’s headquarters at least daily. Page 22 of 166 OCEAN TOW LOADING PLAN ADDENDUM A February 13, 1991 ADDENDUM A TO: General Marine Surveyor Company FROM: United Marine Drilling Contractors SUBJ: Ocean Tow Stowage Plan Please review the enclosed Ocean Tow Loading Plan for our 116 class hull. The loading plan is comprised of the following: 1. A completed loading calculation for the start of the tow based on the latest information from our rig survey. The stability calculations are based on two leg down positions (12.17 ft. for 70 knots and 45.90 ft. for severe storm). 2. All loose gear will be stowed below deck in stowage areas 11 through 13 and secured to prevent shifting during the tow. (see enclosed drawings) 3. The drilling tubulars will be secured with turnbuckles and chain and containment barriers will be fabricated at the ends of the racks, subject to your final approval. Four areas are anticipated at this time. (see enclosed drawings) 4. Two miscellaneous cargo areas will be constructed on top of the quarters in containment areas in order to remove these items from possible sea action. (see enclosed drawings) 5. The Substructure/drill floor assembly will be in the full forward position for the tow and secured to the hull with the clamping arrangement provided by the manufacturer. 6. The emergency tow gear will be strapped along the port side of the hull and provisions made for the deployment in severe weather if the need should arise. 7. The deepwell tower will be secured to the hull with clamping arrangements designed by the manufacturer. Three 3/4 inch guy wires will be connected to the tower in three different directions securing the tower from the rig motions anticipated. Please review the Loading Plan provided at this time. As you know, final loading will depend on your survey prior to the departure of the rig. Page 23 of 166 Page 24 of 166 Page 25 of 166 Page 26 of 166 Page 27 of 166 Page 28 of 166 Page 29 of 166 Page 30 of 166 Page 31 of 166 ADDENDUM B February 13, 1991 Page 32 of 166 Appendix D JRC Marine Warranty Surveyors Code of Practice and scope of Work Joint Rig Committee Room 358, Lloyd’s, One Lime Street London EC3M 7DQ Tel: (+44) 020 7327 3333 Fax: (+44) 020 7327 4443 _____________________________________________________________________________________ PRIVATE AND CONFIDENTIAL Enquiries to: JR 2010/010 John Gurtenne 23 July 2010 (Direct Dial 020 7327 4045) Joint Rig Committee Marine Warranty Surveyors Code of Practice and Scope of Work (JR 2010/010) Attached for underwriters use and information is a copy of the revised Joint Rig Committee Marine Warranty Surveyors Code of Practice (CoP) and Generic Scope of Work (GSoW) (JR2009/002), drawn up by JRC after consultation with surveyors, and others.. This Code of Practice and Generic Scope of Work replaces the 2004 Code of Practice and 2005 Generic Scope of Work previously issued by JRC. It is now presented as a single document which underwriters may use as an Endorsement to marine energy coverages they are issuing. In common with all JRC produced Clauses, this Clause is published by JRC, but it is expressly non-binding and JRC makes no recommendation as to its use in particular policies. Underwriters are of course free to offer different policy wordings and clauses to their policy holders. The Code of Practice and Scope of Work has the following objectives: To: • Clarify the respective roles of the Marine Warranty Surveyor, the Assured, and Underwriters • Define the function of the Marine Warranty Surveyor’s Scope of Work. • Outline criteria for Marine Warranty Surveying activities. • Establish guidelines for communication with underwriters. This Endorsement also gives Underwriters the option of specifying the application of an Project Specific Scope of Work (PSoW) where they think this is required, Should underwriters have any questions on the background, & use of this Code of Practice and Scope of Work, please contact John Gurtenne, secretary to the Joint Rig Committee (john.gurtenne@lmalloyds.com 020 7327 4045, or Len Messenger, Chairman of the JRC’s Engineering and Survey Sub-Committee, on 020 7648 3577. Simon Williams Chairman Joint Rig Committee Page 33 of 166 MARINE WARRANTY SURVEY 1) Coverage under this Policy for project activities is conditional upon: a) A Marine Warranty Surveyor being appointed by the Assured from the following panel _______________________________________________________1 on or before _ _ /_ _ / _ 2; and b) Issuance of the Certificates of Approval (C of A’s) by the Marine Warranty Surveyor for each operation as specified in the Generic Scope of Work (GSOW) contained herein or the Project Specific Scope of Work (PSOW) explicitly agreed by Underwriters. A kick off meeting is required Yes/No3 2) It is the duty of the Assured to procure the compliance with all recommendations, requirements or restrictions of the Marine Warranty Surveyor within the specified timescales. In the event of a breach of this duty, Underwriters will not be liable for any loss, damage, liability or expense arising from or contributed to by such breach. 3) The Marine Warranty Survey shall be conducted in accordance with the Marine Warranty Surveyor Code of Practice (CoP) and the GSOW contained herein (or the Project specific Scope of Work (PSOW) as agreed by the Contract leader(s)). A material change to the project will require a review of the Scope of Work. 4) The cost of the Marine Warranty Survey will be borne by the Assured. 5) Any expenses incurred to comply with the Marine Warranty Surveyor’s recommendations will be solely at the expense of the Assured. 6) The Marine Warranty Surveyor shall not be restricted from furnishing information to or consulting in an unrestricted manner with Underwriters. 7) Underwriters shall be entitled to receive a copy of any recommendations and/or reports directly from the Marine Warranty Surveyor. ___________________ 1 Names of MWS Companies to be inserted 2 Date to be inserted 3 Circle required option. Page 34 of 166 Joint Rig Committee Marine Warranty Surveyors’ Code of Practice (CoP) 2010 This CoP has been produced in order to establish agreed standards for Marine Warranty Surveyors’ performance while conducting Marine Warranty Surveys. It has the following objectives: To: · Clarify the role of the Marine Warranty Surveyor. · Define the function of the Marine Warranty Survey Scope of Work. · Outline approval criteria for Marine Warranty Surveying activities. · Establish minimum standards for Marine Warranty Surveyor performance. · Define lines of communication between Underwriters and the Marine Warranty Surveyor. Nothing in this CoP shall relieve any party of any legal obligations existing in the absence of this document The Code of Practice outlines the obligations for the Marine Warranty Surveyor, the Assured & the Underwriter. The Code of Practice includes a Generic Scope of Work (GSOW) in tabular format. A tailored Project Specific Scope of Work (PSOW) may be substituted for the GSOW with the explicit agreement of Underwriters. 1 Role of the Marine Warranty Surveyor 1.1 The fundamental objective of the Marine Warranty Surveyor is to make reasonable endeavours to ensure that the risks associated with the warranted operations to which a Marine Warranty Surveyor is appointed are reduced to an acceptable level in accordance with best industry practice. 1.2 The Marine Warranty Surveyor Company will only appoint personnel who are demonstrably competent, in terms of qualifications and experience, to perform the review/approval activity being undertaken in accordance with the Marine Warranty Scope of Work. 1.3 The Marine Warranty Surveyor will be satisfied, so far as possible, that the operations are conducted in accordance with: · recognised codes of practice for design and operations; · best industry practice appropriate for the vessels, equipment and location; · vessels and equipment being used within defined safe operating limits. 1.4 The Marine Warranty Surveyor will make available to Underwriters: · an opinion on the adequacy of the Marine Warranty Scope of Work; · particulars of the experience of the key personnel to be engaged; · a schedule of actual and proposed site attendances; · a schedule of Certificates of Approval to be issued. 1.5 The Marine Warranty Surveyor shall perform a review of the relevant documentation in accordance with the requirements of Item 1.3 above relating to the proposed operations within the Marine Warranty Scope of Work including, but not limited to: · calculations; · drawings; · procedures; · certificates; · manuals; · relevant reports. 1.6 The Marine Warranty Surveyor shall carry out suitability surveys of vessels, structures and equipment prior to each operation, including any required follow up “close out” inspections unless otherwise defined in the Marine Warranty Scope of Work, and shall: Page 35 of 166 · establish that the relevant items are suitable for the proposed operations; · make known, in clear terms, in writing to the Assured the recommendations to be implemented prior to commencement of the proposed operations; · make known, in clear terms, in writing to the Assured the recommendations to be implemented during the period of the proposed operations; · review metocean conditions and, where appropriate, incorporate requirements as to metocean conditions in the recommendations in the Certificate(s) of Approval; · observe and record the preparations for the proposed operations; · attend and witness critical function tests or relevant assurance tests. 1.7 Subject to the Marine Warranty Surveyor being satisfied that the objectives outlined under Items 1.1 above will be met, the Marine Warranty Surveyor will issue a Certificate of Approval. The Certificate of Approval will clearly identify: · the operation to be carried out; · the vessel(s) to be used; · recommendations to be satisfied during the period of the proposed operations within the Marine Warranty Scope of Work. Recommendations issued for the Assured’s implementation should be targeted to reduce risk to Underwriters and worded in a clear and explicit manner and whether the recommendation has been implemented or not should be capable of being objectively verified. 1.8 The Marine Warranty Surveyor will: · advise Contract leader(s) when a confidentiality agreement with the Assured is in place which would preclude the exchange of information or communication with Contract leader(s); · not provide any other services to the Assured and/or Operator and/or Main Contractor(s) and/ or Sub Contractor(s)that could present a conflict of interest with the Marine Warranty Work, for example: i) Marine or Design Consultant involved in a/ Design of project components to be used in a marine operation, the failure of which could compromise the integrity of a project asset (for example a lift beam or padeye). b/ Primary analysis of structures, hulls or component parts thereof. Note: the Marine Warranty Surveyor is however expected to review a design by others where this has a direct bearing on the marine risk e.g. check of the strength of launch frames on a launch jacket, or assessment of a lift analysis of a deck. c/ The production of procedures, project standards, risk assessments and other management documentation which influences how a marine operation is conducted and which has a direct bearing on the risk of a particular marine operation e.g. loadout, launch, lift of a jacket. ii) Loss adjuster iii) Classification Authority iv) Verification 1.9 The Marine Warranty Surveyor will immediately advise Contract leader(s), with a copy to the Assured: · if any Certificate of Approval is withheld; or a Non Conformance Certificate issued; · if the Assured fails to comply with any recommendations made by the Marine Warranty Surveyor; · of any proposed changes to relevant key personnel employed by the Marine Warranty Surveyor. 1.10 The Marine Warranty Surveyor will issue the following status reports to the Contract leader(s) direct at key risk milestones: · the marine warranty survey activity carried out in the period; · the marine warranty survey activity planned prior to the next risk milestone; · copies of Certificate(s) of Approval issued since the last report. Page 36 of 166 If the Assured has provided insufficient information to perform a comprehensive review or the Marine Warranty Surveyor’s questions/requests for information remain pending, then the Marine Warranty Surveyor shall make this clear in his reports to Underwriters and outline the potential implications of the omissions. 1.11 All equipment and vessels associated with load-out, transportation and installation activities shall be fully operational and used within their safe working limits, which shall be agreed by the Marine Warranty Surveyor. All vessels (including offshore cranes, pipelay vessels, rigs and flotels) to be in IACS Class. Marine Warranty surveyor to agree all outstanding Class items as not material to intended operations. Marine Warranty surveyor to approve limiting metocean criteria, and weather windows for all marine operations. 2 Role of the Assured 2.1 Once appointed on the project the Marine Warranty Survey Company shall not be changed without the express and prior agreement of the Contract leader(s). 2.2 The Assured shall provide the Marine Warranty Surveyor with a point of contact for the Contract leader(s) and an appropriate point of contact in the Assured’s organisation to assist with the resolution of queries. 2.3 The Assured will provide Contract leader(s) with the contact details of the Marine Warranty Surveyor(s) within 14 working days following appointment of the same. 2.4 The Assured will provide the Marine Warranty Surveyor(s) with the contact details of Contract leader(s) within 14 working days following appointment of the same. 2.5 The Assured shall procure Marine Warranty Surveyor participation at all relevant project management meetings, including marine operation HAZOPs/HAZID, contingency planning and assurance/testing plans. 2.6 The Assured shall contract the Marine Warranty Surveyor directly (without the involvement of any contractor or intermediary) unless required to enable compliance with the law in the jurisdiction or government regulations. 2.7 The Assured shall appoint a single Marine Warranty Survey Company for the entire scope of work herein. 3 Role of the Underwriters 3.1 The Panel of Marine Warranty Surveyors is to be agreed by the Contract leader(s). Other additions to the panel will need to demonstrate their capability/ experience of similar projects and water depths, and to be agreed by the Contract leader(s). 3.2 On each project Underwriters will specify whether a Kick Off meeting is required between Underwriters, the Assured and the Marine Warranty Surveyor. The Assured, Contract leaders and Marine Warranty Surveyor shall agree key risk milestones and date(s) for a joint review of the project scope and development. 3.3 At the request of the Marine Warranty Surveyor, Underwriters will make available: · The PSOW, otherwise the GSOW to be used; · relevant applicable policy terms and conditions including, in particular, any warranty provisions or conditions precedent; · identity and contact details (including telephone, e – mail, fax and out of hours numbers) of the nominated Contract leader(s) to receive communications from the Marine Warranty Surveyor. Page 37 of 166 GENERIC SCOPE OF WORK (GSOW) Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval GENERAL ACTIVITIES Metocean criteria, including limiting seastates, for all marine operations. X Weather forecasting procedures X Weight reports and weight contingency factors X Procedures for use of installation vessels /equipment inc. ROVs, ROV tooling, pile hammers, etc. X Tow routes/passage plans / fuelling plans and safe havens X Loadout Manual(s)including ballast plan, quay strength, vessel strength and intact and damaged stability. X Transportation Manual(s) including bollard pull requirements, vessel strength and intact and damaged stability. X Installation Manual(s) including installation vessel thruster reliability and operational procedures, station keeping/mooring arrangements X HUC and Project handover X Sufficiency of data acquisition & testing for soil/rock mechanics and geotechnical parameters at proposed locations for foundations of all installations. X Adequacy of structures to withstand loads during loadout, tow and installation operations X Design codes and recommended practices X Project QA/QC procedures X Management of Change procedures X Project Communications and Interfaces X Installation vessels suitability surveys X X Tugs / barges suitability surveys X X Emergency contingencies X Page 38 of 166 Project Phase Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval FIXED PLATFORMS a) Fabrication and Loadout Weather forecasting procedures X Barge and cargo stability X Ballasting system and procedures X Barge anchored whilst loaded and mooring during loadout / loaded (incl. Fendering) X Motive power systems (winches, trailers, etc) X Structural strength of skidding system or trailers X Link beam/bridge design X Rigging and lift point design X Capability and certification of cranes X Grillage structural checks X Water depth, tidal limitations X Certification of all loadout equipment X Emergency contingency plans X Ballast system trials X Loadout operation X X b) Transportation Procedure for departure (incl draft, tidal, environmental limits) X Motion Response analysis X Grillage and Seafastening design, including Fatigue design considerations (incl NDT documentation) X X X Firefighting, Life saving and emergency equipment for manned tows X X Emergency anchors and mooring including, mounting and release system. X Internal seafastenings / voyage protection X X X Cargo towage / Transportation X Attend Sailaway Issue C of A for Sailaway Page 39 of 166 Project Phase Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval c) Installation Site/seabed survey and water depth X Jacket launch system and equipment X X X Jacket Launch operation X X X Jacket upending X X Template docking X X Jacket on-bottom stability X Jacket buoyancy tank removal X Static and dynamic hook load calculations (single and dual crane lifts) including lifting through water considerations. The independent lifting calculations performed shall include environmental limitations and be in accordance with the approved crane(s) curves. All lifting factors shall be approved by MWS X Lifting equipment design and certification X Jacket Installation (inc. Hydrostatic Collapse Check) X X X Integrated deck / MSF / Module Lift / Floatover X X X Lift points X Bumpers and guiding systems X As-built dimensions of jacket/module interfaces Piling calculations, analysis and Installation Manuals X X (extent of attendance during piling to be agreed) Installation vessel position monitoring/control X Crane suitability - Crane(s) to be inspected prior to lifting operations taking place. This inspection shall include but not be limited to; Crane Certification and Vessel Class; operating history, maintenance and repair records for Crane and Marine systems ; An external visual examination of the Crane(s) and Vessel. X X Floating Cranes DP & Ballast systems trials X X X Tug configuration X Emergency contingencies X Launch preparations including seafastening removal and barge ballasting X X X Page 40 of 166 Project Phase Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval FLOATING STRUCTURES a) Fabrication and Sailaway Vessel condition X Mooring adequacy in yard (to withstand natural hazard exposures e.g. typhoons) X X (Attend to confirm installed mooring) X Cargo stowage and securing X X X Structural strength/fatigue X Towing equipment X X Dry transport vessel suitability X X Vessel Sailaway Attend Sailaway Issue C of A for Sailaway b) Transportation Certification and documentation X Transportation route and weather conditions X Bunkering X Tug or propulsion systems X Stability, ballasting and watertight integrity X Vessel Motions X Seakeeping/heading control X Navigation lights and shapes X Emergency contingencies and equipment (incl. safety equipment) X X Communications and navigational equipment X X Manning X c) Installation Installation – anchors and mooring system X X X Station keeping – Mooring/DP/Tethers X Hook up with infrastructure X X X Lifting equipment design and certification X Module Lifts at offshore site X X X Page 41 of 166 Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval RIGID PIPELINES a) Fabrication and Load-out Pipe joint/reel storage and handling X X X Pipe loading and uploading X X Pipe barge sailaway X X b) Transportation Seafastenings X X X c) Installation Start-up and Termination X X X Installation aids – DMA, A & R head X Assess pipelay equipment and machinery for adequacy. Witness tensioner calibration. X X X Pipelay Vessels DP Trials X X X Pipelay (including lay, expansion, stability and freespan analysis) X X (Underwriters will stipulate if full attendance is required) X Pipeline Installation Analysis (To be reassessed if configuration changes i.e. stinger changes) X Laydown (including preservation procedures for long laydowns and met ocean criteria for commencement of temporary laydown) X X (If laydown period anticipated to exceed 1 month) X Buckle avoidance and detection strategy inc. pipeline tension, load cell calibration, and D/t limitations. X Field joint coating X Crossings X X X Trenching and backfilling X X X Slope stabilisation, mattress protection, rock dumping X Tie-in X Shore approach/pull-in design including dredging and backfilling. X Horizontal Drilling at shore approach X Cleaning and Gauging X X Pressure testing procedure X X X Contingencies including – Abandonment and recovery and Dry/Wet buckle X Page 42 of 166 Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval SUBSEA EQUIPMENT, UMBILICALS, FLOW-LINES and RISERS a) Fabrication and Load-out Manufacturers reeling/spooling X X X Load-out X X X b) Transportation Transportation including sea-fastening X X X c) Installation Installation lines (Including Static and dynamic analyses for all flexible umbilical, flow-lines and risers) X X X Ancillary items such as buoyancy modules, VIV strakes and clamps. X On-bottom stability, crossing, slope stability, free-spans X Suction piles (foundations/anchors) X X X Installation equipment (lifting and lowering), docking and positioning analyses) X X X Pipe spool, jumper installation X X (For Deepwater > 500m) X (For Deepwater > 500m) Manifold/ tree and other hardware installation X X X Temporary installation aids, rigging etc. X Riser/umbilical / power cable pull-in. X X X Riser installation at platform / FPSO X X X Hook-up, commissioning and project handover. Including hydrotests. X Contingency procedures for recovery of damaged subsea components X QA/QC non-conformance reports X Page 43 of 166 Project Activity Review & Approve: 1. Procedures 2. Dwgs. 3. Design Calcs. 4. Analysis Attend Issue Certificate of Approval VESSEL ACTIVITY DURING CONSTRUCTION PERIOD a) All Project Vessels (Inc. Semi-Sub Rigs and Flotels) Anchoring if within 500m of Project Facilities (Platforms, Templates / Manifolds / Pipelines)) X X X Vessels operating on DP within 500m of Existing Project Facilities, including DP system adequacy, redundancy and condition X X (Attend DP Trials) X b) Jack-Up Rigs Sufficiency of Soil Analysis for Jack-Up Rig punchthrough assessment. Independent punchthrough risk assessment and mitigation measures. X Risk Reduction measures (well shut-in, blowdown, pipeline depressurisation etc.) for Jack-up move onto / off location. X Rig Move - Jack-Up / Jack Down Operations X X X Key X Denotes activity to be performed DMA Dead man anchor A&R Abandon and recovery VIV Vortex Induced Vibration HUC Hook-up and commissioning NDT Non Destructive Testing DP Dynamic Positioning JR 2010/010 23 July.2010 A Joint Committee of the IUA and LMA Page 44 of 166 Appendix E Marine Insurance Act 1906 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Marine Insurance Act 1906 1906 CHAPTER 41 6 Edw 7 An Act to codify the Law relating to Marine Insurance. [21st December 1906] Annotations: Modifications etc. (not altering text) C1 This Act is not necessarily in the form in which it has effect in Northern Ireland C2 Act extended by S.I. 1972/971, art. 4, Sch. 15 MARINE INSURANCE 1 Marine insurance defined. A contract of marine insurance is a contract whereby the insurer undertakes to indemnify the assured, in manner and to the extent thereby agreed, against marine losses, that is to say, the losses incident to marine adventure. 2 Mixed sea and land risks. (1) A contract of marine insurance may, by its express terms, or by usage of trade, be extended so as to protect the assured against losses on inland waters or on any land risk which may be incidental to any sea voyage. (2) Where a ship in course of building, or the launch of a ship, or any adventure analogous to a marine adventure, is covered by a policy in the form of a marine policy, the provisions of this Act, in so far as applicable, shall apply thereto; but, except as by this section provided, nothing in this Act shall alter or affect any rule of law applicable to any contract of insurance other than a contract of marine insurance as by this Act defined. 3 Marine adventure and maritime perils defined. (1) Subject to the provisions of this Act, every lawful marine adventure may be the subject of a contract of marine insurance. Page 45 of 166 2 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) In particular there is a marine adventure where— (a) Any ship goods or other moveables are exposed to maritime perils. Such property is in this Act referred to as “insurable property”; (b) The earning or acquisition of any freight, passage money, commission, profit, or other pecuniary benefit, or the security for any advances, loan, or disbursements, is endangered by the exposure of insurable property to maritime perils; (c) Any liability to a third party may be incurred by the owner of, or other person interested in or responsible for, insurable property, by reason of maritime perils. “Maritime perils” means the perils consequent on, or incidental to, the navigation of the sea, that is to say, perils of the seas, fire, war perils, pirates, rovers, thieves, captures, seisures, restraints, and detainments of princes and peoples, jettisons, barratry, and any other perils, either of the like kind or which may be designated by the policy. INSURABLE INTEREST 4 Avoidance of wagering or gaming contracts. (1) Every contract of marine insurance by way of gaming or wagering is void. (2) A contract of marine insurance is deemed to be a gaming or wagering contract— (a) Where the assured has not an insurable interest as defined by this Act, and the contract is entered into with no expectation of acquiring such an interest; or (b) Where the policy is made “interest or no interest,” or “without further proof of interest than the policy itself,” or “without benefit of salvage to the insurer,” or subject to any other like term: Provided that, where there is no possibility of salvage, a policy may be effected without benefit of salvage to the insurer. 5 Insurable interest defined. (1) Subject to the provisions of this Act, every person has an insurable interest who is interested in a marine adventure. (2) In particular a person is interested in a marine adventure where he stands in any legal or equitable relation to the adventure or to any insurable property at risk therein, in consequence of which he may benefit by the safety or due arrival of insurable property, or may be prejudiced by its loss, or by damage thereto, or by the detention thereof, or may incur liability in respect thereof. 6 When interest must attach. (1) The assured must be interested in the subject-matter insured at the time of the loss though he need not be interested when the insurance is effected: Provided that where the subject-matter is insured “lost or not lost,” the assured may recover although he may not have acquired his interest until after the loss, unless at the time of effecting the contract of insurance the assured was aware of the loss, and the insurer was not. Page 46 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 3 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) Where the assured has no interest at the time of the loss, he cannot acquire interest by any act or election after he is aware of the loss. 7 Defeasible or contingent interest. (1) A defeasible interest is insurable, as also is a contingent interest. (2) In particular, where the buyer of goods has insured them, he has an insurable interest, notwithstanding that he might, at his election, have rejected the goods, or have treated them as at the seller’s risk, by reason of the latter’s delay in making delivery or otherwise. 8 Partial interest. A partial interest of any nature is insurable. 9 Re-insurance. (1) The insurer under a contract of marine insurance has an insurable interest in his risk, and may re-insure in respect of it. (2) Unless the policy otherwise provides, the original assured has no right or interest in respect of such re-insurance. 10 Bottomry. The lender of money on bottomry or respondentia has an insurable interest in respect of the loan. 11 Master’s and seamen’s wages. The master or any member of the crew of a ship has an insurable interest in respect of his wages. 12 Advance freight. In the case of advance freight, the person advancing the freight has an insurable interest, in so far as such freight is not repayable in case of loss. 13 Charges of insurance. The assured has an insurable interest in the charges of any insurance which he may effect. 14 Quantum of interest. (1) Where the subject-matter insured is mortgaged, the mortgagor has an insurable interest in the full value thereof, and the mortgagee has an insurable interest in respect of any sum due or to become due under the mortgage. Page 47 of 166 4 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) A mortgagee, consignee, or other person having an interest in the subject-matter insured may insure on behalf and for the benefit of other persons interested as well as for his own benefit. (3) The owner of insurable property has an insurable interest in respect of the full value thereof, notwithstanding that some third person may have agreed, or be liable, to indemnify him in case of loss. 15 Assignment of interest. Where the assured assigns or otherwise parts with his interest in the subject-matter insured, he does not thereby transfer to the assignee his rights under the contract of insurance, unless there be an express or implied agreement with the assignee to that effect. But the provisions of this section do not affect a transmission of interest by operation of law. INSURABLE VALUE 16 Measure of insurable value. Subject to any express provision or valuation in the policy, the insurable value of the subject-matter insured must be ascertained as follows:— (1) In insurance on ship, the insurable value is the value, at the commencement of the risk, of the ship, including her outfit, provisions and stores for the officers and crew, money advanced for seamen’s wages, and other disbursements (if any) incurred to make the ship fit for the voyage or adventure contemplated by the policy, plus the charges of insurance upon the whole:The insurable value, in the case of a steamship, includes also the machinery, boilers, and coals and engine stores if owned by the assured, and, in the case of a ship engaged in a special trade, the ordinary fittings requisite for that trade: (2) In insurance on freight, whether paid in advance or otherwise, the insurable value is the gross amount of the freight at the risk of the assured, plus the charges of insurance: (3) In insurance on goods or merchandise, the insurable value is the prime cost of the property insured, plus the expenses of and incidental to shipping and the charges of insurance upon the whole: (4) In insurance on any other subject-matter, the insurable value is the amount at the risk of the assured when the policy attaches, plus the charges of insurance. DISCLOSURE AND REPRESENTATIONS 17 Insurance is uberrimæ fidei. A contract of marine insurance is a contract based upon the utmost good faith, and, if the utmost good faith be not observed by either party, the contract may be avoided by the other party. Page 48 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 5 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 18 Disclosure by assured. (1) Subject to the provisions of this section, the assured must disclose to the insurer, before the contract is concluded, every material circumstance which is known to the assured, and the assured is deemed to know every circumstance which, in the ordinary course of business, ought to be known by him. If the assured fails to make such disclosure, the insurer may avoid the contract. (2) Every circumstance is material which would influence the judgment of a prudent insurer in fixing the premium, or determining whether he will take the risk. (3) In the absence of inquiry the following circumstances need not be disclosed, namely: — (a) Any circumstance which diminishes the risk; (b) Any circumstance which is known or presumed to be known to the insurer. The insurer is presumed to know matters of common notoriety or knowledge, and matters which an insurer in the ordinary course of his business, as such, ought to know; (c) Any circumstance as to which information is waived by the insurer; (d) Any circumstance which it is superfluous to disclose by reason of any express or implied warranty. (4) Whether any particular circumstance, which is not disclosed, be material or not is, in each case, a question of fact. (5) The term “circumstance” includes any communication made to, or information received by, the assured. 19 Disclosure by agent effecting insurance. Subject to the provisions of the preceding section as to circumstances which need not be disclosed, where an insurance is effected for the assured by an agent, the agent must disclose to the insurer— (a) Every material circumstance which is known to himself, and an agent to insure is deemed to know every circumstance which in the ordinary course of business ought to be known by, or to have been communicated to, him; and (b) Every material circumstance which the assured is bound to disclose, unless it come to his knowledge too late to communicate it to the agent. 20 Representations pending negotiation of contract. (1) Every material representation made by the assured or his agent to the insurer during the negotiations for the contract, and before the contract is concluded, must be true. If it be untrue the insurer may avoid the contract. (2) A representation is material which would influence the judgment of a prudent insurer in fixing the premium, or determining whether he will take the risk. (3) A representation may be either a representation as to a matter of fact, or as to a matter of expectation or belief. (4) A representation as to a matter of fact is true, if it be substantially correct, that is to say, if the difference between what is represented and what is actually correct would not be considered material by a prudent insurer. Page 49 of 166 6 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (5) A representation as to a matter of expectation or belief is true if it be made in good faith. (6) A representation may be withdrawn or corrected before the contract is concluded. (7) Whether a particular representation be material or not is, in each case, a question of fact. 21 When contract is deemed to be concluded. A contract of marine insurance is deemed to be concluded when the proposal of the assured is accepted by the insurer, whether the policy be then issued or not; and, for the purpose of showing when the proposal was accepted, reference may be made to the slip or covering note or other customary memorandum of the contract . . . F1 Annotations: Amendments (Textual) F1 Words repealed as to instruments made or executed after 1.8.1959 by Finance Act 1959 (c. 58), Sch. 8 Pt. II THE POLICY 22 Contract must be embodied in policy. Subject to the provisions of any statute, a contract of marine insurance is inadmissible in evidence unless it is embodied in a marine policy in accordance with this Act. The policy may be executed and issued either at the time when the contract is concluded, or afterwards. Annotations: Modifications etc. (not altering text) C3 S. 22 excluded by Marine and Aviation Insurance (War Risks) Act 1952 (c. 57), s. 7(1) and Finance Act 1959 (c. 58), s. 30(6)(7) 23 What policy must specify. A marine policy must specify— (1) The name of the assured, or of some person who effects the insurance on his behalf: (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F2 Annotations: Amendments (Textual) F2 S. 23(2)–(5) repealed as to instruments made or executed after 1.8.1959 by Finance Act 1959 (c. 58), Sch. 8 Pt. II Page 50 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 7 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 24 Signature of insurer. (1) A marine policy must be signed by or on behalf of the insurer, provided that in the case of a corporation the corporate seal may be sufficient, but nothing in this section shall be construed as requiring the subscription of a corporation to be under seal. (2) Where a policy is subscribed by or on behalf of two or more insurers, each subscription, unless the contrary be expressed, constitutes a distinct contract with the assured. 25 Voyage and time policies. (1) Where the contract is to insure the subject-matter “at and from,” or from one place to another or others, the policy is called a “voyage policy,” and where the contract is to insure the subject-matter for a definite period of time the policy is called a “time policy.” A contract for both voyage and time may be included in the same policy. (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F3 Annotations: Amendments (Textual) F3 S. 25(2) repealed as to instruments made or executed after 1.8.1959 by Finance Act 1959 (c. 58), Sch. 8 Pt. II 26 Designation of subject-matter. (1) The subject-matter insured must be designated in a marine policy with reasonable certainty. (2) The nature and extent of the interest of the assured in the subject-matter insured need not be specified in the policy. (3) Where the policy designates the subject-matter insured in general terms, it shall be construed to apply to the interest intended by the assured to be covered. (4) In the application of this section regard shall be had to any usage regulating the designation of the subject-matter insured. 27 Valued policy. (1) A policy may be either valued or unvalued. (2) A valued policy is a policy which specifies the agreed value of the subject-matter insured. (3) Subject to the provisions of this Act, and in the absence of fraud, the value fixed by the policy is, as between the insurer and assured, conclusive of the insurable value of the subject intended to be insured, whether the loss be total or partial. (4) Unless the policy otherwise provides, the value fixed by the policy is not conclusive for the purpose of determining whether there has been a constructive total loss. Page 51 of 166 8 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 28 Unvalued policy. An unvalued policy is a policy which does not specify the value of the subject-matter insured, but, subject to the limit of the sum insured, leaves the insurable value to be subsequently ascertained, in the manner herein-before specified. 29 Floating policy by ship or ships. (1) A floating policy is a policy which describes the insurance in general terms, and leaves the name of the ship or ships and other particulars to be defined by subsequent declaration. (2) The subsequent declaration or declarations may be made by indorsement on the policy, or in other customary manner. (3) Unless the policy otherwise provides, the declarations must be made in the order of dispatch or shipment. They must, in the case of goods, comprise all consignments within the terms of the policy, and the value of the goods or other property must be honestly stated, but an omission or erroneous declaration may be rectified even after loss or arrival, provided the omission or declaration was made in good faith. (4) Unless the policy otherwise provides, where a declaration of value is not made until after notice of loss or arrival, the policy must be treated as an unvalued policy as regards the subject-matter of that declaration. 30 Construction of terms in policy. (1) A policy may be in the form in the First Schedule to this Act. (2) Subject to the provisions of this Act, and unless the context of the policy otherwise requires, the terms and expressions mentioned in the First Schedule to this Act shall be construed as having the scope and meaning in that schedule assigned to them. 31 Premium to be arranged. (1) Where an insurance is effected at a premium to be arranged, and no arrangement is made, a reasonable premium is payable. (2) Where an insurance is effected on the terms that an additional premium is to be arranged in a given event, and that event happens but no arrangement is made, then a reasonable additional premium is payable. DOUBLE INSURANCE 32 Double insurance. (1) Where two or more policies are effected by or on behalf of the assured on the same adventure and interest or any part thereof, and the sums insured exceed the indemnity allowed by this Act, the assured is said to be over-insured by double insurance. (2) Where the assured is over-insured by double insurance— (a) The assured, unless the policy otherwise provides, may claim payment from the insurers in such order as he may think fit, provided that he is not entitled to receive any sum in excess of the indemnity allowed by this Act; Page 52 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 9 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (b) Where the policy under which the assured claims is a valued policy, the assured must give credit as against the valuation for any sum received by him under any other policy without regard to the actual value of the subject-matter insured; (c) Where the policy under which the assured claims is an unvalued policy he must give credit, as against the full insurable value, for any sum received by him under any other policy: (d) Where the assured receives any sum in excess of the indemnity allowed by this Act, he is deemed to hold such sum in trust for the insurers, according to their right of contribution among themselves. WARRANTIES, &C. 33 Nature of warranty. (1) A warranty, in the following sections relating to warranties, means a promissory warranty, that is to say, a warranty by which the assured undertakes that some particular thing shall or shall not be done, or that some condition shall be fulfilled, or whereby he affirms or negatives the existence of a particular state of facts. (2) A warranty may be express or implied. (3) A warranty, as above defined, is a condition which must be exactly complied with, whether it be material to the risk or not. If it be not so complied with, then, subject to any express provision in the policy, the insurer is discharged from liability as from the date of the breach of warranty, but without prejudice to any liability incurred by him before that date. 34 When breach of warranty excused. (1) Non-compliance with a warranty is excused when, by reason of a change of circumstances, the warranty ceases to be applicable to the circumstances of the contract, or when compliance with the warranty is rendered unlawful by any subsequent law. (2) Where a warranty is broken, the assured cannot avail himself of the defence that the breach has been remedied, and the warranty complied with, before loss. (3) A breach of warranty may be waived by the insurer. 35 Express warranties. (1) An express warranty may be in any form of words from which the intention to warrant is to be inferred. (2) An express warranty must be included in, or written upon, the policy, or must be contained in some document incorporated by reference into the policy. (3) An express warranty does not exclude an implied warranty, unless it be inconsistent therewith. Page 53 of 166 10 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 36 Warranty of neutrality. (1) Where insurable property, whether ship or goods, is expressly warranted neutral, there is an implied condition that the property shall have a neutral character at the commencement of the risk, and that, so far as the assured can control the matter, its neutral character shall be preserved during the risk. (2) Where a ship is expressly warranted “neutral” there is also an implied condition that, so far as the assured can control the matter, she shall be properly documented, that is to say, that she shall carry the necessary papers to establish her neutrality, and that she shall not falsify or suppress her papers, or use simulated papers. If any loss occurs through breach of this condition, the insurer may avoid the contract. 37 No implied warranty of nationality. There is no implied warranty as to the nationality of a ship, or that her nationality shall not be changed during the risk. 38 Warranty of good safety. Where the subject-matter insured is warranted “well” or “in good safety” on a particular day, it is sufficient if it be safe at any time during that day. 39 Warranty of seaworthiness of ship. (1) In a voyage policy there is an implied warranty that at the commencement of the voyage the ship shall be seaworthy for the purpose of the particular adventure insured. (2) Where the policy attaches while the ship is in port, there is also an implied warranty that she shall, at the commencement of the risk, be reasonably fit to encounter the ordinary perils of the port. (3) Where the policy relates to a voyage which is performed in different stages, during which the ship requires different kinds of or further preparation or equipment, there is an implied warranty that at the commencement of each stage the ship is seaworthy in respect of such preparation or equipment for the purposes of that stage. (4) A ship is deemed to be seaworthy when she is reasonably fit in all respects to encounter the ordinary perils of the seas of the adventure insured. (5) In a time policy there is no implied warranty that the ship shall be seaworthy at any stage of the adventure, but where, with the privity of the assured, the ship is sent to sea in an unseaworthy state, the insurer is not liable for any loss attributable to unseaworthiness. 40 No implied warranty that goods are seaworthy. (1) In a policy on goods or other moveables there is no implied warranty that the goods or moveables are seaworthy. (2) In a voyage policy on goods or other moveables there is an implied warranty that at the commencement of the voyage the ship is not only seaworthy as a ship, but also that she is reasonably fit to carry the goods or other moveables to the destination contemplated by the policy. Page 54 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 11 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 41 Warranty of legality. There is an implied warranty that the adventure insured is a lawful one, and that, so far as the assured can control the matter, the adventure shall be carried out in a lawful manner. THE VOYAGE 42 Implied condition as to commencement of risk. (1) Where the subject-matter is insured by a voyage policy “at and from” or “from” a particular place, it is not necessary that the ship should be at that place when the contract is concluded, but there is an implied condition that the adventure shall be commenced within a reasonable time, and that if the adventure be not so commenced the insurer may avoid the contract. (2) The implied condition may be negatived by showing that the delay was caused by circumstances known to the insurer before the contract was concluded, or by showing that he waived the condition. 43 Alteration of port of departure. Where the place of departure is specified by the policy, and the ship instead of sailing from that place sails from any other place, the risk does not attach. 44 Sailing for different destination. Where the destination is specified in the policy, and the ship, instead of sailing for that destination, sails for any other destination, the risk does not attach. 45 Change of voyage. (1) Where, after the commencement of the risk, the destination of the ship is voluntarily changed from the destination contemplated by the policy, there is said to be a change of voyage. (2) Unless the policy otherwise provides, where there is a change of voyage, the insurer is discharged from liability as from the time of change, that is to say, as from the time when the determination to change it is manifested; and it is immaterial that the ship may not in fact have left the course of voyage contemplated by the policy when the loss occurs. 46 Deviation. (1) Where a ship, without lawful excuse, deviates from the voyage contemplated by the policy, the insurer is discharged from liability as from the time of deviation, and it is immaterial that the ship may have regained her route before any loss occurs. (2) There is a deviation from the voyage contemplated by the policy— (a) Where the course of the voyage is specifically designated by the policy, and that course is departed from; or (b) Where the course of the voyage is not specifically designated by the policy, but the usual and customary course is departed from. Page 55 of 166 12 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (3) The intention to deviate is immaterial; there must be a deviation in fact to discharge the insurer from his liability under the contract. 47 Several ports of discharge. (1) Where several ports of discharge are specified by the policy, the ship may proceed to all or any of them, but, in the absence of any usage or sufficient cause to the contrary, she must proceed to them, or such of them as she goes to, in the order designated by the policy. If she does not there is a deviation. (2) Where the policy is to “ports of discharge,” within a given area, which are not named, the ship must, in the absence of any usage or sufficient cause to the contrary, proceed to them, or such of them as she goes to, in their geographical order. If she does not there is a deviation. 48 Delay in voyage. In the case of a voyage policy, the adventure insured must be prosecuted throughout its course with reasonable dispatch, and, if without lawful excuse it is not so prosecuted, the insurer is discharged from liability as from the time when the delay became unreasonable. 49 Excuses for deviation or delay. (1) Deviation or delay in prosecuting the voyage contemplated by the policy is excused— (a) Where authorised by any special term in the policy; or (b) Where caused by circumstances beyond the control of the master and his employer; or (c) Where reasonably necessary in order to comply with an express or implied warranty; or (d) Where reasonably necessary for the safety of the ship or subject-matter insured; or (e) For the purpose of saving human life, or aiding a ship in distress where human life may be in danger; or (f) Where reasonably necessary for the purpose of obtaining medical or surgical aid for any person on board the ship; or (g) Where caused by the barratrous conduct of the master or crew, if barratry be one of the perils insured against. (2) When the cause excusing the deviation or delay ceases to operate, the ship must resume her course, and prosecute her voyage, with reasonable dispatch. ASSIGNMENT OF POLICY 50 When and how policy is assignable. (1) A marine policy is assignable unless it contains terms expressly prohibiting assignment. It may be assigned either before or after loss. (2) Where a marine policy has been assigned so as to pass the beneficial interest in such policy, the assignee of the policy is entitled to sue thereon in his own name; and the Page 56 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 13 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) defendant is entitled to make any defence arising out of the contract which he would have been entitled to make if the action had been brought in the name of the person by or on behalf of whom the policy was effected. (3) A marine policy may be assigned by indorsement thereon or in other customary manner. 51 Assured who has no interest cannot assign. Where the assured has parted with or lost his interest in the subject-matter insured, and has not, before or at the time of so doing, expressly or impliedly agreed to assign the policy, any subsequent assignment of the policy is inoperative: Provided that nothing in this section affects the assignment of a policy after loss. THE PREMIUM 52 When premium payable. Unless otherwise agreed, the duty of the assured or his agent to pay the premium, and the duty of the insurer to issue the policy to the assured or his agent, are concurrent conditions, and the insurer is not bound to issue the policy until payment or tender of the premium. 53 Policy effected through broker. (1) Unless otherwise agreed, where a marine policy is effected on behalf of the assured by a broker, the broker is directly responsible to the insurer for the premium, and the insurer is directly responsible to the assured for the amount which may be payable in respect of losses, or in respect of returnable premium. (2) Unless otherwise agreed, the broker has, as against the assured, a lien upon the policy for the amount of the premium and his charges in respect of effecting the policy; and, where he has dealt with the person who employs him as a principal, he has also a lien on the policy in respect of any balance on any insurance account which may be due to him from such person, unless when the debt was incurred he had reason to believe that such person was only an agent. 54 Effect of receipt on policy. Where a marine policy effected on behalf of the assured by a broker acknowledges the receipt of the premium, such acknowledgement is, in the absence of fraud, conclusive as between the insurer and the assured, but not as between the insurer and broker. LOSS AND ABANDONMENT 55 Included and excluded losses. (1) Subject to the provisions of this Act, and unless the policy otherwise provides, the insurer is liable for any loss proximately caused by a peril insured against, but, subject as aforesaid, he is not liable for any loss which is not proximately caused by a peril insured against. (2) In particular— Page 57 of 166 14 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (a) The insurer is not liable for any loss attributable to the wilful misconduct of the assured, but, unless the policy otherwise provides, he is liable for any loss proximately caused by a peril insured against, even though the loss would not have happened but for the misconduct or negligence of the master or crew; (b) Unless the policy otherwise provides, the insurer on ship or goods is not liable for any loss proximately caused by delay, although the delay be caused by a peril insured against; (c) Unless the policy otherwise provides, the insurer is not liable for ordinary wear and tear, ordinary leakage and breakage, inherent vice or nature of the subject-matter insured, or for any loss proximately caused by rats or vermin, or for any injury to machinery not proximately caused by maritime perils. 56 Partial and total loss. (1) A loss may be either total or partial. Any loss other than a total loss, as hereinafter defined, is a partial loss. (2) A total loss may be either an actual total loss, or a constructive total loss. (3) Unless a different intention appears from the terms of the policy, an insurance against total loss includes a constructive, as well as an actual, total loss. (4) Where the assured brings an action for a total loss and the evidence proves only a partial loss, he may, unless the policy otherwise provides, recover for a partial loss. (5) Where goods reach their destination in specie, but by reason of obliteration of marks, or otherwise, they are incapable of identification, the loss, if any, is partial, and not total. 57 Actual total loss. (1) Where the subject-matter insured is destroyed, or so damaged as to cease to be a thing of the kind insured, or where the assured is irretrievably deprived thereof, there is an actual total loss. (2) In the case of an actual total loss no notice of abandonment need be given. 58 Missing ship. Where the ship concerned in the adventure is missing, and after the lapse of a reasonable time no news of her has been received, an actual total loss may be presumed. 59 Effect of transhipment, &c. Where, by a peril insured against, the voyage is interrupted at an intermediate port or place, under such circumstances as, apart from any special stipulation in the contract of affreightment, to justify the master in landing and reshipping the goods or other moveables, or in transhipping them, and sending them on to their destination, the liability of the insurer continues, notwithstanding the landing or transhipment. Page 58 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 15 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 60 Constructive total loss defined. (1) Subject to any express provision in the policy, there is a constructive total loss where the subject-matter insured is reasonably abandoned on account of its actual total loss appearing to be unavoidable, or because it could not be preserved from actual total loss without an expenditure which would exceed its value when the expenditure had been incurred. (2) In particular, there is a constructive total loss— (i) Where the assured is deprived of the possession of his ship or goods by a peril insured against, and (a) it is unlikely that he can recover the ship or goods, as the case may be, or (b) the cost of recovering the ship or goods, as the case may be, would exceed their value when recovered; or (ii) In the case of damage to a ship, where she is so damaged by a peril insured against that the cost of repairing the damage would exceed the value of the ship when repaired. In estimating the cost of repairs, no deduction is to be made in respect of general average contributions to those repairs payable by other interests, but account is to be taken of the expense of future salvage operations and of any future general average contributions to which the ship would be liable if repaired; or (iii) In the case of damage to goods, where the cost of repairing the damage and forwarding the goods to their destination would exceed their value on arrival. 61 Effect of constructive total loss. Where there is a constructive total loss the assured may either treat the loss as a partial loss, or abandon the subject-matter insured to the insurer and treat the loss as if it were an actual total loss. 62 Notice of abandonment. (1) Subject to the provisions of this section, where the assured elects to abandon the subject-matter insured to the insurer, he must give notice of abandonment. If he fails to do so the loss can only be treated as a partial loss. (2) Notice of abandonment may be given in writing, or by word of mouth, or partly in writing and partly by word of mouth, and may be given in any terms which indicate the intention of the assured to abandon his insured interest in the subject-matter insured unconditionally to the insurer. (3) Notice of abandonment must be given with reasonable diligence after the receipt of reliable information of the loss, but where the information is of a doubtful character the assured is entitled to a reasonable time to make inquiry. (4) Where notice of abandonment is properly given, the rights of the assured are not prejudiced by the fact that the insurer refuses to accept the abandonment. (5) The acceptance of an abandonment may be either express or implied from the conduct of the insurer. The mere silence of the insurer after notice is not an acceptance. (6) Where notice of abandonment is accepted the abandonment is irrevocable. The acceptance of the notice conclusively admits liability for the loss and the sufficiency of the notice. Page 59 of 166 16 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (7) Notice of abandonment is unnecessary where, at the time when the assured receives information of the loss, there would be no possibility of benefit to the insurer if notice were given to him. (8) Notice of abandonment may be waived by the insurer. (9) Where an insurer has re-insured his risk, no notice of abandonment need be given by him. 63 Effect of abandonment. (1) Where there is a valid abandonment the insurer is entitled to take over the interest of the assured in whatever may remain of the subject-matter insured, and all proprietary rights incidental thereto. (2) Upon the abandonment of a ship, the insurer thereof is entitled to any freight in course of being earned, and which is earned by her subsequent to the casualty causing the loss, less the expenses of earning it incurred after the casualty; and, where the ship is carrying the owner’s goods, the insurer is entitled to a reasonable remuneration for the carriage of them subsequent to the casualty causing the loss. PARTIAL LOSSES (INCLUDING SALVAGE AND GENERAL AVERAGE AND PARTICULAR CHARGES) 64 Particular average loss. (1) A particular average loss is a partial loss of the subject-matter insured, caused by a peril insured against, and which is not a general average loss. (2) Expenses incurred by or on behalf of the assured for the safety or preservation of the subject-matter insured, other than general average and salvage charges, are called particular charges. Particular charges are not included in particular average. 65 Salvage charges. (1) Subject to any express provision in the policy, salvage charges incurred in preventing a loss by perils insured against may be recovered as a loss by those perils. (2) “Salvage charges” means the charges recoverable under maritime law by a salvor independently of contract. They do not include the expenses of services in the nature of salvage rendered by the assured or his agents, or any person employed for hire by them, for the purpose of averting a peril insured against. Such expenses, where properly incurred, may be recovered as particular charges or as a general average loss, according to the circumstances under which they were incurred. 66 General average loss. (1) A general average loss is a loss caused by or directly consequential on a general average act. It includes a general average expenditure as well as a general average sacrifice. Page 60 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 17 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (2) There is a general average act where any extraordinary sacrifice or expenditure is voluntarily and reasonably made or incurred in time of peril for the purpose of preserving the property imperilled in the common adventure. (3) Where there is a general average loss, the party on whom it falls is entitled, subject to the conditions imposed by maritime law, to a rateable contribution from the other parties interested, and such contribution is called a general average contribution. (4) Subject to any express provision in the policy, where the assured has incurred a general average expenditure, he may recover from the insurer in respect of the proportion of the loss which falls upon him; and, in the case of a general average sacrifice, he may recover from the insurer in respect of the whole loss without having enforced his right of contribution from the other parties liable to contribute. (5) Subject to any express provision in the policy, where the assured has paid, or is liable to pay, a general average contribution in respect of the subject insured, he may recover therefor from the insurer. (6) In the absence of express stipulation, the insurer is not liable for any general average loss or contribution where the loss was not incurred for the purpose of avoiding, or in connexion with the avoidance of, a peril insured against. (7) Where ship, freight, and cargo, or any two of those interests, are owned by the same assured, the liability of the insurer in respect of general average losses or contributions is to be determined as if those subjects were owned by different persons. MEASURE OF INDEMNITY 67 Extent of liability of insurer for loss. (1) The sum which the assured can recover in respect of a loss on a policy by which he is insured, in the case of an unvalued policy to the full extent of the insurable value, or, in the case of a valued policy to the full extent of the value fixed by the policy is called the measure of indemnity. (2) Where there is a loss recoverable under the policy, the insurer, or each insurer if there be more than one, is liable for such proportion of the measure of indemnity as the amount of his subscription bears to the value fixed by the policy in the case of a valued policy, or to the insurable value in the case of an unvalued policy. 68 Total loss. Subject to the provisions of this Act and to any express provision in the policy, where there is a total loss of the subject-matter insured,— (1) If the policy be a valued policy, the measure of indemnity is the sum fixed by the policy: (2) If the policy be an unvalued policy, the measure of indemnity is the insurable value of the subject-matter insured. Page 61 of 166 18 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 69 Partial loss of ship. Where a ship is damaged, but is not totally lost, the measure of indemnity, subject to any express provision in the policy, is as follows:— (1) Where the ship has been repaired, the assured is entitled to the reasonable cost of the repairs, less the customary deductions, but not exceeding the sum insured in respect of any one casualty: (2) Where the ship has been only partially repaired, the assured is entitled to the reasonable cost of such repairs, computed as above, and also to be indemnified for the reasonable depreciation, if any, arising from the unrepaired damage, provided that the aggregate amount shall not exceed the cost of repairing the whole damage, computed as above: (3) Where the ship has not been repaired, and has not been sold in her damaged state during the risk, the assured is entitled to be indemnified for the reasonable depreciation arising from the unrepaired damage, but not exceeding the reasonable cost of repairing such damage, computed as above. 70 Partial loss of freight. Subject to any express provision in the policy, where there is a partial loss of freight, the measure of indemnity is such proportion of the sum fixed by the policy in the case of a valued policy, or of the insurable value in the case of an unvalued policy, as the proportion of freight lost by the assured bears to the whole freight at the risk of the assured under the policy. 71 Partial loss of goods, merchandise, &c. Where there is a partial loss of goods, merchandise, or other moveables, the measure of indemnity, subject to any express provision in the policy, is as follows:— (1) Where part of the goods, merchandise or other moveables insured by a valued policy is totally lost, the measure of indemnity is such proportion of the sum fixed by the policy as the insurable value of the part lost bears to the insurable value of the whole, ascertained as in the case of an unvalued policy: (2) Where part of the goods, merchandise, or other moveables insured by an unvalued policy is totally lost, the measure of indemnity is the insurable value of the part lost, ascertained as in case of total loss: (3) Where the whole or any part of the goods or merchandise insured has been delivered damaged at its destination, the measure of indemnity is such proportion of the sum fixed by the policy in the case of a valued policy, or of the insurable value in the case of an unvalued policy, as the difference between the gross sound and damaged values at the place of arrival bears to the gross sound value: (4) “Gross value” means the wholesale price, or, if there be no such price, the estimated value, with, in either case, freight, landing charges, and duty paid beforehand; provided that, in the case of goods or merchandise customarily sold in bond, the bonded price is deemed to be the gross value. “Gross proceeds” means the actual price obtained at a sale where all charges on sale are paid by the sellers. Page 62 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 19 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 72 Apportionment of valuation. (1) Where different species of property are insured under a single valuation, the valuation must be apportioned over the different species in proportion to their respective insurable values, as in the case of an unvalued policy. The insured value of any part of a species is such proportion of the total insured value of the same as the insurable value of the part bears to the insurable value of the whole, ascertained in both cases as provided by this Act. (2) Where a valuation has to be apportioned, and particulars of the prime cost of each separate species, quality, or description of goods cannot be ascertained, the division of the valuation may be made over the net arrived sound values of the different species, qualities, or descriptions of goods. 73 General average contributions and salvage charges. (1) Subject to any express provision in the policy, where the assured has paid, or is liable for, any general average contribution, the measure of indemnity is the full amount of such contribution, if the subject-matter liable to contribution is insured for its full contributory value; but, if such subject-matter be not insured for its full contributory value, or if only part of it be insured, the indemnity payable by the insurer must be reduced in proportion to the under insurance, and where there has been a particular average loss which constitutes a deduction from the contributory value, and for which the insurer is liable, that amount must be deducted from the insured value in order to ascertain what the insurer is liable to contribute. (2) Where the insurer is liable for salvage charges the extent of his liability must be determined on the like principle. 74 Liabilities to third parties. Where the assured has effected an insurance in express terms against any liability to a third party, the measure of indemnity, subject to any express provision in the policy, is the amount paid or payable by him to such third party in respect of such liability. 75 General provisions as to measure of indemnity. (1) Where there has been a loss in respect of any subject-matter not expressly provided for in the foregoing provisions of this Act, the measure of indemnity shall be ascertained, as nearly as may be, in accordance with those provisions, in so far as applicable to the particular case. (2) Nothing in the provisions of this Act relating to the measure of indemnity shall affect the rules relating to double insurance, or prohibit the insurer from disproving interest wholly or in part, or from showing that at the time of the loss the whole or any part of the subject-matter insured was not at risk under the policy. 76 Particular average warranties. (1) Where the subject-matter insured is warranted free from particular average, the assured cannot recover for a loss of part, other than a loss incurred by a general average sacrifice, unless the contract contained in the policy be apportionable; but, if the Page 63 of 166 20 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) contract be apportionable, the assured may recover for a total loss of any apportionable part. (2) Where the subject-matter insured is warranted free from particular average, either wholly or under a certain percentage, the insurer is nevertheless liable for salvage charges, and for particular charges and other expenses properly incurred pursuant to the provisions of the suing and labouring clause in order to avert a loss insured against. (3) Unless the policy otherwise provides, where the subject-matter insured is warranted free from particular average under a specified percentage, a general average loss cannot be added to a particular average loss to make up the specified percentage. (4) For the purpose of ascertaining whether the specified percentage has been reached, regard shall be had only to the actual loss suffered by the subject-matter insured. Particular charges and the expenses of and incidental to ascertaining and proving the loss must be excluded. 77 Successive losses. (1) Unless the policy otherwise provides, and subject to the provisions of this Act, the insurer is liable for successive losses, even though the total amount of such losses may exceed the sum insured. (2) Where, under the same policy, a partial loss, which has not been repaired or otherwise made good, is followed by a total loss, the assured can only recover in respect of the total loss: Provided that nothing in this section shall affect the liability of the insurer under the suing and labouring clause. 78 Suing and labouring clause. (1) Where the policy contains a suing and labouring clause, the engagement thereby entered into is deemed to be supplementary to the contract of insurance, and the assured may recover from the insurer any expenses properly incurred pursuant to the clause, notwithstanding that the insurer may have paid for a total loss, or that the subject-matter may have been warranted free from particular average, either wholly or under a certain percentage. (2) General average losses and contributions and salvage charges, as defined by this Act, are not recoverable under the suing and labouring clause. (3) Expenses incurred for the purpose of averting or diminishing any loss not covered by the policy are not recoverable under the suing and labouring clause. (4) It is the duty of the assured and his agents, in all cases, to take such measures as may be reasonable for the purpose of averting or minimising a loss. RIGHTS OF INSURER ON PAYMENT 79 Right of subrogation. (1) Where the insurer pays for a total loss, either of the whole, or in the case of goods of any apportionable part, of the subject-matter insured, he thereupon becomes entitled to take over the interest of the assured in whatever may remain of the subject-matter Page 64 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 21 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) so paid for, and he is thereby subrogated to all the rights and remedies of the assured in and in respect of that subject-matter as from the time of the casualty causing the loss. (2) Subject to the foregoing provisions, where the insurer pays for a partial loss, he acquires no title to the subject-matter insured, or such part of it as may remain, but he is thereupon subrogated to all rights and remedies of the assured in and in respect of the subject-matter insured as from the time of the casualty causing the loss, in so far as the assured has been indemnified, according to this Act, by such payment for the loss. 80 Right of contribution. (1) Where the assured is over-insured by double insurance, each insurer is bound, as between himself and the other insurers, to contribute rateably to the loss in proportion to the amount for which he is liable under his contract. (2) If any insurer pays more than his proportion of the loss, he is entitled to maintain an action for contribution against the other insurers, and is entitled to the like remedies as a surety who has paid more than his proportion of the debt. 81 Effect of under insurance. Where the assured is insured for an amount less than the insurable value or, in the case of a valued policy, for an amount less than the policy valuation, he is deemed to be his own insurer in respect of the uninsured balance. RETURN OF PREMIUM 82 Enforcement of return. Where the premium or a proportionate part thereof is, by this Act, declared to be returnable,— (a) If already paid, it may be recovered by the assured from the insurer; and (b) If unpaid, it may be retained by the assured or his agent. 83 Return by agreement. Where the policy contains a stipulation for the return of the premium, or a proportionate part thereof, on the happening of a certain event, and that event happens, the premium, or, as the case may be, the proportionate part thereof, is thereupon returnable to the assured. 84 Return for failure of consideration. (1) Where the consideration for the payment of the premium totally fails, and there has been no fraud or illegality on the part of the assured or his agents, the premium is thereupon returnable to the assured. (2) Where the consideration for the payment of the premium is apportionable and there is a total failure of any apportionable part of the consideration, a proportionate part of the premium is, under the like conditions, thereupon returnable to the assured. (3) In particular— Page 65 of 166 22 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) (a) Where the policy is void, or is avoided by the insurer as from the commencement of the risk, the premium is returnable, provided that there has been no fraud or illegality on the part of the assured; but if the risk is not apportionable, and has once attached, the premium is not returnable: (b) Where the subject-matter insured, or part thereof, has never been imperilled, the premium, or, as the case may be, a proportionate part thereof, is returnable: Provided that where the subject-matter has been insured “lost or not lost” and has arrived in safety at the time when the contract is concluded, the premium is not returnable unless, at such time, the insurer knew of the safe arrival. (c) Where the assured has no insurable interest throughout the currency of the risk, the premium is returnable, provided that this rule does not apply to a policy effected by way of gaming or wagering; (d) Where the assured has a defeasible interest which is terminated during the currency of the risk, the premium is not returnable; (e) Where the assured has over-insured under an unvalued policy, a proportionate part of the premium is returnable; (f) Subject to the foregoing provisions, where the assured has over-insured by double insurance, a proportionate part of the several premiums is returnable: Provided that, if the policies are effected at different times, and any earlier policy has at any time borne the entire risk, or if a claim has been paid on the policy in respect of the full sum insured thereby, no premium is returnable in respect of that policy, and when the double insurance is effected knowingly by the assured no premium is returnable. MUTUAL INSURANCE 85 Modification of Act in case of mutual insurance. (1) Where two or more persons mutually agree to insure each other against marine losses there is said to be a mutual insurance. (2) The provisions of this Act relating to the premium do not apply to mutual insurance, but a guarantee, or such other arrangement as may be agreed upon, may be substituted for the premium. (3) The provisions of this Act, in so far as they may be modified by the agreement of the parties, may in the case of mutual insurance be modified by the terms of the policies issued by the association, or by the rules and regulations of the association. (4) Subject to the exceptions mentioned in this section, the provisions of this Act apply to a mutual insurance. SUPPLEMENTAL 86 Ratification by assured. Where a contract of marine insurance is in good faith effected by one person on behalf of another, the person on whose behalf it is effected may ratify the contract even after he is aware of a loss. Page 66 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 23 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) 87 Implied obligations varied by agreement or usage. (1) Where any right, duty, or liability would arise under a contract of marine insurance by implication of law, it may be negatived or varied by express agreement, or by usage, if the usage be such as to bind both parties to the contract. (2) The provisions of this section extend to any right, duty, or liability declared by this Act which may be lawfully modified by agreement. 88 Reasonable time, &c. a question of fact. Where by this Act any reference is made to reasonable time, reasonable premium, or reasonable diligence, the question what is reasonable is a question of fact. 89 Slip as evidence. Where there is a duly stamped policy, reference may be made, as heretofore, to the slip or covering note, in any legal proceeding. 90 Interpretation of terms. In this Act, unless the context or subject-matter otherwise requires,— “Action” includes counter-claim and set off: “Freight” includes the profit derivable by a shipowner from the employment of his ship to carry his own goods or moveables, as well as freight payable by a third party, but does not include passage money: “Moveables” means any moveable tangible property, other than the ship, and includes money, valuable securities, and other documents: “Policy” means a marine policy. 91 Savings. (1) Nothing in this Act, or in any repeal effected thereby, shall affect— (a) The provisions of the M1Stamp Act 1891, or any enactment for the time being in force relating to the revenue; (b) The provisions of the M2Companies Act 1862, or any enactment amending or substituted for the same; (c) The provisions of any statute not expressly repealed by this Act. (2) The rules of the common law including the law merchant, save in so far as they are inconsistent with the express provisions of this Act, shall continue to apply to contracts of marine insurance. Annotations: Marginal Citations M1 1891 c. 39. M2 1862 c. 89. 92, 93. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F4 Page 67 of 166 24 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Annotations: Amendments (Textual) F4 Ss. 92, 93, Sch. 2 repealed by Statute Law Revision Act 1927 (c. 42) 94 Short title. This Act may be cited as the Marine Insurance Act 1906. Page 68 of 166 Marine Insurance Act 1906 (c. 41) FIRST SCHEDULE – Form of Policy Document Generated: 2012-05-29 25 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) S C H E D U L E S FIRST SCHEDULE Section 30. FORM OF POLICY Lloyd’s S.G. policy Be it known that as well in own name as for and in the name and names of all and every other person or persons to whom the same doth, may, or shall appertain, in part or in all doth make assurance and cause and them, and every of them, to be insured lost or not lost, at and from Upon any kind of goods and merchandises, and also upon the body, tackle, apparel, ordnance, munition, artillery, boat, and other furniture, of and in the good ship or vessel called the whereof is master under God, for this present voyage, or whosoever else shall go for master in the said ship, or by whatsoever other name or names the said ship, or the master thereof, is or shall be named or called; beginning the adventure upon the said goods and merchandises from the loading thereof aboard the said ship. upon the said ship, &c. and so shall continue and endure, during her abode there, upon the said ship, &c. And further, until the said ship, with all her ordnance, tackle, apparel, &c., and goods and merchandises whatsoever shall be arrived at upon the said ship, &c., until she hath moored at anchor twenty-four hours in good safety; and upon the goods and merchandises, until the same be there discharged and safely landed. And it shall be lawful for the said ship, &c., in this voyage, to proceed and sail to and touch and stay at any ports or places whatsoever without prejudice to this insurance. The said ship, &c., goods and merchandises, &c., for so much as concerns the assured by agreement between the assured and assurers in this policy, are and shall be valued at Touching the adventures and perils which we the assurers are contented to bear and do take upon us in this voyage: they are of the seas, men of war, fire, enemies, pirates, rovers, thieves, jettisons, letters of mart and countermart, surprisals, takings at sea, arrests, restraints, and detainments of all kings, princes, and people, of what nation, condition, or quality soever, barratry of the master and mariners, and of all other perils, losses, and misfortunes, that have or shall come to the hurt, detriment, or damage of the said goods and merchandises, and ship, &c., or any part thereof. And in case of any loss or misfortune it shall be lawful to the assured, their factors, servants and assigns, to sue, labour, and travel for, in and about the defence, safeguards, and recovery of the said goods and merchandises, and ship, &c., or any part thereof, without prejudice to this insurance; to the charges whereof we, the assurers, will contribute each one according to the rate and quantity of his sum herein assuredAnd it is especially declared and agreed that no acts of the insurer or insured in recovering, saving, or preserving the property insured shall be considered as a waiver, or acceptance of abandonment. And it is agreed by us, the insurers, that this writing or policy of assurance shall be of as much force and effect as the surest writing or policy of assurance heretofore made in Lombard Street, or in the Royal Exchange, or elsewhere in London. And so we, the assurers, are contented, and do hereby promise and bind ourselves, each one for his own part, our heirs, executors, and goods to the assured, their executors, Page 69 of 166 26 Marine Insurance Act 1906 (c. 41) FIRST SCHEDULE – Form of Policy Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) administrators, and assigns, for the true performance of the premises, confessing ourselves paid the consideration due unto us for this assurance by the assured, at and after the rate of In Witness whereof we, the assurers, have subscribed our names and sums assured in London. N.B.—Corn, fish, salt, fruit, flour, and seed are warranted free from average, unless general, or the ship be stranded—sugar, tobacco, hemp, flax, hides and skins are warranted free from average, under five pounds per cent., and all other goods, also the ship and freight, are warranted free from average, under three pounds per cent. unless general, or the ship be stranded. RULES FOR CONSTRUCTION OF POLICY The following are the rules referred to by this Act for the construction of a policy in the above or other like form, where the context does not otherwise require:— Lost or not lost. 1 Where the subject-matter is insured “lost or not lost,” and the loss has occurred before the contract is concluded, the risk attaches unless, at such time the assured was aware of the loss, and the insurer was not. From. 2 Where the subject-matter is insured “from” a particular place, the risk does not attach until the ship starts on the voyage insured. At and from. 3 (a) Where a ship is insured “at and from” a particular place, and she is at that place in good safety when the contract is concluded, the risk attaches immediately. (b) If she be not at that place when the contract is concluded, the risk attaches as soon as she arrives there in good safety, and, unless the policy otherwise provides, it is immaterial that she is covered by another policy for a specified time after arrival. (c) Where chartered freight is insured “at and from” a particular place, and the ship is at that place in good safety when the contract is concluded the risk attaches immediately. If she be not there when the contract is concluded, the risk attaches as soon as she arrives there in good safety. (d) Where freight, other than chartered freight, is payable without special conditions and is insured “at and from” a particular place, the risk attaches pro rata as the goods or merchandise are shipped; provided that if there be cargo in readiness which belongs to the shipowner, or which some other person has contracted with him to ship, the risk attaches as soon as the ship is ready to receive such cargo. From the loading thereof. 4 Where goods or other moveables are insured “from the loading thereof,” the risk does not attach until such goods or moveables are actually on board, and the insurer is not liable for them while in transit from the shore to the ship. Page 70 of 166 Marine Insurance Act 1906 (c. 41) FIRST SCHEDULE – Form of Policy Document Generated: 2012-05-29 27 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Safely landed. 5 Where the risk on goods or other moveables continues until they are “safely landed,” they must be landed in the customary manner and within a reasonable time after arrival at the port of discharge, and if they are not so landed the risk ceases. Touch and stay. 6 In the absence of any further licence or usage, the liberty to touch and stay “at any port or place whatsoever” does not authorise the ship to depart from the course of her voyage from the port of departure to the port of destination. Perils of the seas. 7 The term “perils of the seas” refers only to fortuitous accidents or casualties of the seas. It does not include the ordinary action of the winds and waves. Pirates. 8 The term “pirates” includes passengers who mutiny and rioters who attack the ship from the shore. Annotations: Modifications etc. (not altering text) C4 Sch. 1 rules 8, 10 amended by Public Order Act 1986 (c. 64, SIF 39:2), s. 10(2) Thieves. 9 The term “thieves” does not cover clandestine theft or a theft committed by any one of the ship’s company, whether crew or passengers. Restraint of princes. 10 The term “arrests, &c., of kings, princes, and people” refers to political or executive acts, and does not include a loss caused by riot or by ordinary judicial process. Annotations: Modifications etc. (not altering text) C5 Sch. 1 rules 8, 10 amended by Public Order Act 1986 (c. 64, SIF 39:2), s. 10(2) Barratry. 11 The term “barratry” includes every wrongful act wilfully committed by the master or crew to the prejudice of the owner, or, as the case may be, the charterer. All other perils. 12 The term “all other perils” includes only perils similar in kind to the perils specifically mentioned in the policy. Page 71 of 166 28 Marine Insurance Act 1906 (c. 41) SECOND SCHEDULE – Document Generated: 2012-05-29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. (See end of Document for details) Average unless general. 13 The term “average unless general” means a partial loss of the subject-matter insured other than a general average loss, and does not include “particular charges.” Stranded. 14 Where the ship has stranded, the insurer is liable for the excepted losses, although the loss is not attributable to the stranding, provided that when the stranding takes place the risk has attached and, if the policy be on goods, that the damaged goods are on board. Ship. 15 The term “ship” includes the hull, materials and outfit, stores and provisions for the officers and crew, and, in the case of vessels engaged in a special trade, the ordinary fittings requisite for the trade, and also, in the case of a steamship, the machinery, boilers, and coals and engine stores, if owned by the assured. Freight. 16 The term “freight” includes the profit derivable by a shipowner from the employment of his ship to carry his own goods or moveables, as well as freight payable by a third party, but does not include passage money. Goods. 17 The term “goods” means goods in the nature of merchandise, and does not include personal effects or provisions and stores for use on board. In the absence of any usage to the contrary, deck cargo and living animals must be insured specifically, and not under the general denomination of goods. F5 SECOND SCHEDULE Annotations: Amendments (Textual) F5 Ss. 92, 93, Sch. 2 repealed by Statute Law Revision Act 1927 (c. 42) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 72 of 166 Marine Insurance Act 1906 (c. 41) Document Generated: 2012-05-29 29 Changes to legislation: There are outstanding changes not yet made by the legislation.gov.uk editorial team to Marine Insurance Act 1906. Any changes that have already been made by the team appear in the content and are referenced with annotations. Changes and effects yet to be applied to : – s. 17 modified by 2012 c. 6 s. 2(5)(b) – s. 18(6) added by 2012 c. 6 s. 11(2)(a) – s. 19(1) s. 19 renumbered as s. 19(1) by 2012 c. 6 s. 11(2)(b) – s. 19(2) added by 2012 c. 6 s. 11(2)(b) – s. 20(8) added by 2012 c. 6 s. 11(2)(c) – s. 84 modified by 2012 c. 6 Sch. 1 para. 17 Page 73 of 166 Appendix F IMCA Guidance on The Use of Cable Laid Slings and Grommets PDF can be obtained from: http://www.imca-int.com/documents/core/sel/docs/IMCASEL019.pdf Appendix G IMCA Guidelines for Lifting Operations PDF can be obtained from: http://www.imca-int.com/documents/divisions/marine/docs/IMCAM179.pdf Page 74 of 166 Appendix H BWEA Guidelines for the Selection and Operation of Jack-Ups in the Marine Renewable Energy Industry Guidelines for the Selection and Operation of Jack-ups in the Marine Renewable Energy Industry Industry guidance aimed at jack-up operators, developers and contractors www.bwea.com Page 75 of 166 2 Acknowledgements The BWEA extends grateful acknowledgement to the following people and organisations for their commitment and contribution to this document. Key Consultees Mr. Thomas Broe Mr. Tony Millward Mr. Bill Cooper Mr. Stephan Henrikson Mr. Huw Powell Mr. John Gleadowe Mr. Chris Garratt Mr. Bill Hodges Mr. Gary Hogg Mr. Alan Dixon Ms. Judith Tetlow Mr. John Howard Mr. Ad Van der Pennen Mr. Duncan Wilson Mr. Malcolm Blowers Mr. Mark Hayward Mr. Mike Hoyle Mr. Julian Garnsey Ms. Samantha Henshaw Mr. Jim Sandon Mr. Julian Osbourne Mr. Spencer Chiu Mr. Tjerk Suurenbroek Mr. John Vingoe Mr. Rob Maynard Mr. Christian Seeberg Braun Mr. Joris Wortelboer Mr. Per C. Finsaas Mr. Henning Norholm Just Mr. John Fris Londal Mr. Christopher Andersen PMSS Fugro Seacore Searock E.ON Climate & Renewables Vestas Off shore London Off shore Consultants London Off shore Consultants London Off shore Consultants The Working Group Mr Jeremy Carnell Mr. David Pettigrew Mr. Peter Hodgetts Mr. Ian Johnson Mr Kevin Lennon Mr Chris Mallett Mr John Trickey Mr Mike Frampton A2sea A2sea ABP Marine Environmental Research Dong Energy EMU Fugro Seacore Garrard Hassan Global Maritime Global Maritime The Health & Safety Executive The Health & Safety Executive Howard Marine Jack-up Barge BV MPI MPI Noble Denton Noble Denton RWE NPower Renewables PMSS RES RPS RPS Seafox Contractors Seajacks Searock Siemens Wind Power Smit Statoil Hydro Vestas Off shore Vestas Off shore Windcarrier AS Chair Member Member Member Member Document author / editor Document author / editor Document author / editor Version 1 Page 76 of 166 3 Preface The UK has potentially the largest off shore wind resource in the world, with relatively shallow waters and a strong wind resource extending far into the North Sea. The UK has been estimated to have over 33% of the total European potential off shore wind resource - enough to power the country nearly three times over. The growth in UK off shore wind farm projects has increased substantially in recent years. Many Round 1 (see Crown Estate) developments are operational or nearing completion with a number of Round 2 projects well into the development phase. Bids for Round 3 projects closed in March 2009. The precise scale and timelines for future off shore developments are not fi nalised but what can be expected is a substantial increase in off shore construction and operation and maintenance activities. Jack-up barges, which are the focus of these guidelines, are likely to play a major role. BWEA is committed to raising Health and Safety standards across the wind, wave and tidal electrical generation sector. The justifi cation for these guidelines is twofold: • Safety: jack-ups are often large and complex vessels that can operate in extreme environmental conditions. Failure to ensure the correct selection and operation of these vessels could have serious safety implications including loss of life. • Knowledge: some participants in this growth sector may be less familiar with the key Health and Safety issues, legal standards and industry practices for Jack-up operations. For these reasons BWEA commissioned LOC in 2008 to deliver these guidelines in order to raise the knowledge and awareness of the issues to the industry and to share proven good practice. These guidelines will be reviewed periodically by BWEA to refl ect improvements and technology changes in Jack-up design and operational practice. STATUS These guidelines have been developed in consultation with the industry to refl ect established and proven good practice and sound methodology in the selection and operation of jack-up’s in the off shore wind, wave and tidal industries. The guidelines are not a standard in their own right, but do make reference to the relevant parts of a number of existing and established marine standards in the text. There is no compulsion for the industry to adhere to these guidelines but in the opinion of the authors and BWEA careful cognisance of and adherence to the guidelines together with suffi cient competence in this fi eld of activity will minimise risk of unsafe acts or conditions arising during jack-up operations. It is likely that in the event of a marine jack-up incident that is subject to investigation by UK enforcement agencies this guidance may be referenced as ‘industry good practice’ to which it would be expected that measures equal to or better than those in the guidance are in place. DISCLAIMER The contents of this guide are intended for information and general guidance only, do not constitute advice, are not exhaustive and do not indicate any specifi c course of action. Detailed professional advice should be obtained before taking or refraining from taking action in relation to any of the contents of this guide or the relevance or applicability of the information herein. Page 77 of 166 4 Contents Appendices 1. Introduction 6 2. Legislation and guidelines 7 3. Jack-up management and manning 8 4. Planning of jack-up operations 11 5. Weather restricted and unrestricted operations 14 6. Floating condition: motions and stability 16 7. Grillage, seafastening and cargo design 19 8. Site data required for jack-up site-specifi c assessments 21 9. Jack-up foundation (soils) assessment 24 10. Elevated operations 26 11. Self-propelled and propulsion assisted jack-ups 28 12. Non-propelled jack-ups 29 13. Towing vessels 32 14. Moorings for positioning 35 15. Lifting and load transfer 39 16. Crew transfer 42 17. Marine control for jack-up operations 44 18. Conduct of jack-up operations 45 19. Emergencies and contingencies 50 APPENDIX A: Reference documents 52 APPENDIX B: Defi nitions, terms and abbreviations 54 APPENDIX C: Jack-up certifi cates, manuals publications, logs and records 62 APPENDIX D: Jack-up operating manual (recommended contents) 64 APPENDIX E: Typical spot location report 66 APPENDIX F: Foundation risks: methods for evaluation and prevention 67 APPENDIX G: Flowchart for jack-up site assessment 68 APPENDIX H: Air gap calculation 69 APPENDIX I: Check list for jack-up suitability assessment 71 Chapter Appendix Page Page Page 78 of 166 5 1. Introduction 1.1 Instructions This document has been prepared by London Off shore Consultants Limited for BWEA following various BWEA/HSE discussions and consultations with others involved with the jack-up industry. The report provides guidelines on the safety and integrity of jack-up rigs deployed in the marine renewable energy industry. 1.2 Nature of the guidelines This guidance is intended to be relevant to all organisations contributing to the operation of jack-up vessels in nearshore areas but it is particularly relevant to jack-up owners’ or operators’ technical staff and crews responsible for the operation of jack-up vessels and to project managers in the marine renewable energy industry. These guidelines have been drawn with care to address what are likely to be the main concerns based on the experience of this working group and others. This should not be taken to mean that this document deals comprehensively with all of the concerns which will need to be addressed or even, where a particular matter is addressed, that this document sets out the defi nitive recommendations to be followed for all situations. The guidance is based upon the assumption that the user is familiar with the fundamental aspects of the marine operations of jack-up barges. Those less familiar with these vessels may fi nd it useful in the fi rst instance to acquire a basic understanding of the diff erent types of jack-ups and the risks associated with their various operating modes. This information can be obtained through study of background reference material listed in Appendix A. This document should be treated as providing guidelines for good industry practice to be followed for the selection and operation of jack-ups. The guidelines contained in this document should be reviewed in each particular case by persons responsible to ensure that the particular circumstance is addressed in a way which is adequate and appropriate. Nothing contained in these guidelines shall relieve the owners, operators, managers or masters and crews of the jack-ups of their responsibility for exercising sound judgement based on education, training and experience. These guidelines are not intended to exclude alternative methods, new technology or new equipment, which may provide an equivalent or greater level of operational safety. This guideline is based on and as far as is reasonably practicable is consistent with the guidance contained in existing reference documents listed in Appendix A. 1.3 Area of application This guideline shall be deemed to apply to all jack-ups operating in the inshore and coastal waters adjacent to England, Scotland, Wales and Northern Ireland in the area bounded by Highest Astronomical Tide (HAT) and the seaward limit of the UK territorial waters, and to all areas that are located within UK Renewable Energy Zones (REZ) beyond the UK territorial waters seaward limit 12 miles off shore. 1.4 Terms and defi nitions See glossary containing defi nitions, terms and abbreviations used in this guideline in Appendix B. Defi ned terms used in this guideline have been italicised in the text. Page 79 of 166 6 2. Legislation and guidelines 2.1 Reference is requested to BWEA Guidelines for Health and Safety in the Marine Energy Industry, which provides a basic introduction on the legislative requirements that govern the operations considered in this guideline. Particular reference shall be made to: • The Health and Safety at Work Act 1974 • The Management of Health and Safety at Work Regulations 1999 • The Construction (Design and Management) Regulations 2007 (CDM) • Provision and Use of Work Equipment Regulations 1998 (PUWER) • Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) 2.2 Contractors shall ensure that they fully understand and comply with the CDM regulations when operating jack-ups engaged on projects to which these regulations comply. A guide to these regulations is contained in the Approved Code of Practice (Managing Health and Safety in Construction) (ACOPS). 2.3 The adoption of codes and standards for the design, construction, and operation of jack-ups and attending vessels is governed by marine legislation promulgated by the state in which the vessel is registered (the fl ag state) and by the state which, by international agreement, has been assigned control over the waters in which the jack-up is operating (the port state). 2.4 Jack-up vessels in transit and positioning within UK waters are governed by the Merchant Shipping Act and the Marine and Coastguard Agency (MCA) is the principal government agency responsible for monitoring the implementation of UK marine legislation. In accordance with this legislation, jack-up operators shall arrange to receive Merchant Shipping Notices (MSN), Marine Guidance Notices (MGN) and Marine Information Notices (MIN) issued by the MCA and they shall heed warnings and comply with advice contained therein. 2.5 In addition, jack-ups shall comply with regulations issued by local port or river authorities and harbour masters whenever they are in transit or engaged in elevated operations in waters controlled by such authorities. 2.6 Jack-ups shall be designed, constructed and operated in compliance with the rules, standards, and codes applicable to their fl ag, type, tonnage, size and manning. These rules have been adopted under the terms of the International Conventions on Maritime safety and Marine Pollution and subsequent protocols and amendments as produced by the International Maritime Organisation (IMO). • International Safety Management (ISM) Code 2002 • Safety of Life at Sea (SOLAS 1974) • International Convention on Loadlines 1966 • Preventing Collisions at Sea Regulations COLREGS • Standards of Training, Certifi cation and Watchkeeping for Seafarers (STCW) 1978 • Prevention of Pollution from Ships MARPOL 1973/78 • Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 • Incidents by Hazardous and Noxious Substances, 2000 (HNS Protocol) • Control of Harmful Anti-fouling Systems on Ships (AFS), 2001 The list above includes the conventions and codes likely to apply to jack-up operations in the area considered; however, this list is not exhaustive. The responsibility for obtaining all relevant IMO documents and any latest amendments rests with the jack-up owner or operator. Page 80 of 166 7 2.7 The United Kingdom Health & Safety Executive (HSE) is responsible for enforcing all of the relevant Health and Safety legislation pertaining to work activity in Britain including work activities on jack-ups operating in UK Territorial Waters or within the UK Exclusive Economic Zone (EEZ). Therefore jack-up operators should obtain copies of current HSE Research Reports Information Sheets and Off shore Technology Reports relevant to jack-up operations [Appendix A] and be guided by the advice contained therein. Page 81 of 166 8 3. Jack-up management and manning 3.1 Registry and class 3.1.1 Jack-ups should be offi cially entered on a vessel registry maintained by a recognised maritime nation. 3.1.2 Jack-ups certifi ed to operate only within a specifi c trading area or within a limiting distance from a safe haven shall operate only within the limits prescribed by their fl ag state as stated on the jack-up’s registry certifi cate or certifi cate of seaworthiness and trading area. 3.1.3 Permanently manned jack-ups fi tted with certifi ed accommodation and jack-ups exceeding 24m in length shall be classed and class maintained in accordance with the rules of a recognised classifi cation society. 3.1.4 Unmanned jack-ups not fi tted with certifi ed accommodation and not exceeding 24 metres in length that are not classed shall be certifi ed in accordance with the MCA Small Commercial Vessel and Pilot Boat (SCV) Code as set out in MGN 280, or certifi ed in accordance with equivalent foreign rules promulgated by the fl ag state. 3.1.5 It is recommended that permanently manned jack-ups operating in unrestricted mode are classed by a member of the International Association of Classifi cation Societies (IACS) with jack-up experience and having established rules and procedures for the classifi cation of jack-up hulls, legs and machinery including elevating and holding systems. Such classifi cation societies can usually be identifi ed through the class notation, which should include the term “self elevating” to confi rm that the jack-up has been designed, constructed and maintained to operate in both fl oating and elevated modes. 3.1.6 It is recommended that permanently manned jack-ups fi tted with certifi ed accommodation are certifi ed in compliance with the MODU code. In the absence of a MODU (or MOU) certifi cate, the vessel should, as a minimum requirement, be provided with a class certifi cate or statement of facts verifying the provision of adequate safety equipment for the type of vessel and for the number of personnel on board. 3.1.7 It is a fundamental requirement that the jack-up hull, machinery and equipment shall be maintained in satisfactory condition. An adequate inventory of spare parts should be carried on board. Particular attention should be paid to the provision of replaceable parts for critical jacking system and power system components, where failure of such parts could render the systems inoperative. 3.1.8 It is recommended that site developers obtain an independent suitability survey or general condition survey prior to hiring a jack-up; however, the type and condition of the vessel can provisionally be assessed by review of the specifi cations and the registry and class certifi cates and survey reports [Appendix C]. Particular attention should be paid to the valid dates and any outstanding items or recommendations related to the class approval of design, drawings, manuals, materials, fabrication, modifi cation, maintenance, damage or repair as listed on the document attachments. 3.1.9 Outstanding class items or recommendations should be reviewed by a competent person in order to determine whether any listed defect or defi ciency could create unusual risk or otherwise adversely aff ect the proposed operations. The competent person should recommend, where appropriate, that these be rectifi ed before the jack-up is deployed. Particular attention should be paid to the structural strength and watertight integrity of the jack-up, the operability of the jacking system and the provision of safety equipment. Page 82 of 166 9 3.2 Draft and leg height marks 3.2.1 Draft marks shall be clearly marked on each side of the jack-up hull at each end in accordance with the rules contained in the International Convention on Loadlines 1966. Jack-ups exempted under these rules shall carry the same marks. 3.2.2 Leg height marks shall be clearly marked on each leg at vertical intervals not exceeding one metre. A fi xed point at the deck level or on the jack-house or jack-frame top shall be marked as a reference point against which the leg height marks can be read. The leg height marks and the fi xed reference points should normally be clearly visible from the jacking control position. 3.2.3 Where the confi guration of the jack-up is such that leg height marks and reference points cannot be observed from the jacking control position and where no mechanical or electronic leg height measurement system is fi tted at the control position, then trained crewmembers will usually be required to relay leg height information to the jacking engineer during jacking operations. 3.2.4 Jack-ups shall be fi tted with longitudinal and transverse inclinometers capable of providing accurate readings of tilt to within 0.2 degrees of accuracy or better. These instruments shall be calibrated to ensure accuracy. 3.3 Certifi cation and documentation 3.3.1 Original certifi cates, documents, publications and drawings listed in Appendix C should be carried on board the jack-up. Certifi cates for jack-ups not fi tted with permanent superstructures, enclosed control rooms or accommodation may be kept on board the towing vessel or at the owner’s offi ce and should be made available for inspection prior to vessel deployment. Holding copies of certifi cates and documents on board or ashore is a sensible precaution but presentation of copies should not be accepted as proof of validity. 3.3.2 Every jack-up shall be provided with an operating manual. The contents of the operating manual should contain, as a minimum, the information listed in Appendix D of this guideline. 3.4 Management 3.4.1 Certifi cation or registration of jack-up owners’ or operators’ companies to a standard recognised by the International Standards Organisation is not an absolute requirement; however, in the absence of such accreditation, they should be independently audited to verify that they practice an acceptable standard of management. 3.4.2 Standards of vessel management that are certifi ed under the provisions of the IMO International Safety Management (ISM) code will be deemed satisfactory. In the absence of ISM Certifi cation, it shall be demonstrated that the vessel is managed in accordance with a documented procedure that includes the key requirements of the ISM Code. 3.4.3 The safe management of jack-ups requires a wide range of technical skills: • Structural and off shore engineering • Vessel design and analysis • Vessel machinery operation, maintenance and repair • Navigation, seamanship and off shore operations • Meteorology • Soil investigation and analysis Page 83 of 166 10 Where technical staff holding the relevant qualifi cation and with the appropriate training and experience are not employed by the owners or operator of the jack-up then a competent person must be outsourced as appropriate. 3.4.4 Jack-up owners and operators shall formulate, publish and enforce a drug and alcohol policy. 3.5 Manning 3.5.1 Jack-ups shall be manned in accordance with the Safe Manning Certifi cate if so certifi ed. Jack-ups less than 24m in length shall be manned in accordance with the MCA Small Commercial Vessel and Pilot Boat (SCV) code as set out in MGN 280 or equivalent foreign rules promulgated by the fl ag state. 3.5.2 Whether certifi ed or otherwise, jack-up masters and any licensed person authorised by the master to operate the radio equipment shall demonstrate profi ciency in the English language. All emergency and external operating communications shall be conducted in the English language. In addition to the master, a suffi cient number of the crew shall be profi cient in English so that orders and instructions can be translated swiftly and eff ectively to non-English speaking crewmembers or project personnel. Internal instructions may be conducted in the common language of the crew. 3.5.3 In every case, jack-up owners or operators shall man their vessels with suffi cient crew to manage the vessel and the marine operations making proper allowance for rest periods. The following key positions are usually manned on jack-ups more than 24m in length. 1. Vessel or barge master (off shore installation manager) 2. Tow master for transit and positioning (may be covered by (1) above) 3. Jacking engineer (may be covered by (1) above except where (1) is tow master) 4. Engineer, motorman or mechanic 5. Electrician (may be covered by (4) above if competent) 6. Welder (may be covered by (4) above if competent) 7. Crane operator(s) (units fi tted with cranes) 8. Boatswain and seamen (number suffi cient for the size of the jack-up) 9. Deck foreman and riggers (as required for operations) 10. Catering crew (as appropriate for the number of persons on board) 11. Medic (may be an individual or any trained crewmember assigned to this duty) 3.5.4 The medic (or paramedic) should as a minimum hold a First Aid at Sea Certifi cate or Medical First Aid certifi cate and in some cases should hold a Profi ciency in Medical Care Certifi cate (or its predecessor, the Ship Captain’s Medical Certifi cate). For jackups <24m in length reference is requested to refer to the Small Vessel Code MGN 280 annex 3 page 118. The limitations of the basic training related to these certifi cates should be recognised and in some cases a higher qualifi cation will be appropriate. The level of training, profi ciency and qualifi cation required in each case should be determined through a risk assessment carried out considering the: • Number of persons on board • Proximity to the shore • Vessel and site equipment’s capacity for rapid medivac • Access by emergency services (including coastguard helicopter and RNLI) • Access restrictions imposed by the jack-up confi guration, weather or tide Page 84 of 166 11 3.5.5 Masters and crew serving on self-propelled jack-ups shall be in possession of valid Certifi cates of Competence issued under the provisions of the STCW 95 as required by the vessel’s Safe Manning Certifi cate, including GMDSS Operator’s Certifi cates and DP endorsements as appropriate. 3.5.6 It is noted that the Jack-up Owners Association has expressed an intention to develop a competence framework for barge masters; however, there is currently no statutory requirement for certifi cation or training of crews serving on non-propelled jack-ups. Notwithstanding the lack of a statutory requirement, it is recommended that barge masters serving on permanently manned jack-ups should be in possession of a Certifi cate of Competence in a marine grade and, in addition, should have received formal training in jack-up operations. 3.5.7 Whether certifi ed or otherwise, the barge master shall, as a minimum, demonstrate a satisfactory level of competence in the areas listed below. Competence may be demonstrated through Certifi cates of Competence issued under the provisions of STCW 95 or through other certifi cation or accreditation, or in the absence of such documents, through documented work experience and references. • Applicable laws and regulations • Vessel management • Marine operations, equipment and practices • Marine fi refi ghting • Operation of survival craft and sea survival • Pollution prevention • The GMDSS system and operation of radio equipment • First aid • Meteorology for mariners • Management of barge fl oating stability and jack-up elevated loads • Jacking operations and foundation hazards and shall, as a minimum, be in possession of: • GMDSS Radio Operators Certifi cate • Sea Survival Certifi cate • First Aid Certifi cate (or higher qualifi cation) 3.5.8 There is currently no statutory requirement for certifi cation or training of jacking engineers; however, it is recommended that jacking engineers receive formal training in jack-up marine operations including the fundamentals of jack-up soil foundations. Most importantly, the jacking system shall be operated only by, or under the supervision of, persons who have been trained to operate the type of system fi tted to the jack-up on which they serve. 3.5.9 Crane operators shall be in possession of a Crane Operator’s Certifi cate appropriate for the operation of the equipment installed. 3.5.10 Jack-up crew members shall be in possession of: • Valid certifi cates of Basic Off shore Survival Training of the type provided in the course of induction for personnel engaged in the off shore oil & gas industry (For example: UK OPITO Basic Safety Induction and Emergency Training) or similar merchant navy training for seafarers • Valid certifi cates of Medical Examination appropriate to service off shore or in the merchant navy (for example: UKO or (UK) ENG-1 or foreign equivalent) Page 85 of 166 12 4. Planning of jack-up operations 4.1 Suitability of the jack-up 4.1.1 The design of site-specifi c specialist structures and construction planning for the installation of the structures is a separate activity which may form the basis of jack-up selection. This will usually pre-date the selection of the jack-up; however, it should be recognised that construction planning may be infl uenced by the type and capacity of jack-ups likely to be available at the time the plans are to be executed. 4.1.2 The suitability of a jack-up for a particular operation can only be determined if the objectives to be achieved and the operations necessary to achieve the objectives are thoroughly understood. Based on this understanding, the jack-up’s type and operating limits must be assessed in consideration of the conditions likely to be encountered on the intended transit route and at the selected work site in order to determine whether the jack-up is capable of undertaking the required operations safely and effi ciently. 4.1.3 Jack-ups are not designed, constructed or intended for unlimited service at sea. Each stage of the proposed operations must be considered separately because diff erent limiting environmental criteria will apply to each sequential jack-up operating mode. Jack-up operations can typically be divided into the following stages: • Mobilisation • Loadout • Transit (including jacking down and refl oating) • Positioning (including jacking up and preloading) • Elevated operations (including lifting and load transfer operations) 4.1.4 The suitability of a jack-up for transit will depend upon the characteristics of the sea route and the unit’s seaworthiness and sea keeping capability. The suitability of the jack-up for elevated operations at any location is determined by a site-specifi c assessment. This assessment is a study of environmental, bathymetric and seabed soils data relevant to that location, together with a leg footing penetration analysis and a structural assessment of the rig itself to determine whether the unit is capable of: • Avoiding contact with seabed obstructions or debris • Achieving a stable foundation in the seabed soils • Elevating high enough to stand above the predicted extreme wave crests • Withstanding the static and dynamic loads imposed upon it when elevated • Safely extracting the legs from the soil on removal from the location 4.1.5 Preliminary site-assessments based solely on information related to the site water depth and the jack-up’s leg length may serve to exclude some units from consideration for proposed works at an early stage. Similarly, preliminary assessments based solely on nomograms may be useful but these should be treated with some caution because they may use safety factors less than those associated with the recommended practice and they may be based on assumed assessment parameters that are diff erent to those at the site. 4.1.6 It is stressed that the suitability of any jack-up for elevation and for the performance of the necessary operations on site can only be properly judged by means of a site-specifi c assessment carried out in accordance with the recommended practice. 4.1.7 The fundamental suitability of a jack-up should be established prior to planning or executing jack-up operations. Outline guidance on suitability is included as the fi nal APPENDIX I. Page 86 of 166 13 4.2 Requirement for planning 4.2.1 Jack-up transit, positioning and elevated operations should be planned and prepared in accordance with the provisions described in this guideline. The planning should include the provision of a documented procedure (or method statement) for each stage of the operation and an estimated time for the conduct and completion of each stage together with an adequate contingency for delay. • Departure from the present location • Passage between locations • Arrival and positioning at the new location • Elevated operations to be undertaken at the new location 4.2.2 In addition to the documented procedure, a full risk assessment of planned operations should be undertaken, and an emergency response plan and Health and Safety plan should be developed, both of which should be available onboard the vessel. The responsibilities and lines of communication should be clearly stated. 4.2.3 The procedure document should address the: • Objectives to be achieved • Operations necessary to achieve the objectives • Operational procedures to be adopted • Vessels, equipment and services required to conduct the operations • Geophysical, geotechnical, environmental and operating constraints and limits • Organisation and responsibilities of the parties and personnel involved • Communications • Contingency plans 4.2.4 Generic procedures for refl oating, towing or self-propulsion, dynamic positioning, jacking, preloading, and elevated operations as applicable to the routine operation of the jack-up are usually included in the vessel’s operating manual. 4.2.5 Detailed procedures for the safe operation and maintenance of the jacking machinery should be provided in the form of a jacking system manual if not included as part of the operating manual. Similarly, detailed procedures for the operation of vessel equipment such as engines, bilge and ballast systems and mooring systems should be provided in the vessel’s equipment manuals. These manuals need to be referred to, but may be excluded from the procedure document. 4.2.6 The operating manual and procedure documents shall be prepared in the English language. 4.2.7 All aspects of the planning shall be subject to review by a competent person. The planning and the review shall include the aspects detailed below. 4.3 Planning jack-up transit The jack-up’s limits afl oat (including leg strength and securing arrangements) should be considered and the aspects to be documented and reviewed shall include the: • Defi ned environmental criteria and duration of the transit • Stability calculation and watertight integrity of the jack-up • Motion response of the jack-up in the design sea state considered Page 87 of 166 14 • Strength of the cranes, deck equipment and seafastening arrangements • Details of the cargo and stowage plan • Strength of the cargo together with the grillage and seafastening arrangements • Towing arrangement plan, towing equipment and tug specifi cations (towed jack-ups) • Passage plan (all transits) 4.3.1 It should be verifi ed that the arrangements listed above are adequate for the intended transit and suffi cient to withstand the loads and motions for the jack-up’s condition afl oat. 4.3.2 The tugs together with the towing arrangements and towing equipment should be verifi ed as suitable for the proposed transit and in compliance with the requirements set out in this guideline. 4.3.3 It should be verifi ed that the transit route has been planned in accordance with the principles of good seamanship having due regard for narrows, water depths, squat eff ects, tidal heights and currents, vessel traffi c and separation systems and all navigational hazards. The jack-up’s air draft with legs fully raised should be considered in connection with maintaining safe clearances below overhead obstructions such as bridges and cables. It should also be verifi ed that the provision of navigation equipment, charts, tidal data, and nautical publications is adequate to complete the transit safely. 4.3.4 The transit route should be documented and should include designated safe havens en route and/or alternative safe jacking locations. The maximum transit time between safe havens or alternative jacking locations should be considered having due regard for the time required for jacking down, transit, positioning and jacking up to the minimum safe air gap at the next location. 4.3.5 Seabed surface and soil conditions at alternative safe jacking locations shall be investigated and documented as suitable for positioning. The selection of alternative jacking locations with very soft soils or locations where risk of rapid settlement is deemed to exist should be avoided. 4.3.6 The risk of failure of propulsion machinery or towing gear should be considered. Routes passing rocks, shoals and other hazards to navigation should be planned with allowance, where practicable, for time to repair machinery and reconnect the tow and for possible drift during such operations. 4.3.7 Planning jack-up transits shall include arrangements for the provision of marine weather forecasts obtained from a recognised meteorological authority in accordance with the detailed requirements described in section 18.3. 4.3.8 The planning should include contingency plans and emergency procedures as detailed in Section 19. 4.3.9 Planning jack-up transits should include information on the departure location and the proposed arrival location together with the arrangements for positioning the jack-up on location as follows. 4.4 Planning jack-up positioning 4.4.1 The planning and review shall include a site-specifi c assessment in accordance with the recommended practice for the jack-up at the proposed arrival location. Page 88 of 166 15 4.4.2 The procedure document shall include or make reference to the jack-up soils assessment and the site-specifi c assessment. These documents shall be placed on the jack-up and shall be reviewed by the persons responsible for positioning the jack-up in advance of the move. 4.4.3 The planning should also include site-specifi c jacking and preloading procedures (if any) that may have been developed in response to previously identifi ed jack-up foundation hazards and/or recommendations (if any) contained in the site-specifi c assessment or the soils investigation and assessment reports. 4.4.4 In considering the suitability of jack-up rig locations due consideration should be given to site accessibility. The marine aspects of the approach to and positioning at the arrival location such as water depth, tidal range, tidal current velocity, duration of slack water and navigational hazards should be considered. Particular consideration should be given to the proximity of fi xed or fl oating installations and sub-sea pipelines and cables. It needs to be demonstrated in the plan that the site can be reached without incurring unusual marine risk. 4.4.5 The plan shall include details of the method to be employed and the tugs, moorings and survey equipment required to move the jack-up into position afl oat at the required geographical co-ordinates and on the required heading. Page 89 of 166 16 5. Weather restricted and unrestricted operations 5.1 Operations considered 5.1.1 Jack-up operations in the following modes are considered: 1. Afl oat under tow 2. Moored afl oat 3. Partly elevated with the hull partly buoyant in leg-stabilised mode 4. Elevated in the operating mode at a working air gap 5. Elevated in the survival mode at air gap ≥ the minimum recommended safe air gap 5.1.2 Most jack-ups are required to operate in unrestricted mode (5) above, because the nature of their activity requires that they remain on location for many days or weeks and the distance off shore and the complexity of their equipment and moving arrangements means that they cannot be quickly or easily removed to shelter. 5.1.3 Jack-ups that are not designed or constructed to achieve the survival air gap or to withstand the stresses likely to be imposed by the 50 year design storm in the elevated condition may operate safely in weather restricted mode in accordance with the guidelines for weather restricted operations. 5.2 Jack-up - unrestricted operations 5.2.1 Good industry practice for unrestricted operations elevated requires that the jack-up be capable of elevating to the minimum survival air gap and that the unit’s design meets the minimum acceptance criteria for survival elevated as defi ned in the recommended practice. 5.2.2 The site-specifi c assessment (section 10) shall demonstrate that the unit is capable of remaining safely elevated on location in the prescribed 50 year extreme storm condition or the 10 year extremes for the de-manned condition (section 10.2.4) with a limited amount of additional penetration and with all structural stresses remaining within allowable limits. 5.2.3 When operating in unrestricted mode, the hull elevation for survival mode is to be set at or in excess of a minimum elevation to provide for 1.5 m clearance above the 50 year return period wave crest or to just clear the 10,000 year return period wave crest, whichever is greatest. 5.2.4 Seasonal variations in the 50 or 10 year extremes may be considered if the jack-up is to remain on location for a limited period only during specifi ed months. 5.2.5 Storm directionality may be considered if there is suffi cient reliable evidence that the extreme wind, waves and current at the location are directional. In such cases it may be possible to orientate the jack-up on the most advantageous heading in order to achieve the required values for the checks associated with the acceptance criteria. Particular care shall be taken in making assessments where the environmental conditions are highly directional, that is where they may change signifi cantly over only a few degrees. 5.3 Weather restricted operations 5.3.1 Jack-up operations in the fi rst four modes listed in (5.1) above may be undertaken as a weather restricted operation. In this case the jack-up’s design limits for each mode and the limiting weather criteria for each mode must be clearly defi ned in advance. With due regard for the confi dence in the predicted weather conditions, planning must be in place to remove the jack-up to shelter afl oat or to an alternative safe location where the jack-up can be elevated before the onset of any weather that is forecast to exceed the specifi ed limits. Page 90 of 166 17 5.3.2 The conduct of a weather restricted operation requires that detailed site-specifi c marine weather forecasts be obtained from a recognised authority at intervals no greater than 12 hours (section 18.3). 5.3.3 The planned duration of a weather restricted operation should not normally exceed 72 hours. However, the duration may be indefi nitely extended in prolonged periods of benign weather provided that the limits for the restricted mode are never exceeded, and provided also that a future weather window suitable for moving the jack-up to the safe location is clearly and consistently identifi ed by the duty forecaster with a high level of confi dence on each weather forecast. 5.3.4 If a future weather window for safe removal of the jack-up cannot be identifi ed with a high level of confi dence within the next 72 hours and risk of continued severe weather to follow is deemed to exist such that the limits for the restricted mode (as defi ned in paragraph 5.3.1) could be exceeded, then the jack-up should be moved to shelter immediately before the sea state limit for jacking down and moving off location is approached or exceeded. 5.3.5 The conduct of weather restricted operation requires that a procedure document shall be in place containing details of the proposed work schedule with particular reference to the anticipated duration of each operation, the time needed to suspend operations and to reach the nearest safe haven or safe elevated location and to complete positioning. A contingency for delay caused by leg extraction problems, waiting for slack water, breakdown or other delay shall be allowed. In no case shall the total time estimated for suspension of operations, removal to shelter and positioning at the safe location exceed 48 hours including contingency for delay. 5.3.6 A safe jack-up location may be a port or a sheltered bay or estuary where the jack-up can remain afl oat under tow or moored, or a location where the jack-up can be elevated providing: • The strength of the seabed soils is known to be suffi cient to support the jack-up without further settlement after preloading • The jack-up can be elevated to or above the minimum survival air gap • The jack-up is capable of achieving the survival mode with all stresses remaining within allowable limits 5.3.7 As part of an emergency response procedure, where insuffi cient time remains to reach a safe jack-up location before the anticipated onset of adverse weather and where the risk of remaining afl oat is deemed to be greater than the risk of elevating on a location with an unproven jack-up foundation, then consideration should be given to elevating the jack-up on the nearest location with suitable water depth before the onset of adverse weather, whether the strength of the seabed soil is known or otherwise. 5.3.8 The action described in 5.3.7 (above) should only be attempted at the master’s discretion following receipt of advice from the designated person ashore and the Maritime Rescue Coordination Centre (MRCC). In these circumstances, and where practicable, it is recommended that all non-essential personnel should be removed prior to elevation and consideration should be given to temporarily abandoning the jack-up as soon as it has been preloaded and elevated to the minimum survival air gap. 5.3.9 It should be recognised that the operation of a jack-up in weather restricted mode may result in prolonged delays caused by the potential for frequent interruption of the work in order to move the jack-up to shelter to await a suitable weather window (or series of weather windows) of suffi cient length to continue the proposed works. The limiting condition for the movement of most jack-ups is with signifi cant wave heights between 0.5m and 1.5m. The incidence of such benign conditions may be infrequent and of short duration in many areas, particularly in the winter season. 5.3.10 It should also be recognised that the operation of a jack-up in weather restricted mode involves higher risk than operation in unrestricted mode and consequently the planning and execution of a weather restricted operation requires a high level of competence. In consideration of the higher risk, developers or contractors may consider it appropriate to engage Marine Warranty Survey Services for review and approval of the procedures. Page 91 of 166 18 6. Floating condition: motions and stability 6.1 Application 6.1.1 Jack-up dry transport, self-propelled jack-up ocean transit and non-propelled jack-up ocean tow is not considered in this guideline. This guideline applies only to jack-up location moves and fi eld moves. Guidance on ocean towing can be found in Noble Denton 0030/ND Dated 15/04/200 Guidelines for Marine Transportations and IMO Guidelines for Safe Ocean Towing, December 1998 (MSC/Circ.884). 6.2 Design environmental criteria 6.2.1 This guideline assumes that all transits of self-propelled jack-ups when carrying project cargo and all transits of non-propelled jack-ups with or without cargo will be undertaken as a weather restricted operation with the jack-up essentially in fi eld move confi guration. 6.2.2 Specifi c environmental criteria shall be defi ned for a weather restricted operation and these shall be appropriate to the planned route and the duration of the tow. 6.2.3 The duration of the passage under power or under tow should include any additional time for jacking and preloading on site and any standby time that may reasonably be expected as a result of delays. Planned contingencies for diversion at any point en route to reach a place of shelter should be in place. 6.2.4 The design seastate for a jack-up transit conducted as a weather restricted operation shall be based on the signifi cant wave height (Hs). Typically, the maximum wave height will be 1.86Hs. The design wind speed shall be the one-minute average velocity at 10m above sea level. The incident wave shall be considered to be omni-directional. 6.2.5 The operating criteria shall be set lower than the design criteria to allow for potential inaccuracy in wave height forecasts. Typically weather restricted towages should not commence in seastates greater than 50% of the design maximum as the observer will often report the signifi cant wave heights rather than the maximum wave height. 6.3 Motion response criteria 6.3.1 The jack-up, cargo, grillage and seafastenings shall be designed to withstand the motions and forces resulting from the design environmental criteria. Friction shall be ignored. It is recommended that either a motion response analysis is made or that model tests are performed for each case. 6.3.2 The motion response analysis should utilise proven software and techniques. For both motion response analysis and/or model tests, a realistic combination of environmental loads and wave directions and periods, representing bow, stern, quartering and beam sea conditions shall be used. If required, the analysis shall be validated by correlation with model tests for similar units or by performing new model tests. Alternatively, additional analysis may be performed covering more seastates or using diff erent software 6.4 Default motion criteria 6.4.1 Alternatively, and subject to consideration of the length of the voyage, the risks involved and any mitigating factors for reducing the risks, the jack-up, cargo, grillage and seafastenings shall be designed to withstand the motions and forces derived by using Page 92 of 166 19 Type of jack-up Large jack-up Small jack-up Ship shape unit Field move LOA ≥ 76 and B ≥23 LOA < 76 or B < 23 LOA ≥ 76 and B ≥23 All jack-ups } 20 } 25 } 20 } 10 } 12.5 } 15 } 12.5 } 10 } 0.2g } 0.2g } 0.2g } 0.1g Barge dimensions L & B m Roll amplitude degrees Pitch amplitude degrees Heave acceleration m/s2 default motion criteria tabulated below. The standard criteria shown above should be applied in accordance with the following: • The roll and pitch amplitude are single amplitude values assumed to apply for a 10 second full cycle period of motion • The roll and pitch axes should be assumed to pass through the centre of fl oatation. • The phasing considered should be assumed to combine, as separate load cases, the most severe combinations of: roll ± heave; pitch } heave. 6.5 Inland and sheltered water criteria 6.5.1 For inland and sheltered water transportation, whichever of the following has the greatest eff ect shall be taken into account: • Static loads caused by an acceleration of 0.1g applied parallel to the deck in the roll or pitch direction • The most severe inclination in the damage condition, as determined by the damage stability calculations including the additional heel or trim caused by the design wind. 6.6 Intact static stability 6.6.1 Jack-up stability afl oat shall be calculated to demonstrate compliance with the rules published by a recognised classifi cation society or the rules contained in the MODU Code or the rules contained in MCA - MGN 280 as applicable to their type, tonnage, size and classifi cation, or in accordance with the guidelines provided below. 6.6.2 The intact stability, or intact range of stability, is the range between 0 degree heel or trim and the angle at which the righting arm (GZ) becomes negative (see fi gure. 6.1). el Angle Righting Arm (GZ) 0 0 0 0 10 0.3 80 2.4 20 0.65 30 1.2 40 1.7 0 53 50 2 2.05 53 60 1.95 70 1.6 80 1 90 0.45 100 -0.05 105 -0.2 0 1.3 85 1 80 0 80 1 -0 5 0 0.5 1 1.5 2 2.5 0 20 40 60 80 120 Heel Angle Righting Arm (GZ) Figure 6.1 - Illustration of stability terms Page 93 of 166 20 6.6.3 The transverse metacentric height (GM) must be positive, at zero angle of heel. 6.6.4 The range of transverse static stability should normally exceed 40 degrees. Correction to values of GM to allow for free surface eff ects should be included in this computation. 6.6.5 The acceptability of barges with a range of 30 to 40 degrees will be dependent on motion response predictions. 6.6.6 In the event of the range of static stability being greater than 30 degrees and less than 40 degrees, it shall be demonstrated that the maximum predicted roll angle is less than the angle at which the maximum righting lever occurs. 6.6.7 A range of static stability less than 30 degrees will not normally be accepted. 6.7 Intact dynamic stability 6.7.1 The areas under the righting moment curve and the wind heeling moment (or wind moment) curve should be calculated up to an angle of heel which is the least of: • The angle corresponding to the second intercept of the two curves • The angle of down fl ooding 6.7.2 For guidance on how to derive the wind heeling moment curve, reference is made to IMO resolution A.749 (18) Code on Intact Stability for all Types of Ships covered by IMO instruments. 6.7.3 The wind velocity used to compute the wind heeling moment curve should be the one-minute sustained wind for the operation as defi ned in section 6.2. 6.8 Damage static stability 6.8.1 As a minimum, the jack-up should have suffi cient stability and reserve buoyancy to remain afl oat at a waterline below any opening where progressive fl ooding may occur with any one-compartment adjacent to the sea fl ooded. -0.5 0 0.5 1 1.5 2 2.5 3 3.5 0 10 20 30 40Heel A50ngle 60 70 80 90 Moment A B C Wind Moment Righting Moment INTACT STABILITY (A+B) > 1.4(B+C) Figure 6.2 - Intact stability requirement Page 94 of 166 21 6.8.2 Damage to any compartment above the intact waterline that could lead to loss of stability should be considered when assessing damage stability. 6.8.3 The loss of water from a full compartment should be considered if it gives a more severe result than the fl ooding of an empty compartment. 6.9 Damage dynamic stability 6.9.1 The area under the righting moment curve should be not less than the area under the wind heeling moment curve. 6.9.2 The areas under the righting moment curve and the wind heeling moment curve should be calculated from equilibrium up to an angle of heel which is the least of: • The angle corresponding to the second intercept of the two curves • The angle of down fl ooding 6.9.3 The wind velocity that is used to compute the overturning moment curve may be 25m/s. However, if the design wind velocity for the operation, as defi ned in section 6.2 is less than 25m/s, the design velocity should be used instead. 6.9.4 Where it is impracticable to comply with damage stability recommendations, a risk assessment should be carried out, and appropriate mitigating measures taken. Righting Arm (GZ) 8 0 0 10 0.1 80 20 0.65 30 1.2 40 1.7 0 50 2 2.05 60 1.95 70 1.6 8 0 80 1 8 1.3 90 0.45 100 -0.05 105 -0.2 8 1.3 85 1 Heel Angle Moment A B C Wind Moment Righting Moment DAMAGE STABILITY (A+B) > (B+C) Figure 6.3 - Damage stability requirements Page 95 of 166 22 7. Grillage, seafastening and cargo design 7.1 Loads during transportation 7.1.1 The components of load to be considered when analysing the total forces acting on the cargo, the vessel and grillage and seafastenings are those due to: • The static weight of the cargo • The dynamic loads which result from the vessel’s motion in all six degrees of freedom • The static component of weight which acts parallel to the barge deck when the vessel rolls or pitches • Loads caused by heave acceleration including the heave.sin (Θ) terms • Wind load • Loads resulting from immersion of any part of the cargo support frames • Ballast distribution in the barge • Ice where appropriate 7.1.2 Regarding the loads due to motions above, the combination of motions that give the highest loading in any direction shall be considered. In the absence of information to the contrary (such as a motion analysis taking account of phase relationships to compute acceleration vectors), the highest loadings resulting from the following motions shall be combined as two separate load cases: • Roll, heave and sway • Pitch, heave and surge 7.1.3 Loads may normally be calculated using the assumption that all motions approximate to sinusoidal motions. 7.1.4 Structural loadings due to green water impact shall be based on the true relative motion between the structure and wave surface. 7.1.5 Account shall also be taken of any substantial loads in the grillage and seafastenings resulting from the relative defl ections of vessel and cargo, whether due to changes in ballast arrangement or due to environmental eff ects. 7.1.6 When using the default criteria as defi ned in section 6.4 seas from headings other than the bow, stern and beam the horizontal accelerations may be resolved as applicable to the required heading. The resultant acceleration in the desired direction shall be obtained from taking the square root of the sum of the squares of the resolved accelerations. The heave acceleration will remain unchanged. 7.2 Stresses 7.2.1 The grillage and seafastenings shall be designed in accordance with a recognised standard or code of practice. Wherever possible, the design should be carried out to the requirements of one code only. 7.2.2 The seafastening shall be designed such that the static stresses in all members do not exceed the allowable stresses in accordance with AISC manual or other acceptable code. The 1/3 increase in allowable stresses referred to in earlier editions of the AISC manual may be used for stresses in cargo, grillage and seafastening where the steelwork is of high quality. It should not be used for the design of grillage and seafastening connections to the vessel or assessing the underdeck strength except when the condition of all steelwork associated with the load path has been verifi ed as being of high quality with full material certifi cation. Page 96 of 166 23 7.2.3 If the AISC 13TH edition is used the allowables shall be compared against member stresses determined using a load factor on both dead and live loads of no less than: WSD option LRFD option SLS: 1.0 1.60 ULS: 0.75 1.20 7.2.4 Any load case may be treated as a normal serviceability limit state (SLS)/normal operating case. 7.2.5 Infrequent load cases occurring no more frequently than the maximum design wave, which are dominated by extreme environmental forces may generally be treated as an ultimate limit state (ULS)/survival storm case. This only applies to steel of high quality which has been verifi ed by a thorough and appropriate NDT inspection. 7.3 Grillage 7.3.1 The grillage design and layout should take account of any limitations imposed by the load transfer method. 7.3.2 The basis for the design of the grillage shall be the loads derived from the vessel motions as defi ned in section 6.3 or 6.4. 7.3.3 The relative stiff ness of the barge frames and bulkheads shall be taken into account when deriving the load distribution between the grillage and the barge. 7.3.4 The eff ects of super-position of loads shall be accommodated in the design when welds/connections are made between the grillage and barge deck following load out. 7.4 Seafastening 7.4.1 The purpose of the seafastenings is to secure the cargo during the transit and positioning so that neither the cargo nor vessel suff ers loss or damage as a result of the loadings derived from the vessel motions caused by the environment conditions. 7.4.2 Seafastenings should not in any circumstances be removed until the jack-up has completed preloading or predriving and elevating to the operating air gap. Primary seafastenings should be designed to be removed without damage to the cargo. During and following removal of primary seafastenings, adequate residual seafastening should remain to safely restrain the cargo until its removal from the vessel. 7.4.3 The entire load path, including the potential sliding surfaces, should be demonstrated to be capable of withstanding the design loads. 7.4.4 Small items of cargo ≤1000kg should be secured in accordance with good practice using appropriate lashings or securing arrangements that are adequate to ensure they are safely secured and will not be a hazard to any person in the event of bad weather or an emergency. 7.4.5 If the seafastenings are welded to the cargo it is recommended that they be fi tted after the vessel has been ballasted to the transport condition. 7.4.6 Where the same seafastenings are to be used for multiple transits, inspection of welded seafastenings and/or bolted connections is required prior to commencing each transit. Where practicable, locking nuts/devices should be used in preference to ordinary bolts. Page 97 of 166 24 7.5 Vessel strength 7.5.1 The calculated still water bending moment (SWBM) and shear force (SF) shall be checked against the allowable SWBM and SF values approved by the classifi cation society. If they exceed the specifi ed permissible loads then the classifi cation society shall be informed and their acceptance obtained. 7.5.2 The legs, jack houses and hull are to be shown to possess adequate strength to resist the loads imposed during the sea passage afl oat. Leg chocks, wedges and locking devices shall be considered if fi tted. 7.5.3 Local vessel strength calculations shall be required at highly stressed areas of the vessel. These calculations shall take account of any corrosion from the “as-built” scantlings. 7.6 Cargo strength 7.6.1 It shall be demonstrated that the cargo (equipment, tools, modules and wind turbine components etc.) has adequate structural strength to be transported without damage caused by the maximum loadings resulting from the vessel’s motions under the environmental conditions described in section 6.3 or from the standard criteria as given in section 6.4. 7.6.2 Local analysis may also be required to quantify load eff ects in localised highly loaded areas such as grillage supports or seafastening connection points, and to confi rm the adequacy of equipment to withstand these loads without damage. 7.6.3 The cargo structure is to be shown to have adequate strength to resist the loads imposed during the voyage combined with the additional loading caused by any overhang of the cargo over the side of the transport vessel. 7.7 Internal seafastenings 7.7.1 Internal seafastenings shall be provided where necessary. These may be in the form of temporary members to provide structural support during transportation, or the securing of equipment and loose items forming part of the cargo. Protection against wave slam or spray should also be provided as appropriate. Calculations may be required for major items of equipment. 7.8 Fatigue 7.8.1 Whether or not fatigue analyses are performed, all seafastenings shall be designed for good fatigue characteristics. Page 98 of 166 25 8. Site data required for jack-up site-specifi c assessments 8.1 General 8.1.1 Site survey is required for the purpose of providing data with which to defi ne the position, boundary and characteristics of the location for the purpose of determining the suitability of the site for the operation of the jack-up. 8.1.2 Geophysical data alone is insuffi cient to perform a site-specifi c assessment of the soil foundation conditions and this should be complemented by geotechnical information as described in section 8.7, except for jack-ups engaged in soils investigations as provided in section 18.6. 8.1.3 It is recommended that a single uniform survey system (e.g. WGS84) be used for both site investigation and subsequent fi eld development so as to ensure that compatibility and conformity is achieved between the original site investigation and the operations of marine units subsequently involved in the site works. 8.2 Location co-ordinates 8.2.1 The co-ordinates of each jack-up location expressed in terms of degrees, minutes and seconds of latitude and longitude are required. Latitude and longitude co-ordinates should be given to at least two, or preferably three, decimal places of precision and must also include details of the datum and projection used. 8.3 Water depth, tidal range and storm surge 8.3.1 The water depth at each jack-up location, referred to Lowest Astronomical Tide (LAT), is required. Nearshore pre-construction surveys producing results with vertical levels related to Ordnance datum must be converted to LAT before application to jackup marine operations. 8.3.2 The maximum tidal range and the 50 year storm surge shall be computed for the jack-up location and/or for the area of operations considered. The following data shall be provided as a minimum. • 50 Year storm surge (m) • Highest Astronomical Tide (HAT) (m) • Lowest Astronomical Tide (LAT) (m) 8.4 Wind and wave and current data 8.4.1 Meteorological extremes likely to be reached or exceeded once, on average, every 50 years, are required as listed below. The provision of 1 year and 10 year extremes is also recommended. This information, together with the data in the fi rst two bullet points in 8.3.2 above, is required for the site-specifi c assessment. • Wind – one-minute mean (m/s) • Extreme wave height (m) • Extreme wave crest elevation (m) • Associated crest to crest wave period (sec) • Peak period (sec) • Signifi cant wave height (m) • Maximum surface current in downwind direction (m/s) • Current profi le 8.4.2 Particular attention shall be paid to the provision of competent data for inshore sites that may be aff ected by: • Shelter aff orded by proximity of the coastline or shallows Page 99 of 166 26 • Refracted and/or refl ected waves • Breaking waves and surf zones • High velocity tidal currents (>1.5 m/s) in the vicinity of sand banks and narrows • Tidal bores • Wakes from passing vessels, particularly deep displacement ships and fast craft. 8.4.3 Special consideration is required at sites where breaking waves will occur. Calculation of hydrodynamic loads is not straightforward and a degree of judgement is required by the analyst to arrive at correct design values. Guidance on this subject can be found in ISO 19901-1:2005 (E) part one: “Metocean Design and Operating Considerations”. 8.4.4 Comprehensive met-ocean studies carried out in connection with nearshore and off shore wind farms do not usually take account of the specifi c data required for jack-up emplacement. This creates a need for interpolation which can lead to inaccuracy and signifi cant diff erences in the analyses carried out by diff erent contractors for diff erent jack-ups. For this reason it is recommended that such studies be reviewed by a single competent meteorological authority specialising in the provision of meteorological data for jack-up site-assessments and that the data be presented as a jack-up Spot Location Report (SLR) in a simple unequivocal format (Appendix E). 8.5 Bathymetric survey 8.5.1 A bathymetric survey is required for an area of approximately 1km square centred on the proposed location. Line spacing of the survey should be typically not greater than 100m x 200m over the survey area. If any irregularities are detected interlining should be performed with spacing not exceeding 25m x 50m. Swathe bathymetry or other techniques providing an equivalent or greater level of accuracy may be used as an alternative method of producing the survey results. 8.5.2 Rapid changes in bathymetry shall be anticipated in shallow areas that are subject to high velocity tidal currents and/or areas that may have been exposed to severe storm waves. The appropriate period of validity of the survey should be considered in all cases having due regard for the site characteristics and the anticipated rate of change indicated by earlier surveys. The survey report should include comment on the anticipated period of validity plus the magnitude and probability of error resulting from seabed changes. 8.5.3 Navigational charts derived for shipping are not usually suffi ciently accurate for positioning jack-ups; however, up to date corrected charts for the transit route together with the largest available UK Admiralty navigation charts for the site are required to be carried on the jack-ups and attending tugs for reference. Paper charts may not be required on jack-ups that are ECDIS equipped and certifi ed for ECDIS use only. 8.5.4 Notes and cautions listed on Admiralty charts should be referred to. Navigation should not be attempted through or within areas marked as “not surveyed”, or areas carrying the notation “banks and channels subject to frequent change” or similar notation, without reference to recent bathymetric survey information. 8.6 Seabed surface survey 8.6.1 A seabed surface survey is required to identify natural and man-made seabed features, obstructions and debris. The survey should cover the approach to and the immediate area of the intended location (normally a 500m x 500m square for off shore and nearshore sites) and should be carried out using side scan or sector scan sonar, or other high-resolution techniques producing equivalent or better results. Page 100 of 166 27 8.6.2 A magnetometer survey is required to reveal the presence of buried pipelines or cables, lost anchors and chains, military ordnance or other metallic debris lying below the seabed surface. The requirement for a magnetometer survey may be waived in certain areas but the lack of this information should be justifi ed in the site-specifi c assessment. 8.6.3 Site and location plans based on the seabed surface surveys should identify wrecks and important archaeological sites and/ or marine conservation areas that are subject to protection. Sites where seabed or environmental disturbance should be avoided for any reason shall be identifi ed. Specifi c information concerning the type of activity to be avoided and or seasonal limits or other qualifying conditions related to these areas should be provided. 8.6.4 The appropriate period of validity of the seabed surface survey should be considered in all cases having due regard for the site characteristics and any surface or subsea activity carried out on site since the last survey. As a general rule, the period of validity should be six months or less in uncontrolled areas and areas where no continuous system for reporting marine activity and lost objects exists. 8.6.5 The discovery of seabed surface obstructions or debris at any time within or without the site area should be reported to the site Marine Traffi c Controller (MTC) or, in the absence of an MTC, to the UK Hydrographic Offi ce. 8.7 Geotechnical (soils) investigation 8.7.1 Site-specifi c geotechnical information is required. The type and amount of data required will depend upon the particular circumstances such as the type of jack-up, soil conditions and previous experience of the site, or nearby sites, for which the assessment is being performed. 8.7.2 For sites where previous preloading and elevated operations have been performed by jack-ups, it may be suffi cient to identify the location of existing jack-up footprints. In this case the details of the previous jack-up footing design and the preload applied should be available and it should be verifi ed that the foundation bearing pressure applied previously was in excess of the pressure to be applied by the jack-up under consideration. In the absence of such verifi cation soil investigation involving boreholes or CPT is required. 8.7.3 The location and number of boreholes or CPT’s required should account for lateral variability of the soil conditions, regional experience and the geophysical investigation. A borehole may not be required if there is suffi cient relevant historical data and/ or geophysical tie lines to boreholes in close proximity to the proposed jack-up location. 8.7.4 The geotechnical investigation should comprise a minimum of one borehole to a depth equal to 30m or the anticipated penetration plus 1.5 – 2.0 times the footing diameter, whichever is greater. Investigation to lesser depths may be accepted in cases where only small penetrations are anticipated in hard soils; however, in such cases the advance approval of an geotechnical engineer with appropriate experience with jack-up foundation assessments is recommended and the reduced depth of investigation shall be justifi ed in the foundation assessment. 8.7.5 All layers shall be adequately investigated, including any transition zones between strata, such that the geotechnical properties of all layers are known with confi dence and that there are no signifi cant gaps in the site investigation record. Laboratory testing of soil samples may be required. Page 101 of 166 28 8.7.6 Geotechnical investigations carried out in connection with construction activities such as pile driving may be of limited use for jack-up site assessments. Care must be exercised to ensure that the soil investigation is adequate in scope and detail for jackup site-assessment. If in doubt, a geotechnical engineer with appropriate experience with jack-up foundation assessments shall be consulted. 8.7.7 In virgin territory where there is no soil data available, seabed sampling may be carried out from suitable jack-ups prior to installation. In such cases appropriate precautions (section 18.6) must be taken to ensure the safety of the jack-up during the initial period on location and until the soil investigation is complete. 8.7.8 The nature of the seabed surface soil, together with the water depth and the current and wave regimes shall be assessed to determine whether potential for scour may exist. The assessment should consider whether scour has occurred around existing fi xed or temporary structures in the vicinity (if any) and records of previous scour that may have aff ected earlier jackup installations. In the event that the assessment indicates that the integrity of the jack up foundation could be adversely aff ected then seabed soil samples may be required and a scour analysis should be performed (section 9.13). 8.7.9 The soil investigation must produce suffi cient reliable data on which to base a competent analysis that will provide a recommended soil strength design profi le giving lower and upper bound strength estimates. This will be carried forward into the jack-up site-specifi c assessment (section 10). Page 102 of 166 29 9. Jack-up foundation (soils) assessment 9.1 Foundation assessment is required in all cases where the jack-up is to be preloaded and elevated above the sea surface to a working air gap or to the minimum safe survival air gap on location. The scope of the assessment and the amount of data required will depend upon the particular circumstances such as the type of jack-up, the soil conditions and variations in the soil across the site, and upon previous experience of the site, or nearby sites, for which the assessment is being performed. 9.2 The jack-up foundation assessment shall be carried out in accordance with the recommended practice or in accordance with another recognised and appropriate code of practice that provides an equivalent level of safety. The assessment shall have due regard for potential hazards listed in SNAME T&R Bulletin 5-5A. Foundation risks are tabulated in Appendix F. 9.3 For jack-up locations where there is no history of previous jack-up emplacement a complete foundation assessment is required. The assessment shall include or refer to a geotechnical report containing the survey records together with their interpretation by a qualifi ed soils engineer plus a leg penetration assessment for the proposed unit or a unit with similar footing design and load characteristics. 9.4 For jack-up foundation assessment at sites where preloading operations have been performed earlier by the same or another jack-up it may be suffi cient to identify the location of existing jack-up footprints. In this case the details of the previous jack-up footing design and the preload applied should be available and it should be verifi ed that the footing type was similar to the jack-up under consideration and the foundation bearing pressure applied during the previous installation was in excess of the pressure to be applied for the jack-up considered. In the absence of such verifi cation a complete foundation assessment is required. 9.5 The combinations of vertical and horizontal load shall be checked against a foundation bearing capacity envelope. The resistance factor may be taken as 1.0 when the load-penetration curve indicates signifi cant additional capacity for acceptable levels of additional settlement. Minor settlement not exceeding the limits contained in the Operating Manual may be acceptable provided that: • The jack-up can withstand the storm loading plus the eff ects of the inclination • The lateral defl ections will not result in contact with adjacent structures • The jacking system will remain fully operational at the angle of inclination considered 9.6 Consideration shall be given to the operating limits of the jacking system. The capacity of any jacking system to elevate or lower the hull may be signifi cantly reduced or eliminated by leg guide friction (binding) caused by small angles of inclination. Additionally, some hydraulic recycling jacking systems cannot usually be jacked at angles of inclination greater than 1.0 degree because even this small angle can result in inability to extract or engage the fi xed and working pins (or catcher beams). 9.7 Extreme caution should be exercised if the soil profi le reveals a risk of punch-through when it should be demonstrated that there is an adequate safety factor to ensure against punch-through occurring in both extreme (abnormal) storm events and operating conditions. Particular attention must be paid to the appropriate safety factor in cases where the jack-up’s maximum Page 103 of 166 30 preload capacity does not produce signifi cantly greater foundation bearing pressure than that to be applied in the operating or survival modes (See fi gure 9.1). 9.8 Calculation of the safety factor against punch-through should normally be in accordance with the recommended practice; however, alternative methods that may provide an equivalent or greater level of safety exist and therefore consideration should be given as to which method is appropriate in the circumstances. For this reason reference should be made to other sources of advice contained in UK HSE research report 289 - Guidelines for Jack-up Rigs with Particular Reference to Foundation Stability; Noble Denton 0009/ND Rev 4, dated 16 December 2008 - Self-Elevating Platforms - Guidelines for Elevated Operations; and Det Norske Veritas Classifi cation Note No. 30.4. Ultimately, the assessment of punch-through risk requires a high level of expertise and the exercise of sound judgment based on experience. 9.9 Consideration should be given to the limits of maximum and minimum penetration as determined by the jack-up design or Operating Manual. In cases where the limits stated in the manual are related simply to a sample elevated condition and the leg length installed, it can be ignored provided the leg length is suffi cient to meet the survival air gap defi ned in the recommended practice. An analysis should be carried out for any case where the maximum or minimum penetration limit stated in the manual is related to leg or spudcan structural strength or to the jack-up’s capacity for leg extraction. 9.10 Particular consideration shall be given to the requirement for extracting the leg footings and the probable eff ectiveness of the leg jetting system (if fi tted). Temporary inability to extract the legs from the soil may involve serious risk if the unit cannot be quickly removed to shelter and/or cannot achieve the elevated survival mode and remain on location. Figure 9.1 Page 104 of 166 31 9.11 For jack-ups fi tted with hydraulic recycling jacking systems there is the additional risk that the jacking system may become temporarily immobilised through inability to extract fi xed or working pins during the leg extraction operation. If this occurs during a rising tidal cycle then damage or fl ooding may result. 9.12 Operations involving leg extraction from deep penetration may be considerably prolonged in cases where deep leg penetration has been achieved, particularly if the leg extraction operation is interrupted by periods of adverse weather. The onset of weather conditions exceeding the limits for refl oating the unit will require the jack-up to be re-elevated and preloaded and if this becomes necessary any progress that had been achieved with leg extraction prior to such onset will be almost entirely reversed. In addition to the risk described in 9.9 above, this may have a serious commercial impact in terms of costs caused by an extended delay. 9.13 The potential for seabed scour shall be considered. Special consideration shall be given to the movement of seabed soils caused by currents or waves and the potential impact this may have on the integrity of the jack-up foundation over time. At locations where risk of scour is deemed to exist, the foundation assessment shall include an assessment of the potential depth and rate of soil removal and that may aff ect foundation stability. The assessment shall include a caution to the eff ect that special jacking procedures may be required to mitigate the risk of foundation instability and should also recommend scour protection measures where appropriate. Page 105 of 166 32 10. Elevated operations 10.1 General requirements 10.1.1 Every jack-up shall be provided with an operating manual stating the design limits of the unit for elevated operations. 10.1.2 Every jack-up shall have adequate structural strength and overturning stability to withstand any combination of environmental conditions to which the jack-up may be subjected while elevated at a specifi ed location. Account shall be taken of the properties and characteristics of the seabed and subsoil to ensure there is adequate resistance for applied loads. If rotational foundation fi xity can be justifi ed this may be included in appropriate structural analysis. 10.1.3 No jack-up shall be elevated in weather unrestricted mode (section 5.2) on a location unless, prior to moving, the owner or operator of the unit has obtained from a competent person: a. A Meteorological Spot Location report (Appendix E) b. A Soils investigation and Jack-up Foundation Assessment report c. A site-specifi c assessment report carried out in compliance with the recommended practice confi rming that the jack-up is structurally capable of remaining on location and withstanding the extreme environmental conditions with all stresses remaining within allowable limits and that the seabed and subsoil will provide adequate resistance to withstand the loads at the footings. 10.1.4 No jack-up shall be elevated on location in weather restricted (section 5.3) unless, prior to moving, the owner or operator of the unit has obtained from a competent person: a. Defi ned limiting environmental criteria for the operation b. A Soils Investigation and Jack-up Foundation Assessment report (except as provided for soil investigations in section 18.6) c. A site-specifi c assessment report confi rming that the jack-up is structurally capable of remaining on location and withstanding the defi ned environmental criteria with all stresses remaining within allowable limits and that the seabed and subsoil will provide adequate resistance to withstand the loads at the footings. 10.2 Requirement for site-specifi c assessment 10.2.1 Before installing a jack-up on any location a site-specifi c assessment shall be performed by a competent person. 10.2.2 For multiple locations contained within a defi ned area, such as an off shore wind farm, the number of site-specifi c assessments for the site shall be suffi cient to consider the complete range of physical, environmental and geotechnical conditions across the site. Particular attention shall be paid to any variation in the soil conditions across the site. 10.2.3 The 50 year return period extremes shall be used for the site-specifi c assessment for permanently manned jack-ups unless the unit is to operate in weather restricted mode. 10.2.4 The 10 year return period may be considered where arrangements (including documented procedures) are in place for the safe removal of all personnel from the jack-up prior to the onset of weather conditions predicted to exceed the limit for safe disembarkation, having due regard for the level of confi dence in the forecast weather conditions. 10.2.5 The 10 year return period should only be used for de-manned jack-ups in cases where there is no risk to personnel and where the site developer and the jack-up owner have formally assessed the consequences of catastrophic weather damage to the jack-up and the potential threat to the environment and to shipping, installations, and property in the vicinity. For Page 106 of 166 33 cases where the reduced extremes are used it is recommended that the hull should be raised to comply with the 50 year air gap requirements. It is also recommended that site developers consult with interested parties such as the MCA, third party installation owners and underwriters and environmental agencies in connection with the possible consequences. 10.2.6 The site-specifi c assessment shall be carried out in accordance with the guidelines and recommended practice contained in the SNAME TR5-5A “Guidelines for Site Specifi c Assessment of Mobile Jack-Up Units”. 10.2.7 The dynamic response of the jack-up shall always be considered and assessed in accordance with SNAME TR5-5A. 10.2.8 The assessment may be carried out at varying degrees of complexity. These are expanded below at increasing levels of complexity. The objective of the assessment is to show that the acceptance criteria are met. If this is achieved by a particular level there is no need to consider a more complex level. 1. Compare site conditions with the jack-up’s design or other previous site-specifi c assessments. Assessment carried out at this level is subject to confi rmation that the previous assessment was carried out in accordance with the Recommended Practice and the jack-up’s design, confi guration and footing load is substantially similar to the jack-up considered in the previous assessment. 2. Carry out appropriate calculations according to the simple methods given in SNAME TR5-5A. Possibly compare results with those from existing more detailed/complex calculations. 3. Carry out appropriate detailed calculations according to the more complex methods given in SNAME TR5-5A. Reference is requested to the SNAME TR5-5A fi gure 2.1 overall Ffowchart for the assessment when determining the appropriate level of complexity [Appendix G]. 10.2.9 The site-specifi c assessment shall consider the addition of wind loads on temporary accommodation modules, equipment containers, temporary crane installations and project cargo items (if any) that may not have been considered in previous assessments or design reports. 10.2.10 Assessments at all levels require verifi cation by a competent person to confi rm that the jack-up’s original design report or the site-specifi c assessment has been assessed in accordance with the recommended practice. It is recommended that in all cases where a permanently manned jack-up is to remain elevated in unrestricted mode, the assessment should be verifi ed by an independent third party such as a classifi cation society or marine warranty surveyor. Page 107 of 166 34 11. Self-propelled and propulsion assisted jack-ups 11.1 Self-propelled jack-ups 11.1.1 Self-propelled jack-up vessels considered in this guideline shall be defi ned as power-driven ships capable of undertaking sea passages within their certifi ed trading area under their own power and without tug assistance. Such vessels shall be assigned an appropriate class notation signifying their type and capability. 11.1.2 Self-propelled jack-ups may be considered to be capable of undertaking transits and fi eld moves under their own power; however, due consideration shall be given in each case to the need for tug assistance for port entry and departure, positioning on site, navigating in constricted waters and areas with high velocity currents and positioning in deep water with the legs fully extended below the hull. In some cases national government and local port regulations may require tug assistance regardless of the vessel’s own propulsion force. 11.1.3 For vessels certifi ed for unrestricted transit between locations without tug assistance the propulsion force of the vessel shall be suffi cient to maintain control under conditions with sustained wind velocity 20 m/s, head current velocity 0.5 m/s and signifi cant wave height 5m. 11.1.4 The design, construction, management, manning and operation of self-propelled jack-ups is governed by fl ag state and port state regulations, international codes and standards and classifi cation society rules for ocean-going ships. Certifi ed compliance with these regulations, standards and codes does not waive the requirement for these vessels to comply with the recommended practice. 11.2 Dynamically positioned Jack-ups 11.2.1 In addition to the defi nition and provisions described in 11.1 (above) dynamically positioned (DP) jack-up vessels considered in this guideline shall be defi ned as ships equipped with dynamic positioning systems that are capable of positioning and station keeping under their own power and without tug assistance. 11.2.2 DP jack-ups shall be assigned an appropriate class notation signifying their type and capability. They will usually comply with the propulsion power requirements for unrestricted transit as defi ned above. 11.2.3 DP jack-ups shall comply with IMO MSC Circ.645, “Guidelines for Vessels with Dynamic Positioning Systems” which is the principal internationally accepted reference on which the rules and guidelines of other authorities and organisations, including classifi cation societies are based and with recognised standards for DP training, which are set out in IMO MSC Circ.738 “Guidelines for Dynamic Positioning System (DP) Operator Training”. 11.2.4 It should be recognised that the requirements indicated above represent a minimum standard and that some companies and some owners may require more than just a certifi cate of class and a statement of condition and equipment. 11.3 Propulsion assisted jack-ups 11.3.1 Propulsion assisted jack-ups considered in this guideline shall be defi ned as all other jack-ups that may be fi tted with propulsion equipment but that do not match the defi nitions listed in section 11.1 and 11.2 (above) and that may require tug assistance for transit and positioning. Page 108 of 166 35 11.3.2 For transit of propulsion assisted jack-ups not certifi ed for unrestricted transit the vessel’s propulsion capacity shall be suffi cient to maintain a minimum speed over the ground of 2 knots in the environmental condition considered. 11.3.3 For transit and positioning of propulsion assisted jack-ups, the requirement for assisting tugs may be waived and/or a reduction in the number and power of tugs may be acceptable where it is demonstrated that eff ective control over the movement of the unit can be maintained in the limiting environmental conditions considered and with the legs extended below the hull to the maximum depth likely to be encountered en route and on site. 11.3.4 For transit, propulsion assisted jack-ups as defi ned in this guideline shall be considered the same as non-propelled jack-up barges with respect to the requirements described in section 12. Page 109 of 166 36 12. Non-propelled jack-ups 12.1 Manned and unmanned tows 12.1.1 Jack-up barges certifi ed for manned towage under the loadline rules and having certifi ed crew accommodation should be manned by a marine crew for location and fi eld moves. 12.1.2 Jack-up barges not certifi ed for manned towage under the loadline rules may carry a riding crew on location moves and will always be manned for fi eld moves. Provision shall be made for embarking and disembarking riding crews whenever necessary and suffi cient means of escape, fi refi ghting appliances and lifesaving equipment for the riding crew shall be available ready for deployment. 12.2 Ballasting 12.2.1 The ballasting system, if fi tted, should be in good condition and suitable for the following: • Correction of draught or trim • Damage control purposes in event of hull damage, grounding etc • Modifi cation to the draft, trim, or heel if required for installation on location 12.2.2 In cases where the jack-up is unmanned, specifi cations and operating instructions for the ballast system shall be readily available and retained on board the lead tug with details of the ballast status during the tow. 12.2.3 In cases where the jack-up is not fi tted with a permanently installed ballasting system and power source, the jack-up or the tug must carry suffi cient portable pumps and equipment to carry out the operations considered in section 12.2.1. 12.3 Watertight integrity 12.3.1 All weather deck openings shall have adequate securing arrangements to ensure watertight integrity. 12.3.2 Door openings on weather decks shall be fi tted with sills and deck hatches shall be fi tted with coamings in accordance with International loadline regulations. Exemptions for semi-permanently bolted closures not fi tted with sills or coamings may be accepted subject to approval by the classifi cation society. 12.3.3 Compartment manholes shall be properly secured with bolts and gaskets, which must be maintained in good condition. A set of tools shall be provided on board for releasing and re-fastening the manhole covers. 12.3.4 If manholes to critical compartments are covered by cargo, grillage or seafastenings, care shall be taken to ensure they are properly secured before being covered. 12.4 Barge deck openings 12.4.1 Barges having low freeboards, where there is risk that a portion of the deck may become fl ooded in the damage stability condition considered in section 6.7, should be provided with “top hats” with suitable means of fi xing to the barge deck, which can be used in an emergency to gain access through a manhole that may be awash. 12.4.2 At least one standpipe shall be provided with suitable fi ttings, such that it can be screwed into sounding cap holes that may be awash. 12.5 Mooring arrangements 12.5.1 This section is applicable to the general provision of moorings for jack-ups alongside quays. Moorings for jack-up operations afl oat on site are covered in section 14. Page 110 of 166 37 12.5.2 Mooring bitts or bollards shall be fi tted on either side of the jack-up, suitably spaced in accordance with Class rules if applicable. As a minimum, mooring bitts or bollards shall be fi tted on each side at each end of the barge. At least four suitably dimensioned mooring ropes in good condition shall be carried on board. If the towing tug has spare mooring lines then this may be considered as a part of the barge’s mooring lines. 12.6 Navigation lights and shapes 12.6.1 The jack-up shall be equipped with navigation lights (including anchor lights) and day signals in compliance with the international regulations for the prevention of collisions at sea. 12.6.2 The lights shall be provided with suffi cient power or fuel from an independent source to last for the duration of the voyage plus a reserve of 50%. 12.6.3 A full set of spare navigation bulbs or gas mantles (as appropriate) and shapes shall be carried on the tug or the barge. In addition, spare parts for the navigation lights such as cables or hoses and connections (as appropriate to the system) shall be carried. 12.6.4 Where obstruction or danger to navigation is caused or is likely to result from installation of the jack-up on site; and where it is required under consents granted under the provisions of the Coast Protection Act 1949 - Consent to Locate Off shore Installations – provision for marking off shore installations; the jack-up shall be equipped with obstruction lights (white 360 degree Morse “U”) displayed at each corner of the vessel and with a fog signal. 12.6.5 Small jack-up barges operating within port limits may carry alternative obstruction lights such as fl ashing orange beacons, subject to the approval of the harbour master. 12.7 Access 12.7.1 Safe ladders that extend from the manhole opening to the compartment bottom shall be provided in each compartment. 12.7.2 Ladders shall be available on each side of the jack-up, extending to the lowest water line, to permit access when afl oat. Steel ladders and adjacent protective fenders, if fi tted, shall comply with class rules if applicable. Rope ladders shall comply with the rules for the construction and rigging of pilot ladders. The condition of these ladders shall be checked by the master of the jack-up or the tug master prior to commencing each jack-up transit and they shall be checked by the person intending to use them immediately prior to each use. 12.8 Fenders 12.8.1 It is recommended that adequate fenders are provided for berthing operations. 12.9 Towing arrangements 12.9.1 The jack-up shall be towed from the forward end using a bridle of suitable construction. If two tugs are used, the bridle may be split and each tug connected to a single leg of the bridle. Alternatively the second tug may be connected with a wire towing pennant through a closed fairlead to a separate towing connection. 12.9.2 When assessing the strength of tow connections and fairleads on the barge and bridle, the eff ect of the tug pulling at its maximum bollard pull in any direction shall be considered. Page 111 of 166 38 12.9.3 All towing equipment shall be in satisfactory condition. Test certifi cates for all the items specifi ed in this section shall be valid and available for inspection. Certifi cates shall provide clear identifi cation of the respective equipment. 12.9.4 Alternative towing confi gurations appropriate to operations conducted in narrow channels and confi ned areas may be used in inland waters and within port limits. 12.9.5 A plan or drawing of the towing arrangement showing the confi guration of the towing gear and each component and stating the breaking load (BL) of each component shall be prepared and shall be made available on board the towing vessel. 12.10 Tow connections 12.10.1 Towline connections to the barge shall be of the quick release type where possible. For strength purposes they shall be located over the intersections of transverse and longitudinal bulkheads and they shall be provided with adequate back-up structure. They shall also be secured against premature release. 12.10.2 The breaking (ultimate) strength of the tow connections shall conform to the following: • At least three times the static bollard pull of the tug • Designed to be greater than the breaking load of the bridle 12.11 Fairleads 12.11.1 Capped fairleads or panama type fairleads shall be fi tted forward of and in line with the tow connection points except where the towing connection is installed at the deck edge. Anti-chafe protection shall be provided along the deck edge. 12.11.2 The breaking strength of the fairleads and their connections to the barge deck shall be greater than that of the bridle. 12.12 Towing bridle 12.12.1 The towing bridle shall consist of two legs having an included angle at the apex between 45 degrees to 60 degrees. 12.12.2 If the bridle is a chain bridle it shall be composed of stud link chain, with enlarged open links at each end to facilitate connections. Connection should be made without removal of the stud from the stud link chain. 12.12.3 If a composite bridle is used it shall comprise two lengths of stud link chain, extending beyond the deck edge, connected to wire pennants fi tted with hard eye thimbles. 12.12.4 The bridle legs shall terminate in a shackled connection at a towing ring, triangular (Delta) plate, or other approved and certifi ed device. 12.12.5 The breaking strength of each bridle leg and bridle terminator shall generally be at least three times the static bollard pull of the tug. Under no circumstances should the breaking strength of each leg of the towing bridle be less than the BL of the towing wire. 12.13 Intermediate Tow Pennant 12.13.1 For longer tows in the transit condition an intermediate wire tow pennant shall be included between the towing bridle and the tug’s main towline. The pennant shall be fi tted with hard eye thimbles, and shall be at least 10m in length. The pennant may be shorter or may be omitted if necessary to reduce the overall length of the tow gear for in harbour or fi eld moves. Page 112 of 166 39 12.13.2 The breaking strength of the wire pennant shall be not less than that of the main towline of the tug, and shall be of the same lay as the main towline. 12.14 Shackles 12.14.1 The certifi ed safe working load (SWL) of all shackles included in the towing arrangement shall be greater than the static bollard pull of the tug to be used. Some reduction in this requirement may be allowed for a tug with a bollard pull in excess of 100 tonnes, but in any event their breaking load shall be greater than three times the bollard pull. 12.15 Bridle retrieving arrangements 12.15.1 A retrieval system shall be provided to recover the bridle in the event of the towline parting. 12.15.2 The retrieving wire shall be connected at the bridle apex either to the triangular plate or to an end link of the bridle leg. The wire shall be either led back to a retrieving winch, suitably led via an “A” frame or block arrangement or an alternative system appropriate for the area of operation shall be provided. 12.15.3 The retrieving winch shall be adequately secured and the capacity of the winch shall be suffi cient to take the load of the bridle, apex connection, pennant and connections with some reserve. The winch drum capacity shall be such that the required length of retrieval wire can be spooled. 12.16 Emergency towing arrangements 12.16.1 Emergency towing arrangements shall be provided for use in the event of loss of towline or bridle recovery system or other unforeseen circumstances. Two systems are suggested below although modifi ed forms of these may be accepted: 1. Two spare towing connections shall be fi tted forward located inboard of the main connections. A bridle, which may be of chain or wire and chain with a triangular plate or towing ring at the apex, shall be attached to these connections. The towing ring or delta plate shall be secured to the barge by lashings. A pennant, with hard eye thimbles, shall be shackled to the towing ring or delta plate and clipped or lashed along the barge side, outboard of all obstructions. At the stern of the barge a fl oating line with a buoy attached shall be shackled to the end of the pennant and streamed astern. 2. A single spare towing connection shall be fi tted, located on the barge centre line either forward or aft. If the connection is fi tted forward, a pennant shall be connected to it and led aft to a fl oating line, as in alternative one (above). If the connection is fi tted aft the towing pennant shall be fl aked on deck with the fl oating line connected to it. 12.16.2 The pennants and towing connections shall, in either of the above alternatives, be sized similarly to the main towing equipment and shall be lead over the top of the main bridle if fi tted forward. 12.17 Anchor 12.17.1 The jack-up shall have at least one operable anchor during transit. The anchor is to be of suffi cient capacity and with suffi cient length of mooring line available for emergency anchoring. 12.18 Safety rails 12.18.1 The perimeter of the jack-up deck shall be protected by permanently installed safety rails or removable stanchions and safety wires. These shall be designed and constructed in compliance with the applicable rules (Classifi cation society or MCA MGN 280). Openings in the rails or wires allowing for temporary access for mooring lines or other equipment shall be closed with chains or ropes when not in use. Page 113 of 166 40 13. Towing vessels 13.1.1 The proposed tug(s) shall be in satisfactory condition. The tug(s) and towing equipment, machinery, manning and fuel requirements shall be suitable for the proposed operation. Certifi cation and documentation required by the fl ag state shall be in order and the tug shall be classed by a recognised class society or certifi ed under the provisions of the MCA Small Commercial Vessel (SCV) and Pilot Boat Code (as currently set out in MGN 280) or foreign equivalent. 13.1.2 The tug(s) shall be provided with a Bollard Pull Test Certifi cate stating the continuous (sustained) bollard pull based upon a bollard pull test carried out within the last 10 years. 13.1.3 All towing equipment shall be in satisfactory condition. Test certifi cates for all items shall be valid and shall be available for inspection with clear means of identifi cation of the respective equipment. 13.1.4 The towing vessel shall have a spare towline that shall be similar in all respects to the main towline. Where the spare towline is not spooled on to a second winch drum it shall be stowed in such a manner that it can be spooled on to the main towing drum by the crew at sea. 13.2 Bollard pull requirements 13.2.1 The total environmental load acting on the jack-up and cargo due to the combined eff ects of the following conditions shall be calculated and the minimum tow-line pull required (TPR) should be calculated to hold the jack-up at zero forward speed in a fully developed gale defi ned as: • Signifi cant wave height (Hs): 5m • Wind speed: 20 m/s (approx. 40 knots) • Current: 0.5m/s (approx. 1 knot) 13.2.2 For short coastal tows, fi eld and harbour moves, lesser criteria for calculation of TPR may be agreed. Generally these should not be reduced below 15 m/s wind speed, 2.0m signifi cant wave height and 0.5m/s current, acting simultaneously. 13.2.3 The tow should be capable of making reasonable speed with average weather conditions throughout the passage. It is recommended that the tow be capable of maintaining a minimum speed of 5 knots in conditions with signifi cant wave height 2.0m and wind speed 10m/s. 13.2.4 In all cases due consideration shall be given to the number of tugs and the TPR required to control the jack-up in the anticipated maximum current on site with the legs fully extended below the hull. 13.2.5 The TPR should be related to the continuous static bollard pull (BP) of the tug(s) proposed by: TPR = Σ(BP x Te/100) Where: Te is the tug effi ciency in the sea conditions considered, % BP is the continuous static bollard pull of each tug (BP x Te/100) is the contribution to the TPR of each tug Σ is the sum for all tugs assumed to contribute to the TPR. Page 114 of 166 41 Bollard Pull BP ≤ 30 BP 30 - 90 BP > 90 80 80 80 50 + BP 80 80 H.sig Signifi cant wave height, metres BP Continuous static bollard pull, tonnes Te Tug effi ciency, in percentage of the bollard pull 30 + BP 52.5 + BP/4 75 BP 7.5 + 0.75 x BP 75 Calm H.sig = 2.0 m H.sig = 3.0 m H.sig = 5.0 m Table 13.1 - Estimation of the tug effi ciency 13.2.6 The tug effi ciency, Te, depends on the size and confi guration of the tug, the sea state considered and the towing speed achieved. In the absence of alternative information, information, Te may be estimated according to table 13.1 (below). 13.3 Towing winches 13.3.1 Towing vessels shall be fi tted with a suitable towing winch. Towing from a towing hook will not be accepted for open sea passages but may be accepted for harbour moves or movements in inshore sheltered waters. 13.3.2 Two towing drums shall normally be provided. Where a second towing drum is not fi tted then means of reconnection of the spare towline shall be supplied. The spare towline shall be in good condition and of the required strength. There must be suitable means for connecting the line to the tug and making a rapid reconnection to the emergency towline on the towed barge. 13.3.3 The tow winch shall have a minimum holding power of three times the static bollard pull of the tug at the inner layer on the drum. 13.3.4 All towing winches shall be fi tted with an emergency release brake mechanism. 13.4 Towline control 13.4.1 Towing pods where fi tted shall be of adequate strength, and well faired to prevent snagging. 13.4.2 Alternative arrangements for towline control may be accepted. If gog ropes are used they should be adjustable from a remote station. If a single gog rope system is fi tted then the connection point shall be on the centreline of the vessel. A spare gog rope shall be provided. 13.4.3 Mechanical, hydraulically or manually operated stops (pins) to control the towline shall, if fi tted, be well maintained, and capable of being withdrawn or removed when not in use. 13.5 Towing wire 13.5.1 For jack-up location moves the length of the tow wire should never be less than 500m and shall be determined as follows: L = (BP/BL) X 1200m. Page 115 of 166 42 13.5.2 For harbour moves and tows in inshore sheltered waters diff erent tow wire lengths may be accepted. 13.5.3 The wire shall be in good condition, free from kinks, snags and with no opening of strands. Hard eye thimbles or towing sockets shall be fi tted. 13.5.4 The MBL of the towing wire shall not be less than the following values: 13.5.5 Synthetic rope towlines shall not be used by the main towing vessel for jack-up location or fi eld moves. Synthetic fi bre towlines may be used by assisting tugs for harbour moves or tows in inshore sheltered waters. 13.6 Stretchers 13.6.1 Stretchers (if used) shall only be connected between the tug’s wire and the intermediate pennant and not to the bridle apex connection. In general, a stretcher made up as a continuous loop is preferable to a single line. The breaking load shall at least 1.5 times that of the main towline, and hard eye thimbles are to be fi tted at each end. These ropes are to be in good condition. 13.7 Tailgates/stern rails 13.7.1 The tailgate or stern rail, if fi tted, shall have an upper rail of radius not less than 10 times the diameter of the main towline. Smaller diameter may be accepted for inland tows and harbour moves. 13.7.2 Anti-chafe gear shall be carried on the tug and fi tted as necessary. The stern rail shall be well faired to prevent snagging. 13.8 Additional equipment 13.8.1 The following additional equipment shall be carried on board the towing vessel: • Oxygen/acetylene cutting equipment • Damage control equipment • Spare shackles (sized in accordance with the towing gear plus smaller sizes) • A searchlight to illuminate the tow and if the jack-up is unmanned: • Portable radio transmitter/receivers with spare batteries for communication • Hand lamps or torches with spare bulbs and spare batteries • A powered workboat fi tted with adequate means of launching and recovery (Excepting small tugs < 24m in length) • A portable pump equipped with suffi cient length of suction hose to enable dewatering of the compartments considered in section 6.7 and a self-contained power unit with suffi cient fuel for 12 hours running Bollard Pull (BP) Less than 40 tonnes 40 to 90 tonnes Over 90 tonnes 3 x BP (3.8 – BP/50) x BP 2 x BP BL Page 116 of 166 43 13.9 Bunkers An adequate quantity of fuel and consumables shall be on board for the proposed tow. An adequate amount of fuel at full speed consumption shall be kept in reserve. 13.10 Manning 13.10.1 The towing vessel shall be manned by a qualifi ed and experienced crew in compliance with the requirements of the tug’s fl ag state. There should be suffi cient crew to deal with contingencies such as the parting of a tow wire and the need to board the tow in the case where the towed jack-up is unmanned. 13.10.2 For towage of unmanned jack-ups there must be suffi cient accommodation and certifi ed life-saving capacity to accommodate the barge riding crew (if assigned) on board the towing vessel(s). Page 117 of 166 44 14. Moorings for positioning 14.1 General 14.1.1 Positioning is defi ned as the marine operation necessary to move the jack-up into the required position at a new location and to carry out the jacking and preloading operations necessary to install the unit on location. 14.1.2 All positioning operations are weather restricted and are to be conducted in sea states not exceeding the jack-up’s design limits for going on location (engaging the bottom). This means that the operation must be completed within 72 hours to the point where a temporary safe condition has been achieved. 14.1.3 The jack-up shall be considered to have reached a temporary safe condition when the integrity of the seabed foundation has been proven by preloading and the unit is capable of: a. Withstanding the reduced environmental loads selected for a weather restricted operation. or b. Withstanding the environmental loads corresponding to the 10 year seasonal condition for an unrestricted operation. A permanent safe condition for unrestricted elevated operation has been achieved when the unit can withstand the environmental loads corresponding to the 50 year all-year condition for the location. 14.1.4 Plans for positioning operations shall state the environment limits that are not to be exceeded. The limits shall not exceed the allowable criteria for engaging the bottom and/or for jacking and preloading as prescribed in the jack-up’s operating manual. 14.2 Positioning systems 14.2.1 When positioning close to surface or sub-sea structures, pipelines or cables and whenever fi ne positioning tolerances are required, jack-ups relying on dynamic positioning systems shall be assigned the appropriate class notation for dynamic positioning (DP). The capacity of the DP system shall be documented to demonstrate the vessel’s capacity to operate in DP mode in the defi ned environmental criteria and the system shall be function tested with acceptable results prior to commencing each positioning operation. 14.2.2 When positioning close to surface or sub-sea structures, pipelines or cables and when fi ne positioning tolerances are required, jack-ups not equipped with DP systems and all non-propelled jack-ups shall be equipped with a suitable mooring system except as provided in 14.2.3 and 14.2.4 (below). 14.2.3 At locations where positioning tolerances are less critical and where there is low risk of contact with any proximate surface or seabed obstruction, self propelled jack-ups may position using their propulsion system alone provided that the system is capable of controlling the jack-up’s speed and heading so as to reliably achieve a constant heading and near-zero horizontal movement relative to the seabed in the environmental conditions considered. 14.2.4 At locations where positioning tolerances are less critical and where there is no risk of contact with any surface or seabed obstruction, non-propelled jack-ups may position using tugs alone provided that the towing vessels are capable of controlling the jack-up’s speed and heading so as to reliably achieve a constant heading and near-zero horizontal movement relative to the seabed in the environmental conditions considered. 14.3 Mooring equipment and procedures for positioning afl oat 14.3.1 Mooring equipment for jack-ups (if fi tted) will normally consist of a four point mooring system using mooring winches, wires and anchors. The mooring system shall be designed and constructed and maintained in accordance with the rules of the vessel’s classifi cation society. Page 118 of 166 45 14.3.2 When positioning close to surface or subsea structures, pipelines or cables a mooring layout plan shall be prepared. Additionally a mooring analysis shall be performed if it is necessary to determine the clearances between the mooring lines and the nearby structures (see 14.4). Further details regarding the mooring analysis are given in 14.5. 14.3.3 The capacity of the mooring system, including the holding capacity of the anchors in the soil conditions on site shall be demonstrated as suffi cient to withstand the loads likely to be imposed during positioning of the jack-up in the environmental conditions considered. 14.3.4 The system shall be subject to regular survey and shall be maintained in good condition. The manufacturer’s test data stating the safe working load of the winch, the rated pulling capacity (fi rst wrap) and the rated brake holding capacity together with original certifi cates for each mooring wire, termination socket (if fi tted), shackle, anchor pennant and anchor shall be kept on board the jack-up. 14.3.5 In cases where the mooring winch is to be operated manually from a local control and where the operator can maintain a clear view of the winch drum, the fairlead, and the portion of the wire above the sea surface, the monitoring of line length and tension may be accomplished visually. 14.3.6 In cases where the mooring winch is operated remotely from a central control the equipment shall be fi tted with means of displaying length and tension data at the control station. If there is no clear view of the winch drums from the control station then either CCTV coverage shall be fi tted or competent crew equipped with radios shall be stationed safely in the vicinity of each winch to monitor the spooling of wires. 14.4 Clearances during positioning 14.4.1 Suffi cient clearance should be maintained between the jack-up and adjacent structures or other vessels and between mooring lines and fi xed structures or other vessels and sub-sea pipelines and cables during positioning. The direction of movement to the fi nal position and the environmental conditions shall be considered in order to establish suffi cient clearance. 14.4.2 The minimum clearance between the jack-up hull and an adjacent structure or another fl oating vessel during positioning should not be less than 3m at any point during the positioning operation. 14.4.3 The minimum clearance between the jack-up’s leg footings and an adjacent structure should not be less than 5m at any point during the positioning operation. The minimum clearance between the jack-up’s leg footings and a subsea pipeline or cable should not be less than 10m at any point during the positioning operation. 14.4.4 Smaller clearances may be accepted following a thorough review of the characteristics of the site, the procedures to be adopted, the limiting environmental conditions, back-up systems such as thrusters, lowering the legs to engage the seabed, the use of fenders and the deployment of sonar sector scan equipment when positioning close to subsea pipelines or cables. Due consideration shall be given to the consequences of contact and the ability to remove the jack-up from the location following completion of the operation. 14.4.5 The minimum clearances described below are based on the understanding that anchors are deployed from an anchor handling tug equipped with a DGPS based tug management system that has been specifi cally calibrated for the selected site. Greater clearances shall be allowed where this equipment is not fi tted or is not in service. Page 119 of 166 46 14.4.6 Greater clearances than those described in this section are usually required around ‘hot’ hydrocarbon installations and pressurised pipelines. Anchors shall not be deployed within designated pipeline or cable corridors or exclusion zones. Note that exclusion zones may include areas excluded in marine and environmental permits. 14.4.7 Port authorities, gas and oilfi eld pipeline operators and other concerned parties may have more stringent clearance requirements related to the protection of critical pipelines and sub-sea or overhead electrical and communications cables. These must be complied with. 14.4.8 The clearance between a jack-up mooring line and a fi xed structure or fl oating vessel during positioning shall not be less than 5m. 14.4.9 The horizontal clearance between a jack-up mooring line not crossing (parallel to) a sub-sea pipeline or cable should not be less than 50m. The vertical clearance between a jack-up mooring line crossing a sub-sea pipeline or cable should not be less than 5m. Smaller clearances may be accepted provided that it can be demonstrated that there is no risk of contact between the mooring line and the pipeline or cable. 14.4.10 The horizontal clearance between a jack-up’s anchor and a fi xed structure or sub-sea pipeline or cable shall not be less than 250m if laid across, or 150m if laid parallel to the pipeline or cable. This clearance may be reduced to 50m if the anchor drag sector is away from the pipeline or cable. 14.4.11 Contact between individual lines is not accepted for crossing anchor lines from two or more vessels. 14.4.12 Minimum recommended clearances are tabulated below: Element Jack-up hull Leg footing Mooring line Mooring line Anchor Anchor Anchor Any Any Not crossing Crossing Drag sector away Drag parallel to Drag sector toward 3m 5m 5m 5m 50m 150m 250m - 10m 50m - 50m 150m 250m 3m (afl oat) 3m (afl oat) - 5m - - - Direction Fixed structure or fl oating vessel Horizontal Subsea pipeline or cable Vertical Recommended minimum clearances during positioning 14.5 Mooring analysis 14.5.1 For positioning a jack-up in non-critical locations a mooring layout plan shall be prepared. 14.5.2 For long term moorings defi ned as any mooring system that is deployed not solely for positioning purposes but also for the purpose of station-keeping the mooring arrangements should comply with the guidelines contained in section 14.4 (above) and should be analysed for the appropriate environmental conditions applicable to the season and time period for which the unit will be moored. Page 120 of 166 47 14.5.3 Mooring systems used for the purpose of station-keeping may, in general, be analysed by quasi static methods unless the unit is moored close to a fi xed or fl oating structure or any natural hazard or obstruction that could result in contact damage in which case dynamic analysis should be performed. The analysis should describe the possible excursions under defi ned environmental loads and should demonstrate that there is no risk of contact between the jack-up or its mooring lines and the proximate fi xed or fl oating structure or other obstruction with the moorings intact and in the single line failure mode. 14.6 Anchor handling tugs 14.6.1 Anchors should be deployed by anchor handling tugs. These vessels should be equipped with bow or stern rollers and winches, jaws, forks, pins, release devices and safety rails as appropriate for the safe control of the anchors and wires and to ensure proper protection for the tug crews. 14.6.2 Anchor handling tugs engaged in deploying anchors in the vicinity of fi xed structures or sub-sea pipelines or cables should be equipped with a DGPS based tug management system that has been calibrated for the selected site. 14.6.3 An anchor handling tug carrying an anchor across a sub-sea pipeline or cable should carry the anchor on deck and not suspended from the stern roller. 14.7 Anchor handling procedures 14.7.1 Anchor handling procedures shall be documented. The procedures shall include scale anchor plans and shall describe the complete anchoring operation, the mooring equipment and details of the method of deploying and recovering anchors. The procedure shall include contingency plans for vessel and equipment malfunction or breakage. 14.7.2 The procedure shall also include a plan showing areas where anchors may not be deployed for any reason and shall describe the precautions to be taken to avoid contact between anchors and mooring wires and fi xed structures, subsea pipelines and subsea cables where applicable. 14.7.3 Where required to maintain the vertical clearances (section 14.4) these precautions may include the deployment of line buoys (damage preventer buoys) installed at points along the length of the mooring wire to prevent it from coming into contact with subsea pipelines or cables. Additional precautions may also be necessary concerning the maintenance of tension in moorings during deployment and recovery to ensure that slack bights of wire do not contact fi xed structures, subsea pipelines and cables. 14.7.4 Where the risk of contact between mooring wires and subsea cables and/or contact with the seabed in the vicinity of cables buried to a depth of 1m or less cannot be avoided by using line buoys then means of protecting the sub-sea cables such as rock dumping, concrete/steel mattresses or bolted steel cable protectors shall be employed. 14.7.5 Anchor plans should be reviewed and approved by the owners or operators of fi xed structures, subsea pipelines and cables in the vicinity. 14.7.6 Prior to commencing anchor handling the master of the jack-up and/or the tow master (if the master is not the tow master) should arrange a meeting with the tug master(s) of the anchor handling tugs and the survey team to discuss the procedures to be adopted and the safety precautions to be observed. Sequential operations involving the same procedures, equipment and personnel may be addressed at a single meeting. Page 121 of 166 48 15. Lifting and load transfer 15.1 General 15.1.1 Lifting operations and lifting equipment shall comply with the Lifting Operations and Lifting Equipment Regulations 1998 (S.I.1998/2307) (LOLER). These regulations are supported by the HSE’s technical guidance and approved codes of practice contained in: • Technical guidance on the safe use of lifting equipment off shore • Safe use of lifting equipment – approved code of practice and guidance 15.1.2 Marine Lifting Operations shall also comply with the instructions and recommendations contained in a recognised guideline document, such as:- • GUIDELINES FOR MARINE LIFTING OPERATIONS Noble Denton 0027/ND Rev 7 – 15, April 2009 • LOC Guidelines for Marine Operations – Marine Lifting: LOCG-GEN-Guideline 003 Rev. 0, May 2003 • Det Norske Veritas (DNV) Rules for the Planning and Execution of Marine Operations, January 2000. Chapter 5: Lifting • MCA MGN 280 (M) Small vessels in commercial use for sport or pleasure, workboats and pilot boats - alternative construction standards MS+FV lifting operations and lifting equipment regulations 2006. The Documents listed above are mainly concerned with lifting operations by fl oating crane vessels; therefore the following section of this document provides additional information on marine lifting operations carried out by jack-ups. 15.2 Planning 15.2.1 Operational planning shall be based on the use of well-proven principles, techniques, systems and equipment to ensure acceptable Health and Safety levels are met and to prevent the loss or injury to human life and major economic losses. 15.2.2 All planning for load out and off shore lifting operations is based where possible on the principle that it may be necessary to interrupt or reverse the operation. However, this may be impractical for some operations and in cases where the operation cannot be reversed, points of no return, or thresholds, shall be defi ned during planning and in the lifting manual. Checklists should be drawn up detailing the required status to be achieved before the operation proceeds to the next stage. 15.2.3 A comprehensive lifting manual shall be prepared. This manual may form part of an installation manual for the module or component to be lifted and shall include, as a minimum, details of the following: • Description of the operation • Time schedule • Lift module dimensions weight and COG • Details of stabbing guides and beams (if used) • Details of auxiliary winches and tag lines • Details of the jack-up and attending vessels (tugs, transport barges etc) • Jack-up station keeping arrangement (jacked up, leg-stabilised, moored afl oat, DP) • Transport barge station keeping arrangement • Specifi c operations (ballasting, ROV, divers, survey measurements etc) • Vessel positioning procedures • Confi guration and certifi cation of the crane • Certifi cation of all lifting equipment Page 122 of 166 49 • Crane radius curve (manufacturers/class de-rating of crane when afl oat if applicable) • Proposed clearances between lifted module/crane/legs/vessels/existing structures • Lifting equipment details, rigging weights and rigging drawings • Limiting environmental criteria for each lift • Plan and profi le drawings • Organisation, communications and responsibilities • Recording procedure • Pre-lift checklist • Safety and contingency plans 15.3 Documentation and design calculations 15.3.1 Each crane shall be provided with a report of inspection and a valid certifi cate of test. Permanently mounted vessel’s cranes shall be certifi ed by the jack-up’s classifi cation society and details of annual inspections and fi ve year tests shall be recorded in the vessel’s lifting gear register. 15.3.2 The lifting capacity of the crane shall be defi ned and the basis for the load/radius curve shall be clearly described in the crane manual or similar document. When mobile cranes are used onboard the jack-up, care shall be taken to determine whether the weights of crane blocks, hooks and wires have been included or excluded in the defi ned lifting capacity. 15.3.3 Temporary and mobile cranes not forming part of the jack-up’s permanent equipment shall be certifi ed and shall be seafastened in accordance with the provisions of section 7. 15.3.4 Reference is requested to the fl owcharts contained in the referenced guideline documents on marine lifting (section 15.1.2) which provide a useful summary of the stages in the design and analysis of lifts using a single crane or two cranes. 15.4 Loads and analysis 15.4.1 The module design weight (MDW) shall include adequate contingency factors to allow for the module being heavier than intended. After completion, the module shall be weighed using an approved weighing method. The as-weighed weight shall be increased by 3% to account for weighing inaccuracies. Documentation should be provided to demonstrate that the equipment and procedures adopted for weighing have the required accuracy. 15.4.2 A further component, the rigging weight (RW), shall be added to the MDW. This allowance represents the weight of the lift rigging and shall include the estimated weight of all shackles, slings, lifting beams, spreaders and rigging platforms. In the fi nal design phase the actual weight of rigging (including contingencies) shall be used. 15.4.3 The plan position of the centre of gravity shall generally be restricted for the following reasons: • To allow for the use of matched pairs of slings • To prevent overstress of the crane hook • To control the maximum tilt of the object The module COG should be kept within a specifi ed design envelope. The length of the lifting slings/grommets shall be chosen to control the tilt of the module. For practical purposes the tilt of the module should not exceed 2 degrees, however some modules require fi ner vertical tolerance for installation. Page 123 of 166 50 15.4.4 RW shall be added to the MDW to give the static hook load (SHL): MDW + RW = SHL. The SHL shall be checked against the approved crane capacity curve at the maximum planned outreach. 15.4.5 Where the lifting situation may give rise to a dynamic increase in the eff ective load the dynamic hook load (DHL) shall be obtained by multiplying the SHL by a dynamic amplifi cation factor (DAF): DHL = SHL x DAF. The DAF allows for the dynamic loads arising from the relative motions of the crane vessel and/or the cargo barge during the lifting operations. The DHL shall be checked against the approved crane capacity curve at the maximum planned outreach. 15.4.6 For lifts in air the dynamic load is normally considered to be highest at the instant when the module is being lifted off its grillage. This load, and hence the appropriate DAF, should be substantiated by means of an analysis which considers the maximum relative motions between the hook and the cargo barge and takes account of the elasticity of the crane falls, the slings, the crane booms and the luffi ng gear. 15.4.7 The description of such an analysis must clearly state the assumed limiting wave heights and periods such that, if the calculated value of DAF is critical to the feasibility of the operation, then those conducting the lift will be aware of the limiting seastates. 15.4.8 In the absence of a dynamic lift response analysis being carried out the values of DAF given in table 15.4.8 may be used for lifts in air from a jack-up. 15.4.9 It should be noted that some crane capacity curves already take due account of the DAF and care should be taken to ensure that the DAF is not considered twice in the design calculations. Weight of module Lift off shore Lift inshore Lift off shore Lift off shore Lift inshore Floating mode lifting from vessel afl oat Elevated mode lifting from vessel afl oat Elevated mode lifting from leg stabilised barge or jack-up Elevated mode lifting from quayside 1.50 1.30 1.15 1.00 1.00 1.40 1.20 1.10 1.00 1.00 N/A N/A 1.05 1.00 1.00 < 100 tonnes 100 – 1,000 tonnes Horizontal Table 15.4.8: DAF factors for jack-up Page 124 of 166 51 15.5 Minimum clearances During all phases of a lift the following minimum clearances should be maintained. Recommended clearances are tabulated below. Smaller clearances may be accepted following a thorough review of the characteristics of the lift, the procedures to be adopted, the limiting environmental conditions and the consequences of contact. 15.6 Jack-up crane vessel stability 15.6.1 For a jack-up lifting in the afl oat condition, load and stability calculations shall be provided to demonstrate that the condition at each stage of the lift operation is within the limits contained in the stability book and/or the operating manual. 15.6.2 A failure mode and eff ects analysis (FMEA) is a requirement of class for DP jack-ups. The requirement for an additional FMEA or otherwise for a DP jack-up during lifting or positioning shall be determined in consideration of the risk to persons, DP class, proximity of other structures or vessels, lifting confi guration, operating environment and any other factor particular to the circumstances of the proposed operation. 15.6.3 For a jack-up lifting in the elevated condition it shall fi rst be verifi ed that the preload operation has been carried out in accordance with the instructions contained in the operating manual and/or in accordance with any approved site-specifi c procedures that may have been developed for the location. 15.6.4 For a jack-up lifting in the elevated condition, load calculations shall be provided to demonstrate that the load condition at each stage of the lift operation is within the limits stated in the operating manual and that the jack-up’s maximum allowable elevated weight (operating) and centre of gravity remains within the specifi ed transverse and longitudinal limits throughout the lifting operation. The calculations shall demonstrate that, during lifting and slewing, individual leg loads will not approach or exceed the legs loads achieved during preloading. 15.6.5 Caution shall be exercised at locations where the seabed foundation may have become altered by scour or other eff ect over time. In such cases the jack-up preload or pre-drive sequence should be repeated prior to commencing a lift operation. The jack-up should be precisely levelled prior to commencing a lift operation. 15.6.6 Jack-ups with four or more legs should ensure that the leg loads are equalised before lifting in order to reduce the risk of further slight settlement during the lift operation. Following this test the leg loads should be adjusted (if required) to the prescribed loads for lifting and locking devices, fi xed catches or pins should be engaged (if required) in accordance with the instructions contained in the operating manual. 15.6.7 When carrying out lifts with two cranes, documentation should be submitted to demonstrate that the jack-up crane vessel can safely sustain the changes in hook load which arise from the tilt and yaw factors combined with environmental eff ects in the lifting calculations, specifi cally considering allowable cross lead angles for the crane booms. Jack-up 3m 3m 3m 3m 3m Below the lifted module Between module and jack-up legs Between module and crane boom Between spreader bar and crane boom Between module and fi xed structure 1m 1m 1m 1m 1m Floating mode Elevated mode Page 125 of 166 52 16. Crew transfer 16.1 Principal requirements 16.1.1 Equipment shall be provided to allow the crew, project personnel and visitors to safely embark and disembark when the jack-up is: • Moored afl oat or elevated at a quayside • Afl oat or partly elevated with the hull at draft inshore or off shore • Elevated inshore or off shore It should be recognised that there will be operational circumstances in which safe access cannot be provided and at which time transfer of personnel should not be attempted. 16.1.2 The access equipment shall comply with the following regulations and codes: • The Merchant Shipping (Means of Access) Regulations SI 1988/1637 • The Merchant Shipping (Safe Movement Onboard Ships) Regulations 1988 • MCA Code of Safe Working Practice for Merchant Seamen • MCA Small Commercial Vessel and Pilot Boat (SCV) Code as set out in MGN 280 The responsibility for the provision and maintenance of the jack-up’s access equipment shall be the responsibility of the jackup owner or operator. 16.1.3 Routine access to and from the jack-up will normally be from the quayside or off shore platform (or other fi xed structure) or barge or from a crewboat. The term crewboat shall be deemed to include tugs, workboats or RIBs used for personnel transfer. Transfer of personnel by helicopters has not been considered in this guideline. 16.1.4 The safe condition of quaysides and quayside equipment, off shore platforms and crewboats used for the transfer of personnel to and from jack-ups shall be the responsibility of the party who owns or operates the quayside, platform or crewboat. Crewboats shall be constructed, maintained, equipped, manned, and operated in accordance with the rules laid down by their registry and class or in accordance with the SCV code, as applicable. 16.1.5 The master of the jack-up and master of the crewboat and the person supervising the transfer shall ensure that the selected method of transfer of personnel to and from the jack-up is safe in the prevailing circumstances and that equipment used for the transfer is in satisfactory condition and has been properly rigged and/or prepared for the transfer. In assessing the level of safety the master of the jack-up should be guided by the instructions and recommendations contained in the site-specifi c documented transfer procedure. 16.1.6 The master of the jack-up and/or the person supervising the transfer shall also ensure that all transferees have received the required training in the selected method of transfer and that the appropriate PPE is worn for each transfer. 16.1.7 Each person using a gangway, ladder, personnel carrier or other device for transfer to/from a jack-up, off shore platform, crewboat or quayside shall individually and separately accept responsibility for their own safety. No person should attempt a transfer at any point unless they have received the appropriate training and instruction and are confi dent that they can accomplish the movement safely. 16.1.8 The safe operation of the jack-up and/or platform and/or crewboat is the responsibility of the owner/operators, as applicable. The individual responsibilities of the transferee and the vessel masters and crew involved in supervising transfers, or operating equipment used for transfers, shall be clearly established and documented. Page 126 of 166 53 16.1.9 Specifi c procedures for routine personnel transfer shall be clearly established and documented. For each mode of transfer these procedures should, as a minimum, include details of the equipment to be used, equipment and transfer mode operating limits, training and PPE requirements, provision of safety equipment, communications protocols and the instructions to be given and checks to be carried out prior to each transfer. 16.2 Transfer when the jack-up is moored afl oat or elevated at a quayside 16.2.1 When the jack-up is positioned at a quayside the transfer of personnel should be accomplished using an approved gangway and associated equipment that complies with the Merchant Shipping Regulations (means of access) 1988. The gangway shall be rigged in accordance with the advice contained in the UK Code of Safe Working Practice for Merchant Seamen. 16.2.2 A dock mounted stair tower shall be provided in circumstances where there is a signifi cant diff erence in height between the jack-up deck and the quayside, such that the angle of inclination of the gangway, if used alone, would exceed its design limits. 16.2.3 Stepping over from the jack-up to/from the quayside shall be avoided, even in cases where the gap is small and the jack-up deck and quayside are level or almost level. Scaff olding, planks and other temporary equipment shall not be used for the transfer of personnel to/from the quayside. 16.3 Transfer when the jack-up is afl oat or partly elevated with the hull at draft 16.3.1 When the jack-up is afl oat underway or positioned on location with the hull at draft the transfer of personnel to/from a crewboat shall be accomplished using a fi xed steel boarding ladder (if fi tted) or an approved rope ladder rigged on the lee side or end of the jack-up. A rope ladder (if used) shall be constructed and rigged in accordance with the advice contained in the U.K. Code of Safe Working Practice for Merchant Seamen. 16.3.2 Personnel may transfer directly from the jack-up to/from the crewboat without using a ladder in cases where: • The crewboat has a boarding platform fi tted with a safety rail • The personnel transferring are not required to climb over the safety rail • The height of the boarding platform is almost level with the jack-up’s deck • The vertical movement of the boarding platform in the sea state is ≤ 30 cm • The jack-up’s boarding point has an access opening in the deck rail or bulwark • The boarding point is manned, lighted and equipped with a lifebuoy and line 16.3.3 The jack-up’s fast rescue craft, man overboard boats, workboats or RIBs fi tted with class approved davit launch and recovery systems may be used for the occasional transfer of trained seamen and divers. Such transfers should be subject to a specifi c risk assessment. 16.3.4 Transfer using personnel baskets and man-riding cranes should not be attempted while the jack-up is in the fl oating mode. 16.4 Transfer when the jack-up is elevated on location 16.4.1 When the jack-up is elevated to an air gap on an inshore or off shore location the transfer of personnel to/from the jack-up is usually accomplished using. • Bridge to adjacent fi xed structure (e.g. wind/current turbine or platform). (Further reference is required for specifi c guidance on turbine access) Page 127 of 166 54 • Man-riding crane and certifi ed personnel carrier • Other approved mechanical device certifi ed for manriding 16.4.2 The use of fi xed steel ladders or rope ladders for access by personnel to elevated jack-ups requires extreme caution and should only be attempted in slight sea conditions. Plans for the use of rope ladders should be subject to special consideration and specifi c risk assessment. 16.4.3 The capacity of purpose built bridges and gangways used for access shall be certifi ed, or in the absence of a certifi cate, a report on the structural capacity from a competent person shall be provided. 16.4.4 Man-riding cranes shall comply with LOLER regulations. In addition a certifi cate or report shall be provided to demonstrate that the man-riding crane is equipped in accordance with the guidance provided in HSG 221. 16.4.5 Transfer of personnel by personnel basket or other carrier shall be undertaken in accordance with the guidance contained in HSE off shore information sheet, January 2007: Guidance on Procedures for the Transfer of Personnel by Carriers. The type of personnel carrier used shall comply with guidance contained in HSG 221. Page 128 of 166 55 17. Marine control for jack-up operations 17.1 Marine control during transit and positioning 17.1.1 Jack-ups in transit and during positioning shall comply with the applicable marine traffi c regulations promulgated by the port state controlling the waters through which the transit is made and in which the jack-up is positioned. The jack-up owner or operator shall be responsible for compliance with these regulations. 17.1.2 Jack-up transit and positioning operations usually require notices to mariners to be issued in advance, during, and on completion of each movement. Regulations also require that routine reports are made to vessel traffi c services wherever applicable. The jack-up owner or operator shall be responsible for ensuring that the required notices, advisories and warnings are issued and for maintaining communication with the maritime authorities concerned. 17.1.3 Jack-ups operating within port limits shall comply with rules promulgated by local port or river authorities, pilot services and harbour masters. The jack-up owner or operator shall be responsible for maintaining communication with the marine authorities that operate or exercise control in the area through which the jack-up is transiting and in which the jack-up is operating. 17.2. Nearshore and off shore project sites 17.2.1 In addition to large scale navigational charts, jack-ups operating at marine project sites shall be provided with large scale drawings of the project site in both hard copy and electronic format where such fi les are in use on the jack-up’s survey system. The drawings shall contain information plotted using a system of co-ordinates that is compatible with the survey system in use on the jack-up and they shall be continuously updated to refl ect both natural and man-made changes as they occur. The following information shall be included: • Bathymetry • Seabed surface features including debris and obstructions • Position, dimensions and depth of any previous jack-up ‘footprints’ • Position and dimensions of fi xed surface and subsea structures • Positions (as laid) of all subsea pipelines and cables and proposed cable routes • Positions and heights of overhead cables • Positions of vessels and anchors of units on long term moorings • Clear fairways and exclusion zones • Designated zones within the site together with notation on the reason for zoning 17.2.2 Jack-ups operating as single isolated units and attended only by their towing vessels (if any) require no additional marine control system. Masters of towing vessels (if any) shall be provided with the procedure document or method statement for the proposed transit and positioning operation and they shall be briefed by the master of the jack-up in advance of the proposed movements. 17.2.3 For jack-ups operating off shore it is recommended that a 500m radius exclusion zone centred on the unit’s position be maintained during positioning and elevated operations. No other vessel should enter or move within this exclusion zone until clearance has been received from the master of the jack-up. A lookout on the jack-up or the attending tug should be maintained throughout operations on site. Rogue vessels or small craft approaching the zone without notice should be advised by all available means to avoid this zone. Page 129 of 166 56 17.2.4 Where simultaneous operations involving multiple vessels are planned to take place within the same area, marine traffi c control (MTC) under a single designated authority is required. Coordination shall be arranged between the various contractors and vessels deployed in order to avoid unsafe confl ict between vessel movements and moorings. This is particularly important for jack-up positioning operations and to ensure the safety of the jack-up after elevation. 17.2.5 The area in which MTC applies shall be defi ned. All proposed vessel movements within the defi ned area shall be reported to the marine traffi c controller in advance for planning purposes. No movement shall take place within the area until clearance is received from the marine traffi c controller. The MTC shall be advised on completion of each movement. 17.2.6 Jack-ups operating within an area subject to MTC shall be fi tted with the navigation and communication equipment necessary to monitor and transmit communications and to transmit radio identifi cation signals and messages compatible with systems used by the MTC. Page 130 of 166 57 18. Conduct of jack-up operations 18.1 Sources of guidance on the conduct of jack-up operations 18.1.1 The jack-up’s operating manual is the principal source of instruction and guidance on the conduct of jack-up operations. The operation of vessels governed under the ISM code shall be guided by the relevant safety management manuals. The operation of the vessel’s jacking system, cranes and all machinery and equipment should be conducted in accordance with the relevant manufacturer’s manuals. 18.1.2 Specifi c guidance contained in procedure documents should be followed. Proposed departures or deviations (if any) from the instructions and recommendations contained in the manuals referred to in 18.1.1 (above) should follow a management of change (MOC) procedure and should be documented at the planning stage. 18.1.3 The operation should be conducted in such a way that there is no unplanned departure from the guidance provided in the sources listed above except in cases of emergency when the master of the jack-up deems it necessary to take diff erent action or adopt an alternative procedure in order to avoid an unsafe condition or risk thereof. Provision for such emergencies should be identifi ed in the MOC procedure. 18.1.4 In cases where circumstances arise requiring a change to the existing guidance then the operation in progress should be temporarily suspended and the circumstances investigated in accordance with the MOC procedure. Alternative procedures should only be adopted when they have been reviewed, approved and signed off in accordance with the MOC procedure. 18.1.5 The use of jack-up move checklists is recommended. 18.2 Manning for operations 18.2.1 The jack-up shall be manned with a competent marine crew in accordance with the vessel’s Safe Manning Certifi cate (if issued) or in any case with suffi cient crew to manage the vessel and the marine operations making proper allowance for rest periods. 18.2.2 Jack-ups without any propulsion units and issued with loadline or loadline exemption certifi cates for unmanned tow may carry a riding crew suffi cient to manage the vessel and the operations subject to the provision of adequate life saving and fi refi ghting equipment. 18.2.3 Where a riding crew is carried the attending tug(s) shall have suffi cient certifi ed capacity to accommodate the riding crew and suitable provision to safely transfer all personnel from the jack-up to the tug. The maximum weather conditions for transfer of personnel from the jack-up to the attending tug(s) should be established prior to commencing the tow and provision should be in place for the transfer of personnel from the jack-up to the tug well before deteriorating weather conditions approach the level that would render disembarkation unsafe. 18.2.4 For propulsion assisted or non-propelled jack-ups in the transit condition the manning should be reduced as far as is practicable by the removal of non-essential personnel before departure. In any event the total complement shall not exceed 50% of the total survival craft/liferaft capacity for the transit mode. Manning need not be reduced for fi eld moves. 18.2.5 There is no requirement to reduce manning in the transit mode for self-propelled jack-ups classed for unrestricted transit through the certifi ed trading area; however, the total number of persons on board shall not exceed the vessel’s certifi ed lifesaving capacity. Page 131 of 166 58 18.2.6 For all jack-ups operating in the elevated mode the manning level including day visitors shall never exceed the jack-up’s maximum certifi ed capacity except in cases where emergency assistance is being rendered by the jack-up to another vessel in distress. 18.2.7 Well prior to the onset of extreme storm conditions and before placing the jack-up in the storm survival mode, consideration should be given to the available means of evacuation and the timely removal of all non-essential personnel. 18.3 Weather forecasts 18.3.1 The safety of most jack-up operations is dependent upon the regular receipt of reliable weather forecasts. 18.3.2 Excepting UK Met Offi ce forecasts, no reliance shall be placed upon weather information freely available to the public on the internet or information broadcast by commercial radio and television stations of the type that is general in nature and intended only for those engaged in non-critical leisure activities. 18.3.3 Shipping forecasts, inshore forecasts, gale and strong wind warnings and the latest marine observations issued by the UK Met Offi ce shall be monitored on a regular basis. Routine forecasts and warnings broadcast by the UK Met Offi ce may be suffi cient for jack-up operations conducted in harbours or within sheltered bays and estuaries. 18.3.4 For all other jack-up transit, positioning and elevated operations conducted anywhere outside sheltered harbours or outside sheltered bays and estuaries, route-specifi c and site-specifi c marine weather forecasts (as applicable) are required. 18.3.5 Route and site-specifi c forecasts are required at intervals not exceeding 12 hours and these should be broken down into four time periods (00, 06, 12 and 18 hundred hours U.T.) for the following three days plus an outlook for the following two days. Each forecast should contain the following meteorological information: • Wind directions, speed and gusts at 10m • Wind directions, speed and gusts at 50m • Maximum wind wave height and period • Signifi cant wind wave height and period • Swell wave direction height and period • Visibility • Temperature • Barometric pressure per period • Type of weather per half-day • Overall conditions in the form of surface pressure isobar maps • Forecast reliability ranking for each forecast • Contact details for the duty forecaster (to be available on a 24/7 basis) 18.4 Transit 18.4.1 Prior to commencing the transit the person responsible for conducting the operation shall be in possession of the relevant site-specifi c assessment report for the proposed new location and shall be familiar with the information, instructions and recommendations contained in the documents described in section 18.1.1 and 18.1.2 (above). Page 132 of 166 59 18.4.2 A weather forecast indicating suitable conditions for the proposed transit shall be received and reviewed prior to jacking down. On site conditions of wind, wave and current should be carefully observed and assessed to ensure that the prevailing conditions will not adversely aff ect control of the movement of the jack-up on departure from the location. 18.4.3 Before jacking down, the load and stability calculations should be completed and all equipment and cargo secured for transit. The jacking system and all main machinery and equipment should be tested and the person responsible for the conduct of the move should be satisfi ed that the jack-up and the towing vessel(s) (if any) are in all respects ready for the move. 18.4.4 Before jacking down the jack-up’s position, heading and clearances between adjacent structures or obstructions should be carefully checked. Particular attention should be paid to the air gap, the water depth, the predicted rise or fall of the tide and the individual leg penetrations. These levels should be checked against individual leg height readings so as to ensure that the person responsible has a complete understanding of the jack-up’s elevated status before jacking down. 18.4.5 Caution should be exercised when raising the legs to avoid the risk of injury to personnel on deck caused by loose objects and marine growth breaking loose and falling from the legs. 18.4.6 For manned units, routine checks of the watertight integrity and seafastening arrangements should be carried out during transit afl oat. For unmanned units routine inspection of the barge draft and trim can be carried out by the crew of the towing vessel using binoculars. 18.4.7 Jack-ups in transit are required to have an anchor ready for release during transit and positioning; however, to avoid accidental release the anchor should be secured with a quick-release mechanism. 18.4.8 A schedule of regular radio contacts should be maintained between the towing vessel and manned jack-ups under tow. Weather forecasts shall be monitored and weather observations logged. 18.5 Positioning 18.5.1 To ensure that the limits prescribed in the operating manual are not exceeded during positioning, a weather forecast shall be obtained indicating that the prescribed limits will not be exceeded over the time required for positioning plus a contingency for delay. On site conditions of wind, wave and current shall be carefully observed to ensure that the prevailing conditions and any anticipated changes will not adversely aff ect control of the jack-up during the approach and positioning. 18.5.2 Prior to approaching the proposed new location the leg securing system (if fi tted) should be disengaged and the jacking system and all machinery and equipment to be used for the positioning operation such as survey gear and mooring winches should be function tested. 18.5.3 Crane booms shall remain secured for the transit condition and all equipment and cargo seafastenings shall be kept in place until the positioning operation is complete. The towing vessel shall remain connected to the main towing bridle until the positioning operation is complete. 18.5.4 The jacking, preloading and elevating operations shall be undertaken in accordance with the instructions and recommendations contained in the operating manual and the jacking system manual (if not included in the operating manual). Limits specifi ed in the manuals shall not be exceeded and all precautions described in the manuals shall be observed. Page 133 of 166 60 18.5.5 The jack-up’s overall elevating speed, inclusive of time taken to recycle jacks, shall be suffi cient to manage the planned positioning and removal operations, having due regard for the tidal range and the rate of tidal rise or fall. Special consideration for operations at locations with large tidal ranges and locations where the duration of slack water may limit the time available for changing from the fl oating to the elevated mode may be required. 18.5.6 Preloading shall be carried out to ensure that each leg is subjected to the load specifi ed in the operating manual or in the site-specifi c assessment. The preloading operation should be carried out with the hull levelled at the lowest practicable air gap. 18.5.7 In circumstances where risk of rapid leg settlement exists during preloading the level of the hull should be set, as far as practicable, at zero airgap or with the hull partially buoyant before achieving footing loads that are likely to result in rapid settlement. Operations of this type require careful planning; the rise and fall of the tide must be taken into account and the operation can only be conducted in calm weather. 18.5.8 Complex preloading or predriving operations involving leg jetting or other special measures designed to achieve the safe installation of a jack-up at locations where risk of punch-through or other foundation hazards exist should not be attempted without expert geotechnical advice. 18.5.9 Particular attention shall be paid to accurate measurement of actual leg penetrations and associated footing loads during installation so as to monitor progress against the predicted load/penetration curve. Any signifi cant diff erence between the predicted leg penetrations and the actual progress of the penetration during preloading should be investigated and reported to a competent person for review and approval prior to elevating the jack-up to the working air gap. 18.5.10 Following the preloading operation and before elevating the jack-up to a working air gap, the individual leg height readings and leg footing penetrations shall be accurately recorded (Appendix H). Leg height and penetration measurements obtained from mechanical or electronic instruments should be verifi ed by visual inspection of the leg height marks against a reference point at the level of the deck or jack-house. 18.5.11 Following completion of the preloading any signifi cant diff erence between the penetrations of each leg and/or any signifi cant diff erence between the penetration anticipated and the penetration achieved should be investigated and reported to the competent person responsible for the site-specifi c assessment for review and approval prior to elevating the jack-up to the working air gap. 18.6 Deployment of jack-ups for soil investigations 18.6.1 In virgin territory, where there has been no previously recorded jack-up activity and where there is no adequate advance information on the nature of the seabed soils, the ground investigation may be carried out using equipment deployed from a jack-up operating in weather restricted mode. 18.6.2 Compliance with the recommendations contained in this section 18.6 does not relieve the jack-up operator of his responsibility for obtaining, as far as reasonably practicable, any available information on the probable characteristics of the soils likely to be encountered before the jack-up is deployed. Particular reference is requested to the HSE information sheet - jack-up (self elevating) installations: review and location approval using desktop risk assessments in lieu of undertaking site soils borings. Page 134 of 166 61 18.6.3 In the absence of reliable advance soil data the jack-up operator must exercise extreme caution during preloading or predriving and the jack-up should remain with the hull partly buoyant or elevated to the lowest practical air gap so that it can be refl oated quickly should the investigation and analysis reveal that the foundation is unsuitable or if rapid settlement occurs. 18.6.4 A jack-up should not be elevated above the lowest practical working air gap or to the survival air gap on any location until the soil investigation and the geotechnical assessment has progressed to the point where the level of confi dence in the integrity of the jack-up foundation has been formally declared satisfactory by a Competent Person. It should be recognised that on-site soil investigation alone may prove inadequate and that the results of on-shore laboratory analysis of samples may be needed before this level of confi dence is achieved. 18.6.5 The lack of adequate advance soil data means that the risk of encountering unsuitable foundation conditions cannot be reduced to a level that is as low as reasonably practicable until the soils investigation and analysis is complete. Therefore soils investigations undertaken from permanently manned jack-ups should only be attempted with towing vessel(s) in attendance and in periods of benign weather that will allow the jack-up to be refl oated and moved to shelter or an alternative safe elevated location at any time. 18.6.6 For unmanned jack-ups, where the crew are routinely accommodated on shore between shifts, the requirement to remove the jack-up before conditions for jacking and refl oating are exceeded can be waived if the following conditions are complied with: • It has been established by a competent person through review of the desk top study and/or the progress of the soils investigation that the risk of encountering unsuitable foundation conditions is low. • A repeated preload operation has exposed no problems and leg penetrations are approximately even. • The jack-up is capable of withstanding the 10 year storm (foundation bearing capacity assumed to be adequate) and the hull is raised to comply with the 50 year air gap requirement. • Site-specifi c weather forecasts stating a high level of confi dence are being monitored and all personnel are removed from the jack-up prior to the onset of weather conditions predicted to exceed the limit for safe disembarkation. • There is no risk to personnel and the consequences of catastrophic weather damage to the jack-up and the potential threat to the environment and to shipping, installations, and property in the vicinity have been formally assessed by the site developer and the jack-up owner. 18.7 Elevated operations 18.7.1 Elevated operations shall not begin until preloading has been completed and the unit has been elevated to the working air gap in accordance with the provisions of section 18.5 of this guideline. 18.7.2 Receipt and review of weather forecasts (section 18.3) shall be continued throughout the period elevated on location. 18.7.3 The progress of elevated operations shall be closely monitored to ensure that weather conditions do not exceed the prescribed limits and to ensure that there is adequate time remaining to implement contingency plans for removal of the jack-up or for placing the unit in the elevated survival mode before the onset of adverse weather, as applicable. 18.7.4 The elevated load condition shall be calculated and any changes in weight attributable to material loaded, discharged or consumed shall be recorded in such a manner that the individual leg loads for all stages of the elevated operation are known. Page 135 of 166 62 18.7.5 Hull inclination shall be monitored on a frequent and regular basis. For units elevated by means of hydraulic jacks, the jack pressures shall be monitored on a frequent and regular basis. In the event that any inclination or loss of jack pressure is observed the elevated operations should be suspended until the cause of the inclination or loss of pressure has been investigated and the condition has been rectifi ed. 18.7.6 Consideration shall be given to the potential impact of seabed scour on the integrity of the jack-up foundation over time. Particular consideration shall be given to the potential for movement of seabed soils caused by currents or waves. Where risk of such conditions is deemed to exist, the jack-up foundation analysis shall include an assessment of the level of change that may aff ect foundation stability. The integrity of the foundation is to be tested by repeating the preload operation following a storm or other event that may have adversely aff ected the strength of the soil supporting the jack-up. 18.7.7 At locations where potential for seabed scour exists, an increase in leg penetration, inclination and/or loss of hydraulic jack pressure (for units elevated by means of hydraulic jacks) may occur. Scour eff ect may create a requirement for frequent operation of the jacking system as adjustments to leg heights become necessary to maintain elevated stability. In such cases a suitable ‘bedding-in’ period must be allowed for and elevated operations should not be attempted until the leg penetration has reached a depth at which the rate of additional penetration caused by scour has reduced to a manageable level. 18.7.8 If any unexpected increase in leg penetration or inclination occurs during elevated operations then all operations should be suspended immediately and expert geotechnical advice should be obtained. Jacking of the unit should only be undertaken after consultation with experts. Subject to the provision of expert advice the hull may be lowered to the lowest practical air gap until the cause of the settlement has been investigated and rectifi ed. After the jack-up has been stabilised the preload operation must be repeated. 18.7.9 Seafastenings for cargo (particularly modules subject to high wind loads) should not be removed until lift rigging is connected and lifting operations are ready to proceed. 18.7.10 Prior to heavy lift operations, the elevated load condition of the unit should be checked by calculation and, for units elevated by means of hydraulic jacks, by equalising the jack pressures. In all cases it shall be verifi ed that the heavy lift operation will not cause allowable leg loads or the centre of gravity off set limits to be exceeded at any point during the proposed lift. Page 136 of 166 63 19. Emergencies and contingencies 19.1 Life saving appliances, fi refi ghting appliances and radio installations 19.1.1 Jack-ups shall be fi tted with life saving and fi refi ghting appliances and radio installations in accordance with their registry, class and certifi cation. Typically, the following standards will be applied as appropriate. • IMO MODU code for the construction and equipment of mobile off shore drilling units, consolidated edition, 2001 • IMO Safety of Life at Sea (SOLAS, 1974) • MCA Small Commercial Vessel and Pilot Boat (SCV) Code (see MGN 280) 19.1.2 Whether required by statutory regulation or otherwise, permanently manned jack-ups fi tted with certifi ed crew accommodation including modular accommodation that is occupied by project personnel or visitors shall, as far as practicable, be fi tted with survival craft and means of evacuation and escape complying with the IMO MODU code, chapter 10. 19.1.3 In the case of a jack-up where, due to its size or confi guration, lifeboats and launching arrangements cannot be fi tted, liferafts complying with the requirements of IMO SOLAS 74 regulation III/39 or III/40 served by launching devices complying with the requirements of regulation III/48.5 or III/48.6 shall be fi tted and these shall be of such aggregate capacity as will accommodate the total number of persons on board if: • All of the liferafts in any one location are lost or rendered unusable • All of the liferafts on any one side, any one end, or any one corner of the unit are lost or rendered unusable 19.1.4 If two widely separated fi xed steel ladders extending from the deck to the waterline when the unit is elevated cannot be installed then alternative means of escape with suffi cient capacity to permit all persons on board to descend safely to the waterline shall be provided. 19.2 Emergency procedures, training and drills Whether required by statutory regulation or otherwise, all jack-ups fi tted with permanent crew accommodation and/or modular accommodation that is occupied by project personnel or visitors shall comply with the provisions contained in the IMO MODU code with respect to the following. Chapters and section numbers refer to numbering in the MODU code. • Emergency Procedures (chapter 14, section 14.8) • Emergency Instructions (chapter 14, section 14.9) • Training Manuals (chapter 14, section 14.10) • Practice Musters and Drills (chapter 14, section 14.11) • Onboard training and instructions (chapter 14, section 14.12) • Records (chapter 14, section 14.13) 19.3 Site-specifi c emergency response plan 19.3.1 Site-specifi c emergency response plans shall be developed for jack-ups operating on site. Emergency response plans are likely to involve local emergency services such as the coastguard, RNLI, fi re, police, ambulance, harbour master and local towage, salvage and pollution response services. Contact should be made with these services to co-ordinate plans prior to mobilising the jack-up. Following mobilisation, joint exercises should be conducted if practicable. 19.3.2 Guidance can be found in the MCA MGN 371 ‘Off shore Renewable Energy Installations (OREIs) Guidance on UK Navigational Practice, Safety and Emergency Response Issues’ and the supporting note ‘Off shore Renewable Energy Installations Emergency Response Cooperation Plans (ERCoP) for SAR Helicopter Operations’. 19.3.3 Plans should be based on comprehensive risk assessments and should be developed following consultation with local emergency services to cover all foreseeable emergency situations including, but not limited to: Page 137 of 166 64 • Extreme storms • Evacuation and escape • Medical aid and evacuation of individuals • Man overboard • External response to jack-up vessel emergencies (Common perils such as fi re, collision, fl ooding, breaking adrift, settlement etc.) • External response to pollution (In addition to the jack-up’s SOPEP) • Notifi cations, contact details and incident reporting 19.4 Route and site-specifi c contingency plans for transit and positioning Contingency plans specifi c to the proposed transit and positioning operations shall be contained in the procedure document and should include: • Forecast of or unexpected onset of adverse weather ≥ prescribed criteria • Motions afl oat approaching prescribed limits • Failure of or damage to seafastenings and grillage • Deviation to designated safe havens en route • Tug breakdown • Towing equipment failure • Jacking system machinery and/or power failure • Mooring equipment failure • Survey equipment failure • Unexpected installation behaviour (leg penetration not as anticipated) • Pollution response (for units not provided with a SOPEP) • Communications equipment failure • Notifi cations, contact details and incident reporting 19.5 Site-specifi c contingency plans for elevated operations Contingency plans specifi c to the proposed elevated operations shall be contained in the Procedure Documents and should include: • Forecast or unexpected onset of adverse weather ≥ prescribed criteria • Jacking system failure • Main power failure • Settlement of leg footings and/or leg misalignment and binding • Removal of the jack-up to a safe haven • Crane structural or machinery failure with lift suspended • Notifi cations, contact details and incident reporting 19.6 Ship emergency response 19.6.1 Under the provisions of the ISM code, self-propelled jack-ups (as ships) are required to have in place a ship emergency response service contactable on a 24/7 basis through the designated person ashore (DPA). This service may be provided by a company’s competent person (naval architect or specialist) or by an external company. The service is intended to provide the vessel’s master with a swift and eff ective response in the form of practical advice, support and back-up technical services in the event of unexpected incidents such as grounding, collision, fl ooding or explosion. Consideration should be given to the provision of a similar response service for all jack-up operations whether required by statutory regulation or otherwise. Page 138 of 166 65 APPENDIX A References PLEASE CHECK FOR AMENDMENTS, REVISIONS AND LATEST EDITIONS. BWEA BWEA Guidelines for Health and Safety in the Marine Energy Industry, October 2008 Background Information on Jack-Ups Noble Denton Consultants Ltd. The Marine Operations of Self-Elevating Platforms (Jack-up Rigs) (Copyright - Noble Denton: Course off ered by Aberdeen College of Further Education) Oilfi eld Publications Ltd. Oilfi eld Seamanship Series, volume two – Jack-up Moving Bennet & Associates & Off shore Technology Development Inc. Jack-Up Units. A Technical Primer for the Off shore Industry Professional UK Government The Health and Safety at Work Act 1974 The Management of Health and Safety at Work Regulations 1999 The Construction (Design and management) Regulations 2007 (CDM) Provision and Use of Work Equipment Regulations 1998 Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) - HSE - Technical guidance on the safe use of lifting equipment off shore - HSE - Safe use of lifting equipment – Approved Code of Practice and Guidance HSE Information Sheets Jack-up (self elevating) installations: rack phase diff erence http://www.hse.gov.uk/off shore/infosheets/is4-2007.pdf Jack-up (self elevating) installations: fl oating damage stability survivability http://www.hse.gov.uk/off shore/infosheets/is6-2007.pdf Jack-up (self elevating) installations: review and location approval using desk-top risk assessments in lieu of undertaking site soils borings http://www.hse.gov.uk/off shore/infosheets/is3-2008.pdf HSE Information The safe approach, set-up and departure of jack-up rigs to fi xed installations http://www.hse.gov.uk/foi/internalops/hid/spc/spctosd21.htm Guidance on Procedures for the Transfer of Personnel by Carriers. HSE Research Reports - OTO series SNAME 5-5B WSD 0: Comparison with SNAME 5-5A LRFD and the SNAME 5-5A North Sea Annex http://www.hse.gov.uk/research/otopdf/2001/oto01001.pdf Page 139 of 166 66 Self-elevating installations (jack-up units) http://www.hse.gov.uk/research/otohtm/2001/oto01051.htm Stability of jack-ups in transit http://www.hse.gov.uk/research/otopdf/1995/oto95022.pdf HSE RR series Review of the jack-ups: Safety in transit (JSIT) technical working group http://www.hse.gov.uk/research/rrhtm/rr049.htm Guidelines for jack-up rigs with particular reference to foundation stability http://www.hse.gov.uk/research/rrhtm/rr289.htm International Maritime Organisation MODU Code. Code for the construction and equipment of mobile off shore drilling units, consolidated edition, 2001 International Safety Management (ISM) Code 2002 Safety of Life at Sea (SOLAS 1974) International Convention on Loadlines 1966 Preventing Collisions at Sea Regulations COLREGS Standards of Training, Certifi cation and Watchkeeping for Seafarers (STCW) 1978 Prevention of Pollution from Ships MARPOL 1973/78 Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 Incidents by Hazardous and Noxious Substances, 2000 (HNS Protocol) Control of Harmful Anti-fouling Systems on Ships (AFS), 2001 IMO MSC Circ.645, “Guidelines for Vessels with Dynamic Positioning Systems” IMO MSC Circ.738 “Guidelines for Dynamic Positioning System (DP) Operator Training”. Marine and Coastguard Agency MCA Code of Safe Working Practice for Merchant Seaman MCA Small Commercial Vessel and Pilot Boat (SCV) Code (as currently set out in MGN 280) MCA - MGN 371 ‘Off shore Renewable Energy Installations (OREIs) Guidance on UK Navigational Practice, Safety and Emergency Response Issues’ and the supporting note: MCA - ‘Off shore Renewable Energy Installations Emergency Response Cooperation Plans (ERCoP) for SAR Helicopter Operations’. Society of Naval Architects and Marine Engineers Society of Naval Architects and Marine Engineers (SNAME) Technical and Research Bulletin TR5-5A Guidelines for Site Specifi c Assessment of Mobile Jack-up Units Including the Recommended Practice and Commentary International Organisation for Standardisation ISO 19901-1:2005(E) Part 1: MetOcean design and Operating considerations. Page 140 of 166 67 Noble Denton Seabed and Sub-seabed Data for Approvals of Mobile Off shore Units/Mou 0016: 0016/ND Rev 4 - 16 Dec 2008 Self-Elevating Platforms - Guidelines for Elevated Operations 0009: 0009/ND Rev 4 - 16 Dec 2008 Guidelines for Marine Transportations 0030/ND Rev 3 - 15 April 2009 Guidelines for the Approval Of Towing Vessels 0021/ND Rev 7 - 17 Nov 2008 Guidelines for Marine Lifting Operations 0027/ND Rev 7 - 15 April 2009. A further update (to correct a typo) is imminent. London Off shore Consultants LOC Guidelines for Marine Operations – Barge Transportation LOCG-GEN-Guideline 002 Rev. 01 Dated 01/01/2007 LOC Guidelines for Marine Operations – Marine Lifting LOCG-GEN-Guideline 003 Rev. 0 Dated 05/2003 Det Norske Veritas Det Norske Veritas (DNV) Rules for the Planning and Execution of Marine Operations: • Load Transfer Operations (issued 1996) • Towing (issued 1996) • Special Sea Transports (issued 1996) • Off shore Installation (issued 1996) • Lifting (issued 1996) • Sub Sea Operations (issued 1996) • Transit and Positioning of Mobile Off shore Units (issued 2000) Det Norske Veritas (DNV) Classifi cation Notes Section 8: Foundation of Jack-up Platforms Lloyds Register Code for Lifting Appliances in a Marine Environment 2008 UK Off shore Operators Association Guidelines for Safe Movement of Self-Elevating Off shore Installations (Jack-ups) UK Off shore Operators Association. April 1995 issue No.1 North Sea Lifting (NSL) Suitability of Cranes for Man Riding Page 141 of 166 68 Air gap Vertical distance between the bottom of the rig hull and the water surface. Air gap related to LAT Vertical distance between the bottom of the hull and the level of LAT. Centroid of the legs Point on a three-legged jack-up that is horizontally equidistant from each leg centre. Certifi ed accommodation Permanent or temporary certifi ed crew accommodation comprising sleeping cabins with sanitary facilities, galley, mess room and recreation spaces intended for occupation by the crew and project workers. This specifi cally excludes temporary or permanent containerised or modular units installed on the jack-up to provide limited shelter, feeding and sanitary facilities for personnel that are not routinely accommodated on board. Chart datum The datum to which the soundings (water depths) are reduced on the location bathymetric chart and to which must be added the tidal height to obtain the actual depth of water at any point in time. Class notation Series of symbols, letters and numbers assigned by the classifi cation society to indicate the details of the class assigned to the vessel (For example: “ABS Self Elevating ✠A1”, Lloyds ✠100A1 etc.). Competent person A person having suitable and suffi cient experience in the fi elds that they work in, to understand the hazards and risks involved with the work, the operating environment, and the type of people they need to work with; and having suffi cient training to be able to communicate the results of their assessment to all the people necessary (in writing if necessary) in a clear and comprehensible manner. The Management of Health and Safety at Work Regulations 1999, requires every employer to appoint one or more competent persons to assist with putting measures in place to ensure legal compliance. The competent person can be either an individual or a company providing these services. The person is regarded as competent if they have suffi cient training and experience or knowledge and other qualities to properly assist the employer to meet his safety obligations. A competent person is likely to be a corporate body rather than an individual because of the necessary requirement to have access to a wide variety of technical expertise and specialist services. One indication of competence is accreditation and certifi cation. Contingency plan: Pre-considered response to a deviation from an intended course of action. Dynamic amplifi cation factor The factor by which the ‘gross weight’ is multiplied, to account for accelerations and impacts during the lifting operation. APPENDIX B Glossary, terms and defi nitions Page 142 of 166 69 Elevated operation Jack-up marine operation conducted after the unit has been jacked, preloaded and elevated to a working air gap. Extreme wave crest elevation The maximum elevation of the storm wave crest above LAT for the return period specifi ed. Field move A jack-up move undertaken in the vicinity of a work site which can be completed within the period covered by a single reliable weather forecast (commonly 12 – 24 hours). Flag state Nation operating a registry of vessels in which the jack-up has a valid listing. Freeboard The vertical height of the assigned deck line above the vessel’s waterline. Gog line (or rope) System used for the control of the towline to reduce the risk of girding. Commonly a line led from a winch drum or fi xed connection through a deck fi tting aft of the towing winch and connected to the towing wire so as to control the point at which any transverse load imposed by the towline angle acts upon the towing vessel. Grillage: The temporary structural members that support the module and distribute the vertical static and dynamic loads over the barge or vessel framing. Gross Weight The calculated or weighed weight of the structure to be lifted including a reserve factor. Harbour Move Jack-up move conducted within port limits. Hook Load The hook load is the ‘lift weight’ plus the ‘rigging weight including dynamic factor’. Jack Frame Jack-up vessel structure at each leg containing the jacking system (also called the “jack house”). Jacking Operation of the jacking system Jacking down Lowering the rig hull when in the elevated mode Jacking up Elevating the rig hull when in the elevated mode Jacking legs down Jacking the rig hull up Jacking hull down Jacking the legs up. Raising legs Jacking legs up when in the fl oating mode Lowering legs Jacking legs down when in the fl oating mode Jack-up Ship or barge fi tted with legs and jacking machinery providing the capability to self-elevate the vessel above the sea surface. Leg bind or leg binding Excessive friction between the leg chords and leg guide usually caused by the rig being out of level and/or by the legs being bent or inclined. Leg braces Horizontal or diagonal tubular members of the leg structure connecting the leg chords. Page 143 of 166 70 Leg chords Vertical tubular members of the leg structure of braced type legs. Leg footing penetration curve Graphic representation based on geotechnical analysis showing the predicted leg footing load versus the depth of leg penetration. Leg footing reaction Equal to the portion of the jack-up’s elevated weight including environmental loads imposed on any one leg plus the leg and footing weight minus the leg buoyancy. Leg load Portion of the jack-up’s elevated weight including environmental loads supported by a particular leg. Location move Jack-up move not falling into the defi nition of an ocean tow or a fi eld move and generally undertaken with the unit in fi eld move confi guration as a weather restricted operation within the period of a reliable weather forecast. Location approval Certifi cate and report providing location details and certifying warranty approval for installation of a rig on a specifi c location. Location move A move between two locations which cannot be completed within the period covered by a single forecast but which can safely be undertaken with the unit in fi eld move confi guration, having due regard for the availability of standby locations or shelter points en route. Marine warranty surveyor Marine surveyor assigned to review procedures and to attend marine operations commonly to satisfy an insurance warranty clause that states that the operation shall be approved by and conducted in accordance with the recommendations issued by a named warranty surveyor. Medivac Evacuation of a sick or injured person. Met-ocean study Meteorological study of a specifi c area carried out to determine the probable range of environmental conditions for specifi c return periods. Minimum breaking load The minimum allowable value of ‘breaking load’ for a particular lifting operation. Mobile off shore unit For the purposes of this document, the term includes non-drilling mobile jack-up vessels such as accommodation, construction, and lifting barges. MODU code Code for the construction and equipment of mobile off shore drilling units, consolidated edition 2001. Module A unit of cargo such as a jacket, integrated deck, topside components, pre-assembled units, items of equipment or parts thereof. Net weight The calculated or weighed weight of a structure, with no contingency or weighing allowance. Page 144 of 166 71 Nomograms Graphic representation indicating the jack-up’s capacity to withstand defi ned environmental conditions in a range of water depths and with a range of leg penetrations. Permanently manned jack-up Jack-up permanently manned by the crew (and project workers if applicable) where some or all personnel, both on-shift and off -shift, are accommodated on board and are not routinely transported to and from the shore at each shift change. Positioning ( jack-up) Jack-up marine operation commencing from the time of arrival at a new location and continuing until the unit has completed jacking, preloading and elevating to the working air gap on a new elevated location or until the unit is safely moored afl oat at a new location. Preloading Preloading is the process by which the jack-up rig’s legs are loaded so as to drive them into the seabed soil. The preloading process simulates the expected maximum loads that may be imposed on the seabed and thus the strength of the seabed soil foundation is proof tested in excess of the capacity required to support the rig when it is working or when it is idle in the storm survival mode. The object of preloading is to achieve suffi cient capacity to withstand the combination of vertical and horizontal reactions, the applied preload (generally) has to be greater than the storm vertical reaction. When using SNAME, as required in this document, the vertical and horizontal reactions include the eff ects of the partial load factor and the permitted capacity is reduced by the application of the SNAME resistance factor. Punch-through Punch-through is a generic term often loosely applied to an event whenever signifi cant vertical footing settlement is observed over a relatively short period of time. During these events diff erential footing penetrations usually occur which may dramatically aff ect the stability of the jack-up. Punch-through can result in structural failure and even total loss. Rack chocks Leg fi xation device engaged to form a strong connection between the rig hull and legs for units fi tted with rack and pinion jacking systems Rack phase diff erence Diff erence in vertical height between individual chords on one leg on units with braced type leg structures Recognised classifi cation A Vessel classifi cation society with established rules and procedures for the classifi cation, survey and certifi cation of vessels used in off shore construction activities Recognised maritime nation A nation with maritime laws that maintains a registry of ships and that has adopted the IMO conventions listed in section 2.6. Recommended practice SNAME TR5-5A: the Recommended Practice for Site-Specifi c Assessment of Mobile Jack-up Units Rev, 2 January 2002. Refl ected waves Wind or swell generated waves that have been refl ected through direct impact with obstructions such as cliff s or breakwaters society (RCS) Page 145 of 166 72 Refracted waves Wind or swell generated waves that have been infl uenced in direction by the geophysical characteristics of the coastline or seabed Riding crew Marine crew assigned to an unmanned barge during a tow Rig mover Person appointed to be in charge of the planning and execution of the jack-up move Seafastenings: Shall in general mean the temporary structures or tie-downs that secure the Module for transportation and berthing forces. Settlement The settlement of jack-up leg footings into the seabed soil Slow settlement: Leg settlement where the rate at which one or more legs is penetrating is less than the rate at which the hull can be maintained in a level condition by lowering the hull on the other legs. Rapid settlement: Rapid uncontrolled leg settlement where the rate at which one or more leg is penetrating exceeds the rate at which the hull can be maintained in a level condition by lowering the hull on the other legs. Slight settlement: Leg settlement where the resulting inclination is less than one degree. Signifi cant settlement: Leg settlement where the resulting inclination is more than one degree. Signifi cant wave height H = the average of the highest one-third of all waves. Site-specifi c assessment Assessment of the site soil foundation and the structural capacity of a jack-up to withstand the loads associated with the geophysical and extreme environmental conditions for a specifi c location. Spudcan Very robust tank-like structure attached to the bottom of a jack-up rig’s leg and forming the leg footing. Squat Temporary increase in vessel’s hull draft caused by change of trim when proceeding in shallow water above a certain speed. Survival mode Elevated condition achieved by the jack-up when it is capable of remaining on location in extreme storm conditions with all stresses remaining within allowable limits in accordance with the RP. Tidal window Period during a tidal cycle where the tidal height provides adequate depth of water and/or current velocity not exceeding a prescribed value for a particular operation. Tow master Person usually holding a Marine Certifi cate of Competency assigned to control the towage, navigation and positioning of the Rig afl oat Page 146 of 166 73 Transit ( jack-up) Jack-up marine operation commencing from the moment when lowering of the hull commences on departure from an elevated location or when the last mooring line is recovered on departure from a location afl oat and continuing until arrival in the vicinity of a new location. Tug management system DGPS navigation survey system and telemetry that allows the positions of tugs, anchors and mooring lines to be displayed in real time on remote monitors. Unaccounted weight Portion of the vessel’s total weight that has not been accounted for in the load calculations. The amount is calculated by subtracting the calculated displacement from the actual displacement obtained by reading the hull draft marks with the rig afl oat. Unmanned jack-up A non-propelled jack-up barge that carries no permanent crew accommodated on board and is not fi tted with certifi ed accommodation and where the crew and project workers are routinely transported to and from the shore at the end of each shift. Unrestricted mode A jack-up engaged on an unrestricted operation. Unrestricted operation A marine operation which cannot be completed within the limits of a favourable weather forecast (generally less than 72 hours). The design weather conditions must refl ect the statistical extremes for the area and season. Variable load Portion of the vessel’s elevated weight that is variable, that is, not forming part of the fi xed structure and machinery. This includes fuel, lubricants, fresh water, ballast, drilling materials and equipment, crew and stores. Visitors Personnel on board the unit who do not form a part of the vessel’s crew. Weather restricted operation A marine operation which can be completed within the limits of a favourable weather forecast (generally less than 72 hours), taking contingencies into account. The design weather conditions need not refl ect the statistical extremes for the area and season. A suitable factor should be applied between the design weather conditions and the operational weather limits. Weather window Forecast period of generally benign weather with wind and waves not exceeding prescribed the limits for a particular operation. Page 147 of 166 74 ABREVIATIONS AISC American Institute of Structural Steel ALARP As low as reasonably practicable (with reference to risk reduction) BL Breaking load BP Bollard pull CCTV Closed Circuit Television CDM (Regulations) Construction Design and Management regulations CPT Cone penetrometer test DAF Dynamic Amplifi cation Factor applied to lifted weights to account for the dynamic motion of vessels in marine lifting operations DGPS Diff erential Global Positioning System DP Dynamic positioning ECDIS Electronic Chart Display and Information System EEZ Exclusive economic zone GMDSS Global Maritime Distress and Safety System HAT Highest astronomical tide Hs Signifi cant wave height IACS International Association of Class Societies IAPP International Air Pollution Prevention IMO International Maritime Organisation IOPP International Oil Pollution Prevention ISM International Safety Management (ISM Code) ISPS International Ship and Port Security L.A.T. Lowest astronomical tide LRFD Load resistance factor design MCA Marine and Coastguard Agency (UK) MDW Module design weight MIN Marine information notices MSN Merchant shipping notices MGN Marine guidance notices MOC Management of change MODU Mobile off shore drilling unit MOU Mobile off shore unit MSL Mean sea level MTC Site-specifi c (non-governmental) marine traffi c control OIM Off shore installation manager. The person in charge of the jack-up Page 148 of 166 75 PPE Personal protective equipment PUWER Provision and use of Work Equipment Regulations 1998 RCS Recognised classifi cation society RNLI Royal National Lifeboat Institution RW Rigging weight for lifting operations SCV Small Commercial Vessel Code (Awaiting publication) SF Shear force SHL Static hook load SOPEP Shipboard oil pollution emergency plan STCW 95 Standards of Training and Certifi cation of Watchkeepers 1995 SWBM Still water bending moment TPR Towline pull required WGS 84 World Geophysical Survey 1984 WLL Working load limit (Same as SWL: safe working load) Page 149 of 166 76 APPENDIX C Certifi cates, Manuals, Publications, Logs and Records Ref. Registry Flag state inspection report or MCA inspection ISM Certifi cate and document of compliance Minimum Safe Manning Certifi cate Builders Certifi cate International Tonnage Certifi cate International Loadline Certifi cate (or exemption) Annual Loadline Survey Report/Endorsement Certifi cate of Class (+Annual endorsement) Safety Construction Certifi cate MOU Certifi cate or Safety Equipment Certifi cate or: Safety Equipment – Class Statement of Facts IOPP Certifi cate IAPP Certifi cate ISPS Certifi cate Safety Radio Certifi cate Radio License (GMDSS) Radio Certifi cate of Shore Based Maintenance Fast Rescue Craft Certifi cate Lifeboats (Rigid Survival Craft) Certifi cates Lifeboats davits and launching gear Certifi cates Infl atable Liferaft Service Certifi cates Liferaft Launching Davit Certifi cates (if fi tted) Fixed Firefi ghting Appliances Certifi cate Portable Firefi ghting Appliances Certifi cate Crane Test Certifi cate Lifting Appliances Register - Annual inspection & Quadrennial Test Sewage Plant Certifi cate Garbage Management Certifi cate Medical Drugs Certifi ed Inventory Deratisation or Deratisation exemption Cert. ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✗ ✓ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✗ ✗ ✗ ✓ ✓ ✗ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ Certifi cate CERTIFICATES REQUIRED Self-prop. jack-up ships Permanently manned and/or classed jack-ups Unmanned jack-ups with no classifi cation Page 150 of 166 77 Emergency station bills posted Safety equipment Plans posted Safety equipment signs posted Evacuation and escape route signs posted Emergency muster points marked Survival craft launching instructions posted Lifejacket donning instructions posted Health, safety & environmental policy Drug and alcohol policy Record of emergency drills Safety manual PPE signs posted Accident/incident reports Near miss reports Hazard identifi cation/observation reports Risk assessments conducted/recorded Safety meetings conducted/recorded Tool box talks conducted/recorded Permits to work posted Visitors safety briefi ng record Tag card system Ship security plan Gangway crew/visitors log Medical log Plans, manuals and reports Operating company QA system Company instructions/procedures Ship safety management system manuals Non-conformance & corrective action Vessel operating manual General arrangement plan / capacity plan Crew training manuals / records Approved stability book Stability plan for current voyage/operation SOPEP manual Garbage management plan Engine room & machinery Engine log Bunker check lists Oil Record Book / waste oil disposal Machinery operation & maint. manuals IMO SOLAS (1986 consolidated) IMO load line regulations (1986/81) IMO MERSAR manual IMO ship routeing IMO standard marine navigation vocabulary IMO Collision Regulations (1990) IMO bridge procedures guide IMO Annex I: to MARPOL 73/78 (Oil) IMO Annex II: to MARPOL 73/78 (Noxious Subst.) IMO Annex III: Pollution by Harmful Substances IMO Annex IV: Pollution by Sewage from Ships IMO Annex V to MARPOL 73/78 (Garbage) IMO IMDG code (consolidated supplement) IMO ISPS code MCA Code of Safe Working Practice Bridge / Navigation Publications Navigation charts Chart correction log Pilot books & supplements Guide to port entry List of lights Admiralty list of radio signals (volumes 1 - 6) International Code of Signals (1987) Notices to mariners Flag state marine notices and guidance notes Tide tables Tidal current tables/charts Nautical almanac Navigation tables RPM/Speed data Manoeuvring data Deck log book Rough log Radio log Night order book Passage plans Master/pilot exchange form Vessel check lists [arrival, departure] Operations check lists (jacking) Operations check lists (DP – if DP vessel) Equipment operation and maintenance manuals Complete set of drawings Safety and security A = Self-propelled jack-up ships B = Permanently manned and/or classed jack-up barges C = Unmanned and non-classed jack-up barges A ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✓ ✗ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✓ ✗ ✓ ✓ ✗ ✗ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✓ ✓ B C IMO and other Publications A B C Page 151 of 166 78 Operating manuals containing guidance for the safe operation of the unit should be provided on board and be readily available to all concerned. The manual should, in addition to providing the necessary general information about the unit, contain guidance on and the procedures for the operations that are vital to the safety of personnel and the unit. The manual should be concise and be compiled in such a manner that it is easily understood. The manual should be provided with a contents list, an index and wherever possible be cross-referenced to additional detailed information in the form of drawings, manufacturer’s manuals and other readily available information for the safe and effi cient operation of the unit. Detailed information contained in manufacturer’s manuals (such as the Jacking System Manual) need not be repeated in the operating manual. The operating manual should include the following information. 1. Description, particulars and principal dimensions. 2. Organisation and responsibilities. 3. General arrangement plan and capacity plan showing the location and centres of gravity of all tanks and stowage spaces. 4. Plan showing the location of watertight and weather tight boundaries, the location and type of all watertight and weather tight closures, and the location of down fl ooding points. 5. Limiting design data for the fl oating mode and the elevated mode. 6. Operational limits and procedures and guidance for the transition between the fl oating mode and the elevated operating mode and between the operating mode and the elevated survival mode. 7. Information and guidance on the preparation of the unit to avoid structural damage afl oat and during the setting or retraction of the legs on or from the seabed. 8. Information and guidance on jacking and preloading. 9. Information and guidance on the preparation of the unit to withstand the extreme environmental limits associated with the limiting design data for the elevated mode described in (5) above. 10. Lightship data together with a list of inclusions and exclusions of semi-permanent equipment and guidance for the recording of light weight changes together with weight data and centre of gravity off set limits including: Lightweight Weight of movable items (cranes, pile gates/grippers etc) Weight of legs and leg footings Maximum allowable variable load afl oat, jacking, preloading, operating and survival Maximum allowable displacement afl oat APPENDIX D Jack-up operating manual (recommended contents) Page 152 of 166 79 Maximum allowable elevated weight and maximum leg load for jacking Maximum allowable elevated weight and centre of gravity limits for preloading Maximum allowable elevated weight and centre of gravity limits for elevated operations Maximum allowable elevated weight and centre of gravity limits for survival 11. Tank sounding tables showing capacities, vertical, longitudinal and transverse centres of gravity in graduated intervals and free surface data for each tank. 12. Stability information including hull hydrostatic properties and GZ curves. 13. Allowable vertical centre of gravity curve. 14. Sample stability and trim calculations and guidance for maintaining stability afl oat. 15. Sample elevated load calculations and guidance for maintaining leg loads within design limits including leg load limits and/ or centre of gravity limits for lifting operations. 16. Acceptable structural deck loads. 17. A plan and description of the towing arrangements for non-propelled vessels together with guidance on safe towing operations. 18. A description, schematic diagram and guidance for the operation of the bilge and ballast system (if fi tted), together with a description of its limitations such as draining of spaces not directly connected to the systems. 19. Fuel oil storage and transfer procedures. 20. Description and capacity of main and emergency power systems. 21. Personnel transfer procedures. 22. Limiting conditions for crane operations. 23. Guidance on damage control for incidents of fl ooding and unexpected settlement. Page 153 of 166 80 APPENDIX E Typical spot location reports Page 154 of 166 81 APPENDIX F Foundation Risks: Methods for Evaluation and Prevention RISK Installation problems Punch-through Settlement/bearing failure Sliding failure Scour Geohazards (mudslides, mud volcanoes etc) Gas pockets/shallow gas Leg extraction diffi culties Eccentric spudcan reactions Seabed slope Footprints of previous jack ups Faults Metal or other object, sunken wreck, anchors, pipelines etc. Local holes (depressions) in seabed, reefs, pinnacle rocks, non-metallic structures or wooden wreck Bathymetric survey Sea fl oor survey Geophysical survey Soil sampling and other geotechnical testing and analysis Geophysical survey Soil sampling and other geotechnical testing and analysis Ensure adequate jack up preload capability Geophysical survey Soil sampling and other geotechnical testing and analysis Increase vertical spudcan reaction Modify the spudcans Bathymetric and sea fl oor survey (identify sand waves) Surface soil samples and seabed currents Inspect spudcan foundation regularly Install scour protection (gravel bag/artifi cial seaweed) when anticipated Sea fl oor survey Geophysical survey Soil sampling and other geotechnical testing and analysis Geophysical survey Geophysical survey Magnetometer and sea fl oor survey Sea fl oor survey Diver/ROV inspection Soil sampling and other geotechnical testing and analysis Consider change in spudcans Jetting/airlifting Geophysical survey Geophysical survey (buried channels or footprints) Soil sampling and other geotechnical testing and analysis Seabed modifi cation Geophysical survey Seabed modifi cation Evaluate site records Prescribed installation procedures Consider fi lling/modifi cation of holes as necessary METHODS FOR EVALUATION & PREVENTION Page 155 of 166 82 Source: Adapted from recommended practice for the site-specifi c assessment of mobile jack-up units, rev 2 APPENDIX G Flowchart for Jack-up Site Assessment Overall fl owchart for the assessment Page 156 of 166 83 APPENDIX H Leg Penetration Check and Air Gap Calculation Level the hull at zero air gap immediately after preloading to check the individual leg penetrations and to defi ne the level of the hull above LAT Leg number Leg height mark at top of jack frame - Jack frame height above hull baseline = Leg below hull - Height of tide - Water depth at LAT = Leg penetration 1 2 3 4 5 6 Page 157 of 166 84 MINIMUM (SURVIVAL) HULL ELEVATION A or B whichever is greatest A) LAT + HAT + surge + wave crest elevation + 1.5m B) To clear the 10,000 year return period wave crest APPENDIX H continued Page 158 of 166 85 APPENDIX I Checklist for jack-Up suitability Assessment Note: This checklist is presently comprised of approximately 60 questions which are intended to provide an outline assessment of a jack-up’s suitability for a proposed operation. Negative or uncertain responses to checklist items suggest issues that may require clarifi cation and/or a more detailed independent assessment by consultants with experience of jack-up operations. Ref 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Management and manning Is the owner or operator (the contractor) an established marine contractor with experience of the management and operation of type of jack-up vessels commonly deployed for the type of work required? Does the contractor a) employ civil or structural engineers capable of carrying out jack-up related analyses associated with structural capacity, site-specifi c assessments, vessel motion response and seafastening design, and heavy lifts, or b) routinely engage third party engineering services to undertake the required analyses? Does the contractor a) employ a geotechnical engineer capable of performing soils assessments for jack-up site-specifi c assessments, or b) routinely engage recognised soils experts to undertake the required assessments? Does the contractor employ a competent person having the requisite qualifi cations, skills and experience to conduct a jack-up site-specifi c assessment and/or to verify that the site-assessment has been conducted in accordance with the recommended practice? If not, are recognised marine consultants with experience of jack-up operations routinely engaged to conduct or to verify the assessments? Does the contractor a) employ master mariners and/or marine engineers for planning and preparation, production of procedure documents, and execution of jack-up operations, or b) routinely engage third party services to undertake these tasks? Is the contractor capable of planning jack-up operations in accordance with the provisions described in section 4 of this guideline? Does the contractor understand the regulatory requirements and guidelines for the operation of jack-ups in UK waters as described in section 2 of this guideline? Is the jack-up manned in accordance with section 3 of this guideline? JACK-UP SUITIBILITY ASSESSMENT check 2 2.1 2.2 2.3 2.4 Off shore jack-ups with accommodation - unrestricted operations Is the jack-up entered on a vessel registry of a recognised maritime nation (the fl ag state)? Have outstanding fl ag state recommendations (if any) been cleared? Is the jack-up vessel classed in accordance with the rules of a recognised classifi cation society and a member of the International Association of Class Societies (IACS)? Does the class notation a) Include the term “self-elevating” or b) otherwise defi nitively cover the design, construction and survey of the unit’s capacity for safe elevation? (Some classifi cations relate solely to the design as a fl oating vessel). Does the class status report (and/or the class certifi cates) confi rm that the jack-up is currently class maintained? Have all outstanding class recommendations, defects or defi ciencies that may have an impact on the proposed operations been rectifi ed or complied with? Are the certifi cates and documentation in accordance with this guideline Appendix C? Is the jack-up provided with a class approved operating manual? check 2.5 2.6 2.7 2.8 Page 159 of 166 86 3 4 3.1 4.1 3.2 4.2 3.3 4.3 3.4 4.4 3.5 4.5 3.6 4.6 3.7 4.7 4.8 4.9 4.10 Small unmanned inshore jack-ups – weather restricted operation Suitability of the jack-up for transit to site: Is the jack-up entered on a small vessel registry of a recognised maritime Nation (the fl ag State)? Have any outstanding fl ag state recommendations been cleared? Has the unit’s design limits for fl oating and elevated operations been clearly stated by the vessel manufacturer in a design report or the operating manual? Has the design report or operating manual been verifi ed by an independent authority? If the jack-up is not classed or not covered under MCA MGN-280, is there an independent survey report confi rming that the unit is in satisfactory condition with no outstanding defects or defi ciencies? Are the certifi cates and documentation in accordance with this guideline Appendix C? Is the jack-up provided with an operating manual and does the operating manual include the information suggested in Appendix D? If the proposed work site is in coastal waters or an off shore area, is the jack-up designed and certifi ed for transit afl oat on its own hull beyond port limits? Does the vessel’s certifi ed trading area include the whole of the proposed transit route and the operating site? Has the limiting sea state for transit afl oat been defi ned? Will the limiting sea state for operations afl oat unreasonably restrict the jack-up’s capability to undertake the transit effi ciently in the predicted seasonal conditions? If project cargo and equipment is to be transported on the deck of the jack-up, can the total displacement (including variable load plus deck load) and the trim and the allowable VCG be maintained within the allowable limits for the fl oating condition? Does the jack-up meet the intact and damage stability requirements for the loaded condition as described in this guideline section 6? In the loaded condition, is the total elevated weight and the centre of gravity within the allowable limits for the a) Jacking mode? b) Elevated operating mode (including lifting operations) and c) elevated survival mode? If project cargo and equipment is to be transported on the deck of the jack-up, will the grillage and seafastening arrangements meet the requirements described in section 7 of this guideline? If project cargo and equipment is to be transported on the deck of the jack-up, can the cranes be stowed and seafastened with the booms lowered in the cradles. If the jack-up is self-propelled and/or fi tted with a dynamic positioning system, does the unit comply with the provisions of this guideline section 11? check check 4.11 4.12 If the jack-up is non-propelled or propulsion assisted, is the unit capable of complying with the arrangements as specifi ed in the guideline sections 11 & 12? If the jack-up is non-propelled or propulsion assisted, will it be towed by suitable towing vessels that meet the requirements of this guideline section 13? Page 160 of 166 87 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 Suitability of the jack-up for positioning and elevating Has the site geophysical data been obtained as described in section 8 of this guideline and the survey reports delivered to the contractor? Has the site meteorological data been obtained and delivered to the contractor in the form of a spot location report (Appendix E)? Has a site soil investigation been carried out and the results delivered to the contractor? Has the contractor reviewed the site survey and soil investigation reports and confi rmed that the data received is adequate and suffi cient to complete a site-specifi c assessment for the jack-up in accordance with the recommended practice? Is the jack-up fi tted with a station keeping system (DP or 4-Point Mooring System) in accordance with this guideline Section 14? Can the contractor devise an approach and/or a mooring plan that will allow jack-up be moved into the required position while maintaining the minimum clearances prescribed in this guideline section 14? Are the water depths and tidal levels in the approach to, and on site, suffi cient to allow the jack-up to be moved always afl oat on to the location? In areas where high velocity tidal currents fl ow, is the duration of slack water periods of adequate length to allow safe positioning and subsequent removal of the jack-up? Based upon the information received, is the contractor satisfi ed that there are no signifi cant or unusual marine hazards in the approach to, or on site, that could have an impact on jack-up positioning? Based upon the information received, is the contractor satisfi ed that there are no signifi cant or unusual seabed surface features or soil foundation hazards for jacking and preloading and for subsequent elevated operations? If seabed surface and/or foundation hazard(s) have been identifi ed, is the contractor confi dent that procedures can be developed to safe jacking, preloading and elevated operations? Have the foundation hazard(s) and the proposed procedures been assessed and found suitable by independent geotechnical engineers and jack-up move experts? Based upon the information received, has the contractor determined through site-specifi c assessment that the jack-up is capable of operating on site in a) weather restricted Mode or b) unrestricted Mode? If the jack-up is capable of operating only in weather restricted mode, will this unreasonably restrict the jackup’s capability to operate effi ciently in the elevated mode on site in the expected seasonal conditions? Is the jack-up capable of complying with the arrangements for mooring and positioning on site as described in section 14 of this guideline? check 5.11 5.12 5.13 5.14 5.15 Page 161 of 166 88 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 Suitability of the jack-up for elevated operations Has the contractor fully understood the objectives to be achieved? Are the contractor’s personnel capable of planning and executing the operations necessary to achieve the objectives without engineering assistance from third party services? Is the jack-up a suitable platform for the execution of the operations with respect to size, confi guration, deck height, deck strength, accommodation and facilities? Based upon the site-specifi c assessment, is the jack-up’s leg length suffi cient to allow elevation to the extreme storm survival air gap (see Appendix H) If the leg length is not suffi cient to achieve the survival air gap, is it suffi cient to allow elevation to a working air gap? Based upon the site-specifi c assessment, is the jack-up capable of remaining elevated on location in the seasonal 50 year extreme storm condition with all stresses remaining within allowable limits in accordance with the RP? If the jack-up cannot achieve the minimum survival air gap and/or cannot safely withstand the extreme storm condition, can the proposed elevated operations be completed safely by the jack-up as a weather restricted operation in accordance with this guideline section 5? If the jack-up is operating in Weather Restricted mode, will the operating restrictions that apply and the potential need to often remove the unit to shelter have an unreasonable adverse impact on the proposed works in the seasonal weather considered. If a weather restricted operation is proposed, can the elevated operations be suspended and the jack-up removed to a safe standby location or to shelter within 48 hours? Is the contractor in possession of, and familiar with, at least one of the guideline documents for marine lifting operations listed in this guideline section 15.1.2? Are the crane and the lifting gear capable of performing the proposed lifting operations (if any) in accordance with the specifi ed guidelines and with this guideline section 15? check 6.11 Page 162 of 166 BWEA Greencoat House Francis Street London SW1P 1DH United Kingdom Tel: +44 (0)20 7901 3000 Fax: +44 (0)20 7901 3001 www.bwea.com Page 163 of 166 Appendix I Useful References Olifield Publications Ltd. OilfIeld Seamanship Series, volume two — Jack-up Moving Bennet & Associates & Offshore Technology Development Inc. Jack-Up Units. A Technical Primer for the Offshore Industry Professional UK Government The Health and Safety at Work Act 1974 The Management of Health and Safety at Work Regulations 1999 The Construction (Design and management) Regulations 2007 (CDM) Provision and Use of Work Equipment Regulations 1998 Lifting Operations and Lifting Equipment Regulations 1 998 (LOLER) - HSE - Technical guidance on the safe use of lifting equipment offshore - HSE - Safe use of lifting equipment — Approved Code of Practice and Guidance HSE Information Sheets Jack-up (self elevating) installations: rack phase difference http://www.hse.gov.uk/offshore/infosheets/is4-2007.pdf Jack-up (self elevating) installations: floating damage stability survivability http://www.hse.gov.uk/offshore/infosheets/is6-2007.pdf Jack-up (self elevating) installations: review and location approval using desk-top risk assessments in lieu of undertaking site soils borings http://www.hse.gov.ukloffshore/infosheets/is3-2008.pdf HSE Information The safe approach, set-up and departure of jack-up rigs to fixed installations http://www.hse.gov.uk/foi/internalops/hid/spc/spctosd21.htm Guidance on Procedures for the Transfer of Personnel by Carriers HSE Research Reports - OTO series SNAME 5-5B WSD 0: Comparison with SNAME 5-5A LRFD and the SNAME 5-5A North Sea Annex http://www.hse.gov.uk/research/otopdf/2001/oto01001.pdf Det Norske Veritas Det Norske Veritas (DNV) Rules for the Planning and Execution of Marine Operations: • Load Transfer Operations (issued 1996) • Towing (issued 1996) • Special SeaTransports (issued 1996) • Offshore Installation (issued 1996) • Lifting (issued 1996) • Sub Sea Operations (issued 1996) • Transit and Positioning of Mobile Offshore Units (issued 2000) Det Norske Verftas (DNV) Classification Notes Section 8: Foundation of Jack-up Platforms Page 164 of 166 Lloyds Register Code for Lifting Appliances in a Marine Environment 2008 UK Offshore Operators Association Guidelines for Safe Movement of Self-Elevating Offshore Installations (Jack-ups) UK Offshore Operators Association. April 1995 issue No.1 North Sea Lifting (NSL) Suitability of Cranes for Man Riding Self-elevating installations (jack-up units) http://www.hse.gov.uk/research/otohtm/2001/oto01051.htm Stability of jack-ups in transit http://www.hse.gov.uklresearch/otopdf/1995/oto95022.pdf HSE RR series Review of the jack-ups: Safety in transit (JSIT) technical working group http://www.hse.gov.uk/research/rrhtm/rr049.htm Guidelines for jack-up rigs with particular reference to foundation stability http:/www.hse.gov.uk/research/rrhtm/rr289.htm International Maritime Organisation MODU Code. Code for the construction and equipment of mobile offshore drilling units, consolidated edition, 2001 International Safety Management (ISM) Code 2002 Safety of Life at Sea (SOLAS 1974) International Convention on Loadlines 1966 Preventing Collisions at Sea Regulations COLREGS Standards of Training, Certification and Watchkeeping for Seafarers (STCW) 1978 Prevention of Pollution from Ships MARPOL 1973/78 Prevention of Marine Pollution by Dumping of Wastes and Other Matter I972 Incidents by Hazardous and Noxious Substances, 2000 (HNS Protocol) Control of Harmful Anti-fouling Systems on Ships (AFS), 2001 IMO MSC Circ.645, “Guidelines for Vessels with Dynamic Positioning Systems” IMO MSC Circ.738, “Guidelines for Dynamic Positioning System (OP) Operator Training” Marine and Coastguard Agency MCA Code of Safe Working Practice for Merchant Seaman MCA Small Commercial Vessel and Pilot Boat (SCV) Code (as currently set out in MGN 280) MCA - MGN 371 ‘Offshore Renewable Energy Installations (OREIs) Guidance on UK Navigational Practice, Safety and Emergency Response Issues’ and the supporting note: MCA -‘Offshore Renewable Energy Installations Emergency Response Cooperation Plans (ERCoP) for SAR Helicopter Operations’ Society of Naval Architects and Marine Engineers Society of Naval Architects and Marine Engineers (SNAME) Technical and Research Bulletin TRS-SA Guidelines for Site Specific Assessment of Mobile Jack-up Units Including the Recommended Practice and Commentary International Organisation for Standardisation ISO 19901-1:2005(E) Part 1: MetOcean design and Operating considerations. The Society of Naval Architects SNAME Bulletin 5-5A 2008 1 INTRODUCTION 1.1 The purpose of this document is to provide a Recommended Practice (PRACTICE) for use with the 'Guideline for Site Specific Assessment of Jack-Up Units' (GUIDELINE). Each assessment should address the areas of this document as appropriate for the particular jack-up and location as described in Section 1.4 of the GUIDELINE. 1.2 This document has been formulated as a result of a Joint Industry Project involving all sections of the industry. It is not intended to obviate the need for applying sound judgment as to when and where this PRACTICE should be utilized. 1.3 The formulation and publication of this PRACTICE is not in any way intended to impose calculation methods or procedures on any party. It leaves freedom to apply alternative practices within the framework of the accompanying GUIDELINE. 1.4 This PRACTICE relates only to the assessment of independent leg jack-up units in the elevated condition. The development has been based on 3 legged truss-leg units and caution is advised when applying the PRACTICE to other configurations. Transportation to and from the site and moving on and moving off location are not covered in this document. 1.5 This PRACTICE may be revised if and when more information/research results become available. 1.6 For further details of the applicability and limitations, refer to the GUIDELINE. 1.7 This PRACTICE may be used by anyone desiring to do so, and a diligent effort has been made by the authors to assure the accuracy and reliability of the information contained herein. However, the authors make no representation, warranty or guarantee in connection with the publication of this PRACTICE and hereby expressly disclaim any liability or responsibility for loss, damage or injury resulting from its use, for any violation of local regulations with which a recommendation may conflict, or for the infringement of any patent resulting from the use of this publication. 1.8 The load factors presented in Section 8 herein were determined from the reliability analysis of a limited number of jack-up/site combinations. The load factors are provisional pending the further evaluation of the results from a wider range of assessments by the SNAME OC-7 panel. Alternative values can be used when acceptable rationale is provided. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 10 Rev 3, August 2008 2 OBJECTIVES 2.1 The principal objective of this PRACTICE is to provide acceptance criteria and associated engineering methods that may be applied in the site specific assessment of a jack-up to: a) Establish the geometric suitability of the jack-up with respect to leg length, airgap and leg penetration. b) Establish that the jack-up is structurally adequate for its intended application. c) Ensure that the foundation can offer suitable support to meet this objective. d) Ensure adequate overturning stability. 2.2 This PRACTICE is applicable to the various possible modes of jack-up operation (drilling, production, accommodation, construction, etc.) in all areas of the world. It should be noted that different extreme environmental return periods may be appropriate for manned and unmanned operations. 2.3 The user of this PRACTICE is advised that, in some areas of the world, the requirements of the local regulatory bodies may be more onerous than those recommended herein. 2.4 Scope of the Assessment 2.4.1 The primary objective of the site specific assessment is to ensure the integrity of the jackup in the elevated condition. The assumptions incorporated into the assessment must conform with the structural condition of the unit. 2.4.2 The assessment will normally assume that the jack-up is in sound mechanical and structural condition and it is the responsibility of the owner to ensure that this is so. The existence of valid documents indicating that the jack-up is presently in class by a recognized classification society is usually sufficient to verify the mechanical and structural condition of the jack-up to the assessor. 2.4.3 Accidental loads (dropped objects, ship impact, etc.) are not specifically addressed and should be covered at the design stage. Furthermore, the site specific assessment addresses the global structural integrity, hence local damage not affecting the overall integrity is outside the scope of the PRACTICE. 2.4.4 As indicated in Section 1.4.1 of the GUIDELINE, the assessment of the jack-up may be carried out at various degrees of complexity. These are as expanded below, at increasing levels of complexity. The objective of the assessment is to show that the acceptance criteria of Section 8 of this PRACTICE are met. If this is achieved by a particular level there is no need to consider a more complex level. 1. Compare site conditions with design conditions or other existing assessments determined in accordance with this PRACTICE. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 11 Rev 3, August 2008 2.4.4 2. Carry out appropriate calculations according to the simple methods given in this PRACTICE. Possibly compare results with those from existing more detailed/complex calculations. 3. Carry out appropriate detailed calculations according to the more complex methods given in this PRACTICE. In all cases the adequacy of the foundation should be assessed. An overall flow chart for the assessment is given in Figure 2.1 overleaf. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 12 Rev 3, August 2008 Figure 2.1 - Overall flow chart for the assessment COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 13 Rev 3, August 2008 3 ASSESSMENT INPUT DATA 3.1 Rig data 3.1.1 The information that may be required to perform the assessment is outlined in Section 2.1 of the GUIDELINE. 3.1.2 The operating procedures and limitations of the jack-up should be clearly defined in the Operating Manual. Those sections of the Operating Manual which give relevant information and are required to perform a site assessment in accordance with this PRACTICE are to be provided. 3.2 Functional Loadings 3.2.1 The operating and survival conditions may be treated separately, provided it is practical to change the mode of the jack-up unit from operating to survival mode on receipt of an unfavorable weather forecast, and appropriate procedures exist. The limits of operational loading conditions may depend on the drilling program proposed and consideration should be given to loadings on the conductors if supported by the jack-up. 3.2.2 For both operational and survival conditions, the following shall be defined: a) Maximum and minimum elevated weight and weight distribution (fixed and variable load), excluding legs. In the absence of other information the minimum elevated weight may normally be determined assuming 50% of the variable load permitted by the operating manual. b) Extreme limits of center of gravity position (or reactions of the elevated weight on the legs) for the conditions in a) above. c) Substructure and derrick position, hook load, rotary load, setback and conductor tensions for the conditions in a) above. d) Weight, center of gravity and buoyancy of the legs. 3.2.3 With reference to Section 4.1.3 of the GUIDELINE, if a minimum elevated weight or a limitation of center of gravity position is required to meet the overturning safety factor in survival conditions, then the addition of water in lieu of variable load is permitted, provided that: a) Maximum allowable loadings are not exceeded. b) Procedures, equipment and instructions exist for performing the operation. c) The maximum variable load, including added water, is used for all appropriate assessment checks (preload, stress, etc.). 3.3 Environmental Conditions - General 3.3.1 The environmental data required for an assessment and their application are discussed in Section 2.3 of the GUIDELINE. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 14 Rev 3, August 2008 3.3.2 Section 2.3 of the GUIDELINE recommends that 50 year return period extremes are normally used, however in particular circumstances other return periods may be appropriate. 3.3.3 Unless there is specific data to the contrary, wind, wave and current loadings shall be considered to be those caused by the individual return period extremes acting in the same direction and at the same time as the extreme water level. Seasonally adjusted values may be adopted as appropriate to the duration of the operation. Note: Where directional and/or seasonal data are utilized, these should generally be factored so that the data for the worst direction and/or season equals the omni-directional/all-year data for the assessment return period. 3.4 Wind 3.4.1 The wind velocity shall be the 1 minute sustained wind for the assessment return period, related to a reference level of 10.0m above mean sea level. The Commentary discusses the conversion of data for averaging periods other than 1 minute to 1 minute values. 3.4.2 The wind velocity profile is normally taken as a power law with exponent 1 10 unless site specific data indicates otherwise (see Section 4.2.2). 3.4.3 Different jack-up configurations (weight, center of gravity, cantilever position, etc.) may be specified for operating and survival modes. In such cases, the maximum wind velocity considered for the operating mode should not exceed that permitted for the change to the survival mode. 3.5 Waves 3.5.1 The extreme wave height environment used for survival conditions shall, as a minimum, be computed according to the following sub-sections based on the three-hour storm duration with an intensity defined by the significant wave height, Hsrp, for the assessment return period. The seasonally adjusted wave height may be used as appropriate for the operation. The wave height information for a specific location may also be expressed in terms of Hmax, the individual extreme wave height for the return period, rather than the significant wave height Hsrp. The relationship between Hsrp and Hmax must be determined accounting for the effects of storms (longer than 3 hours) and for the additional probability of other return period storms (see Commentary Section C3.5.1). This relationship will depend on the site specific conditions, however Hsrp may usually be determined from Hmax using the generally accepted relationship for non-cyclonic areas: Hsrp = Hmax/1.86 For cyclonic areas the recommended relationship is: Hsrp = Hmax/1.75 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 15 Rev 3, August 2008 3.5.1 Note: The wave load can be computed either stochastically (through a random frequency or time domain approach) or deterministically (through an individual maximum wave approach). The scaled wave heights for the two approaches are discussed in Sections 3.5.1.1 and 3.5.1.2 respectively (see Commentary). The scaled wave heights are to be used only in conjunction with the associated kinematics modeling recommended in Section 4.4 and the hydrodynamic coefficients given in Sections 4.6 to 4.8. 3.5.1.1 For stochastic/random wave force calculations Airy wave theory is implied, see Section 4.4.2. To account for wave asymmetry, which is not included in Airy wave theory, a scaling of the significant wave height should be applied to capture the largest wave forces at the maximum crest amplitude. The effective significant wave height, Hs, may be determined as a function of the water depth, d in meters, from: Hs = [1 + 0.5e(-d/25)] Hsrp (d ≥ 25m) and should be used with the wave kinematics model described in Section 4.4.2. For water depths less than 25m a regular wave analysis should be considered. The selection of wave period for use in stochastic/random wave force analysis is discussed in Section 3.5.3 and the Note thereto. 3.5.1.2 For deterministic/regular wave force calculations it is appropriate to apply a kinematics reduction factor of 0.86 in order to obtain realistic force estimates (see Commentary). This factor may be considered to implicitly account for spreading and also the conservatism of deterministic/regular wave kinematics traditionally accomplished by adjusting the hydrodynamic properties. The factor should be applied by means of a reduced wave height, Hdet. Hdet may be determined as a function of Hmax from: Hdet = 0.86 Hmax The use of a factor smaller than 0.86 may be justified by analysis explicitly accounting for the effects of three-directional spreading. However, such effects should be properly balanced by the inclusion of second-order interaction effects between spectral wave components. The wave loads should be determined using an appropriate wave kinematics model in accordance with Section 4.4.1. In the analysis a single value for the wave period Tass, in seconds, associated with the maximum wave may be considered. Unless site specific information indicates otherwise Tass will normally be between the following limits: 3.44 (H ) srp < Tass < 4.42 (H ) srp where Hsrp is the return period extreme significant wave height in meters. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 16 Rev 3, August 2008 3.5.2 For airgap calculations the wave crest elevation may be obtained from the formulations of an appropriate deterministic wave theory (see Section 4.4.1) and the maximum wave height, Hmax, from the relationship: Hmax = 1.86 Hsrp In Tropical Revolving Storm areas the relationship: Hmax = 1.75 Hsrp may alternatively be applied. It is noted that the minimum return period recommended by the GUIDELINE for Hsrp for airgap calculations is 50 years, even if a lower return period is used for other purposes. 3.5.3 Where the analysis method requires the use of spectral data, the choice of the analytical wave spectrum and associated spectral parameters should reflect the width and shape of spectra for the site and significant wave height under consideration. In cases where fetch and duration of extreme winds are sufficiently long a fully developed sea will result (this is rarely realized except, for example, in areas subject to monsoons). Such conditions may be represented by a Pierson-Moskowitz spectrum. Where fetch or duration of extreme winds is limited, or in shallow water depths, a JONSWAP spectrum may normally be applied (see Note at the end of this Section). The wave spectrum can be represented by the power density of wave surface elevation Sηη(f) as a function of wave frequency by: Sηη(f) = (16I0(γ))-1Hs 2TP(TPf)-5exp(-1.25/(TPf)4)γq [Note: An alternative formulation is given in the Commentary] where; q = exp(-(Tpf-1)2/2σ2) with: σ = 0.07 for Tpf ≤ 1 σ = 0.09 for Tpf > 1 (Carter 1982, [1]) and; Hs = significant wave height (meters), including depth correction, according to Section 3.5.1.1 Tp = peak period (seconds) f = frequency (Hz) γ = peak enhancement factor I0(γ) = is discussed below. The above definition yields a single parameter Pierson-Moskowitz spectrum when γ = 1 and Tp = 5 (H ) s , with Hs in meters. In this case an appropriate Tp/Tz ratio is 1.406 (see below). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 17 Rev 3, August 2008 When considering a JONSWAP spectrum, the peak enhancement factor γ varies between 1 and 7 with a most probable average value of 3.3. There is no firm relationship between γ, Hs and Tp. Relationships between variables for different γ according to Carter (1982) [1] are as follows: γ 1 2 3 3.3 4 5 6 7 I0(γ) .200 .249 .293 .305 .334 .372 .410 446 Tp/Tz 1.406 1.339 1.295 1.286 1.260 1.241 1.221 1.205 Alternatively: I 0 Ln 0 2 1 0287 ( ) . . () γ γ = − ⎡ ⎣ ⎢⎢ ⎤ ⎦ ⎥⎥ Unless site specific information indicates otherwise γ = 3.3 may be used. For a given significant wave height the wave period depends on the significant wave steepness which in extreme seas in deep water often lies within the range 1/20 to 1/16. This leads to an expression for zero-upcrossing period Tz, related to Hsrp in meters, as follows: 3.2 (H ) srp < Tz < 3.6 (H ) srp However in shallow water the wave steepness can increase to 1/12 or more, leading to a zero-upcrossing period Tz as low as 2.8 (H ) srp . This is because the wave height increases and wave length decreases for a given Tz. Note: If a JONSWAP spectrum is applied the response analysis should consider a range of periods associated with Hsrp based on the most probable value of Tp plus or minus one standard deviation. However it should be ensured that the assumptions made in deriving the spectral period parameters are consistent with the values used in the analysis. Alternatively, applicable combinations of wave height and period may be obtained from a scatter diagram determined from site specific measurements; in this case specialist advice should be obtained on a suitable spectral form for the location. To avoid the need for analyses of several wave periods a practical alternative is to use a 2 parameter spectrum with γ = 1.0 in combination with the site specific most probable peak period. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 18 Rev 3, August 2008 3.5.4 For stochastic/random wave force calculations, the short-crestedness of waves (i.e. the angular distribution of wave energy about the dominant direction) may be accounted for when site-specific information indicates that such effects are applicable. In all cases the potential for increased response due to short-crested waves should be investigated. The effect may be included by means of a directionality function F(α), as follows: Sηη(f, α) = Sηη(f).F(α) where; α = angle between direction of elementary wave trains and dominant direction of the short-crested waves. Sηη(f, α) = directional short-crested power density spectrum. F(α) = directionality function. and, in the absence of more reliable data: F(α) = C.Cos2nα for - π 2 ≤ α ≤ π 2 where; n = power constant C = constant chosen such that: π/2 Σ F(α) .dα = 1.0 -π/2 The power constant n, should not normally be taken as less than: n = 2.0 for fatigue analysis n = 4.0 for extreme analysis 3.5.5 Where the natural period of the jack-up is such that it may respond dynamically to waves (Section 7.3), the maximum dynamic response may be caused by wave heights or seastates with periods outside the ranges given in Sections 3.5.1.2 and 3.5.3. Such conditions shall also be investigated to ensure that the maximum (dynamic plus quasistatic) response is determined. 3.5.6 For fatigue calculations (Section 7.4), the long term wave climate may be required. For the purposes of the fatigue analysis the long-term data may be presented deterministically in terms of the annual number of waves predicted to fall into each height/period/direction group. Alternatively the probability of occurrence for each seastate (characterized by wave energy spectra and the associated physical parameters) may be presented in the form of a significant wave height versus zero-upcrossing period scatter diagram or as a table of representative seastates. 3.6 Current 3.6.1 The extreme wind driven surface current velocity shall be that associated with the assessment return period wind, seasonally adjusted if appropriate. When directional information regarding other current velocity components is available the maximum surface flow of the mean spring tidal current and the assessment return period surge current, seasonally adjusted if appropriate, shall be vectorially added in the down-wind direction and combined with the wind driven surface current as indicated in Section 3.6.2. If directional data are not available the components shall be assumed to be omniirectional and shall be summed algebraically. Note: A site specific study will normally be required to define the current velocity components. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 19 Rev 3, August 2008 3.6.2 The current profile may be expressed as a series of velocities at certain stations from seabed to water surface. Unless site specific data indicates otherwise, and in the absence of other residual currents (such as circulation, eddy currents, slope currents, internal waves, inertial currents, etc.), an appropriate method for computing current profile is (see Figure 3.1): VC = Vt + Vs + (Vw - Vs) [(h+z)/h], for |z| ≤ h and Vs < Vw VC = Vt + Vs for |z| > h or Vs ≤ Vw where; VC = current velocity as a function of z. Note that a reduction may be applicable according to Section 4.5. Vt = downwind component of mean spring tidal current. Vs = downwind component of associated surge current (excluding wind driven component). Vw = wind generated surface current. In the absence of other data this may conservatively be taken as 2.6% of the 1 minute sustained wind velocity at 10m. h = reference depth for wind driven current. In the absence of other data h shall be taken as 5 meters. z = distance above still water level (SWL) under consideration (always negative). Figure 3.1 - Suggested current profile 3.6.3 In the presence of waves the current profile should be stretched/compressed such that the surface component remains constant. This may be achieved by substituting the elevation as described in Section 4.4.2. Alternative methods may be suitable, however mass continuity methods are not recommended. The current profile may be changed by wave breaking. In such cases the wind induced current could be more uniform with depth. 3.6.4 For a fatigue analysis, current may normally be neglected. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 20 Rev 3, August 2008 3.7 Water Levels and Airgap 3.7.1 The water depth at the location shall be determined and related to lowest astronomical tide (LAT). The relationship between LAT and Chart Datum is discussed in the Commentary. 3.7.2 The mean water level (MWL) related to the seabed shall be expressed as the mean level between highest astronomical tide (HAT) and lowest astronomical tide (LAT) i.e.: MWL = (HAT + LAT)/2 3.7.3 The extreme still water level (SWL) shall be expressed as a height above LAT, and shall be the sum of; Mean high water spring tide (MHWS) + 50 year extreme storm surge (see Note 1). unless reliable data indicates that an alternative summation is appropriate. 3.7.4 When lower water levels are more onerous the minimum still water level (SWL) to be considered in the loading calculations shall be the sum of: Mean Low Water Spring Tide (MLWS) + 50 year negative Storm Surge. 3.7.5 The Airgap (see Note 2) is defined in Section 3.2 of the GUIDELINE as the distance between the underside of the hull and LAT during operations. It shall be not less than the sum of: Distance of the extreme still water level (SWL), from Section 3.7.3, above LAT + 50 year extreme wave crest height associated with Hmax as defined in Section 3.5.2 (see Note 1), + 1.5m Clearance to the underside of the hull (or any other vulnerable part attached to the hull, if lower). See Commentary. Notes: 1. Section 3.2.1 of the GUIDELINE recommends that values for a return period of no less than 50 years be applied, even if a lower return period is used for other purposes. 2. The definition of Airgap used herein differs from that used in other areas of offshore engineering where the Clearance used here is often defined as Airgap. In areas subject to freak waves a higher airgap may be applicable. 3.8 Temperatures The lowest average daily air and water temperatures shall be compared with the steel design temperature limits of appropriate parts of the jack-up. If these are not met, suitable adjustments should be made to the properties applied in the strength assessment. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 21 Rev 3, August 2008 3.9 Marine Growth Where existing marine growth is not to be cleaned between locations or where the operation is to last long enough for significant growth to occur, the influence of growth on the leg hydrodynamic properties should be considered as stated in Section 4.2.3 of the GUIDELINE. Where applicable, location specific data should be obtained. In the absence of such data, default values for thickness and distribution are given in Section 4.7.3. 3.10 Leg Length Recommendations regarding the reserve leg length are given in Section 3.3 of the GUIDELINE. 3.11 Geotechnical and Geophysical Information Adequate geotechnical and geophysical information must be available to assess the location and the foundation stability. Aspects which should be investigated are shown in Table 3.1 and are discussed in more detail in the referenced Sections. The information obtained from the surveys and investigations set out in Sections 3.12 to 3.16 is required for areas where there is no data available from previous operations. In areas where information is available it may be possible to reduce the requirements set out below by use of information obtained from other surveys or activities in the area. See Section 2.4 of the GUIDELINE. 3.12 Bathymetric Survey 3.12.1 An appropriate bathymetric survey should be supplied for an area approximately 1 kilometer square centered on the location. Line spacing of the survey should typically be not greater than 100 meters x 250 meters over the survey area. Interlining is to be performed within an area 200 meters x 200 meters centered on the location. Interlining should have spacing not exceeding 25 meters x 50 meters. 3.12.2 Further interlining should be performed if any irregularities are detected. 3.13 Seabed Surface Survey 3.13.1 The seabed surface shall be surveyed using sidescan sonar or high resolution multibeam echosounder techniques and shall be of sufficient quality to identify obstructions and seabed features and should cover the immediate area (normally a 1 km square) of the intended location. The slant range selection shall give a minimum of 100% overlap between adjacent lines. A magnetometer survey may also be required if there are buried pipelines, cables and other metallic debris located on or slightly below the sea floor. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 22 Rev 3, August 2008 REFERENCE RISK METHODS FOR EVALUATION & SECTION(S) PREVENTION Installation problems - Bathymetric survey 3.12 Punch-through - Shallow seismic survey 3.14 - Soil sampling and other geotechnical 3.16 testing and analysis 6.2.6 Settlement under storm - Shallow seismic survey 3.14 loading/Bearing failure - Soil sampling and other geotechnical 3.16 testing and analysis 6.2.6 - Ensure adequate jack-up preload capability 6.3 Sliding failure - Shallow seismic survey 3.14 - Soil sampling and other geotechnical 3.16 testing and analysis 6.3.3 - Increase vertical footing reaction - Modify the footing(s) Scour - Bathymetric survey (identify sand 3.12 waves) 3.15 - Surface soil samples and seabed currents 6.4.3 - Inspect footing foundations regularly - Install scour protection (gravel bag/ artificial seaweed) when anticipated Seafloor instability - Side scan sonar, shallow seismic 3.13 (mudslides) survey 3.14 - Soil sampling and other geotechnical 3.16 testing and analysis 6.4.4 Gas pockets/ - Digital seismic with attribute 3.14 Shallow gas analysis processing (shallow seismic) 6.4.5 Faults - Shallow seismic survey 3.14 Metal or other object, - Magnetometer and side scan sonar 3.13 sunken wreck, anchors, - Diver/ROV inspection pipelines etc. Local holes (depressions) - Side scan sonar 3.13 in seabed, reefs, - Diver/ROV inspection pinnacle rocks or wooden wreck Legs stuck in mud - Geotechnical data 3.14 - Consider change in footings 3.16 - Jetting Footprints of previous - Evaluate location records 3.12 jack-ups - Consider filling/modification 3.13 of holes as necessary 6.4.2 Table 3.1 - Foundation risks, methods for evaluation and prevention COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 23 Rev 3, August 2008 3.13.2 Where seabed obstructions such as pipelines and wellheads are known to be present, sufficient information to enable safe positioning of the jack-up is required. In some cases an ROV or diver's inspection may be required in addition to a sidescan sonar survey. 3.13.3 Seabed surface surveys can become out-of-date, particularly in areas of construction/drilling activity or areas with mobile sediments. Good judgment should be used regarding the applicability of all surveys, especially with regard to validity. In open locations the maximum period for the validity of seabed surveys for debris and mobile sediment conditions should be determined taking account of local conditions. For locations close to existing installations seabed surveys for debris and sediment conditions should, subject to practical considerations, be undertaken immediately prior to the arrival of the jack-up at the location. 3.14 Geophysical Investigation - Shallow Seismic Survey 3.14.1 The principal objectives of the shallow seismic survey are: - To determine near surface soil stratigraphy. This requires correlation of the seismic data with (existing) soil boring data in the vicinity. - To reveal the presence of shallow gas concentrations. Due to the qualitative nature of seismic surveys it is not possible to conduct analytical foundation appraisals based on seismic data alone. This requires correlation of the seismic data with soil boring data in the vicinity through similar stratigraphy. 3.14.2 A shallow seismic survey should be performed over an approximately 1 kilometer square area centered on the location. Line spacing of the survey should typically not be greater than 100 meters x 250 meters over the survey area. Equipment should normally be capable of giving detailed data to a depth equal to the greater of 30 meters or the anticipated footing penetration plus 1.5 to 2 times the footing diameter. Further guidance on seismic surveys is given in reference [2]. 3.14.3 The survey report should include at least two vertical cross-sections passing through the location showing all relevant reflectors and allied geological information. The equipment used should be capable of identifying reflectors of 0.5m and thicker. 3.15 Surface Soil Samples The site investigation should be sufficient to identify the character of the soil surface and allow evaluation of the possibility of scour occurring. (See Commentary to Section 6.4.3) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 24 Rev 3, August 2008 3.16 Geotechnical Investigations 3.16.1 Site specific geotechnical testing is recommended in areas where any of the following apply: - the shallow seismic survey cannot be interpreted with any certainty, - significant layering of the strata is indicated, - the location is in a new operating area, - the area is known to be potentially hazardous. 3.16.2 A geotechnical investigation should comprise a minimum of one borehole to a depth equal to 30 meters or the anticipated footing penetration plus 1.5 to 2 times the footing diameter, whichever is the greater. All the layers should be adequately investigated and the transition zones cored at a sufficient sampling rate. The number of boreholes required should account for the lateral variability of the soil conditions, regional experience and the geophysical investigation. When a single borehole is made, the preferred location is at the center of the leg pattern at the intended location. 3.16.3 "Undisturbed" soil sampling and laboratory testing and/or in-situ cone penetrometer testing may be conducted. Other recognized types of in-situ soil testing may be appropriate such as vane shear and/or pressure meter tests. 3.16.4 The geotechnical report should include borehole logs, cone penetrometer records (if appropriate) and documentation of all laboratory tests, together with interpreted soil design parameters. Design parameters should be selected by a competent person. For the methods recommended in Section 6, the design parameters should include profiles of undrained shear strength and/or effective stress parameters, soil indices (plasticity, liquidity, grain size, etc.), relative density, unit weight and, where applicable, the over consolidation ratio (OCR). Additional soil testing to provide shear moduli and cyclic/dynamic behavior may be required if more comprehensive analysis are to be applied or where the soil strength may deteriorate under cyclic loading. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 25 Rev 3, August 2008 3 GLOSSARY OF TERMS - ASSESSMENT INPUT DATA C = Constant in expression for F(α). d = Water depth. f = Wave frequency. F(α) = Directionality function = C.Cos2nα h = Reference depth for wind driven current. = 5.0 m in the absence of other data. HAT = Water depth at highest astronomical tide. Hdet = Reduced wave height which may be used for deterministic wave force calculations, allowing for the conservatisms of higher order wave theories. = 1.60 Hsrp Hmax = The individual extreme wave height for a given return period defined as the wave height with an annual probability of exceedence of 1/return period (e.g. the 50 year return period Hm has a 2% annual probability of exceedence). Where local data is not available: Hmax = 1.86 Hsrp (for non-tropic revolving storm areas), Hmax = 1.75 Hsrp (for tropical revolving storm areas.) When Hmax is used for airgap calculations the minimum return period for Hsrp is recommended as 50 years, even if a lower return period is used for other purposes. Hs = Significant wave height (meters), including depth/asymmetry correction, according to Section 3.5.1.1. Hsrp = The assessment return period significant wave height for a three hour storm. I0(γ) = Parameter depending on γ used in the expression for Sηη(f). LAT = Water depth at lowest astronomical tide. MHWS = Height of mean high water spring tide above LAT. MLWS = Height of mean low water spring tide above LAT. MWL = Mean water level related to the seabed. n = Power constant in expression for F(α). = 2 or 4. q = Exponent in expression for Sηη(f). = exp(-(Tpf-1)2/2σ2) Sηη(f) = Power density spectrum of long crested wave surface elevation as a function of frequency, f. = (16I0(γ))-1Hs 2Tp(Tpf)-5exp(-1.25/(Tpf)4)γq Sηη(f,α) = Power density spectrum of short-crested wave surface elevation as a function of frequency, f. = Sηη(f).F(α) SWL = Height of extreme still water level above LAT. = MHWS + 50 year storm surge. = MLWS + 50 year negative storm surge (if more onerous). Tass = Wave period associated with Hmax (also used with Hdet). Tp = Peak period associated with Hsrp (also used with Hs). Tz = Zero-upcrossing period associated with Hsrp (also used with Hs). VC = Current velocity as a function of z. Vs = Downwind component of surge current. Vt = Downwind component of mean spring tidal current. Vw = Wind generated surface current. = 2.6% of 1 minute sustained wind velocity at 10m, in the absence of other data. z = Distance above still water level used in determination of VC. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 26 Rev 3, August 2008 3 GLOSSARY OF TERMS - ASSESSMENT INPUT DATA (Continued) α = Angle between direction of elementary wave trains and dominant direction of short-crested waves. γ = Peak enhancement factor used in expression for Sηη(f). For JONSWAP spectrum varies between 1 and 7 with a most probable average value of 3.3. σ = Constant in expression for q = 0.07 for Tpf <= 1 = 0.09 for Tpf > 1 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 27 Rev 3, August 2008 4 CALCULATION METHODS - HYDRODYNAMIC AND WIND FORCES 4.1 Introduction 4.1.1 The models, methods and coefficients given in this Section are matched to represent a consistent method such that the whole Section should be considered together. No force coefficients should be used unless they correspond to a particular stated analysis method. 4.1.2 The environmental forces may be determined according to the recommendations of this Section based on the dimensions of the members and the environmental criteria as described in Section 3 (wind speed, wave height and period and current velocity and profile). 4.1.3 Since differences in shape, proportions and even detail can result in considerable differences in the resultant forces, rational data from model testing may be used by the assessor at his discretion subject to the conditions of Section 4.7.6. 4.2 Wind Force Calculations 4.2.1 For wind load application according to Section 5.7.2, the wind force for each component (divided into blocks of not more than 15m vertical extent), FWi, may be computed using the formula: FWi = Pi AWi where; Pi = the pressure at the center of the block. AWi = the projected area of the block considered. and the pressure Pi shall be computed using the formula: Pi = 0.5 ρ (Vref)2 Ch Cs where; ρ = density of air (to be taken as 1.2224 kg/m3 unless an alternative value can be justified for the location). Vref = the 1 minute sustained wind velocity at reference elevation (normally 10m above MWL), see Section 3.4.1. Ch = height coefficient, as given in Section 4.2.2. Cs = shape coefficient, as given in Section 4.2.3. Note: The wind area of the hull and associated structures (excluding derrick and legs) may normally be taken as the profile area viewed from the direction under consideration. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 28 Rev 3, August 2008 4.2.2 Ch may be derived from the wind velocity profile; VZ = Vref (Z/Zref)1/N where; VZ = the wind velocity at elevation Z. Vref = the 1 minute sustained wind velocity at elevation Zref (normally 10m above MWL), see Section 3.4.1. N = 10 unless site specific data indicate that an alternative value of N is appropriate. Hence: Ch = (VZ/Vref)2 = (Z/Zref)2/N, but always ≥ 1.0 Alternatively, the approximate coefficients shown in Table 4.1 may be applied. The height is the vertical distance from the still water surface to the center of area of the block considered. Blocks which have a vertical dimension greater than 15 m shall be subdivided, and the appropriate height coefficients applied to each part of the block. Height m Height coefficient Ch 0 - 15 1.00 15 - 30 1.18 30 - 45 1.30 45 - 60 1.39 60 - 75 1.47 75 - 90 1.53 90 - 105 1.58 105 - 120 1.62 120 - 135 1.66 135 - 150 1.70 150 - 165 1.74 165 - 180 1.77 180 - 195 1.80 Table 4.1 - Height coefficients In deriving Table 4.1 the wind velocity used to obtain Ch for the block below 15.0m is the Vref value. For all other blocks the Ch value is that for the mid-height of the block. When using Table 4.1 the wind velocity is derived from Section 3.4.1 for a reference height of 10m above the still water. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 29 Rev 3, August 2008 4.2.3 Shape coefficients shall be derived from Table 4.2; Type of member or structure Shape coefficient Cs Hull side, (flat side) 1.0, based on total projected area Deckhouses, jack-frame structure, sub-structure, drawworks house, and other abovedeck blocks 1.1, based on the total projected area (i.e. the area enclosed by the extreme contours of the structure) Leg sections projecting above jack-frame structure and below the hull Cs = CDe as determined from Section 4.6, except that marine growth may be omitted. AWi determined from De and section length. Isolated tubulars (crane pedestals, etc.) 0.5 Isolated structural shapes (angles, channels, box, Isections) 1.5, based on member projected area Derricks, crane booms, flare towers (open lattice sections only, not boxed- in sections) The appropriate shape coefficient for the members concerned applied to 50% of the total projected profile area of the item (25% from each of the front and back faces) Shapes or combinations of shapes which do not readily fall into the above categories will be subject to special consideration Table 4.2 - Shape coefficients 4.3 Hydrodynamic Forces 4.3.1 Wave and current forces on slender members having cross sectional dimensions sufficiently small compared with the wave length should be calculated using Morison's equation. Note: Morison's equation is normally applicable providing: λ > 5Di where; λ = wavelength and Di = reference dimension of member (e.g. tubular diameter) Morison's equation specifies the force per unit length as the vector sum: ΔF = ΔFdrag + ΔFinertia = 0.5 ρ D CD vn ⏐vn⏐+ ρ CM A 􀀅u n where the terms of the equation are described in the following. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 30 Rev 3, August 2008 4.3.2 To obtain the drag force, the appropriate drag coefficient (CD) is to be chosen in combination with a reference diameter, including any required additions for marine growth, as described in Section 4.7. The Morison's drag force formulation is: ΔFdrag = 0.5 ρ CD D vn ⏐vn⏐ where; ΔFdrag = drag force (per unit length) normal to the axis of the member considered in the analysis and in the direction of vn. ρ = mass density of water (normally 1025 kg/m3). CD = drag coefficient ( = CDi or CDe from Section 4.6-7). vn = relative fluid particle velocity resolved normal to the member axis. D = the reference dimension in a plane normal to the fluid velocity vn ( = Di or De from Section 4.6-7). Note: The relative fluid particle velocity, vn, may be taken as: vn = un + VCn - α 􀀅r n where; un + VCn = the combined particle velocity found as the vectorial sum of the wave particle velocity and the current velocity, normal to the member axis. 􀀅rn = the velocity of the considered member, normal to the member axis and in the direction of the combined particle velocity. α = 0, if an absolute velocity is to be applied, i.e. neglecting the structural velocity. = 1, if relative velocity is to be included. May only be used for stochastic/random wave force analyses if: uTn/Di ≥ 20 where u = particle velocity = VC + πHs/Tz Tn = first natural period of surge or sway motion and Di = the reference diameter of a chord. Note: See also Section 7.3.7 for relevant damping coefficients depending on α. 4.3.3 To obtain the inertia force, the appropriate inertia coefficient (CM) is to be taken in combination with the cross sectional area of the geometric profile, including any required additions for marine growth, as described in Section 4.7. The Morison's inertia force formulation is: ΔFinertia = ρ CM A 􀀅u n where; ΔFinertia = inertia force (per unit length) normal to the member axis and in the direction of 􀀅u n. ρ = mass density of water (normally 1025 kg/m3). CM = inertia coefficient. A = cross sectional area of member ( = Ai or Ae from Section 4.6) 􀀅u n = fluid particle acceleration normal to member. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 31 Rev 3, August 2008 4.4 Wave Theories and Analysis Methods 4.4.1 For deterministic analyses an appropriate wave theory for the water depth, wave height and period shall be used, based on the curves shown in Figure 4.1, after HSE [3]. For practical purposes, an appropriate order of Dean's Stream Function or Stokes' 5th (within its bounds of applicability) is acceptable for regular wave survival analysis. 4.4.2 For random wave (stochastic) analyses, it is recommended that the random seastate is generated from the summation of at least 200 component Linear (Airy) waves of height and frequency determined to match the required wave spectrum. The phasing of the component waves should be selected at random. The extrapolation of the wave kinematics to the free surface is most appropriately carried out by substituting the true elevation at which the kinematics are required with one which is at the same proportion of the still water depth as the true elevation is of the instantaneous water depth. This can be expressed as follows: z' = z d − + ζ 1 ζ / where; z' = The modified coordinate to be used in particle velocity formulation z = The elevation at which the kinematics are required (coordinate measured vertically upward from the still water surface) ζ = The instantaneous water level (same axis system as z) d = The still, or undisturbed water depth (positive). This method ensures that the kinematics at the surface are always evaluated from the linear wave theory expressions as if they were at the still water level, Wheeler (1969) [4] (see Figure C4.4.2 in the Commentary). 4.4.3 If breaking waves are specified according to Figure 4.1, it is recommended that the wave period is changed to comply with the breaking limit for the specified height. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 32 Rev 3, August 2008 Notes 1) None of these theories is theoretically correct at the breaking limit. Nomenclature 2) Wave theories intended for limiting height waves should be referenced for waves higher than 0.9Hb when stream function theory may underestimate the kinematics. Hmax/gTass 2 = Dimensionless wave steepness 3) Stream function theory is satisfactory for wave loading calculations over the remaining range of regular waves. However, stream function programs may not produce a solution when applied to near breaking waves or deep water waves d/gTass 2 = Dimensionless relative depth Hmax = Wave height (crest to trough) Hb = Breaking wave height d = Mean water depth 4) The order of stream function theory likely to be satisfactory is circled. Any solution obtained should be checked by comparison with the results of a higher order solution. Tass = Wave period L = Wave length (distance between crests) 5) The error involved in using Airy theory outside its range of applicability is discussed in the background document. g = Acceleration due to gravity Figure 4.1 - Range and validity of different wave theories for regular waves, (after HSE [3]) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 33 Rev 3, August 2008 4.5 Current 4.5.1 The current velocity and profile as specified in Section 3.6 shall be used. Interpolation between the data points may be required and linear interpolation is recommended for simplicity. 4.5.2 The current induced drag forces are to be determined in combination with the wave forces. This is to be carried out by the vectorial addition of the wave and current induced particle velocities prior to the drag force calculations. 4.5.3 The current may be reduced due to interference from the structure on the flow field of the current, Taylor [5]. The current may be reduced as follows (see Commentary): VC = Vf [1 + CDeDe/(4D1)]-1 where; VC = the current velocity to be used in the hydrodynamic model, VC should be not taken as less than 0.7Vf. Vf = the far field (undisturbed) current. CDe = equivalent drag coefficient, as defined in 4.6.5. De = equivalent diameter, as defined in 4.6.5. D1 = face width of leg, outside dimensions. 4.6 Leg Hydrodynamic Model 4.6.1 The hydrodynamic modeling of the jack-up leg may be carried out by utilizing 'detailed' or 'equivalent' techniques. In both cases the geometric modeling procedure corresponds to the respective modeling techniques described in Section 5.6.4. The hydrodynamic properties are then found as described below: 'Detailed' model All relevant members are modeled with their own unique descriptions for the Morison term values with the correct orientation to determine vn and 􀀅u n and the corresponding CDD = CDiDi and CMA = CMiπDi 2/4, as defined in Section 4.7. 'Equivalent' model The hydrodynamic model of a bay is comprised of one, 'equivalent' vertical tubular located at the geometric center of the actual leg. The corresponding (horizontal) vn and 􀀅u n are applied together with equivalent CDD = CDeDe and CMA = CMeAe, as defined in Sections 4.6.5 and 4.6.6. The model should be varied with elevation, as necessary, to account for changes in dimensions, marine growth thickness, etc. Note: The drag properties of some chords will differ for flow in the direction of the wave propagation (wave crest) and for flow back towards the source of the waves (wave trough). Often the combined drag properties of all the chords on a leg will give a total which is independent of the flow direction along a particular axis. When this is not the case it is recommended that the effect is included directly in the wave-current loading model. If this is not possible it is recommended that: COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 34 Rev 3, August 2008 1. Regular wave deterministic calculations use a value appropriate to the flow direction under consideration, noting that the flow direction is that of the combined wave and current particle motion. 2. An average drag property is considered for random wave analyses which are solely used to determine dynamic effects for inclusion in a final regular wave deterministic calculation which will be made on the basis of 1. above. 3. The drag property in the direction of wave propagation is used for random wave analyses from which the final results are obtained directly. 4.6.2 Lengths of members are normally taken as the node-to-node distance of the members in order to account for small non-structural items (e.g. anodes, jetting lines of less than 4" nominal diameter). Large non-structural items such as raw water pipes and ladders are to be included in the model. Free standing conductor pipes and raw water towers are to be considered separately from the leg hydrodynamic model. 4.6.3 The contribution of the part of the spudcan above the seabed should be investigated and only excluded from the model if it is shown to be insignificant. In water depths greater than 2.5 Hs or where penetrations exceed 1/2 the spudcan height, the effect of the spudcan is normally insignificant. 4.6.4 For leg structural members, shielding and solidification effects should not normally be applied in calculating wave forces. The current flow is however reduced due to interference from the structure on the flow field, see Section 4.5.3. 4.6.5 When the hydrodynamic properties of a lattice leg are idealized by an 'equivalent' model description the model properties may be found using the method given below: The equivalent value of the drag coefficient, CDe, times the equivalent diameter, De, to be used in Section 4.3.2 for CDei of the bay may be chosen as: CDe De = De Σ CDei The equivalent value of the drag coefficient for each member, CDei, is determined from: CDei = [ sin2βi + cos2βi sin2αi ]3/2 CDi D D s i i e 1 where; CDi = drag coefficient of an individual member (i) as defined in Section 4.7. Di = reference diameter of member 'i' (including marine growth as applicable) as defined in Section 4.7. De = equivalent diameter of leg, suggested as (Σ D l / s i i 2 li = length of member 'i' node to node center. s = length of one bay, or part of bay considered. αi = angle between flow direction and member axis projected onto a horizontal plane. βi = angle defining the member inclination from horizontal (see Figure 4.2). Note: Σ indicates summation over all members in one leg bay COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 35 Rev 3, August 2008 The above expression for CDei may be simplified for horizontal and vertical members as follows: Vertical members (e.g. chords): CDei = CDi (Di/De) Horizontal members: CDei = sin3α CDi (Dili/Des) Figure 4.2: Flow angles appropriate to a lattice leg (after DNV Class Note 31.5, February 1992, [6]) 4.6.6 The equivalent value of the inertia coefficient, CMe, and the equivalent area, Ae, to be used in Section 4.3.3, representing the bay may be chosen as: CMe = equivalent inertia coefficient which may normally be taken as 2.0 when using Ae Ae = equivalent area of leg per unit height = (ΣAili)/s Ai = equivalent area of element = πDi 2/4 Di = reference diameter chosen as defined in Section 4.7 For a more accurate model the CMe coefficient may be determined as: CMe Ae = Ae Σ CMei where; CMei = [1 + (sin2βi + cos2βi sin2αi)(CMi - 1)] A l A s i i e CMi = the inertia coefficient of an individual member, CMi is defined in Section 4.7 related to reference dimension Di. Note: For dynamic modeling the added mass of fluid per unit height of leg may be determined as ρAi(Cmi - 1) for a single member or ρAe(CMe - 1) for the equivalent model, provided that Ae is as defined above. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 36 Rev 3, August 2008 4.7 Hydrodynamic Coefficients for Leg Members 4.7.1 Hydrodynamic coefficients for leg members are given in this Section. Tubulars, brackets, split tube and triangular chords are considered. Hydrodynamic coefficients including directional dependence are given together with a fixed reference diameter Di. No other diameter should be used unless the coefficients are scaled accordingly. Unless better information is available for the computation of wave and current forces, the values of drag and inertia coefficients applicable to Morison's equation should be obtained from this Section. 4.7.2 Recommended values for hydrodynamic coefficients for tubulars (<1.5m diameter) are given in Table 4.3 based on the data discussed in the commentary. Surface condition CDi CMi Smooth Rough See Note ⎫⎬ ⎪ ⎭⎪ 0.65 1.00 2.0 1.8 Table 4.3: Base hydrodynamic coefficients for tubulars Note: The smooth values will normally apply above MWL + 2m and the rough values below MWL + 2m, where MWL is as defined in Section 3.7.2. If the jack-up has operated in deeper water and the fouled legs are not cleaned the surface should be taken as rough for wave loads above MWL + 2m. See Commentary. 4.7.3 When applicable, marine growth is to be included in the hydrodynamic model by adding the appropriate marine growth thickness, to, on the boundary of each individual member below MWL + 2m where MWL is as defined in Section 3.7.2 i.e. for a tubular Di = Doriginal + 2tm. Site specific data for marine growth is preferred (see Section 3.9). If such data are not available all members below MWL + 2m shall be considered to have a marine growth thickness tm = 12.5 mm (i.e. total of 25 mm across the diameter of a tubular member). Marine growth on the teeth of elevating racks and protruding guided surfaces of chords may normally be ignored. The effects of marine growth may be ignored if anti-fouling, cleaning or other means are applied, however the surface roughness is still to be taken into account (see Commentary). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 37 Rev 3, August 2008 4.7.4 The in-line force due to gussets in any vertical plane shall be determined using a drag coefficient: CDi = 2.0 applied together with the projected area of the gusset visible in the flow direction, unless model test data shows otherwise. This drag coefficient may be applied together with a reference diameter Di and corresponding length li chosen such that their product equals the plane area, A = Dili and Di = li (see Figure 4.3). In the equivalent model of Section 4.6 the gussets may then be treated as a horizontal element of length li , with its axis in the plane of the gusset. CMi should be taken as 1.0 and marine growth may be ignored. Figure 4.3: Gusset plates COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 38 Rev 3, August 2008 4.7.5 For non-tubular geometries (e.g. leg chords) the appropriate hydrodynamic coefficients may, in lieu of more detailed information, be taken in accordance with Figures 4.4 or 4.5 and corresponding formulas, as appropriate. Figure 4.4: Split tube chord and typical values for CDi For a split tube chord as shown in Figure 4.4, the drag coefficient CDi related to the reference dimension Di = D+2tm, the diameter of the tubular including marine growth as in Section 4.7.3, may be taken as: CDi = C C CWD C Sin D D D i D 0 0 1 0 2 0 20 20 9 7 20 90 ; ( / ) [( )/] ; ° < ≤ ° + − − ° ° < ≤ ° ⎧ ⎨ ⎪ ⎩ ⎪ θ θ θ where; θ = Angle in degrees, see Figure 4.4 CD0 = The drag coefficient for a tubular with appropriate roughness, see Section 4.7.2. (CD0 = 1.0 below MWL+2m and CD0 =0.65 above MWL+2m.) CD1 = The drag coefficient for flow normal to the rack (θ = 90°), related to projected diameter, W. CD1 is given by: CD1 = 18 12 14 12 18 20 18 1 3 . ; / . . ( / ) ; . / . . ; . / W D W D W D W D i i i i < + < < < ⎧⎨ ⎪ ⎩⎪ The inertia coefficient CMi = 2.0, related to the equivalent volume πDi 2/4 per unit length of member, may be applied for all heading angles and any roughness. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 39 Rev 3, August 2008 Figure 4.5: Triangular chord and typical values of CDi For a triangular chord as shown in Figure 4.5, the drag coefficient CDi related to the reference dimension Di = D, the backplate width, may be taken as: CDi = CDpr(θ) Dpr(θ) / Di where the drag coefficient related to the projected diameter, CDpr, is determined from: CDpr = 170 0 195 90 140 105 165 180 2 00 180 . ; . ; . ; . ; . ; θθθ θ θ θ = ° = ° = ° = °− = ° ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ o Linear interpolation is to be applied for intermediate headings. The projected diameter, Dpr(θ), may be determined from: Dpr(θ) = D W D D o o o o cos( ) ; sin( ) . θ θ θ θ θ θ θ θ θ θ θ 0 0 5 180 180 < < + < < − < < ⎧⎨ ⎪ ⎩⎪ |cos( )| ; |cos( )| ; 180 - The angle θo, where half the rackplate is hidden, θo = tan-1(D/(2W)). The inertia coefficient CMi = 2.0 (as for a flat plate), related to the equivalent volume of πDi 2/4 per unit length of member, may be applied for all headings and any roughness. 4.7.6 Shapes, combinations of shapes or closely grouped non-structural items which do not readily fall into the above categories should be assessed from relevant literature (references to be provided) and/or appropriate interpretation of (model) tests. The model tests should consider possible roughness, Keulegan-Carpenter and Reynolds number dependence. 4.8 Other Considerations Local load effects will normally have been addressed at the design stage. Should the wind or current and/or wave height parameters at the location exceed those applicable at the design stage further consideration may be required. The Commentary provides further details and references to calculation methods. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 40 Rev 3, August 2008 4 GLOSSARY OF TERMS - CALCULATION METHODS HYDRODYNAMICS AND WIND FORCES AWi = Projected area of the block considered in wind computations. A = Cross sectional area of member. Ae = Equivalent area of leg per unit height = (Σ Ai 1i )/s. Ai = Equivalent area of element = π Di 2 /4. CD = Drag coefficient. CDe = Equivalent drag coefficient. CDi = Drag coefficient of an individual member, related to Di. CD0 = The drag coefficient for chord at direction θ = 0°. CD1 = The drag coefficient for flow normal to the rack, θ = 90°. CDpr = The drag coefficient related to the projected diameter. CM = Inertia coefficient. CMe = Equivalent inertia coefficient. CMi = Inertia coefficient of a member, related to Di. Ch = Height coefficient for wind. Cs = Shape coefficient for wind related to projected area. d = The mean, undisturbed water depth (positive). D = Member diameter or backplate width. De = Equivalent diameter of leg. Di = Reference dimension of individual leg members. D1 = Face width of leg, outside dimensions. Dpr = The projected diameter. FWi = Wind force for block i. Hs = The effective significant wave height (Section 5.5.1.3). li = Length of member 'i' node to node center. Pi = Wind pressure at the center of block i. 􀀅r n = Velocity of the considered member, normal to the member axis and in the direction of the combined particle velocity. s = Length of one bay, or part of bay considered. tm = Marine growth thickness. Tn = First natural period of sway motion. Tz = The zero-upcrossing period associated with Hs. u = Wave particle velocity. un = Wave (only) particle velocity normal to the member. 􀀅u n = Wave particle acceleration normal to the member. vn = Total (relative) flow velocity normal to the member. VCn = Current velocity to be used in the hydrodynamic model, normal to member. Vf = Far field (undisturbed) current. Vref = One minute sustained wind velocity at elevation Zref. VZ = Wind velocity at elevation Z. W = Dimension from backplate to pitch point of triangular chord or dimension from root of one rack to tip of other rack of split-tubular chord. z = Coordinate measured vertically upward from the mean water surface. z' = Modified coordinate to be used in particle velocity formulation. Z = Elevation measured from the mean water surface. Zref = Reference elevation for wind speed. α = Indicator for relative velocity, 0 or 1. αi = Angle defining flow direction relative to member. βi = Angle defining the member inclination. ΔFdrag = Drag force per unit length. ΔFinertia = Inertia force per unit length. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 41 Rev 3, August 2008 4 GLOSSARY OF TERMS - CALCULATION METHODS HYDRODYNAMICS AND WIND FORCES (Continued) ζ = The instantaneous water surface elevation (same axis system as z). ρ = Mass density of water or air. θ = Angle in degrees of water particle velocity relative to the chord orientation. θo = Angle at which half rackplate of Δ chord is hidden = tan-1 (D/(2W)) λ = Wave length. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 42 Rev 3, August 2008 5 CALCULATION METHODS - STRUCTURAL ENGINEERING 5.1 General Conditions 5.1.1 Structural calculations should be carried out in accordance with the following sections. 5.1.2 A range of environmental approach directions and storm water levels should be considered, such that the most onerous (i.e. that leading to the extreme maximum and/or minimum loading) is determined for each assessment check {strength of each major type of element (chord, brace, etc.), overturning stability, foundation capacity, horizontal deflections, holding system, etc.}. 5.1.3 In deterministic calculations the most critical wave phase position(s) should be considered for each case identified under 5.1.2. Normally the phase giving maximum base shear and/or overturning moment will be found critical for overturning, leeward leg stresses, leeward leg foundations and windward leg foundations. 5.1.4 For fatigue calculations it may be necessary to determine the load or stress ranges, and hence other phase positions may also need to be considered. 5.2 Seabed Reaction Point For independent leg jack-up units, the reaction point for horizontal and vertical loads at each footing shall be situated on the geometric vertical axis of the leg/spudcan, at a distance above the spudcan tip equivalent to: a) Half the maximum predicted penetration (when spudcan is partially penetrated), or b) Half the height of the spudcan (when the spudcan is fully, more than fully penetrated). If detailed information exists regarding the soils and spudcan the position of the reaction point may be calculated. (Brekke et al, [7]) 5.3 Foundation Fixity 5.3.1 For analyses of an independent leg jack-up unit under extreme storm conditions the foundations may normally be assumed to behave as pin joints, and so are unable to sustain a bending moment. Analysis and practical experience suggest that this may be a conservative approach for bending moment in the upper parts of the leg in way of the lower guides. 5.3.2 In cases where the inclusion of rotational foundation fixity is justified and is included in the structural analysis, it is essential that the nonlinear soil-structure interaction effects are properly taken into account. The model should include the interaction of rotational, lateral and vertical soil forces. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 43 Rev 3, August 2008 5.3.3 Methods of establishing the degree of fixity of rotational restraint, or fixity, at the footings are discussed further in Section 6.3.4 and the Commentary to Section 6. Upper or lower bound values should be considered as appropriate for the areas of the structure under consideration. 5.3.4 For checking the spudcans, the leg-to-can connection and the lower parts of the leg, appropriate calculations considering soil-structure interaction shall be carried out to determine the upper bound can moment. These areas may be checked assuming that a percentage of the maximum storm leg moment at the lower guide (derived assuming a pinned footing) is applied to the spudcan together with the associated horizontal and vertical loads. This percentage would normally be not less than 50%. For such simplified checks the loading on the spudcan may be modeled assuming that the soil is linear-elastic and incapable of taking tension. 5.4 Leg Inclination The effects of initial leg inclination should be considered. Leg inclination may occur due to leg-hull clearances and the hull inclination permitted by the operating manual. Thus the total horizontal offset due to leg inclination, OT, may be determined as: OT = O1 + O2 where; OT = Total horizontal offset of leg base with respect to hull. O1 = Offset due to leg-hull clearances. O2 = Offset due to maximum hull inclination permitted by the operating manual. If detailed information is not available, OT should be taken as 0.5% of the leg length below the lower guide. The effects of leg inclination need be accounted for only in structural strength checks. This will normally be accomplished by increasing the effective moment in the leg at the lower guide by an amount equal to the offset OT times the factored vertical reaction at the leg base due to dead, live, environmental, inertial and P-Δ loads. 5.5 P-Δ Effects 5.5.1 The P-Δ Effect occurs because the jack-up is a relatively flexible structure and is subject to lateral displacement of the hull (sidesway) under the action of environmental loads. As a result of the hull translation the line of action of the vertical spudcan reaction no longer passes through the centroid of the leg at the level of the hull. Consequently the leg moments at the level of the hull are increased over those arising from a linear quasi- static analysis by an amount equal to the individual leg load P times the hull translation, D. This additional moment will cause additional deflection over that predicted by standard linear-elastic theory. The increased deflection is a function of the ratio of the applied axial load to the Euler load. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 44 Rev 3, August 2008 Furthermore the shift in the hull center of gravity due to the hull translation will increase the overturning moment (or decrease the righting moment). Consequently the axial loads in the leeward leg(s) will increase and the axial loads in the windward leg(s) will reduce. The consequences of the above are: a) Increased hull deflections (which will increase the linear-elastic P-Δ moments). b) A redistribution of base shears (in global axes) such that the increase in lower guide moment is reduced in the leeward leg(s) and increased in the windward leg(s). 5.5.2 An analysis using a standard linear elastic (small displacement) finite element program will not allow for these effects. The following Sections describe techniques which may be used to account for the P-Δ/Euler effects. The large displacement methods are the most accurate, but require more rigorous analysis. The geometric stiffness methods are simpler and generally of sufficient accuracy. 5.5.3 Large displacement methods; These methods are part of a number of finite element (F.E.) programs. In such methods the non-linear (large-displacement) solution is obtained by applying the load in increments and iteratively generating the stiffness matrix for the next load increment from the deflected shape (nodal deflections) of the previous increment. Some F.E. programs offer an intermediate solution in which the deflected geometry from an initial linear- elastic solution is used as the input to the final 'corrected' solution. 5.5.4 Geometric stiffness methods; 5.5.4.1 These methods are also available within a number of F.E. programs. A linear correction is made to the element stiffness matrix based on the axial load present in the element. Iteration is also required for this solution procedure. 5.5.4.2 A simplified geometric stiffness approach allows incorporation of P-Δ effects in a standard linear-elastic F.E. program without recourse to iteration (refer to Commentary for derivation). In this approach a correction term is introduced into the global stiffness matrix prior to analysis. When the analysis is complete the hull deflections, leg axial loads and leg bending moments will include the P-Δ effects. The derivation of the method is described in appendix C5.A of the Commentary. The correction term is: -Pg/L where; Pg = Total effective gravity load on legs at hull. This includes the hull weight and weight of the legs above the hull. L = The distance from the spudcan reaction point to the hull vertical center of gravity. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 45 Rev 3, August 2008 This single (negative) value is incorporated into the global stiffness matrix by attaching a pair of orthogonal horizontal translational earthed spring elements to a node representing the hull center of gravity and entering the negative value for each of the spring constants. Some F.E. packages allow direct matrix manipulation. The negative stiffness term at the hull will produce an additional lateral force at the hull proportional to the structural deflection. The resulting (additional) base overturning moment will be equal to the gravity load times the hull displacement. The additional lateral load (due to the negative stiffness term) will cause an overprediction of the base shear (in global axes). Typically this is not critical. However, the base shear at each leg can be reduced by an amount equal to the difference between the total base shear and the shear due to the applied loads (both in global axes) divided by the number of legs. 5.5.4.3 An alternative geometric stiffness approach is given below. Here the P-Δ effects are determined by amplifying the linear-elastic displacement (excluding P-Δ) as follows: Δ = δs / (1 - P PE ) where; Δ = the approximate displacement including P-Δ. δs = the linear-elastic first order hull displacement. P = the average axial load in the leg at the hull (i.e. the total leg load at the hull divided by the number of legs). PE = Euler buckling load of an individual leg.(See Section 7.3.5 for general formulation). Corrections can then be made to a global linear-elastic solution by manually adding P-Δ moments to the results. The P-Δ moments are computed using the amplified deflection, Δ, and P's adjusted to account for this. (This approach is not strictly valid because it ignores the fact that the deflection of all the legs at the hull must be approximately equal. The imposition of this constraint will lead to a redistribution of the global base shear between the legs.) Ignoring the redistribution will generally be conservative for leeward leg(s) and their foundation loads and non- conservative for windward leg(s) and their foundation loads. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 46 Rev 3, August 2008 5.6 Structural Modeling 5.6.1 Introduction It is important that the structural model accurately reflects the complex mechanism of the jackup. For most jack-up configurations the load distribution at the leg-hull interface is not amenable to manual calculation, therefore, it is necessary to develop a Finite Element (F.E.) computer model. A number of different modeling techniques can be used to depict the jack-up structure. The recommended techniques are summarized below and their applicability and limitations are discussed in more detail in Section 5.6.3. a) Fully detailed model of legs and hull/leg connections with detailed or representative stiffness model of hull and spudcan. b) Simplified lower legs and spudcans, detailed upper legs and hull/leg connections with detailed or representative stiffness model of hull. c) Equivalent stiffness model of legs and spudcans, equivalent hull/leg connection springs and representative beam-element hull grillage. d) Detailed leg (or leg section) and hull/leg connection model. Section 5.6.3 and Table 5.1 outline the limitations of the various modeling techniques and should be referenced to ensure that the selected models address all aspects required for a specific assessment. 5.6.2 General Considerations In the elevated condition the most heavily loaded portion of the leg is normally between the upper and lower guides and in way of the lower guide. The stress levels in this area depend on the design concept of the jack-up. A specific jack-up design concept can be described by the combination of the following components (see Commentary Figure C5.5): a) With or without fixation system, b) Fixed or floating jacking system, c) Opposed or unopposed pinions. In units having fixation systems the transfer of moment between the leg and the hull is largely by means of a couple due to vertical loads carried from the chord into the fixation or jacking system. Where a fixed or floating jacking system is fitted (and there is no fixation system) the transfer of moment between the leg and the hull is partly by means of a couple due to horizontal loads carried from the chords into the upper and lower guides. In this case and when the chord/guide contact occurs between bracing nodes significant local chord bending moments are normal. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 47 Rev 3, August 2008 If the jacking system has unopposed pinions local chord moments will arise due to: - the horizontal pinion load component (due to the pressure angle of the rack/pinion). - the vertical pinion load component acting at an offset from the chord neutral axis. The modeling of the various design aspects is critical and recommended modeling techniques are outlined in the following sections. The Commentary provides detailed information regarding the combination of the above three components for current jack-up units. 5.6.3 Applicability and Limitations It is most desirable to fully model the jack-up when assessing its structural strength. Very often assumptions and simplifications such as equivalent hull, equivalent leg, etc. will be made in the process of building the model. In view of this, various levels of modeling described in a) through d) below may be used. It should be noted that some of these methods may have limitations with respect to the accuracy of assessing the structural adequacy of a jack-up and when simplified models, such as those described in (c) and (d) are used it may be appropriate to calibrate against a more detailed model. a) Fully detailed 3-leg model The model consists of 'detailed legs', hull, hull/leg connections and spudcans modeled in accordance with 5.6.4(a),5.6.5, 5.6.6 and 5.6.7, respectively. The results from this model can be used to examine the preload requirements, overturning resistance, leg strength and the adequacy of the jacking system or fixation system. b) Combination leg 3-leg model The model consists of a combination of 'detailed leg' for the upper portion of legs and 'equivalent leg' for the lower portion of the legs modeled in accordance with 5.6.4. The hull, hull/leg connections and spudcans are modeled in accordance with 5.6.5, 5.6.6 and 5.6.7 respectively. The results from this model can be used to examine the preload requirements, overturning resistance, leg strength and the adequacy of the jacking system or fixation system. c) Equivalent 3-stick-leg model The model consists of 'equivalent legs' modeled in accordance with 5.6.4(b), hull structure modeled using beam elements in accordance with 5.6.5, leg to hull connections modeled in accordance with 5.6.6 and spudcans modeled as a stiff or rigid extension to the equivalent leg. The results from this model can be used to examine the preload requirements and overturning resistance. This model may also used to obtain the reactions at the spudcan or internal forces and moments in the leg at the vicinity of lower guide for application to the 'detailed leg' and hull/leg model (d) which should be used to assess the strength of the leg in the area between lower and upper guides. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 48 Rev 3, August 2008 d) Single detailed leg model The model consists of a 'detailed leg' or a portion of a 'detailed leg' modeled in accordance with 5.6.4(a), the hull/leg connection modeled in accordance with 5.6.6 and, when required, the spudcan modeled in accordance with Section 5.6.7. This model is to be used in conjunction with the reactions at the spudcan or the forces and moments in the vicinity of lower guide obtained from Model (c). The results from this model can be used to examine the leg strength and the adequacy of the jacking system or the fixation system. Applicability (see Note 1) Model Type I Global Loads II Overturning Checks III Foundation Checks IV Global Leg Loads V Leg Member Loads VI Pinion/ Fixation System Loads VII Hull Element Loads a Y Y Y Y Y Y 2 b Y Y Y Y Y Y 2 c Y Y Y Y - - - d - - - - Y Y - Legend: Y = Applicable - = Not applicable Notes: 1. Large displacement and dynamic effects to be included where appropriate. 2. VII, hull stresses will only be available from more complex hull models. Table 5.1 - Applicability of the suggested models 5.6.4 Modeling the Leg The leg can be modeled as a 'detailed leg', an 'equivalent leg' or a combination of the two. The 'detailed leg' model consists of all structural members such as chords, horizontal, diagonal and internal braces of the leg structure and the spudcan (if required). The 'equivalent leg' model consists of a series of colinear beam elements (stick model) simulating the complete leg structure. It is recommended that the leg model(s) be generated in accordance with the following: a) 'Detailed Leg' Model The coordinates of the joints for this model are to be defined by the intersection of the chord and brace centerlines. For joints where there is more than one brace, it is unlikely that there will be one (1) common point of intersection between the braces and chord. In this instance, it is usually sufficient to choose an intermediate point between the chord/brace centerline intersections. Gusset plates normally need not be included in the structural leg model, however their effects may be taken into account in the calculation of member and joint strength checks. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 49 Rev 3, August 2008 b) 'Equivalent Leg' Model The leg structure can be simulated by a series of colinear beams with the equivalent cross sectional properties calculated using the formulas indicated in Figure 5.1 or derived from the application of suitable 'unit' load cases (see Commentary C5.5) to the 'Detailed Leg' model described in 5.6.4 (a). Where such a model is used, detailed stresses, pinion loads, etc. will be derived either directly or indirectly from a 'detailed model'. c) 'Combination Leg' model To facilitate obtaining detailed stress, pinion loads, etc. directly, a 'detailed leg' model can be generated covering the region between the guides, and extending at least 4 bays below and, where available, at least 4 bays above this region. The remainder is then modeled as an 'equivalent leg'. Care is required to ensure an appropriate interface and consistency of boundary conditions at the connections. The 'detailed leg'/'equivalent leg' connection should be modeled so that the plane of connection remains a plane after the leg is bent. Note: The leg stiffness used in the overall response analysis may account for a contribution from a portion of the rack tooth material. Unless detailed calculations indicate otherwise, the assumed effective area of the rack teeth should not exceed 10% of their maximum cross sectional area. When checking the capacity of the chords the chord properties should be determined discounting the rack teeth. 5.6.5 Modeling the Hull The hull structure should be modeled so that the loads can be correctly transferred to the legs and the hull flexibility is represented accurately. Recommended methods are given below: a) Detailed Hull Model The model can be generated using plate elements in which appropriate directional modeling of the effect of the stiffeners on the plates should be included. The elements should be capable of carrying in-plane and, where applicable, out-of plane loads. b) Equivalent Hull Model Alternatively, the hull can be modeled by using a grillage of beams. Deck, bottom, side shell and bulkheads can be used to construct the grillage. The properties of the beam can be calculated based on the depth of the bulkheads, side-shell and the 'effective width' of the deck and bottom plating. Attention should be paid to the inplane and torsional properties due to the continuity of the deck and bottom structures. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 50 Rev 3, August 2008 5.6.6 Modeling the Hull/Leg Connection The hull/leg connection modeling is of extreme importance to the analysis since it controls the distribution of leg bending moments and shears carried between the upper and lower guide structures and the jacking or fixation system. It is therefore necessary that these systems are properly modeled in terms of stiffness, orientation and clearance. For the 'Equivalent 3-stick-leg model' a simplified derivation of the equivalent leg-hull connection stiffness may be applicable. For jack-ups with a fixation system, the leg bending moment will be shared by the upper and lower guides, the jacking and the fixation systems. Normally the leg bending moment and axial force due to environmental loading are resisted largely by the fixation system because of its high rigidity. Depending on the specified method of operation, the stiffnesses, the initial clearances and the magnitude of the applied loading a portion of the environmental leg loading may be resisted by the jacking system and the guide structures. Typical shear force and bending moment diagrams for this configuration are shown in Figure 5.2. For jack-ups without a fixation system, the leg bending moment will be shared by the jacking system and guide structure. For a fixed jacking system, the distribution of leg moment carried between the jacking system and guide structure mainly depends on the stiffness of the jacking pinions. Typical shear force and bending moment diagrams for this design are shown in Figures 5.3 and 5.4. For a floating jacking system, the distribution of leg bending moment carried between the jacking system and guide structure depends on the combined stiffness of the shock pads and pinions. Typical shear force and bending moment diagrams for this design are shown in Figure 5.5. The hull/leg connection should be modeled considering the effects of guide and support system clearances, wear, construction tolerances and backlash (within the gear-train and between the drive pinion and the rack). The following techniques are recommended for modeling hull/leg connections (specific data for the various parts of the structure may be available from the designers data package): Detailed modeling a) Upper and Lower Guides - The guide structures should be modeled to restrain the chord member horizontally only in directions in which guide contact occurs. The upper and lower guides may be considered to be relatively stiff with respect to the adjacent structure, such as jackcase, etc. The nominal lower guide position relative to the leg may be derived using the sum of leg penetration, water depth and airgap. It is however recommended that at least two positions are covered when assessing leg strength: one at a node and the other at the midspan. This is to allow for uncertainties in the prediction of leg penetration and possible differences in penetration between the legs. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 51 Rev 3, August 2008 The finite lengths of the guides may be included in the modeling by means of a number of discrete restraint springs/connections to the hull. Care is required to ensure that such restraints carry loads only in directions/senses in which they can act. Alternatively the results from analyses ignoring the guide length may be corrected, if necessary, by modification of the local bending moment diagram to allow for the proper distribution of guide reaction, see Figure 5.6. b) Jacking Pinions - The jacking pinions should be modeled based on the pinion stiffness specified by the manufacturer and should be modeled so that the pinions can resist vertical and the corresponding horizontal forces. A linear spring or cantilever beam can be used to simulate the jacking pinion. The force required to deflect the free end of the cantilever beam a unit distance should be equal to the jacking pinion stiffness specified by the manufacturer. The offset of the pinion/rack contact point from the chord neutral axis should be incorporated in the model. c) Fixation System - The fixation system should be modeled to resist both vertical and horizontal forces based on the stiffness of the vertical and horizontal supports and on the relative location of their associated foundations. It is important that the model can simulate the local moment capacity of the fixation system arising from its finite size and the number and location of the supports. d) Shock Pad - Floating jacking systems generally have two sets of shock pads at each jackcase, one located at the top and the other at the bottom of the jackhouse. Alternatively shock pads may be provided for each pinion. The jacking system is free to move up or down until it contacts the upper or lower shock pad. In the elevated condition, the jacking system is in contact with the upper shock pad and in the transit condition it is in contact with the lower shock pad. The stiffness of the shock pad should be based on the manufacturer's data and the shock pad should be modeled to resist vertical force only. It should also be noted that the shock pad stiffness characteristics may be nonlinear. e) Jackcase and associated bracing - The jackcase and associated bracing should be modeled based on the actual stiffness since it has direct impact on the horizontal forces that the upper guide can resist. Note: Where the hull is not modeled it is normally suitable to earth the base of the jackcase and associated bracing, the foundations of the fixation system and the lower guide structures at their connections to the hull. Simple modeling f) For applications such as those described in Section 5.6.3 c) (Equivalent 3-stick-leg model) a simplified representation of the hull to leg connection is required. In this instance the rotational stiffness may be represented by rotational springs and, where applicable, horizontal and vertical stiffnesses by linear springs. Where these are derived from a more detailed modeling, as described above, it is important that suitable loading levels (typical of the cases to be analyzed) are selected so that the effects of clearances, etc. do not dominate the result. Hand calculations may also be applicable. See Section C5.5 in the Commentary. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 52 Rev 3, August 2008 5.6.7 Modeling the Spudcan When modeling the spudcan, rigid beam elements are considered sufficient to achieve an accurate load transfer of the seabed reaction into the leg chords and bracing in the area between upper and lower guides. It should be noted that, due to the sudden change in stiffness, rigid beams can cause artificially high stresses at the leg to spudcan connections. Hence the modeling and selection of element type should be carefully considered when an accurate calculation of chord stresses is required in this area. For a strength analysis of the spudcan and its connections to the leg it may be appropriate to develop a separate detailed model with appropriate boundary conditions. 5.7 Load Application The assessment follows a partial factor format. The partial load factors are applied to loads as defined in other sections (i.e. they are load factors, NOT load-effect factors). The jack-up response is non-linear, and hence the application of the combined factored loads will not in general develop the same result as the factored combination of individual load effects. For typical jack-up assessments, the time-varying nature of the wave loading will amplify the static responses and must be considered. The extreme response can be assessed either by a quasi-static analysis procedure (Section 7.2) including an inertial loadset (Section 7.3.6) or by a more detailed dynamic analysis procedure (Section 7.3.7). In the former case (quasi-static analysis including an inertial loadset), the load factors should be directly applied to the appropriate combinations of quasi-static environmental loading and inertial loadsets. In the latter case (detailed dynamic analysis), alternative methods can be used when acceptable rationale is provided. The loads and load effects to be included in the analysis, with their designators used in Section 8 in ( ), comprise: a) Self weight and non-varying loads (D), variable and drilling loads (L). b) Wind loads (E). c) Hydrodynamic wave-current loads (E). d) Inertial loads due to dynamic response (Dn). e) Second order effects (associated with D,L,E & Dn). These are discussed in turn below. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 53 Rev 3, August 2008 5.7.1 Self weight, variable and drilling loads Depending on the initial positions of the legs with respect to guide clearances, and the operation of the jacking and fixation systems (if fitted), the distributed hull loading and stiffness will lead to hull sagging which may impose bending moments on the legs which remain present for the remainder of the period on location. Such moments should be considered in the site assessment analyses, and will be larger in shallow waters where the leg extension below the hull is small and consequently the leg bending stiffness is higher. To correctly capture these effects the hull loads should be applied to the model in such a manner as to represent their correct vertical and horizontal distribution. If dynamic analyses are to be performed all weights should be represented by means of masses together with vertical gravitational acceleration. It is generally appropriate to apply these masses by means of factored element self-weight with additional correction masses applied as necessary to obtain the correct total mass and center of gravity. Alternatively, it may be sufficient to apply point masses at the node points of the model. It is noted that an F.E. model with distributed hull stiffness and loading will incorporate hull sag effects if the hull and variable gravity loading is 'turned on' with the unit defined in its initially undeflected shape at the operating airgap. It should be verified that the amount of hull sag moment arising is applicable, given the operating procedures pertaining to the unit. It may be necessary to apply corrections to the final results for any discrepancies in the hull sag induced loadings. Further guidance is given in Section 5.3.3 of the Commentary. 5.7.2 Wind loads The wind loading on the legs above and below the hull may be applied as distributed or nodal loads. Where nodal loads are used a sufficient number of loads should be applied to reflect the distributed nature of the loading and it should be ensured that the correct total shear and overturning moment is applied on each leg. Similarly the wind loading on the hull and associated structure may be applied as distributed or nodal loads. The application should ensure the correct total shear and overturning moment is applied to the hull. 5.7.3 Hydrodynamic wave-current loads The wave-current loading on the leg and spudcan structures above the mudline may be applied as distributed or nodal loads. Where nodal loads are used the application should ensure the correct total shear and overturning moment on each leg, and reflect the distributed nature of the loading. 5.7.4 Inertial loads due to dynamic response When the dynamic approach (see Section 7) leads to the explicit determination of an inertial loadset, this should be applied to the hull model. In simpler dynamic approaches the inertial load may be represented by a single lateral point loading acting at the hull center of gravity, or by a number of point loads applied to other parts of the hull having the same line of action. In more complex approaches a more complete distributed load vector may be applied to the hull and legs. 5.7.5 Second order effects Methods for including P-Δ effects are described in Section 5.5. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 54 Rev 3, August 2008 Figure 5.1: Formulas for the determination of equivalent member properties;(After DNV Class Note 31.5 1992 [6] (corrected) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 55 Rev 3, August 2008 Figure 5.2: Leg shear force and bending moment - jack-ups with a fixation system COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 56 Rev 3, August 2008 Figure 5.3: Leg shear force and bending moment - jack-ups without a fixation system and having a fixed jacking system with opposed pinions COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 57 Rev 3, August 2008 Figure 5.4: Leg shear force and bending moment - jack-ups without a fixation system and having a fixed jacking system with unopposed pinions COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 58 Rev 3, August 2008 Figure 5.5: Leg shear force and bending moment - jack-ups without a fixation system and having a floating jacking system COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 59 Rev 3, August 2008 Figure 5.6: Correction of point supported guide model for finite guide length (After DNV Class Note 31.5, 1992 [6]) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 60 Rev 3, August 2008 5 GLOSSARY OF TERMS - STRUCTURAL ENGINEERING A = Equivalent axial area of a leg for stiffness calculations. ACi = Area of chord including a contribution from the rack teeth (see note to Section 5.6.4.) AD = Axial area of an inclined brace. AQi = Equivalent shear area of a leg face. AQy = Equivalent shear area of a leg in y direction. AQz = Equivalent shear area of a leg in z direction. AV = Axial area of a brace perpendicular to the chords. d = Length of inclined brace or face to face distance between chords for lattice structures without inclined braces. D = Self weight and non-varying loads. Dn = Inertial loads due to Dynamic response. E = Environmental loads. h = Distance between chord centroids. h = Length of guide. IB = Second moment of area of 'brace'. IG = Second moment of area of longitudinal girder. IT = Equivalent torsional constant of leg about longitudinal axis. IY = Equivalent second moment of area of leg about y-y axis for stiffness calculations. Iz = Equivalent second moment of area of leg about z-z axis for stiffness calculations. L = Variable loads. L = Distance from the spudcan reaction point to the hull vertical center of gravity. N = Number of bays, used in determination of equivalent shear area AQ. OT = Total horizontal offset of leg base with respect to hull = O1 + O2 O1 = Offset of leg base with respect to hull due to leg-hull clearances. O2 = Offset of leg base with respect to hull due to maximum hull inclination permitted by the operating manual. P = Average axial load in the legs at the hull (total leg load divided by number of legs). P = Guide reaction. PE = Euler buckling load of an individual leg. Pg = Total effective gravity load on legs at hull, including the hull weight and weight of legs above hull. s = Leg bay height (distance between brace nodes). δs = Linear elastic first order displacement of hull. Δ = Approximate hull displacement including P-Δ effects = δs /(1 - P/PE) v = Poissons ratio for the material = 0.3 for steel. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 61 Rev 3, August 2008 6 CALCULATION METHODS - GEOTECHNICAL ENGINEERING 6.1 Introduction 6.1.1 Section 6 addresses three groups of geotechnical areas of concern which are discussed in the following subsections: 6.2 Prediction of footing penetration during preloading. 6.3 Jack-up foundation stability after preloading. 6.4 Other aspects of jack-up foundation performance during or after preloading. 6.1.2 Where geotechnical analyses are performed they should be based on geotechnical data obtained from a site investigation incorporating soil sampling and/or in-situ testing (see Section 3.16). 6.1.3 Uncertainties regarding the geotechnical data should be properly reflected in the interpretation and reporting of analyses for which the data are used. 6.1.4 The majority of spudcans are effectively circular in plan but other spudcan geometries are not uncommon. Typical spudcan designs are illustrated in Figure 6.1. The bearing capacity formulas given in this section are consistent with 'circular' spudcan footings without skin-friction on the leg. Due consideration should be given to the tapered geometry of most spudcans for bearing capacity assessment. Note: Terms which are not defined in the text may be found in the Glossary to this Section. 6.2 Prediction of Footing Penetration During Preloading 6.2.1 Analysis Method The conventional procedure for the assessment of spudcan load/penetration behavior is given in the following steps: 1. Model the spudcan. 2. Compute the vertical bearing capacity of the footing at various depths below seabed using closed form bearing capacity solutions and plot as a curve. 3. Enter the vertical bearing capacity versus footing penetration curve with the specified maximum preload and read off the predicted footing penetration. For conventional foundation analyses the spudcan can often be modeled as a flat circular foundation. The equivalent diameter is determined from the area of the actual spudcan cross section in contact with the seabed surface, or where the spudcan is fully embedded, from the largest cross sectional area. Foundation analyses are then performed for this circular foundation at the depth (D) of the maximum cross sectional area in contact with the soil. (See Figure 6.2). Alternative shapes, e.g. tubular legs, should be treated as appropriate. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 62 Rev 3, August 2008 Figure 6.1: Typical spudcan geometries Figure 6.2: Spudcan foundation model COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 63 Rev 3, August 2008 The depth of spudcan penetration is usually defined as the distance from the spudcan tip to the mudline. It is therefore necessary to correct for this when referring to the analytical foundation model. The possibility of soil back-flow over the footing should be considered when computing bearing capacity. In very soft clays complete back-flow may occur whereas in firm to stiff clays and granular materials, where limited footing penetration may be expected, the significance of back-flow diminishes. Back-flow in clay may be assumed not to occur if: D ≤ Ncus γ ' where, in this case, cus is taken as the average undrained cohesive shear strength over the depth of the excavation, N is a stability factor and γ' is the submerged unit weight of the soil. Conservative stability factors in uniform clays, as a function of excavation depth and diameter, are summarized in Figure 6.3. Alternative stability factors are given in the Commentary. For spudcan penetration analyses it is recommended that conservative criteria are used and the excavation depth be considered as the depth to the maximum spudcan bearing area. Both the bearing capacity analyses and the above back-flow analysis are based on simple solutions developed for other geotechnical purposes or foundation conditions. These differences should be recognized and are discussed further in the Commentary. The equations given in the following sections may be considered with or without soil back-flow over the footing. The additional load from back-flow on the footing increases the maximum penetration. In general two cases can be distinguished: - Immediate back-flow - Hole side walls collapse after the installation phase. For deeply penetrated footings the effect of side wall collapse after preloading will be to significantly reduce the ultimate vertical bearing capacity of the foundation. Where relevant this phenomenon should be considered. For spudcan penetration analyses the ultimate vertical bearing capacity, FV, may be determined at a series of spudcan penetration depths according to the criteria given in Sections 6.2.2 to 6.2.6. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 64 Rev 3, August 2008 Figure 6.3: Stability factors for cylindrical excavations in clay 6.2.2 Penetration in Clays The ultimate vertical bearing capacity of a foundation in clay (undrained failure in clay, φ = 0) at a specific depth can be expressed by: FV = (cu.Nc.sc.dc + po')A. The maximum preload is equal to the ultimate vertical bearing capacity, FV, taking into account the effect of backflow, Fo'A, and the effective weight of the soil replaced by the spudcan, γ'V (see Commentary) i.e.: VLo = FV - F'oA + γ'V See Figures 6.2 and 6.4 and note that the terms - F'oA + γ'V should always be considered together. It is recommended that the value of undrained cohesive shear strength, cu, is taken as the average value over a distance B/2 from beneath the level where the maximum spudcan diameter is in contact with the soil. (Refer to the Commentary). The bearing capacity formula given above has been empirically derived for surface foundations and does not account for foundation roughness, shape (conical for most spudcans) or the effects of increased shear strength with depth. These factors are taken into account in a method provided in the Commentary. Note: It is recognized that the bearing capacity of a soil may reduce when subjected to cyclic loading. (Refer to the Commentary.) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 65 Rev 3, August 2008 Figure 6.4: Spudcan bearing capacity analysis 6.2.3 Penetration in Silica Sands The ultimate vertical bearing capacity of a circular footing resting in silica sand or other granular material can be computed by the following equation; FV = (0.5 γ'B Nγ sγ dγ + po' Nq sq dq)A The maximum preload is equal to the ultimate vertical bearing capacity, FV, taking into account the effect of backflow, Fo'A, and the effective weight of the soil replaced by the spudcan, γ'V (see Commentary) i.e.: VLo = FV - F'oA + γ'V See Figures 6.4 and note that the terms -F'oA + γ'V should always be considered together. Typically observed load-penetration data for large diameter spudcans suggest that reduced friction angles may be applicable for this analysis method. To account for this it is appropriate to reduce the laboratory derived φ by 5°. Further recommendations on the selection of φ values are given in the Commentary together with a discussion regarding the use of alternative bearing capacity factors. 6.2.4 Penetration in Carbonate Sands Penetrations in carbonate sands are highly unpredictable and may be minimal in strongly cemented materials, or large, in uncemented materials. Extreme care should be exercised when operating in these materials. Further discussion regarding these soil conditions is provided in the Commentary. 6.2.5 Penetration in Silts It is recommended that upper and lower bound analyses for drained and undrained conditions are performed to determine the range of penetrations. The upper bound solution is modeled as a loose sand and the lower bound solution as a soft clay. Cyclic loading may significantly affect the bearing capacity of silts. See discussion in Commentary. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 66 Rev 3, August 2008 6.2.6 Penetration in Layered Soils Three basically different foundation failure mechanisms are considered in spudcan predictions in layered soils: 1. General shear. 2. Squeezing. 3. Punch-through. The first failure mechanism occurs if soil strengths of subsequent layers do not vary significantly. Thus an average soil strength (either cu or φ) can be determined below the footing. The footing penetration versus foundation capacity relationship is then generated using criteria from Sections 6.2.2 through 6.2.5. Criteria for the other two failure mechanisms (squeezing and punch-through) are given below. The last condition is of particular significance since it concerns a potentially dangerous situation where a strong layer overlies a weak layer and hence a small additional spudcan penetration may be associated with a significant reduction in bearing capacity. 6.2.6.1 Squeezing of clay On a soft clay subject to squeezing overlaying a significantly stronger layer (Figure 6.5), the ultimate vertical bearing capacity of a footing given by Meyerhof [8] is: For no back-flow conditions: FV = A{(a + bB T + 12. D B ) cu + po'} ≥ A{Nc sc dc cu + po'} and for full back-flow conditions: FV = A{(a + bB T + 12. D B ) cu} + Vγ' ≥ A{Nc sc dc cu} + Vγ' where the following squeezing factors are recommended: a = 5.00 b = 0.33 and cu refers to the undrained shear strength of the soft clay layer. Figure 6.5: Spudcan bearing capacity analysis - squeezing clay layer COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 67 Rev 3, August 2008 It is noted that the lower bound foundation capacity is given by general failure in the clay layer (right hand side of equation), and that squeezing occurs when B ≥ 3.45T(1+1.1D/B). The upper bound capacity (for T<<B) is determined by the ultimate bearing capacity of the underlying strong soil layer. Comment on the limits included in the above relationships is provided in the Commentary. 6.2.6.2 Punch-through: Two clay layers The ultimate vertical bearing capacity of a spudcan on the surface of a strong clay layer overlying a weak clay layer can be computed according to Brown [9]: FV = A (3 H B cu,t + Nc sc cu,b) ≤ A Nc sc cu,t See Figure 6.6. For the evaluation of punch-through potential for deep footings, and to achieve compatibility with the equations used for homogeneous clays, the following equations are recommended: For no back-flow conditions: FV = A {3 H B cu,t + Nc sc (1 + 0.2 D H B + ) cu,b + po'} ≤ A(Nc sc dc cu,t + po') and for full back-flow conditions: FV = A [3 H B cu,t + Nc sc (1 + 0.2 D H B + ) cu,b] + γ'V ≤ A Nc sc dc cu,t + γ'V Figure 6.6: Spudcan bearing capacity analysis - firm clay over weak clay COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 68 Rev 3, August 2008 6.2.6.2 It is noted that the condition (firm clay over soft clay) can also be "man-made" as in some clays artificial crusts can form during delays in the installation procedure. Caution is therefore required in situations where soil sampling/testing is performed from a jack-up prior to preloading. 6.2.6.3 Punch-through: Sand overlying clay The ultimate vertical capacity of a spudcan on a sand layer overlying a weak clay layer can be computed using: For no back-flow: FV = FV,b - A Hγ' + 2 H B (Hγ' + 2 p'o) Kstanφ A and for full or partial back-flow: FV = FV,b - A Hγ' - A I γ' + 2 H B (Hγ' + 2 p'o) Kstanφ A where; FV,b is determined according to Section 6.2.2 assuming the footing bears on the surface of the lower clay layer, with no back-flow. See Figure 6.7. The coefficient of punching shear, Ks, depends on the strength of both the sand layer and the clay layer. For practical purposes a lower bound for the term Ks tanφ, applicable to the onset of punch-through, can be approximated by: Ks tanφ ≈ 3cu/Bγ' An alternative analysis method is described in the Commentary. Figure 6.7: Spudcan bearing capacity analysis - sand over clay COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 69 Rev 3, August 2008 6.2.6.4 Three Layered Systems The foundation bearing capacity for a spudcan resting on three soil layers can be computed using the squeezing and punch-through criteria for two layer systems. Firstly the bearing capacity of a footing with diameter B resting on top of the lower two layers is computed. These two layers can then be treated as one (lower) layer in a subsequent two layer system analysis involving the (third) upper layer. For further explanation see Figure 6.8. Figure 6.8: Spudcan bearing capacity analysis - three layer case Analysis 2 QV Layer 1 Analysis 1 QV Layer 2 Layer 3 Use 2 layer bearing capacity procedures for both analyses Analysis 2 Analysis 1 Layer 1 over (Layer 2 and 3) Layer 2 over layer 3 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 70 Rev 3, August 2008 6.3 Foundation Stability Assessment 6.3.1 Approach The overall foundation stability may be assessed using a phased method with three steps increasing in order of complexity (See Figure 6.9): - Step 1 Preload and Sliding Check (Section 6.3.2). The foundation capacity check is based on the preloading capability. Sliding of the windward leg is also checked. Loads from pinned footing analysis. - Step 2 Bearing Capacity Check. Step 2a Bearing capacity check (Section 6.3.3), based on resultant loading, assuming a pinned footing. (see Section 5.3.1). Also check sliding. Step 2b Bearing capacity check (Section 6.3.4), including rotational, vertical and translational foundation stiffness. - Step 3 Displacement Check (Section 6.3.5). The displacement check requires the calculation of the displacements associated with an overload situation arising from Step 2b. Any higher level check need only be performed if the lower level check fails to meet the foundation acceptance criteria given in Section 8.3. The following sections give details regarding the three phased acceptance procedure. However, there are certain aspects which are not covered in these sections which may require further consideration. Some of the more common ones are listed below: - Soils where the "long term" (drained) bearing capacity is less than the "short term" (undrained) capacity. This may be the case for overconsolidated cohesive soils (silts and clays) with significant amounts of sand seams. - Where soil back-flows over the spudcan after the preload installation phase, (silts, clays). - If a reduction of soil strength due to cyclic loading occurs. This can be of particular significance for silty soils and/or carbonate materials. - If an increase in spudcan penetration occurs, due to cyclic loading, where a potential punch-through exists. - In soils with horizontal seams of weak soils located beneath the spudcan it is recommended that the lateral bearing capacity/sliding stability of the foundation is verified. If any of the above circumstances exist further analysis is required. In the case of partial spudcan embedment, (e.g. sandy soils), additional footing embedment may result in a considerable increase in bearing capacity. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 71 Rev 3, August 2008 Figure 6.9: Foundation stability assessment COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 72 Rev 3, August 2008 6.3.2 Ultimate bearing capacity for vertical loading - Preload Check (Step 1) Except as discussed in 6.3.1, when the horizontal load is small, the ultimate vertical bearing capacity under extreme conditions is assumed to be the same as the maximum footing load during preloading, (VLo). The minimum requirements for VLo are given in Section 8.3.1.3 or 8.3.2 as applicable. 6.3.3 Bearing Capacity/Sliding Check - Pinned footing (Step 2a) A reduction in vertical bearing capacity, FV, of a footing occurs when it is simultaneously subjected to horizontal loading, QH, and moment loading, QM. The latter is ignored in Step 2a analyses as the footings are considered to be pinned. The vertical/horizontal capacity envelope, FVH, for sands and clays may be generated according to the following criteria, however, further discussion with regard to the analytical applicability is provided in the Commentary. 6.3.3.1 Ultimate Vertical/horizontal bearing capacity envelopes for spudcan footings in sand: The general ultimate vertical/horizontal bearing capacity envelope for jack-up footings in sand is as follows: FVH = A (0.5 γ' B Nγ sγ iγ dγ + po'Nq sq iq dq) During the preloading phase it may be assumed that no horizontal load acts on the foundation and that the ultimate vertical bearing capacity of the soil is in equilibrium with the applied footing installation load, VLo. The applied footing installation load should include the effect of back-flow and spudcan buoyancy i.e. VLo = FV - Fo'A + γ'V. In this instance the inclination factors assume values of unity and the remaining terms may be defined. Substituting for iq and iγ the appropriate relationship may be written for generation of the foundation capacity for combined vertical and horizontal loading as: FVH = A {0.5 γ' B Nγ sγ dγ [1 - (FH/ FVH)*]m+1 + po'Nq sq dq [1 - (FH/FVH)*]m} This may be solved by the use of assumed values for (FH/FVH) designated (FH/FVH)*. For example use (FH/FVH)* = 0.00, 0.04, 0.08, 0.12, etc. For these values corresponding FVH values may be determined. The correct FH values may then be determined as FVH and (FH/FVH)* are known, e.g. for (FH/FVH)* = 0.12, FH* = 0.12 FVH*. The corrected horizontal capacity, FH, may then be given as: FH = FH* + 0.5γ' (kp - ka) (h1 + h2) As The sliding capacity envelope of a footing in sand is given by: FH = FVHtanδ + 0.5γ' (kp - ka) (h1 + h2) As where δ is the steel/soil friction angle which for a flat plate, δ = φ - 5°, and for a rough surfaced conically shaped spudcan δ = φ. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 73 Rev 3, August 2008 6.3.3.2 Ultimate vertical/horizontal bearing capacity envelopes for spudcan; footings in clay The general equation for the horizontal and vertical bearing capacity envelopes for footings in clay is as follows: FVH = A [(Nc cu sc dc ic) + po' Nq sq iq dq] Substituting for the inclination factors for a circular footing the equation may be written as: FVH = A {Nc cu sc dc [1 - (1.5FH*/NcAcu)] + po' Nq sq (1 - FH*/FVH)1.5 dq} The ultimate bearing capacity envelope under inclined loading may be determined by substituting values of FVH and solving for FH*. FH may then be given as: FH = FH* + (cuo + cul)As Footing sliding capacity in clay: When 0 ≤ QV ≤ 0.5 FV the sliding capacity in clay may be conservatively assumed constant, determined by: FH = Acuo + (cuo + cul)As 6.3.3.3 Ultimate vertical/horizontal bearing capacity envelopes for spudcan for spudcan footings on layered soils. The above formulas (Sections 6.3.3.1 through 6.3.3.2) can also generally be used to make a conservative estimate of the ultimate FVH-FH relationship for layered soils by considering failure through the weakest zones in such a soil profile. The bearing capacity of layered soils may be determined using the principles of limiting equilibrium analysis or the finite element method. 6.3.3.4 Settlements resulting from exceedence of the capacity envelope Vertical settlement and/or sliding of a footing can occur if the storm load combination is in excess of the (FVH-FH) resistance envelope computed for the spudcan at the penetration achieved during installation. Such settlements can result in a gain of (FVH-FH) bearing capacity, e.g. in silica sands. However, the integrity of the foundation may decrease in the situation where a potential punch-through exists, e.g. where dense sand overlies soft clay. More thorough analyses are required for complex and/or potentially dangerous foundation conditions of the type listed in Section 6.3.1. 6.3.4 Footing with moment fixity and vertical and horizontal stiffness (Step 2b) Foundation fixity is the rotational restraint offered by the soil supporting the foundation. The degree of fixity is dependent on the soil type, the maximum vertical footing load during installation, the foundation stress history, the structural stiffness of the unit, the geometry of the footings and the combination of vertical and horizontal loading under consideration. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 74 Rev 3, August 2008 Inclusion of foundation fixity in an assessment incorporates a check on bearing capacity in terms of vertical and horizontal (sliding) capacities. The amount of rotational fixity is not directly involved in a checking equation, but it serves to modify the forces (beneficially) in both the foundation and structure. The bearing and sliding checks are performed implicitly through the use of the yield function and explicitly through the bearing capacity and sliding checks described in Section 6.3.3. Uncertainties in soil properties should be considered when including fixity in assessments. Where data reliability is uncertain, an upper/lower bound sensitivity analysis should be performed. For performing structural analysis, horizontal and vertical spring stiffnesses should be included in addition to the rotational stiffness (see Section 5.3). The springs should be applied to the spudcan support point as defined in Section 5.2. The calculation of fixity should be based on factored environmental loading including dead, live, environmental, inertial and P-Δ loads. 6.3.4.1 Calculation procedures accounting for moment fixity – See also 6.3.4.6 The interaction of vertical, horizontal and rotational forces has been modeled based on a plasticity relationship (References C6 [48] through [52]). The plasticity relationship can account for moment softening at high load levels, unloading behavior and workhardening effects. This type of foundation modeling is preferable if foundation fixity is to be included directly in a time-domain analysis. For a pseudo-static analysis, a simplified application of this full plasticity analysis is described in this section. This simple approach can be used to create moment loads on the spudcan by inclusion of a simple linear rotational spring to generate moments at the spudcan. The moment thus induced on the spudcan is limited to a capacity based on the yield interaction relationship among vertical (QV), horizontal (QH) and moment (QM) loads acting at the spudcan. This simple procedure is described in the following steps: 1. Include vertical, horizontal and (initial) rotational stiffnesses (linear springs) to the analytical model and apply the gravity and factored metocean and inertial loading. 2. Calculate the yield interaction function value using the resulting forces at each spudcan. For extreme wave analysis, the result will likely indicate the force combination falls outside the yield surface. In this case, reduce the rotational stiffness (arbitrarily) and repeat the analysis. 3. Continue with step 2 until the force combination at each spudcan lies essentially on the yield surface. If the moment is reduced to zero, and the force combination is still outside the yield surface, then a bearing failure (either vertical or horizontal) is indicated. 4. If a force combination initially falls within the yield surface, the rotational stiffness must be further checked to satisfy the reduced stiffness conditions in Section 6.3.4.3. The following sections are applicable to traditional spudcan designs. Information on spudcans fitted with skirts can be found in references C6 [48] through [51]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 75 Rev 3, August 2008 6.3.4.2 Ultimate Vertical / horizontal / rotational capacity interaction; function for spudcan footings in sand and clay For shallow embedment for both sand and clay, the yield interaction is defined by the following expression: 4 1 0 2 2 = ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ + ⎥⎦ ⎤ ⎢⎣ ⎡ Lo VHM Lo VHM Lo M Lo HM V F V F M F H F where VLo is taken to be equal to the vertical spudcan load achieved during preloading and HLo and MLo are defined as follows: For sand: C = 0.3, C = 0.625 0.075 / 4 0.12 ( / )( / 4) 1 2 1 1 2 with V B M C V B V H C C V Lo Lo Lo Lo Lo Lo ⎪ ⎪ ⎭ ⎪ ⎪ ⎬ ⎫ = = = = For clay: HLo = cuoA + (cuo + cul) As MLo = 0.1VLoB Note that in the above expression for the yield surface, if a load combination (QV,QH,QM) satisfies the equality then (QV,QH,QM) = (FVHM, FHM, FM). The load combination (QV,QH,QM) lies outside the yield surface if the left-hand side is greater than zero. Conversely, the load combination lies inside the yield surface if the left-hand side is less than zero. The expression for the yield surface can be re-written to give the maximum spudcan moment as a function of the horizontal and vertical loads. Thus, for a given vertical and horizontal load combination which, with zero moment, lies inside the yield surface given above, the maximum moment at a spudcan cannot exceed the value defined below. FM = MLo 2 2 2 0 5 16 1 . Lo H Lo V Lo V H Q V Q V Q ⎪⎭ ⎪⎬ ⎫ ⎪⎩ ⎪⎨ ⎧ ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ The equation above only applies when: V Lo 0.0 < Q < V ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ < Lo V Lo V H Lo V Q V Q Q 4H 1 Embedded footings in clay achieve greater moment and sliding capacities as compared to shallow penetrations in clay. For fully or partially penetrated spudcans, the yield surface at FVHM/VLo<0.5 can be expressed as: 2 1 ⎥⎦ ⎤ ⎢⎣ ⎡ Lo HM f H F + 2 2 ⎥⎦ ⎤ ⎢⎣ ⎡ Lo M f M F - 1.0 = 0 where; f1 = α + 2(1 - α) V Lo Q V ⎡ ⎤ ⎢ ⎥ ⎣ ⎦ COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 76 Rev 3, August 2008 f2 = f1 where suction (i.e. uplift resistance) is available, = 4 V Lo Q V ⎡ ⎤ ⎢ ⎥ ⎣ ⎦ 1 V Lo Q V ⎡ ⎤ ⎢ − ⎥ ⎣ ⎦ where suction cannot be relied upon α = 1.0 for soft clays = 0.5 for stiff clays α accounts for the degree of adhesion. Engineers may want to consider α values within the range 0.5-1.0 depending on site specific soil data, spudcan/soil interface roughness, etc. An α value less than 0.5 may be considered for situations such as a hard clay at the surface. In this case, the standard form of the yield surface should be considered. Thus, for a given vertical and horizontal load combination which, with zero moment, lies inside the yield surface given above, the maximum moment at a spudcan for a clay foundation with QV/VLo<0.5 cannot exceed the value defined below: 2 0.5 2 0 1 1 H M L Lo F f M Q f H ⎧⎪ ⎡ ⎤ ⎪⎫ = ⎨ − ⎢ ⎥ ⎬ ⎩⎪ ⎣ ⎦ ⎪⎭ The equation above only applies when: V Lo 0.0 < Q < V H Lo Q f H 1 < There is no existing data for deeply embedded footings in sand. The application of the yield surface calibrated to shallow penetrations will likely be conservative for the deep penetration case. 6.3.4.3 Estimation of rotational, vertical, and horizontal stiffness An initial estimate for rotational stiffness, K3, which is applicable for a flat spudcan without embedment (Winterkorn [10]) under relatively low levels of load is given below: K3 = 3(1 ) 3 −ν GB , flat spudcan with no embedment Values for K3 for other cases are given in the Commentary. The selection of the shear modulus, G, is discussed in the Commentary. An upper or lower bound value should be selected as appropriate for the analysis being undertaken. For clays susceptible to cyclic degradation (OCR ≥ 4) the soil rotational stiffness, calculated from the degraded static soil properties, may be multiplied by a factor of 1.25, Anderson [18]. If the load combination of (QV,QH,QM) lies outside the yield surface, the linear rotational stiffness at the spudcan must be reduced until the load combination lies on the yield surface. The reduction in stiffness is arbitrary and requires iterative analyses. It should be noted that if the initial load combination (QV,QH,QM) lies outside the yield surface, the final value of the rotational stiffness is determined only by the requirement that the generated moment at the spudcan falls on the yield surface. If the load combination of (QV,QH,QM) lies inside the yield surface, the initial estimate of rotational stiffness should be reduced by a factor, fr. The reduction factor is equal to COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 77 Rev 3, August 2008 unity when the moment and horizontal forces are zero. It is given by the following expression (Svanø, [56]): fr = (1- r ) + 0.1e f 100(rf −1) where rf is the failure ratio defined by: rf = ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ ⎪⎭ ⎪⎬ ⎫ ⎪⎩ ⎪⎨ ⎧ ⎥⎦ ⎤ ⎢⎣ ⎡ + ⎥⎦ ⎤ ⎢⎣ ⎡ Lo V Lo V . Lo M Lo H V Q V Q M Q H Q 4 1 2 2 0 5 Note that rf > 1.0 implies that the load combination (QV,QH,QM) lies outside the yield surface. Under such conditions, the reduced stiffness factor is not applicable. For fully embedded foundations in clays at vertical load ratio FVHM/VLo < 0.5, the failure ratio may be expressed as: rf = 2 2 0.5 H M 1 Lo 2 Lo Q Q f H f M ⎧⎪⎡ ⎤ ⎡ ⎤ ⎪⎫ ⎨⎢ ⎥ + ⎢ ⎥ ⎬ ⎩⎪⎣ ⎦ ⎣ ⎦ ⎪⎭ where f1 and f2 are as defined in Section 6.3.4.2 above, but replacing FVHM with QV. Vertical and horizontal stiffnesses can be estimated from the elastic solutions for a rigid circular plate on an elastic half-space (assuming no embedment): Vertical stiffness, K1 = (1 ) 2GB −ν Horizontal stiffness, K2 = (7 8 ) 16GB(1 ) ν ν − − Advice on the selection of appropriate values for G may be found in the Commentary. 6.3.4.4 Extension of the yield surface for additional penetration On seabeds of silica sands, conical spudcans which are not fully seated may show a plastic moment restraint due to further penetration. The effect may be taken into account for legs with QV/VLo > 0. The moment capacity Mp associated with further penetration is estimated as the minimum of MPS and MPV, calculated as follows (Svanø [56]): MPS = 0.075 B VLo(D/B)3 MPV = 0.15 B FVHM in which B is the plan diameter of the effective contact area after preload, and D is the plan diameter of the contact area when the spudcan is fully seated. The combined capacity should be checked against the modified yield function: 4 1 0 2 2 = ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ − ⎥⎦ ⎤ ⎢⎣ ⎡ + ⎥⎦ ⎤ ⎢⎣ ⎡ Lo VHM Lo VHM P M Lo HM V F V F M F H F For additional penetration of spudcans in clay, references C6 [49] and [52] provide work-hardening modifications to the yield surface equations. Updated stiffnesses are determined through plasticity principles. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 78 Rev 3, August 2008 6.3.4.5 Deep Footing Penetration For deep footing penetrations, typically experienced in soft clay conditions, the calculation of foundation fixity may be augmented with the inclusion of the lateral soil resistance on the leg members due to soil back-flow over the spudcan. This lateral soil resistance is effectively added to the rotational elastic stiffness of the spudcan (as determined in Section 6.3.4.3), (Brekke [7]). The lateral soil resistance may be modeled based on concepts proposed by Matlock [17] for lateral soil resistance of piles. The jack-up leg may be modeled as an equivalent pile for purposes of determining "p-y", or load-deflection curves. The diameters of the individual members (i.e., leg chords and braces) give appropriate characteristic dimensions for determining the p-y curves. The p-y curve for each member is summed to form a p-y curve for the entire leg. Only one face of each leg should be assumed to be in contact with the soil and contribute to lateral resistance. Given a set of p-y curves for the leg, the lateral force-deflection along the entire embedded leg section is thus determined. Typically, equivalent springs at each bay elevation are used to simplify the calculations. 6.3.4.6 Calculation procedures accounting for moment fixity – further details Structural analyses should account for rotational, horizontal and vertical stiffnesses at all spudcans. The jack-up is then acceptable if the following conditions are met: 1. Structural conditions satisfy acceptance criteria outlined in Section 8.1. 2. Factored foundation loads QV, QH satisfy, as applicable, the bearing capacity criteria in Sections 8.3.2 or 8.3.1.5. 3. Factored foundation loads QV, QH, QM satisfy the appropriate unfactored yield surface criterion from Section 6.3.4.2 or 6.3.4.4. Factored foundation loads exceeding this requirement are permitted provided that the soil-structure interaction model adopted accurately captures the expansion of the foundation yield surface after first yield, and that the large-displacement effects of associated structural displacements are taken into account. 4. The analysis ensures load & displacement compatibility between the foundation and the structure. 5. The location is not prone to, or is protected from, scour so that the assumed fixity is assured. Fixity may be included in the response simulation in three ways (Refer to Figure 6.11 below): 1. By conservatively considering effects of changes to seabed boundary reactions only and ignoring any reduction in the dynamic response with pinned footings. In this approach quasi-static analyses are used in the iterations of the procedure given in Section 6.3.4.1 to derive the foundation rotational and horizontal secant stiffnesses with loadings obtained from the pinned foundation case including dynamics. This approach is not applicable if the inclusion of fixity brings the natural period closer to the wave period. 2. By considering linearised fixity in SDOF or more detailed dynamic calculations and then carrying out a final quasi-static analysis with non-linear fixity using the procedure of Section 6.3.4.1. If this approach is adopted, care should be taken to ensure that the natural period with fixity does not fall at a cancellation point in the COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 79 Rev 3, August 2008 wave force transfer function (Sections 7.3.5.2, 7.3.5.4, C7.4 & Fig C7.1). Typically the initial linearised rotational stiffness for the dynamic analysis may be taken as 80% of value determined from the formulation in the first paragraph of Section 6.3.4.3. When this stiffness is adjusted to avoid wave force cancellation, the adjusted value may lie anywhere between 0% and 100% of the value from Section 6.3.4.3. This simplified approach does not capture the temporary reductions in stiffness which occur during plasticity events, but also does not capture the increased damping that is associated with these events; these two effects are considered to be largely self-cancelling. Given that care is taken to avoid wave force cancellation effects, it is considered that the dynamic response will be determined at a level which is either realistic or conservative. For further discussion of approaches which may be used to avoid cancellation and reinforcement effects refer to the Commentary Section C7.4. 3. By considering the effects of the foundation fixity on both the dynamic response and the seabed reactions. This approach is more complete and may require a complex iterative calculation procedure. The following outline procedure may be adopted: a) Use a time-domain dynamic analysis to determine structural response and foundation loadings at each time step. b) Compute the foundation behaviour using a non-linear elasto-plastic model, such that at each time step the plastic and elastic portions of the behaviour are captured. If desired, this model may include hysteresis. This will likely require an iterative procedure. c) When plasticity occurs, the responses will be influenced by the load history. Consideration should be given to ensuring that the methodology used to determine the extreme values provides stable results. In cases where the analysis is intended to provide final results (rather than DAF’s for application in subsequent analysis step) it may be appropriate to perform analyses for differing wave histories, and then determine the extremes from a procedure such as that given in C7.B.2.3. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 80 Rev 3, August 2008 Figure 6.10: Calculation procedure to account for foundation fixity COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 81 Rev 3, August 2008 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 82 Rev 3, August 2008 6.3.5 Displacement Check (Step 3) Structural model with nonlinear soil response included When a Step 2 assessment results in an overload situation, Step 3 may be used to calculate the associated displacements and rotations from a full nonlinear loaddisplacement foundation model. The procedure should account for the load redistribution resulting from the overload and displacement of the spudcan(s). The displacements derived from the analysis should be checked against the allowable displacements of the spudcans and should satisfy the following requirements: - The spudcan vertical and horizontal displacements should not lead to unacceptable overturning or strength checks. - The resulting rotation of the unit should neither exceed the limitations defined by the operating manual nor lead to the possibility of contact with any adjacent structure. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 83 Rev 3, August 2008 6.4 Other Aspects of Jack-Up Unit Foundation Performance 6.4.1 Leaning Instability Leaning instability of jack-ups can occur during preloading operations in soft clays where the rate of increase in bearing capacity with depth is small. In deep water a potentially unsafe condition (comparable to a punch-through situation) may occur. However, the potential for such incidents may be discounted if appropriate installation procedures are adopted. These may, for example, include preloading the footings individually. Further discussion on leaning instability is included in the Commentary. 6.4.2 Footprint Considerations The seabed depressions which remain when a jack-up is removed from a location are referred to as 'footprints'. The form of these features depends on several factors such as the spudcan shape, the soil conditions, the footing penetration achieved and the method of extraction. The shape, and the time period over which the form will exist, will also be affected by the local sedimentary regime. The positioning of spudcans very close to, or partially overlapping, footprints is not recommended. The difference in resistance between the original soil and the disturbed soil in the footprint area and/or the slope at the footprint perimeter, may cause the spudcans to slide towards the footprint. The resulting leg displacements could cause severe damage to the structure and, at worst, could lead to catastrophic failure. The situation could be complicated by the proximity of a fixed structure or wellhead. The following two operational sequences may be considered: a) Installation of an identical jack-up design to that previously used at a particular location: If a jack-up with identical footing geometry to the unit previously used is to be installed, the re-positioning should not cause problems provided that the jack-up is located in exactly the same position as for the previously installed unit. Thus the footings would lie in the existing footprints. It is therefore necessary to ensure that reliable records are obtained of the exact location of existing footprints in relation to the well/jacket. If the new spudcan positions are not located directly over the footprints sliding of the legs may occur with the potential consequences described above. b) Installation of a jack-up of different design to that previously used at a particular location: It is unlikely for two jack-up designs to have similar footing geometries. It is therefore probable that it will not be possible to locate the spudcans exactly within the existing footprints. However, it may be possible to carefully position the jack-up on a new heading, and/or with one footing located over a footprint with the others in virgin soil, to alleviate the potential for spudcan sliding. Again reliable records of existing footprint locations (and depths) are required. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 84 Rev 3, August 2008 Where it is not possible to locate the jack-up to avoid spudcan-footprint interaction special attention is required to minimize the potential sliding problem. Consideration may be given to infilling the footprints with imported materials. The material selection should recognize the potential for material removal, by scour, and the differences of material stiffness. Further discussion is included in the Commentary. 6.4.3 Scour Scour may occur when a footing or other object is installed on the seabed, and its presence causes increased local current velocities. The phenomenon is usually observed around spudcans which are embedded to a shallow level in granular materials at locations with high current velocities. Scour may partially remove the soil from below the footing, resulting in a reduction of the ultimate bearing capacity of the foundation and any seabed fixity. This is normally a gradual process and the effects of the reduced bearing capacity may not be apparent until during storm loading when (rapid) downward movement of the leg may occur. The effects of scour are potentially more severe when it occurs at a location where a potential for punch-through exists. There is no definitive procedure for the evaluation of scour potential and emphasis must usually be placed on previous operational experience. Further guidance is given in the Commentary. If scour is recognized to be a potential problem, then preventative measures should be implemented. These should be adopted on a trial basis and include: a) Gravel dumping prior to installation provided the selected gravel gradation will not cause damage to the jack-up footing. b) Installation of artificial seaweed. c) Use of stone/gravel dumping, gravel bags or grout mattresses after installation. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 85 Rev 3, August 2008 6.4.4 Seafloor Instability Seafloor instability may be caused by a number of mechanisms which may be interactive or act independently. The most frequent types of instability result in large scale mass movement, in the form of mudslides or slope failures. Such phenomena are often associated with deltaic deposits, and it is recommended that the advice of local experts is obtained when such situations are encountered. Liquefaction, or cyclic mobility, occurs when the cyclic stresses within the soils cause a progressive build up of pore pressure. The pore pressure within the profile may build up to a stage where it becomes equal to the initial average vertical effective stress. Foundation failure may result depending on the extent of pore pressure developed. Such failures may be manifested as continued foundation settlements or large scale failure of the soil mass as described above. In areas where liquefaction is known to be possible its potential must be assessed. For further guidance refer to the Commentary. 6.4.5 Shallow Gas Gas in soils may originate from biogenic degradation or thermogenic diagenesis. Gas charged sediments may result in hazards during site investigation soil borings, reduced bearing capacity, unpredictable foundation behavior (due to seabed depressions or gas accumulations under the spudcans) and complications with shallow drilling operations, including blowouts. The presence of gas charged sediments may be identified by geophysical digital high resolution shallow seismic surveys using attribute analysis techniques. Any gas concentration should be avoided if it is located above the primary casing shoe level (generally 20 inch or 18.75 inch diameter casing) or the conductor pipe shoe level which are determined during the drilling program design. This is because neither of these holes are drilled under BOP control and, therefore, there is a risk of seabed cratering around the well which could result in the undermining of the footings in the event of a blow out. Of lesser risk is the potential for gas migration from depth to the surface outside the casing. Although this occurrence is uncommon the potential should not be discounted. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 86 Rev 3, August 2008 6.4.6 Spudcan - Pile Interaction For jack-ups located in close proximity to pile-founded platforms, soil displacements caused by the spudcan penetration will induce lateral loading into the nearby piles. The amount of soil displacement will depend on the spudcan proximity (spudcan edge-to-pile distance), the spudcan diameter and penetration. If the foundation materials comprise either a deep layer of homogeneous firm to stiff clay or sand and if the proximity of the spudcan to the pile is greater than one spudcan diameter, then no significant pile loading is expected. When the proximity is closer than one spudcan diameter, then analysis by the platform owner is recommended to determine the consequences of the induced pile loading. Guidance regarding the analytical procedures available for assessing these spudcan induced pile loads is given in the Commentary. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 87 Rev 3, August 2008 6 GLOSSARY OF TERMS - CALCULATION METHODS, GEOTECHNICAL ENGINEERING A = Spudcan effective bearing area based on cross-section taken at uppermost part of bearing area in contact with soil (see Figure 6.2). As = Spudcan laterally projected embedded area. a = Bearing capacity squeezing factor. au = Adhesion. B = Effective spudcan diameter at uppermost part of bearing area in contact with the soil (for rectangular footing B = width). b = Bearing capacity squeezing factor. cu = Undrained cohesive shear strength at D + B/4 below mudline. cu1 = Undrained cohesive shear strength at spudcan tip. cuo = Undrained cohesive shear strength at maximum bearing area (D below mudline). cus = Undrained cohesive shear strength at D/2 below mudline. cu,b = Undrained cohesive shear strength - lower clay below spudcan. cu,t = Undrained cohesive shear strength - upper clay below spudcan. CC 1 2 == ⎫⎬⎭ Constants used in computation of H and V for sand. Lo Lo dc = Bearing capacity depth factor. = 1 + 0.4 (D/B) for D/B ≤ 1. = 1 + 0.4 arctan (D/B) for D/B > 1. dq = Bearing capacity depth factor. = 1 + 2tanφ(1- sinφ)2 D/B for D/B ≤ 1 = 1 + 2tanφ(1- sinφ)2 arctan(D/B) for D/B > 1 dγ = Bearing capacity depth factor = 1. D = Distance from mudline to spudcan maximum bearing area. f1 = Factor used in yield surface equation for embedded footings on clay. f2 = Factor used in yield surface equation for embedded footings on clay. fr = Reduction factor on stiffness. Fo' = Effective overburden pressure due to back-flow at depth of uppermost part of bearing area. FH = Horizontal foundation capacity. FHM = Horizontal foundation capacity in combination with moment. FV = Vertical foundation capacity. FV,b = Ultimate vertical bearing capacity assuming the footing bears on the surface of the lower (bottom) clay layer with no back-flow. FVH = Vertical foundation capacity in combination with horizontal load. FVHM = Vertical foundation capacity in combination with horizontal and moment load. FM = Moment capacity of foundation. Gv = Shear Modulus for vertical loading. Gh = Shear Modulus for horizontal loading. Gr = Shear Modulus for rotational loading. h = Distance from rotation point to reaction point. h1 = Embedment depth to the uppermost part of the spudcan, (if not fully embedded = 0). h2 = Spudcan tip embedment depth. H = Distance from spudcan maximum bearing area to weak strata below. HLo = (C1/C2)(VLo/4), C1 = 0.3, C2 = 0.625 (sand) = Acuo +(cuo + cu1)As (clay) ic = Inclination factor (for φ = 0). = 1 - mFH/AcuNc COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 88 Rev 3, August 2008 6 GLOSSARY OF TERMS - CALCULATION METHODS, GEOTECHNICAL ENGINEERING (Continued) iq = Inclination factor. = (1 - FH/FVH)m iγ = Inclination factor. = (1 - FH/FVH)m+1 I Height of soil column above spudcan. ka = Active earth pressure coefficient (for cu = 0) = tan2(45-φ/2) kp = Passive earth pressure coefficient = 1/ka K1,K2,K3 = Stiffness factors. Ks = Coefficient of punching shear. L = Foundation length, for circular foundation L=B. For strip footing - inclination in direction of shorter side. = (2 + B/L)/(1 + B/L) m= For strip footing - inclination in direction of longer side. = (2 + L/B)/(1 + L/B) For circular footing = 1.5 MLo = C1VLoB/4, C1 = 0.3 (sand) = 0.1VLoB (clay) MP = moment capacity associated with further spudcan penetration under environmental loading (equal to minimum of MPS and MPV). MPS = moment capacity when further spudcan penetration leads to fully seated spud conditions. MPV = moment capacity under further spudcan penetration, when the actual vertical force is too low to reach fully seated conditions. n = Iteration factor, ≥ 2. N = Stability factor. Nc = Bearing capacity factor (taken as 5.14). Nq = Bearing capacity factor = eπtanφtan2(45 + φ/2) Nγ = Bearing capacity factor = 2(Nq + 1)tanφ po' = Effective overburden pressure at depth, D, of maximum bearing area. QH = Applied factored horizontal load. QM = Applied factored moment load. QV = Applied factored vertical load. rf = Failure ratio. sc = Bearing capacity shape factor = (1 + (Nq/Nc)(B/L)) sq = Bearing capacity shape factor = 1 + (B/L)tanφ sγ = Bearing capacity shape factor = 1 - 0.4(B/L) ( = 0.6 for circular footing under pure vertical load). T Thickness of weak clay layer underneath spudcan. V = Volume of soil displaced by spudcan. VLo = Maximum vertical foundation load during preloading. α = Adhesion factor = 1.0 for soft clays, = 0.5 for stiff clays. δ = Steel/soil friction angle - degrees, (φ-5≤δ≤φ). δν = Vertical displacement of foundation. δh = Horizontal displacement of foundation. γ' = Submerged unit weight of soil. θ = Foundation rotation - radians. φ = Angle of internal friction for sand - degrees. ν = Poisson's ratio. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 89 Rev 3, August 2008 7 CALCULATION METHODS - DETERMINATION OF RESPONSES 7.1 General 7.1.1 The response of a jack-up unit is determined by combining the applied factored loading with a structural model to determine the internal forces in the members and the reactions at the foundations. These internal forces and reactions are compared with the factored resistances available to take up these loads to determine the safety of the unit. The loads consist of fixed loads (self weight and non-varying loads) and variable loads (see Section 3.2) together with hydrodynamic and wind loadings (see Section 4). The structural modeling is described in Section 5. The foundation resistance is described in Section 6. Section 8 provides the structural resistance and a methodology to check the adequacy of the various resistances to the acceptance criteria. 7.1.2 Two aspects of the response are to be distinguished and assessed separately. These are: a) The extreme response. The maximum calculated response to the design environment occurring at a particular instant in time, which is compared with the acceptance criteria. See Sections 7.2 and 7.3. b) Fatigue. The cumulative effect of stress/strain cycling, which is used to estimate the fatigue lives of steel components (see Section 7.4). 7.1.3 For typical jack-up assessments, the time-varying nature of the wave loading will amplify the quasi-static responses and must be considered. The extreme response can be assessed either by a quasi-static analysis procedure (Section 7.2) including an inertial loadset (Section 7.3.6) or by a more detailed dynamic analysis procedure (Section 7.3.7). 7.1.4 The dynamic amplification of the quasi-static response may not be significant for a given set of location parameters. The magnitude of the dynamic response is primarily influenced by the amount of wave energy at or near the natural period of the jack-up. The distribution of wave energy is at a maximum at the peak wave period and reduces for other periods. Thus the single most important parameter in the determination of the dynamic amplification of responses is the separation of the natural period of the jack-up from the peak period of the wave spectrum. Generally a large separation will produce a small dynamic amplification. As the separation decreases, the dynamic amplification will increase. These conclusions may be modified by effects such as wave-load cancellation and wave-current induced harmonics. 7.1.5 For many applications, the dynamic amplification may be determined using a simple, but empirical, method. This simple method is detailed in Section 7.3.6.1. Caution is advised when relying solely on results using this simple method. Specific guidance on the limitations of the method is given in Section 7.3.6.1. Because of its simplicity, the method detailed in Section 7.3.6.1 is recommended for an initial evaluation of the dynamic amplification. If the dynamic amplification is determined to be relatively small (see Section 7.3.6.1), or, if acceptance criteria are met, then random dynamic analysis is not required. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 90 Rev 3, August 2008 7.1.6 For many applications the dynamic effects may be included through the addition of an inertial loadset (see Section 7.3.6.1) to the environmental loads in a quasi-static analysis procedure. In this approach the inertial loadset may be determined using a simplified model of the jack-up. An appropriate detailed model of the jack-up may then be used to determine the detailed responses when the inertial loadset is applied together with the quasi-static environmental loads. 7.1.7 Appropriate combinations of gravity loads, wave/current loads and wind loads shall be applied as required by the acceptance criteria in Section 8. Load application is described in Section 5.7. Section 5.1 requires that the analysis is carried out for a range of environmental headings with respect to the unit such that the most onerous loading(s) for each major type of element in the structural system is(are) determined. The checks cover: Load Component Limit State Check Section Response Parameters(s)1 L note 2 Dn D E min max Strength of elements 8.1 Element load vectors3 Y Y4 Y Y Overturning 8.2 Overturning moment 5 5 Y Y stability Stabilizing moment Y Y Foundation capacity: 8.3 - preload 8.3.1 Vertical leg reaction Y Y Y Y - sliding 8.3.1 Vertical & Horizontal leg reactions Y Y Y Y - bearing 8.3.2/3 Vertical, Horizontal (& moment) leg reactions Y Y6 Y6 Y Y - displacement 8.3.4 Leg footing displacements and reactions Y Y6 Y6 Y Y Horizontal deflection 8.4 Hull displacement. Y Y6 Y6 Y Y Holding system loads 8.5 Holding system loads vectors Y Y6 Y6 Y Y where D, L, E and Dn are defined in the glossary at the end of section 7. Notes: 1. In all instances the responses are evaluated including the effects of deformation under dead loads (hull sag) and large displacement (P-Δ) effects. 2. Placed at most onerous center of gravity position. 3. The effects of leg offset to be added after global response analysis (see Section 5.4). 4. Consider minimum live (variable) load if this is more onerous. 5. Must be included in response calculation so P-Δ effects are included. 6. Worst case combination required. 7.2 Quasi-Static Extreme Response with Inertial Loadset 7.2.1 The most common method of analysis adopted for the determination of extreme responses is the deterministic, quasi-static wave analysis. Such an analysis shall be carried out in accordance with all relevant requirements of Sections 3 to 6. The maximum wave loading is determined by 'stepping' the maximum wave through the structure. The maximum wave is defined in Section 3.5.1.2 and the methodology for calculating the wave loading is described in Section 4.3. Various methods for determining the inertial loadset are given in Section 7.3.6. Load cases and combinations are discussed in Section 7.1.7. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 91 Rev 3, August 2008 The spudcan-foundation interface should normally be modeled as a pin joint. The inclusion of a degree of fixity is to be justified on a case by case basis. If foundation fixity is included it should generally be represented by a combination of horizontal, vertical and rotational springs (which may be coupled) at the spudcan, rather than by a rotational spring alone. (See also Sections 5.3, 6.3.4 and 7.3.5.2). 7.3 Dynamic Extreme Response 7.3.1 Factors Governing Dynamics Dynamic amplification of the structural response must be taken into account (see Figure 7.1). Determination of dynamic response requires the incorporation of two separate items in the analysis: a) The dynamic characteristics of the structural system formed by the jack-up on its foundation, b) The characteristics of the environmental excitation. 7.3.2 The Structural System 7.3.2.1 The characteristics of the structural system are governed by the following aspects: a) The mass and mass distribution of the jack-up. This includes structural mass, mass of equipment and variable load on board, added mass due to the surrounding water and marine growth (if applicable), etc. The magnitudes and effective centers of mass of the various mass contributions are to be accurately determined. b) The overall (global) structural stiffness. This includes stiffness contributions from bending, shear deformation and axial straining of the legs, the leg to hull connections, the hull and the spudcan-foundation interface (if applicable). c) The damping. Damping contributions arise from the structural components and their connections, the water surrounding the legs and the soil underneath/around the spudcans. For further discussion of damping refer to Section 7.3.7. 7.3.2.2 The jack-up on its foundation represents a multi degree-of-freedom system. If the dynamic behavior is to be investigated in some detail it should also be modeled as such. The model may contain a number of nonlinear elements, notably the leg to hull connections and the spudcan-foundation interfaces. The influence of gravity (P-Δ/Euler) on the effective sway stiffness should be considered (see Section 5.5). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 92 Rev 3, August 2008 Figure 7.1: Recommended approach to determine extreme dynamic responses COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 93 Rev 3, August 2008 Due to the fact that the mass of the hull dominates the mass distribution, the global dynamic behavior of the jack-up may in some cases be determined from an idealized single degree-of-freedom system (see Section 7.3.6.1). Structural modeling at various levels of complexity is discussed in Section 5.6. 7.3.3 The Excitation 7.3.3.1 The characteristics of the environmental excitation are controlled by the fluctuating nature of the environmental factors - wind, current and waves. Currents change slowly compared with the natural periods at which jack-ups may oscillate and may hence be considered to be a steady phenomenon. Variations in wind velocity cover a wide range of periods, but the main wind energy is associated with periods which are considerably longer than the natural periods of jack-up oscillations. Therefore, in connection with jack-ups, the wind may generally be represented as a steady flow of air. The periods of waves typically lie between some 2-3 sec and some 20 sec. Since typical jack-up natural periods fall within this range, the primary source of excitation is from waves. Sea waves are generally not regular but random in nature unless swell is predominant. This has important implications which should be considered for both the dynamic excitation and the resulting dynamic response. As waves and currents interact these two environmental factors should be considered in combination when generating time varying hydrodynamic drag forces according to Section 4.3. 7.3.3.2 For the simplified dynamic analysis method of Section 7.3.6.1 based on a regular-wave deterministic quasi-static analysis the wave period is chosen to be 0.9Tp where Tp is the peak period of the wave spectrum for the extreme sea state. For random analyses (see Sections 7.3.6.2 and 7.3.7) the most probable peak period (Tp) of the wave spectrum for the extreme seastate will normally be selected when a 2 parameter Pierson-Moskowitz spectrum is used (Hs and Tp from site specific data and γ = 1 in Section 3.5.3). If a JONSWAP spectrum is used it is recommended that the peak period is considered to vary between plus and minus one standard deviation from the most probable peak period (Tp). Where the jack-up is sensitive to the wave period it is recommended that the range described in Section 3.5.1.2 or 3.5.3 is investigated as appropriate. In a deterministic calculation waves with a period close to the natural period of the jackup will give the largest dynamic amplification. It is therefore recommended that the wave associated with the highest natural period of the jack-up is also investigated. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 94 Rev 3, August 2008 7.3.4 The Dynamic Analysis A flow chart indicating the recommended dynamic analysis approach is shown in Figure 7.1. An initial estimate of the dynamic amplification can be obtained using the empirical methods described in Section 7.3.6.1. Techniques for performing random dynamic analyses can be categorized as frequency domain methods or time domain (simulation) methods or hybrids thereof; see Section 7.3.7. 7.3.5 The Natural Period(s) 7.3.5.1 The natural period of the jack-up on its foundation in the fundamental (or first) mode of vibration is an important indicator of the degree of dynamic response to be expected. The first and second vibrational modes are nearly always the surge and sway modes. The natural periods of these vibrational modes are usually close together; which of the two is the higher depends on which direction is less stiff. Where the period varies with environmental heading, care should be taken that the period used is applicable to the environmental direction being considered in the analysis. The third vibrational mode is normally a torsional mode, the three-dimensional effects of which may be important, in particular for environmental attack directions where the legs and hence wave loads are not symmetric about the direction of wave propagation. 7.3.5.2 If available, a finite element structural model containing the mass and stiffness properties of the jack-up may be used to obtain the various natural periods and mode shapes. This model should include the stiffness of the legs, hull and hull/leg connections according to Sections 5.6.4 to 5.6.6. If a finite element model containing only stiffness properties is available, then the global sway stiffness for the required headings may be determined by applying lateral unit loads to the hull. Normally the foundation will be considered pinned. This assumption may however be unconservative for situations in which: 1. The structure natural period is within a cancellation region of the base shear transfer function (see Commentary Section C7.4). 2. Significant foundation nonlinearities are expected at higher loading levels typical of dominant wave frequencies but not at lower loading levels typical of inertial frequencies. If either of these situations occur, and detailed foundation modeling is not available, it is recommended that the DAF's be calculated with fixity included and are then applied to a pinned model for response calculations. Where the foundation stiffness is included, lateral and vertical translational springs should be included together with the rotational springs. In any case the limitations on foundation loading according to Section 6.3.4 must be verified. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 95 Rev 3, August 2008 7.3.5.3 If such a capability is not available, the fundamental mode period may be estimated from the system described by: - an equivalent mass representing the mass of the jack-up and its distribution as referred to in Section 7.3.2; the equivalent mass is equal to the mass of the hull plus a contribution from the mass of the legs, including added mass, and is located at the center of gravity of the hull. - an equivalent spring representing the combined effect of the various stiffnesses mentioned in Section 7.3.2. The period is determined from the following equation applied to one leg: Tn = 2π (M / K ) e e where; Tn = highest (or first mode) natural period. Me = effective mass associated with one leg. = M N hull + Mla + M 2 lb Mhull = full mass of hull including maximum variable load. N = number of legs. Mla = mass of leg above lower guide (in the absence of a clamping mechanism) or above the center of the clamping mechanism. Mlb = mass of leg below the point described for Mla, including added mass for the submerged part of the leg ignoring spudcan. The added mass may be determined as Aeρ(CMe - 1) per unit length of one leg (for definitions of Ae and CMe see Section 4.6.6); ρ = mass density of water. Ke = effective stiffness associated with one leg (for derivation, refer to Commentary). = 3EI L3 1 P P 1 3L 4 12F I AF Y EI K L 2 3(EI) F LK K EI K L EI F K E g v 2 rs 2 r rs rh rs r rh − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ − − + ⎧⎨⎩ ⎫⎬⎭ − + + ⎧⎨⎩ ⎫⎬⎭ + ⎡ ⎣ ⎢⎢⎢⎢⎢ ⎤ ⎦ ⎥⎥⎥⎥⎥ 78I 2 . A F L s h When the soil rotational stiffness Krs at the spudcan-foundation interface is zero this may be re-written: = 3EI L3 1 P P 1 12F I AF Y 3EI F LK 7.8I A F L E g v 2 r rh s h 2 − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ + + + ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ Krs = rotational spring stiffness at spudcan-foundation interface. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 96 Rev 3, August 2008 Krh = rotational stiffness representing leg to hull connection stiffness (see below). Fr = factor to account for hull bending stiffness. = 1 1 2EI + ⎧⎨⎩ ⎫⎬⎭ YKrh H IH = representative second moment of area of the hull girder joining two legs about a horizontal axis normal to the line of environmental action. E = Young's modulus for steel. A = axial area of one leg (equals sum of effective chord areas, including a contribution from rack teeth - see Note to Section 5.6.4). As = effective shear area of one leg (see Figure 5.1). I = second moment of area of the leg (see Figure 5.1), including a contribution from rack teeth (see Note to Section 5.6.4). Y = distance between center of one leg and line joining centers of the other two legs (3 leg unit). = distance between windward and leeward leg rows for direction under consideration (4 leg unit) Fg = geometric factor. = 1.125 (3 leg unit), 1.0 (4 leg unit) Fv = factor to account for vertical soil stiffness, Kvs, and vertical leg-hull connection stiffness, Kvh (see below). = 1 1 EA LK EA LK vs vh + + ⎧⎨⎩ ⎫⎬⎭ Fh = factor to account for horizontal soil stiffness, Khs, and horizontal leg-hull connection stiffness, Khh (see below). = 1 1 2 6LK 2 6LK + + ⎧⎨⎩ ⎫⎬⎭ EA EA s hs s hh . . L = length of leg from the seabed reaction point (see Section 5.2.1) to the point separating M1a and M1b (see above). P = the mean force due to vertical fixed and variable loads acting on one leg. = M g N hull g = acceleration due to gravity. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 97 Rev 3, August 2008 PE = Euler buckling load of one leg. = α2EI α = the minimum positive non-zero value of αL satisfying: tan(αL) = (K K ) EI ( EI) (K K ) rs rh 2 rs rh + − ⎧⎨⎩ ⎫⎬⎭ α α Thus: when Krs = 0 and Krh = ∞, αL = π/2 and hence: PE = π 2 2 EI 4L when Krs = ∞ and Krh = ∞, αL = π and hence PE = π 2 2 EI L The hull to leg connection springs, Krh, Kvh and Khh represent the interaction of the leg with the guides and supporting system and account for local member flexibility and frame action. They should be computed with respect to the point separating M1a and M1b, as described above. The following approximations may be applied: Khh = ∞ Kvh = effective stiffness due to the series combination of all vertical pinion or fixation system stiffnesses, allowing for combined action with shockpads, where fitted. Unit with fixation system: Krh = combined rotational stiffness of fixation systems on one leg. = Fnh2kf where; Fn = 0.5, three chord leg; = 1.0, four chord leg h = distance between chord centers. kf = combined vertical stiffness of all fixation system components on one chord. Unit without fixation system: Krh = rotational stiffness allowing for pinion stiffness, leg shear deformation and guide flexibility. = Fnh2kj + k d 1 (2.6k d / EA ) u 2 u s + where; h = distance between chord centers (opposed pinion chords) or pinion pitch points (single rack chords). kj = combined vertical stiffness of all jacking system components on one chord. d = distance between upper and lower guides. ku = total lateral stiffness of upper guides with respect to lower guides. As = effective shear area of leg. 7.3.5.3 The above equations for estimating the fundamental natural period are approximate and ignore the following effects: - more realistic representation of possible fixity at the spudcan-foundation interface in the form of (coupled) horizontal, vertical and rotational spring stiffnesses. - three dimensional influences of the system as compared with the two-dimensional single leg model. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 98 Rev 3, August 2008 7.3.5.4 Due to uncertainty in the parameters affecting the natural period the calculated natural period(s) will also be uncertain. The natural period(s) used in the dynamic analysis should be selected such that a realistic but conservative value of the dynamic response is obtained for the particular application envisaged. Care should be taken to ensure that the maximum dynamic amplification is not selected as coincident with a cancellation period causing minimum environmental loading. The potential for increased response due to shortcrested waves should be considered (see Section 7.3.7.5). For further details refer to the Commentary Section C7.4 and Figure C7.1. 7.3.6 Inertial Loadset Approaches In inertial loadset approaches the dynamic response is represented in a global quasi-static response model by either a distributed inertial loadset or an equivalent point load applied at the hull center of gravity. The inertial loadset may be derived from the simple approach described in Section 7.3.6.1 or from the more complex methods discussed in Sections 7.3.6.2 and 7.3.6.3. 7.3.6.1 The classical SDOF analogy This representation assumes that the jack-up on its foundation may be modeled as an equivalent mass-spring-damper mechanism; see Section 7.3.2. The (highest) natural period of the vibrational modes may be determined as described in Section 7.3.5. The torsional mode and corresponding three-dimensional effects cannot be included in this representation. The single degree-of-freedom (SDOF) method is fundamentally empirical because (1) the wave-current loading does not occur at the mass center and (2) the loading is nonperiodic (random) and non-linear. It should also be noted that all global and detailed response parameters are not equally amplified. The method described below will generally lead to a reasonable approximation of the jack-up's real behavior and has been calibrated against more rigorous methods. The following cautions are noted when using the SDOF method: 1. If the ratio of the jack-up natural period to the wave excitation period, Ω, is less than 0.5 and the current is 'relatively small' the SDOF method should give reasonably accurate results when compared to a more rigorous analysis. 2. If Ω is greater than 0.5, the relative position of the jack-up natural period within the base shear transfer function should be checked. If the natural period falls near a wave force peak, then the SDOF method may be unconservative because it ignores forcing at other than the full wave excitation period. Note that the calculation of natural periods should include a range of periods to account for a reasonable estimate of foundation fixity (see Section 7.3.5.2). 3. The SDOF method may be unconservative for cases with relatively high currents. If the results of the assessment are close to the acceptance criteria further detailed analysis is recommended. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 99 Rev 3, August 2008 The ratio of (the amplitudes of the) dynamic to the quasi-static response as a function of frequency (ω) or period (T) of steady state, periodic and sinusoidal excitation is calculated as the classical dynamic amplification factor (DAF): DAF = [ ] 1 (1− Ω2 )2 + (2ζΩ)2 where; Ω = Wave Excitation frequency Jack − up natural frequency = ω ω n = Jack - up natural period Wave excitation period T T = n ζ = Damping ratio or fraction of critical damping = (% Critical Damping)/100, ≤ 0.07. T = 0.9Tp. Tp = most probable peak wave period. Tn = the jack-up natural period as derived in 7.3.5. The damping parameter ζ in this model represents the total of all damping contributions (structural, hydrodynamic and soil damping). For the evaluation of extreme response using the SDOF method a value not exceeding 0.07 is recommended. The calculated DAF from the SDOF method is used to estimate an inertial loadset which represents the contribution of dynamics over and above the quasi-static response in accordance with Figure 7.1. This inertial loadset should be determined as follows and applied at the hull (center of gravity) in the down-wind direction: Fin = (DAF - 1) BSAmplitude where; Fin = Magnitude of the inertial loadset for use in conjunction with the SDOF method. BSAmplitude = Amplitude of quasi-static Base Shear over one wave cycle. = (BS(Q - S)Max - BS(Q - S)Min)/2 BS(Q - S)Max = Maximum quasi-static wave/current Base Shear. BS(Q - S)Min = Minimum quasi-static wave/current Base Shear. Note: The above equation is part of a calibrated procedure and should not be altered. A more general inertial loadset procedure, using the results from random analysis, is described in Section 7.3.6.3. 7.3.6.2 Other SDOF approaches An alternative use of the SDOF method is to apply the entire DAF function for all frequencies (periods), rather than a single point DAF at one frequency. This method reflects the random wave plus current excitation more correctly. Execution of this procedure is as per the relevant parts of Section 7.3.7. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 100 Rev 3, August 2008 7.3.6.3 Inertial loadset based on random analysis The inertial loadset may be derived from random frequency or time domain analysis according to the recommendations of Section 7.3.7. The inertial loadset should be such that it increases the responses of the deterministic quasi-static analysis by the same ratios as those determined between the random quasi-static (zero mass) analysis and the random dynamic analysis (see Figure C7.B.1) In such cases the structural model (used for dynamic analysis) may be simplified and does not need to contain all the structural details, but will nevertheless be a multi degree-of-freedom model. The approach to the modeling and determination of the inertial loadset is described further in the Commentary, Section C7.B.2. The inertial loadset can be determined to model the effect of dynamic amplification in a more realistic manner as required. The simplest alternative uses a single point force to match inertial overturning moment effects as shown in the Commentary, Section C7.B.2. However the use of a distributed inertial loadset is considered more representative and will therefore provide a more accurate description of the component dynamic amplification effects as well as global response amplification. The distribution of the loadset is based on the fundamental sway modes and mass distribution. Note that the use of a distributed inertial loadset is recommended for units where a significant proportion of the total mass (including fluid added mass) acts at a location other than the hull center of gravity. The mathematical procedure for calculation of the distributed loadset is given in Figure 7.2. A brief description of the calculation process is as follows: Step 1 Perform random response analysis using a wave attack direction along the selected main axis (x or y) and establish the global response dynamic amplification factors for base shear and overturning moment, whereby the dynamic amplification factors are defined as DAF3 = MPMEdyn/MPMEstatic. Step 2 Establish a set of two simultaneous equations using combinations of 2-D mode shapes, nodal masses and unknown modal scalar, which match the inertial base shear and moment along the selected main axis. Solve this equation set to determine the two modal multipliers. Step 3 Establish the (2-D) inertial loadset Fin by a combination of the selected structural mode shapes (ϕ1, ϕ2), scalar multipliers (α, β) and nodal masses (M), i.e. Fin = α ϕ1M + β ϕ2M. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 101 Rev 3, August 2008 Figure 7.2 - Procedure for calculation of distributed inertial loadset (2-D response) 7.3.7 Detailed Dynamic Analysis Methods Fully detailed random dynamic analysis will be necessary indicated in Figure 7.1. Random dynamic analysis may be performed in the time or in the frequency domain. 7.3.7.1 The waves may be modeled as a linear random superposition model which is fully described by the wave spectrum (see Section 3.5.3). The statistics of the underlying random process are gaussian and fully known theoretically. An empirical modification around the free surface may be needed to account for free surface effects. This, together with the fact that drag forces are a nonlinear (squared) transformation of wave kinematics, makes the hydrodynamic force excitation always nonlinear. As a result, the random excitation is non-gaussian. The statistics of such a process are generally not known theoretically, but the extremes are generally larger than the extremes of a corresponding gaussian random process. For a detailed investigation of the dynamic behavior of a jack-up the non-gaussian effects must be included. A number of procedures for doing this are presented in the Commentary. 7.3.7.2 The spudcan-foundation interface should normally be modeled as a pin joint in the absence of justifiable site-specific foundation fixity information, but see Section 7.3.5.2. If foundation fixity is included, it should be represented by a combination of horizontal, vertical and rotational springs. Coupling of the springs is preferable. In any case the limitations on foundation loading according to Section 6.3.4 must be verified. 7.3.7.3 When the random displacements of the submerged parts are small and the velocities are significant with respect to the water particle velocities the damping is not well represented by the relative velocity formulation in Morison's equation, which will tend to overestimate the damping and underpredict the response. A criterion for determining the applicability of the relative velocity formulation is given in Section 4.3.2. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 102 Rev 3, August 2008 7.3.7.4 Table 7.1 summarizes appropriate percentages of global critical damping for the various damping sources which should be summed to provide the total global damping as a percentage of critical damping. Damping source Global damping not to exceed (% of critical damping) Structure, holding system, etc. 2% Foundation 2% or 0%(1) Hydrodynamic 3% or 0%(2) Notes: 1. Where a non-linear foundation model is adopted the hysteresis foundation damping will be accounted for directly and should not therefore be included in the global damping. 2. In cases where the relative velocity formulation may be used (α = 1 in Section 4.3.2) the hydrodynamic damping will be accounted for directly and should not therefore be included in the global damping. Table 7.1 - Recommended damping from various sources 7.3.7.5 The effects of directionality and wave spreading may be considered in any dynamic analysis. It is recommended that a comparison be made between the Base Shear Transfer Function (BSTF) for the chosen 2-D (long crested/unspread) analysis direction and the 3- D (short crested/spread) BSTF to determine whether the selected direction is unconservative. Optimally the direction of the 2-D seastate should be chosen to obtain a match with the 3-D BSTF for the entire wave spectrum. If this is not possible the match between the spread and unspread BSTFs should be good at the natural period. A 3-D BSTF, H3D, can be generated from a set of 2-D BSTFs, H2D, by the following expression: H3D(ω) = [H ] d D n 2 2 2 0 2 (ω,θ) cos (θ) θ π ∫ where: ω = Wave excitation frequency θ = Angle between 2-D BSTF and dominant direction of 3-D BSTF n = Power constant of spreading function ≥ 2.0 for fatigue analysis ≥ 4.0 for extreme analysis A simple approximation to the incorporation of wave spreading into inertial load calculations is to perform a 2-D analysis with the wave approach angle which is between the two approach angles which give the maximum and minimum forces at the cancellation and reinforcement points (see Figure C7.1 in the Commentary). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 103 Rev 3, August 2008 7.3.7.6 Tables 7.2 and 7.3 respectively identify the most important factors associated with each type of analysis method and with each approach to determining the extreme responses. Further details of the methods are provided in the Commentary. 7.3.8 Acceptance Criteria The results of a dynamic extreme response analysis shall be assessed against the acceptance criteria described in Section 8. The required load factors should be introduced when combining the component loads into total load combinations. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 104 Rev 3, August 2008 Method Recommendations Frequency Domain Consider linearization assumptions with respect to: - wave-current loading (quadratic dependence on particle velocity and finite wave ht). - structural non-linearity. Generate random sea from at least 200 components and use divisions of equal frequency. Note: fewer frequency components may be used provided that the divisions are shown to be sufficiently small around the wave period, the natural period & periods associated with reinforcement and cancellation. Time Domain Generate random sea from at least 200 components and use divisions of generally equal energy. It is recommended that smaller energy divisions are used in the high frequency portion of the spectrum, which will generally contain the reinforcement and cancellation frequencies. Each wavelet should be taken to disperse with its own linear dispersion relationship [12] Check validity of wave simulation: - correct mean wave elevation - standard deviation = (Hs /4) ± 1% - -0.03 < skewness < 0.03 - 2.9 < kurtosis < 3.1 - Max crest elevation = (Hs/4)√{2ln(N)} -5% to +7.5% where N is the number of cycles in the time series being qualified, N ≈ Duration / Tz Integration time-step less than the smaller of: Tz/20 or Tn/20 where; Tz = the zero-upcrossing period of the wave spectrum Tn = the jack-up natural period (unless it can be shown that a larger time-step leads to no significant change in results) Avoid transients in 'run-in' (≥100 secs). Ensure simulation length OK for method chosen to determine the Most Probable Maximum Extreme (MPME) response(s). Note: The MPME is defined in Table 7.3 Table 7.2 - Recommendations for application of dynamic analysis methods (see Commentary) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 105 Rev 3, August 2008 Method Recommendations General Define the Most Probable Maximum Extreme (MPME) as the extreme with a 63% chance of exceedence (typically this is the mode or highest point on the probability density function (PDF)).This is approximately equivalent to the 1/1000 highest peak level in a 3-hour storm. Frequency Domain Use mean & standard deviation to determine drag-inertia parameter and use Figure C7.B.6 in Commentary Section C7.B.2.1. Time Domain Use mean & standard deviation to determine drag-inertia parameter and use Figure C7.B.5 or Figure C7.B.6 in Commentary Section C7.B.2.1. Simulation time of at least 60 minutes usually required to obtain stable standard deviation. or Fit Weibull distribution to distribution, for 3-hour probability level. Take results as average of MPME's from ≥ 5 simulations. Each input wave simulation to be of sufficient length for recommendations of Table 7.2 to be met (usually at least 60 minutes). See Commentary C7.B.2.2. or Use multiple 3-hour simulations and use Gumbel distribution on the extreme from each simulation. Sufficient simulations (usually at least 10) are required to obtain stable MPME of responses. See Commentary C7.B.2.3. or Use Winterstein's Hermite polynomial model, with improvements by Jensen if Kurtosis > 5. Simulation of sufficient duration to provide stable skewness and kurtosis of responses (normally in excess of 180 minutes). See Commentary Section C7.B.2.4. Table 7.3 - Recommendations for determining MPME (see Commentary) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 106 Rev 3, August 2008 7.4 Fatigue 7.4.1 General The fatigue of jack-ups should be considered for all new locations and operations. Jackups are mobile structures, generally operating in a wide range of water depths, therefore the location of the fatigue sensitive areas may vary (see Section 7.4.3). This means that fatigue damage at any member/joint or other component may not occur equally throughout the life of the unit and tends to complicate the fatigue problem. If the original analysis carried out for the unit demonstrates that lives of critical components are adequate then a unit may not require a separate analysis if on location for a period of less than one year provided that adequate proof from a recent inspection exists showing that the unit is behaving as originally predicted. If no original analysis and/or inspection proof is in existence then a separate analysis may be required for all operations in excess of one year. In extreme cases six months may be more appropriate if this period contains the rough winter season. Alternatively a recent assessment inspection, or proof that such an inspection (including detailed NDT) has been carried out may serve as a demonstration of the adequacy of the unit. 7.4.2 Fatigue Life Requirements A fatigue analysis, if undertaken, should ensure that all structural components have (remaining) fatigue lives of more than the greater of four times the duration of the assignment or 10 years. Different (reduced) fatigue life requirements may be justified for certain items on a case by case basis where structural redundancy or ease of access for inspection and repair permit. 7.4.3 Fatigue Sensitive Areas All structural members subject to fatigue loading are to be checked in the analysis, with emphasis on the following areas, which are likely to be the most critical. However, other areas should also be studied if they are potentially more critical: a) The leg members and joints in the vicinity of the upper and lower guides for the operating leg/guide location(s). b) The rack teeth of the chord. c) The leg members and joints adjacent to the waterline. d) The jack-frame/jackhouse and associated areas of the hull. e) The leg members and joints in the vicinity of the leg to spudcan connection. f) The spudcan to leg connection. Records of inspections, damage and repair for the unit may provide guidance in the selection of critical areas. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 107 Rev 3, August 2008 As mentioned the fatigue analysis should consider all loading conditions that may occurduring the period under consideration and for items c) through f) the cumulative damage due to transit loadings should also be included. 7.4.4 General Description of Analysis Suitable approaches to the analysis may be found in reference [13]. Equivalent approaches may be applied. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 108 Rev 3, August 2008 7 GLOSSARY OF TERMS - DETERMINATION OF RESPONSES A = Equivalent axial area of a leg (see Figure 5.1), including contribution from rack teeth (see note to Section 5.6.4). As = Effective shear area of one leg. BS = Base Shear. d = Distance between upper and lower guides. D = Self weight and non varying loads. DAF = Dynamic Amplification Factor. Dn = Inertial loads due to Dynamic response. E = Environmental loads. E = Young's modulus for steel. Fg = Geometric factor = 1.125 (3 leg unit), 1.0 (4 leg unit) Fh = Factor to account for horizontal soil stiffness, Khs, and horizontal leg-hull connection stiffness, Khh. Fin = Magnitude of inertial loadset. Fn = 0.5, three chord leg; = 1.0, four chord leg Fr = Factor to account for hull bending stiffness. Fv = Factor to account for vertical soil stiffness, Kvs, and vertical leg-hull connection stiffness, Kvh. g = Acceleration due to gravity. h = Distance between chord centers or pinion pitch points. Hdet = The wave height to be used for deterministic waveforce calculations, allowing for conservatisms in the theoretical predictions of higher order wave theories. = 1.60 Hsrp Hmax = The maximum deterministic wave height. = 1.86 Hsrp, generally. = 1.75 Hsrp, in Tropical Revolving Storm areas. Hs = Significant wave height (meters), including depth/asymmetry correction, according to Section 3.5.1.1. Hsrp = The assessment return period significant wave height for a 3 hour storm. H2D = 2-D base shear transfer function. H3D = 3-D base shear transfer function. I = Second moment of area of the leg (see Figure 5.1) including contribution from rack teeth (see note to Section 5.6.4). IH = Representative second moment of area of the hull girder joining two legs about a horizontal axis normal to the line of environmental action. kf = Combined vertical stiffness of all fixation system components on one chord. kj = Combined vertical stiffness of all jacking system components on one chord. ku = Total lateral stiffness of upper guides with respect to lower guides. Ke = The effective stiffness associated with one leg. Khh = Horizontal stiffness of leg-hull connection, generally infinite. Khs = Horizontal stiffness at the spudcan-foundation interface. Krh = Rotational stiffness representing the leg-hull connection. Krs = Rotational stiffness at the spudcan-foundation interface. Kvh = Vertical stiffness of leg-hull connection. Kvs = Vertical stiffness at the spudcan-foundation interface. L = Variable loads. L = Length of leg from the seabed reaction point (see Section 5.2.1) to the point separating M1a and M1b. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 109 Rev 3, August 2008 7 GLOSSARY OF TERMS - DETERMINATION OF RESPONSES (Continued) M = Nodal masses. Me = Effective mass associated with one leg. Mhull = Full mass of hull, including variable load. M1a = Mass of a leg above lower guide (in the absence of a clamping mechanism) or above the center of the clamping mechanism. M1b = Mass of leg below the point described for M1a, including added mass for the submerged part of the leg. MPME = Most Probable Maximum Extreme response(s). The extreme response with a 63% chance of exceedence; approximately equal to the 1/1000 highest peak level in a 3-hour storm. n = Power constant of spreading function. ≥ 2.0 for fatigue analysis. ≥ 4.0 for extreme analysis. N = Number of legs. N = Number of cycles. P = The mean force due to vertical dead weight and variable load acting on one leg. = M g N hull PE = Euler buckling load of one leg. = α2EI T = 0.9 Tp. Tass = Wave period associated with Hmax (also used with Hdet). Tn = Natural period of jack-up (subject to the precautions of Section 7.3.5.4). Tp = Peak period associated with Hsrp (also used with Hs). Tz = Zero-upcrossing period of the wave spectrum. Y = Distance between center of one leg and line joining centers of the other two legs (3 leg unit). = Distance between windward and leeward leg rows for direction under consideration (4 leg unit). α = The minimum positive non-zero value of αL satisfying: tan (αL) = ( ) ( ) ( ) K K EI EI K K rs rh rs rh + − ⎧⎨⎩ ⎫⎬⎭⎪ α α 2 α = Scalar multiplier used in establishing 2-D Fin. β = Scalar multiplier used in establishing 2-D Fin. ϕ1,ϕ2 = Structural mode shapes. Ω = ω/ωn = Tn/T. ρ = Mass density of water. θ = Angle between 2-D BSTF and dominant direction of 3-D BSTF. ω = Wave excitation frequency = 2π/T. ωn = Jack-up natural frequency = 2π/Tn. ζ = Damping ratio or fraction of critical damping. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 110 Rev 3, August 2008 8 ACCEPTANCE CRITERIA The acceptance checks in the following sections cover: - Structural strength (Section 8.1), - Overturning stability (Section 8.2), - Foundation capacity (preload, bearing, sliding displacement and punch-through) (Section 8.3), - Horizontal deflections (Section 8.4), - Loads in the holding system (Section 8.5), - Loads in the hull (Section 8.6) and - The condition of the unit (Section 8.7). Meeting acceptance criteria implies that the factored resistance is equal to or greater than the internal forces or reactions due to the application of the factored loads. 8.1 Structural Strength Check Note: Figure 8.1 provides a flowchart for member strength assessment. 8.1.1 Introduction 8.1.1.1 Code Basis The main basis for the structural strength check is the AISC 'Load and Resistance Factor Design (LRFD) Specification for Structural Steel Buildings' [14]. The AISC LRFD specification has been interpreted and, in some cases, modified for use in the assessment of mobile jack-up unit structures. Interpretation of the code has been necessary to enable a straight-forward method to be presented for the assessment of beam-columns of non 'I' section. Development of the code has been necessary in two areas as described below: a) A method has been established for dealing with sections constructed of steels with different material properties. b) A method has been established for the assessment of beam columns under biaxial bending to overcome a conservatism which has been identified in the standard AISC LRFD equations. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 111 Rev 3, August 2008 Figure 8.1: Flow chart for member strength assessment COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 112 Rev 3, August 2008 One particular type of member geometry which is not covered at all by AISC LRFD is the high R/t ratio tubular which usually has ring frame and/or longitudinal stiffeners. Recommendations for checking such members are given in Section 8.1.5 where the user is referred to an applicable code and guidance is given on suitable load and resistance factors. The resistance factors used in the AISC LRFD specification have been adopted. In addition to checking the strength of members, it may be necessary to check the strength of joints between members. Recommendations for joint checking are given in Section 8.1.6 where the user is referred to an applicable code and guidance is given on suitable load and resistance factors. 8.1.1.2 Limitations The structural strength check assessment described here is limited by the following criteria: a) The geometry of structural components and members, as defined in 8.1.2, must fall reasonably within the categories described in that section. b) In accordance with AISC LRFD Specification, Chapter A Para. A5, the minimum specified yield stress of the strongest steel comprising the components and members should not exceed: - 65 ksi (448 MN/m2) if (elasto-)plastic structural analysis is used to determine the member loads. For slender geometries plastic structural analysis is precluded, even if the yield stress is below 65 ksi. - 100 ksi (690 MN/m2) if elastic structural analysis is used to determine the member loads. For higher strength steels within the holding system, refer to Section 8.5. It should also be noted that the assessment has been tailored towards the types of analysis normally carried out for jack-ups. The detailed recommendations which follow focus particularly on closed section brace and chord scantlings in truss type legs. Geometries outside the limits of Sections 8.1.2 - 8.1.4 may be checked in accordance with the recommendations of Section 8.1.5. Notes: 1. Of necessity, many of the equations presented in Section 8.1 are dimensional. Such equations are quoted firstly in metric units (MN, m, MN/m2 etc.) and then in { } in North American imperial units (kips, inches, ksi, etc.). 2. Where the member geometry may contain components of part-tubular shape it is appropriate to consider their dimensions in terms of radius and thickness (rather than diameter and thickness), and hence relevant equations have been converted to this format. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 113 Rev 3, August 2008 3. The AISC LRFD source equations/text are identified between [ ]. 4. The terms in the equations are defined where they appear. A glossary is also provided at the end of Section 8. 8.1.2 Definitions 8.1.2.1 Structural Members and Components a) Structural Members For the purposes of strength assessment, it is necessary to consider the structure as comprised of structural members. Typically each structural member could be represented by a single finite element in an appropriate finite element model of the structure. Examples of members would include braces and chords in truss type legs, box or tubular legs and plating which forms a piece of structure for which the properties can readily be calculated. The strengths of structural members are to be assessed according to Section 8.1.4 with the exception of structural members exceeding any of the following provisions which should be assessed according to Section 8.1.5. i) A plain tubular with R/t > 44,815/Fy {Imperial: 6,500/Fy} [Table A-F1.1] ii) Any tubular with ring stiffeners with or without longitudinal stiffeners. iii) Tubulars with longitudinal stiffeners where; R/t > 11,375/Fy {Imperial: 1,650/Fy} [Table B5.1] b) Structural Components A structural component is defined as a part of a structural member (see Figure 8.2). Typically, structural components are pieces of plating or tubulars such as the plates, splittubulars and rack pieces forming a jack-up chord, or the stringers on a panel. Note that it is not always appropriate to consider fundamental structural parts as components. A plain tubular, for example is better analyzed as a member. A component should not consist of more than one material. 8.1.2.2 Stiffened and Unstiffened Components A component which is stiffened along both edges is denoted a stiffened component. A component which is supported along only one edge is denoted an unstiffened component. Typically all the components forming parts of chord sections may be regarded as stiffened. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 114 Rev 3, August 2008 8.1.2.3 Compact, noncompact and slender sections Steel sections are divided into compact sections, noncompact sections and sections with slender compression elements. Compact sections are capable of developing a fully plastic stress distribution before the onset of local buckling. Noncompact sections can develop the yield stress in compression components before local buckling occurs, but will not resist inelastic local buckling at the strain levels required for a fully plastic stress distribution. Slender compression components buckle elastically before the yield stress is achieved. Where a distinction is required between these categories, appropriate limiting slenderness ratios have been stipulated. 8.1.3 Factored Loads Factored loads in structural components and members are to be determined in accordance with the previous sections, using the most onerous condition for each structural component or member. Each structural component or member meet the acceptance criteria for the member loads (i.e. axial load, moments and, if applicable, shears and torsion) resulting from the application to the jack-up of the factored load Q (as described in 5.7) where; Q = γ1.D + γ2.L + γ3(E + γ4.Dn) and γ1 = 1.0 γ2 = 1.0 γ3 = 1.15 (provisional - see Section 1.8) γ4 = 1.0 D = The weight of structure and non-varying loads including: - Weight in air including appropriate solid ballast. - Equipment. - Buoyancy. - Permanent enclosed liquid. L = The maximum variable load (gravity adds to environmental loads) or minimum variable load (gravity opposes environmental loads) positioned at the most onerous center of gravity location applicable to extreme conditions as specified in Section 3.2. E = The load due to the assessment return period wind, wave and current conditions (including associated large displacement effects). Dn = The inertial loadset which represents the contribution of dynamics over and above the quasi-static response as described in Section 7.3.6 (including associated large displacement effects). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 115 Rev 3, August 2008 8.1.4 Assessment of Members - excluding stiffened and high R/t ratio tubulars 8.1.4.1 General interaction equations Each structural member within the scope of Section 8.1.2 shall satisfy the following conditions: If Pu/φaPn > 0.2 P P 8 9 M M M M u 1.0 a n uex b nx uey b ny 1 φ φ φ η η η + ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ⎡ ⎣ ⎢⎢ ⎤ ⎦ ⎥⎥ ≤ [Eq. H1-1a] else P P M M M M u 1.0 a n uex b nx uey b ny 1 2φ φ φ η η η + ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ⎡ ⎣ ⎢⎢ ⎤ ⎦ ⎥⎥ ≤ [Eq. H1-1b] where; Pu = applied axial load Pn = nominal axial strength determined in accordance with Section 8.1.4.2 (tension) and 8.1.4.3 (compression). Muex,Muey = effective applied bending moment determined in accordance with Section 8.1.4.4 (tension) and 8.1.4.5 (compression). Mnx,Mny = nominal bending strength determined in accordance with Section 8.1.4.6. φa = Resistance factor for axial load = 0.85 for [Eq. E2.1] compression and 0.90 for tension [Eq. D1.1]. φb = Resistance factor for bending = 0.9 [Ch. F1.2] η = Exponent for biaxial bending, a constant dependent on the member cross section geometry, determined as follows: i) For purely tubular members, η = 2.0 ii) For doubly symmetric open section members, η = 1.0 iii) For all other geometries, the value of η may be determined by analysis as described in Section 8.1.4.7 but shall not be less than 1.0. In lieu of analysis, a value of η equal to 1.0 may be used. The interaction equations can be used in a reduced form if one or two of the three load ratio terms in the equation are zero. Alternatively, the more complex interaction formulations given in Section C8.1.4.7 of the Commentary may be used where applicable. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 116 Rev 3, August 2008 8.1.4.2 Nominal Axial Strength of a Structural Member in tension Pn For a member comprising more than one component, the nominal tensile strength lies between the maximum individual tensile strength of any one component, and the sum of all the individual tensile strengths. The nominal tensile strength of a tension component shall be the lower value from the following equations: a) Pni = FyiAi b) Pni = 5 6 FuiAi where; Ai = area of component Fyi = specified minimum yield stress of component (or specified yield strength where no yield point exists) Fui = specified minimum tensile (ultimate) strength of component Pni = component nominal axial tensile strength This assumes that for members in jack-up units the net section is equal to the gross section [Eq's. D1.1 and D1.2]. The total member nominal tensile strength shall be: Pn = FminΣAi with the resistance factor φt = 0.90 [Eq. D1.1] where Fmin is the smallest value of Fyi or 5 6 Fui of all the components. Note: If for any component the nominal strength is significantly different from the nominal strengths of other components, the formulation above may be conservative and alternative rational methods may be applied. An example is given in the Commentary. 8.1.4.3 Nominal Axial Strength of a Structural Member in Compression Pn So long as local buckling of the components of a member is not the limiting state, the member can be treated for global loads only. Should local buckling dominate, the loads in the components must be considered. Therefore, in determining the nominal axial strength of a member in compression, a local buckling check must first be applied. Check: Local buckling The structural components which make up the cross section of a compact or noncompact section must satisfy the following criteria [Table B5.1]: i) For rectangular components stiffened along both edges bi/ti ≤ 625/ (F F ) yi r − {Imperial: bi/ti ≤ 238/ (F F ) yi r − } COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 117 Rev 3, August 2008 ii) For rectangular components stiffened along one edge bi/ti ≤ 250/ (F ) yi {Imperial: bi/ti ≤ 95/ (F ) yi } iii) For tubular sections R/ti ≤ 11380/Fyi {Imperial: R/ti ≤ 1650/Fyi} where; bi = width of a rectangular component ti = thickness of a rectangular component or tube wall R = outside radius of the tube or tubular component Fr = residual stress due to welding (114 MPa, {16.5 ksi}) Members containing rectangular and tubular sections which do not meet this criteria are considered to be slender and are treated in 8.1.4.3 b) for local buckling. a) Strength assessment for Compact and Noncompact Sections The nominal axial strength of a structural member subject to axial compression and within the above stipulated restrictions regarding cross section shall be determined from the following equations: Pn = A Fcr [Eq. E2.1] Fcr = (0.658λc2) Fyeff For λc ≤ 1.5 [Eq. E2.2] Fcr = 0877 2 . λc ⎧⎨⎩ ⎫⎬⎭ Fyeff For λc > 1.5 [Eq. E2.3] where; A = gross area of section (excluding rack teeth of chords) λc = K r F E ι yeff π ⎧⎨⎩ ⎫⎬⎭ 1 2 for max. Kι/r from all directions [Eq. E2.4] ι = unbraced length of member: - face to face for braces - braced point to braced point for chords - longer segment length of X-braces (one pair must be in tension, if not braced out of plane) r = radius of gyration, based on gross area of section. E = material Young's modulus (200,000 MN/m2 {29,000 ksi}). Fyeff =effective material yield stress, to be taken as the minimum of (specified) yield stress or 5/6 (ultimate stress) of all components in the member unless rational analysis shows that a higher value may be used. K = effective length factor. Figure 8.3 provides generally recommended values for K. For the specific case of jack-up truss legs, the value of K shall be taken as follows [Table C-C2.1], unless alternative values are shown applicable by rational analysis: Assumed boundary conditions Chord members 1.0 pinned-pinned K-Braces & span breakers 0.8 between pinned-pinned X-Braces 0.9 and fully built-in Complete legs 2.0 pinned-sliding COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 118 Rev 3, August 2008 b) Strength Assessment for Members with Slender Components The nominal axial strength of a structural member subject to axial compression and outside the restrictions for a) above shall be determined from the following equations. Pn = A Fcr where; Fcr = Q(0.658Qλc2)Fyeff for λc Q ≤ 1.5 [Eq. A-B5-11] Fcr = 0877 2 . λ c ⎧⎨⎩ ⎫⎬⎭ Fyeff for λc Q > 1.5 [Eq. A-B5-13] where λc is defined in Section 8.1.4.3 a) and Q is determined from the following: i) For members comprising entirely of stiffened components [A-B5.3.b and A-B5.3.c]: Q = Qa where; Qa = Ae/A [Eq. A-B5-10] and Ae is the section effective area found from: Ae = Σ bei ti (excluding rack teeth of chords) with bei = 856t 1 i 170 i i i i i f b t f b − ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ≤ ( / ) {Imperial: bei = 326 1 t 64 9 f b t f b i i i i i i − ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ≤ . ( / ) } [Eq A-B5-7] and fi is the calculated elastic stress in the component where, for the analysis, the member area is based on the actual cross sectional area but with elastic section modulus and radius of gyration based on effective area. ii) For members comprising of stiffened and unstiffened components [A-B5.3.b and A-B5.3.c]: Q = Qa Qs where Qa is determined from Section 8.1.4.3 b) i) but with the additional check that fi for the stiffened component must be such that the maximum compressive stress in the unstiffened component does not exceed φcFcr with Fcr defined in Section 8.1.4.3 b) with Q = Qs and φc = 0.85 or φbFyeffQs with φb = 0.90. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 119 Rev 3, August 2008 Qs is the lowest value for all components in the member which are stiffened along one edge determined from the following: For 250/ Fy < bi/ti < 460/ Fy {Imperial: 95/ Fy < bi/ti < 176/ Fy } Qs = 1.415 - 0.00166(bi/ti) Fy {Imperial: 1.415 - 0.00437(bi/ti) Fy } [Eq. A-B5-3] For bi/ti ≥ 460/ Fyi {Imperial: bi/ti ≥ 176/ Fyi } Qs = 137,900/[Fyi(bi/ti)2] {Imperial: Qs = 20,000/[Fyi(bi/ti)2]} [Eq. A-B5-4] Note: The implication of this section is that the critical components in the member will be the unstiffened components. If these buckle, then the assumed buckling lengths and hence strengths for the stiffened components will then be wrong, hence invalidating the original assumptions. This assumes that the unstiffened components are placed in the member to reduce the buckling length of the major components. iii) For members comprising a tube alone and: 11,375/Fy < R/t < 44,815/Fy {Imperial: 1,650/Fy < R/t < 6,500/Fy} Q = 3790 2 F R t 3 y( / ) + {Imperial: Q = 550 2 F R t 3 y( / ) + } [Eq. A-B5-9] 8.1.4.4 Effective Applied Moment for Members in Tension; Mue (Muex,Muey) In many cases, the effective applied moments used in the interaction equations will not be equal to applied moments obtained in a structural analysis. This can be due to the type of structural model and /or the effective length effect on buckling. The following procedures shall be followed for the determination of the effective applied moment. The effective applied moment for a member under axial tension shall be taken to be equal to the applied moment from an analysis including global P-Δ effects and accounting for local loading. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 120 Rev 3, August 2008 8.1.4.5 Effective Applied Moment for Compression Members; Mue (Muex,Muey) The effective applied moment for a member under axial compression shall be taken to be: Mue = B Mu [Eq. H1.2] where; Mu is the applied moment determined in an analysis which includes global P- Δ/hull-sway effects and accounts for local loading. When eccentricity is not incorporated in the model, the equation for Mue should be modified to include pue due to the eccentricity, e, between the elastic and plastic neutral axes. Note: When the member considered represents the leg the requirement to include P-Δ effects in the global analysis means that the provisions of ii) below apply. and i) Where the individual member loads are determined from a first order linear elastic analysis i.e. the equilibrium conditions were formulated on the undeformed structure, (For example a linear analysis of a detailed truss type leg, using external loads determined from a second order analysis of a simplified global model): B = C P P m u E ( / ) . 1 10 − ≥ [Eq. H1-3] where: PE = (π2r2AE)/(Kι)2 with K ≤ 1.0 and PE is to be calculated for the plane of bending. A is defined in Section 8.1.4.3 a) and r is the radius of gyration for the plane of loading. Cm = a coefficient whose value shall be taken as follows [Ch. H1.2a]: i) For members not subject to transverse loading between their supports in the plane of bending Cm = 0.6 - 0.4 (M1/M2) [Eq. H1-4] where M1/M2 is the ratio of the smaller to the larger moments at the ends of that portion of the member unbraced in the plane of bending under consideration. M1/M2 is positive when the member is bent in reverse curvature, negative when bent in single curvature. ii) For members subjected to transverse loading between their supports, the value of Cm can be determined from rational analysis. In lieu of such analysis, the following values may be used: For members whose ends are restrained against sidesway Cm = 0.85 For members whose ends are unrestrained against sidesway Cm = 1.0 ii) Where the individual member loads are determined from a second order analysis i.e. the equilibrium conditions were formulated on the elastically deformed structure so that local P-Δ loads were also included in the analysis: B = 1.0 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 121 Rev 3, August 2008 8.1.4.6 Nominal Bending Strength; Mn (Mnx, Mny) The calculation of nominal bending strength is based on the plastic properties of the section. The practice allows for hybrid sections built up from components of different yield strengths. Standard techniques shall be applied to obtain a section plastic moment in the absence of axial load, Mp, based on the individual component values which are the lesser values of Fyi and 5/6 Fui (an example is given in the Commentary). Lateral torsional buckling and local buckling of components must be considered. If both tensile and compressive yielding occur during the same load cycle, it shall be demonstrated that the structure will shake down without fracture. Check: Lateral torsional buckling (Not applicable to tubulars) The cross sectional geometry of a member subjected to bending shall be examined for susceptibility to the limit state of lateral torsional bucking. The member cross section must satisfy the following criteria for compact sections for the nominal bending strength to be assessed under Sections 8.1.4.6 a) or 8.1.4.6 b). Lb/ry ≤ 25860 (JA) /M p {Imperial: Lb/ry ≤ 3750 p (JA) /M } [Table A-F1.1] where; Lb = Laterally unbraced length; length between points which are either braced against lateral displacement of the compression flange or braced against twist of the cross section. ry = Radius of gyration about the minor axis. A = Cross sectional area. J = Torsional constant for the section Sections which do not satisfy this criteria are susceptible to lateral torsional buckling and are treated as having slender compression components as in Section 8.1.4.6 c). Check: Local buckling The cross sectional geometry of a member subjected to bending is to be examined for susceptibility to the limit state of local bucking. If local buckling is deemed to be the limit state, the nominal bending strength shall be reduced in accordance with the following paragraphs. Members with particularly slender components are covered in Section 8.1.4.6c). For this check it is necessary to identify web components and flange components. This can be done by visual inspection, with knowledge of the major and minor axes. For example, in a split-tubular, opposed rack chord, the rack plate would be a suitable web component, and the split tubulars flanges. For a teardrop chord, the rack and side plates would be web components, and the back plate the flange. In cases of doubt, components shall be checked as both web and flange. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 122 Rev 3, August 2008 a) Compact Sections For members in which all the components sections satisfy the following [Table B5.1]: i) For rectangular components stiffened along both edges bi/ti ≤ λp where; λp = 500/ (F ) yi {Imperial: λp = 190/ (F ) yi } ii) For rectangular components stiffened along one edge bi/ti ≤ λp where; λp = 170/ (F ) yi {Imperial: λp = 65/ (F ) yi } iii) For tubular sections 2R/t ≤ λp where; λp = 14270/Fyi {Imperial: λp = 2070/Fyi} The nominal bending strength is given by the plastic bending moment of the whole section Mn = Mp [Eq-A-F1-1] where Mp is derived as discussed above. Note: Where significant plastic hinge rotations are required the section must remain stable after rotation through an appreciable angle. In such cases, to achieve this requirement, the limitations of ii) and iii) above should be reduced to: ii) λp = 135/ (F ) yi {Imperial: λp = 52/ (F ) yi } iii) λp = 11000/Fyi {Imperial: λp = 1600/Fyi} b) Noncompact Sections For members in which all the components do not satisfy the previous criteria but satisfy the following [Table B5.1]: i) For rectangular components stiffened along both edges bi/ti ≤ λr where; λr = 625/ (F F ) yi r − {Imperial: λr = 238/ (F F ) yi r − } Fr = 114 MN/m2 {16.5 ksi} residual stress ii) For rectangular components stiffened along one edge bi/ti ≤ λr where; λr = 278/ (F F ) ywj r − {Imperial: λr = 106/ (F F ) ywj r − } Fywj = web component yield stress. Fr = 114 MN/m2 {16.5 ksi} residual stress. iii) For tubular sections 2R/t ≤ λr where; λr = 61850/Fyi {Imperial: λr = 8970/Fyi} COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 123 Rev 3, August 2008 The nominal bending strength is given by an interpolation between the plastic bending moment and the limiting buckling moment: Mn = Mp - (Mp- Mr) λ λ λ λ − − ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ p r p h [Eq. A-F1.3] where; Mp = Section Plastic Moment. h = subscript referring to the component which produces the smallest value of Mn. λ = b/t or 2R/t as applicable for component h. λp is determined for component h from 8.1.4.6 a). λr is determined for component h from 8.1.4.6 b). Mr is the limiting buckling moment of the section defined as follows: For bending of non-tubular sections about the major axis, the lesser of Mr = Fl S (flange buckling) [Table A-F1.1] Mr = ReFyfjS (web buckling) [Table A-F1.1] where; Fl = the smaller of (Fyfj – Fr) and Fywj S = minimum section elastic modulus for plane of bending under consideration. For bending of non-tubular sections about the minor axis; Mr = FyfjS (flange buckling) [Table A-F1.1] For bending of tubular sections: [Table A-F1.1] Mr = 2068 R t F S / y + ⎧⎨⎩ ⎫⎬⎭ {Imperial: Mr = 300 R t F S / y + ⎧⎨⎩ ⎫⎬⎭ } Fyfj = yield stress of flange component. Re = hybrid girder reduction factor [A-G2] = 1.0 if components are of the same material otherwise: = [12 + ar (3m – m3)] / (12 + 2 ar) ≤1.0 ar = ratio of total web area to area of compression flange. m = ratio of web component yield stress to flange component yield stress which gives smallest value of Re. c) Slender Sections The nominal bending strength of members including components which do not satisfy the above criteria for compact and noncompact sections or for lateral torsional buckling shall be determined in accordance this section. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 124 Rev 3, August 2008 The nominal bending strength of a member is given by the limiting flexural bending moment: Mn = S Fcr where S is the elastic section modulus for the plane of bending under consideration and Fcr is the lowest value from (where appropriate): i) Doubly symmetric members (lateral torsional buckling) Fcr = 6.895 C X X X b 1 1 2 2 2 1 2 2 1 λ 2λ + ⎧⎨⎩ ⎫⎬⎭ [Table A-F1.1(b)] {Imperial: Fcr = C X X X b 1 1 2 2 2 1 2 2 1 λ 2λ + ⎧⎨⎩ ⎫⎬⎭ } where; Cb = 1.75 + 1.05(M1/M2) + 0.3(M1/M2)2 ≤ 2.3 where M1 is the smaller and M2 the larger end moment in the unbraced member; M1/M2 is positive when the moments cause reverse curvature. X1 = (π/S) (EGJA / 2) X2 = (4Cw/Iy)(Sx/GJ)2 E = Modulus of elasticity (200,000 MN/m2 {29,000 ksi}). G = Shear modulus of elasticity (77,200 MN/m2 {11,200 ksi}). J = Torsion constant for section. A = Cross-sectional area (excluding rack teeth). Iy = Second moment of area of section about minor axis. Sx = Elastic section modulus for major axis bending. Cw = Warping constant. λ = Lb/ry ry = Radius of gyration about the minor axis ii) Singly symmetric members (lateral torsional buckling) [Table A-F1.1(c)] Fcr = 393,000Cb b SL {B1 + (1 ) 2 1 + B + B 2 } (I J) y ≤ Fy {Imp'l: Fcr = 57,000C SL b b {B1 + (1 ) 2 1 + B + B 2 } (I J) y ≤ Fy} where; B1 = 2.25 2 1 1 2 I I h L I J c y b y ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ − ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ⎧⎨⎩ ⎫⎬⎭ ⎧⎨⎩ ⎫⎬⎭ B2 = 25 1 2 − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ⎧⎨⎩ ⎫⎬⎭ ⎧⎨⎩ ⎫⎬⎭ I I h L I J c y b c h = web depth. Ic = second moment of area of compression flange about the section minor axis Cb = as for doubly symmetric sections. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 125 Rev 3, August 2008 iii) Doubly and singly symmetric members (flange local buckling) [Table A-F1.1(g)] Fcr = 77,220/λ2 {Imperial: Fcr = 11,200/λ2} where; λ = bi/ti for flange(s) iv) For tubular members (Local buckling) [Table A-F1.1] Fcr = 33,610/(R/t) {Imperial: Fcr = 4,875/(R/t)} where; R = radius of tubular t = wall thickness of tubular 8.1.4.7 Determination of η for non-tubular sections The general interaction equation requires that applied bending moments are resolved into components in two perpendicular axes (X,Y). For elaborate sections such as chords, these axes may be selected on the basis of section geometry and not on load incidence. Therefore neither of these axes need be coincident with the angle of load. The use of the exponent η is necessary to ensure that the effective nominal bending strength of the section is not significantly influenced by this choice of axes. To determine a suitable value of η the following process is applied: 1. For angles q = 0°, 30°, 45°, 60°, 90°, to the X-axis, obtain the allowable bending strengths Mnq. 2. Assume loads incident at angle q=30°, the limiting bending moment in the absence of axial load is Muq = Mnq. When the section is non-compact Mnq is a function of Mr and a suitable analysis in line with that of Section 8.1.4.6 b), should be applied in determining Mr for non-principal axes. 3. Resolve this limiting moment into limiting components M'uex and M'uey about the X and Y axes: M'uex = Muq cos q M'uey = Muq sin q 4. The interaction ratio for the (X,Y) axis pair is required to give the same result as if the X-axis were lined up with the q-axis: i.e. M M M M M M uex nx uey ny uq nq ⎛ ' ' ⎝ ⎜ ⎞ ⎠ ⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ = η η η 1 Since Mnx and Mny are by definition Mnq for q = 0° and 90° respectively and so are known, the only unknown in the above identity is η. This can be determined from the graph in Figure 8.4 or by numerical means if preferred. Figure 8.4 is based on the ratio Muq/Mnq being equal to unity, and will produce conservative results when axial loads are present. 5. Step 4 yields a value of η suitable for loads from 30° to the X-axis. Steps 2 to 4 are repeated for q = 45° and 60° to obtain a range of values of η. 6. The value of η for use in subsequent assessment shall be the least of the above determined values, but not less than 1.0. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 126 Rev 3, August 2008 This method includes some approximation. Since bending will not be along or perpendicular to a plane of symmetry, deflection will not necessarily be at the same angle as the applied moment. This effect is second order. Note: An alternative, more detailed approach, involving modified interaction equations is presented below for a number of typical chord configurations. 8.1.4.8 Plastic Interaction Curve Approach Alternatively, interaction equations and curves for generic families of chords are presented in Figures C8.1.8 - C8.1.11 in the Commentary. These are taken from Dyer [19] and based on the interaction approach proposed by e.g. Duan & Chen [20]. It should be noted that the curves and equations are based on axial load applied at the 'center of squash' which is defined as the location at which the axial load produces no moment on the yielded section. For chords without two axes of symmetry (triangular and tubular with offset rack) this is offset from the elastic centroid when the section is comprised of materials of differing yield strengths. Before a section is checked it is necessary to correct as appropriate moments by the axial load times the offset distance between the elastic centroid (used in the structural analysis) and the 'center of squash'. This offset, together with other geometric data for the members of each family of chord is presented in Tables C8.1.1 to C8.1.4 in the Commentary. The effective applied moment may then be calculated from: Muex = Bx(Mux + Pu.ey) Muey = By(Muy + Pu.ex) The interaction equations are based on ultimate capacity. It is therefore necessary to introduce the required resistance factors. This is achieved by defining: Py = F1.φa.Pn Mpx = F2.φb.Mnx Mpy = F2.φb.Mny where; F1 = 1.0, unless alternative values are justified by analysis. F2 = 1.0, unless alternative values are justified by analysis. The ratio of Pu/Py, Muex/Mpx and Muey/Mpy shall be determined for the condition under consideration. The user should then enter the plastic interaction curves with the Muex/Mpx and Muey/Mpy ratios. The allowable value for Pu/Py may then be determined. A measure of the interaction ratio can then be obtained as the ratio between the actual and allowable values of Pu/Py. The user should note that the equations for sections with only one axis of symmetry depend on the sign of the moment about the Y-Y axis (given in the Figures). The sign convention should be observed with care. The equations are based on lower bound data from each family of chord shape and will therefore tend to be conservative. More accurate results will be obtained from the individual consideration of the chord in question. [NOTE: At present Figures C8.1.8 - C8.1.11 in the Commentary cover only fully plastic section strength considerations, and their use for a beam-column member is based on the assumption that the member being evaluated is sufficiently short/compact that elasto-plastic stability (buckling at large strains) is not a consideration. Violating this assumption may lead to errors on the unsafe side. Updated information covering elasto-plastic stability may be generated in the future, and should preferentially be used for member evaluations.] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 127 Rev 3, August 2008 8.1.5 Assessment of other member geometries It is recommended that other member geometries are assessed using the relevant provisions of AISC LRFD [14] or, for stiffened or high R/t ratio shell members, the DNV Rules for fixed offshore installations in conjunction with the DNV Classification note on Buckling Strength Analysis of Mobile Offshore Units [15]. For these geometries, the nominal strength/resistance factors shall be the same as given in the relevant codes, but the load cases and factored loads should be determined in accordance with Section 8.1.3 rather than using the factors in the reference. 8.1.6 Assessment of member joints It is recommended that the assessment of joints of members which form a truss structure be carried out in accordance with AISC LRFD [14] or API LRFD [16] as appropriate for the joint under consideration. The factored loads should be determined in accordance with Section 8.1.3, rather than using the factors in the references. Figure 8.2: Typical members and components COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 128 Rev 3, August 2008 Figure 8.3: Effective Length Factors (from AISC-LRFD [14]) Figure 8.4: Chart for Determination of η COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 129 Rev 3, August 2008 8.2 Overturning Stability 8.2.1 For independent leg jack-ups the assumed overturning axis shall be the most critical axis passing through any two spudcan reaction points as defined in Section 5.2. 8.2.2 The overturning moment shall be calculated from the components of environmental loading, resolved normal to the overturning axis, times the vertical distance from the point of action of the component to the overturning axis. The overturning stability should meet the overturning requirements of 8.2.3, based on the overturning moment MO resulting from the application to the jack-up of the factored load Q described in 8.1.3. 8.2.3 The unit shall be shown to satisfy the following overturning requirements: MO ≤ φ1.MD + φ2.ML + φ3.MS where; MD = The stabilizing moments due to weight of structure and non-varying loads (at the displaced position resulting from the factored loads - see note) including: - Weight in air including appropriate solid ballast. - Equipment. - Buoyancy. - Permanent enclosed liquid. ML = The stabilizing moment due to the most onerous combination of minimum variable load and center of gravity applicable to extreme conditions as specified in Section 3.2 (at displaced position - see note). MS = The stabilizing moments due to seabed foundation fixity (these shall not be taken into account unless specific calculations for the location and the spudcan concerned show that a significant contribution from seabed fixity may be expected). φ1 = R.F. for dead load moments (MD) = 0.95 φ2 = R.F. for live load moments (ML) = 0.95 φ3 = R.F. for seabed moments (MS) = 0.95 Note: It may be convenient to consider the reduction in dead and live load stabilizing moment caused by the displacement resulting from the factored loads as an increase in the overturning moment, rather than as a reduction in the stabilizing moment. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 130 Rev 3, August 2008 8.3 Foundation assessment The foundation assessment shall be carried out in a step-wise manner until the requirements of the current stage are satisfied when it is not necessary to proceed further. The philosophy is described in Section 6.3 and shown in Figure 6.9. 8.3.1 Step 1 - Preload and Sliding checks Step 1a - Preload check 8.3.1.1 A preload check shall be used to verify the adequacy of the leeward leg foundation. The acceptance criteria for the windward leg are discussed in Section 8.3.1.5. 8.3.1.2 The preloading capability should be checked for the vertical leg reaction Qv caused by the following factored loads resulting from the application to the jack-up of the factored load Q described in 8.1.3. 8.3.1.3 The preload capacity shall be shown to be sufficient to satisfy the following requirements: Qv ≤ φp.VLo where; VLo = Vertical leg reaction during preloading φp = R.F. for foundation capacity during preload = 0.9 (see Commentary) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 131 Rev 3, August 2008 8.3.1.4 In dense sands (i.e. with maximum bearing area not mobilized) and in clayey soils the preload check may be applied if the leeward leg horizontal reaction QH < 0.1VLo (with QH determined in accordance with Section 8.3.1.5). For a spudcan fully embedded in sand the preload check may be applied if the leeward leg horizontal reaction QH < 0.03VLo. In all other cases a pinned condition bearing capacity check of the foundation shall be carried out in accordance with Section 8.3.2 (see Commentary). 8.3.1.5 Step 1b - Sliding Resistance - Windward Leg(s) a) The sliding capacity of the windward leg(s) should be checked for the horizontal leg reaction QH in association with the vertical leg reaction Qy, both resulting from the application to the jack-up of the factored load Q described in 8.1.3. b) The foundation shall be shown to satisfy the following capacity requirements: QH ≤ φHfc.FH where; FH = foundation capacity to withstand horizontal loads when load QV is acting φHfc = R.F. for horizontal foundation capacity (see Commentary). = 0.80 (effective stress - sand/drained). = 0.64 (total stress - clay/undrained). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 132 Rev 3, August 2008 8.3.2 Step 2a - Capacity check - pinned foundation 8.3.2.1 The bearing capacity of the leeward leg should be checked for the leg reaction vector QVH of vertical and horizontal leg reaction resulting from the application to the jack-up of the factored load Q described in 8.1.3. 8.3.2.2 The leeward leg foundation shall be shown to satisfy the following capacity requirements: QVH ≤ φVH.FVH where; FVH = foundation capacity to withstand combined vertical and horizontal loads taken as a vector from the still water load vector in the same direction as QVH. φVH = R.F. for foundation capacity (see Commentary). = 0.90 - Maximum bearing area not mobilized. = 0.85 - Penetration sufficient to mobilize maximum bearing area. 8.3.2.3 The windward leg foundations should be checked according to the requirements of Section 8.3.1.5. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 133 Rev 3, August 2008 8.3.3 Step 2b - Capacity check - with foundation fixity 8.3.3.1 The foundation capacity of the leeward and windward legs should be checked for the leg reaction vector, including vertical and horizontal leg reaction and the associated can moment, QVHM, resulting from the application to the jack-up of the factored load Q described in 8.1.3. 8.3.3.2 The leg reaction vector QVHM shall be checked to satisfy the yield surface as defined in 6.3.4. 8.3.3.3 The windward and leeward leg foundations shall also be shown to satisfy the bearing capacity and sliding capacity requirements of 8.3.2. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 134 Rev 3, August 2008 8.3.4 Step 3 - Displacement check If the factored loads on any footing exceed the factored capacity discussed above a further assessment may be performed in order to show that any additional settlements and/or the associated additional structural loads are within acceptable limits. See Section 6.3.5. 8.3.5 Punch-through The selection of factors of safety against punch-through should be made using sound engineering judgment, accounting for the accuracy of the available soil data and the magnitude of any possible sudden penetration (see Commentary). When the possibility of punch-through exists during the installation and preloading phases it may be applicable to consider the magnitude of possible sudden penetration in comparison with the structural capability of the unit to resist punch-through. If the possibility of punch-through remains once the unit has been installed on location and elevated to the operational airgap the evaluation should account for long term effects (e.g. cyclic degradation). 8.4 Horizontal Deflections When working close to or over a platform the assessor shall, if required by the platform owner, provide the extreme deflections of the jack-up to the platform owner (see Section 5.5.1 of the GUIDELINE). 8.5 Loads in the Holding System 8.5.1 The holding system (elevation and/or fixation system) is deemed to be the system which forms the load path connecting the hull to the legs. 8.5.2 The loads in the holding system shall not exceed those specified by the manufacturers, unless the basis of the limitations and the equivalent reference stress levels are stated, when the loads in the holding system resulting from the application to the jack-up of the factored load Q described in 8.1.3 may be compared with the ultimate capacity multiplied by a R.F. (φ) of 0.85. 8.5.3 he stresses in the structural members connecting the holding system to the hull shall be in accordance with the requirements of Section 8.1. 8.6 Hull 8.6.1 It is assumed that the jack-up hull is designed and built to the structural/scantling requirements of a recognized Classification Society and carries a valid Class Certificate. 8.6.2 For jack-ups where 8.6.1 does not apply it shall be shown that the hull has adequate strength to withstand appropriate combinations of dead load, variable load, environmental load, deflections, preload conditions and dynamics effects. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 135 Rev 3, August 2008 8.7 Structure Condition Assessment The objective of the site specific assessment is to ensure an appropriate level of structural reliability of the jack-up in the elevated condition. To achieve this, account must be taken of any deterioration in the jack-up structure (see Section 1.3.4 of the GUIDELINE). The condition of the structure is the responsibility of the owner and is deemed to be satisfactory if the jack-up has valid class certification as described in Section 2.4.2. Normally the owner can thus provide the assessor with all the information required to satisfy the structure condition requirement. In special cases (usually at the option of the operator), an on site structural inspection may be required to assess the condition of the jack-up. Guidance for such an on site structural inspection is given in the Commentary. In the event that the results of this inspection reveal deterioration of the structure, due account of such deterioration shall be taken into account in the assessment. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 136 Rev 3, August 2008 8 GLOSSARY OF TERMS - ACCEPTANCE CRITERIA ar = Ratio of total web area to area of compression flange. A = Cross sectional area of a member (excluding rack teeth). Ae = Section effective area (excluding rack teeth). Ai = Area of a component in a member. bei = Effective width of a component. bi = Width of a rectangular component. B,B1,B2 = Factors used in determining Mu for combined bending and compressive axial load. Bx,By = Moment amplification factors. Cb = Bending coefficient dependent on moment gradient. Cm = Coefficient applied to bending term in interaction formula for prismatic members dependent upon column curvature caused by applied moments. Cw = Warping constant. D = Dead load vector due to the self-weight of the structure and non-varying loads. Dn = The load vector due to the inertial loadset which represents the contribution of dynamics over and above the quasi-static response (including associated large displacement effects). e , ex, ey = Eccentricity between elastic and plastic neutral axes. E = Load due the to assessment return period wind, wave and current conditions (including associated large displacement effects). E = Modulus of elasticity (200,000 MN/m2 {29,000 ksi}). fi = Component compressive stress. Fcr = Critical stress. FH = Foundation capacity to withstand horizontal loads when QV is acting. Fmin = The smaller value of Fyi and (5/6)Fui of all the components (in a member). Fr = Residual stress due to welding (114 MN/m2). FVH = Foundation capacity to withstand combined vertical and horizontal loads. FVHM = Foundation capacity to withstand combined vertical, horizontal and moment loads. Fy = Minimum specified yield stress or specified yield strength. Fyh = Minimum yield stress or specified yield strength of component with highest b/t ratio. Fyeff = Effective material yield stress for consideration of axial buckling. Fyi = Minimum specified component yield stress or specified yield strength. Fywj = Minimum specified web yield stress or specified yield strength. Fyfj = Minimum specified flange yield stress or specified yield strength. Fui = Component material ultimate strength. G = Shear modulus of elasticity. h = Subscript referring to the component which produces the smallest value of Mn. h = Web depth. Ic = Second moment of area of compression flange. I = Second moment of area of section. Ix = Second moment of area of section about major axis. Iy = Second moment of area of section about minor axis. J = Torsional constant for the section. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 137 Rev 3, August 2008 8 GLOSSARY OF TERMS - ACCEPTANCE CRITERIA (continued) K = Effective length factor. ι = Unbraced length of member; face to face for braces, braced point to braced point for chords. L = The load vector due to the maximum or minimum variable load positioned at the most onerous center of gravity location applicable to extreme conditions. Lb = Laterally unbraced length; length between points which are either braced against lateral displacement of compression flange or braced against twist of the cross section. m = Ratio of web component yield stress to flange component yield stress which gives smallest value of Re. MD = Stabilizing moment due to self weight. ML = Stabilizing moment due to most onerous combination of variable load and center of gravity. MS = Stabilizing moment due to seabed foundation fixity. Mn, Mnx, Mny = Nominal bending strength. Mnq = Allowable bending strength about axis q. MO = Factored overturning moment. Mp = Section plastic moment. Mpx = Plastic moment capacity about member x-axis. Mpy = Plastic moment capacity about member y-axis. Mr = Limiting buckling moment of section. Mu = Applied moment determined in an analysis which includes global P-Δ effects and accounts for local loading. Mue, Muex, Muey = Effective applied bending moment. M'uex, M'uey = Limiting components of applied bending moment. Muq = Assumed limiting bending moment about axis q in absence of axial load. M1 = Smaller end moment of a member. M2 = Larger end moment of a member. PE = Euler buckling strength. Pu = Applied axial load. Pn = Nominal axial strength. Pni = Component nominal axial strength. Py = Axial yield strength. q = Angle of load heading with respect to defined X axis. Q = Factored load vector. Q = Full reduction factor for slender compression components. Qa = Reduction factor for slender stiffened compression components. QH = Factored horizontal leg reaction. Qs = Reduction factor for slender unstiffened compression components. QV = Factored vertical leg reaction. QVH = Factored leg reaction vector of vertical and horizontal loads. QVHM = Factored leg reaction vector of vertical, horizontal and moment loads. r = Radius of gyration. rx = Radius of gyration about the major axis. ry = Radius of gyration about the minor axis. R = Outside radius of the tube or tubular component. Re = Hybrid girder reduction factor. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 138 Rev 3, August 2008 8 GLOSSARY OF TERMS - ACCEPTANCE CRITERIA (continued) S = Elastic section modulus. Sx = Elastic section modulus for major axis bending. Sy = Elastic section modulus for minor axis bending. t = Thickness of tubular member or tubular section. ti = Thickness of a rectangular or tubular component.. VLo = Vertical leg reaction during preloading. X1,X2 = Beam buckling factors. Zi = Component plastic modulus. γ = Load factor. γ1 = Load factor for dead load vector. γ2 = Load factor for variable load vector. γ3 = Load factor for environmental load vector. γ4 = Load factor for inertial load vector due to dynamic response. λ,λc = Column slenderness parameter. λp = Limiting slenderness parameter for compact component. λr = Limiting slenderness parameter for noncompact component. η = Exponent for biaxial bending. φ = Resistance factor. φa = Resistance factor for axial load. φb = Resistance factor for bending. φc = Resistance factor for axial load (compression). φHfc = Resistance factor for foundation to withstand horizontal loads when QV is acting. φp = Resistance factor for foundation during preload. φt = Resistance factor for axial load (tension). φVH = Resistance factor for foundation to withstand combined vertical and horizontal loads. φVHM = Resistance factor for foundation to withstand combined vertical, horizontal and moment loads. φ1 = Resistance factor for dead load moments (MD). φ2 = Resistance factor for live load moments (ML). φ3 = Resistance factor for seabed moments (MS). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 139 Rev 3, August 2008 REFERENCES 1 Carter D.J.T. (1982), 'Estimation of Wave Spectra from Wave Height and Period', I.O.S. Report No. 135. 2 Compiled by P. Walker (1990), The UKOOA Surveying and Positioning Committee 'Technical Notes for the conduct of Mobile Drilling Rig Site Surveys (Geophysical and Hydrographic)'. 3 Health and Safety Executive, Petroleum Engineering Division (1990), 'Offshore Installations; guidance on design and construction' (and subsequent amendments). 4 Wheeler J.D. (1969) 'Method for Calculating Forces Produced by Irregular Waves', Proceedings 1st Offshore Technology Conference, Houston. (OTC 1006). 5 Taylor P.H. (1991), 'Current Blockage - Reduced Forces on Offshore Space-Frame Structures' Proceedings 23rd Offshore Technology Conference, Houston. (OTC 6519). 6 Det Norske Veritas, Classification Note 31.5, 'Strength Analysis of Main Structures of Self-Elevating Units', February 1992. 7 Brekke J.N., Murff J.D., Campbell R.B., and Lamb W.C., (1989) 'Calibration of Jackup Leg Foundation Model Using Full-Scale Structural Measurements', Proceedings 21st Offshore Technology Conference, Houston. (OTC 6127). 8 Meyerhoff G.G. and Chaplin T.K., 'The Compression and Bearing Capacity of Cohesive Layers', Br. J. Appl. Phys, No 4, 1953. 9 Brown J.D., and Meyerhoff G.G., 'Experimental study of Bearing Capacity in Layered Soils', Proc. 7th ICSMFE, Vol 2, 1969. 10 Winterkorn H.F. and Fang H.Y. (1975) 'Foundation Engineering Handbook', Van Nostrand Reinbhold Company. 11.1 Noble Denton & Associates Limited (1987), 'Foundation fixity of jack-up units, Joint Industry Study', Volumes I and II. 11.2 Noble Denton & Associates Limited (1988), 'Foundation fixity of jack-up units, Joint Industry Study, extra work'. 12 Sarpkaya T. and Isaacson M. (1981), 'Mechanics of Wave Forces on Offshore Structures', Van Nostrand Reinhold Company. 13 Det Norske Veritas, Classification Note 30.2, 'Fatigue Strength Analysis for Mobile Offshore Units', August 1984. 14 American Institute of Steel Construction, 'Specification for Structural Steel Buildings - Load and Resistance Factor Design', September 1986. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 140 Rev 3, August 2008 REFERENCES (Continued) 15 Det Norske Veritas, 'Rules for Classification of Fixed Offshore Installations', July 1989, Part 3, Chapter 1, Section 6B and associated Class Note 30.1, 'Buckling strength analysis of Mobile Offshore Units', October 1987. 16 American Petroleum Institute, 'Draft Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Load and Resistance Factor Design' (RP 2A-LRFD), First Edition, December 1989. 17 Matlock H. (1970), "Correlations for Design of Laterally Loaded Piles in Soft Clay", Proceedings Offshore Technology Conference (OTC 1204). 18 Andersen K.H. (1992), "Cyclic effects on Bearing Capacity and Stiffness for a Jack-up Platform on Clay", NGI Oslo report 913012-1, Rev 1. 19 Dyer A.P., "Plastic Strength Interaction Equations for Jack-Up Chords", MSc Thesis, Dept of Mechanical Engineering, Univ. of Sheffield, Nov. 1992. 20 Duan L., Chen W.-F., "A Yield Surface Equation for Doubly Symmetrical Sections", Engineering Structures, Vol 12, pp. 114-119, April 1990. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 141 Rev 3, August 2008 INDEX Subject Page(s) ACCEPTANCE CRITERIA 10, 110 - 135 dynamic extreme response 102 foundation assessment 130 holding system loads 134 horizontal deflections 134 hull 134 overturning stability 129 punch-through 134 structural strength check 110 structure condition assessment 135 ADDED MASS 35, 91, 95, 100 AIRGAP 16, 20 AIRY WAVE THEORY 15, 31 AISC-LRFD CODE 110, 112, 113 ASSOCIATED WAVE PERIOD 15 AXIAL AREA chord 49 leg 54 AXIAL LOAD at leg/hull connection 50 due to P-Δ 44 AXIAL STRENGTH compact and noncompact sections 117 slender sections 118 structural member in compression 116 structural member in tension 116 BASE SHEAR TRANSFER FUNCTION 90,94,98,99,102,103 BATHYMETRIC SURVEY 21, 22 BEARING CAPACITY 61-82 bearing capacity check, foundation stability 72, 132 penetration in carbonate sands 65 penetration in clays 64 penetration in layered soils 66-69 penetration in silica sands 65 penetration in silts 65 settlements resulting from exceedence of capacity envelope 73 soil back-flow 63 BENDING MOMENT bending moment diagrams for leg 55-58 bending moment due to foundation 42 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 142 Rev 3, August 2008 INDEX (Continued) Subject Page(s) BENDING STRENGTH –121-125 compact sections 122 noncompact sections 122-123 slender sections 123-125 BIAXIAL BENDING EXPONENT –125-128 BOREHOLE INVESTIGATION 24 BREAKING WAVES 19, 31 CENTER OF GRAVITY 13, 14, 114, 129-134 COMPACT SECTIONS definition 114 nominal axial strength 116 nominal bending strength 121 CONE PENTROMETER TESTING 24 CREST ELEVATION 15, 20 CURRENT 18-19, 33 drag forces 29-30, 33 environmental excitation 93 other considerations 39 load application 53, 89 profile 19, 33 stretching 19 structure interference 33, 34 surface current 18 surge 18, 19 tide 18, 19 velocity 18, 19, 33 DETAILED LEG MODELING hydrodynamic 33-39 structural 46-52 DETERMINISTIC ANALYSIS 31,42 dynamic wave analysis 93 extreme response determination 89 hydrodynamic modeling 34 wave height for 15 wave theories 31 DIRECTIONALITY 14 directionality function for spreading 17 effects on dynamic response 102 DISPLACEMENT CHECK, FOUNDATION ASSESSMENT 70, 81, 134 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 143 Rev 3, August 2008 INDEX (Continued) Subject Page(s) DRAG COEFFICIENTS 33-39 equivalent drag coefficient 34-35 gusset drag coefficient 37 split tube chord drag coefficient 38 triangular chord drag coefficient 39 tubular drag coefficient 36 DRAG FORCE 30, 33 DYNAMIC AMPLIFICATION 89,91,93,98-100 dynamic amplification factor 98, 99 DYNAMIC ANALYSIS 89-107 application of dynamic analysis methods 104 closed-form frequency domain analysis 98 damping 90, 98, 101 dynamic amplification 89,91,93,94,98 dynamic amplification factor 98,99 environmental excitation 93 equivalent mass-spring-damper system 95,98 extreme response 89,92,104,105 fixation system 46, 48, 49-51,55-58, 97 frequency domain method 94, 100,101,104,105 inertial loadset 52, 53, 89-91, 98- 101 JONSWAP spectrum 16-17, 93 maximum response 18 most probable maximum 100,101,104,105 natural period 18,90,93,94-99 nonlinear elements 91 Pierson-Moskowitz spectrum 16, 93 random analysis 90,93,94,100-103 regular wave (deterministic) analysis 93 single degree of freedom analogy 98,99 structural system 91 damping 91,98,101 masses 91,95 springs 95 stiffness 91,94 time domain methods 94,101,104,105 EFFECTIVE LENGTH 117 effective length factor 117, 128 ENVIRONMENTAL DATA 14-21 (see also WIND, WAVE and CURRENT) directionality 14, 17 return period 10, 14 return period for airgap 15, 20 ENVIRONMENTAL EXCITATION 93 EQUIVALENT LEG MODELING hydrodynamic 33 structural 47, 49,54 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 144 Rev 3, August 2008 INDEX (Continued) Subject Page(s) EXTREME (MPME) RESPONSE 89,92,104 EXTREME STILL WATER LEVEL 20, 42 FACTORED LOADS 110 for foundation stiffness determination 74 foundation checks 130-134 overturning check 129 structural strength check 114 FACTORED RESISTANCE 110 foundation checks 130 - 134 overturning check 129 structural strength check 115 FATIGUE 88, 106, 107 analysis 42, 107 environmental data for 17-18, 19 life requirements 106 sensitive areas 106 FIXATION SYSTEM 46 modeling 48, 49-51 rotational and vertical stiffness 97 shear force and bending moment diagrams 55-58 FIXITY 42-43 degree of fixity 43, 91, 94 foundation capacity with 133 horizontal and vertical stiffness 75, 96 rotational foundation fixity (stiffness) 42-43, 73-75, 76, 95 FOOTPRINTS 22, 79 FOUNDATION ASSESSMENT 130-134 capacity check 132 foundation fixity 133 pinned foundation 132 displacement check 134 horizontal leg reaction 133 preload check 130 sliding resistance 131 vertical leg reaction 125 FOUNDATION ANALYSIS 61-85 bearing capacity 61-81, 130-134 displacement check 70, 81,134 moment fixity 73-81 footprints 22,83 leaning instability 83 other considerations 70 partial spudcan embedment 70 preloading penetration 61-69 preloading check 70-72, 130-131 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 145 Rev 3, August 2008 INDEX (Continued) Subject Page(s) FOUNDATION ANALYSIS (Continued) scour 22, 84 seafloor instability 85 shallow gas 22, 85 sliding check 70,72-73, 131 spudcan-pile interaction 85 FREQUENCY DOMAIN ANALYSIS 92, 94, 101-103, 104,105 closed-form frequency domain analysis 100 GEOTECHNICAL ANALYSIS 61-85 leg penetration 61-69 analysis method 61-63 carbonate sands 65 clay 64 layered soils 66-69 silica sands 65 silts 65 spudcan geometries 61, 62 spudcan foundation model 62 GEOTECHNICAL SURVEYS 21-24 bathymetric survey 21, 22 borehole investigation 24 cone penetrometer testing 24 geotechnical investigation 24 seabed surface survey 21-23 shallow seismic survey 22, 23 soil sampling 22 use of geotechnical data 61 GUIDES 46, 49-51, 59 GUSSETS 37, 48 HEIGHT COEFFICIENT FOR WIND LOADING 28 HOLDING SYSTEM LOADS 46, 49, 134 HORIZONTAL DEFLECTIONS 134 HORIZONTAL LEG REACTION, FOUNDATION ASSESSMENT 131-133 HULL acceptance criteria 134 detailed hull model 49 equivalent hull model 49 functional loads 13 loading 52 HULL/LEG CONNECTION MODELING 46, 47, 49-51 equivalent system 49, 51 fixation system 50, 51 guides 49-51, 59 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 146 Rev 3, August 2008 INDEX (Continued) Subject Page(s) HULL/LEG CONNECTION MODELING (Continued) jackcase 51 jacking system 50, 51 modeling considerations 49-51 shock pads 51 HULL MODELING 49 detailed hull model 49 equivalent hull model 49 HYDRODYNAMIC COEFFICIENTS 36-39 gussets 37 marine growth 21, 30, 36 non-tubulars 38 other shapes 39 rough tubulars 36 smooth tubulars 36 split tube chord 38 triangular chord 39 tubulars 36 HYDRODYNAMIC LOADS 29-31, 53 deterministic/regular wave analysis 15, 31 drag force 30 fluid-structure interaction 30, 98 inertia force 30-31 Morison's equation 29, 30, 31, 33, 36 slender members 29 stochastic/random wave height/spectra 15, 16-17, 31 wave kinematic extrapolation 31 INERTIA inertia coefficients 35, 36, 37, 38-39 inertia force (wave) 30 inertial loadset 52, 53, 89, 90,98-101 INTERACTION EQUATIONS FOR MEMBER CHECKS 115, 119, 125 JACKING SYSTEM 46, 49-51,55-58 LARGE DISPLACEMENT ANALYSIS (see NON-LINEAR ANALYSIS) LEANING INSTABILITY 79 LEG/CAN CONNECTION 43 LEG/HULL CONNECTION (see HULL/LEG CONNECTION) LEG INCLINATION 43 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 147 Rev 3, August 2008 INDEX (Continued) Subject Page(s) LEG MODELING hydrodynamic added mass 35, 90, 94 buoyancy 13 detailed leg modeling 33-34 drag coefficients 33-39 equivalent leg modeling 33-35 inertia coefficients 35, 36-37, 38-39 member lengths 34 non-structural items 34 shielding 34 solidification 34 spudcan modeling 34 structural combination leg modeling 49 detailed leg modeling 46-52 equivalent leg modeling 47-49, 54 member lengths 48 single detailed leg model 48 spudcan modeling 52 LEG PENETRATION analysis method 61-63 carbonate sands 65 clay 64 layered soils 66 silica sands 65 silts 65 LEG RESERVE 21 LOAD AND RESISTANCE FACTOR DESIGN, STRUCTURAL STRENGTH 110-113, 127 LOADS application to structural model 52-53 combinations 89 current 53, 89 hull (functional) 13, 52 hydrodynamic 29-31, 53 inertial loadset 52, 53, 89, 90,98-101 P-Δ 43-45, 52, 53 wind 27-29, 53 LOCAL BUCKLING 116,121 MARINE GROWTH 21, 30, 36 MASS-SPRING-DAMPER SYSTEM 95,98-100 MAXIMUM HEIGHT, WAVE 14 MEAN WATER LEVEL 20 MINIMUM STILL WATER LEVEL 20 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 148 Rev 3, August 2008 INDEX (Continued) Subject Page(s) MOMENT bending moment capacity 121-125 bending moment due to foundation fixity 42 bending moment diagrams for leg 55-58 can moment 129, 133 effective applied moment members in compression 120 members in tension 119 hull sag moment 52-53 leg/hull connection moment 46, 49-51 lower guide moment due to leg inclination 43 overturning moment 90,100,129 P-Δ moment 43-45 second moment of area (legs) 54 MORISON'S EQUATION 29, 30, 31, 33, 36 MOST PROBABLE MAXIMUM 100,101,104,105 NATURAL PERIOD 90,93,94-99 NONLINEAR MODELING METHODS 44, 77 non-linear elements 87 NON-STRUCTURAL ITEMS, LEG MODELING 34 NON-TUBULARS, HYDRODYNAMIC COEFFICIENTS 38-39 OVERTURNING STABILITY 10, 129 axis 124 moment 44, 45, 89, 129 P-Δ 43-45 geometric stiffness modeling methods 44 linear-elastic displacement amplification 45 loads 52, 53 manual addition of P-Δ moments 45 non-linear modeling methods 44 PERIOD natural 18,90, 93, 94-99 return 14, 15, 20 wave associated 15 peak 16-17, 90,99 zero-upcrossing 17 PINIONS46-47,49-51,55-58,134 PLASTIC ANALYSIS 112 plastic moment 121,122 plastic stress distribution 114 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 149 Rev 3, August 2008 INDEX (Continued) Subject Page(s) PRELOAD 90,110 foundation assessment 130, 131 foundation stability 70-72 leg penetration during 61-69 PUNCH-THROUGH 134 QUASI-STATIC ANALYSIS 44, 87, 90,93,98-100 RACK TEETH fatigue 100 stiffness due to 49 marine growth on 36 RANDOM WAVE ANALYSIS (see STOCHASTIC ANALYSIS) REFERENCE LEVEL, WIND 14, 27, 28 REGULAR WAVE ANALYSIS (see DETERMINISTIC ANALYSIS) RESERVE LEG LENGTH 21 RESISTANCE FACTORS foundations 130 31 holding system 134 overturning 129 structural members 115 RESPONSE ANALYSIS 89-107 RETURN PERIOD 14, 15, 20 SCOUR 22, 80 SEABED REACTION POINT 42 SEABED SURFACE SURVEY 21 SEAFLOOR INSTABILITY 81 SHALLOW GAS 22, 81 SHALLOW SEISMIC SURVEY 22, 23 SHAPE COEFFICIENTS FOR WIND LOADING 29 SHEAR FORCE DIAGRAMS 55-58 SHIELDING 34 SHOCK PADS 50, 51 SHORTCRESTEDNESS (WAVE SPREADING) 17-18, 98, 102,103 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 150 Rev 3, August 2008 INDEX (Continued) Subject Page(s) SIGNIFICANT WAVE HEIGHT 14, 15, 17 SINGLE DEGREE OF FREEDOM ANALOGY 98,99 SLENDER SECTIONS hydrodynamic loads 29 structural considerations 114,118,123-125,127 SLIDING CHECK 70, 72-73, 130-131 SMOOTH VALUES, HYDRODYNAMIC COEFFICIENTS FOR TUBULARS 36 SOIL SAMPLING 23, 24 SOLIDIFICATION 34 SPECTRUM (WAVE) 16-18 JONSWAP 16-17, 92 Pierson-Moskowitz 16-17,92 SPLIT TUBE CHORD, HYDRODYNAMIC COEFFICIENTS 38 SPUDCAN modeling 34, 52 partial spudcan embedment 70 spudcan foundation model 62 spudcan geometries 61, 62 spudcan-pile interaction 86 STIFFNESS due to chord rack 49 for natural period estimation 95-98 geometric stiffness modeling methods 44 STOCHASTIC ANALYSIS dynamic analysis 93,94,100,101,104,105 hydrodynamic modeling 34 kinematic extrapolation 31 wave height for (scaled) 15 wave spectra 16-17 wave theory 31 STORM DIRECTIONS, RANGE OF 42 STRUCTURAL ANALYSIS 42-53 fatigue analysis 18, 42, 107 foundation fixity 42-43, 73-81 general conditions 42 leg inclination 43 load application 52-53 P-Δ effects 43-45 range of storm directions 42 response analysis 88-105 seabed reaction point 42 structural modeling 46-52 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 151 Rev 3, August 2008 INDEX (Continued) Subject Page(s) STRUCTURAL MEMBERS definitions 113 structural strength check 110-127 STRUCTURAL MODELING 46-52 combination 3-leg model 47 combination leg model 49 detailed hull model 49 detailed 3-leg model 47 detailed leg model 48 equivalent 3-stick-leg model 47 equivalent hull model 49 equivalent leg model 49 fixation systems 46, 51 general considerations 46-47 jacking systems 46, 51 jack-case and bracing 51 leg-hull connection modeling 49-51 model applicability 47 pinions 47, 51 rack tooth stiffness 49 shock pad 51 single detailed leg model 48 spudcan modeling 52 STRUCTURAL STRENGTH CHECK 110-127 AISC code 110-112, 127 axial strength structural member in compression 116-119 structural member in tension 116 bending strength 121-125 biaxial bending exponent 125, 128 compact sections 114 axial strength 116-119 bending strength 121-125 effective applied moment members in compression 120 members in tension 119 effective length factors 117, 128 factored loads 110-114 factored resistance 110, 115, 127 interaction equations 115 local buckling 116-119,121-125 limitations 112,113 load and resistance factor design 110,111,127 member joints 127 noncompact sections 122 axial strength 117 bending strength 122 other geometries 127 resistance factors 112,115, 127, 134 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 152 Rev 3, August 2008 INDEX (Continued) Subject Page(s) STRUCTURAL STRENGTH CHECK (Continued) slender sections 114 axial strength 118,119 bending strength 123-125 structural components - stiffened and unstiffened 113 structural members 113 structural strength check 110-127 torsional buckling (lateral) 121 yield stress 112,114,117 STRUCTURAL SYSTEM (FOR DYNAMICS) 91-93 damping 91, 102 masses 91,95 stiffness 94, –95-98 STRUCTURE CONDITION ASSESSMENT 10, 135 STRUCTURE INTERFERENCE, CURRENT 33, 34 TEMPERATURE - AIR AND WATER 20 THREE LEG MODEL combination 3-leg model 47 detailed 3-leg model 47 equivalent 3-stick-leg model 47 TIME DOMAIN ANALYSIS 94,101,104,105 TRIANGULAR CHORD, HYDRODYNAMIC COEFFICIENTS 39 TUBULARS, HYDRODYNAMIC COEFFICIENTS 36 VERTICAL LEG REACTION, FOUNDATION ASSESSMENT 130-133 WATER LEVEL 20 chart datum 20 extreme still water level 20 lowest astronomical tide 20 mean water level 20 minimum still water level 20 WAVES 14-18 Airy wave theory 15, 31 breaking waves 19, 31 crest elevation 15, 20 directionality function 17, 102 extreme wave height 14 freak waves 20 kinematic extrapolation 31 maximum height 14, 15 period associated 15 peak 16-17 return 14, 15, 20 zero-upcrossing 16-17 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Recommended Practice for Site Specific Assessment of Mobile Jack-Up Units Page 153 Rev 3, August 2008 INDEX (Continued) Subject Page(s) WAVES (Continued) shortcrestedness (spreading) 17, 97, 102, 103 significant height 14 significant height (scaled) 15, 17 spectrum JONSWAP 16-17, 93 Pierson-Moskowitz 16-17, 93 steepness 17 WEIGHT center of gravity 13, 14, 114, 129 - 133 minimum elevated weight 13 WIND 14, 27-29 force calculation 27-29 height coefficient 28 load application 53 profile 14, 28, 29 reference level 14, 27-28 shape coefficient 29 velocity 14, 27-28 YIELD STRESS 112,114,117 YIELD SURFACE, FOUNDATION FIXITY 74-75 ZERO-UPCROSSING WAVE PERIOD 16-17 COMPLIMENTARY COPY FOR 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COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER COMMENTARIES TO RECOMMENDED PRACTICE FOR SITE SPECIFIC ASSESSMENT OF MOBILE JACK-UP UNITS FIRST EDITION – MAY 1994 (REVISION 3 – AUGUST 2008) Rev Issue Date Details Rev 1 May 1997 Changes made to pages 11, 27, 30, 80, 86, 128, 155, 171, 176, and 191. Revised areas indicated by sidelines thus: Rev 2 Jan 2002 Changes made to pages 112,114, 131, 138, 147, 152, 153, 164, 176 Revised areas indicated by double sidelines thus: Rev 3 Aug 2008 Changes made to pages 9,115 – 119, 127,131, 164, 180 Revised areas indicated by triple sidelines thus: Note that page numbers listing above changes in Rev.1 and 2 may no longer be accurate due to insertion of material in Rev.3. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 2 Mobile Jack-Up Units Rev 3, August 2008 PREAMBLE These Commentaries to the Recommended Practice for Site Specific Assessment of Mobile Jack- Up Units (PRACTICE) have been written to provide background information, supporting documentation, and additional or alternative calculation methods as applicable. The reader should recognize that the information presented herein should only be taken in conjunction with the PRACTICE and that the cautions and limitations discussed in Section 1 of the PRACTICE apply. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 3 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS SECTION TITLE PAGE NO C3 COMMENTARIES TO ASSESSMENT INPUT CONDITIONS 12 C3.3 ENVIRONMENTAL CONDITIONS - GENERAL 12 C3.4 WIND 12 C3.5 WAVES 13 C3.5.1 Determining Wave Heights for Regular and Irregular Wave Analysis C3.5.1.1 Significant Wave Height for Stochastic Irregular Waves Analysis. C3.5.1.2 Wave Height for Regular Wave Analyses C3.5.3 Alternative formulation for wave spectrum. C3.5.4 Spreading C3.7 WATER LEVELS AND AIRGAP 20 Glossary of terms for Section C3 21 References for Section C3 22 C4 COMMENTARIES TO CALCULATION METHODS – HYDRODYNAMIC AND WIND FORCES 23 C4.1 INTRODUCTION 23 C4.2 WIND FORCE CALCULATIONS 23 C4.3 HYDRODYNAMIC FORCES 24 C4.3.1 General C4.3.2 Drag forces C4.3.3 Inertia forces C4.4 WAVE THEORIES 27 C4.4.1 General C4.4.2 Regular wave analysis C4.4.3 Irregular wave analysis C4.5 CURRENT 31 C4.5.1 General C4.5.2 Combination with wave particle velocities C4.5.3 Reduction of current by the actuator disc formula C4.5.4 Current stretching C4.6 LEG HYDRODYNAMIC MODEL 32 C4.6.1 General C4.6.2 Length of members C4.6.3 Spudcan C4.6.4 Shielding and Solidification C4.6.5 Equivalent drag coefficient C4.6.6 Equivalent Inertia coefficient COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 4 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS (Continued) SECTION TITLE PAGE NO C4.7 HYDRODYNAMIC COEFFICIENTS FOR LEG MEMBERS 34 C4.7.1 General C4.7.2 Hydrodynamic Coefficients for Tubulars C4.7.2.1 General C4.7.2.2 Literature survey and recommended values C4.7.2.3 Marine Growth dependence C4.7.2.4 Definition of relevant parameters C4.7.2.5 Dependence on roughness C4.7.2.6 Keulegan Carpenter number dependence C4.7.2.7 Reynold's number dependence C4.7.3 Marine Growth Thickness C4.7.4 Hydrodynamic Coefficients for Brackets C4.7.5 Hydrodynamic Coefficients for Chords C4.7.5.1 Split tube chords C4.7.5.2 Triangular chords C4.7.6 Other shapes C4.8 OTHER CONSIDERATIONS 58 Glossary of terms for Section C4 59 References for Section C4 61 Appendices to Section C4 C4.A Example of Equivalent Model Computations 66 C4.B Comparison cases to assess implications of PRACTICE 70 formulation C4.C Comparison of test results for chords 75 C5 COMMENTARIES TO CALCULATION METHODS – STRUCTURAL ENGINEERING 78 C5.1 INTRODUCTION 78 C5.2 GENERAL 78 C5.3 GLOBAL RESPONSE 79 C5.4 DISCUSSION OF THE LEG-HULL CONNECTION 80 C5.5 DETERMINATION OF PROPERTIES FOR EQUIVALENT MODELLING OF LEG AND LEG-HULL CONNECTION 82 C5.6 LOAD APPLICATION 84 C5.7 EVALUATION OF FORCES 84 Glossary of terms for Section C5 89 Appendices to Section C5 C5.A Derivation of alternative geometric stiffness formulation for P-Δ effects 90 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 5 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS (Continued) SECTION TITLE PAGE NO C6 COMMENTARIES TO CALCULATION METHODS – GEOTECHNICAL ENGINEERING 98 C6.1 INTRODUCTION 98 C6.2 PREDICTION OF FOOTING PENETRATION DURING PRELOADING 98 C6.2.1 Analysis method for leg penetration prediction C6.2.2 Penetration analysis for clays C6.2.3 Penetration analysis for silica sands C6.2.4 Penetration analysis for carbonate sands C6.2.5 Penetration in silts C6.2.6 Penetration analysis for layered soils C6.2.6.1 Squeezing of clay C6.2.6.3 Punch-through : Dense sand over soft clay C6.2.7 Summary C6.3 FOUNDATION STABILITY ASSESSMENT 111 C6.3.3 & C6.3.4 Bearing capacity for inclined loading C6.4 OTHER ASPECTS OF JACK-UP UNIT INSTABILITY 121 C6.4.1 Leaning instability C6.4.2 Footprint considerations C6.4.3 Scour C6.4.4 Seafloor instability C6.4.6 Spudcan-pile interaction Glossary of terms for Section C6 122 References for Section C6 124 C7 COMMENTARIES TO CALCULATION METHODS – DETERMINATION OF RESPONSES 128 C7.1 INTRODUCTION 128 C7.2 QUASI-STATIC EXTREME RESPONSE WITH INERTIAL LOADSET 128 C7.3 CONSIDERATIONS AFFECTING THE DYNAMIC RESPONSE 128 C7.4 SELECTION OF APPROPRIATE EXCITATION PERIOD 130 C7.5 METHODS FOR DIRECT DETERMINATION OF THE DYNAMIC RESPONSES 131 Appendices to Section C7 C7.A Derivation of jack-up stiffness equation 134 C7.B Details of appropriate dynamic analysis methods 145 C7.B.1 Analysis methods C7.B.1.1 Frequency domain methods C7.B.1.2 Time domain methods COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 6 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS (Continued) SECTION TITLE PAGE NO Appendices to Section C7 (continued) C7.B.2 Methods for determining the MPM 145 C7.B.2.1 Use of drag-inertia parameter (or equivalent) 147 determined from mean and standard deviation of a frequency or time-domain analysis. C7.B.2.2 Fit Weibull distribution to results of a 148 number of time-domain simulations to determine responses at required probability level and average the results. C7.B.2.3 Fit Gumbel distribution to histogram of peak 150 responses from a number of time-domain simulations to determine responses at required probability level. C7.B.2.4 Apply Winterstein's Hermite polynomial method 151 to the results of time domain simulation(s). C8 COMMENTARIES TO ACCEPTANCE CRITERIA 164 C8.0 BACKGROUND TO PARTIAL LOAD FACTORS 164 C8.0.1 General C8.0.2 Fundamental Question C8.0.3 Solution C8.0.3.1 Probabilistic Description of Input C8.0.3.2 Limit States C8.0.3.3 Response Model C8.0.3.4 Safety Index vs. Safety Factor C8.0.3.5 Reference or Target Safety Level C8.0.3.6 Derivation/Calibration of Safety Factors C8.1 STRUCTURAL STRENGTH CHECK 167 C8.1.1 Introduction C8.1.2 Definitions C8.1.3 Factored loads C8.1.4 Assessment of members - excluding stiffened and high D/t ratio tubulars C8.1.4.1 General interaction equations C8.1.4.2/3 Nominal Axial Strength C8.1.4.4/5 Effective Applied Moment C8.1.4.6 Nominal Bending Strength C8.1.5 Assessment of members - other geometries C8.3 FOUNDATION ASSESSMENT 186 C8.7 STRUCTURE CONDITION ASSESSMENT 188 C8.7.1 Introduction C8.7.2 Scope of condition assessment C8.7.3 Condition monitoring Glossary of terms for Section C8 190 References for Section C8 192 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 7 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS (Continued) LIST OF FIGURES C3.5.1 Comparison of wave crest elevation predicted skewness and 16 observed data at 70m in the North Sea. C4.3.1 Oscillating drag coefficient vs. motion amplitude to diameter 26 ratio x0/D for given reduced velocities. C4.4.1 Range of validity of different wave theories. 29 C4.4.2 Surface elevation, and velocity profiles for deterministic 30 regular waves. C4.4.3 Linearization w.r.t. wave heights. 30 C4.7.1 Comparison between measured and computed forces on a pile up 42 to free surface C4.7.2 Drag coefficient for rough cylinders at high Reynold's number 44 C4.7.3 Drag coefficient for post critical Reynolds numbers for rough 44 cylinders. C4.7.4 Effect of roughness on drag coefficient and vortex shedding 45 frequency for post-critical Reynolds numbers. C4.7.5 Recommended values for the drag coefficient as function of 45 relative roughness. C4.7.6 Drag coefficient dependence on KC number. 47 C4.7.7 Drag coefficient dependence on KC-number for clean cylinders 47 of the Ocean Test Structures. C4.7.8 Drag coefficient dependence on KC-number for barnacle covered 48 cylinders of the Ocean Test Structure. C4.7.9 Recommended drag coefficient dependence on KC for cylinders 48 in waves, at high Reynolds numbers. C4.7.10 Suggested Reynolds dependence in existing guidance. 49 C4.7.11 Reynolds dependence of drag coefficient in test results. 49 C4.7.12 Reynolds dependence of drag coefficient. 50 C4.7.13 Recommended values for Reynolds dependence for different 50 values of relative roughness, KC>40. C4.7.14 Definition of directions and dimensions for a split tube 53 chord. C4.7.15 Drag coefficient at 90° related to the rack width W. 53 C4.7.16 Alternative interpolation formulations fit to data. 54 C4.7.17 Comparison with some current practices for regular wave 54 analysis. W/D = 1.24 and the scaling regular/irregular =0.7, valid below MWL+2.0m. C4.7.18 Definition of dimensions and angles for a triangular chord. 56 C4.7.19 Drag coefficients for basic sections in uniform flow. 57 C4.7.20 Comparison between TEES test results and the PRACTICE. 57 C4.A.1 Model of a bay for test purposes 66 C4.A.2 Square bay with triangular chords 68 C4.C.1 Comparison of PRACTICE formulation with model tests, ratio 75 W/D = 1.08 C4.C.2 Comparison of PRACTICE formulation with model tests, ratio 75 W/D = 1.10 C4.C.3 Comparison of PRACICE formulation with model tests, ratio 76 W/D = 1.13 C4.C.4 Comparison of PRACTICE formulation with model tests, rack 76 W/D = 1.18 C4.C.5 Comparison of PRACTICE formulation with model tests, rack 77 W/D = 1.24 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 8 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS (Continued) LIST OF FIGURES (continued) C5.1 Responses/reactions from first order analyses 85 C5.2 P-Δ and leg inclination effects 85 C5.3 Contribution of second order effects to first order responses 86 C5.4 Representative leg-hull connection 86 C5.5 Leg-hull connection component combinations 87 C5.6 Guide clearances 87 C5.7 Jacking system backlash 87 C5.8 Types of leg guide arrangement 88 C5.9 Unopposed and opposed pinion arrangements 88 C5.A.1 Analysis model 94 C5.A.2 Load application 94 C6.1 Comparison of bearing capacity analytical procedures for 98 shallow foundations and jack-ups. C6.2 Stability factors for cylindrical excavations in clay. 98 C6.3 Conical footing bearing capacity - problem definition and 101 notation. C6.4 Depth of failure zone in sand 107 C6.5 Spudcan bearing capacity analysis - sand over clay - load 109 spread method. C6.6 Foundation bearing failure modes. 110 C6.7 Vertical/horizontal load envelopes for footings in clay. 112 C6.8 Foundation combined vertical/horizontal loading on sand 112 - comparison of design criteria and observed data. C6.9 Vertical/horizontal load envelopes for footings in sand. 112 C6.10 Normalised initial shear modulus as a function of Plasticity Index, Ip, for 11 different clays. Figure 10.2 from Anderson [55] 116 C6.11 Vertical load-displacement curves for leeward and windward 119 legs. C7.1 Periods for wave force cancellation and reinforcement as a 133 function of leg spacing. C7.A.1 Graphical solution of equation (24) 142 C7.B.1 Part 1 - Procedure for determining inertial loadset 153 C7.B.1 Part 2 - Procedure for determining (distributed) inertial 154 loadset C7.B.2 Time domain procedure for determining mean and standard 155 deviation. C7.B.3 Frequency domain procedure for determining mean and standard 156 deviation. C7.B.4 Procedure for estimating the extreme response. 157 C7.B.5 Procedure for determining the mpm-factor of the static 160 response. C7.B.6 Ratio CR of most probable maximum to standard deviation as a 162 Function of drag-inertia parameter K for N = 1000 peaks. C7.B.7 Comparison between the normalized spectra Sη(ω), Sφ(ω) and SPM(ω) 162 C8.0.1 Link between safety factor and safety index 166 C8.1.1 Stress-strain curve - ultimate strength much bigger than 171 yield strength. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 9 Mobile Jack-Up Units Rev 3, August 2008 C8.1.2 Stress-strain curve - yield strength close to ultimate strength. 171 C8.1.3 Stress-strain curves for two component member for which 171 addition of nominal strengths is permissible. C8.1.4 Stress-strain curves for two component member in which one 172 component fractures before the other is loaded to its nominal strength. C8.1.5 Stress-strain curves for components of example member. 172 C8.1.6 Example hybrid chord section. 174 C8.1.7 Fully plastic stress distribution. 174 C8.1.8 Interaction equations/curves for tubular chords with double 177 central racks. C8.1.9 Interaction equations/curves for split tubular chords with 180 double central racks. C8.1.10 Interaction equations/curves for tubular chords with offset 182 double racks. C8.1.11 Interaction equations/curves for triangular chords with 184 single racks. LIST OF TABLES C3.5.1 Regular Wave Analysis Normalized Results, CDeDe = 5.13 over the 14 full depth. C3.5.2 Scaling Factor γd on loads to comply with Airy Wheeler in 15 Irregular Seas. C4.7.1 Survey of Relevant Literature on CM- and CD-values for 37 Tubulars. C4.7.2 Recommended Roughness Values for Tubulars. 43 C4.7.3 Recommended Hydrodynamic Coefficients for Tubulars. 43 C4.7.4 Comparison of Drag Coefficients for Simple Sections and Chord 56 CDpr Evaluated From tests. C4.A.1 Computations of Equivalent model for heading 0° to be used in 66 Site Assessment for z < MWL +2m, chord W/D = 1.13. C4.A.2 Computations of Equivalent model for heading 0° to be 67 Compared with Model Test Results, Chord W/D = 1.13, Model Scale 1:4.264. C4.A.3 Computations of Equivalent model for heading 30° to be 67 Compared with Model Test Results, Chord W/D = 1.13, Model Scale 1:4.264. C4.A.4 Square Bay with Triangular Chords, Equivalent Model to be 68 used in Site Assessment z < MWL + 2m. C4.A.5 Square Bay with Triangular Chords, Equivalent Model to be 69 used in Comparison with Test Results, Model Scale 1:4.256. C4.B.1 Comparison including wave height scaling, water depth = 30m, 72 Hsrp = 10m. C4.B.2 Comparison including wave height scaling, water depth = 90m, 73 Hsrp = 14m. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 10 Mobile Jack-Up Units Rev 3, August 2008 CONTENTS (Continued) LIST OF TABLES (continued) C5.A.1 Verification of Simple Procedure for P-Δ Effect with Exact 93 Solution. Wave Loading Case. C5.A.2 Verification of Simple Procedure for P-Δ Effect with Exact 93 Solution. Wind Loading Case. C6.1 Nc' factors as a function of embedment, rate of increase of 103 shear strength with depth and roughness, cone angle 30°. C6.2 Nc' factors as a function of embedment, rate of increase of 103 shear strength with depth and roughness, cone angle 60°. C6.3 Nc' factors as a function of embedment, rate of increase of 104 shear strength with depth and roughness, cone angle 90°. C6.4 Nc' factors as a function of embedment, rate of increase of 104 shear strength with depth and roughness, cone angle 120°. C6.5 Nc' factors as a function of embedment, rate of increase of 104 shear strength with depth and roughness, cone angle 150°. C6.6 Nc' factors as a function of embedment, rate of increase of 104 shear strength with depth and roughness, cone angle 180°. C7.1 Recommended combinations of the structural system and 132 environmental excitation models for a dynamic analysis. C8.1.1 Data for tubular chords with double central racks. 179 C8.1.2 Data for split tubular chords with double central racks. 181 C8.1.3 Data for tubular chords with offset double racks. 183 C8.1.4 Data for triangular chords with single racks. 185 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 11 Mobile Jack-Up Units Rev 3, August 2008 C3 COMMENTARIES TO ASSESSMENT INPUT CONDITIONS C3.3 ENVIRONMENTAL CONDITIONS - GENERAL The PRACTICE does not permit the use of full joint probability (assessment return period) environmental data. Nevertheless some account of joint probabilities is permitted as noted below: - Seasonally adjusted data may be used if appropriate (Section 3.3.1). Note: When seasonal data are specified, the data should not be divided into periods of less than one month and the values so calculated should generally be factored such that the extreme for the most severe period equals the all-year value for the required assessment return period. - Where directional data are available, these may be considered (Section 3.3.1). Note: When directional data are specified, the data should normally not be divided into sectors of less than 30° and the directional values so calculated should generally be factored such that the extreme for the most severe sector equals the omnidirectional value for the required assessment return period and season where applicable. In certain areas 30° sectors may be inappropriate; caution should be exercised if an assessment heading falls marginally outside a sector with higher data. - The downwind (vector) component of the maximum surface flow of the mean spring tidal current is specified rather than the maximum spring tidal current (Section 3.6.1). - Site specific information may be used to determine an appropriate combination of wind driven and surge currents (Section 3.6.1). C3.4 WIND The PRACTICE selects the 1 minute sustained wind for determining the wind loadings on the jack-up. In some instances the wind data will be supplied only for an alternative averaging period. The conversion to the 1 minute sustained value can not be uniquely defined as the conversion can be a function of various parameters, including the wind speed itself. In the absence of site specific data the following formula may be applied [1], providing that the design storm is of longer duration than the supplied averaging period (the supplied averaging period may exceed the storm duration in areas of the world where the extreme winds are due to squalls, thunderstorms, etc.): Vref = Vs[1 - 0.047ln( t t ref s )] where; Vref = wind velocity for reference averaging period required by PRACTICE (1 minute). Vs = wind velocity for supplied averaging period, ts. tref = averaging period required by PRACTICE (1 minute). ts = averaging period for supplied wind velocity. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 12 Mobile Jack-Up Units Rev 3, August 2008 C3.5 WAVES C3.5.1 Determining Wave Heights for Regular and Irregular Wave Analysis The wave heights utilized by the PRACTICE for wave load calculations are related to the return period significant wave height for a three-hour storm, Hsrp. The PRACTICE however recognizes that this data may not always be available to the assessor and therefore provides relationships between Hsrp and Hmax, the individual extreme wave height for the assessment return period with an annual probability of exceedance of 1/return period. The assessment return period is normally taken as 50 years in which case Hmax(50) is the wave height with a 2% annual probability of exceedance. Hsrp and the associated period are normally determined through a direct extrapolation of measured or hindcast site specific significant wave heights. Hmax may be determined either from an extrapolation of the distribution of individual wave heights over the assessment return period or by the application of a multiplication factor to Hsrp. It is noted that the 'extreme wave height' of a regular wave, Hmpm, determined from a 3- hour storm segment is the most probable maximum (MPM) wave height, defined as the distance from the extreme crest to the following trough. Using this definition, the MPM wave height from the 3-hour storm segment is given by: Hmpm = 1.68 Hsrp This relationship is confirmed by the data of [2] for individual storms. However, Hmpm must not be confused with Hmax and must not be used to determine the value of Hsrp on which an assessment is based. This is because Hmax includes site specific considerations of potentially longer durations of storms (including build up and decay) and the additional probability contributions of other return period storms (i.e. 20, 30, 40, 100- year, etc., return period storms). Consequently the ratio Hmax/Hsrp is larger than the ratio Hmpm/Hsrp. A consequence of the site specific nature of the derivation of Hmax is that there is no unique relationship between Hmax and Hsrp applicable to all areas of the world. Thus, if a specified return period maximum wave height is given at a particular location there is no consistent way to derive Hsrp without knowledge of how the maximum (Hmax) wave height was derived originally. Average factors between Hsrp and Hmax have been derived for a North Sea and a Gulf of Mexico location for a 50-year return period. Without further information, the North Sea factors can be generalized to any non-tropical revolving storm area and the Gulf of Mexico factors can be generalized to tropical revolving storm areas. These factors are: Environmental Conditions Hmax/Hsrp Tropical revolving storms 1.75 Non-tropical storms 1.86 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 13 Mobile Jack-Up Units Rev 3, August 2008 The Dean's stream function/Stoke's fifth order theories predict higher peak than trough amplitudes, increasing the maximum velocities and the wetted surface compared with the Airy theory. In Figure C4.4.2 the difference in the profiles is illustrated. Using the same specified wave height this difference may be seen in terms of the overturning moment, base shear or deck displacement. A number of computations were performed to determine the differences due to wave kinematics on selected Jack-up designs. Some results are summarized in Tables C3.5.1 and C3.5.2. See also Appendix C4.B. Table C3.5.1 Regular wave analysis normalized results, CDeDe = 5.13 over the full water depth Theory Water depth m Wave H:T m:sec Crest amp. m Base shear MN Overt. moment MNm Dean's overturning/ other Airy Const. 30 15/14 7.5 3.577 91.607 1.74 Airy Wheeler 15/14 7.5 3.266 82.782 1.93 Stoke's fifth 15/14 10.22 5.211 156.16 1.02 Dean's stream 15/14 10.42 5.243 159.45 1. Airy Const. 70 15/14 28/16 7.5 14.0 2.916 14.121 160.83 677.69 1.12 1.44 Airy Wheeler 15/15 28/16 7.5 14.0 2.563 13.446 138.80 636.53 1.30 1.53 Stoke's fifth 15/14 28.16 8.41 19.17 3.171 18.264 180.80 976.62 1.00 1.00 Dean's stream 15/14 28/16 8.41 19.33 3.161 18.136 180.30 972.54 1. 1. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 14 Mobile Jack-Up Units Rev 3, August 2008 In Table C3.5.2 the deterministic analysis is based on application of a various Hmax to Hs relationships. The Stochastic analysis refers to extreme values determined from time domain analyses by fitting a three parameter Weibull distribution to the response peaks and reading the extreme as the 0.999 fractile, approximating a three hour storm extreme. The results show dependence on the choice of wave kinematics differing with wave height. Table C3.5.2 Scaling factor γd on loads to comply with Airy Wheeler in irregular seas, [11]. BASE SHEAR: Airy Wheeler Airy No stretch Airy Constant Stokes fifth Stochastic irregular seas 1.00 1.03 0.83 - Deterministic 1) 0.79 0.84 0.69 0.66 regular waves 2) 0.66 0.69 0.56 0.66 3) 0.71 0.75 0.61 0.66 4) - - - 0.92 OVERTURNING MOMENT: Stochastic irregular seas 1.00 1.10 0.79- - Deterministic 1) 0.81 0.93 0.69 0.66 regular waves 2) 0.67 0.76 0.56 0.66 3) 0.72 0.83 0.61 0.66 4) - - - 0.93 Water depth 110m, Hs = 13.0m, Tp = Tass = 17.0 sec, uniform current V = 0.4 m/s 1) Hmax = 1.86Hs 2) crest as Stokes 3) Hmax = 1.86Hs 1.07 except Stokes. 4) Hmax = 1.60Hs (PRACTICE recommendation) Wheeler stretching basis for normalized results, i.e.: Airy Wheeler stochastic load = γd (other load) C3.5.1.1 Significant Wave Height for Stochastic Irregular Waves Analysis. Only Airy theory is currently applicable together with a stochastic irregular seas analysis, and in Section 4.4 the Wheeler stretching is recommended for describing the kinematics to the instantaneous surface. It is accepted that the increasing assymetry described by higher order theories such as Stokes is appropriate. The asymmetry can also be seen in recorded data as skewness of the waves, as shown in Figure C3.5.1. Since Airy theory has certain limitations, a practical way to compensate for the assymetry is to increase the significant wave height used as input to the force computations. In order to show that a scaling of significant wave height is appropriate, and to determine the absolute values of the scaling factors, COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 15 Mobile Jack-Up Units Rev 3, August 2008 one needs to decide which theory is correct at a given wave condition. Based on the good fit to test results in wave tank measurements, [6], the Wheeler stretching is found to be a best fit. However, due to the asymmetry of wind generated ocean waves in shallow water, this agreement is judged to be valid only for large water depths. In [7] it is also indicated that a higher peak than trough is appropriate. Here it is assumed that the significant wave height should have a scaling factor close to 1.0 for Wheeler stretching at 110m using irregular wave analysis. At shallower water depths a scaling factor in excess of 1.0 should be due to the wave asymmetry. In [8] a scaling of wave crests is suggested based on the Stokes wave profiles. Comparisons are made both with data for North Sea conditions (d = 70 m), see also Figure C3.5.1, and shallow waters (d ≈ 5.0 m) in the Baltic Sea implying that this may be a general model. A correction proportional to wave steepness is deduced which shows fair agreement with the data. Figure C3.5.1 - Comparison of wave crest elevation predicted skewness and observed data at 70 m in the North Sea [8] The crest height correction formula may be simplified neglecting the higher order terms to be [8]: ηs/η ≈ 1. + 0.6 α3 + 0.5 (α4 - 3) where; ηs = crest elevation by Stokes η = crest elevation by Airy α3 = 2.5 D2 Hs / Tp 2 , α4 - 3 ≈ (1.6α3)2 : Skewness & kurtosis relations D2 = coth (kd) [1 + 3/(2sinh2(kd)] : Depth attenuation k = (2π/T)2/g : Wave number The data and the model indicate that the skewness, α3, is about 0.08 - 0.2 for large seastates at 70 m water depths giving a correction of 1.05-1.12 on the crest height compared with a linear model. The forces on a Jack-up structure increase proportionally as the square (or more) of the elevation. Applying a correction for the square of the bias in wave crest the correction for 70m should be in the range 1.10-1.25, depending on wave steepness. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 16 Mobile Jack-Up Units Rev 3, August 2008 By combining the above suggested formulae a correction for the Wheeler stretching in a stochastic analysis may be deduced as: Hs = 1.0 + 1.5 D2 Hsrp / Tp 2 The D2 factor includes a dependence on the wave number for individual; waves. This is not suitable for the purpose of inclusion in the PRACTICE, since there is no unique wave number for a seastate. The elevation is not the only parameter to be considered and others; are: - the depth attenuation over water depth, - the profiles are not similar in horizontal directions, - and forces at some distance lose correlation. This gives a different scaling than that deduced from the wave crest height only. Based on the above a significant wave height for stochastic/irregular wave analysis using Airy waves and Wheeler stretching is recommended as: Hs = [1 + 10 Hs/Tp 2 exp(-d/25)]Hsrp This removes the direct link to the Stokes profile as suggested in [8], but contains the linear dependence on steepness and a depth dependence with an exponential decay. Further, by inserting the limited range of wave steepness specified in Section 3.5 the scaling may be further simplified. Assuming a peak enhancement factor of γ = 3.5, the peak period may be approximated as Tp/Tz = 1.3, giving a range for 0.046 < Hs/Tp 2 < 0.057 for all areas. A ratio Hs/Tp 2 = 0.05 is therefore introduced, such that the significant wave height is recommended as: Hs = [1 + 0.5 exp(-d/25)] Hsrp The scaling factor should be limited to a water depth above, say 25m. A similar scaling on wave height for Airy/Wheeler stretching is currently being applied indirectly in design specifications, [9], where it is stated that the wave heights according to Airy should be two times the peak amplitude predicted by the Stokes wave profile. The above scaling is an approximation. It would be more correct to account for the wave asymmetry directly in the generation of the sea surface elevation by, for example, the methods indicated in [8]. The significant wave height Hsrp could then be applied directly. Scaling for other stretching techniques combined with Airy waves may be deduced for stochastic, irregular waves and based on computational comparisons for different wave heights and water depths. However, this will not give exactly the same force profile over the leg and discrepancies in force prediction will occur. Such scaling is therefore not included in the PRACTICE. For computational comparisons using this wave height scaling, see also Appendix C4.B. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 17 Mobile Jack-Up Units Rev 3, August 2008 C3.5.1.2 Wave Height for Regular Wave Analyses The selection of wave height to be applied in a particular analysis approach (regular or irregular waves) is recommended based on matching the loads resulting from the combination of the wave height and kinematics models, as recommended in Section 4.4. The scaling of wave heights is introduced as an alternative to the scaling of drag coefficients, using the wave height relation Hmax = 1.86Hs. For regular wave analyses the wave asymmetry is properly accounted for, but the irregularity of the sea surface and the wave spreading may not be modeled properly. As indicated in Tables C3.5.1 and C3.5.2 a reduction factor is required to give similar forces as predicted by an irregular seas simulation if Hmax = 1.86Hs. In [3] a reduction of the drag coefficient by a factor 0.7 is chosen and in [4] a reduction of wave kinematics is chosen. Classification societies generally specify lower CD values than specified in Section 4 and these apply to regular wave analyses. Considering that the computations with regular waves are made with a kinematics model that has been documented in [5] to be somewhat conservative a reduction factor is appropriate to arrive at realistic force estimates. Accepting that a scaling factor on kinematics is applicable, a practical way of implementing this in the PRACTICE is to reduce the wave height to be used for force computations in regular wave analyses. This may be more practical than using a factor on kinematics as most software on the market does not include such a scaling factor. Equivalent wave heights are suggested as: Hdet = 1.60Hsrp The scaling factors on kinematics may be implemented assuming that the load effect is proportional to wave height to the power 2.2, remembering that CD's should not be scaled. As a comparison with previous practices the relationship Hdet ≈ 1.60Hsrp may also be compared with the reduction of CD by a factor 0.7 as recommended in [3] in combination with the wave height Hmax = 1.86Hs. By assuming that load effects are proportional to the ratio of wave heights to the power 2.2, the scaling becomes (1.60/1.86)2.2 = (0.86)2.2 = 0.72, indicating that this is not lower than current practice. The computational results of Table C3.5.2 indicate also that scaling of 0.66 would give similar static forces as the irregular seas simulation at large water depths. See also Appendix C4.B for a comparison of the computational results, related to other practices. C3.5.2 The wave heights specified in the PRACTICE for use in airgap determination will be generally applicable. Special consideration may, however, be required in areas subject to Freak Waves or where the 1.5m clearance will not be adequate to cover the increase in wave height associated with higher return period waves. It should be noted that certain regulatory bodies require the use of higher return period waves (e.g. 10,000 years) for the determination of airgap requirements. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 18 Mobile Jack-Up Units Rev 3, August 2008 C3.5.3 Alternative formulation for wave spectrum The following alternative, and rather restrictive, representation of the wave spectrum by the power density of wave surface elevation Sηη(f) as a function of wave frequency may be used: Sηη(f) = αg2(2π)-4(f)-5exp(-1.25/(Tpf)4)γq where; α = equilibrium range parameter = 0.036 - 0.0056Tp/ Hm0 2 g = acceleration due to gravity q = exp(-(Tpf-1)2/2σ2) σ = spectral peakwidth parameter = 0.07 for Tpf <= 1 = 0.09 for Tpf > 1 Hm0 = estimate of Hs significant wave height (meters) Tp = spectral peak period (seconds) f = frequency (Hz) γ = peak enhancement factor = exp(1/0.287[1-0.1975αTp 4/Hm0 2]) The above definition yields a Pierson-Moskowitz spectrum when γ = 1 and Tp = 5√(Hs) with Tp in seconds and Hs in meters. C3.5.4 Spreading The PRACTICE provides a formulation which may be used to incorporate the effects of wave spreading in the analysis. The power constants recommended [10] imply that the extreme seastate is close to long-crested, and that there is therefore little angular distribution of wave energy about the mean direction. It should be noted that where significant spreading exists it may be non-conservative to assume a long-crested sea. In [4] a reduction formula is suggested which reduces the velocity by a factor 'primarily accounting for wave spreading': ured/u = √[(2n+1)/(2n+2)] where; n = the exponent in the cos2nθ spreading function at Tp, u = the computed velocity for long crested waves, ured = the reduced horizontal velocity. For a range of the spreading exponent, 2 < n < 3, the range of the scaling is 0.91 < ured/u < 0.94. This corresponds to a reduction of the forces by a factor ranging from 0.833-0.875. To use such a spreading factor in reducing overall forces on a structure is debatable, and especially so for jack-up structures. There may be cases where the inclusion of the spreading in irregular seas results in higher forces for some headings. If the leg spacing corresponds to a wave period, inducing opposing wave forces for different legs coinciding with the first resonance period, the forces will in fact be amplified when spreading is included. For jack-ups where the resonance period may often be as high as 4-7 sec., the effect of wave spreading is believed to reduce forces. However, the size of the reduction is dependent on the structure. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 19 Mobile Jack-Up Units Rev 3, August 2008 C3.7 WATER LEVELS AND AIRGAP The PRACTICE references water depths to lowest astronomical tide (LAT). In some instances the water depth may be referenced to Chart Datum. It is modern practice for these reference levels in hydrographic surveys to be the same, however caution should be exercised when using older data or navigation charts and the relation of Chart Datum to LAT should be checked and any necessary corrections applied. See also the Section C3.5.2 regarding wave heights for airgap determination. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 20 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C3 CDeDe = equivalent drag coefficient times effective diameter. d = water depth. D2 = depth attenuation. f = frequency (Hz). g = acceleration due to gravity. H = wave height. Hdet = reduced wave height which may be used in deterministic/regular wave force calculations. Hmax = maximum wave height for a given return period; used for airgap calculations. Hmpm = wave height associated with Hsrp equivalent to the height between the extreme crest and the following trough. Hmo = estimate of Hs significant wave height (meters). Hs = scaled significant wave height to be used in irregular seas simulation (meters). Hsrp = significant wave height for assessment return period. k = wave number. n = the exponent in the Cosnθ spreading function at Tp. q = exp(-(Tpf-1)2/2σ2) Snn(f) = power density of wave surface elevation as a function of wave frequency. tref = wind averaging period required by PRACTICE (1 minute). ts = wind averaging period for supplied wind velocity. T = wave period (seconds). Tp = peak period in wave spectrum (seconds). Tz = zero-upcrossing period of wave spectrum (seconds). u = the computed velocity for long crested waves. ured = the reduced horizontal velocity. V = current. Vref = wind velocity for reference averaging period required by PRACTICE (1 minute). Vs = wind velocity for supplied averaging period, tu. α = equilibrium range parameter = 0.036 - 0.0056Tp / Hm0 2 α3 = skewness. α4 = kurtosis. γ = peak enhancement factor = exp(1/0.287[1-0.1975αTp 4/Hm0 2]), for Tp in seconds and Hm0 in meters. γd = scaling of drag forces. ηs = crest elevation by Stokes. η = crest elevation by Airy theory. σ = spectral peakwidth parameter = 0.07 for Tpf <= 1 = 0.09 for Tpf > 1 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 21 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C3 1 Det Norske Veritas, Classification Notes No 30.5, 'Environmental Conditions and Environmental Loads', Høvik, March 1991. 2 Heideman J.C. and Schaudt K.J., 'Recommended Equations for Short-term Statistics of Wave Heights and Crest Heights', 1 April 1987. 3 'Practice for the Site Specific Assessment of Jack-up Units', By Marine Technology division, SIPM, EDP-5, The Hague, May 1989. 4 American Petroleum Institute, proposal for an update of the API-RP2A, 'Hydrodynamic Force Guidelines for U.S. Waters', received 6 February 1992. 5 L. Skjelbreia and J.A. Hendricksen, 'Fifth-order Gravity Wave Theory', Proceedings of Seventh Conference on Coastal Engineering, 1961, pp. 184-196. 6 J.E. Skjelbreia, G. Berek, Z.K. Bolen, O.T. Gudmestad, J.C. Heideman, R.D. Ohmart, N. Spidsoe and A. Torum, 'Wave Kinematics in Irregular Waves', OMAE, Stavanger, 1991. 7 Health and Safety Executive, Petroleum Engineering Division, 'Offshore Installations: Guidance on Design, Construction and Certification', London, 1990. 8 S.R. Winterstein, E.M. Bitner-Gregersen and K. Ronold, 'Statistical and Physical Models of Nonlinear Random Waves', OMAE, Volume II, Safety and Reliability, Stavanger, 1991, pp.23-31. 9 O.J. Andersen, E. F`rland and S. Haver, 'Design Basis, Environmental Conditions, Statfjord', Statoil Report no. F&U-ST 88007, Stavanger, April 25, 1988. 10 S. Haver, 'On the Modelling of Short Crested Sea for Structural Response Calculations', EurOMS, Trondheim, 20-22 August 1990. Other project reports and related technical notes: 11 D. Karunakaren, 'Scaling of Hydrodynamic Loads According to Computational Models', Technical memo no. 710762, SINTEF, Trondheim, July, 1991. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 22 Mobile Jack-Up Units Rev 3, August 2008 C4 COMMENTARIES TO CALCULATION METHODS – HYDRODYNAMIC AND WIND FORCES C4.1 INTRODUCTION The main objective of this Section is to provide documentation of the numbers, methods and formulations of the Section 4 of the PRACTICE. This Section is limited to considering Jack-Up specific methods for wind loading on legs and hulls and hydrodynamic forces acting on the legs under the action of waves and current. Typical jack-up leg designs consist of legs with an open lattice frame structure with typical member dimensions of 0.25-1.0m in diameter. A special feature are the racks fitted to the chord elements for jacking purposes. The fact that jack-ups are mobile will also limit the marine growth. The models, methods and coefficients for computing the forces are considered together in the development of PRACTICE Section 4, and represent a consistent method such that the whole Section should be considered in its entirety. This means that no coefficients should be taken from this Section or Section 4 of the PRACTICE unless the corresponding method is applied. The Section is organized such that the main sub-sections have the same numbers as the corresponding section in the PRACTICE. This means that Section C4.2 in this report corresponds to section 4.2 in the PRACTICE and so on. C4.2 WIND FORCE CALCULATIONS The wind force acting on each block of the jack-up is obtained by multiplying the pressure (which accounts for the elevation and shape of the block - see C4.2.2 and C4.2.3 respectively) by projected area. The total wind force on the jack-up can then be obtained by summing the wind forces over all the blocks. Shielding effects are not normally included in the calculation, except that the wind area of the hull and associated structures (excluding derrick and legs) may normally be taken as the profile area viewed from the direction under consideration. The wind speed varies with height since the boundary layer friction (which in increased by the roughness of the sea surface) retards the wind near the sea surface. The lower layers then retard those above them, resulting in increasing velocity above the sea level, until the retarding forces reduce to zero. A wind profile is normally used to represent the variation of wind speed with respect to height. The PRACTICE recommends a power law of 10 (N = 10) to represent the wind. The wind speed measured at 10m above the mean sea level is normally used as the reference in defining the wind speed profile. Alternatively, the height coefficients (Ch) listed in Table 4.1 can be used to determine the wind speed at various heights. Where a block has a vertical extent of more than 15m, it is recommended that it is subdivided and the appropriate height coefficients are applied to each part of the block. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 23 Mobile Jack-Up Units Rev 3, August 2008 The shape coefficients for various typical components of a jack-up are given in Table 4.2. Items with 'solid' faces are treated as individual blocks. A different approach is used for open lattice structures, such as derricks, crane booms, helideck support structure, flare booms and raw water towers, etc. Here Table 4.2 recommends the use of 50% of the total projected profile area of the item (e.g. 50% of the product of the derrick width overall and the vertical extent of block under consideration) in association with the appropriate shape coefficient for the isolated shapes comprising the lattice. For leg structures, the equivalent hydrodynamic coefficients on lattice legs may be taken from Section 4.6. These will generally be the same as those for clean legs in large velocities and long waves and hence the smooth values are generally recommended. C4.3 HYDRODYNAMIC FORCES C4.3.1 General Jack-up leg sections are complex structures, usually made of slender members. The best engineering tool available for computation of hydrodynamic forces is Morison's equation. However, the limitations of Morison's equation should be recognized. For single large diameter members/legs, which may be an alternative to lattice legs, more appropriate theories and formulations for the inertia forces should be applied. MacCamy and Fuch's [60] corrections on the inertia coefficients of vertical elements may be an alternative for those structures. A limitation on the application of Morison's equation to predict wave loads is implemented. The limitation is set to: λ > 5Di (4.3.1) where; λ = wave length and Di = reference dimension of individual leg members (within a lattice leg). The above limitation implies that the members should be small compared with the waves. Morison's equation [30] is an empirical relation given by a drag term plus an inertia force term as: ΔF = ΔFdrag + ΔFinertia = 0.5 ρ CD D | ux | ux + ρ CM (πD2/4) 􀀅ux (4.3.2) where; CD = the drag coefficient. CM = the inertia coefficient. ux, 􀀅ux = the horizontal water particle velocity and acceleration. D = the tubular diameter. ρ = the density of fluid surrounding the tubular. The above equation was established to be used for vertical circular cylinders in waves, but has later been modified and generalized to account for current, inclined members and relative velocity and acceleration. These extensions are further defined for use in the PRACTICE and discussed in the following sections. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 24 Mobile Jack-Up Units Rev 3, August 2008 C4.3.2 Drag forces For the drag part of the equation the extension from Morison's original formula is made as: ΔFdrag = 0.5 ρ CD D | vn | vn (4.3.3) where vn is now introduced as the relative particle velocity normal to the local member axis including current, taken as: vn = un + VCn - α 􀀅r n (4.3.4) where; un + VCn = the combined particle velocity from wave and current by vectorial summation normal to the member considered. 􀀅r n = the velocity of the considered member normal to its axis and in the direction of the combined particle velocity. α = 0, if an absolute velocity is to be applied, i.e. neglecting the structural velocity. = 1, if relative velocity is to be included. May only be used for stochastic/random wave force analyses if: Ured = uTn/Di ≥ 20. where; u = particle velocity, Tn = first natural period of surge or sway motion Di = the reference diameter of a chord. In the above definition of combined velocity, current is included. This should be acceptable as the member does not distinguish between the velocity due to current or wave motions. The backflow of the wake is different in combined wave and current fields, (KC dependence) but this has a small influence on the prediction of the largest force in an extreme wave for single members of diameters typical for jack-ups, see Section C4.7.2.6. For inclined members the above definition implies that the procedure to arrive at the force components is first to determine the particle velocity component normal to the member axis, then determine the force normal to the member axis and thereafter to determine the force components in the global directions. This implies that the force component along the member is neglected. On the inclusion of the relative velocity there has been some reluctance to directly accept the extension to the original Morison's equation. Intuitively the extension should be correct using the same argument as for current forces as the member only experiences the flow field passing locally. However, the displacements of the members are quite small and there has been few data to support such an extension as pointed out in [34]. In [55] test results show that for small amplitude motions the damping may be overpredicted when the relative velocity is included. However, for a typical jack-up, with member diameters less than 1m and natural periods around 5.0 seconds, the sensitivity to member displacement is not large because the parameter Ured = uTn/Di ≈ 20 or more in an extreme sea state, see Figure C4.3.1. In addition, the Christchurch bay test results show that the relative velocity formulation gives good prediction of the inine loading [44], 'correctly predicting the important hydrodynamic damping at the resonant frequency'. From this it may be concluded that the relative velocity formulation is probably applicable for jack-up structures. A limitation is introduced to avoid any significant overprediction of damping. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 25 Mobile Jack-Up Units Rev 3, August 2008 The reduced velocity Ured may be computed for a wave height equal to the significant wave height and using the first natural period normally corresponding to the fixed condition soil parameters. In practical cases it is suggested to evaluate Ured for a majority of members close to the sea surface, and to include relative velocity either for all or no members. The relative velocity formulation is in effect similar to the inclusion of damping reaction forces. All predictions of damping are uncertain, and compared with other damping estimates the relative velocity formulation is judged to be reasonably well estimated. This additional damping from the relative velocity formulation should be considered when choosing the structural/proportional damping coefficient. A low structural damping should be considered when the relative velocity is included. A procedure to combine the forces on several individual members into one member with equivalent diameter and drag coefficient to be used with the horizontal water particle velocities is discussed in Section 4.6. Figure C4.3.1 Oscillating drag coefficient vs. motion amplitude to diameter ratio xo/D for given reduced velocities [55] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 26 Mobile Jack-Up Units Rev 3, August 2008 C4.3.3 Inertia forces These forces are not dominant for extreme loads of typical jack-up lattice legs. A more comprehensive model could be applied to include relative accelerations (noting that in this case the added mass should not be included in the structural model). In the RP the formulation is given as: ΔFinertia = ρ CM (πD2/4) 􀀅un (4.3.5) where; ΔFinertia = normal force per unit length of member (in this case the member is vertical and the force horizontal). ρ = density of fluid surrounding the tubular. CM = inertia coefficient. D = diameter of the member. 􀀅un = water particle acceleration normal to the member. This implicitly defines how to treat inclined members. However, for inclined members the horizontal force may alternatively be determined by accounting for the inclination on the added mass part of the inertia force, but not on the Froude-Krylov part of the force. The horizontal inertia force is hence computed as: ΔFinertiaH = ρπD2/4 [(CM-1)sin2βi + 1] 􀀅un (4.3.6) where βi is the angle between the particle acceleration and the element orientation as defined in Figure 4.2. It should be noted that the vertical particle acceleration will also provide a horizontal component on inclined braces. For global force calculations this will generally be unimportant as the loadings on different braces at different angles will tend to cancel out. C4.4. WAVE THEORIES C4.4.1 General In general there are two different computational methods with corresponding suitable wave theories; - Deterministic regular wave analysis, and - Stochastic irregular or random wave analysis. For the deterministic regular wave analysis all formulated wave theories may be chosen from a mathematical point of view. For shallow waters however, the choice of wave theory is limited to those properly predicting wave asymmetry and the corresponding change in wave kinematics. For the stochastic irregular wave analysis only the linear Airy wave theory, or variations of Airy theory are suitable. Airy wave theory does not fully describe the wave kinematics behavior since this wave theory implies symmetric waves, which are not always applicable for shallow water. This will limit the application of this type of analysis to deeper and intermediate water depths and is considered further in Section 3.5.1, see Appendix C4.B. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 27 Mobile Jack-Up Units Rev 3, August 2008 C4.4.2 Regular wave analysis Currently there are a number of wave theories that are applied in the analysis of jack-up platforms. In most cases the deterministic computations are performed using Stokes fifth order [42] or Dean Stream function [40] theories. The Dean Stream function theory shows the best fit to test results, [40,41], for shallow water waves. The difference in overall forces from these two wave theories will however be small at large to intermediate water depths and for low wave steepnesses. Figure C4.4.1 is included in the PRACTICE in a linear scale to guide the selection of the appropriate wave theory for deterministic analyses. Only the Dean stream and Stokes wave theory are recommended here in order to limit the range of possible choices, reducing the scatter in wave force predictions. C4.4.3 Irregular wave analysis For the irregular waves analysis, Airy's wave theory is the only possible choice using the principle of sum of independent wave components as implied in standard irregular seas time domain simulation and frequency domain solutions. For both the Dean Stream and Stokes wave theories there are implicit phase dependencies between wave components at different frequencies. To account for changes in wetted surface a modification of the Airy wave theory is required, introducing the surface elevation as a parameter in the kinematics. A number of such stretching methods have been proposed in literature. One simple method, the Wheeler stretching method [37], compares well with test results in model tank measurements [38]. Even for the Wheeler stretching method there exist different variations. The chosen definition is that originally suggested in [37], to substitute the true elevation at which the kinematics are required with one which is at the same proportion of the mean water depth. This can be expressed by: z' = z d − + ζ 1 ζ / (4.4.1) where; z = The elevation at which the kinematics are required. (Coordinate measured vertically upward from the mean water surface) z' = modified coordinate to be used in particle velocity formulation ζ = The instantaneous water level (same axis system as z) d = the mean, or undisturbed water depth (positive) This method causes the kinematics at the surface to be evaluated from linear theory expressions as if they were at the mean water level. If a frequency domain analysis is to be applied in extreme response predictions, it is recommended to use linearization with respect to a finite wave height, Hmax defined in 3.5.1, however damping should be linearized using a lower wave height. Stochastic linearization implies the use of a unit wave height and when combined with the assumption of Gaussian statistics the extreme response may be underpredicted, see Figure C4.4.3. For fatigue computations stochastic linearization, [51], is recommended as fatigue damage is not dominated by the extreme wave heights, however consideration should be given to local loads arising from the finite wave height. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 28 Mobile Jack-Up Units Rev 3, August 2008 Notes 1) None of these theories is theoretically correct at the breaking limit. 2) Wave theories intended for limiting height waves should be referenced for waves higher than 0.9Hb when stream function theory may underestimate the kinematics. 3) Stream function theory is satisfactory for wave loading calculations over the remaining range of regular waves. However, stream function programs may not produce a solution when applied to near breaking waves or deep water waves. 4) The order of stream function theory likely to be satisfactory is circled. Any solution obtained should be checked by comparison with the results of a higher order solution. 5) The error involved in using Airy theory outside its range of applicability is discussed in the background document. Nomenclature Hmax/gTass 2 = Dimensionless wave steepness d/gTass 2 = Dimensionless relative depth Hmax = Wave height (crest to trough) Hb = Breaking wave height d = Mean water depth Tass = Wave period L = Wave length (distance between crests) g = Acceleration due to gravity Figure C4.4.1 : Range of validity of different wave theories [52,58] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 29 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.4.2 : Surface elevation, and velocity profiles for deterministic regular waves Figure C4.4.3 : Linearization w.r.t. wave heights [47] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 30 Mobile Jack-Up Units Rev 3, August 2008 C4.5. CURRENT C4.5.1 General The current specified for a specific site is to be included as specified in section 3.6 of the PRACTICE. Interpolation between the data points may be required and linear interpolation is recommended for simplicity. C4.5.2 Combination with wave particle velocities It should be emphasized that the wave and current velocities are to be treated together, as a sum of separate force contributions will significantly underestimate the hydrodynamic forces. C4.5.3 Reduction of current by the actuator disc formula The current velocity will be reduced due to the presence of the structure in the current flow field. An estimate of the reduction of the steady flow velocity may be found by [53]: VC/Vf = [1 + Σ(CDiDi)/4W]-1 ≥ 0.7 (4.5.1) where; VC = the reduced current velocity to be used in analysis. Vf = the observed far field current. CDi = the drag coefficient of an element i. Di = the element diameter of element i. W = the width of the structure. Several limitations of the above relation are discussed in [53,56] and a lower limit to the reduction of the current velocity is suggested to be 0.7. The above equation contains a sum of CDi and diameters Di, but is not explicit with respect to inclined members. The summation ΣCDiDi is similar to the computation of the equivalent drag coefficient and diameter, CDeDe, in Section 4.6 of the PRACTICE, where member inclination is accounted for. Since the equation should be considered for separate groups of elements [53], it suggested to apply the formula for each leg and use the following format: VC = Vf [1 + CDeDe/(4D1)]-1 (4.5.2) where; VC = the current velocity to be used in the hydrodynamic model, VC should not be taken less than 0.7Vf. Vf = the far field (undisturbed) current. CDe = equivalent drag coefficient, as defined in 4.6.6. De = equivalent diameter, as defined in 4.6.6. D1 = face width of leg, outside dimensions. For structures where the hydrodynamic geometry varies significantly with depth, the blockage factors can be computed for different depths. In view of the reduced drag above MSL (due to lack of marine growth) it may be appropriate to calculate current blockage for the stretched part of the current above MSL separately. C4.5.4 Current stretching It is suggested to let the profile follow the surface elevation by changing the coordinate system similarly to that of the Wheeler stretching defined by equation 4.4.1. The current profile is recommended in Section 3.6.2. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 31 Mobile Jack-Up Units Rev 3, August 2008 C4.6. LEG HYDRODYNAMIC MODEL C4.6.1 General The hydrodynamic modeling of the leg of a jack-up may be carried out by utilizing either 'detailed' or 'equivalent' techniques. In both cases the geometric orientation of the elements are accounted for. The hydrodynamic properties are then found as described below: 'Detailed Model' All relevant members are modeled with their own unique descriptions for the Morison term values and with correct orientation to determine vn and 􀀅un and the corresponding drag coefficient times diameter CDD = CDiDi and inertia coefficient times sectional area CMA = CmiπDi 2/4, as defined in Section 4.7. 'Equivalent Model' The hydrodynamic model of a bay is comprised of one, 'equivalent', vertical tubular to be located at the geometric center of the actual leg. The corresponding (horizontal) vn and 􀀅un are to be applied with equivalent CDD = CDeDe and CMA = CMeAe, given in 4.6.5 and 4.6.6. The model should be varied with elevation, as necessary, to account for changes in dimensions, marine growth thickness, etc. C4.6.2 Length of members Lengths of members are normally to be taken as node-to-node distance of the members, in order to account for small non-structural items. C4.6.3 Spudcan A criteria for considering the spudcan is suggested such that the effect of the wave and current forces on the spudcan may normally be neglected at deep water or deep penetrations. However, there may be special cases with e.g. large spudcans in combination with high currents that should be considered also outside the suggested criteria. C4.6.4 Shielding and Solidification Shielding is normally neglected for computations of the hydrodynamic model as presented herein. The shielding is dependent on KC- and Re- numbers. Since it is difficult to quantify shielding, and shielding in waves is less than in constant flow [45,62], shielding is neglected. The same criteria are used for solidification as for shielding such that both effects should be considered if advantage is taken due to shielding in wave and current loads. According to [56] shielding is recommended to be neglected for S/D ≤ 4 for an array of elements, where S is the outer diameter of the array and D is the diameter of individual elements. This is also considered in [45]. If information on shielding is obtained from experiments, care should be taken to distinguish between shielding and the effect discussed in C4.5.3. These effects are different, but could possibly be confused in tests on small models in large tanks. Solidification is an increase of wave forces due to interference from objects 'side by side' in the flow field. This is normally not included in the hydrodynamic coefficient formulation for jack-ups since shielding is also neglected. Jack-up rigs are usually space frame structures with few parallel elements in close proximity so that this effect is usually not important. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 32 Mobile Jack-Up Units Rev 3, August 2008 In [45] solidification effects are quantified for two elements and for a group of elements. The drag coefficient may increase 100% if two tubulars are placed side by side, or be reduced for a group of elements, e.g. a conductor array, where shielding is also present. The effect is less than 10% in the worst direction and is therefore suggested omitted in the PRACTICE, when: As/At < 0.5 where; As = sum of projected areas for all members in the considered plane At = the total projected envelope area of the considered plane. Solidification should be considered if shielding is included. C4.6.5 Equivalent drag coefficient In order to comprise the information on drag forces for individual members of a lattice leg into an equivalent vertical member over the bay length s, a fixed diameter and a directional dependent drag coefficient is specified. This model accounts for the geometrical orientation of the individual members. In this model the principle of no shielding and no blockage is assumed. The equivalent diameter is recommended such that the inertia coefficient normally will follow without any further computations. The equivalent drag coefficient, CDe, times the equivalent diameter, De, is specified. If another reference diameter De is preferred, the product of CDeDe should in any case be equal to that specified in Section 4.6.5 of the PRACTICE. The expression for CDei may be simplified for horizontal and vertical members as follows: - Vertical member (e.g. a chord) : CDei = CDi (Di/De) - Horizontal member : CDei = sin3αi CDi (Dili/Des) C4.6.6 Equivalent Inertia coefficient The equivalent value of the inertia coefficient, CMe, and the equivalent area, Ae, to be used in Section 4.3.3, representing the CMA chosen as: CMe = may normally be taken as equal to 2.0 when using Ae = 1.0 for flat plates (brackets). Ae = equivalent area of leg per unit height = (Σ Ai li)/s. Ai = equivalent area of element = π Di 2/4. Di = reference diameter as defined in Section 4.7. The reference diameters Di and corresponding area of member Ae, are chosen such that the use of an inertia coefficient CMe = 2.0 or CMe = 1.0 is consistent with the inertia forces for chords and brackets respectively. A conservatism is present since the inertia coefficient for rough tubulars is set to 1.8 and there is no reduction of forces for inclined members. For normal lattice leg designs the conservatism will not play any significant role as the drag forces are dominant. The inertia force will also be dominated by chords due to their larger diameter, such that the conservatism is judged to be insignificant for extreme wave forces. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 33 Mobile Jack-Up Units Rev 3, August 2008 If, however, a more accurate model is wanted an alternative is given using the individual member inertia coefficients, as specified in Section 4.7 of the PRACTICE, and including the effect of inclined members. The CMe coefficient is then determined by the summation shown in Section 4.6.6 of the PRACTICE. This model is in closer agreement with the 'detailed model'. It should be stressed that the coefficients must be defined together with their reference dimensions Di. As comments to this formulation the following may be observed: - for horizontal members with flow along the length axis the inertia coefficient is: CMei = 1.0 - for a vertical rough tubular the inertia coefficient will be: CMei = 1.8 - for other vertical members the inertia coefficient will be: CMei = 2.0 - for other flat plates (brackets) the inertia coefficient will be: CMei = 1.0 C4.7 HYDRODYNAMIC COEFFICIENTS FOR LEG MEMBERS C4.7.1 General The coefficients determined herein are based on tests where the particle velocities and accelerations are measured simultaneously as the forces, usually in a controlled environment. This is the logical way to determine the loading coefficients. However, the important result in engineering is the overall forces predicted by the Morison's equation over the Jack-up legs. Since some wave theory has to be applied, which does not perfectly predict the wave particle motions in all cases, additional scaling is suggested in Section 3.5 of the PRACTICE, see also Appendix C4.B. This is important to consider when reading this chapter as the stated coefficients may be somewhat larger than those applied in other recommendations or classification rules. C4.7.2 Hydrodynamic Coefficients for Tubulars C4.7.2.1 General; There exists a wealth of data on hydrodynamic coefficients (drag and inertia coefficients) for tubulars, mainly from model tests. A number of model tests have been performed in wind tunnels, others in oscillating water environment or in steady water flow, while (to our knowledge) only a few model tests have been performed in a wave environment. In addition a few full scale tests have been reported. In the following section (Section C4.7.2.1-7) an overview is given of the literature that has been applied for the purpose of recommending values for the hydrodynamic coefficients of jack-up platforms. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 34 Mobile Jack-Up Units Rev 3, August 2008 Before choosing the appropriate hydrodynamic coefficients for tubular parts of jack-up platforms the following questions have to be answered: - Are the coefficients to be used for a fatigue analysis or an ultimate strength analysis? - Are the tubular parts smooth or rough, and if they are rough what is the roughness to be applied? The parameters to be considered in determining the hydrodynamic coefficients are; Keulegan-Carpenter number KC = U T D m Reynolds number Re = UD ν Relative roughness = k D where; k = roughness height D = diameter Um = maximum orbital particle velocity T = wave period U = flow velocity at the depth of the considered element. ν = kinematic viscosity of water (ν ≈ 1.4 x 10-6 m2/sec, t = 10°C) Concerning the first question above, it is important to determine the range of Reynolds numbers and Keulegan-Carpenter numbers of interest. Both the drag coefficient CD and the inertia coefficient CM are dependent on the Reynolds number and the Keulegan-Carpenter number. In the ultimate strength case one is interested in the CD and CM coefficients in relatively long and steep waves, i.e. wave steepness S = Hs/λ in the range 1/10-1/15. A typical ultimate strength case may for example be, a tubular with diameter D = 0.3 m standing in a seastate with average zero-upcrossing period Tz = 10 secs. (λ = 156 m) and significant wave height Hs = 13.0 m. The representative water particle velocity for this wave will be: UW = H T s z π = 4.1 m/s. Assuming a current velocity UC of about 1.0 m/s, the total water particle velocity will be U = UW+UC = 5.1 m/s. This results in the following Reynolds number and Keulegan-Carpenter numbers (close to the water surface): Re = UD ν = 1.1 106, KC = UT D z = 170 This means that in the ultimate strength case we are dealing with high KC-numbers and post-critical Re-numbers. Sarpkaya (see for example [4]) uses a parameter β = Re/KC to describe the test environment. In the ultimate strength environment described above, the value of β is approximately 6500. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 35 Mobile Jack-Up Units Rev 3, August 2008 A typical fatigue case may for example be the same tubular in a seastate with Tz = 6 secs. (λ = 56 m) and Hs = 5.6 m. In this case the representative water particle velocity will be UW = Hsπ/Tz = 2.9 m/s. In the fatigue case, current is not part of the water particle velocity, which is to be applied. This results in the following Reynolds number and Keulegan Carpenter number (close to the water surface): Re = 0.62 106, KC = 58. This means that post-critical Re-numbers and relatively high KC-numbers are also to be dealt with in the fatigue case. Sarpkaya's β parameter has a value β = 10860 for the described fatigue case. It may be concluded that, in general, for jack-up tubulars, the following ranges of Renumbers and KC-numbers will be of interest: - Re-numbers: Ultimate Strength, roughly from Re ≈ 1.0x106 - 4.5 x 106 Fatigue, roughly from Re ≈ 0.5x106 - 1.0 x 106 - KC-numbers: Ultimate Strength, KC > 100 Fatigue, KC ≈ 25 - 60 Since quite a large amount of the literature survey is dealing with papers written by Sarpkaya, the following range of Sarpkaya's β-parameter may be regarded to be of interest: β ≈ 6000 - 20000 (depending on the KC-number). The answer to the second question concerning the roughness of the tubulars will depend largely on type of paint used and the smoothness of the steel surface, whether the tubular is new or has been in the water for quite some time (marine growth), or whether the tubular mainly stays in air, etc. Smooth cylinders are defined as cylinders having a roughness k/D < 0.0001, while rough cylinders are assumed to have a roughness k/D > 0.004 (i.e. highly rusted steel k/D ≈ 0.005-0.01). Marine roughness due to marine growth implies a roughness in the range k/D ≈ 0.01-0.15. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 36 Mobile Jack-Up Units Rev 3, August 2008 C4.7.2.2 Literature Survey and Recommended Values In Table C4.7.1 a survey result is presented of relevant literature with respect to inertia coefficients (CM) and drag coefficients (CD) for tubulars. Of course, there exists more relevant literature than that presented in Table C4.7.1, but it should give a reasonably representative overview. Table C4.7.1 : Survey of Relevant Literature on CM and CD values for Tubulars Source Geometric Shape Re-Number KC-number CD CM Comments Keulegan Smooth Cylinder 0.1-0.3 105 25-50 1.3-1.5 1.3-1.8 Sub-Critical Carpenter 0.1 105 >100 1.0-1.2 2.4-2.6 and Critical 1958 [1] Flow. Low Re-numbers. Sarpkaya Smooth Cylinder >0.5 106 20-40 0.6-0.7 1.7-1.8 Post-Crit. 1976 [2] >0.7 106 60-100 0.6-0.7 1.7-1.9 Oscillating Flow. Rough Cylinders Sand k/D = 0.005 >0.5 106 20-40 1.5-1.7 1.2-1.4 Post-Crit. k/D = 0.01 1.6-1.8 1.2-1.4 Oscillating Roughened k/D = 0.02 1.7-1.9 1.1-1.3 Flow. Sand k/D = 0.005 >0.5 106 60-100 1.4-1.6 1.5-1.7 Post-Crit. k/D = 0.01 1.5-1.6 1.4-1.6 Oscillating Roughened k/D = 0.02 1.6-1.7 1.4-1.6 Flow. Hogben Smooth Cylinder >1.0 106 >25 ≈0.6 ≈1.5 Post-Crit. et al. Flow. 1977 [3] Rough Cylinders Post-Crit. Survey k/D = 0.0002 >1.0 106 >25 0.6-0.7 Flow. Paper k/D = 0.002 >0.5 106 >25 ≈1.0 State of k/D = 0.01 >0.5 106 >25 ≈1.0 the Art k/D = 0.05 >0.1 106 >25 ≈1.25 1977 Sarpkaya Smooth Cylinder >0.1 106 25-40 0.6-0.8 1.5-1.7 Critical - et al. Super-Crit. 1982 [4] Oscillating Rough Cylinder >0.1 106 25-40 1.5-1.7 1.0-1.2 Flow. k/D = 0.01 β = 4000. Sarpkaya Smooth Cylinder ≈0.1 106 25-40 0.7-0.8 1.5-1.7 Critical - et al. ≈0.15 106 60 0.6-0.65 1.5-1.6 Super-Crit. 1984 [5] Oscillating Rough Cylinder ≈0.1 106 25-40 1.4-1.5 1.4-1.6 Flow. k/D = 0.01 ≈0.15 106 60 1.4-1.5 1.5-1.6 β = 2500. Sarpkaya Rough Cylinder 0.1-0.2 106 25-40 1.4-1.5 1.0-1.3 Critical - et al. k/D = 0.01 Super-Crit. 1985 [6] ≈0.21 106 50 1.4-1.5 1.2-1.3 Oscillating Flow. β = 4200. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 37 Mobile Jack-Up Units Rev 3, August 2008 Source Geometric Shape Re-Number KC-number CD CM Comments According to Sarpkaya, available data with current + oscillatory flow substantiate the fact that drag coefficients obtained from tests at sea in general will be smaller than those obtained under laboratory conditions. Sarpkaya Smooth Cylinder 0.2-0.3 106 20-25 0.6-0.7 1.6-1.8 Super-Crit. 1985 [7] Oscillating Flow. β = 11240. Sarpkaya Smooth Cylinder >0.5 106 25-40 0.6-0.8 1.5-1.8 Post-Crit. 1985 [8], >0.5 106 >50 0.6-0.7 1.6-1.8 Oscillating 1986 [9] Flow. Survey Rough Cylinder >0.5 106 25-40 1.4-1.8 1.2-1.4 Articles k/D = 0.02 >0.5 106 >50 1.4-1.6 1.3-1.5 Nath Smooth Cylinder ≈0.5 106 ∞ 0.4-0.5 Super-Crit. 1982 [10] Steady Flow. Rough Cylinder k/D = 0.02 ≈0.5 106 ∞ 0.9-1.0 Post-Crit. k/D>0.1 ≈0.5 106 ∞ 1.0-1.2 Steady Flow. Smooth Cylinder 0.15-0.2 106 15-25 0.3-0.6 0.8-1.4 Super-Crit. Oscillating Rough Cylinder Flow. k/D = 0.02 0.15-0.2 106 15-25 0.6-1.0 0.4-1.0 k/D>0.1 0.15-0.2 106 15-25 1.0-2.0 0.8-2.3 There is very large scatter in the data presented by Nath. Bearman Smooth Cylinder 0.15-0.5 106 ≈20 0.6-0.7 1.4-1.5 Super/Postet al. Crit. Flow, 1985 [11] Regular Waves. The authors present results for random waves as well, but it is difficult to draw any conclusion from these results. Kasahara Smooth Cylinder 0.5-1.0 106 20-40 0.5-0.6 1.6-1.8 Post-Crit. et al. Oscillating 1987 [12] Rough Cylinder Flow. k/D = 0.0083 0.5-1.0 106 20-40 1.1-1.4 1.3-1.7 Large Scatter ≈50 1.1-1.2 1.6-2.3 in CM-values. k/D = 0.0042 0.5-1.0 106 20-40 0.9-1.3 1.3-2.1 ≈50 0.9-1.1 1.6-2.1 Chaplin Smooth Cylinder ≈0.2 106 ≈20 0.6-0.7 1.4-1.5 Super/Post- 1988 [13] Crit. Oscillating Flow. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 38 Mobile Jack-Up Units Rev 3, August 2008 Source Geometric Shape Re-Number KC-number CD CM Comments Davies Smooth Cylinder >0.5 106 ≈20 0.6-0.7 1.5-1.6 Post-Crit. et al. Flow, Reg. 1990 [14] Waves. Smooth Cylinder >0.5 106 ≈18 0.5-0.7 1.5-1.7 Post-Crit. Flow. Random Waves. The authors conclude that for smooth cylinders and KC>4, drag and inertia coefficients in periodic waves may be used to represent average CD- and CM- values in random waves. Roden- Smooth Cylinder >1.0 106 ∞ ≈0.6 Post-Crit. busch Rough Cylinder Steady Flow et al. k/D = 0.02 >1.0 106 ∞ 0.9-1.1 (Steady Tow). 1983 [15] Smooth Cylinder >1.0 106 >30 0.6-0.7 1.6-1.7 Post-Crit. Rough Cylinder Oscillak/ D = 0.02 >1.0 106 >30 1.4-1.5 1.1-1.3 ting Flow (Forced Motion). Smooth Cylinder >1.0 106 20-40 0.6-0.8 1.4-2.0 Post-Crit. Rough Cylinder Random Flow k/D = 0.02 >1.0 106 20-40 1.0-1.8 1.0-1.9 (Forced Motion). Smooth Cylinder >1.0 106 60-90 0.6-0.8 1.5-1.7 Post-Crit. Rough Cylinder Random Flow k/D = 0.02 >1.0 106 60-90 1.1-1.4 1.0-1.4 (Forced Motion). The random tests show relatively large spread especially for the lower KC-numbers (20-40). Roden- Smooth Cylinder >1.0 106 >60 0.65-0.75 1.5-1.7 Post-Crit. busch Random Flow et al. Rough Cylinder (Forced 1986 [16] k/D>0.0005 >0.5 106 >60 1.1-1.3 1.1-1.5 Motion). Theopha- Rough Cylinder Post-Crit. natos k/D = 0.005 >0.8 106 0.95-1.05 Steady Flow et al. k/D = 0.0095 1.0-1.1 (Steady Tow). 1989 [17] k/D = 0.025 1.15-1.25 => Sand Rough. ----------------------------------------------------------------------- k/D = 0.049 1.15-1.25 k/D = 0.098 1.3-1.4 => Pyramids ----------------------------------------------------------------------- k/D = 0.067 1.2-1.3 => Mussels Klopman "Rough" Cylinder Post-Crit. et al. k/D = 0.00012 ≈0.5 106 ≈15 0.6-0.9 1.3-1.6 Random Waves. 1990 [18] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 39 Mobile Jack-Up Units Rev 3, August 2008 Source Geometric Shape Re-Number KC-number CD CM Comments Heideman Smooth Cylinder >0.2 106 15-30 0.5-1.2 Post-Crit. et al. >0.2 106 >30 0.6-0.8 1.2-1.9 Random Waves. 1979 [19] Rough cylinder Ocean Test k/D≈0.03-0.05 >0.2 106 15-30 0.9-1.8 Structure. >0.2 106 >30 0.8-1.3 0.9-1.7 Large spread for lower KC-numbers (< 30). Authors state that for large KC-numbers (> 30), smooth cylinder CD approaches an asymptote CD = 0.68, while rough cylinder CD approaches an asymptote CD = 1.0. Tests performed in an ocean environment. Nath Rough Cylinder Barnacles: Post-Crit. 1988 [20] k/D = 0.073 ∞ 0.95 Steady Flow. k/D = 0.104 ∞ 0.98-1.2 Artificial Hard Fouling: Post-Crit. k/D = 0.078 ∞ 0.98-1.2 Steady Flow. Wolfram Rough Cylinder Mussels: Post-Crit. & Theo- k/D = 0.075 ∞ 1.22 Steady Flow. phanatos k/D = 0.085 ∞ 1.26 1990 [21] Mixed Hard Fouling: k/D = 0.076 ∞ 1.11 Kelp: k/D = 1.25 ∞ 1.51 k/D = 2.5 ∞ 1.69 Sea Anemones: k/D = 0.16 ∞ 1.35 Roshko Smooth Cylinder >3.5 106 ∞ 0.65-0.75 Post-Crit. 1961 [22] Steady Flow Wind Tunnel. Miller Smooth Cylinder >3.0 106 ∞ 0.60-0.65 Post-Crit. 1976 [23] Steady Flow Rough Cylinder Wind Tunnel. k/D = 0.0004 >3.0 106 ∞ ≈0.80 Sand k/D = 0.0009 0.8-0.9 Roughened k/D = 0.0014 0.8-0.9 k/D = 0.0021 0.9-1.0 k/D = 0.0031 1.0-1.1 k/D = 0.0050 1.0-1.1 Pearl k/D = 0.015 >0.5 106 ∞ ≈1.1 Post-Crit. Barley k/D = 0.023 ≈1.1 Steady Flow k/D = 0.044 1.1-1.2 Wind Tunnel Dried k/D = 0.042 >0.5 106 ∞ 1.1-1.2 Peas k/D = 0.063 1.2-1.4 Pearcey Smooth Cylinder >3.5 106 ∞ ≈0.6 Post-Crit. et al. Steady Flow 1982 [24] Rough Cylinder Wind Tunnel k/D = 0.0004 >2.0 106 ∞ ≈0.8 k/D = 0.0014 ≈0.88 k/D = 0.0028 ≈0.92 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 40 Mobile Jack-Up Units Rev 3, August 2008 In addition to the literature review presented in Table C4.7.1, an interesting and useful overview of existing literature is presented in a survey report prepared by Advanced Mechanics Engineering Limited for the Health and Safety Executive [25]. The literature review presented in Table C4.7.1 shows that the test results at different facilities agree reasonably well with respect to the drag coefficients for smooth cylinders in post-critical flow. The majority of tests show CD values between 0.6 and 0.7, both for the lower KC range for fatigue (25-60) and the higher KC range for ultimate strength. The suggested CD value for smooth tubular elements (k/D < 0.0001) in post-critical flow is therefore chosen to be CD = 0.65. For rough cylinders the spread between the individual tests with respect to CD values is considerably larger. Especially Sarpkaya [2] operates with very high post-critical CD values for rough cylinders. It should be noted that none of the values obtained by the other authors referenced in Table C4.7.1 support the Sarpkaya values in the postcritical region. The differences between individual tests may partly be due to the different types of post-critical flow (different test conditions) and to the non-uniform definition of roughness used by the different authors. One should also bear in mind that the wave particle velocities decrease with increasing depth below the water surface, which might mean a transition from the post-critical regime to the super-critical or even critical regime. This will result in a reduction in CD values for smooth cylinders (although in the lower Re-number part of the critical regime it may result in an increase in CD values, but here the water particle velocities are so low that the resulting contribution to the overall drag force will be significantly smaller than the contributions higher up on the cylinder). For the rough cylinders the critical regime occurs at lower Re-numbers and there is no reduction in the drag coefficient in the super-critical regime. For large roughnesses an increase in the drag coefficient has in fact been reported in this regime [3, 32]. Based on the literature survey presented in Table C4.7.1 and the discussion above, the drag coefficient for rough cylinders (roughness k/D>0.004) is chosen equal to CD = 1.0, both for the ultimate strength and the fatigue cases. C4.7.2.3 Marine Growth dependence Rust and hard marine growth has been found to behave in essentially the same manner as artificial hard roughness, but a surface with hard marine growth behaves quite differently from a surface with soft marine growth. Another point of consideration is that different types of marine growth on a submerged tubular may dominate at different depths below the sea surface. The use of anti-fouling coating will at least delay the development of marine growth but after a few years the anti-fouling coating becomes less effective. Regularly cleaning of the tubulars is another possible way to limit the development of marine growth. In Table 4.3, Section 4.7.2 of the PRACTICE, it is assumed that severe marine growth is not allowed. This is in accordance with the operational profile of mobile jack-up rigs, with cleaning of legs at intervals preventing severe marine growth. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 41 Mobile Jack-Up Units Rev 3, August 2008 The main contribution to forces is in the surface region, such that the extension of the marine growth below the surface zone is not important for the overall forces. The paint will in addition be somewhat roughened when exposed to the salt water for a longer period. Above the marine growth region the use of values for a smooth cylinder has been recommended. This is mainly based on the fact that the marine growth will be limited to the region below MWL + 2m, limiting the roughness above this region. In addition measurements also indicate that the wave forces in ocean waves are less than predicted by use of a constant CD [39, 31], see also Figure C4.7.1 Based on this it is recommended that the value CD for a smooth surface (CD = 0.65) is generally used for the legs above MWL + 2m and the value for a rough surface below MWL + 2m (CD = 1.0), as stated in Table 4.4 of the PRACTICE. Figure C4.7.1 Comparison between measured and computed forces on a pile up to free surface [39, 31] C4.7.2.4 Definition of relevant parameters The drag coefficient (CD) for tubulars, may be considered as a function of roughness (k/D), Keulegan-Carpenter number (KC) and Reynolds number (Re) as an alternative to Table 4.3. This explicit dependence is intended to be used in cases where there is more detailed knowledge, first of all on the roughness and in addition on the flow conditions around the members at a specific site. A definition of these governing parameters are included in section C4.7.2.1. C4.7.2.5 Dependence on roughness The roughness may be accounted for explicitly if the roughness is documented to be of an intermediate value compared with the smooth and rough k/D values assumed above. Recommended values for the roughness, k, may be found from table C4.7.2. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 42 Mobile Jack-Up Units Rev 3, August 2008 Table C4.7.2 Recommended Roughness Values for Tubulars [45] Surface k (meters) Steel, new uncoated Steel, painted Steel, highly rusted Marine growth 5.0E-5 5.0E-6 3.0E-3 5.0E-3 - 5.0E-2 Several authors have presented, in graphical form, the CD dependence on the relative roughness k/D at post-critical Re-numbers. Figure C4.7.2 presents a graph from Miller [23], showing the variation of CD with varying k/D based on several model experiments at post-critical Re numbers. Figure C4.7.3 and Figure C4.7.4 show similar graphs presented by respectively Wolfram et al [21] and Pearcey et al [28]. Based on the available data with respect to the dependence of CD on k/d, the expressions presented in Equation (4.7.1) have been proposed to describe this dependence for the purpose of the PRACTICE. The drag coefficient CDi may then be obtained from Equation (4.7.1): CDi(k/D) = C kD C kD k D C kD Dsmooth Dsmooth Drough = < + < < = < ⎧ ⎨ ⎪ ⎩ ⎪ 0 65 0 0001 2 36 0 34 0 0001 0 004 10 0 004 . ; / . ( . . ( / )) ; . / . . ; . / Log10 (4.7.1) A graphic representation of Equation (4.7.1) is shown in Figure C4.7.5. With respect to the inertia coefficients for smooth cylinders, all the references from Table C4.7.1 report post-critical CM values lower than the asymptote CM = 2.0. The CM values lie mainly in the range 1.6 - 1.7. However the question is whether (in general) some inertia contribution has been included in the drag forces used for the CD determination. This would mean that the CD values are slightly overestimated and the CM values slightly underestimated. At the same time, since both fatigue and ultimate strength imply Keulegan-Carpenter numbers >25, it is the drag dominated region which is of most interest and the chosen CM values are not really critical. Based on this argument the inertia coefficient for smooth cylinders in the post-critical regime is set equal to the asymptotic value CM = 2.0. The CM values for rough cylinders, are in general reported to be slightly lower than the CM values for smooth cylinders. Based on the same argument as used for the smooth cylinders, the inertia coefficient for rough cylinders in the post-critical regime is set equal to CM = 1.8. A summary of the recommended values for the hydrodynamic coefficients for tubulars is given in Table C4.7.3. Table C4.7.3 : Recommended Hydrodynamic Coefficients for Tubulars Tubular CDi CMi Smooth (k/D<0.0001) 0.65 2.0 Rough (k/D>0.004) 1.0 1.8 Intermediate k/D Equation 4.7.1 2.0 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 43 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.2 Drag coefficient for rough cylinders at high Reynold's number, [23] Figure C4.7.3 Drag coefficient for post critical Reynolds numbers for rough cylinders, [21] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 44 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.4 Effect of roughness on drag coefficient and vortex shedding frequency for post-critical Reynolds numbers, [28] Figure C4.7.5 Recommended values for the drag coefficient as function of relative roughness COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 45 Mobile Jack-Up Units Rev 3, August 2008 Keulegan-Carpenter number dependence. In post-critical conditions, for KC-numbers lower than say 30-40, there seems to be some dependence of the drag coefficient on the KC-number, at least for rough cylinders. For smooth cylinders this KC-dependence is more uncertain. The Christchurch Bay Tower (CBT) results for a clean cylinder reported by Bishop [26], for example, show this dependence for smooth cylinders, and so do the results reported from the Ocean Test Structure (OTS) [19]. Wolfram and Theophanatos [21], and the SSPA results reported by Rodenbusch and Gutierrez [15], do not show this dependence for smooth cylinders. For rough cylinders in post-critical conditions, the KC-dependence of the drag coefficient for KC-numbers lower than say 30-40, seems to be a more generally observed trend, as in [15, 19, 27] amongst others. It must be emphasized that for decreasing KC-numbers (<30) the (post-critical) conditions will gradually be more inertia dominated and less drag dominated, implying an increasing uncertainty in the reported CD- values. Figure C4.7.6 shows CD as a function of the KC-number for cylinders in waves from [52]. Figures C4.7.7 and C4.7.8 show in a similar way CD as a function of KC-number for respectively a clean cylinder and a rough barnacle covered cylinder of the Ocean Test Structure (OTS [19]) as presented in [25]. Based on the discussion above and the results reported in the literature the explicit KCdependence presented in Equation (4.7.2) may be included in the computations in addition to the roughness dependence: CDi(KC,k/D) = CDi(k/D) 145 10 2 5 10 37 10 37 0 2 . ; / ( ) ; . ; . KC KC KC KC < − < < < ⎧⎨ ⎪ ⎩⎪ (4.7.2) A graphic representation of Equation (4.7.2) is given in Figure C4.7.9. Equation (4.7.2) should also be used for smooth cylinders, in spite of the uncertainty with respect to the KC-dependence. However, for low KC- values the choice of CDvalue is less critical due to the transition to inertia dominated conditions. Furthermore using Equation (4.7.2) for the entire roughness range (from smooth to rough) results in a more uniform and easier to use way to handle the KC-dependence. An inertia coefficient CM = 2.0 for smooth cylinders and CM = 1.8 for rough cylinders is suggested for use if KC-dependence is used for the drag coefficients at low KCnumbers. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 46 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.6 Drag coefficient dependence on KC number, [52] Figure C4.7.7 Drag coefficient dependence on KC-number for clean cylinders of the Ocean Test Structures, [19, 25] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 47 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.8 Drag coefficient dependence on KC-number for barnacle covered cylinders of the Ocean Test Structure, [19, 25] Figure C4.7.9 Recommended drag coefficient dependence on KC for cylinders in waves, at high Reynolds numbers COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 48 Mobile Jack-Up Units Rev 3, August 2008 Reynold's number dependence As previously discussed the drag coefficient is dependent on the Re-number and this has been reported by several authors [3, 32] (Figures C4.7.11 and C4.7.12) and is reflected in some guidance on load computations, e.g. [29, 33] (Figure C4.7.10). However, the use of test results reducing CD in the critical region is not relevant for practical purposes as the roughness k/D<1/100000 implied in the curve for smooth cylinders is not applicable for jack-up structures. The change in the Reynolds dependence with respect to roughness is quite large and it is therefore not possible to recommend one single curve for this dependence. The recommended set of curves shown in Figure C4.7.13 are mainly based on a functional fit to the test results presented in [32] and in addition the drag coefficient in the critical regime is set to minimum of CD = 0.45. Test results have indicated lower CD values, but only in the ideal conditions of test facilities. A recommended set of curves are given in Figure C4.7.13, complying with the roughness dependence of Figure C4.7.5 at large Reynolds numbers. Using the curve for roughness k/D = 0.01 there is no reduction below CD = 1.0 for Reynolds numbers above 105, which supports the use of a constant CD in the PRACTICE. Figure C4.7.10 Suggested Reynolds dependence in existing guidance, [33] Figure C4.7.11 Reynolds dependence of drag coefficient in test results, [3] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 49 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.12 Reynolds dependence of drag coefficient, [32] Figure C4.7.13 Recommended values for Reynolds dependence for different values of relative roughness, KC>40 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 50 Mobile Jack-Up Units Rev 3, August 2008 C4.7.3 Marine Growth Thickness In addition to the effect on the roughness the effective diameter should be increased to account for marine growth. Here it is recommended to increase the radius by 12.5 mm (i.e. diameter increased by 25mm) over the full water depth for tubulars. C4.7.4 Hydrodynamic Coefficients for Brackets These are treated as flat plates implying that a CDi = 2.0 and CMi = 1.0 is to be applied (considering the area associated with CM as that of the circumscribed circle). For convenience the PRACTICE proposes that brackets are included as horizontal members in the hydrodynamic model to assure proper directional dependence of forces. Shielding may be considered according to Figure 4.3 of the PRACTICE. C4.7.5 Hydrodynamic Coefficients for Chords C4.7.5.1 Split tube chords In considering the test results for split tube chord data the following aspects are considered: - The tests are almost always performed with a smooth cylinder section. - Most of the tests are performed in stable current or wind conditions. The first aspect is the most important, also indicated by the test results evaluation of the tubulars presented in Section C4.7.2. The drag coefficient for smooth tubulars is about CDsmooth = 0.65, while for rough cylinder this increases to CDrough = 1.0. The second aspect on stable flow conditions should not affect the results very much as the KC values are very high in extreme load evaluations. However, the test result in [63] showed higher values in waves than in stable current. This has not yet been fully explained, but comparisons made in [25] indicates that test results in waves from flume experiments overpredict the drag forces. A number of test results [62] have been considered, from wind tunnel tests and towing in water, when evaluating hydrodynamic coefficients for split tube chords. The drag coefficient is first estimated for the directions 0° and 90° as defined in Figure C4.7.14. The drag coefficients for 0° are dominated by the tubular part and no particular effect of the rack on the drag coefficient is seen from the tests. That is, for typical dimensions of the tubular diameter and rackplate thickness t, Di/t >> 1.0, tests show values of about CD ≈ 0.65. This indicates that the drag coefficients chosen for the tubular are also valid for the split tube chord for the 0° direction. In order to be consistent with the roughness dependence of the drag coefficient for tubulars, the drag coefficient in the marine growth region is increased due to roughness to CDrough = 1.0 for θ = 0°. For the 90° direction the drag coefficient should be similar to that of a flat plate for large W/Di ratios, CDplate = 2.0. However, test results seem to indicate that the CD values for this direction referring to the mean rack width W, are, on average, about 1.8, see Figure C4.7.15. The suggested drag coefficient in the PRACTICE is therefore set to be 1.8 for small W/Di ratios, increasing to 2.0 for large W/Di ratios. The interpolation between these two numbers is based on engineering judgment. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 51 Mobile Jack-Up Units Rev 3, August 2008 The drag coefficient for the wave flow normal to the rack, related to the rack width W, is recommended as: CD1 = 18 12 14 3 12 18 20 18 20 . / . . / . / . . . / . W D W D W D W D i i i i < + < < < < ⎧⎨ ⎪ ⎩⎪ (4.7.3) For the interpolation between the directions 0° and 90° a number of formulations are available, but since there were a number of test results available, a best fit of a new formulation was decided. The following interpolation formula were found to fit the data best, see Appendix C4.C, and at the same time be flexible with respect to the drag coefficient for rough and smooth surfaces at 0°: CDi = C C CWD C D D D i D 0 0 1 0 2 20 20 9 7 20 90 θ θ θ < ° + − − ° ° < < ° ⎧⎨⎩ ( / )sin[( )/] (4.7.4) where; CD0 = is the drag coefficient for the chord at θ = 0° and is to be taken as that of a tubular with appropriate roughness, see Section C4.7.2 i.e. CD0 = 0.65 above MWL + 2.0m and CD0 = 1.0, below MWL+2.0m. Possible dependence on KC and Re numbers as for a tubular. CD1 = The drag coefficient for flow normal to the rack (θ = 90°), related to the projected diameter (the rack width W). Explicit dependence on KC may be taken according to Figure C4.7.9, but is normally not relevant for extreme loading conditions. Dependence on k/D or Re may normally be neglected. The above formulation was derived based on the assumption that the chord behaves like a tubular up to a direction where the rack enters the flow field, and from there and up to 90° the chord acts as a flat plate. In addition to the above formulation two other formulations were tested as shown in Figure C4.7.16. Equation 4.7.4 gave an excellent fit with the observed drag coefficients for a smooth tubular and is therefore recommended to be used for split tube chords. Interpolation formula similar to those used in [29] and [46] are compared in Figure C4.7.17 with Equation 4.7.4, for a regular wave analysis. There is some difference in the direction close to 90°, but the number of test results behind the PRACTICE formulation is believed to justify the change. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 52 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.14 Definition of directions and dimensions for a split tube chord Figure C4.7.15 Drag coefficient at 90° related to the rack width W COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 53 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.16 Alternative interpolation formulations fit to data Figure C4.7.17 Comparison with some current practices for regular wave analysis [29], [46]. W/D = 1.24 and the scaling regular/irregular = 0.7, valid below MWL + 2.0m COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 54 Mobile Jack-Up Units Rev 3, August 2008 For the inertia coefficient the theory [32] indicates CM = 2.0 for a smooth tubular related to the projected diameter and CM = 1.0 for an isolated flat plate. However, when the plate is considered in conjunction with the split tube sections CM = 2.0 is appropriate for the combined section. For a rough tubular as indicated in Table 4.4 of the PRACTICE, the inertia coefficient should be about 1.8 in the marine growth region. However, since the inertia forces will not contribute much to the extreme forces on the legs, the inertia coefficient was set to 2.0 related to the width of the chord measured over the tubular, i.e. at 0°. This is a simple solution and will be conservative in the direction of the tubular for a rough surface and unconservative in the direction of the rack and on average correct. This formulation will also be consistent with the simplified modeling of the leg section where the reference diameter Di is the dimension D and using CMe = 2.0. For large rack to diameter ratios W/D, it may however be considered appropriate to modify (reduce) the inertia coefficient such that it accounts more correctly for the combination of the contributions from the flat plate and tubular components. C4.7.5.2 Triangular chords For triangular chords (Figure C7.4.18) little test data are available. Some currently applied formulae for drag coefficients of more basic sections were therefore used in addition to the test results to improve the background for the actual chosen values. Drag coefficients related to two typical shapes are given in [45], as shown in Figure C4.7.19, for a triangular box section and two plates mounted normally on each other. A triangular chord is a combination of these cross sections. The numbers at different directions are compared in Table C4.7.4. The drag coefficients were determined by vectorial summation of drag forces in direction 1 and 2 according to Figure C4.7.19. To relate the drag coefficient to a fixed dimension Di = D the back plate width is chosen. A fixed dimension and directional dependent drag coefficient is convenient for modeling purposes. The drag coefficient related to this fixed diameter may be computed as: CDi = CDpr(θ) Dpr(θ) / Di where; CDpr(θ) = the drag coefficient referenced to the projected diameter. = 170 0 195 90 140 105 165 180 2 00 180 . ; . ; . ; . ; . ; θθθ θ θ θ = ° = ° = ° = °− = ° ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ o Dpr(θ) = the projected diameter of the chord determined as: Dpr(θ) = D W D D o o o o cos( ) ; sin( ) / cos( ) ; cos( ) ; θ θ θ θ θ θ θ θ θ θ θ 0 2 180 180 180 < < + < < − − < < ⎧ ⎨ ⎪ ⎩ ⎪ (7.9) θo = the angle where half the backplate is hidden behind the rackplate, determined as θo = tan-1(D/2W). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 55 Mobile Jack-Up Units Rev 3, August 2008 Table C4.7.4 Comparison of drag coefficients for simple sections and chord CDpr evaluated from tests. θ ⊥ /45/ Δ /45/ PRACTICE CDpr: 0 1.7 1.3 1.70 45 2.5 1.8 1.825 90 2.2 1.95 135 1.5 1.3 1.50 180 2.0 1.8 2.00 (W/D = 1.1) As a basis for the suggested drag coefficients the results available from TEES [67] and DHL [61,62] were considered together with the recommendations in [46]. The drag coefficients recommended in the PRACTICE are compared with the TEES test results in Figure C4.7.20. The inertia coefficient CMi = 2.0 may be applied for all directions, related to the equivalent volume of πDi 2/4 per unit length, where Di = D, the backplate dimension. This assumes that the outline cross sectional area is approximately πDi 2/4. If the rack width is not of similar size to the backplate dimension, a more detailed consideration of the inertia coefficient should be made if the loadings on the leg are not drag dominated i.e. if the results are sensitive to the choice of inertia coefficient. Explicit dependence on KC may be taken according to Figure C4.7.9, but is normally not relevant for extreme loading conditions. Dependence on k/D or Re may normally be neglected. Figure C4.7.18 Definition of dimensions and angles for a triangular chord C4.7.6 Other shapes For other shapes, or groups of elements, see e.g. [45]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 56 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.7.19 Drag coefficients for basic sections in uniform flow [45] Figure C4.7.20.a : Marathon LeTourneau 116C Figure C4.7.20.b : Marathon LeTourneau Gorilla Figure C4.7.20 Comparison between TEES test results and the PRACTICE COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 57 Mobile Jack-Up Units Rev 3, August 2008 C4.8 OTHER CONSIDERATIONS For the most critical individual leg members the possibility of local vortex induced vibrations should be evaluated. This check will normally be covered at the design stage. However, if the site conditions of wind or current and/or wave height exceed those used for design such a check may be required. This is because vortex induced vibrations may lead to very high local stresses and a major contribution to fatigue loading. Vortex induced resonance will not normally be occur if: S < 0.2 for tubulars < 0.145 for flat plates where; S = [(fi Di)/vn], the Strouhal number vn = flow velocity normal to the member Di = diameter of member fi = fundamental vibration frequencies of member (in Hz). Further information and bounds for S above which vortex shedding will not occur may be found in [45] and [59]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 58 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C4 A = cross sectional area of member. Ae = equivalent area of leg per unit height = (Σ Ai li )/s. Ai = equivalent area of element = π Di 2 / 4. As = sum of projected areas for all members in the considered plane. At = total projected envelope area of the considered plane. CD = drag coefficient. CDo = The drag coefficient for chord at direction θ = 0°. CD1 = The drag coefficient for flow normal to the rack, θ = 90°. CDe = equivalent drag coefficient. CDei = equivalent drag coefficient of member i = CDi (Di/De) (vertical member) = sin3αi CDi (Dili/Des). CDi = drag coefficient of an individual member, related to Di. CDpr(θ) = drag coefficient to the projected diameter. CDrough = drag coefficient for a rough member. CDsmooth = drag coefficient for a smooth member. Ch = height coefficient for wind. CM = inertia coefficient. CMe = equivalent inertia coefficient. CMei = equivalent inertia coefficient of member i = 1.0, horizontal member with flow along the length axis = 1.8, vertical rough tubular with flow normal to the length axis = 2.0, other vertical members with flow normal to the length axis = 1.0, flat plates (brackets). CMi = inertia coefficient of a member, related to Di. d = the mean, undisturbed water depth (positive). D = member diameter. De = equivalent diameter of leg bay. Di = reference dimension of individual leg members. Dl = face width of leg, outside dimensions. Dpr(θ) = projected diameter of the chord. fi = fundamental vibration frequencies of the member. Hs = significant wave height. k = roughness height. k/D = relative roughness. KC = Keulegan-Carpenter number. li = length of member 'i' node to node. N = constant in wind velocity power law. 􀀅rn = velocity of the considered member, normal to the member axis and in the direction of the combined particle velocity. Re = Reynolds number. s = length of one bay, or part of bay considered. S = Strouhal's number. S = average wave steepness. S = outer diameter of an array of tubulars. T = wave period. Tn = first natural period of sway motion. Tz = zero-upcrossing period. u = particle velocity. un = liquid particle velocity normal to the member. 􀀅un = liquid particle acceleration normal to the member. ux, 􀀅ux = horizontal water particle velocity and acceleration. U = flow velocity at the depth of the considered element. UC = particle velocity by current. Um = maximum orbital particle velocity. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 59 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C4 (Continued) Ured = reduced particle velocity for regular waves, Ured = uTn/D. UW = particle velocity by waves. vn = total flow velocity normal to the member. VC = the reduced current velocity to be used in analysis. VC = the current velocity to be used in the hydrodynamic model, VC should not be taken less than 0.7Vf. VCn = current velocity normal to member used in the hydrodynamic model. Vf = far field (undisturbed) current. W = dimension from backplate to pitch point of triangular chord or dimension from root of one rack to tip of other rack of split -tubular chord. W = the width of the structure. xo = motion amplitude used in consideration of the applicability of the relative velocity formulation. z = coordinate measured vertically upward from the mean water surface. z' = modified coordinate to be used in particle velocity formulation. Z = elevation measured from the mean water surface. α = indicator for relative velocity, 0 or 1. αi = angle defining flow direction relative to member. β = Re/KC parameter to describe the test environment. βi = angle defining the member inclination. ΔFdrag = drag force per unit length. ΔFinertia = inertia force per unit length. ΔFinertiaH = horizontal inertia force per unit length. λ = wave length. ν = kinematic viscosity. θ = angle in degrees for waves relative to the chord orientation. θo = angle where half the backplate is hidden behind the rackplate. ρ = mass density of water or air. ζ = the instantaneous water surface elevation (same axis system as z) ζo = the wave crest (same axis system as z). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 60 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C4 1 Keulegan, G.H., Carpenter, L.H., 'Forces on Cylinders and Plates in an Oscillating Fluid', Journal of Research of the National Bureau of Standards, Volume 60, No. 5, May 1958. 2 Sarpkaya, T., 'In-Line and Transverse Forces on Smooth and Sand-Roughened Cylinders in Oscillatory Flow at High Reynolds Numbers', Naval Postgraduate School, Report NPS-69 SL 76062, 1976. 3 Hogben, N., Miller, B.L., Searle, J.W., Ward, G., 'Estimation of Fluid Loading on Offshore Structures', Proc. Institution Civil Engineers, Part 2, 1977. 4 Sarpkaya, T., 'Wave Forces on Inclined Smooth and Rough Circular Cylinders', Offshore Technology Conference, Paper OTC 4227, 1982. 5 Sarpkaya, T., Bakmis, C., Storm, M.A., 'Hydrodynamic Forces from Combined Wave and Current Flow on Smooth and Rough Circular Cylinders at High Reynolds Numbers', Offshore Technology Conference, Paper OTC 4830, 1984. 6 Sarpkaya, T., Storm, M.A., 'In-Line Force on a Cylinder Translating in Oscillatory Flow', Applied Ocean Research, Volume 7, No. 4, 1985. 7 Sarpkaya, T., 'Force on a Circular Cylinder in Viscous Oscillatory Flow at Low Keulegan- Carpenter Numbers', Journal of Fluid Mechanics, Volume 165, 1986. 8 Sarpkaya, T., 'Past Progress and Outstanding Problems in Time-Dependent Flows about Ocean Structures', Proc. of Separated Flow around Marine Structures, The Norwegian Institute of Technology, Trondheim, Norway, 1985. 9 Sarpkaya, T., 'On Fluid Loading of Offshore Structures - After Ten Years of Basic and Applied Research', Offshore Operations Symposium, 9th ETCE, New Orleans, 1986. 10 Nath, J.H., 'Heavily Roughened Horizontal Cylinders in Waves', Proceedings of BOSS, 1982. 11 Bearman, P.W., Chaplin, J.R., Graham, J.M.R., Kostense, J.K., Hall, P.F., Klopman, G., 'The Loading on a Cylinder in Post-Critical Flow Beneath Periodic and Random Waves', Proceedings of BOSS, 1985. 12 Kasahara, Y., Koterayama, W., Shimazaki, K., 'Wave Forces Acting on Rough Circular Cylinders at High Reynolds Numbers', Offshore Technology Conf., Paper OTC 5372, 1987. 13 Chaplin, J.R., 'Loading on a Cylinder in Uniform Oscillatory Flow: Part I - Planar Oscillatory Flow', Applied Ocean Research, Vol.10, No. 3, 1988. 14 Davies, M.J.S., Graham, J.M.R., Bearman, P.W., 'In-Line Forces on Fixed Cylinders in Regular and Random Waves', Society for Underwater Technology, Volume 26: Environmental Forces on Offshore Structures and Their Prediction, 1990. 15 Rodenbusch, G., Gutierrez, C.A., 'Forces on Cylinders in Two-Dimensional Flows', Report BRC13-83, Shell Development Co., 1983. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 61 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C4 (Continued) 16 Rodenbusch, G., Källström, C., 'Forces on a Large Cylinder in Random Two-Dimensional Flows', Offshore Technology Conference, Paper OTC 5096, 1986. 17 Theophanatos, A., Wolfram, J., 'Hydrodynamic Loadings on Macro-Roughened Cylinders of Various Aspect Ratios', Journal of Offshore Mechanics and Arctic Engineering, Volume 111, No. 3, 1989. 18 Klopman, G., Kostense, J.K., 'The Loading on a Vertical Cylinder in Random Waves at High Reynolds Numbers', Water Wave Kinematics, pp. 679-699, 1990. 19 Heideman, J.C., Olsen, O.A., Johansson, P.I., 'Local Wave Force Coefficients', Civil Engineering in the Oceans IV, ASCE, 1979. 20 Nath, J., 'Biofouling and Morison Equation Coefficients', Proceedings 7th. International Conf. on Offshore Mechanics and Arctic Engineering, 1988. 21 Wolfram, J., Theophanatos, A., 'Marine Roughness and Fluid Loading', Society for Underwater Technology, Volume 26: Environmental Forces on Offshore Structures and Their Prediction, 1990. 22 Roshko, A., 'Experiments on the Flow Past a Circular Cylinder at Very High Reynolds Number', Journal of Fluid Mechanics, Volume 10, Part 3, 1961. 23 Miller, B.L., 'The Hydrodynamic Drag of Roughened Circular Cylinders', Transactions RINA, 1976. 24 Pearcey, H.H., Cash, R.F., Salter, I.J., 'Flow Past Circular Cylinders: Simulation of Full- Scale Flows at Model Scale', NMI Report R131, 1982. 25 'Roughness and Vortex Shedding Effects for Cylinders in Flume and Real Sea Waves', Report for the Health and Safety Executive by Advanced Mechanics Engineering Limited, 1991. 26 Bishop, J.R., 'An Analysis of Peak Values of Wave Forces and Particle Kinematics from the Second Christchurch Bay Tower', NMI Report R180, 1985. 27 Bishop, J.R., 'Wave Force Experiments at the Christchurch Bay Tower with Simulated Hard Marine Fouling', Report No. OTI 89 541, HMSO, 1989. 28 Pearcey, H.H., Matten, R.B. and Singh, S., 'Fluid Forces for Cylinders in Oscillatory Flow Waves and Currents when Drag and Inertia Effects Are Present Together', BMT Report to the Health and Safety Executive OT-0-86-011, 1986. 29 Det Norske Veritas Rules for the Classification of Fixed Offshore Installations. 30 J.R. Morison, M.P O'Brien, J.W. Johnson, S.A. Schaaf, 'The Forces Exerted by Surface Waves on Piles', J. of Petr. Techn., American Inst. of Mining Engrs., Vol. 189, 1950, p149- 154. 31 S.K. Chakrabarti, 'Hydrodynamics of Offshore Structures', Springer Verlag, Berlin, Hedelberg, 1987. 32 O.M. Faltinsen, 'Sea Loads on Ships and Offshore Structures', Cambridge University Press, Trumpington Street, Cambridge, 1990. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 62 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C4 (Continued) 33 BSI Code of Practice No. 3, Chapter 5, Part 2, 'Wind Loads', September 1972 34 J.H. Vugts, 'A Review of Hydrodynamic Loads on Offshore Structures and Their Formulation', BOSS'79, Imperial College, London, England, August 1979 35 E.J. Laya, J.J. Connor and S.Shyam Sunder, 'Hydrodynamic Forces on Flexible Offshore Structures', Journal of Engineering Mechanics, Vol. 110, No.3, 1984. 36 S.R. Winterstein, E.M. Bitner-Gregersen and K. Ronold, 'Statistical and Physical Models of Nonlinear Random Waves', OMAE, Volume II, Safety and Reliability, Stavanger, 1991, pp.23-31. 37 J.D. Wheeler, 'Method for Calculating Forces Produced by Irregular Waves', OTC, paper no. 1006, Dallas, Texas, 1969. 38 J.E. Skjelbreia, G. Berek, Z.K. Bolen, O.T. Gudmestad, J.C. Heideman, R.D. Ohmart, N. Spidsoe and A. Torum, 'Wave Kinematics in Irregular Waves', OMAE, Stavanger, 1991. 39 R.G. Bea and N.W. Lai, 'Hydrodynamic Loadings on Offshore Platforms', OTC paper no 3064, May, 1978, pp. 155-168. 40 R.G. Dean and P.M. Aagaard, 'Wave Forces: Data Analysis and Engineering Calculations', Journal of Petroleum Technology, March 1970, 105-119. 41 J.R. Chaplin and T.P Flintham, 'Breaking Wave Forces on Tubulars', 3rd International Jack-up Conference, City University, London, September 1991. 42 L. Skjelbreia and J.A. Hendricksen, 'Fifth-order Gravity Wave Theory', Proceedings of Seventh Conference on Coastal Engineering, 1961, pp. 184-196. 43 O.J. Andersen, E. Førland and S. Haver, Design Basis, Environmental Conditions, Statfjord, Statoil Report no. F&U-ST 88007, Stavanger, April 25 1988. 44 R.C.T. Rainey, 'Christchruch Bay Tower Compliant Cylinder Project, Final Summary Report and Conclusions', OTH-90-139, WS Atkins Engineering Sciences, Surrey, January, 1991. 45 DNV Classification note 30.5, 'Environmental Conditions and Environmental Loads', July 1990. 46 'Practice for the Site Specific Assessment of Jack-up Units', By Marine Technology Division, SIPM, EDP-5, The Hague, May 1989, 47 WAJAC, Veritas Sesam Systems Report no. 82-6108, Høvik, Dec. 1984. 48 N. Pharr Smith, D.B. Lorenz, C.A. Wendenburg and J.S. Laird, 'A Study of Drag Coefficients for Truss Legs on Self-Elevating Mobile Offshore Drilling Units', SNAME Tansactions, Vol. 91, 1983, pp. 257-273. 49 N. Pharr Smith and C.A. Wendenburg, 'A study of Drag Coefficients', The Jack-Up Drilling Platform, Ed. L. Boswell, City University, London, 1989. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 63 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C4 (Continued) 50 Yoshiharu, Ideguchi, 'Legs Drag Coefficients of Enhanced 300IC Jack-Up Rig', TSU Research Laboratories Technical Research Center, Nippon Kokan K.K. Report No. 822117, June 1982 51 Borgman, L.E., 'Random Hydrodynamic Forces on Objects', Annals of Mathematical Statistics, Vol. 38., 1967, pp. 37-51. 52 Atkins Engineering Services, 'Fluid Loading on Fixed Offshore Structures', OTH 90 322, 1990. 53 Taylor, P., 'Current Blockage - Reduced Forces on Steel Platforms in Regular and Irregular Waves with a Mean Current', Offshore Technology Conference, OTC 6519, Houston, 1991. 54 Heideman J.C. and Schaudt K.J., 'Recommended Equations for Short-term Statistics of Wave Heights and Crest Heights', 1 April 1987 55 Moe, G. and Verley, R.L.P, 'Hydrodynamic Damping of Offshore Structures in Waves and Currents', The Offshore Technology Conference, OTC 3798, Houston, 1980. 56 American Petroleum Institute, proposal for an update of the API-RP2A, 'Hydrodynamic Force Guidelines for U.S. Waters', received 6. February 1992. 57 The Norwegian Petroleum Directorate, 'Regulation for structural design of loadbearing structures intended for exploitation of petroleum resources', 1988. 58 Health and Safety Executive, 'Offshore Installations: Guidance on design, construction and certification', London, 1990. 59 N.D.P. Barltrop, A.J. Adams, 'Dynamics of Fixed Marine Structures', Third Edition, Butterworth Heinemann, 1991. 60 MacCamy R.S., Fuchs R.A., 'Wave Forces on Piles: A Diffraction Theory", U.S. Army Corps of Engineers, Beach Erosion Board, Tech. Memo No 69, Washington DC, 1954. Other project reports related and technical notes: 61 G.H.G. Lagers, 'Morison Coefficients of Jack-Up Legs', MSC report 1005, Schiedam, The Netherlands, February 1990. 62 G.H.G. Lagers, 'Collected Morison Coefficients of Jack-Up Leg Elements', MSC report 1715, Schiedam, The Netherlands, June 1991. 63 S.Th. Schurmans et. al., DHL, 'Wave Forces on Jack-Up Legs', Delft Hydraulics measurement report 8603-1505, Delft, 1990. 64 A. Løken, 'Review of DHL test data', Veritec report no. 91-3372, Høvik, 1991. 65 Løseth R.M., Arnesen Y., 'Check of data reduction of DHL data', DNVC report No 92- 1054, Høvik, August 1992. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 64 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C4 (Continued) Other project reports related and technical notes (continued): 66 D. Karunakaren, 'Scaling of Hydrodynamic Loads According to Computational Models', Technical memo no. 710762, SINTEF, Trondheim, July, 1991. 67 N.P. Smith, TEES Test Data, Extract, December 6, 1991. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 65 Mobile Jack-Up Units Rev 3, August 2008 APPENDIX C4.A : EXAMPLE OF EQUIVALENT MODEL COMPUTATIONS Figure C4.A.1 Model of a bay for test purposes Table C4.A.1 Computations of equivalent model for heading 0° to be used in site assessment for z < MWL + 2m, chord W/D = 1.13. i αi βi cos…*) CDi Di li CDi*Di*li*cos… 1 (30) 90. 1.0 1.0 .65 5.0 3.25 Chords: 2 (30) 90. 1.0 1.0 .65 5.0 3.25 3 (90) 90. 1.0 2.124 .65 5.0 6.90 4 -30 26.7 0.25 1.0 .30 11.2 0.84 5 -30 -26.7 0.25 1.0 .30 11.2 0.84 Inclined 6 30 26.7 0.25 1.0 .30 11.2 0.84 braces 7 30 -26.7 0.25 1.0 .30 11.2 0.84 8 90 26.7 1.0 1.0 .30 11.2 3.36 9 90 -26.7 1.0 1.0 .30 11.2 3.36 span 10 -30 0. 0.125 1.0 .10 5.0 0.06 breakers 11 30 0. 0.125 1.0 .10 5.0 0.06 12 90 0. 1.0 1.0 .10 5.0 0.50 ΣCDi*Di*li*cos… = 24.10 s 5.0 m CC equivalent model De Me = = Σ = = Σ = = = = ⎫ ⎬ ⎪ ⎭ ⎪ C D C Dl s D Dl s De e Di i i e i i / . ( /) . . / . .. 482 158 482 158 305 20 2 ) Geometric factor, see Section 4.6.6 [sin2βi + cos2βi sin2αi]3/2 the PRACTICE COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 66 Mobile Jack-Up Units Rev 3, August 2008 Table C4.A.2 Computations of equivalent model for heading 0° to be compared with model test results, chord W/D = 1.13, model scale = 1:4.264 i αi βi cos…*) CDi Di li CDi*Di*li*cos… 1 (30) 90 1.0 0.65 .152 1.178 0.1164 Chords: 2 (30) 90 1.0 0.65 .152 1.178 0.1164 3 (90) 90 1.0 2.124 .152 1.178 0.3803 4 -30 26.7 0.25 0.65 .07 2.628 0.02899 5 -30 -26.7 0.25 0.65 .07 2.628 0.02899 Inclined 6 30 26.7 0.25 0.65 .07 2.628 0.02899 braces 7 30 -26.7 0.25 0.65 .07 2.628 0.02899 8 90 26.7 1.0 0.65 .07 2.628 0.11957 9 90 -26.7 1.0 0.65 .07 2.628 0.11957 span 10 -30 0. 0.125 0.65 .025 1.173 0.00238 breakers 11 30 0. 0.125 0.65 .025 1.173 0.00238 12 90 0. 1.0 0.65 .025 1.173 0.01906 ΣCDi*Di*li*cos… = 0.992 s C D D D s C De e e i i De == = Σ = = = = ⎫ ⎬ ⎪ ⎭ ⎪ 1178 0 842 1 0 370 0 842 0 370 2 277 20 2 . . / . . / . .. C equiv. model Me (model scale) C D D C De e e De . . .. = === ⎫⎬ ⎪ ⎭⎪ 359 158 2 277 C 2 0 equiv. model Me (full scale) Table C4.A.3 Computations of equivalent model for heading 30° to be compared with model test results, chord W/D = 1.13, model scale = 1:4.264 i αi βi cos…*) CDi Di li CDi*Di*li*cos… 1 (60) 90 1.0 1.663 .152 1.178 0.2978 Chords: 2 (60) 90 1.0 1.663 .152 1.178 0.2978 3 (30) 90 1.0 0.65 .152 1.178 0.1164 4 0 26.7 0.091 0.65 .07 2.628 0.01088 5 0 -26.7 0.091 0.65 .07 2.628 0.01088 Inclined 6 60 26.7 0.716 0.65 .07 2.628 0.08561 braces 7 60 -26.7 0.716 0.65 .07 2.628 0.08561 8 30 26.7 0.254 0.65 .07 2.628 0.03037 9 30 -26.7 0.254 0.65 .07 2.628 0.03037 span 10 60 0. 0.650 0.65 .025 1.173 0.01239 breakers 11 60 0. 0.650 0.65 .025 1.173 0.01239 12 30 0. 0.125 0.65 .025 1.173 0.00238 ΣCDi*Di*li*cos… = 0.9929 s C D D D s C De e e i i De == = Σ = = = = ⎫ ⎬ ⎪ ⎭ ⎪ 1178 0 843 1 0 370 0 843 0 370 2 278 20 2 . . / . . / . .. C equiv. model Me (model scale) C D D C De e e De . . .. = === ⎫⎬ ⎪ ⎭⎪ 359 158 2 278 C 2 0 equiv. model Me (full scale) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 67 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.A.2 Square bay with triangular chords Table C4.A.4 Square bay with triangular chords, Equivalent model to be used in site assessment z < MWL + 2m. i αi βi cos…*) CDi Di li CDi*Di*li*cos… 1 45 90 1.0 1.65 .71 3.4 3.983 Chords: 2 45 90 1.0 1.65 .71 3.4 3.983 3 135 90 1.0 1.79 .71 3.4 4.321 4 135 90 1.0 1.79 .71 3.4 4.321 5 0 40.2 0.2689 1.0 .32 10.6 0.912 Inclined 6 90 40.2 1.0 1.0 .32 10.6 3.392 braces 7 90 40.2 1.0 1.0 .32 10.6 3.392 8 0 40.2 0.2689 1.0 .32 10.6 0.912 Side 9 0 0. 0.091 1.0 .32 11.2 0.0 Horiz 10 90 0. 1.0 1.0 .32 11.2 3.584 11 90 0. 1.0 1.0 .32 11.2 3.584 12 0 0. 0.091 1.0 .32 11.2 0.0 span 13 45 0. 0.354 1.0 .23 11.4 2.622 breakers 14 45 0. 0.354 1.0 .23 11.4 2.622 brackets 15 90. 0. 1.0 2.0 .98 0.98 1.921 ΣCDi*Di*li*cos… = 39.550 s C D D Dl s CC De e e i i De Me == = = = = = ⎫ ⎬ ⎪ ⎭ ⎪ Σ 34 1163 230 1163 2 30 5 06 20 2 . . ( /) . . / . .. equivalent model COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 68 Mobile Jack-Up Units Rev 3, August 2008 Table C4.A.5 Square bay with triangular chords, Equivalent model to be used in comparison with test results, model scale 1:4.256. i αi βi cos…) CDi Di li CDi*Di*li*cos… 1 45 90 1.0 1.65 .167 0.8008 0.2207 Chords: 2 45 90 1.0 1.65 .167 0.8008 0.2207 3 135 90 1.0 1.79 .167 0.8008 0.2989 4 135 90 1.0 1.79 .167 0.8008 0.2989 5 0 40.2 0.2689 0.65 .076 2.481 0.0330 Inclined 6 90 40.2 1.0 0.65 .076 2.481 0.1226 braces 7 90 40.2 1.0 0.65 .076 2.481 0.1226 8 0 40.2 0.2689 0.65 .076 2.481 0.0330 Side 9 0 0. 0.091 0.65 .076 2.628 0.0 Horiz. 10 90 0. 1.0 0.65 .076 2.628 0.1298 11 90 0. 1.0 0.65 .076 2.628 0.1298 12 0 0. 0.091 0.65 .076 2.628 0.0 span 13 45 0. 0.354 0.65 .054 2.680 0.0333 breakers 14 45 0. 0.354 0.65 .054 2.680 0.0333 brackets 15 90. 0. 1.0 2.0 .231 0.231 0.1070 SCDi*Di*li*cos… = 1.7836 s C D D D s C De e e i i De == = Σ = = = = ⎫ ⎬ ⎪ ⎭ ⎪ 0 8008 2 227 1 0 542 2 227 0 542 4109 20 2 . . / . . / . .. C equiv. model Me (model scale) C D D C De e e De . ... = === ⎫⎬ ⎪ ⎭⎪ 948 2 307 4109 C 2 0 equiv. model Me (full scale) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 69 Mobile Jack-Up Units Rev 3, August 2008 APPENDIX C4.B : COMPARISON CASES TO ASSESS IMPLICATIONS OF PRACTICE FORMULATION Computations are performed on a 'simplified model' with no mass. The irregular and regular wave results are computed according to the PRACTICE, Section 3 and 4. These computations are made to asses the implications of changes made concerning drag coefficients and wave kinematics formulations compared with previous practices. The significant wave height is chosen as judged realistic for the two water depths investigated: Water depth 30m: significant wave height Hsrp = 10m Water depth 90m: significant wave height Hsrp = 14m The period range specification is taken from PRACTICE, Section 3.5: ( . ) ( . ) . ( ) . ( ) 118 19 5 35 36 H T H H T H s s s Z s < < < < The current and current profile is often site dependent. The current is here set be constant over the water depth, extrapolated to sea surface. The example design for the computations is defined by: Three legs, split tube chords, Diameter chord (tubular) Dc = 0.7m, Rack width W = 0.8m, Diameter of braces Db = 0.3m, length of braces per m. height lb = 13.44m, leg spacing xleg = 50m leg diameter D1 = 10m COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 70 Mobile Jack-Up Units Rev 3, August 2008 Particulars for two existing practices and the PRACTICE Practice I: PRACTICE: Irregular waves: CD d l cos CD d l cos Tubular 1.0 0.3 13.44 0.6 = 2.419 1.0 0.3 13.44 0.6 = 2.419 Chord 1 2.114 0.7 1.0 1.0 = 1.479 2.057 0.7 1.0 1.0 = 1.440 Chord 2,3 1.279 0.7 2.0 1.0 = 1.790 1.056 0.7 1.0 2.0 = 1.478 CDeDe 5.688 z < 1.5m 5.338 z > 1.5m 4.491 kinematics according to Delta stretching Wheeler stretching Regular waves : Stokes' fifth Stokes' fifth (regular) Tubular 0.7 0.3 13.44 0.6 = 1.693 Chord 1 1.486 0.7 1.0 1.0 = 1.040 Chord 2,3 0.896 0.7 2.0 1.0 = 1.254 CDeDe = 3.989 No shielding assumed No shielding for waves Reduction of current by a factor 1/[1 + CDeDe/(4D1)] = 0.88 Practice II: Regular waves: Stokes' fifth Tubular 0.64 0.3 13.44 0.6 = 1.548 Chord 1 1.307 0.7 1.0 1.0 = 0.915 Chord 2,3 0.973 0.7 2.0 1.0 = 1.362 CDeDe = 3.825 Irregular waves: Airy with constant stretching CDeDe = 3.825 1.3 = 4.973 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 71 Mobile Jack-Up Units Rev 3, August 2008 Table C4.B.1 Comparison including wave height scaling, Water depth = 30 m, Hsrp = 10 m. Case Environment H/T Hs/Tz m and sec Current m/sec Base Shear MN Overturning Moment MNm Regular waves Practice I H = Hmax = 1.86 Hsrp 18.6/14.0 0.0 1.0 5.58 8.03 143 197 Regular waves Practice II H = Hmax = 1.86 Hsrp 18.6/14.0 0.0 1.0 5.42 7.70 139 189 Irregular waves Practice II Hs = Hsrp 10.0/11.0 0.0 1.0 3.18 6.89 108 145 Regular waves PRACTICE H = Hdet = 0.86 Hmax 16.5/14.0 0.0 0.88 4.90 6.96 115 157 Irregular Waves PRACTICE Hs = [1+.5exp(-d/25)] Hsrp 11.84/11.0 0.0 0.88 5.95 7.88 122 154 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 72 Mobile Jack-Up Units Rev 3, August 2008 Table C4.B.2 Comparison including wave height scaling, Water depth = 90 m, Hsrp = 14.0 M. Case Environment H/T Hs/Tz m and sec Current m/sec Base Shear MN Overturning Moment MNm Regular waves Practice I H = Hmax = 1.86 Hsrp 18.6/16.5 26.0/16.5 0.0 0.5 9.82 12.30 668 819 Regular waves Practice II H = Hmax = 1.86 Hsrp 18.6/16.5 26.0/16.5 0.0 0.5 9.41 11.79 641 785 Irregular waves Practice II Hs = Hsrp 14.0/13.0 14.0/13.0 0.0 0.5 11.22 13.11 747 859 Regular waves PRACTICE H = Hdet = 0.86 Hmax 23.14/16.5 23.14/16.5 0.0 0.44 8.90 11.20 578 709 Irregular Waves PRACTICE Hs = [1+.5exp(-d/25)] Hsrp 14.34/13.0 14.34/13.0 0.0 0.44 9.12 10.80 573 671 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 73 Mobile Jack-Up Units Rev 3, August 2008 Comments to the results The results for both the 30m and 90m water depth cases in Tables C4.B.1 and C4.B.2 show improved agreement between regular and irregular wave force calculations for the PRACTICE methodology as compared to Practice II. The main differences between Practice II and the PRACTICE are that: - the PRACTICE uses a reduced wave height for regular wave analysis instead of a reduced drag coefficient. - the PRACTICE includes a shallow water wave height correction to be applied to the significant wave height used in irregular wave analysis. The shallow water wave height correction term is described and justified in C3.5.1.1. The effect of wave asymmetry in shallow water in Practice II is included only by a conservative kinematics model above the mean water level for an irregular wave analysis. Other practices give no consideration to shallow water effects in irregular wave analysis. The agreement between regular and irregular wave forces is better at the 90m water depth case than for the 30m water depth case. However, the correction term for shallow water cases is justified as compared to the Practice II results. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 74 Mobile Jack-Up Units Rev 3, August 2008 APPENDIX C4.C : COMPARISON OF TEST RESULTS FOR CHORDS Split tube chords compared in the following rack ratio W/D F&G 1.08 NKK 1.10 MLMC 1.13 MSC 1.18 MLMC 1.24 Figure C4.C.1 : Comparison of PRACTICE formulation with model tests, ratio W/D = 1.08, [48] Figure C4.C.2 : Comparison of PRACTICE formulation with model tests, ratio W/D = 1.10, [50] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 75 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.C.3 : Comparison of PRACTICE formulation with model tests, ratio W/D = 1.13, [49] Figure C4.C.4 : Comparison of PRACTICE formulation with model tests, rack W/D = 1.18, [51] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 76 Mobile Jack-Up Units Rev 3, August 2008 Figure C4.C.5 : Comparison of PRACTICE formulation with model tests, rack W/D = 1.24, [49] COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 77 Mobile Jack-Up Units Rev 3, August 2008 C5 COMMENTARY TO CALCULATION METHODS - STRUCTURAL ENGINEERING C5.1 INTRODUCTION The application of the procedures and techniques given in Section 5 is consistent with the guidance given in the other sections of the Recommended Practice (PRACTICE). Furthermore, it is assumed that the user of the PRACTICE is familiar with the general philosophy and design/assessment approach specifically applicable to jack-ups. To provide additional guidance to the analyst less familiar with these procedures and to also ensure consistency of application by all users, this commentary has been prepared. In general, the structural modeling for the assessment of a jack-up must achieve the following objectives for both the static and (where applicable) dynamic responses: • Realistic global response (i.e. displacement, base shear, overturning moments, etc.) for the unit under the applicable environmental and functional loads. • Represent the correct linear and non-linear characteristics of the leg, leg-hull connection and the leg-foundation interaction. • Sufficient detail to allow for detailed assessment of the adequacy of the leg structure, structural/mechanical components of the jacking system and the foundation. C5.2 GENERAL Prior to beginning the actual modeling of the jack-up unit the analyst should ensure that all data necessary to perform the assessment is available. Refer first to the accompanying "Guideline for Site Specific Assessment of Mobile Jack-up Units" and Section 3 of the PRACTICE - Assessment Input Data for guidance on the data needed and for the rationale as to why they are important to the assessment procedure. Once these data are collected it would also benefit the analyst to review Section 4 - Calculation Methods - Hydrodynamics and Wind Forces and Section 6 - Calculation Methods - Geotechnical Engineering of the PRACTICE. This will serve not only as confirmatory check to assure the completeness of the data being collected for the analysis, but will also allow the analyst to evaluate the level of analysis techniques to be used in light of the computer software available. It is important that the analyst anticipate the complete scope of the assessment in terms of the level of quasi-static and dynamic analyses which may be required. This will allow the analyst to optimize the structural modeling and reduce the duplication of effort. In the remaining sections of this Section of the Commentary the analyst is guided through the overall structural modeling of a jack-up for the following: (1) Quasi-static analysis procedures (2) Assessment criteria procedures For guidance on dynamic analysis techniques, refer to Section 7 of the PRACTICE. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 78 Mobile Jack-Up Units Rev 3, August 2008 This Commentary has been focused on providing a general discussion of key points and their impact/importance on the final assessment results. Thus it is important that if additional detail is required, the analyst refer to appropriate technical references or contact the jack-up designer for further guidance. C5.3 GLOBAL RESPONSE C5.3.1 In the analysis of jack-ups the global response is developed by appropriate combination/modeling of both the first order (linear) response and the second order (non-linear) response. The first order response of a jack-up can be derived from models of varying degrees of complexity as discussed in Section 5.6 of the PRACTICE. Please refer to Figure C5.1 for the resulting response/reactions which are derived from a first order analysis. C5.3.2 The effects noted in Section 5.4 - 5.5 of the PRACTICE (e.g. leg inclination, P-Δ) should be determined and combined with the forces generated by the first order analysis. These effects have been shown to be significant (in varying degrees of importance) in the assessment of jack-ups based on the specific circumstances of the jack-up and the specific site conditions being considered. The actual treatment/derivation of the response is highly dependent on the modeling complexity chosen and the computer software analysis packages available to the analyst. The guidance given in Sections 5.4 - 5.5 of the PRACTICE allows for this needed flexibility in addressing the full spectrum of approaches by allowing for implicit incorporation of these second order effects by using the appropriate non-linear modeling capabilities of the computer software or by explicit addition of a conservative incorporation of these effects by approximate/simplified hand calculations. Please refer to Figure C5.2 for further representation of the effects of P-Δ and leg inclination and Figure C5.3 as to the applicable contribution of these second order effects that are required to be incorporated with the first order response. It should be noted that the PRACTICE recommends that P-Δ effects are included throughout the assessment. It also recommends that the effects of initial leg inclination are included only at the end of the analysis in the structural strength checks (by means of an additional applied moment). The derivation of the alternative geometric stiffness approach to P-Δ of Section 5.5.4.3 of the PRACTICE is given in Appendix C5.A. C5.3.3 Although the "Recommended Practice" gives guidance as to simplified calculations that can be performed for P-Δ and leg inclination, no specific guidance has been given for the additional moment caused by hull sagging. When a unit is installed on location the legs will normally engage the seabed with the hull supported by its own buoyancy in a hogged condition. Subsequently, with the hull slightly clear of the water, preload ballast will be taken on board thus preloading the legs to achieve their final penetration. This will normally lead to an extreme hull sagging condition. Finally the preload ballast is dumped and the hull elevated to the required airgap for the location. In this condition the hull will be sagging under self weight and variable loads. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 79 Mobile Jack-Up Units Rev 3, August 2008 As explained in Section 5.7 of the PRACTICE, the leg shear and bending moments caused by hull sagging are very dependent on leg guide clearances, the design of the jacking system, operational parameters and the modeling used in the analysis. A simplified approach for a conservative quantitative assessment is to assume that 25 to 50 percent of the theoretical hull sagging moment at the lower guide is seen in practice. This may be accounted for in a global model by reducing the distributed hull mass by 75 to 50 percent and applying the residual mass as point masses on the hull adjacent to the connections to the legs. This procedure is not applicable when hull stresses are required. A more thorough method is to apply self equilibrating pairs of forces/moments across the spring connections between hull and legs: An alternative approach is to allow a relaxation of the horizontal seabed restraint by means of prescribed displacements. C5.4 DISCUSSION OF THE LEG-HULL CONNECTION In addition to the importance of understanding the global response of the jack-up, it is important that the analyst has a full appreciation of the leg-hull interface. A representative leg-hull connection is shown in Figure C5.4. The basic function of the leg-hull connection is to provide for a transition of forces between the leg and hull via: 1) the upper and lower guide which transfer bending moments by a set of horizontal forces and 2) a jacking system and/or fixation system which transfers vertical load and bending moment via a set of vertical forces. Section 5.6.6 gives guidance on the detailed modeling requirements for each of the following components: • upper and lower guides • jacking pinions • fixed jacking system • floating jacking system • fixation system • shock pads • jackcase and associated bracing COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 80 Mobile Jack-Up Units Rev 3, August 2008 The various combinations of the above components to create the leg-hull connections on typical jack-ups now in service are given in Figure C5.5. Close attention to the leghull connection should be given by the analysts to ensure a thorough understanding of the jacking system so that proper modeling is realized. The number of key variables which must be properly incorporated are: • bending, shear and torsional stiffness of the leg between the upper and lower guide • axial, bending, shear and torsional stiffness of the jackcase stiffness of the upper and lower guides • amount of clearance/tolerance of the legs within the guides (see Figure C5.6) • amount of backlash in the jacking system (see Figure C5.7) • type of leg guide arrangement (see Figure C5.8) • rack/pinion arrangement (opposed versus unopposed pinions) (see Figure C5.9) When accounting for the effects of clearances (e.g. between guides and leg) in simpler models there are several approaches available: • For estimates of extreme behavior, use a 'secant stiffness' approach, so that the springs used provide a realistic displacement for the load/deflection levels expected. Thus the equivalent stiffness will include any slack behavior: • An alternative to the above, which is less sensitive to the initial estimate of load and deflection, is to use a pair of self equilibrating applied forces to represent the slack so that the spring is initially under a compressive load Po, where Po = kδo: Note: When using the methods above any spring with true tensile loading must be manually released. • For natural frequency calculations, providing that the gaps do not open and close, the use of the stiffness for closed gaps is appropriate. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 81 Mobile Jack-Up Units Rev 3, August 2008 C5.5 DETERMINATION OF PROPERTIES FOR EQUIVALENT MODELLING OF LEG AND LEG-HULL CONNECTION C5.5.1 Equivalent leg stiffness The determination of stiffnesses for the equivalent leg model referred to in Section 5.6.4b) of the PRACTICE may be accomplished the following means: • Hand calculations using the formulae presented in Figure 5.1 (after DNV, with corrections). Provided that there are no significant offsets between the brace work points these will be reasonably accurate for cases A (sideways K bracing), C (X bracing) and D (Z bracing); case B (normal K bracing) should be used with caution as the values of equivalent shear area and second moment of area are dependent on the number of bays being considered. If the leg scantlings change in different leg sections this can be accounted for by calculating the properties for each leg section and creating the equivalent leg model accordingly. • The application of unit load cases to a detailed leg model in accordance with Section 5.6.4 a) of the PRACTICE. The following load cases should be considered, applied about the major and minor axes of the leg: - Axial load. This is used to determine the axial area, A, of the equivalent beam according to standard theory: Δ Δ = => = FL AE A FL E where; Δ = axial deflection of cantilever at point of load application F = applied axial end load L = length of cantilever (from rigid support to point of load application) E = Young's modulus - Pure moment applied either as a moment or a couple. This is used to derive the second moment of area (I) according to standard beam theory: δ δ = => = ML I 2 ML2 2EI 2E and θ θ = => = ML EI I ML E where; δ = lateral end deflection of cantilever at point of load application M = applied end moment θ = end slope of cantilever at point of load application It should be noted that the value of I resulting from the two equations may differ somewhat. - Pure shear, P, applied at the end of the leg which may be used to derive I according to standard beam theory: θ θ = => = PL I 2 PL2 2EI 2E COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 82 Mobile Jack-Up Units Rev 3, August 2008 Using either this value of I, or a value obtained from the pure moment case, the effective shear area, As, can then be determined from: δ δ = + => = − PL EI PL AG A PLI EI PL s s 3 3 3 78 3 . where; G = shear modulus = E/2.6 for poissons ratio of 0.3 C5.5.2 Equivalent leg-hull connection stiffness The determination of stiffnesses for the equivalent leg-hull connection model referred to in Section 5.6.6 f) of the PRACTICE may be accomplished the following means: • Hand calculations using the formulae presented in Section 7.3.5.3 of the PRACTICE. • The application of unit load cases to a detailed leg model in combination with a detailed leg-hull connection model in accordance with Sections 5.6.4 a) and 5.6.6 a)-e) of the PRACTICE. Unit load cases are again applied, as described in C5.5.1. In this instance the differences between the results from the detailed leg model alone (see C5.5.1) and the detailed leg plus leg-hull connection model allow the effective stiffness of the connection to be determined: - Axial load. This is used to determine the vertical leg-hull connection stiffness, Kvh from the axial end displacements of the detailed leg model, Δ, and the axial end displacements of the combined leg and leg-hull connection model, ΔC, under the action of the same loading, F: Kvh = F/(ΔC-Δ) - Pure moment applied either as a moment or a couple. This is used to derive the rotational connection stiffness, Krh from either the end slopes, θ and θC, or the end deflections, δ and δC, of the two models under the action of the same end moment, M: Krh = M/(θC-θ) or Krh = ML/(δC-δ) - Pure shear which may be used to determine the horizontal leg-hull connection stiffness, Khh, in a similar manner, accounting for the rotational stiffness already derived. Normally the horizontal leg-hull connection stiffness may be assumed infinite. If the model contains nonlinearities due to the inclusion of gap elements care should be taken to ensure that suitable levels of 'unit' loading are applied such that the derived stiffness is applicable to the analysis to be undertaken. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 83 Mobile Jack-Up Units Rev 3, August 2008 C5.6 LOAD APPLICATION Section 5.7 of the PRACTICE indicates appropriate methods for applying the various loads to the analytical model(s). The importance of capturing the distributed nature of the self weight and distributed loadings is emphasized. C5.7 EVALUATION OF FORCES This Commentary is directly applicable for the structural modeling of jack-ups for either quasi-static or dynamic analysis. Key points which impact the final conclusions drawn from the assessments of jack-ups have been emphasized to complement the guidance given in the PRACTICE. A successful analysis will conclude with a set of forces which can then be used in the final evaluation of the adequacy of the unit the specific site, as contained in Section 8.0 - Assessment Criteria. The specific areas of review include: • Structural Strength Check (see Section 8.1 of the PRACTICE). • Overturning Stability (see Section 8.2 of the PRACTICE). • Foundation Assessment (see Section 8.3 of the PRACTICE): - Bearing Capacity - Sliding Resistance. • Other Responses of Interest (see Sections 8.4, 8.5 and 8.6 of the PRACTICE respectively): - Horizontal Deflection - Holding Capacity of the Jacking System - Hull Strength (if required). Care should be taken to ensure that the appropriate load factor is reflected in the determination of the load set applied during the analysis. This allows for direct use of the resulting loads in the assessment formulation. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 84 Mobile Jack-Up Units Rev 3, August 2008 Figure C5.1 : Responses/reactions from first order analyses Figure C5.2 : P-Δ and leg inclination effects COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 85 Mobile Jack-Up Units Rev 3, August 2008 Figure C5.3 : Contribution of Second Order Effects to First Order Responses Figure C5.4 : Representative leg-hull connection COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 86 Mobile Jack-Up Units Rev 3, August 2008 Figure C5.5 : Leg-hull connection component combinations Figure C5.6 : Guide clearances NB: Additional backlash may arise due to slack in gear train, clearances between floating elevating system and shockpads etc. Figure C5.7 : Jacking system backlash COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 87 Mobile Jack-Up Units Rev 3, August 2008 Figure C5.8 : Types of leg guide arrangement Figure C5.9 : Unopposed and opposed pinion arrangements COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 88 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C5 A = axial area of equivalent beam. As = effective shear area of equivalent beam. E = Young's modulus. F = applied axial end load. G = shear modulus = E/2.6 for poissons ratio of 0.3. I = second moment of area of equivalent beam. Khh = horizontal leg-hull connection stiffness. Krh = rotational leg-hull connection stiffness. Kvh = vertical leg-hull connection stiffness. L = length of cantilever (from rigid support to point of load application). M = applied end moment. P = applied end shear. δ = lateral end deflection of cantilever at point of load application for detailed leg model alone. δC = lateral end deflection of cantilever at point of load application for detailed leg plus leg-hull connection model. Δ = axial deflection of cantilever at point of load application for detailed leg model alone. Δ C = axial deflection of cantilever at point of load application for detailed leg plus leghull connection model. θ = end slope of cantilever at point of load application for detailed leg model alone. θC = end slope of cantilever at point of load application for detailed leg plus leg-hull connection model. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 89 Mobile Jack-Up Units Rev 3, August 2008 APPENDIX C5.A - DERIVATION OF ALTERNATIVE GEOMETRIC STIFFNESS FORMULATION FOR P-Δ EFFECTS C5.A.1 SUMMARY The method described below allows a simple procedure for incorporating P-Δ effects in a jack-up structural analysis. The advantage of this simple procedure is the ability to include such effects without the necessity to adopt the iterative procedures required by other methods. This method is accurate in determining the global response parameters, including hull displacement and base overturning moment. It is also accurate in determining the leg moment below the lower guide (usually the most critical part of the leg). In its simplest form the procedure will conservatively predict the shear in the legs (by roughly 10%). However leg shear is rarely a controlling factor in structural assessments; therefore this difference is insignificant. C5.A.2 DESCRIPTION OF THE METHOD It is assumed that a structural computer model of a jack-up is used to determine the effects of applied loads. Typically, a 'static' wave load is applied to a structural model, and resulting deflections, forces and moments are determined. Note, however, that the method can be similarly applied to dynamic analysis. (The method may not be permitted by some software packages which 'prohibit' the use of a negative spring stiffness). The incorporation of P-Δ effects in the structural analysis is accomplished by including a correction term in the global stiffness matrix of the structure. When an analysis is performed with the correction term included, the resulting deflections, etc. will include P-Δ effects. Note that since the global stiffness matrix is modified before the analysis, no subsequent changes to the matrix are required (i.e. no iterations are required in the solution). The correction term to the global stiffness matrix is determined by a simple hand calculation: The correction term is: -Pg/L where; Pg = Effective hull gravity load. This includes hull weight and weight of the legs above the hull. L = The distance from the spudcan point of rotation to the hull center of gravity. This single (negative) value is then incorporated into the global stiffness matrix of the jack-up structural model. This can be accomplished in various ways depending on the software in use. Typically, an orthogonal pair of horizontal translational earthed spring elements can be attached to a node representing the hull center of gravity, and the negative value is entered for each of the spring constants. Some software packages allow direct matrix manipulation. The effect of the negative stiffness is to produce an additional overturning load at the hull. The overturning moment produced by this lateral load about the base is equal to the overturning moment caused by the vertical load (of hull and legs above the hull) times the deflection of the hull. Thus, the effect of the translation of the vertical load is incorporated as a lateral force couple. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 90 Mobile Jack-Up Units Rev 3, August 2008 C5.A.3 BASIS FOR THE METHOD The P-Δ effect is a consideration of the displacement of the structure under the applied loads. In its most general form, the solution considers the displacements of each element of the structure under loading. This is typically called a 'large displacement' solution. In this general procedure, the deflections of the structure are used to reform the stiffness matrix, which is then used to recalculate the displacements. While this is analytically correct, there is a requirement to resolve the stiffness matrix several times for each loading condition. If the overall structural displacements are not very large, approximate solutions may be used. Typically, approximate solutions are valid if tanθ ≈ θ, where θ is the rotation of the structure about its base. These approximate solutions are known as 'geometric stiffness' solutions. The classical column moment magnification or 'Euler amplification' term is an example. The simple method presented here is another example. A comparison of these two methods is given in Section C5.A.4 and the derivation is presented in Section C5.A.5. The P-Δ effect for jack-up structures is manifested as a change in lateral stiffness of the individual legs, given a change in the axial load in each leg. For jack-ups the change in axial load in each leg is caused by the application of the gravity loading and environmental loading. As shown in Section C5.A.5, the net effect on the P-Δ of the axial load changes in each leg due to the environmental loading will cancel out. Thus, for overall structural response, only the gravity load need be considered in the calculation of P-Δ effects. The reduced stiffness will then affect the response to environmental loadings. C5.A.4 VERIFICATION AGAINST 'EXACT' SOLUTION Verification of this simple procedure was made against an 'exact' solution. In this case, the 'exact' solution was performed using analysis software which accounts for large displacements. In this procedure, the displaced configuration of the structure is used to update the stiffness matrix, and iteration is used to converge on a given solution. Verification was performed using a jack-up structural model as shown in Figure C5.A.1. The leg chord, horizontal and diagonal members are modeled as individual elements. The hull (in this case) is assumed to act as a rigid body. The hull to leg connection included leg clamping devices. These were modeled along with the leg guides. For the purpose of this verification the detailing of the hull and leg/hull connection is not important. The spudcans were modeled as 'pinned'. Loading of the model was accomplished as shown on Figure C5.A.2. Loadings due to wave and wind (and dynamic inertial) were considered separately to verify the behavior under the two separate types of loading. The loading direction was towards the bow in both cases. For each case, a vertical load was applied at the hull center of gravity. It is interesting to note that the vertical load is necessary for solution using 'exact' large displacement methods, but is not needed to obtain a solution using the simple method. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 91 Mobile Jack-Up Units Rev 3, August 2008 A summary of the comparison results is given on Tables C5.A.1 (wave load) and C5.A.2 (wind load). Verification with these two load cases was done separately, since the loading occurs on different parts of the structure. The level of loading is arbitrary. Values assumed here are greater than used in the site assessment of this particular jackup. Discussion of the individual response parameters from Tables C5.A.1 and C5.A.2 is given below. C5.A.4.1 Global Response Parameters The fundamental response quantities of deck displacement and overturning moment agree to within 1%. The base shear for the simple method is not correct since it includes the additional (fictitious) lateral force applied to the hull. The difference between the total applied force and the base shear is the additional lateral force applied at the hull. In theory the moment due to the vertical load (P-Δ moment) should be replaced by a lateral force couple, i.e. lateral loads at the hull and base. Reduction of the base shear (in global axes) by this additional lateral force at the hull will equate the global base shear with the applied load. C5.A.4.2 Windward and Leeward leg parameters The values for individual leg axial load and moment at the lower guide agree to within 1%. These quantities are the most critical parameters for structural assessments. The distribution of global base shear among the individual legs is not as accurately matched by the simple method. For each leg, the lateral stiffness is decreased by increasing axial load. Thus, the distribution of global base shear will depend on the axial load present in each leg. The simple method, since it lumps the effects of all legs into one correction term, cannot accurately predict the shear re-distribution among the legs. This lack of re-distribution of global base shear loading is not generally important to a structural assessment. The amount will depend on the level and type of loading (wave or wind). For the two cases given, 1% and 5% of the total base shear load (in global axes) is shifted from the leeward leg to the windward legs. When the leg base shears are not corrected, the simple method conservatively overpredicts the shear in the legs. Since shear force is not as critical as the leg bending moment this conservatism is not very restrictive. If a correction is desired, the added lateral load at the hull can be subtracted in equal fractions from the leg spudcan reactions (in global axes). Note that, for the case of the windward leg, this will slightly under-predict the 'correct' global shear reaction. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 92 Mobile Jack-Up Units Rev 3, August 2008 TABLE C5.A.1 - VERIFICATION OF SIMPLE PROCEDURE FOR P-Δ EFFECT WITH EXACT SOLUTION - WAVE LOADING CASE No P-Δ Simple Method Exact Solution Global response parameters Hull displacement (inches) 21.6 24.5 24.7 Base OTM (Kip-ft x 103) 227. 253. 251. Base shear (kips) 711. 780. 711. (Added lateral load at hull, kips) (69.) Windward leg parameters Axial force (kips) 3638. 3524. 3534. Shear at spudcan (kips) 250. 272. 254. (Corrected by 69/3 = 23 kips) (249.) Moment at lower guide (Kip-ft x 103) 48. 56. 56. Leeward leg parameters Axial force (kips) 5477. 5706. 5685. Shear at spudcan (kips) 212. 235. 204. (Corrected by 69/3 = 23 kips) (212.) Moment at lower guide (Kip-ft x 103) 57. 65. 65. Shear transferred from leeward leg to 0. 8. windward legs due to P-Δ (kips) TABLE C5.A.2 - VERIFICATION OF SIMPLE PROCEDURE FOR P-Δ EFFECT WITH EXACT SOLUTION - WIND LOADING CASE No P-Δ Simple Method Exact Solution Global response parameters Hull displacement (inches) 44.9 51.0 51.4 Base OTM (Kip-ft x 103) 490. 545. 541. Base shear (kips) 1055. 1198. 1055. (Added lateral load at hull, kips) (143.) Windward leg parameters Axial force (kips) 2538. 2300. 2318. Shear at spudcan (kips) 352. 399. 375. (Corrected by 143/3 = 48 kips) (351.) Moment at lower guide (Kip-ft x 103) 124. 141. 141. Leeward leg parameters Axial force (kips) 7803. 8279. 8242. Shear at spudcan (kips) 352. 400. 305. (Corrected by 143/3 = 48 kips) (352.) Moment at lower guide (Kip-ft x 103) 124. 141. 140. Shear transferred from leeward leg to 0. 47. windward legs due to P-Δ (kips) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 93 Mobile Jack-Up Units Rev 3, August 2008 Figure C5.A.1 - Analysis model Figure C5.A.2 - Load application COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 94 Mobile Jack-Up Units Rev 3, August 2008 C5.A.5 DERIVATION OF THE SIMPLIFIED CORRECTION TERM Beam Deflection Moment diagram (due to secondary bending only) Ref.: Salmon and Johnson, 'Steel Structures', p 620. y0 = Deflection without axial load, P y1 = Additional lateral deflection due to axial load, P To calculate y1, take moment of M/EI diagram between support and midspan y1 = P(y y EI 0 1 2L 2L + ⎧⎨⎩ ⎫⎬⎭ ⎧⎨⎩ ⎫⎬⎭ ) π π Centroid of area under moment diagram Area under moment diagram Rearranging: y1 = (y0 + y1) 4PL2 π2EI using: PE = π 2 2 EI (kL) (with k = 2) y1 = (y0 + y1) P PE y1 = y0 P P P P E E / 1− / ⎧⎨⎩ ⎫⎬⎭ Total lateral deflection: ymax = y0 + y1 ymax = y0 + y0 P P P P E E / 1− / ⎧⎨⎩ ⎫⎬⎭ = y0 1 1− ⎧⎨⎩ ⎫⎬⎭ P PE / 'Euler amplification' term COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 95 Mobile Jack-Up Units Rev 3, August 2008 Determine effect on stiffness Define Ko = H y0 Lateral stiffness without axial load, P = 3 3 EI L Define K1 = H ymax Lateral stiffness with axial load, P = H y P 0 PE 1− ⎧⎨⎩ ⎫⎬⎭ = Ko 1 4L2 2 − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ ⎧⎨⎩ ⎫⎬⎭ P π EI = Ko - P 3 4L 3 2 2 EI L EI ⎧⎨⎩ ⎫⎬⎭ ⎧⎨⎩ ⎫⎬⎭ π = Ko - 12 π2 P L ⎧⎨⎩ ⎫⎬⎭ Conclusion: Effective lateral stiffness reduced by - 12P π2L P = axial load in one leg Note: This is based on assuming a sine curve for deflection. Repeat calculations assuming a linear deflection (rather than a sine curve): y1 = P y y EI ( ) L L 0 1 2 2 3 + ⎧⎨⎩ ⎫⎬⎭ ⎧⎨⎩ ⎫⎬⎭ Centroid of area under moment diagram Area under moment diagram Rearranging: y1 = (y0 + y1) PL EI 2 3 y1 = y0 PL EI PL EI 2 2 3 1 3 / − / ⎧⎨⎩ ⎫⎬⎭ ymax = y0 + y1 ymax = y0 1 1− 2 3 ⎧⎨⎩ ⎫⎬⎭ PL / EI Amplification for linear assumption Determine effect on stiffness Define Ko = H y0 Lateral stiffness without axial load, P = 3 3 EI L COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 96 Mobile Jack-Up Units Rev 3, August 2008 Define K1 = H ymax Lateral stiffness with axial load, P = H y PL EI 0 2 1 3 − ⎧⎨⎩ ⎫⎬⎭ = Ko 1 3 2 − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ ⎧⎨⎩ ⎫⎬⎭ PL EI = Ko - P L Conclusion: Based on linear deflection assumption, lateral stiffness is reduced by -P/L term. This is the usual approximation of geometric stiffness. Effect on total jack-up stiffness: KE = Ke1 + Ke2 + Ke3 sum of individual leg stiffnesses (neglects hull rotation) For each leg: P = Pgravity + Penvironment KE = [k01 - 12 1 π2 L (Pg1 + Pe1)] + [k02 - 12 1 π2 L (Pg2 + Pe2)] + … = (k01 + k02 + k03) - 12 1 π2 L (Pg1 + Pg2 + Pg3) - 12 1 π2 L (Pe1 + Pe2 + Pe3) Assume net vertical environmental load (Pe1 + Pe2 + Pe3) = 0 KE = (ΣK0i) - 12 π2 P L G , where PG is total gravity load only If linear deflection assumption is made: KE = (ΣK0i) - P L G COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 97 Mobile Jack-Up Units Rev 3, August 2008 C6 COMMENTARY TO CALCULATION METHODS – GEOTECHNICAL ENGINEERING C6.1 INTRODUCTION This Commentary is compiled to support Section 6 of the PRACTICE and should only be used as a reference document in conjunction with the text of the PRACTICE. A Glossary of Terms used for the Geotechnical Engineering Analysis is included at the end of this Commentary. C6.2 PREDICTION OF FOOTING PENETRATION DURING PRELOADING C6.2.1 Analysis Method for Leg Penetration Prediction The equations in Sections 6.2.2 and 6.2.3 may be applied for estimating the penetration of the spudcan during preloading. In this case the backflow and contribution of the spudcan buoyancy (due to the weight of soil replaced by the spudcan) will have a direct effect on the penetration depth. Hence the effect of backflow and spudcan buoyancy should be included in the calculations. Predictions of spudcan penetration are based on a direct application of conventional bearing capacity formulae for shallow circular flat foundations. However, the analysis methods for shallow foundations and spudcan penetration predictions are fundamentally different as illustrated in Figure C6.1. Conventional foundation analyses for a circular footing at depth D firstly comprise the determination of the ultimate bearing capacity, FV, at this depth and subsequently computing the vertical displacement of this footing, zu, which is required to mobilize this resistance. Thus the analyses consist of a strength analysis followed by a deformation analysis. Figure C6.1 : Comparison of bearing capacity analytical procedures for shallow foundations and jack-ups COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 98 Mobile Jack-Up Units Rev 3, August 2008 In a spudcan penetration analysis the deformation at ultimate resistance (i.e. the spudcan penetration D) is taken as an input and from this the associated soil resistance is directly computed. The conventional analysis consist of only one step using the same bearing capacity criteria as for the former shallow foundation analyses. The incompatibility between these approaches is generally accounted for by the application of empirical corrections to classical bearing capacity formulations. These empirical corrections are generally introduced by the selection of appropriate soil strength parameters. It is also noted that these corrections account for other significant differences between conventional shallow foundations and spudcans, such as: 1. Spudcans are relatively smooth (steel) and (semi) conical whereas the other footings are usually rough (concrete) and flat. 2. Spudcan foundations stress soil which, during installation, has been subjected to large strains, whereas conventional foundations are placed on soil which has not failed. Also for conventional foundations the soil may have improved due to "pre-design" foundation loads causing increased strength by consolidation. 3. Spudcans are an order of magnitude larger than most conventional foundations. For the conservative evaluation of the hole backflow the PRACTICE recommends that the stability factors of Meyerhoff [1] are used. However, for normally consolidated clay profiles the Britto and Kusakabe [2] curve may be more appropriate (see Figure C6.2). It should be noted that the expression in Section 6.2.1 is based on static hole stability. In reality, during penetration of the spudcan the soil will probably flow along the spudcan upwards on to the top of the spudcan. Hence, the hole stability derived from the expression provided in Section 6.2.1 may be too optimistic. Figure C6.2: Stability factors for cylindrical excavations in clay COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 99 Mobile Jack-Up Units Rev 3, August 2008 C6.2.2 Penetration Analysis For Clays For the selection of undrained shear strength, cu, it is recommended that the mean value to a depth of half a spudcan diameter beneath the level where the maximum spudcan diameter is in contact with the soil is used (Young [3]). This method is applicable if the shear strength values up to one diameter below the spudcan do not vary more than 50 percent from the average value (after Skempton [4]). If significant cu variations occur, then the bearing capacity should be computed using a method for layered soil conditions. Analytical solutions are available for computing the bearing capacity of footings on clay with increasing shear strength with depth (Davis and Booker, [5]); Salencon and Matar, [6]; Houlsby and Wroth, [7]). These methods give bearing capacities less than those resulting from the use of Skempton's [4] and Vesic [8] relationships. Empirical correction factors for the Skempton [4] and the Davis and Booker [5] methods are recommended by Endley et al [9]. However these empirical methods take no account of the spudcan equivalent cone angle, the spudcan roughness factor or the depth of spudcan embedment of the uppermost part of the bearing area below the soil surface. An alternative bearing capacity factor Nc' has been developed which takes these factors, and that of increased shear strength with depth, into account. In this case the ultimate bearing capacity of a spudcan in clay can be expressed by: FV = {cuoNc' + po'} A The maximum preload, VLo, is equal to the ultimate vertical bearing capacity, FV, taking into account the effect of backflow, Fo'A, and the effective weight of the soil replaced by the spudcan, γ'V i.e.: VLo = FV - F'oA + γ'V noting that the terms -F'oA + γ'V should always be considered together. Table C6 provides values for Nc' which is an alternative dimensionless bearing capacity factor dependent on: (a) The equivalent cone angle of the spudcan β. For spudcans with multiple cone angles, the equivalent cone has a base equal to the base of the largest component and a volume equal to the total volume of the components, (b) The roughness factor for the spudcan surface α, (c) The depth of embedment of the uppermost part of the bearing area below the soil surface D, (d) The rate of increase of the undrained shear strength with depth below the spudcan "ρ" (see Figure C6.3). The alternative non-dimensional bearing capacity factors "Nc'" shown in Tables C6.1 to C6.6 have been derived using a computer program which is able to calculate lower bound (conservative) collapse loads for both axisymmetric and plane strain foundations. Vertical bearing capacity has been computed for all combinations of the following parameters: COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 100 Mobile Jack-Up Units Rev 3, August 2008 Figure C6.3: Conical footing bearing capacity - problem definition and notation Cone angle, β = 30°, 60°, 90°, 120°, 150°, 180°. Footing embedment depth, D/R = 0.0, 0.2, 0.5, 1.0, 2.0, 5.0. Roughness factor, α = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 (where α = 0.0 for fully smooth and 1.0 for fully rough) Rate of increase of clay shear strength with depth, ρ2R/cum = 0.0, 1.0, 2.0, 3.0, 4.0, 5.0. The effects of the depth of embedment and the rate of increase of shear strength with depth are expressed by use of the dimensionless factors D/2R and ρ2R/cum, where cum is the undrained strength at the soil surface (equal to cuo - Dρ assuming a linear variation of strength with depth) and R is the radius of the spudcan. Values of the dimensionless factor Nc' are given in Tables C6.1 to C6.6 for the range: β = 30° to 180° ; α = 0.0 to 1.0 D/2R = 0.0 to 2.5 ; ρ2R/cum = 0.0 to 5.0 The factors are calculated assuming a linear variation of undrained strength with depth. The best fit to the profile of undrained strength between the depth of the lowermost point of the maximum bearing area and one radius below that point should be used in deriving the value of ρ. In the model a field of slip lines is formed between the footing and the horizontal free soil surface. This type of "general shear" failure mechanism is appropriate for the shallow footing penetrations being considered. At larger embedments, however, the slip lines do not propagate to the surface as the "local shear" failure mechanism becomes critical (i.e. it gives a lower bearing capacity). A transition from general to local shear failure may be predicted at footing embedments between 6R and 8R. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 101 Mobile Jack-Up Units Rev 3, August 2008 The greatest embedment considered in the tables is 5R, so the general shear bearing capacity factors are still appropriate for this depth. Therefore Table C6.6 should not be extrapolated to higher values of D/2R, since the bearing capacity factor does not increase significantly with further embedment. Values for D/2R = 2.5 should be used for large embedments. Although a footing may be fully rough (α = 1.0), full adhesion is only mobilized at the cone surface when β ≤ 90°. For cone angles greater than 90°, only partial friction is mobilized. In general, if the roughness factor is α, full friction is mobilized only when β < π - sin-1α. This relationship may be derived using Mohr's Circle. For the selection of appropriate roughness factors the results of mathematical models (Noble Denton [10a]) suggest that the presence of a sharp secondary cone, forming the tip of spudcan, tends to cause "rough" behavior. Rough blunt spudcans behave in a similar manner to flat circular plates but more pointed spudcans behave as neither fully rough nor fully smooth and have intermediate roughness factors of between α = 0.3 to 0.5. In the absence of detailed information, and as an approximation, a value of α = 0.4 may be appropriate for typical "double cone" spudcan shapes. For further information regarding this alternative method for bearing capacity analysis in clay reference should be made to Houlsby [11, 12, 13], Koumoto [14] and Houlsby [15]. It is noted that footing penetration predictions are generally made using shear strength data from simple laboratory tests such as torvane, pocket penetrometer, motorvane and/or unconfined compression tests. Strength values from such tests are generally lower than those of higher quality in-situ or laboratory tests, particularly if samples for the latter tests are obtained from push/piston sampling rather than the percussion sampling method. It is likely that the former testing methods may yield low bearing capacity values for very sensitive clays and/or strongly strain softening clays. Engineering judgment is required in such cases to assess the likely footing penetration. It is noted that in some clays, following remolding during spudcan penetration, the shear strength may increase over a short time period. For certain clays the strength may be regained in a matter of hours. In such cases, a crust of stronger material may develop underneath the spudcan and this crust may then be underlain by weaker clay. In this condition a potential punch-through situation could occur during subsequent reloading. Several actual failures have been attributed to this type of soil behavior (Young et al., [3]). For soils where this type of strength hardening (thixotropy) is possible caution should be exercised as interruptions during the preloading operations could lead to severe consequences. For the conservative assessment of the effects of cyclic loading on clay foundations the following vertical bearing capacity reduction factors may be applied to the capacities calculated from static soil properties (Andersen [16]): Leeward leg vertical bearing capacity reduction factor = 1.0 Windward leg vertical bearing capacity reduction factor = 0.8 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER TABLE C6.1 TABLE C6.2 30 degrees cones FV/(Acuo) factors 60 degrees cones FV/(Acuo) factors ρ2R D cuo ρ2R Roughness ρ2R D cuo ρ2R Roughness --- - --- --- --- - --- --- cum R cum cuo 0.0 0.2 0.4 0.6 0.8 1.0 cum R cum cuo 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.0 1.00 0.00 4.61 5.51 6.38 7.22 8.03 8.78 0.0 0.0 1.00 0.00 4.45 4.96 5.45 5.90 6.32 6.69 0.0 0.2 1.00 0.00 4.80 5.70 6.56 7.40 8.20 8.95 0.0 0.2 1.00 0.00 4.68 5.19 5.67 6.12 6.53 6.90 0.0 0.5 1.00 0.00 5.05 5.94 6.80 7.63 8.43 9.18 0.0 0.5 1.00 0.00 4.98 5.50 5.96 6.40 6.81 7.18 0.0 1.0 1.00 0.00 5.41 6.29 7.14 7.79 8.76 9.50 0.0 1.0 1.00 0.00 5.41 5.90 6.37 6.81 7.21 7.57 0.0 2.0 1.00 0.00 5.98 6.85 7.70 8.51 9.29 10.03 0.0 2.0 1.00 0.00 6.07 6.55 7.01 7.43 7.84 8.18 0.0 5.0 1.00 0.00 7.12 7.98 8.81 9.61 10.38 11.10 0.0 5.0 1.00 0.00 7.33 7.81 8.25 8.66 9.05 9.39 1.0 0.0 1.00 1.00 7.53 9.02 10.46 11.84 13.19 14.46 1.0 0.0 1.00 1.00 5.81 6.51 7.15 7.77 8.34 8.87 1.0 0.2 1.10 0.91 7.45 8.89 10.27 11.61 12.90 14.13 1.0 0.2 1.10 0.91 5.92 6.59 7.23 7.83 8.38 8.89 1.0 0.5 1.25 0.80 7.38 8.73 10.05 11.32 12.55 13.72 1.0 0.5 1.25 0.80 6.04 6.70 7.30 7.88 8.42 8.91 1.0 1.0 1.50 0.67 7.28 8.55 9.78 10.98 12.14 13.24 1.0 1.0 1.50 0.67 6.20 6.84 7.41 7.96 8.47 8.94 1.0 2.0 2.00 0.50 7.20 8.38 9.51 10.61 11.68 12.68 1.0 2.0 2.00 0.50 6.43 7.05 7.58 8.12 8.59 9.03 1.0 5.0 3.50 0.29 7.34 8.39 9.39 10.37 11.30 12.19 1.0 5.0 3.50 0.29 6.97 7.55 8.08 8.54 8.98 9.39 2.0 0.0 1.00 2.00 10.45 12.51 14.51 16.44 18.31 20.10 2.0 0.0 1.00 2.00 7.14 8.02 8.84 9.60 10.32 10.99 2.0 0.2 1.20 1.67 9.65 11.53 13.33 15.08 16.79 18.40 2.0 0.2 1.20 1.67 6.92 7.73 8.49 9.21 9.88 10.50 2.0 0.5 1.50 1.33 8.89 10.58 12.19 13.76 15.27 16.72 2.0 0.5 1.50 1.33 6.74 7.50 8.18 8.84 9.46 10.03 2.0 1.0 2.00 1.00 8.20 9.67 11.09 12.47 13.80 15.08 2.0 1.0 2.00 1.00 6.59 7.29 7.91 8.53 9.09 9.61 2.0 2.0 3.00 0.67 7.60 8.87 10.10 11.30 12.45 13.54 2.0 2.0 3.00 0.67 6.55 7.20 7.76 8.33 8.83 9.30 2.0 5.0 6.00 0.33 7.37 8.44 9.48 10.18 11.44 12.35 2.0 5.0 6.00 0.33 6.99 7.49 8.03 8.50 8.95 9.37 3.0 0.0 1.00 3.00 13.36 15.98 18.56 21.03 23.42 25.71 3.0 0.0 1.00 3.00 8.49 9.54 10.50 11.42 12.29 13.10 3.0 0.2 1.30 2.31 11.51 13.76 15.92 18.02 20.05 22.00 3.0 0.2 1.30 2.31 7.77 8.70 9.56 10.38 11.14 11.85 3.0 0.5 1.75 1.71 9.98 11.89 13.72 15.49 17.21 18.85 3.0 0.5 1.75 1.71 7.24 8.03 8.80 9.53 10.20 10.82 3.0 1.0 2.50 1.20 8.74 10.33 11.87 13.36 14.80 16.18 3.0 1.0 2.50 1.20 6.82 7.56 8.21 8.86 9.45 10.00 3.0 2.0 4.00 0.75 7.79 9.11 10.39 11.64 12.83 13.98 3.0 2.0 4.00 0.75 6.60 7.27 7.85 8.44 8.94 9.43 3.0 5.0 8.50 0.35 7.40 8.46 9.51 10.52 11.49 12.42 3.0 5.0 8.50 0.35 6.99 7.47 8.01 8.49 8.94 9.36 4.0 0.0 1.00 4.00 16.27 19.46 22.57 25.62 28.52 31.32 4.0 0.0 1.00 4.00 9.83 11.02 12.16 13.24 14.26 15.18 4.0 0.2 1.40 2.86 13.10 15.68 18.14 20.54 22.86 25.08 4.0 0.2 1.40 2.86 8.51 9.52 10.48 11.38 12.22 13.00 4.0 0.5 2.00 2.00 10.83 12.87 14.86 16.79 18.66 20.44 4.0 0.5 2.00 2.00 7.61 8.44 9.26 10.04 10.75 11.41 4.0 1.0 3.00 1.33 9.11 10.77 12.38 13.96 15.47 16.91 4.0 1.0 3.00 1.33 6.97 7.74 8.41 9.08 9.69 10.26 4.0 2.0 5.00 0.80 7.91 9.26 10.57 11.84 13.06 14.23 4.0 2.0 5.00 0.80 6.64 7.31 7.90 8.49 9.01 9.51 4.0 5.0 11.00 0.36 7.40 8.47 9.52 10.54 11.52 12.46 4.0 5.0 11.00 0.36 6.86 7.45 8.00 8.48 8.94 9.35 5.0 0.0 1.00 5.00 19.18 22.94 26.61 30.20 33.63 36.92 5.0 0.0 1.00 5.00 11.17 12.52 13.83 15.06 16.20 17.26 5.0 0.2 1.50 3.33 14.48 17.33 20.06 22.72 25.29 27.75 5.0 0.2 1.50 3.33 9.14 10.23 11.26 12.25 13.15 13.99 5.0 0.5 2.25 2.22 11.46 13.64 15.75 17.80 19.78 21.68 5.0 0.5 2.25 2.22 7.90 8.78 9.63 10.43 11.17 11.87 5.0 1.0 3.50 1.43 9.37 11.08 12.77 14.38 15.94 17.43 5.0 1.0 3.50 1.43 7.08 7.84 8.55 9.24 9.86 10.45 5.0 2.0 6.00 0.83 7.98 9.35 10.68 11.97 13.21 14.40 5.0 2.0 6.00 0.83 6.66 7.32 7.94 8.53 9.06 9.56 5.0 5.0 13.50 0.37 7.40 8.47 9.53 10.56 11.55 12.48 5.0 5.0 13.50 0.37 6.85 7.44 7.99 8.47 8.93 9.35 Commentaries to Recommended Practice for Site Specific Assessment of Page 102 Mobile Jack-Up Units Rev 3, August 2008 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER TABLE C6.3 TABLE C6.4 90 degrees cones FV/(Acuo) factors 120 degrees cones FV/(Acuo) factors ρ2R D cuo ρ2R Roughness ρ2R D cuo ρ2R Roughness --- - --- --- --- - --- --- cum R cum cuo 0.0 0.2 0.4 0.6 0.8 1.0 cum R cum cuo 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.0 1.00 0.00 4.64 5.02 5.36 5.67 5.95 6.17 0.0 0.0 1.00 0.00 4.96 5.25 5.51 5.73 5.92 6.05 0.0 0.2 1.00 0.00 4.90 5.28 5.61 5.91 6.18 6.41 0.0 0.2 1.00 0.00 5.23 5.52 5.77 5.99 6.17 6.30 0.0 0.5 1.00 0.00 5.22 5.59 5.93 6.23 6.49 6.71 0.0 0.5 1.00 0.00 5.57 5.85 6.10 6.31 6.49 6.62 0.0 1.0 1.00 0.00 5.68 6.03 6.36 6.66 6.92 7.14 0.0 1.0 1.00 0.00 6.04 6.31 6.55 6.76 6.93 7.05 0.0 2.0 1.00 0.00 6.37 6.71 7.05 7.32 7.58 7.79 0.0 2.0 1.00 0.00 6.74 7.01 7.24 7.44 7.61 7.72 0.0 5.0 1.00 0.00 7.65 8.03 8.32 8.60 8.86 9.05 0.0 5.0 1.00 0.00 8.07 8.32 8.55 8.75 8.90 8.99 1.0 0.0 1.00 1.00 5.57 6.05 6.47 6.87 7.22 7.53 1.0 0.0 1.00 1.00 5.69 6.04 6.36 6.65 6.89 7.09 1.0 0.2 1.10 0.91 5.74 6.21 6.62 7.00 7.36 7.65 1.0 0.2 1.10 0.91 5.89 6.24 6.55 6.82 7.07 7.26 1.0 0.5 1.25 0.80 5.94 6.38 6.79 7.16 7.50 7.79 1.0 0.5 1.25 0.80 6.12 6.45 6.76 7.02 7.26 7.45 1.0 1.0 1.50 0.67 6.16 6.61 6.99 7.36 7.68 7.97 1.0 1.0 1.50 0.67 6.39 6.72 7.01 7.27 7.48 7.66 1.0 2.0 2.00 0.50 6.50 6.93 7.30 7.64 7.95 8.21 1.0 2.0 2.00 0.50 6.80 7.10 7.37 7.61 7.82 7.97 1.0 5.0 3.50 0.29 7.25 7.57 7.94 8.25 8.53 8.78 1.0 5.0 3.50 0.29 7.52 7.82 8.08 8.29 8.49 8.61 2.0 0.0 1.00 2.00 6.46 7.03 7.54 8.01 8.45 8.82 2.0 0.0 1.00 2.00 6.38 6.79 7.16 7.50 7.80 8.04 2.0 0.2 1.20 1.67 6.41 6.94 7.43 7.88 8.28 8.65 2.0 0.2 1.20 1.67 6.41 6.80 7.16 7.47 7.75 7.97 2.0 0.5 1.50 1.33 6.41 6.88 7.35 7.76 8.14 8.46 2.0 0.5 1.50 1.33 6.46 6.83 7.17 7.46 7.72 7.94 2.0 1.0 2.00 1.00 6.40 6.88 7.29 7.69 8.03 8.35 2.0 1.0 2.00 1.00 6.56 6.91 7.22 7.49 7.74 7.92 2.0 2.0 3.00 0.67 6.54 6.99 7.37 7.73 8.06 8.33 2.0 2.0 3.00 0.67 6.80 7.12 7.40 7.65 7.87 8.03 2.0 5.0 6.00 0.33 7.16 7.49 7.86 8.18 8.47 8.72 2.0 5.0 6.00 0.33 7.43 7.72 7.99 8.21 8.41 8.53 3.0 0.0 1.00 3.00 7.36 8.00 8.59 9.14 9.65 10.08 3.0 0.0 1.00 3.00 7.04 7.51 7.93 8.31 8.66 8.93 3.0 0.2 1.30 2.31 6.99 7.57 8.10 8.60 9.05 9.45 3.0 0.2 1.30 2.31 6.84 7.27 7.65 8.00 8.31 8.57 3.0 0.5 1.75 1.71 6.70 7.24 7.73 8.17 8.59 8.94 3.0 0.5 1.75 1.71 6.71 7.09 7.45 7.76 8.05 8.27 3.0 1.0 2.50 1.20 6.54 7.04 7.47 7.88 8.24 8.57 3.0 1.0 2.50 1.20 6.66 7.02 7.34 7.63 7.88 8.08 3.0 2.0 4.00 0.75 6.56 7.02 7.41 7.78 8.11 8.39 3.0 2.0 4.00 0.75 6.81 7.11 7.41 7.67 7.89 8.06 3.0 5.0 8.50 0.35 7.12 7.46 7.83 8.15 8.44 8.46 3.0 5.0 8.50 0.35 7.38 7.68 7.95 8.17 8.38 8.51 4.0 0.0 1.00 4.00 8.22 8.96 9.64 10.25 10.82 11.33 4.0 0.0 1.00 4.00 7.70 8.22 8.69 9.11 9.49 9.81 4.0 0.2 1.40 2.86 7.49 8.11 8.68 9.22 9.70 10.14 4.0 0.2 1.40 2.86 7.20 7.66 8.07 8.44 8.77 9.03 4.0 0.5 2.00 2.00 6.94 7.50 8.01 8.48 8.92 9.29 4.0 0.5 2.00 2.00 6.88 7.28 7.65 7.98 8.27 8.53 4.0 1.0 3.00 1.33 6.63 7.15 7.58 8.01 8.38 8.72 4.0 1.0 3.00 1.33 6.72 7.08 7.42 7.71 7.97 8.18 4.0 2.0 5.00 0.80 6.57 7.03 7.43 7.80 8.14 8.42 4.0 2.0 5.00 0.80 6.80 7.12 7.41 7.68 7.90 8.08 4.0 5.0 11.00 0.36 7.05 7.44 7.81 8.13 8.42 8.67 4.0 5.0 11.00 0.36 7.39 7.66 7.93 8.15 8.36 8.49 5.0 0.0 1.00 5.00 9.11 9.93 10.66 11.35 12.00 12.56 5.0 0.0 1.00 5.00 8.35 8.91 9.43 9.89 10.31 10.67 5.0 0.2 1.50 3.33 7.87 8.55 9.17 9.74 10.26 10.75 5.0 0.2 1.50 3.33 7.52 7.99 8.43 8.82 9.18 9.95 5.0 0.5 2.25 2.22 7.12 7.71 8.24 8.72 9.17 9.57 5.0 0.5 2.25 2.22 7.01 7.43 7.81 8.15 8.45 8.72 5.0 1.0 3.50 1.43 6.70 7.22 7.67 8.09 8.47 8.82 5.0 1.0 3.50 1.43 6.77 7.13 7.47 7.77 8.03 8.25 5.0 2.0 6.00 0.83 6.57 7.04 7.44 7.82 8.16 8.44 5.0 2.0 6.00 0.83 6.80 7.12 7.42 7.69 7.91 8.09 5.0 5.0 13.50 0.37 7.03 7.42 7.80 8.12 8.41 8.66 5.0 5.0 13.50 0.37 7.34 7.64 7.91 8.14 8.34 8.48 TABLE C6.5 TABLE C6.6 Commentaries to Recommended Practice for Site Specific Assessment of Page 103 Mobile Jack-Up Units Rev 3, August 2008 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER 150 degrees cones FV/(Acuo) factors 180 degrees cones FV(Acuo) factors ρ2R D cuo ρ2R Roughness ρ2R D cuo ρ2R Roughness --- - --- --- --- - --- --- cum R cum cuo 0.0 0.2 0.4 0.6 0.8 1.0 cum R cum cuo 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.0 1.00 0.00 5.32 5.55 5.74 5.89 6.01 6.05 0.0 0.0 1.00 0.00 5.69 5.86 5.97 6.03 6.05 6.05 0.0 0.2 1.00 0.00 5.60 5.82 6.00 6.16 6.26 6.30 0.0 0.2 1.00 0.00 5.97 6.13 6.24 6.29 6.30 6.30 0.0 0.5 1.00 0.00 5.94 6.16 6.34 6.49 6.59 6.61 0.0 0.5 1.00 0.00 6.31 6.47 6.57 6.61 6.61 6.61 0.0 1.0 1.00 0.00 6.41 6.62 6.80 6.94 7.03 7.05 0.0 1.0 1.00 0.00 6.79 6.93 7.02 7.05 7.05 7.05 0.0 2.0 1.00 0.00 7.13 7.32 7.49 7.62 7.71 7.72 0.0 2.0 1.00 0.00 7.49 7.63 7.70 7.71 7.71 7.71 0.0 5.0 1.00 0.00 8.46 8.65 8.81 8.93 8.99 8.99 0.0 5.0 1.00 0.00 8.82 8.94 8.99 8.99 8.99 8.99 1.0 0.0 1.00 1.00 5.94 6.22 6.46 6.67 6.84 6.97 1.0 0.0 1.00 1.00 6.25 6.47 6.65 6.79 6.90 6.95 1.0 0.2 1.10 0.91 6.16 6.43 6.67 6.87 7.04 7.15 1.0 0.2 1.10 0.91 6.48 6.69 6.87 7.00 7.10 7.14 1.0 0.5 1.25 0.80 6.41 6.67 6.90 7.09 7.25 7.36 1.0 0.5 1.25 0.80 6.74 6.94 7.11 7.23 7.32 7.35 1.0 1.0 1.50 0.67 6.71 6.96 7.18 7.36 7.51 7.60 1.0 1.0 1.50 0.67 7.05 7.24 7.39 7.51 7.58 7.60 1.0 2.0 2.00 0.50 7.13 7.36 7.57 7.73 7.86 7.95 1.0 2.0 2.00 0.50 7.47 7.64 7.79 7.88 7.93 7.94 1.0 5.0 3.50 0.29 7.91 8.12 8.31 8.44 8.56 8.61 1.0 5.0 3.50 0.29 8.26 8.32 8.52 8.60 8.61 8.61 2.0 0.0 1.00 2.00 6.50 6.82 7.11 7.35 7.57 7.73 2.0 0.0 1.00 2.00 6.73 6.98 7.20 7.39 7.53 7.63 2.0 0.2 1.20 1.67 6.59 6.90 7.16 7.40 7.59 7.74 2.0 0.2 1.20 1.67 6.85 7.08 7.30 7.46 7.59 7.68 2.0 0.5 1.50 1.33 6.69 6.98 7.23 7.45 7.63 7.76 2.0 0.5 1.50 1.33 6.98 7.20 7.39 7.55 7.66 7.72 2.0 1.0 2.00 1.00 6.84 7.10 7.34 7.54 7.70 7.82 2.0 1.0 2.00 1.00 7.15 7.36 7.53 7.67 7.76 7.80 2.0 2.0 3.00 0.67 7.11 7.35 7.57 7.74 7.89 7.99 2.0 2.0 3.00 0.67 7.45 7.63 7.78 7.90 7.96 7.98 2.0 5.0 6.00 0.33 7.81 8.01 8.21 8.35 8.47 8.53 2.0 5.0 6.00 0.33 8.16 8.27 8.43 8.50 8.53 8.53 3.0 0.0 1.00 3.00 7.03 7.40 7.72 7.98 8.24 8.43 3.0 0.0 1.00 3.00 7.16 7.45 7.69 7.91 8.08 8.21 3.0 0.2 1.30 2.31 6.94 7.27 7.56 7.81 8.03 8.21 3.0 0.2 1.30 2.31 7.13 7.40 7.62 7.81 7.96 8.07 3.0 0.5 1.75 1.71 6.88 7.18 7.45 7.68 7.88 8.03 3.0 0.5 1.75 1.71 7.15 7.37 7.58 7.75 7.88 7.96 3.0 1.0 2.50 1.20 6.91 7.18 7.43 7.63 7.81 7.94 3.0 1.0 2.50 1.20 7.21 7.42 7.61 7.75 7.86 7.91 3.0 2.0 4.00 0.75 7.10 7.35 7.57 7.75 7.90 8.00 3.0 2.0 4.00 0.75 7.43 7.62 7.78 7.90 7.97 7.99 3.0 5.0 8.50 0.35 7.76 7.97 8.16 8.31 8.43 8.49 3.0 5.0 8.50 0.35 8.13 8.23 8.38 8.46 8.49 8.49 4.0 0.0 1.00 4.00 7.55 7.94 8.30 8.58 8.88 9.10 4.0 0.0 1.00 4.00 7.56 7.87 8.15 8.38 8.58 8.73 4.0 0.2 1.40 2.86 7.23 7.58 7.89 8.16 8.40 8.59 4.0 0.2 1.40 2.86 7.38 7.64 7.89 8.09 8.26 8.39 4.0 0.5 2.00 2.00 7.02 7.34 7.62 7.86 8.07 8.23 4.0 0.5 2.00 2.00 7.26 7.50 7.71 7.89 8.03 8.13 4.0 1.0 3.00 1.33 6.95 7.23 7.49 7.70 7.88 8.01 4.0 1.0 3.00 1.33 7.25 7.46 7.65 7.80 7.92 7.98 4.0 2.0 5.00 0.80 7.09 7.34 7.56 7.75 7.90 8.00 4.0 2.0 5.00 0.80 7.44 7.61 7.77 7.89 7.97 8.00 4.0 5.0 11.00 0.36 7.72 7.94 8.13 8.29 8.41 8.47 4.0 5.0 11.00 0.36 8.09 8.19 8.36 8.44 8.47 8.47 5.0 0.0 1.00 5.00 8.05 8.48 8.86 9.19 9.48 9.74 5.0 0.0 1.00 5.00 7.94 8.27 8.57 8.83 9.05 9.23 5.0 0.2 1.50 3.33 7.46 7.83 8.16 8.44 8.69 8.90 5.0 0.2 1.50 3.33 7.56 7.85 8.10 8.32 8.50 8.64 5.0 0.5 2.25 2.22 7.13 7.45 7.74 7.99 8.20 8.37 5.0 0.5 2.25 2.22 7.34 7.59 7.81 8.00 8.15 8.25 5.0 1.0 3.50 1.43 6.99 7.27 7.53 7.74 7.93 8.07 5.0 1.0 3.50 1.43 7.27 7.49 7.68 7.84 7.96 8.02 5.0 2.0 6.00 0.83 7.09 7.34 7.56 7.75 7.91 8.01 5.0 2.0 6.00 0.83 7.43 7.60 7.77 7.89 7.97 8.00 5.0 5.0 13.50 0.37 7.70 7.93 8.12 8.27 8.40 8.46 5.0 5.0 13.50 0.37 8.07 8.18 8.35 8.43 8.46 8.46 Commentaries to Recommended Practice for Site Specific Assessment of Page 104 Mobile Jack-Up Units Rev 3, August 2008 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 105 Mobile Jack-Up Units Rev 3, August 2008 C6.2.3 Penetration Analysis For Silica Sands Various bearing capacity and shape factors are given in the literature for the analysis of bearing capacity in silica sand. The method described in the PRACTICE text is that of Vesic [8]. However, of particular relevance is the method proposed by Brinch Hansen [17] which is also in common use particularly where the angle of internal friction has been determined for plane strain conditions. FV = A (0.5 γ' B Nγdγsγ + po' Nq sq dq) where; Nγ = 1.5(Nq - 1) tanφ Nq = eπtanφ tan2 (45° + φ/2) dγ = 1 sq = 1 + B/L sinφ sγ = (1 - 0.4B/L) dq = 1 + 2tanφ (1 - sinφ)2 D/B and the maximum preload, VLo, is equal to the ultimate vertical bearing capacity, FV, taking into account the effect of backflow, Fo'A, and the effective weight of the soil replaced by the spudcan, γ'V, i.e.: VLo = FV - Fo'A + γ'V Empirical bearing capacity factors show reasonable agreement with model footings of less than 2.0 metros diameter. However, significant disagreement has been observed in centrifuge tests on larger size spudcans and for actual jack-up rig footings in the North Sea for which the footing diameters ranged from 3.0 to 15.0 m, and laboratory triaxial φ values for the sand indicated φ values in the range of 30° to 40°. Observed penetrations were significantly larger than the φ values would indicate for both the Vesic and Brinch Hansen methods. Analyses by various researchers (Graham, [18]; James, [19]; Kimura, [20]) suggest that reduced φ values be used to account for these "scale effects". In view of these observations it is recommended that laboratory triaxial φ test values should be reduced by 5° for the prediction of large diameter footing penetrations in silica sands, i.e. φdesign = φtriaxial - 5° If laboratory test data are unavailable the following design φ values may be applicable: DESIGN PARAMETERS FOR COHESIONLESS SILICEOUS SOIL* Density Soil Description φ°des. Nγ Nq Very Loose Sand 15 2.6 3.9 Loose Sand-Silt Medium Silt Loose Sand 20 5.4 6.4 Medium Sand-Silt Dense Silt Medium Sand 25 11 11 Dense Sand-Silt Dense Sand 30 22 18 Very Dense Sand-Silt Dense Gravel 35 48 33 Very Dense Sand See notes overleaf COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 106 Mobile Jack-Up Units Rev 3, August 2008 NOTE: "Sand-Silt" includes those soils with significant fractions of both sand and silt. Strength values generally increase with increasing sand fractions. For spudcans on sand the effects of cyclic loading may be to either increase or decrease the pore water pressure. Positive excess pore water pressure will weaken the soil and in severe cases may cause partial fluidization. Negative excess pore water pressures may temporarily strengthen the soil. Approximate methods are available for the assessment of excess pore water pressure development and associated foundation settlement (Dean [20]). The following qualifications apply: 1. Footing penetrations in a thick layer of clean silica sand are usually minimal with the maximum diameter of the spudcan rarely coming into contact with the soil. It is therefore not usual to consider the effects of soil backflow in this situation. 2. If various sand layers occur to 1.5 B below the footing depth an average value for φ' can be selected using the graph developed by Meyerhof [22] as shown in Figure C6.4. Considering the overall inaccuracy in the prediction of footing penetration in sand, this refinement does not generally influence the accuracy of the prediction. 3. Emphasis should be placed on the identification and analyses of potential punchthroughs into a clay layer (or a silt layer which may behave undrained). Figure C6.4 : Depth of failure zone in sand COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 107 Mobile Jack-Up Units Rev 3, August 2008 C6.2.4 Penetration Analysis For Carbonate Sands Relatively large footing penetrations have been reported for uncemented carbonate materials despite high laboratory friction angles (Dutt, [23]). This may be attributed to either the high compressibility of these materials or low shear strengths due to high voids ratio and a collapsible structure. The leg penetration is governed by both strength and deformation characteristics of foundation soils as noted in Commentary 6.2.1. The compressibility of carbonate sands is relatively higher than for silica sands. Hence, greater penetrations should be expected for carbonate sands relative to silica sands despite the similar or even higher laboratory friction angles. This is supported by both experimental (Poulos, [24]) and theoretical (Yeung, [25]) studies on model foundations. The predictions of footing penetrations in carbonate sands are likely to be performed to a lower degree of accuracy compared with those for silica sands. The conventional method is to use the plasticity based formulation for bearing capacity of shallow foundations in sand. However, friction angles to be used in the formulae should be considerably smaller than laboratory values to account (in an artificial manner) for the soil behavior. C6.2.5 Penetration in Silts Cyclic loads imposed in silty fine sands/silt foundations may cause liquefaction due to the generation of excess pore water pressures. In this situation foundation settlements would be anticipated. Conservative assessments of reduced bearing capacities and increased settlements should be conducted as appropriate. C6.2.6 Penetration Analysis For Layered Soils C6.2.6.1 Squeezing of Clay For a squeezing clay layer the resistance on the footing cannot become larger than the resistance of the layer underneath the soft clay layer. Thus there is a limit to the squeezing process. C6.2.6.3 Punch-through: Dense Sand Over Soft Clay Traditionally the bearing capacity of a footing on a thin sand layer overlying soft clay has been computed according to the method developed by Hanna and Meyerhof [26] as described in the PRACTICE. This method appears to provide reasonable predictions of the ultimate resistance at the onset of punch-through, however it may overpredict the resistance after the initiation of punch-through as the soil shear planes then approach the vertical and the assumed modeling is then incorrect. The approximation Kstanφ ≈ 3cu/Bγ' is a lower bound applicable to the onset of punch-through. The reference paper provides more accurate data for Ks. An alternative method is that in which a load spread is considered through the upper sand layer, as illustrated in Figure C6.5. In this model the bearing capacity of the foundation is assumed to be equal to the bearing capacity of the foundation projected onto the lower layer. This method allows capacity ranges to be developed for a range of load spread gradients. Thus for a load spreading under a slope of 1:n, the ultimate bearing capacity of a circular foundation is given by: COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 108 Mobile Jack-Up Units Rev 3, August 2008 FV = FV,b - W where; FV = ultimate bearing capacity of footing (with diameter B and area A at depth D). FV,b = ultimate bearing capacity of fictitious footing (with diameter [B + 2H/n] and area (1 + 2H/nB)2A, at the top of the soft clay layer. W = weight of soil "plug" in between footing and fictitious footing. = [1 + 2H/(nB)]2AHγ' Figure C6.5 : Spudcan bearing capacity analysis - sand over clay - load spread method This method, using n = 3, has been recommended by Young, [27] for jack-up foundations. However, comparison with model test data (Jacobsen, [28]; Higham, [29]; Craig, [30]) suggest a range from n = 3 to 5. Conversely, actual spudcan penetration data are available which suggest a higher spread, i.e. smaller n values, (Baglioni, [31]). Hence it is suggested that this method would provide reasonable, but conservative, results if a lower bound value n = 5 be used. However, it is noted that both observations of model test data and results of numerical analyses reveal that soil punching failure occurs along vertical surfaces. Thus, although this method can provide reasonable quantitative estimates on leg penetration, it may not be based on a physically correct model. The same comment applies to the previously referenced Hanna and Meyerhof method which is based on failure along a truncated cone surface. This is unlike the observed vertical shear surface. However, the ultimate resistance computed when punching shear is initiated generally gives reasonable agreement (and is acceptably conservative) compared with actually observed data. It is noted that this method generally provides reasonable estimates of ultimate soil resistance at the onset of punch-through. However, significant underpredictions of soil resistance have been reported by Baglioni, [31]. Conversely the method appears to overpredict soil resistance after punch-through has initiated as suggested by Craig, [32]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 109 Mobile Jack-Up Units Rev 3, August 2008 Craig, [30] observed in centrifuge model tests that a sand plug underneath the spudcan is pushed with relatively little lateral deformation into the underlying clay for prototype offshore conditions. It is suggested that account be taken of the frictional resistance on this sand plug when penetrating the clay. C6.2.7 Summary The various soil failure mechanisms considered in this section are illustrated in Figure C6.6. The current status on analytical methods for punch-through (Section C6.2.6) is that the widely used methods, discussed above, (i.e. the load spread method and the Hanna and Meyerhof method) show (different) discrepancies with observed data. However, both methods allow prediction of a lower bound resistance at the initiation of punch-through. Figure C6.6 : Foundation bearing failure modes COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 110 Mobile Jack-Up Units Rev 3, August 2008 C6.3 FOUNDATION STABILITY ASSESSMENT C6.3.3/4 Bearing capacity for inclined loading Introduction Formulae for combined vertical (FVH, FVHM), horizontal (FH, FHM) and moment (FM) capacity on shallow foundations in uniform soils have been suggested by various researchers. Those due to Vesic [8] and Brinch Hansen [17] are commonly used for offshore applications and are included in API RP2A [33] and DNV [34] guidelines respectively. It should be noted that the equations are applicable to shallow penetrations. Any contribution of horizontal soil resistance on the embedded legs is ignored. In case of deep penetrations the horizontal resistance may be significant, especially when the jack-up leg comprises a single tubular or box section or when the spudcan is provided with skirts around the can perimeter. The following section is an overview of the recommended criteria for spudcan foundations. It is noted that the analytical procedures apply to a flat footing in which all load/resistance is transmitted through its base. The influence of horizontal resistance on vertical areas (e.g. footing cone or vertical surfaces above the base) can either be assessed separately or ignored. Reasons for discluding the latter resistance component are discussed below. 1. Uncertainty of the contact area between the spudcan and soil due to the shape of the foundations or due to removal of foundation material by scour. 2. Soil strengths and stiffnesses may be significantly reduced as a result of material remolding during unit installation. 3. The ultimate shear resistance along the foundation base is generally mobilized at a significantly smaller displacement than that required to mobilize the passive soil resistance. It is noted that the combined loading problem is generally solved in a simplistic and generally conservative manner. For layered soil conditions and/or complex footing configurations it may be helpful to assess the ultimate foundation capacity using finite element techniques. Such analyses are particularly relevant for the assessment of displacements associated with combined loads (level 3 analyses). The equations of Sections 6.3.3.1 and 6.3.3.2 may be used to calculate the bearing capacity of the soil beneath the spudcan under inclined loading. The expressions provide correlation between the vertical soil bearing capacity the associated horizontal soil bearing capacity. In this case the effect of backflow and spudcan buoyancy shall be included in the spudcan loading. The total vertical load during storm conditions may comprise: - dead, live and environmental loads including associated P-Δ effects - backflow - spudcan buoyancy (due to weight of soil displaced by the spudcan) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 111 Mobile Jack-Up Units Rev 3, August 2008 Uniform Clay Clay pinned foundation (FM = 0): A comparison of the Vesic [8] and Brinch Hansen [17] criteria for surface footings in clay shows that the latter are slightly more conservative than the former (i.e. the Brinch Hansen results show a reduced capacity compared with those given by the Vesic approach). The Brinch Hansen criteria appear to provide a lower bound to finite element analysis results and (model) test data reported by Noble Denton [10b] and by Santa Maria [35]. The relationship between maximum vertical capacity (FVH) and horizontal soil capacity (FH) for a circular surface footing in clay is graphically presented in Figure C6.7. The graph has been non-dimensionalized by dividing FVH and FH by the maximum vertical soil capacity FVmax (which occurs when FH = 0). Also shown is a curve for deep footings where D/B≥2.5. For spudcans founded on overconsolidated clay (OCR ≥ 4), cyclic degradation may reduce the horizontal bearing capacity by a factor of 0.3, i.e. the horizontal bearing capacity calculated from static soils properties should be multiplied by a reduction factor: Horizontal bearing capacity reduction factor = 0.7 For these materials the horizontal and vertical soil stiffnesses calculated from static soil properties may be multiplied by factors of 1.25 and 3 to 8 as a result of cyclic effects (Anderson [36]). Figure C6.7 : Vertical/horizontal load envelopes for footings in clay COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 112 Mobile Jack-Up Units Rev 3, August 2008 Clay foundation with moment fixity (FM > 0): The FVH-FH envelope reduces in size if an overturning moment is applied in addition to horizontal and/or vertical loading. Reference is made to Brinch Hansen [17] or to DNV [34]. Some guidance can also be obtained from Santa Maria [35]. Uniform Sand Pinned sand foundation (FM = 0): Figure C6.8 shows a comparison of Vesic, [8] (=API RP2A, [33]) and Brinch Hansen, [17] (= DNV, [34]) criteria for surface footings on sand with test results reported by Noble Denton [10b]. These data suggest that the Vesic criteria provide a reasonable lower bound to the test data for FH/FVH ratios less than 0.3. (It is noted that Tan [39] reported tests results and analysis data which indicate higher soil resistances than those due to Vesic and Brinch Hansen.) The relations between FVH/FVmax and FH/FVmax for a circular surface footing and for a deep footing in sand are graphically presented in Figure C6.9. The graph for surface footings can be used to make a lower bound estimate of FVH-FH relations at any depth. Based on the above studies it is recommended to adopt the Vesic criteria for spudcan analysis in sands. Sand foundation with moment fixity (FM > 0): The FVH-FH envelope reduces in size if an overturning moment is simultaneously applied. Reference is made to Vesic [8] and API RP2A [33] for details on the computation procedure. Further guidance can be obtained from Tan [39]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 113 Mobile Jack-Up Units Rev 3, August 2008 Figure C6.8 : Foundation combined vertical/horizontal loading on sand - comparison of design criteria and observed data Figure C6.9 : Vertical/horizontal load envelopes for footings in sand COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 114 Mobile Jack-Up Units Rev 3, August 2008 Clay & Sand Foundations with moment fixity (FM > 0) Section 6.3.4.6 describes three methods by which fixity may be included in the analysis. The intermediate method, using linear fixity, is an approach that was not previously encompassed. It is now included as the more detailed methods are not readily available to most analysts. It must however be noted that the linear rotational stiffness must be selected with care to ensure that wave force cancellation effects do not drive the resulting DAF’s. Refer to C7.4. Elastic Spring Stiffnesses - Sand and Clay The elastic stiffness factors are calculated assuming full contact of the spudcan with the seabed. If the vertical load is insufficient to maintain full contact as the moment increases then reduced stiffnesses should be used. The stiffness factors are derived for a homogeneous, linear, isotropic soil. Choice of the appropriate shear modulus should take into account the expected stress level and strain amplitude. In general, the shear modulus decreases with increasing strain amplitude. Selection of Shear Modulus, G, in clay The value of the initial, small-strain shear modulus for clay should be based on the value of the shear strength (cu) measured at the depth z =D+0.15B where B is the diameter of the spudcan and D is the depth below mudline of the lowest point on the spudcan at which this diameter is attained. Where the clay is significantly layered the average strength within the range z = D to z = D + 0.3B should be used. Except in areas with carbonate clays or clayey silts the shear modulus should be calculated as [ref. 53]: G = 0.25 600 OCR cu with G < CuIrNC and subject to the limitations given below. Where; OCR = The overconsolidation ratio; IrNC = The Rigidity Index for Normally Consolidated clay.. For extreme loading conditions and in the absence of other data IrNC shall be conservatively limited to 400 (Noble Denton, [53]) based on overconsolidated clay sites with Plasticity Indices (Ip) of up to 40%; the data for normally consolidated clay published by Andersen in Figure 10.2 of [55], reproduced as Figure C6.10 below, supports the use of IrNC of 400 up to about Ip = 60% if, as suggested by Andersen in correspondence, the low points at Ip of around 50% are given less weight as they fall outside the main trend. Due consideration should be given to the possibility of determining site-specific shear moduli for normally consolidated and slightly overconsolidated clays and/or where the Plasticity Indices exceed 60%. IrNC = 600 for clays with low OCR and Ip less than about 40% is supported by field data for jack-up response in the Gulf of Mexico (Templeton [54]). It should be noted that IrNC appears to be fundamentally inversely proportional to the Plasticity Index (Andersen [55], Figure 10.2, reproduced as Figure C6.10 below). For sites with Plasticity Indices in excess of 60%, and not covered by field data, the analyst should account for the inverse relationship when determining G. In some cases higher ratios of IrNC may be used. The data published by Andersen ([55], Figure 10.2, reproduced as Figure C6.10 below) would support use of COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 115 Mobile Jack-Up Units Rev 3, August 2008 values as high as 1000 or even 2500, particularly for Plasticity Indices less than 20%. These recommendations are intended for use in both site assessments for extreme loading and applications involving small strain beneath the spudcan. In the calculation of fixity for extreme loading, the moment stiffness based on the small strain G values will be degraded using the stiffness reduction formulae given in 6.3.4 of the Practice. In the case of small strain applications, such as in structural fatigue analysis, the stiffness reductions do not apply and it may be appropriate to adopt upper-bound values. Figure C6.10 : Normalised initial shear modulus as a function of Plasticity Index, Ip, for 11 different clays. Figure 10.2 from Anderson [55] Note: On the vertical axis Gmax, the initial shear modulus from shear waves generated by bender elements in direct simple shear (DSS) tests is normalised against Su DSS, the undrained montonic shear strength from the DSS tests. Whilst these parameters may differ from those determined by other means, due to rate effects, etc., the differences are expected to be sufficiently small that the data and trends remain applicable. Note: If it is assumed that Poisson's ratio for clay is 0.5 then, 3 K = 1.5 GB3 and, ignoring other terms and factors: Lo V = c u B N c 4 π 2 where Lo V is the effective seabed vertical reaction under preload. 0 20 40 60 80 100 Plasticity Index, Ip (%) 0 1000 2000 3000 Gmax / suDSS 3 40 4 10 2405 2 2.8 2.8 1.9 1.0 < OCR <1.5 OCR > 1.5. OCR indicated at data point COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 116 Mobile Jack-Up Units Rev 3, August 2008 This simplifies to: K3 = 0.25 1 1.5 4 600 N OCR V B c Lo ⎟ ⎟⎠ ⎞ ⎜ ⎜⎝ ⎛ × π So that the rotational stiffness is directly proportional to the diameter, directly proportional to the preload, and depends weakly on the OCR. The bracketed term is almost a constant factor in the region of about 80. Since full embedment will usually apply, neither preload nor diameter will vary very much for any one unit. In fact the OCR is the only factor that alters the stiffness significantly. Selection of Shear Modulus in Sand For sands the initial, small-strain shear modulus should be computed from: a G p = ( )0.5 swl a j V Ap where j = ⎟⎠ ⎞ ⎜⎝ ⎛ + 500 230 0.9 R D (Dimensionless stiffness factor) a p = Atmospheric pressure DR = Relative Density (percent) Vswl = Seabed vertical reaction under still water conditions. Note: The above gives a p G = 0.5 2 4 500 9 . 0 230 ⎟ ⎟⎠ ⎞ ⎜ ⎜⎝ ⎛ ⎟⎠ ⎞ ⎜⎝ ⎛ + a R swl B p D V π Combining this with 3 K = ( ) 3 1−ν GB3 and Lo V = γ π γ B B N 4 2 2 ′ (for a partially embedded foundation in sand, and also approximately true for the fully embedded case if one ignores the Nq term and depth and shape factors) gives: 3 K = ( ) 2 0.5 0.5 0.5 3 1 500 2 230 0.9 B D p V a swl R −ν π ⎟⎠ ⎞ ⎜⎝ × ⎛ + and B3 = γ πγ N VL ′ 0 8 . Two cases emerge. If there is (rarely) full embedment then the rotational stiffness is proportional to the square of the diameter and the square root of the load - since for any particular unit not much can be done about either, this results in almost constant rotational stiffness in the embedded case. In the partially embedded case we substitute for the diameter and get: 3 K = ( ) 0.67 0.67 0.67 0.67 0.5 0.5 1.17 8 1 1 3 1 500 2 230 0.9 γ ν π V π γ N V D p V swl Lo a swl R ′ ⎟⎠ ⎞ ⎜⎝ ⎛ ⎟ ⎟⎠ ⎞ ⎜ ⎜⎝ ⎛ − ⎟⎠ ⎞ ⎜⎝ × ⎛ + COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 117 Mobile Jack-Up Units Rev 3, August 2008 This shows that the stiffness depends on the vertical load (increasing slightly more than linearly) and reduces with increasing bearing capacity factor. Note that Nγ increases much more rapidly than DR as relative density increases. The rather surprising effect of density is due to the reduced penetration and hence reduced effective diameter. In the limit an infinitely strong soil would result in point contact, and no rotational stiffness! None of the other factors in the above equation vary much. Therefore weaker soils (NC rather than OC clays, loose rather than dense sands) in each case result in, paradoxically, higher rotational stiffnesses. Effect of Embedment of the Spudcan on the Elastic Spring Stiffness A study of the effect of embedment of flat plate and conical type footings has been performed by Bell [42] to demonstrate the effect of penetration depth on the translational and rotational spring stiffnesses. In order to take the embedment into account the spring stiffness derived from the elastic solutions may be multiplied by the depth factor Kd. The results of the study are summarized in the tables below for Poisson’s ratios of 0.0, 0.2, 0.4 and 0.5. In the tables Kd1, Kd2 and Kd3 represent the depth factors for the vertical spring stiffness, horizontal spring stiffness and the rotational spring stiffness, respectively. Case 1 represents an open hole above the spudcan, case 2 a back-filled hole. Stiffness factors for ν=0.0 Kd1 Kd2 Kd3 D/R Case 1 Case 2 Case 1 Case 2 Case 1 Case 2 0.5 1.15 1.21 1.33 1.49 1.28 1.64 1.0 1.28 1.41 1.44 1.71 1.43 2.05 2.0 1.42 1.70 1.51 1.92 1.51 2.31 4.0 1.59 2.00 1.61 2.06 1.57 2.41 Stiffness factors for ν=0.2 Kd1 Kd2 Kd3 D/R Case 1 Case 2 Case 1 Case 2 Case 1 Case 2 0.5 1.11 1.18 1.32 1.47 1.23 1.54 1.0 1.21 1.34 1.42 1.67 1.37 1.90 2.0 1.34 1.59 1.48 1.85 1.44 2.15 4.0 1.49 1.85 1.58 1.98 1.51 2.25 Stiffness factors for ν=0.4 Kd1 Kd2 Kd3 D/R Case 1 Case 2 Case 1 Case 2 Case 1 Case 2 0.5 1.08 1.14 1.31 1.45 1.18 1.43 1.0 1.16 1.27 1.41 1.64 1.31 1.76 2.0 1.27 1.48 1.48 1.80 1.39 2.01 4.0 1.41 1.72 1.57 1.92 1.47 2.13 Stiffness factors for ν=0.5 Kd1 Kd2 Kd3 D/R Case 1 Case 2 Case 1 Case 2 Case 1 Case 2 0.5 1.07 1.10 1.32 1.44 1.18 1.39 1.0 1.15 1.23 1.44 1.62 1.31 1.71 2.0 1.25 1.44 1.51 1.78 1.40 1.99 4.0 1.40 1.69 1.59 1.91 1.51 2.16 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 118 Mobile Jack-Up Units Rev 3, August 2008 Avoidance of numerical problems An analysis in which the spudcan is considered as pinned to the seabed is equivalent to the assumption that K1 and K2 are infinite and K3 is zero. In any analysis taking into account foundation fixity (K3 non-zero) it is recommended that the effects of K1 and K2 are considered, as they will tend to decrease the sway stiffness, and hence increase the natural period and second order effects. As a first approximation elastic springs are recommended. In some instances the vertical deformations resulting from the inclusion of such springs may be large, and could compromise the numerical accuracy of the solution. A possible method of reducing the absolute value of the deflections is given below. Figure C6.11: Vertical load-displacement curves for leeward and windward legs With reference to Figure C6.11, consider the windward and leeward legs as follows: Leeward leg Windward leg Vmax = VD + VE Vmin = VD - VE where; VD = Vertical reaction due to dead load VE = Vertical reaction due to environmental load (and any change from the variable load level used in computing VD) The deflection due to environmental load alone Δd can be derived as: Δd = V V K V K D v v max max − = Δd = V V K V K D v v − min = min The modified vertical spring stiffness K*v is then: K*v = Kv V V VD max max − K*v = Kv V V V D min min − K*v = Kv V V V D E E + K*v = Kv V V V D E E − where; Kv = K1 from the PRACTICE = 2GD/(1-ν) For further information regarding foundation stiffness evaluation reference should be made to Bell, [44]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 119 Mobile Jack-Up Units Rev 3, August 2008 C6.4 OTHER ASPECTS OF JACK-UP UNIT FOUNDATION PERFORMANCE C6.4.1 Leaning Instability A lower bound estimate of the leaning stability can be performed using the theory of Hambly [45]. However, it should be recognized that such estimates have proven to be generally conservative due to the omission of beneficial effects such as spudcan fixity and lateral soil resistance on the legs. The potential for jack-up unit leaning instability may largely be discounted if appropriate installation procedures are adopted. C6.4.2 Footprint Considerations Installing a jack-up with its spudcans near or adjacent to existing footprints, or zones of weaker material (naturally infilled spudcan footprints) may induce soil failure. Mathematical models are available for the evaluation of ground stability in such situations and, in particular, finite element techniques are becoming more widely used. It is not possible to advise on a minimum acceptable distance between the proposed spudcan locations and existing footprints as this will depend on several parameters. These parameters include the soil conditions, the depth and configuration of the footprints, the degree of soil backfill during and after spudcan removal, the elapsed time since the last installation, the spudcan geometry and foundation loading. As a general guideline it is usually acceptable for a spudcan to be installed at a minimum distance (from the edge of the bearing area to the edge of the footprint) of one diameter measured at the spudcan bearing area. However, in soft clay conditions, with consequentially deep footing penetrations, the situation may be complicated by the fact that the footprints may have larger diameters than the spudcans. Also in dense sand or stiff clay conditions, where shallow footprints are unlikely to influence the integrity of the spudcan foundations, the above guideline may be conservative. C6.4.3 Scour The seabed is susceptible to scour when the shear stresses induced by fluid flow exceed a certain value and/or when turbulent intensity of the flow is sufficiently large to lift individual grains and entrain these in the flow. Both wave action and currents can induce scour although in deep water, the effect of wave action on seabed scour is negligible. The following parameters are important for the assessment of scour potential: a) Seabed material - size, shape, density and cohesion b) Flow conditions - current velocity, wave-induced oscillatory velocities interaction of waves and currents c) Shape, size and penetration of jack-up footing. Methods are available to determine whether significant scour is likely under waves and currents. These generally proceed by considering the velocities near the seabed and by calculation of the shear stresses. Guidance is given with regard to the assessment of scour potential in the US NCEL [46] Marine Geotechnical Engineering Handbook. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 120 Mobile Jack-Up Units Rev 3, August 2008 C6.4.4 Seafloor instability Seafloor instability may be caused by a number of mechanisms and where the potential for unstable ground conditions is recognized it is recommended that expert local advise is obtained. In areas where liquefaction is known to be possible its potential must be assessed. Liquefaction, or cyclic mobility, occurs when the cyclic stresses within the soils cause a progressive build up of pore pressure. The pore pressure within the profile may build up to a stage where it becomes equal to the initial average vertical effective stress. Foundation failure may result depending on the location and extent of pore pressure developed in the soil. The rate and degree of pore pressure build up will depend on three factors: a) The loading characteristics; that is, the amplitude, period and durations of the different cyclic loading components b) The cyclic characteristics of the soil deposits c) The drainage and compressibility of the strata comprising the soil profile. The cyclic loads may be induced by environmental or mechanical means, or by the oscillatory ground accelerations imposed during earthquake conditions. If appropriate soil conditions prevail, the potential for cyclic mobility should be considered for a wide variety of load cases. Of particular interest is the windward footing during storm conditions, where reduced vertical load and increased horizontal load may theoretically induce lateral sliding or bearing failure. C6.4.6 Spudcan - pile interaction Where it is recognized that jack-up footings may adversely effect the piles of an adjacent structure it will be necessary to assess the implications. Procedures such as that proposed by Siciliano [47] may be used for deeply embedded footings in clay. Otherwise, if adequate soil data is available, mathematical modeling techniques, such as finite element modeling, could be used to assess the significance of the spudcan-pile interaction. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 121 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C6 au = Adhesion. A = Spudcan effective bearing area. B = Effective spudcan diameter at uppermost part of bearing area in contact with the soil (for rectangular footing B = width). B' = Increased effective spudcan diameter - load spread method. cu = Undrained cohesive shear strength. cul = Undrained cohesive shear strength at spudcan tip. cum = Undrained cohesive shear strength at mudline. cuo = Undrained cohesive shear strength at max bearing area. d = Critical depth of failure below spudcan in sand. dq = Bearing capacity factor = 1 + 2tanφ(1- sinφ)2 D/B. dγ = Bearing capacity factor = 1. D = Distance from mudline to spudcan maximum bearing area. DR = Relative Density (percent). e = Voids ratio. e(e) = Voids ratio factor. f(eL) = Voids ratio factor for loose sand. f(eD) = Voids ratio factor for dense sand. FH = Horizontal foundation capacity (envelope). FM = Foundation moment capacity (envelope). Fo' = Effective overburden pressure due to backfill at depth of the uppermost part of the bearing area. FV = Vertical foundation capacity. FV,b = Vertical bearing capacity of fictitious footing on the surface of the lower (bottom) clay layer with no backfill. FVH = Vertical foundation capacity when horizontal load is present. FVmax = Maximum vertical soil resistance (occurs when FH = 0). G = Shear modulus. GLoose = Shear modulus for loose sand. GDense = Shear modulus for dense sand. H = Distance from spudcan maximum bearing area to weak strata below. Ir = Coefficient relating undrained shear strength to shear modulus. I = Height of soil column above spudcan. j = Dimensionless stiffness factor for sand. ks = Coefficient of punching shear. kv = Vertical foundation stiffness (= K1). K1,K2,K3 = Vertical, horizontal and rotational stiffness. Kd1 = Stiffness factor on vertical stiffness to account for embedment. Kd2 = Stiffness factor on horizontal stiffness to account for embedment. Kd3 = Stiffness factor on rotational stiffness to account for embedment. K*v = Modified vertical foundation stiffness. L = Foundation length, for circular foundation L = B. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 122 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C6 (Continued) n = Inverse slope of load spreading (slope of spread = 1:n). N = Stability factor. NC = Bearing capacity factor (taken as 5.14). NC' = Alternative bearing capacity factor for normally consolidated clays. Nq = Bearing capacity factor = eπtanφtan2(45 + φ/2). Nγ = Bearing capacity factor = 2(Nq + 1) tanφ for Vesic analysis [8] = 1.5(Nq - 1) tanφ for Brinch Hansen analysis [17]. OCR = Over consolidation ratio. pa = Atmospheric pressure. po' = Effective overburden pressure at spudcan base level (i.e. depth of maximum bearing area). QV = Factored vertical leg reaction. QH = Factored horizontal leg reaction. R = B/2. sq = Bearing capacity shape factor = 1 + (B/L)tanφ. sγ = Bearing capacity shape factor = (1 - 0.4B/L). ( = 0.6 for circular footing under pure vertical load). T = Thickness of weak clay layer underneath spudcan. V = Embedded spudcan volume. VD = Vertical reaction due to dead load. VE = Vertical reaction due to environmental load (and any change from the variable load level used in computing VD). VLo = Maximum vertical foundation load during preloading. Vmax = Maximum footing reaction on leeward leg. Vmin = Minimum footing reaction on windward leg. Vswl = Seabed vertical reaction under still water conditions. W = Weight of soil plug (load spread method) = [1 + 2H/(nB)]2AHγ'. z = Vertical foundation settlement for conventional bearing capacity analysis. zu = Vertical displacement required to mobilize capacity FV. α = Roughness factor = au/cu. β = The equivalent cone angle of the spudcan. Δd = Vertical deflection due to environmental load. γ' = Submerged unit weight of soil. φ = Angle of internal friction for sand - degrees. φ' = Angle of internal friction for sand - degrees, dependent on d/B ratio. ν = Poisson's ratio. ρ = Rate of increase of cohesive shear strength with depth. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 123 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C6 1 Meyerhof G.G. (1972), "Stability of Slurry Trench Cuts in Saturated Clay", Proceedings of the Speciality Conference on Performance of Earth and Earth Supported Structures, ASCE, pp. 1451-1466. 2 Britto A.M., Kusakabe, Osanu (1983) "Stability of Axisymmetric Excavations in Clays", Journal of Geotechnical Eng., Vol 109, No. 5. 3 Young A.G., Remmes B.D., Meyer B.J., (1984) "Foundation Performance of Offshore Jack-Up Drilling Rigs" Journal of Geotechnical Engineering, Vol. 110, No. 7, pp. 841- 859. 4 Skempton A.W. (1951), "The Bearing Capacity of Clays", Building Research Congress. 5 Davis E.H., Booker J.R., (1973), "The Effect of Increasing Strength with Depth on the Bearing Capacity of Clays", Geotechnique Vol. 23, No. 4, pp. 551-563. 6 Salencon J., Matar M., (1982), "Capacite portante des Foundations superficielles circulaires", Journal de Mecanique theorique et applique, Vol. 1, No. 2, pp. 237-267. 7 Houlsby G.T., Wroth C.P., (1983), "Calculation of Stresses on Shallow Penetrometers and Footings", Proc. IUTAM Symp. on Seabed Mechanics, Newcastle, pp. 107-112. 8 Vesic A.S., (1975), "Bearing Capacity of Shallow Foundations", Foundation Engineering Handbook (H.F. Winterkorn and H.Y. Fang, eds.), 121-147, Van Nostrand. 9 Endley, S.N., Rapoport, V., Thompson, P.J., and Baglioni, V.P. (1981), "Prediction of Jack-up rig Footing Penetration", OTC, Houston, OTC 4144. 10a Noble Denton & Associates (1987), "Foundation Fixity of Jack-up Units, Joint Industry Study", Volumes I, II. 10b Noble Denton & Associates (1988), "Foundation Fixity of Jack-up Units, Joint Industry Study, Extra work", Volume III. 11 Houlsby G.T., Wroth C.P., (1982), "Determination of undrained strengths by cone penetration tests", Proceedings of the Second European Symposium on Penetration Testing / Amsterdam. 12 Houlsby G.T., Wroth C.P., (1982), "Direct Solution of Plasticity Problems in Soils by the Method of Characteristics", Proceedings of the Fourth International Conference on Numerical Methods in Geomechanics, Edmonton, Canada. 13 Houlsby G.T., (1982), "Theoretical Analysis of the Fall Cone Test" Geotechnique 32, No. 2, 111-118. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 124 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C6 (continued) 14 Koumoto T., Kaku K. (1982), "Three-Dimensional Analysis of Static Cone Penetration" Proceedings of the Second European Symposium on Penetration Testing, Amsterdam. 15 Houlsby G.T. (1991), "Bearing Capacity Factors for Conical Footings on Clay - Comments on Derivation of Factors", presented to Jack-Up Working Group Foundations Sub-Committee, London. 16 Andersen K.H. (1988), "A Review of Soft Clay under Static and Cyclic Loading", Invited lecture, International Conference on Engineering Problems of Regional Soils, Being, China. 17 Brinch Hansen J., (1970) "A Revised and Extended Formula for Bearing Capacity", Bulletin No. 28, Danish Geotechnical Inst., Copenhagen. 18 Graham J., Stuart J.G. (1971), "Scale and Boundary Effects in Foundation Analysis", Journal of the Soil Mechanics and Foundation Division, ASCE, Vol. 97, No. SM11, November, pp. 1533-1548. 19 James R.G., Tanaka H. (1984), "An Investigation of the Bearing Capacity of footings under Eccentric and Inclined Loading in Sand in a Geotechnical Centrifuge", Proc. Symp. Recent Advances in Geotechnical Centrifuge Modelling, University of California, Davis, pp. 88-115. 20 Kimura T., Kusakabe O., and Saitoh K. (1985), "Geotechnical Model Tests of Bearing Capacity Problems in Centrifuge", Geotechnique, Vol. 35, No. 1, pp. 33-45. 21 Dean E.T.R. (1991), "Some Potential Approximate Methods for the Preliminary Estimation of Excess Pore Water Pressures and Settlement-Time Curves for Submerged Foundations subjected to Time Dependent Loading", Cambridge University Engineering Department, CUED/D-Soils/TR240. 22 Meyerhof G.G. (1984), "An Investigation of the Bearing Capacity of Shallow Footings on Dry Sand", Proceedings 2nd ICSMFE, Rotterdam. 23 Dutt R.N., Ingram W.R. (1988), "Bearing Capacity of Jack-up Footings in Carbonate granular Sediments", Proceedings of the International Conference on Calcareous Sediments, Perth, pp. 291-296. 24 Poulos H.G., Chua E.W. (1985), "Bearing Capacity of Foundations on Calcareous Sand", Proceedings 11th ICSMFE, San Francisco, Vol. 3, pp. 1619- 1622. 25 Yeung S.K., Carter J.P. (1989), "An Assessment of the Bearing Capacity of Calcareous and Silica Sands", International Journal for Numerical and Analytical Methods in Geomechanics, Vol. 13, pp. 19-26. 26 Hanna A.M., Meyerhof G.G. (1980), "Design Charts for Ultimate Bearing Capacity of Foundations on Sand Overlying Soft Clay", Canadian Geotechnical Journal Vol. 17. 27 Young A.G., Focht J.A. Jr. (1981), "Subsurface Hazards Affect Mobile Jack-up Rig Operations", Sounding, McClelland Engineers Inc., Houston, Texas, Vol. 3, No. 2, pp. 4-9. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 125 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C6 (Continued) 28 Jacobsen M., Christensen K.V., Sorensen C.S. (1977), "Gennemlokning of Tynde Sandlag (Penetration of Thin Sand Layers)", Vag-och Vattenbyggaren 8-9, Sweden. 29 Higham M.D. (1984), "Models of Jack-up Rig Foundations:", M.Sc. Thesis, University of Manchester. 30 Craig W.H., Chua K. (1990), "Deep Penetration of Spudcan Foundations on Sand and Clay", Geotechnique, Vol. 40, No. 4, pp. 541-556. 31 Baglioni V.P., Chow G.S. Endley S.N. (1982) "Jack-up Rig Foundation Stability in Straified Soil Profiles", Proceedings, 14th OTC, Houston, OTC 4408. 32 Craig W.H., Higham M.D. (1985), "The Applications of Centrifugal Modelling to the Design of Jack-up rig Foundations". Proceedings Offshore Site Investigation Conference, Vol. 3. ISBN 0-86010-668-3. 33 API RP2A (1989), "API Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms", API Recommended Practice 2A (RP2A) 18th Edition, Washington. 34 Det Norske Veritas (1977), "Rules for the Design and Inspection of Offshore Structures, Appendix F, Foundations", H`vik, Reprint with corrections (1980). 35 Santa Maria P.E.L. de (1988), "Behavior of Footings for Offshore Structures under Combined Loads", Ph.D. Thesis, Oxford University. 36 Andersen K.H. (1992), "Cyclic effects on Bearing Capacity and Stiffness for a Jack-up Platform on Clay", NGI Oslo report 913012-1, Rev 1. 37 Brekke J.N., Murff J.D., Lamb W.C. (1989) "Calibration of Jackup Leg Foundation Model Using Full-Scale Structural Measurements", Proceedings Offshore Technology Conference, Houston, (OTC 6127). 38 Matlock H. (1970), "Correlations for Design of Laterally Loaded Piles in Soft Clay", Proceedings Offshore Technology Conference (OTC 1204). 39 Tan F.S.C. (1990), "Centrifuge and Theoretical Modelling of Conical Footings in Sand", Ph.D. Thesis, Cambridge University. 40 Wroth et al. (1979), "A Review of the Engineering Properties of Soils with Particular Reference to the Shear Modulus", Cambridge University Engineering Department. Report No 1523/84./SM049/84. 41 Dean et al. (1992a), "A New Procedure for Assessing Fixity of Spudcans on Sand", Andrew N Schofield and Associates Ltd., Cambridge, for Joint Industry Jack-Up Committee. 42 Dean et al. (1992b), "A New Procedure for Assessing Fixity of Spudcans on Sand - Further Notes", Andrew N Schofield and Associates Ltd., Cambridge, for Joint Industry Jack-Up Committee. 43 Hardin B.O., and Drnevich V.P. (1972), "Shear Modulus and Damping in Soils: Design Equations and Curves", J. Soil Mech. Foundation Division, ASCE Vol 98, SM7, 667- 692 44 Bell R.W. (1991), "The Analysis of Offshore Foundations Subjected to Combined Loading", MSc. Thesis presented to the University of Oxford. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 126 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C6 (Continued) 45 Hambly E.C. (1985), "Punch-through Instability of Jack-up on Seabed", Journal of Geotechn. Eng., ASCE, Vol. 111, No. 4. 46 US NCEL (1985), "Handbook for Marine Geotechnical Engineering". Deep Ocean Technology, Naval Civil Engineering Laboratory, Port Hueneme, CA 93043. 47 Siciliano R.J., Hamilton J.M., Murff J.D. (1990), "Effect of Jackup Spudcans on Piles", Proceedings Offshore Technology Conference (OTC 6467). 48 Dean, et al. (1995), "Centrifuge Modelling of 3-Leg Jackups with Non-Skirted and Skirted Spuds on Partially Drained Sand", Proceedings Offshore Technology Conference, Houston, (OTC 7839). 49 Wong P.C. and Murff J.D. (1994), "Dynamic Analysis of Jack-up Rigs Using Advanced Foundation Models", Proceedings OMAE, Houston, paper 94-1315 50 Svano and Tjelta (1993), "Skirted Spudcans - Extending Operational Depth and Improving Performance", 4th City University Jack-up Platform Conference, London. 51 Baerheim (1993), "Structural Effects of Foundation Fixity on a Large Jack-up", 4th City University Jack-up Platform Conference, London. 52 Van Langen and Hospers (1993), "Theoretical Model for Determining Rotational Behavior of Spudcans", Proceedings Offshore Technology Conference, Houston, (OTC 7302). 53 Noble Denton Europe & Oxford University (2005), "The Calibration of SNAME Spudcan Footing Equations with Field Data", Report No L19073/NDE/mjrh, Rev 4, dated 21st November 2005. 54 Templeton J.S., Lewis D.R., Brekke J.N. (2003), "Spud Can Fixity in Clay, First Findings of a 2003 IADC Study", 9th City University Jack-up Platform Conference, London. 55 Andersen K.H. (2004), "Cyclic clay data for foundation design of structures subjected to wave loading", Invited lecture, International Conf. on CyclicBehaviour of Soils and Liquefaction Phenomena, CBS04, Bochum, Germany. Proc. p. 371 – 387. 56 Svanø G. (1996), "Foundation Fixity Study for Jack-Up Unit", SINTEF report STF22 F96660, August 1996. 57. Murff, J. D., M. D. Prins, E. T. R. Dean, R. G. James, A. N. Schofield (1992), "Jack-Up Rig Foundation Modeling", Proceedings, Offshore Technology Conference, Houston, (OTC 6807). 58. van Langen, H., P. C. Wong, E. T. R. Dean (1997), “Formulation and Validation of a Theoretical Model for Jack-Up Foundation Load-Displacement Assessment”, Proceedings, 6th International Conference on the Jack-Up Platform – Design, Construction and Operation, London. 59. Wong, P. C., J. C. Chao, J. D. Murff, E. T. R. Dean, R. G. James, A. N. Schofield, Y. Tsukamoto (1993), “Jack-Up Rig Foundation Modeling II”, Proceedings, Offshore Technology Conference, Houston, (OTC 7303). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 127 Mobile Jack-Up Units Rev 3, August 2008 C.7 COMMENTARY TO CALCULATION METHODS – DETERMINATION OF RESPONSES C7.1 INTRODUCTION The main objective of this Section is to provide documentation of the considerations applied to the recommendations given in the Recommended Practice (PRACTICE) concerning the determination of extreme responses. The PRACTICE recommends that extreme response determination should always follow a procedure which always considers the potential dynamic magnification of the jack-up's behavior. C7.2 QUASI-STATIC EXTREME RESPONSE WITH INERTIAL LOADSET Section 7.2 of the PRACTICE recommends that quasi-static responses are normally determined by stepping the design wave through the structure. The extreme response is obtained by combining the quasi-static wave-current loading with wind loads, dead loads, etc., and an inertial loadset to represent the loading due to dynamic response. This method approximates the random nature of wave excitation and implicitly assumes that the extreme response is uniquely related to the occurrence of the extreme wave. As an alternative to the deterministic quasi-static design wave analysis a probabilistic quasi-static random wave analysis may be used. This procedure is identical to a random dynamic analysis procedure with the dynamic effects suppressed. Where software permits, suppression may be achieved by setting all jack-up vibrational masses to zero; see Section 7.3 of the PRACTICE. The significant wave height used for the random wave analysis should include a water depth correction as shown on Section 3.5.1 of the PRACTICE. C7.3 CONSIDERATIONS AFFECTING THE DYNAMIC RESPONSE The following considerations are relevant: a) The highest natural period of the jack-up, in absolute terms, in relation to the environmental excitation periods. For the present purpose the highest natural period (Tn) is used as the single indicator representing the properties of the structural system for the given application. The environmental excitation is due to sea waves and may contain energy at periods in the range 2-3 to some 20 seconds. The energy content in the wave spectrum at the lower end of this period range is controlled by wave saturation and is independent of the geographical location. Experience has shown, and theoretical calculations support, that the dynamic magnification may be neglected if the highest natural period does not exceed 2.5 seconds. The extent of the upper end of the period range, and its energy content, varies significantly with the geographic location, an important indicator being the peak period (Tp) of the wave spectrum of the extreme sea state. If Tn > 0.5 Tp the dynamic behavior becomes increasingly significant and complex, which always demands an appropriate dynamic analysis. Tn may be determined in accordance with Section 7.3.5 of the PRACTICE. The derivation of the equations is given in COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 128 Mobile Jack-Up Units Rev 3, August 2008 Appendix C7.A. The derivation of Tn and Tp are therefore critical to the dynamic analysis. Considerations for the calculation of Tn and Tp are given in Section C7.4. b) The magnitude of the dynamic magnification, relative to the quasi-static response. Engineering calculations are subject to inherent (in)accuracy as a result of uncertainties/inaccuracies in calculation methods and input data. Therefore, if the magnitude of the dynamic contribution remains smaller than some 5%, it may be considered to be covered by the overall margins included in the engineering assessment criteria in Section 8 of the PRACTICE, without explicitly quantifying and including the dynamic effect. For this evaluation, the magnitude of the dynamic contribution may be estimated by the Dynamic Amplification Factor (DAF) of an idealized single degree-of-freedom system in accordance with Section 7.3.6.1 of the PRACTICE. If the DAF < 1.05, dynamic magnification may be neglected. c) As the dynamic responses to periodic and random excitations can be significantly different, the random nature should (where possible) be retained in the modeling of the excitation. The simplified method described in Section 7.3.6.1 implicitly assumes periodic excitation. C7.3.7 Free surface corrections for frequency domain spectral wave load analysis When using frequency domain spectral techniques, the wave forces are evaluated using linear kinematics up to the mean water level only. Thus the force in the wave crests may be underestimated. The underestimation is perhaps further compounded by the drag force linearization. To account primarily for the effects if inundation, but also partially to correct any errors in the drag linearization, empirical factors (FSE's) may be derived to adjust the wave induced force and overturning moment obtained from a frequency domain spectral analysis. By way of an example, the maximum wave force and overturning moment on a pile group (representing jack-up legs) and accounting for free surface effects and drag force non-linearity, have been compared with the wave load on the same pie group when ignoring the sea surface variability and using linearized drag force. This yields separate FSE's for shear and overturning moment which may be used to make an initial correction for the above effects. Such factors are dependent on the kinematic stretching algorithm assumed. Using Wheeler stretching for a drag-dominated jack-up of typical size gives: FSES = π 2 1 2d + ⎧⎨⎩ ⎫⎬⎭ H FSET = π 2 1 2 2 + ⎧⎨⎩ ⎫⎬⎭ H d where; FSES = the base shear correction factor FSET = the overturning moment correction factor d = water depth H = the most probable maximum wave height (Hmax or Hmpm) Similar expressions may be derived for different wave stretching algorithms. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 129 Mobile Jack-Up Units Rev 3, August 2008 C7.3.7 For a jack-up subjected to wave and current loading these factors should be used to scale the MPM responses prior to combination with the mean (wind) response to form MPME. C7.4 SELECTION OF APPROPRIATE EXCITATION PERIOD Sections 7.3.3, 7.3.6, 7.3.7 and 7.4 of the PRACTICE require that an appropriate selection of excitation period is made. In making the selection consideration should be given to the position of the natural period(s) in relation to the cancellation and reinforcement points in the global wave loading of the jack-up which is important for the magnitude of any dynamic wave magnification. Cancellations and reinforcements in global loading are due to spatial separation of the wave load attracting legs and may be different for different wave directions. The global loading may be characterized by the total horizontal wave loading or overturning moment; cancellation and reinforcement of points for these may appear at slightly different wave periods. Figure C7.1 presents the periods at which first and second cancellations and reinforcements occur in the total wave loading. It is valid for the main wave directions of 3 and 4 -legged jack-ups in water depths exceeding 30m. The calculation of natural period(s) is subject to uncertainty as a result of uncertainty in the parameters affecting the natural period. In order to avoid the possibility of underconservative dynamic amplification factors, it is important to investigate the relationship between the jack-up natural period and the cancellation and reinforcement points in the transfer functions relating wave height to base shear and overturning moment [1]. The range of possible natural period(s) should be bracketed and compared with the relevant cancellation/reinforcement points in the global wave loading. The natural period(s) used in the dynamic analysis should be selected such that a realistic but conservative value of the dynamic response is obtained for the particular application envisaged, avoiding maximum dynamic amplification to coincide with minimum environmental loading. Figure C7.1 may be used for a first evaluation of the position of the calculated natural period(s), but it is recommended that the definitive selection of natural period(s) be based on the shape of the global horizontal wave loading (base shear) and overturning moment transfer functions calculated for the actual application under consideration. When the natural period occurs at a cancellation point in the transfer functions, the mass or stiffness should be adjusted in a logical manner to move the natural period away from the cancellation point. If the analysis is for pinned footings with maximum hull mass, then the adjustment should be made by reducing the hull mass (within the normal range) and/or by introducing a degree of rotational fixity at the seabed. If the analysis is for a case with footing moment fixity, then the adjustment would most logically be made by varying the degree of rotational fixity at the seabed. To minimise cancellation effects, it is suggested that the dynamic analysis may be carried out for a single wave heading along an axis which is neither parallel nor normal to a leg line. Thus, for a 3-legged unit with equilateral leg positions and a COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 130 Mobile Jack-Up Units Rev 3, August 2008 single bow leg, suitable analysis headings would be with the environment approaching from approximately 15o or 45o off the bow. The dynamic amplification factors (DAF’s) should be determined for one, or both, of these headings, with suitably adjusted natural period. The DAF’s (or more conservative DAF’s) may then be applied to the final quasi-static analysis for all headings and hull weight cases with, when applicable, non-linear fixity iteration according to Section 6.3.4.1 of the Practice. C7.5 METHODS FOR DIRECT DETERMINATION OF THE DYNAMIC RESPONSES Section 7.3.7 of the PRACTICE outlines some of the considerations which are relevant to direct methods for determining the dynamic responses. Appendix C7.B provides further details of appropriate methodologies, together with flowcharts indicating their implementation. An overview of the applicability of various modeling combinations is given in Table C7.1 (overleaf). For applications incorporating linearised foundation fixity in the dynamic analysis, the methodology of Appendix C7.B.2.1 is recommended using the time domain approach per Appendix C7.B.1.2. For applications incorporating non-linear foundation fixity in the dynamic analysis, the methodology needs to be selected with care, to ensure stable results. When the analysis is used solely to determine DAF’s it is probable that a time domain simulation of appropriate duration using the approach per Appendix C7.B.1.2 will be sufficient with the extremes determined using the methodology of Appendix C7.B.2.1. However, if the analysis is to be used to directly determine the extremes of other responses, then the methodology of Appendix C7.B.2.3 is recommended using the time domain approach per Appendix C7.B.1.2. This is because the results from the non-linear fixity analysis (where non-linear foundation response occurs) are dependent upon the load history experienced by the foundations. Consequently, the analysis should be carried out for a number of load histories in order to determine a reliable extreme value. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 131 Mobile Jack-Up Units Rev 3, August 2008 Model of the Environmental Analysis Structural Model Excitation (always nonlinear) Level Random Periodic Frequency Time Domain Domain Simple SDOF Linear A B full results not Nonlinear Unsuitable Unsuitable available directly MDOF Linear Generally not C Nonlinear recommended E D Complex - full MDOF Linear Generally not C results available Nonlinear recommended E D Notes: A - Combines a simplistic model of the structural system with a simplistic model of the excitation. B - Is a refinement of case A. It remains simplistic to execute and lends itself to both frequency and time domain methods. In the latter method the main nonlinearities in the excitation can be retained and therefore non-gaussian effects in the random response can be accounted for. Same limitations as for case A. C - Is a simplification of case D, if linear modeling of the structural system is a sufficiently accurate representation. D - Is the more complete and accurate representation of reality, but also the most complex. This is a necessary combination for a detailed evaluation of the dynamic behavior of a jack-up. Both random time and frequency domain methods can be used; the latter requires some approximation in the form of appropriate linearization of nonlinear terms and, therefore, the former are the most suitable. E - Incompatible combination. Table C7.1 : Recommended combinations of the structural system and environmental excitation models for a dynamic analysis COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 132 Mobile Jack-Up Units Rev 3, August 2008 Figure C7.1 : Periods for wave force cancellation and reinforcement as a function of leg spacing COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 133 Mobile Jack-Up Units Rev 3, August 2008 APPENDIX C7.A - DERIVATION OF JACK-UP STIFFNESS EQUATION To determine the natural period of a jack-up, the effective lateral stiffness seen by a horizontal load acting at the level of the jack-up hull is required. To determine this stiffness the following effects which cause hull lateral deflections are considered: 1. bending of the legs, leg-soil and leg-hull rotational stiffness. 2. shear deformation of the legs. 3. axial deformation of the legs. 4. hull bending deformation. 5. horizontal soil and leg-hull connection stiffness. 6. vertical soil and leg-hull connection stiffness. 7. second order P-Δ or Euler amplification. Effects 4, 5 and 6 may readily be considered by means of modifications to terms in the stiffness equation that can be derived for effects 1, 2 and 3. Taking each effect in turn: 1. Bending of the legs, leg-soil and leg-hull rotational stiffness. Consider one leg as shown in the Figure: F = shear transmitted from the hull E = Young's modulus ν = Poisson's ratio I = second moment of area of leg As = effective leg shear area L = length considered Krh = leg-hull connection rotational stiffness Krs = leg-soil connection rotational stiffness Mh = moment on leg-hull spring Ms = moment on leg-soil spring The bending equation may be written for any section z-z as: Mzz = F.z - Ms substituting the general equation of flexure: EI x z M M Fz zz s ∂ ∂ 2 2 = − = − . hence: EI x z M z F z A s ∂ ∂ = − . − + 2 2 EIx M z F z A z B s = . − . + . + 2 3 2 6 Apply the boundary condition: z = 0, x = 0, ∂ ∂ x z M K s rs = Hence: B = 0 and A = EIM K s rs COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 134 Mobile Jack-Up Units Rev 3, August 2008 The deflection at any point is then given by: EIx M z F z M zEI K s s rs = − + . 2 . 3 . . 2 6 (1) To determine Ms, apply the boundary condition: z = L, Mh = F.L - Ms, ∂ ∂ x z M K h rh = also from (1): ∂ ∂ x z M z EI F z EI M K s s rs = − + . . 2 2 Thus when z = L: ∂ ∂ x z M L EI F L EI m K M K F L M K s s rs h rh s rh = − + = = − . . 2 . 2 rearranging: Ms = F L K F L K K L EI rh rs rh . . + ⎧⎨⎩ ⎫⎬⎭ + + ⎧⎨⎩ ⎫⎬⎭ 2 2EI 1 1 (2) The deflection xLB at x = L, due to bending is (from (1)): xLB = M L M L K s s F L rs . 2 . . 3 2EI 6EI + − Rearranging and substituting from (2), the effective bending stiffness, KB = F/xLB, at z = L is obtained thus: x F L K L EI L EI L K K K L EI L LB EI rh rs rs rh = + ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨⎩ ⎫⎬⎭ + + ⎧⎨⎩ ⎫⎬⎭ − ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ 2 2 2 2 3 1 1 6 K L K L EI L EI L K K K L EI L B EI rh rs rs rh = + ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨⎩ ⎫⎬⎭ + + ⎧⎨⎩ ⎫⎬⎭ − ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ − 2 2 3 1 2 2 1 1 6 After rearrangement and manipulation: K EI L L EI LK K EI K L EI K B rs rh rs rh = − − + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ 3 1 3 4 3 3 2 / ( ) (3) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 135 Mobile Jack-Up Units Rev 3, August 2008 2. Shear deformation of the legs. Considering the shear force at any section zz is constant, the deflection xzzS due to shear is: xzzS = F.z/(As.G) but: G = E/{2(1 + ν)} and, for steel, ν = 0.3 hence: xzzS = 2.6F.z/(As.E) (4) and the shear stiffness, KS, when x = L is: KS = F x A E LS = s . 2.6L (5) 3. Axial deformation of the legs. A) Consider a 3-leg jack-up, and assume that the legs are placed at the vertices of an equilateral triangle. The shear applied to the hull is 3F, i.e. F acting on each leg. Case 1 Case 2 3.F.L - 3.Mu - R.Y = 0 3.F.L - 3.Mu - R.X = 0 thus: thus: R = 3(F.L M ) Y s − R = 3(F.L M ) X s − applying Hook's law: δaxial = 3( . ) . . F L M L A EY s − δaxial = 3( . ) . . F L M L A E X s − The resulting hull rotation is: θhull = 3.δaxial/(2.Y) θhull = 2.δaxial/X = 9 2A 2 ( . ) . . F L M L E Y s − = 6 2 ( . ) . . F L M L A E X s − COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 136 Mobile Jack-Up Units Rev 3, August 2008 and the horizontal hull deflection is: Δhorz = θhull.L Δhorz = θhull.L = 9 2 2 2 ( . ) . . F L M L A EY s − = 6 2 2 ( . ) . . F L M L A E X s − If X = Y/cos30 = Y 3 2 Δhorz = 9 2 2 2 ( . ) . . F L M L A EY s − i.e. assuming an equilateral hull, the two loading directions yield the same horizontal displacement at the hull: Δhorz = 9 2 2 2 ( . ) . . F L M L A EY s − (6) B) Consider an N-leg jack-up, where N = 4, and assume that the legs are placed in two parallel rows. The shear applied to the hull is NF, i.e. F acting on each leg. Applying similar methods as above: Δhorz = 4 2 2 ( . ) . . F L M L A E Y s − (7) where Y is the distance between the windward and leeward leg rows. Comparing equations (6) and (7), it can be seen that (6) is a factor, Fg, of: Fg = (9/2)/4 = 1.125 larger than (7). The effective horizontal stiffness due to axial deformation, KA, rearranging (7), including Fg and substituting for Ms from (2) is: KA = F F horz g Δ . = A EY L L L K L K K L EI g rh rs rh . . 2 / 2 2 4F 2EI 1 1 − + ⎧⎨⎩ ⎫⎬⎭ + + ⎧⎨⎩ ⎫⎬⎭ = A EY F L EI K L EI K L EI K g rs rs rh . . 2 / 4 3 2 + ⎧⎨⎩ ⎫⎬⎭ + + ⎧⎨⎩ ⎫⎬⎭ (8) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 137 Mobile Jack-Up Units Rev 3, August 2008 4. Hull bending deformation. Assume that the hull can be represented by equivalent beams joining the legs, of typical bending stiffness IH: If it is assumed that the hull deflects in double-curvature under the influence of the moments transmitted by the leg-hull connection springs, and that the rotational deflections at the two sides are equal (the side with higher stiffness has two legs acting on it) we can write, for one half of the beam: θ = M Y E IH .( / . 2) Hence the hull rotational stiffness Khull, = M/θ = 2E.IH/Y If this stiffness is considered as acting in series with the leg-hull connection spring Krh, the modified stiffness is: Krh' = 1 1 1 / K K rh hull + ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ Rearranging, and substituting for Khull gives: Krh' = Krh/(1 + Y K I rh H . 2E. ) Hence the modification factor Fr, to be applied to the leg-hull connection stiffness, Krh, to account for hull flexibility is: Fr = 1 1 2E + ⎧⎨⎩ ⎫⎬⎭ Y K I rh H . . (9) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 138 Mobile Jack-Up Units Rev 3, August 2008 5. Horizontal soil leg-hull connection stiffness. The horizontal soil and leg-hull connection stiffnesses, Khs and Khh, may be considered to act in series with the lateral stiffness due to leg shear deformation (ASG/L). The combined stiffnesses is then: KS' = 1 1 1 / L A G K K S hs hh + + ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ rearranging, gives: KS' = (ASG/L)/(1 + A G LK A G LK S hs S hh + ) = (ASG/L)(1 + A E L K A E L K S hs S hh . . . . 2 6 2.6 . + ) If it is considered that the modified leg deformation stiffness Ks' is linked to the unmodified value by a factor, Fh: Fh = 1 1 26L 26L + + ⎧⎨⎩ ⎫⎬⎭ A E K A E K s hs s hh . . . . . . (10) 6. Vertical soil and leg-hull connection stiffness. The vertical soil and leg-hull connection stiffnesses, Kvs and Kvh, may be considered to act in series with the axial stiffness due to leg axial deformation (AE/L). The combined stiffnesses is then: KA' = 1 1 1 / L AE K K vs vh + + ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ rearranging: KA' = (AE/L)/(1 + AE LK AE LK vs vh + ) If it is considered that the modified leg deformation stiffness KA' is linked to the unmodified value by a factor, Fv: Fv = 1 1+ + ⎧⎨⎩ ⎫⎬⎭ AE L K AE L K vs vh . . (11) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 139 Mobile Jack-Up Units Rev 3, August 2008 7. Second order P-Δ or Euler amplification. The deflection will (approximately) be amplified by a factor (1 - [P/PE]) due to second order effects. The Euler load, PE, may be derived as follows, accounting for the soil and leg-hull connection rotational springs: P = axial load in leg E = Young's modulus I = second moment of area of leg L = length considered Krh = leg-hull connection rotational stiffness Krs = leg-soil connection rotational stiffness Mh = moment on leg-hull spring Ms = moment on leg-soil spring xh = hull deflection The bending equation may be written for any section z-z as: MZZ = P.x - MS substituting the general equation of flexure: EI x z ∂ ∂ 2 2 = -Mzz = Ms - P.x hence: ∂ ∂ 2 2 x z P x E I M E I + = s . . . let μ2 = P/E.I hence: ∂ ∂ μ 2 2 2 0 x z x M P + ( − s ) = (12) The solution to (12) is: x = A.Cosμz + B.Sinμz + M P s (13) differentiating (13): ∂ ∂ x z = -μA.Sinμz + μB.Cosμz (14) When z = 0, x = 0 and hence, from (13), A = -Ms/P When z = 0, ∂ ∂ x z M K s rs = and hence, from (14) B = Ms/(μ.Krs) Thus: x M P Cos z M K Sin z M P s s rs = s − . μ + . + μ μ (15) and: ∂ ∂ μ μ μ x z M P Sin z M K s s Cos z rs = . + . (16) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 140 Mobile Jack-Up Units Rev 3, August 2008 Apply boundary conditions at leg-hull interface to derive the equation yielding the Euler load: When z = L, ∂ ∂ x z M K h rh = (17) and x = xh (18) also Mh = P.xh - Ms (19) From (16) and (17): M K M P Sin L M K h Cos L rh s s rs = + μ . μ . μ (20) From (15) and (18): xh = − + + M P Cos L M K Sin L M P s s rs . μ . s μ μ (21) Substituting (21) into (19) gives: Mh = − M Cos L+ P M K Sin L s s rs . . μ . μ μ hence: M M P K h Sin L Cos L s rs = − μ . μ μ (22) Rearranging (20) gives: M M K P Sin L K K h Cos L s rh rh rs = + μ . μ . μ (23) Equating the (22) and (23): Sin L P K K P Cos L K K rs rh rh rs μ μ μ μ . − ⎧⎨⎩ ⎫⎬⎭ = + ⎧⎨⎩ ⎫⎬⎭ 1 or: Tan L K K P K K P rh rs rs rh μ μ μ = + ⎧⎨⎩ ⎫⎬⎭ − ⎧⎨⎩ ⎫⎬⎭ 1 . = μ μ μ K P K P P K K rs rh rs rh . . . + 2 − 2 By definition P = μ2EI so: TanμL = ( ) ( ) ( . ) K K EI EI K K rs rh rs rh + − μ μ 2 (24) Notes: 1. When Krs = 0, and Krh = ∞, (24) reduces to TanμL = ∞ i.e. μL = π/2, 3π/2, 5π/2, … The smallest finite value satisfying (24) is π/2, thus μL = π/2 and μ2 = P/(EI) hence: PE = π2EI / (4L2) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 141 Mobile Jack-Up Units Rev 3, August 2008 2. When Krs = ∞, and Krh = ∞, (24) reduces to TanμL = 0 i.e. μL = 0, π, 2π, 3π, … Rejecting the first value (μL = 0) as this give PE = 0, the smallest value satisfying (24) is μL = π hence: PE = π2EI / L2 3. For finite values of Krs and Krh the Euler load may be determined using a graphical solution. For example: Krs = 2.65 x 1010 Nm/rad Krh = 5.30 x 1010 Nm/rad E = 2.10 x 1011 N/m2 I = 7.45 m4 L = 100m From equation (24) the LHS = TanμL = Tan100μ (Note μ is in radians/m) the RHS = ( ) ( ) ( . ) K K EI EI K K rs rh rs rh + − μ μ 2 = 124 4 2448 2 14045 . . μ μ − Plotting these as shown in Figure C7.A.1 the smallest non-zero value in the example is μ1 = 0.018248. Thus the Euler crippling load is: PE = (0.018248)2EI or, in the more general form: PE = 0.337389π2EI / L2 Figure C7.A.1 Graphical solution of equation (24) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 142 Mobile Jack-Up Units Rev 3, August 2008 COMBINING EFFECTS 1 TO 7 ABOVE: For the leg under consideration, all the effects can be combined by considering the components as springs in series, thus Ke, the effective spring stiffness for one leg is deduced from: 1 1 1 1 K K K K e B S A = + + where the stiffness terms KB, KS and KA are derived in (3), (5) and (8). Rearranging and including the Euler amplification effect: K P P K K K e E B S A = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ + + 1 1 1 1 = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ − − + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ + + + + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ 1 1 3 4 3 3 26 2 4 2 3 2 3 P P L EI LK K EI K L EI K EI L L A E EI K L EI K L EI K A EY F L E rs rh rs rh s rs rs rh g ( ) / . . . . / = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ − − + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ + + + + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ 3 1 1 3 4 3 78I 4F 3 3 2L 3 2 2 3 2 2 3 2 EI L P P L EI LK K EI K L EI K A L L AEY EI L K EI EI K L EI K E rs rh rs rh s g rs rs rh ( ) . . ( ) = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ − − + ⎧⎨⎩ ⎫⎬⎭ − + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ + 3 1 1 3 4 4 3 3 2 3 78 3 3 2 2 3 2 2 2 EI L P P L F L AEY EI K L EI L EI LK K EI K L EI K I A L E g rs rs rh rs rh s ( ) ( ) . . = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ − − + ⎧⎨⎩ ⎫⎬⎭ − + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ + 3 1 1 3 4 12F 2 3 78I 3 2 2 2 EI L P P L I AY EI K L EI LK K EI K L EI K A L E g rs rs rh rs rh s ( ) . . COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 143 Mobile Jack-Up Units Rev 3, August 2008 If the correction terms to Krh, As and A which are Fr, Fh, and Fv as defined in (9), (10) and (11) respectively are included: K EI L P P L I F AY EI K L EI F LK K EI K L EI F K F A L e E g v rs r rs rh rs r rh h s = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ − − + ⎧⎨⎩ ⎫⎬⎭ − + + ⎧ ⎨ ⎪⎪ ⎩ ⎪⎪ ⎫ ⎬ ⎪⎪ ⎭ ⎪⎪ + 3 1 1 3 4 12F 2 3 78I 3 2 2 2 ( ) . . . If the foundation is effectively pinned, and Krs = 0, the equation can be simplified as follows (multiply top and bottom of central term in denominator by Krs, and then set Krs = 0): K EI L P P I F AY EI F LK F A L e E g v r rh h s = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ + + + 3 1 1 12F 3 78I 3 2 2 . . . If the foundation and leg-hull connection are effectively encastré, and Krs = Krh = ∞, the equation can be simplified as follows (note that the Fr term to incorporate hull stiffness has vanished, as its definition relies on a finite value of Krh; if an alternative definition were applied, its effect could be retained). K L P P I F AY F A L e E g v h s = − ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ + + 12EI 1 1 24F 312I 3 2 2 . . . In the absence of any of the terms for effects other than bending (i.e. setting A and As to infinity), this further reduces to 12EI/L3, which is as expected for a beam, encastré at each end, with one end free to slide. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 144 Mobile Jack-Up Units Rev 3, August 2008 APPENDIX C7.B - DETAILS OF APPROPRIATE DYNAMIC ANALYSIS METHODS Section 7.3.6.1 of the PRACTICE provides a simple approach to determining the dynamic response, based on the SDOF approximation. Sections 7.3.6.2 and 7.3.7 of the PRACTICE outline more complex approaches and some specific recommendations are included in Tables 7.1, 7.2 and 7.3. It should be noted that the basic analysis may be carried out in either the frequency or time domain and that there are then a number of approaches for determining the required most probable maximum (MPM) response which is defined in Table 7.3 of the PRACTICE as the mode value (or highest point on the PDF with a 63% chance of exceedance). This corresponds to a 1/1000 probability level in a 3-hour storm. The recommended, more complex, analysis methods are described below, together with appropriate methods of determining the MPME. These may be summarized as follows: C7.B.1 Analysis Methods C7.B.1.1 Frequency Domain Methods: - Use entire RAO (DAF) from simplified SDOF model. - Use RAO from multi-degree-of-freedom (MDOF) model, with appropriate linearization. Frequency domain methods require the linearization of the wave-current drag loading. It is recommended that the statistical (or least squares) linearization procedure formulated by Borgman is adopted [L.E. Borgman, 'Ocean Wave Simulation for Engineering Design', Civil Engineering in the Oceans, ASCE conference, San Francisco, September 1967]; other forms of linearization may not adequately handle the current velocity, wave induced particle velocity and the structures velocity (if a relative velocity formulation is used). Table 7.2 of the PRACTICE makes some additional recommendations regarding the generation of the random seastate. C7.B.1.2 Time Domain methods: - Use simplified SDOF model. - Use MDOF model. Time domain simulations require a suitable generation of the random seastate, that the validity of the generated seastate is checked, and that the time-step for the solution of the equations of motion is sufficiently small. It is also necessary to ensure that the duration of the simulation(s) is sufficient for the method being used to determine the MPME. Specific recommendations are given in Tables 7.2 and 7.3 of the PRACTICE. C7.B.2 Methods for Determining the MPME It should be noted that the simpler modeling approaches will not lead directly to the MPME of all quantities of interest. For example, SDOF based models will provide directly only the MPME hull displacement; simpler multi-degree-of-freedom models may provide the MPME of total leg loads, but will not lead directly to loads in individual members of a truss-leg. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 145 Mobile Jack-Up Units Rev 3, August 2008 As a means of circumventing this difficulty the analysis may be used solely to determine the inertial loadset which represents the contribution of dynamics over and above the quasi-static response (see Figure C7.B.1). The inertial loadset is then applied to a structural model of appropriate complexity together with all the quasi-static loads (due to wind, wave/current, weight, etc.) and the required responses determined. The simplest inertial loadset uses a single point load at deck level. The magnitude of this force is calculated to match the inertial overturning moment effects as shown on the right hand side of figure C7.B.1 (blocks 18, 23, 24, and 25). It is possible to refine this loadset to match both base shear and overturning moment inertial effects by simply determining the magnitude of the loadset to match the inertial base shear and then applying this loadset (single point load) at an elevation such that the inertial overturning moment is matched. However, the use of a distributed inertial loadset is considered more representative and will, in turn, result in a more accurate description of the component dynamic amplification effects as well as the amplification of global responses. The distribution of the inertial loadset is based on the fundamental sway modes and the mass distribution and is determined so that both the global base shear and overturning moment responses are matched. Figure C7.B.1 (on the left hand side) outlines how a distributed loadset (2-dimensional response) is determined based on the first two fundamental bending modes (in the same direction) and the mass distribution. An alternative to the inertial loadset approach is to use transfer functions to link known responses with other required responses (for example to determine leg member loads from total leg loads). The derivation of such transfer functions requires the use of appropriately detailed models. Where non-linearities are significant the transfer functions are not linear (and cannot be linearized) and may vary, for example, as a function of the level of leg load(s). The following methods are recommended for determining the MPME: - Use of drag-inertia parameter (or equivalent) determined from mean and standard deviation of a frequency or time-domain analysis. - Fit Weibull distribution to results of a number of time-domain simulations to determine responses at required probability level and average the results. - Fit Gumbel distribution to histogram of peak responses from a number of timedomain simulations to determine responses at required probability level. - Apply Winterstein's Hermite polynomial method to the results of time domain simulation(s). Further details of the approaches are given below: COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 146 Mobile Jack-Up Units Rev 3, August 2008 C7.B.2.1 Use of drag-inertia parameter (or equivalent) determined from mean and standard deviation of a frequency or time-domain analysis This procedure relies on the identification of the two components of the total dynamic response, i.e. the quasi-static and the 'inertial' parts. The 'inertial' part is the amplification of the quasi-static part due to dynamic effects, and should not be confused with inertial wave loading. The procedure requires the determination of the basic statistical parameters of the mean, μ, and the standard deviation (excluding the mean), σ, of the required response variable(s). In general the root-mean-square, RMS, ≠ σ, unless μ = 0. The notation MPMR is used to refer to the most probable value of the response minus the mean response, R(t) - μR, for a given storm duration. When the mean is included the MPM value is referred to as the most probable maximum extreme of R(t) and denoted by MPMER. The response quantity of interest is indicated by the general notation R; this can be any quantity which is related to the random wave excitation (e.g. base shear BS, overturning moment OTM, etc.) Where necessary to distinguish between different forms of response a second subscript is used as follows: 's' for (quasi-)static, 'i' for inertial and 'd' for total dynamic (quasi-static plus inertial) response. The procedure for estimating the extreme response is shown on Figure C7.B.4, and requires the means and standard deviations of the (overall) dynamic and quasi-static response, and the standard deviation of the 'inertial' response. These can be determined from time domain simulations (Figure C7.B.2) or frequency domain analyses (Figure C7.B.3). Figures C7.B.5 or C7.B.6 form an input to Figure C7.B.4. These Figures are based on [SIPM EPD/51/52 'Dynamic Analysis and Estimation of Extreme Responses for Jack-Ups', August 1991]. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 147 Mobile Jack-Up Units Rev 3, August 2008 C7.B.2.2 Fit Weibull distribution to results of a number of time-domain; simulations to determine responses at required probability level and; average the results. This procedure requires a suitable length time domain simulation record for each quantity of interest. The input seastate record should be checked for 'Gaussianity'. Guidance is given in Tables 7.2 and 7.3 of the PRACTICE. The procedure requires the following steps. Step 1 The signal record is first analyzed to calculate the mean, μR, as: μ R i i n R t n = − Σ ( ) 1 where R(ti) = time history of signal ti = time points n = number of useable time points in simulation (discounting the run-in) Step 2 The individual point-in-time maxima are next extracted according to the following criteria: A maximum occurs at ti if: R(ti-1) < R(ti) and R(ti+1) ≤ R(ti) Suppose Nmax maxima are found in the extraction. Step 3 From the Nmax maxima, the mean of the signal, μR, is subtracted and the maxima R(max,i) are ranked into 20 blocks having mid-points in ascending order. The blocks all have the same width and the upper bound of block 20 is taken as being 1.01 x the largest value, the lower bound of the first block being zero. A distribution of maxima observations is then found, using for each block the Gumbel plotting position in order to obtain the best possible description of the distribution for large values of R. If each block has ni maxima, the cumulative probability Fi to be plotted against the mid point for block i is then given by: F n n N i j j j i j j j i = + + = = − = = [( Σ )Σ ] . / ( ) max 1 1 0 1 0 0 5 where n0 = 0. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 148 Mobile Jack-Up Units Rev 3, August 2008 C7.B.2.2 Step 4.a A Weibull distribution is fitted against the cumulative distribution of the maxima as defined under Step 3 (see Steps 4.b to 4.d). The 3-parameter Weibull cumulative distribution function is defined as: F(R;α,β,γ) = 1 - exp. − − ⎧⎨⎩ ⎫⎬⎭ ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ R γ α β where; F(R;α,β,γ) = probability of non-exceedance α = scale parameter β = slope parameter γ = threshold parameter and α,β,(R-γ) > 0.0 Step 4.b Only data points R(max,i), corresponding to a probability of non-exceedance greater than a threshold value of 0.2 are used to fit the Weibull distribution, i.e. only the points: R N i (max,i) N max max − + ⎧⎨⎩ ⎫⎬⎭ ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ 1 for i>0.2 x Nmax Notice that R(max,i) are in ascending order. Step 4.c For each of these points, the deviations between the Weibull distribution and the values R(max,i) (transformed to Weibull scales) are calculated as: δi = ln[-ln{1-F(R(max,i),α,β,γ)}] - β[ln(r(max,i)-γ) - ln(α)] Step 4.d The parameters α,β,γ are now estimated by a non-linear least square technique, i.e. δ i i N N 2 =0 2 Σ . max max is minimized The procedure may be based on a Levenberg-Marquardt algorithm, using the parameters of a 2-parameter Weibull distribution (found by the maximum likelihood method) as initial estimates. Step 5 The MPM value RMPM is found as the value of R for which: F(R,α,β,γ) = 1 - 1 Nmax . 3 hours simulation duration ⎧⎨⎩ ⎫⎬⎭ Step 6 The total extreme MPM value, RMPME is found as: RMPME = μR + RMPM where μR = the mean value of R established in Step 1 RMPM = the MPM value (excluding the mean) established in Step 5. Step 7 The procedure is repeated for each required response parameter. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 149 Mobile Jack-Up Units Rev 3, August 2008 C7.B.2.3 Fit Gumbel distribution to histogram of peak responses from a number of time-domain simulations to determine responses at required probability level. The basic assumption of this method is that the 3-hour extreme values follow a Gumbel distribution: F3h(x) = exp − − − ⎧⎨⎩ ⎫⎬⎭ ⎡ ⎣ ⎢ ⎤ ⎦ ⎥ exp x ψ κ where; F3h(x) = the probability that the 3-hour maximum will not exceed value x. ψ = location parameter κ = scale parameter The following steps are followed for each required response parameter: Step 1 Extract maximum (and minimum) value for each of 10 3-hour response signal records. Step 2 A Gumbel distribution is fitted through these 10 maxima/minima. This is done using the maximum likelihood method, yielding ψ and κ. Step 3 The Most Probable Maximum Extreme is found according to: MPME = ψ - κ ln − ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ln{F3h ( MPME)} with; F3h (MPME) = 0.37 The 0.37 lower quantile is used because the extreme of recurrence of once in 3 hours will have a probability of exceedance of 0.63 (= 1 - 0.37). In this case it can be seen that: MPME = ψ Step 4 The procedure of Step 3 is similarly applied for minima. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 150 Mobile Jack-Up Units Rev 3, August 2008 C7.B.2.4 Apply Winterstein's Hermite polynomial method to the results of time domain simulation(s). For Gaussian processes, analytical results exist for the determination of the MPM values (e.g. MPM wave height = 1.86 x significant wave height). For general noninear, non-gaussian, finite band-width processes, approximate methods are required to generate the probability density function of the process. The method proposed by Winterstein [Winterstein S.R., 'Non-Linear Vibration Models for Extremes and Fatigue', Journal of Engineering Mechanics, Vol. 114, No 10, 1988] fits a Hermite polynomial of gaussian processes to transform the non-linear, non-gaussian process into a mathematically tractable probability density function. This has been further refined by Jensen [Jensen, J.J. 'Dynamic Amplification of Offshore Steel Platform Responses due to Non-Gaussian Wave Loads', The Danish Center for Applied Mathematics and Mechanics Report No 425, May 1991, Submitted to Journal of Structural Engineering, ASCE] for processes with large kurtosis. This procedure requires a suitable length time domain simulation record for each quantity of interest. The input seastate record should be checked for 'Gaussianity'. Guidance is given in Tables 7.1 and 7.2 of the PRACTICE. The calculation procedure to determine the maximum of a time series, R(t), in duration T is as follows: Step 1 Calculate the following quantities of the time series for the parameter under consideration: μ = mean of the process σ = standard deviation α3 = skewness α4 = kurtosis Step 2 Hence construct a standardised response process, z = (R - μ)/σ. Using this standardised process, calculate the number of zero-upcrossings, N. In lieu of an actual cycle count from the simulated time series, N = 1000 may be assumed for a 3-hour simulation. Step 3 Compute the following quantities from the characteristics of the response parameters identified earlier: h3 = α3 / [4 + 2 {1+1.5(α4 − 3)}] h4 = [ {1 15 3 } 1] 18 4 + . (α − ) − / K = [1 2h 6h ] 3 2 4 2 1 + + 2 − COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 151 Mobile Jack-Up Units Rev 3, August 2008 Step 3 It is necessary to seek a more accurate result by determining the solution of the following equations for C1, C2 and C3: σ2 = C1 2 + 6C1C3 + 2C2 2 + 15C3 2 σ3α3 = C2(6C1 2 + 8C2 2 + 72C1C3 + 270C3 2) σ4α4 = 60C2 4 + 3C1 4 + 10395C3 4 + 60C1 2C2 2 + 4500C2 2C3 2 + 630C1 2C3 2 + 936C1C2 2C3 + 3780C1C3 3 + 60C1 3C3 using as initial guesses: C1 = σK(1-3h4) C2 = σKh3 C3 = σKh4 with σ, K, h3 and h4 from above. Following the solution for C1, C2 and C3, the values for K, h3 and h4 are computed as follows: K = (C1 + 3C3)/σ h3 = C2/(σK) h4 = C3/(σK) Step 4 The most probable value, U, of the transformed process is computed by the following equation: U = ( )⎟ ⎟⎠ ⎞ ⎜ ⎜⎝ ⎛ ⋅ simulation time in hours hours N e 3 2 log Where U is a Gaussian process of zero mean, unit variance. Step 5 The most probable maximum, transformed back to the standardised variable, z, is then given by: zMPM = K[U + h3(U2 - 1) + h4(U3 - 3U)] Step 6 Finally, the most probable maximum extreme in the period T, for the response under consideration, can be computed from the following equation: RMPME = μ + σzMPM COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Figure C7.B.1, Part 1 - Procedure for determining inertial loadset Notes with Figure C7.B.1 - Part 1 General The figure shows two possible paths. The path on the left through blocks 19 to 22 matches the dynamic base shear and the dynamic overturning moment, by making up the difference between the dynamic and static base shears by a distributed inertial force. This distributed inertial force is established by an appropriate combination of structural mode shapes and lumped masses. The basis for the calculation is that the base shear and overturning moment inertial effects are simultaneously matched and combined in phase with the quasi-static loads such that the levels of total global response are maximized. By contrast, the path on the right chooses to match the dynamic overturning moment by an inertial force in the form of a point load at deck level. This is a very reasonable approximation of the inertial loadset, for cases where the mass of the hull is much larger than the masses of the legs and the mode participation factor (the relative horizontal displacement of the vibrating jack-up) is also largest at the deck elevation. The inertial point load thus determined is again not equal to the difference in dynamic and static base shears; generally it overmatches the dynamic base shear. In this case the remaining excess force is not compensated for (as was possible for the path on the left) and must be accepted as an element of some conservatism. Re blocks 17 and 18: The input to these blocks is obtained from Figure C7.B.4 (blocks 14, 15 and 16). Note that DAF3T will be greater than DAF3S. This is in agreement with experience and supported by theory. Re block 19: An outline calculation of the distribution of F1i over height is given in Figure C7.B.1 (Part 2). Re block 23: The force F2i follows directly from the increase in OTM and the height h at which F2i is applied above the effective hinge or fixation points of the legs Therefore this does not require knowledge of the mass distribution and mode shape. Re block 24: The excess F3i in representing the dynamic base shear is calculated as general verification. If F3i is found to be relatively large compared to the dynamic base shear it is recommended to follow the path on the left instead of the path on the right. A criterion for this should be set by the user; as a suggestion the excess should not be greater than up to 5% of the dynamic base shear. . Commentaries to Recommended Practice for Site Specific Assessment of Page 154 Mobile Jack-Up Units Rev 3, August 2008 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 153 Mobile Jack-Up Units Rev 3, August 2008 Notes with Figure C7.B.1 - Part 2 Procedure for Determining (Distributed) Inertial Loadset. The extreme inertial load will generally be three dimensional in nature. It should be noted that vertical dynamic response effects are not normally significant for storm conditions. It is assumed that the response of the Jack-up under combination of wave/current and inertial loading will be in-line with the applied wave and current actions. Hence a 2-D response is considered along one of the global structural axes. The first two bending sway modes (i.e. global modes rather than local leg bending modes) acting along the selected axis are combined to form a pair of simultaneous equations which match both inertial base shear and overturning moment. Base shear is given by the product of mass and assumed acceleration profile, and overturning moment by the product of mass, assumed lateral acceleration profile and lever arm above footing level i.e. M1i = α φ1 MZ + β φ2 MZ F1i = α φ1 M + β φ2 M (1) where M1i is the global inertial overturning moment (zero mean) F1i is the global inertial base shear (zero mean) φ1 is the first global sway/bending mode shape φ2 is the second global sway/bending mode shape M is a matrix of structural masses Z is a vector of point elevations above footing level α and β are scalars Global inertial responses are calculated from the global response DAFs generated by the dynamic analyses, combined with the design wave and current load i.e. F1i = (DAF3S-1)mpmeSs M1i = (DAF3T-1)mpmeTs (2) where DAF3Ts is the global overturning moment DAF (using mpme responses) DAF3Ss is the global base shear DAF (using mpme responses) M1i is the maximum design wave and current overturning moment F1i is the maximum design wave and current base shear mpmeSs is the most probable maximum extreme static shear mpmeTs is the most probable maximum extreme static overturning moment The simultaneous equations (1) are solved for scalar multipliers α and β, which are used to calculate the inertial load set i.e. Fin = α φ1 M + β φ2 M (3) In its current format, Fin is a distributed load vector consisting of horizontal forces applied to each point mass in the structure. Equations (1) to (3) can be readily adapted such that the inertial load is fully three dimensional in nature, by using the first and second global (3-D) sway modes along both horizontal axes, and extending equation set (1) to 4 components. Jack-up structures exhibit several unique properties which allow the use of a simplified inertial load set calculation procedure. For the majority of units, approximately 80% of the total system mass (including added fluid mass) effectively acts at the hull COG. In addition, the mass and stiffness distribution results in the ratio of the first and second bending/sway mode periods for each principal direction being in excess of 5. This leads to the resonant component of response being largely confined to the fundamental modes in each direction (sway and surge), with a potential contribution from the first torsional mode (yaw). On this basis, and assuming torsion can be ignored, equation set (1) can be reduced: M1i = αδHMHZH F1i = αδHMH (4) where δH is the first mode shape ordinate at the hull COG MH is the point mass acting at the hull COG ZH is the elevation of the hull COG above footing level We can clearly relate the second of equations (4) with the inertial load set given in Section 7.3.6.1 of the Practice. Figure C7.B.1, Part 2 - Procedure for determining (distributed) inertial loadset COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 154 Mobile Jack-Up Units Rev 3, August 2008 Specific notes with Figure C7.B.2 General The procedure for estimating the extreme response due to hydrodynamic loading shown in Figure C7.B.4 requires knowledge of the mean and the standard deviation of the quasi-static and dynamic responses, and the standard deviation of the "inertial" response. A time domain procedure may be used to determine these. Re blocks 4, 5, 6: The mean of the "inertial" response is not used in the procedure. In most cases the mean of the static response will be (approximately) equal to the mean of the dynamic response. Therefore, the mean of the "inertial" response will be (approximately) zero. This may serve as a check on the simulations performed. However, under certain conditions the means may truly be different. this can most clearly be seen when relative velocities (i.e. the wave induced water particle velocity minus the structure's velocity) are used to perform the dynamic simulation. Figure C7.B.2 Time domain procedure for determining mean and standard deviation COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 155 Mobile Jack-Up Units Rev 3, August 2008 Specific notes with Figure C7.B.3 General The procedure for estimating the extreme response due to hydrodynamic loading shown in Figure C7.B.4 requires knowledge of the mean and the standard deviation of the quasi-static and the dynamic responses, and the standard deviation of the "inertial" response. A frequency domain procedure may be used to determine these. In order to reflect the interactions between the current velocity, the absolute wave induced water particle velocity and the structure's velocity (if a relative velocity formulation is adopted) and to linearize the associated drag loading adequately it is necessary to adopt a statistical or least squares linearization procedure as first formulated by Borgman (see Ref. below). Other forms of linearization in frequency domain analysis cannot handle these interactions. For the least square linearization procedure, there only is a mean response in case of a non-zero current. The magnitude of the mean depends on the value of the current velocity and on the standard deviation of the wave induced (horizontal) water particle velocity, both taken at the same elevation z, and subsequently integrated over the full water depth. The wave induced water particle velocity may be the absolute or the relative velocity, depending on which of these is more appropriate for the case considered. The transfer functions HRs(ω) and HRd(ω) between the response and the water surface elevation are similarly dependent on both the wave induced (horizontal) absolute or relative velocities and the current velocities at various elevations. The means mRs and mRd and the transfer functions HRs(ω) and HRd(ω), are therefore a function of the sea state and the current sued in the environmental definition. Re block 3: The transfer function representing the difference between the dynamic and the quasi-static response is only notionally associated with "mass inertial" forces (not to be confused with inertial wave loading). The difference may additionally be due to damping forces and any effect causing (frequency dependent) phase differences between HRd(ω) and HRs(ω). (e.g. associated with multi degree of freedom system responses). Re blocks 4, 5, 6: The spectral analyses operate on the transfer functions HRx(ω), which by definition represent the time varying part of the response minus the mean, i.e. Rx(t)-μRx. A similar note on the mean values of the various responses as given with Figure C7.B.2 should be made here. The mean value of the "inertial" response cannot be determined in a frequency domain analysis and is not required either. However, the fact remains that in most cases the mean of the static response will be (approximately) equal to the mean of the dynamic response. This should again serve as a useful check o the analyses performed. From the above general note it can be seen that both means will only be non-zero if there is a current present. When relative velocities are used in the analysis of the dynamic problem the interaction between the current and the relative velocity may be different for the dynamic and the static case, resulting in realistically different mean values. Reference: L.E. Borgman "Ocean wave simulation for engineering design" Civil Engineering in the Oceans, ASCE conference, San Francisco, September 1967 Figure C7.B.3 Frequency domain procedure for determining mean and standard deviation COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 156 Mobile Jack-Up Units Rev 3, August 2008 Figure C7.B.4 Procedure for estimating the extreme response COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 157 Mobile Jack-Up Units Rev 3, August 2008 Specific notes with Figure C7.B.4 Re block 7: The correlation coefficient ρR is theoretically a value between -1 and +1. For virtually all applications to offshore structures problems it is expected that: δ2 Rd > δ2 Rs + δ2 Ri so that 0 < ρR < 1. For rR = 0, zero correlation, the quasi-static and "inertial" responses do not influence one another and will be well separated in the frequency domain. This is generally only to be expected for relatively low natural periods which fall in the (very) high frequency tail of the wave spectrum and where HRs(ω) is also very low. Under these circumstances the variance (or mean square) of the full dynamic response is equal to the sum of the variances of the quasistatic response and the "inertial" response: δ2 Rd = δ2 Rs + δ2 Ri Geometrically, this means a direct addition of non-overlapping areas of the two parts of the response spectrum. For rR = 1, full correlation, the quasi-static and "inertial" responses are fully dependent on one another. The two parts of the response spectrum overlap strongly and will not really be distinguishable. This will increasingly be the case for high natural periods, considerably closer to the peak of the wave spectrum and therefore associated with a region of significant wave energy, and where HRs(ω) is also having appreciable values. Under these circumstances the standard deviation (instead of the variance) of the full dynamic response is equal to the sum of the standard deviations of the quasi-static response and the "inertial" response: δRd = δRs + δRi Re blocks 8, 12, 16: Several definitions of the dynamic amplification factor DAF are in use. The purest and most meaningful definition is believed to be DAF1, the ratio of the standard deviations of the dynamic and static responses (block 8), i.e. after eliminating the means which are not affected by dynamic magnification. If the static and the dynamic processes are both gaussian, or to an equal degree non-gaussian, then DAF2 = DAF1; however, this will not be the case in general. The ratio DAF3 of the most probably maximum extremes, including the means, is a practical overall measure of the increase in response due to dynamics. Re block 9: The mpm-factor for an arbitrary non-gaussian response is not known. As an engineering postulate it is assumed that this is equal to the mpm-factor for Morison type wave loading on a cylindrical element of unit length. The factor for a nominal number of 1000 peaks (corresponding approximately with a 3 hr storm duration) then varies between the extremes of 3.7 (for inertial wave loading only and hence a gaussian process) and 8.0 (for drag waver loading only and consequently a strongly non-gaussian process). It can be determined on the basis of a drag-inertia parameter or the kurtosis of the response, as shown in Figure C7.B.5 with its associated notes. Note that the factor 8.0 is different from the previously used factor of 8.6. This is due to the fact that in this report the most probably maximum is consistently used as a predictor for the maximum of a random process. The previous factor 8.6 referred to the expected maximum instead of the most probably maximum. Re block 10: The mpm-factor for the "inertial" part of the response is associated with the dynamic behavior and predominantly of a purely narrow banded resonant nature. Experience has shown (and theory supports this) that such lightly damped dynamic processes tend towards gaussianity so that a mpm-factor of 3.7 is a reasonable and confident assumption for engineering purposes. Re block 11: The relationship between the mpm-values is entirely analogous with the relationship between the standard deviations from which the correlation coefficient is determined. However, while it is theoretically proven equation for the standard deviations, it is an engineering postulate for the mpm-values. Re blocks 14, 15: It should be recalled that the procedure depicted in Figures C7.B.2 to C7.B.6 is aimed at estimating the extreme short-term response due to hydrodynamic loading only (see General Note 1). Therefore, the effect of wind should be excluded from the most probably maximum extreme static and dynamic responses in block 14 and 15, respectively. Wind is assumed to produce a static load and a static response, and not to influence the dynamic behavior. To determine the ultimate response the mean response due to wind should be determined separately and added to mpmeRs and mpmeRd. Notes to Figure C7.B.4 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 158 Mobile Jack-Up Units Rev 3, August 2008 Figure C7.B.5 Procedure for determining the mpm-factor of the static response COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 159 Mobile Jack-Up Units Rev 3, August 2008 Specific notes with Figure C7.B.5 Re blocks 9a and 9b: These standard deviations may be obtained from separate time domain simulations in the same manner as shown in Figure C7.B.2 (blocks 1 and 4) or, alternatively, from separate frequency domain analyses as shown in Figure C7.B.3 (blocks 1 and 4). The mean values are not required and neither is it necessary to subtract dynamic and static response time series or transfer functions, respectively. Re block 9c: The drag-inertia parameter is defined as the ratio of the magnitude of the drag force to the magnitude of the inertia force due to waves. All relationships given below are valid for the case of zero current, which is used as the basis for the whole procedure in view of the engineering approximations involved. For an element of a circular cylinder of diameter D and unit length, subjected to a periodic wave, the drag-inertia parameter then becomes: K = ( 1 2 ρ Cd D v2) / ( 1 4 Cm ρ π D2 a) = 2 2 Cd v πCmDa (1) Where v and a are the velocity and the acceleration normal to the element, respectively. As both v and a depend on the wave parameters (wave height, wave period, waterdepth) and the elevation at which the element is located, it is obvious that K is also a function of depth, waterdepth, wave height and wave period. therefore, the theoretical definition of K is only meaningful for Morison wave loading per unit length of the element. The definition of K can be generalized to random instead of periodic wave conditions by replacing the deterministic normal velocity v by the standard deviation of the random normal velocity σv and replacing the deterministic normal acceleration a by the standard deviation of the random normal acceleration σa. Equation (1) then becomes: K = 2 2 Cd v CmD a σ π σ (2) Using a statistical or least squares linearization procedure in the frequency domain, as developed by Borgman (see notes with Figure C7.B.3), it can be shown that for the wave force on an element of a single member the standard deviations of the two parts of the wave force are as follows: σR(Cm = 0) = 8 / x. 1/2 ρ Cd D.σv2 σR(Cd = 0) = ρ Cm.1/4 π D2.σa These relationships can be used to determine σv 2 and σa, which can then be substituted into equation 2 to result in: K = π σ 8 σ 0 0 . ( ) ( ) R Cm R Cd = = (3) With R being the wave force per unit length in a random sea. Equation (3) may subsequently be generalized to apply to any other local or global response R selected for interest. It will be clear that such a generalization is purely an engineering postulate and not founded on theoretical reasoning. It is an attempt to incorporate the important but unknown non-gaussian effects on the maximum response through the assumed similarity with the wave loading process for which the nongaussian statistics are known. Yet another way to determine the drag-inertia parameter K for a generalized response R is by using the kurtosis of R. The kurtosis is defined through the expected values of the second and fourth order moments of the time simulations of R, i.e.: κ = E {R4} / [E {R2}]2 (4) For Morison wave loading per unit length of member the relationship between K and the kurtosis k is (see Ref. 2 below): κ = 105 4 18 2 3 3 2 1 2 K K K + + ( + ) (5a) or in the inverse form: Notes to Figure C7.B.5 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 160 Mobile Jack-Up Units Rev 3, August 2008 K = ( ) ( ) ( ) κ κ κ − + − − ⎧⎨⎩ ⎫⎬⎭ ⎡ ⎣ ⎢⎢⎢⎢ ⎤ ⎦ ⎥⎥⎥⎥ 3 26 3 3 1 2 35 3 / 1/2 (5b) While K varies between 0 (inertia loading only) and infinity (drag loading only) κ ranges from 3 to 35/3. It may now be assumed that the same relationship holds for an arbitrary response variable R. Therefore, if the kurtosis of R is know the corresponding drag-inertia parameter K can be determined. If this is done, separate time domain simulations for the standard deviations in blocks 9a and 9b are not required but the route through block 93 cannot be followed. One enters the diagram in block 9c and must read CRs from Figure C7.B.6 as per block 9d. Both the kurtosis and the drag-inertia parameter may be subject to appreciable statistical variability and their determination may require time domain simulations of substantial length; see Ref. 2 below. Re blocks 9d and 9e: Figure C7.B.6 (referred to in block 9d) is equivalent to the figure that was derived by Brouwers and Verbeek and presented in Ref. 1 below as well as in Figure A1 of the SIPM - Practice (EP 89-0550). However, this latter figure presented the ratio of the expected value of the extreme to the standard deviation for a 1000 peaks, rather than the mpm-factor CR which is the ratio of the most probable maximum value of the response to the standard deviation, which is used in this report. Therefore, Figure C7.B.6 has been recalculated in accordance with Ref. 3 and now truly presents the mpm-factor CR. It should be noted that the figure is valid for a narrow band process, the corresponding ratios for a broad band process being somewhat smaller. Therefore, CR is a slightly conservative estimate for the mpm-factor. This is in accordance with the general principles underlying a simplified engineering method and is well within the accuracy of the overall procedure. An alternative and practical method to estimate K is to apply the engineering assumption for estimating the most probably maximum value of the dynamic response, as used in block 11 of Figure C7.B.4, to separate responses due to hydrodynamic drag loading only and inertia loading only, replacing RS from block 9 and Ri from block 10, respectively. These two hydrodynamic loading components are fully uncorrelated and so are the responses caused by them; hence the correlation coefficient r = 0. Further, the mpm-factor for a totally drag dominated Morison force is 8.0 and for a totally inertia dominated Morison force it is 3.7. With these substitutions the equation in block 11 of Figure C7.B.4 becomes: mpmR 2 = {8.0 σR (Cm = 0)}2 + {3.7 σR (Cd = 0)}2 For zero correlation the standard deviation of the overall response is obtained from the equation: σR 2 = {σR (Cm = 0)}2 + {σR (Cd = 0)}2 (see note with block 7 of Figure C7.B.4). These are the equations presented in block 9e. The comments made with regard to conservatism included in the route through block 9d remain equally valid here. Its determination in block 9c could therefore, strictly speaking be avoided. The input of KRs into block 93 of Figure C7.B.5 is symbolic, representing the implicit use through σRs (Cm = 0) and σRs (Cd = 0), resulting directly from blocks 9a and 9b. In practical applications it is recommended that both routes through block 9d and 93 are followed as a check on the calculations. Reference 1: J.J.H. Brouwers and P.H.J. Verbeek "Expected fatigue damage and expected extreme response for Morison-type wave loading" Applied Ocean Research, Vol. 5, No. 3, 1983, pp. 129-133 Reference 2: P.M. Hagemeijer "Estimation of drag/inertia parameters using time-domain simulations and the prediction of the extreme response" Applied Ocean Research, Vol. 12, No. 3, 1990, pp. 134-140. Reference 3: J.J.M. Baar Extreme values of Morison-type processes" Report EP 90-33365, October 1990. To be published shortly in Applied Ocean Research Notes to Figure C7.B.5 (cont.) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 161 Mobile Jack-Up Units Rev 3, August 2008 The equation for the curve is Ref. 3, Specific notes with Fig. C7.B.5 C A D C R = + 372 691 . / ( . )/ if C B K C B K R R < < < < ( . ) ( . ) 0135 0135 Where A, B, C and D are functions of k as follows: A = 3K2 + 1 B = 1 / ⎡(2K) (3K2 +1) ⎣ ⎢ ⎤ ⎦ ⎥ C = ⎡ (3K2 +1) / (2K) ⎣ ⎢ ⎤ ⎦ ⎥ D = 1/(8K2) Figure C7.B.6 Ratio CR of most probable maximum to standard deviation as a function of drag-inertia parameter K for N = 1000 peaks Figure C7.B.7 Comparison between the normalized spectra Sη(ω), Sφ(ω) and SPM(ω) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 162 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C7 1. Parker G.J. (1997), ‘Calibration of an SDOF-Based Dynamic Analysis Procedure Including Non-Linear Foundation Fixity’, Sixth International Conference The Jack-Up Platform, Design Construction and Operation, City University, London. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 163 Mobile Jack-Up Units Rev 3, August 2008 C8 COMMENTARIES TO ACCEPTANCE CRITERIA C8.0 BACKGROUND TO PARTIAL LOAD FACTORS C8.0.1 General Reliability analysis was used in the derivation of load effect factors which are conservatively presented in the PRACTICE as load factors. All factors associated with strength or resistance have been derived either from consensus (e.g. weight in overturning) within the JUWG or from other relevant codes (e.g. AISC LRFD). The philosophy used in the derivation of the load effect factors is discussed below. Further references on the technique etc. are given in [1], [2], [3] and [4]. C8.0.2 Fundamental Question When a jack-up is offered for operation at a marginal location, a number of issues such as overturning stability, soil capacity and leg strength are addressed to ascertain the fitness for purpose of the jack-up. In all these assessments, it is necessary to establish an acceptable safety margin (or safety factor) between load and resistance. The question is, how do we establish, quantitatively, the safety factor required for the performance assessment? C8.0.3 Solution Loads and resistances are not uniquely defined due to physical, statistical and methodological uncertainties. Acceptance of this fundamental principle has led to the understanding that the use of safety factors merely assists in maintaining a level of safety. Furthermore, the true goal of assessment is to achieve as consistent a level of safety as possible when the safety factors are just satisfied. This demonstrates the need to perform reliability analysis which would provide a framework to link the safety factors to the safety levels. The various key stages of the analysis are described below: C8.0.3.1 Probabilistic Description of Input The code calibration project was performed in two stages. In Stage 1, sensitivity studies were performed to identify the key parameters which influence the response of a jack-up [5], [6]. These showed that significant wave height (Hs), peak period (Tp), drag diameter (CDD), tidal current (VT) and the permissible interaction ratio for structural elements were important items. The reliability studies, [2], showed that the significance of Tp, CDD and VT was not critical and therefore the variability in these parameters was ignored in Stage 2 studies, [3]. However, it was clear that the largest value of the responses varied between different realizations of the same seastate and it was therefore necessary to account for this variability. Thus in the final stages of the study, Hs, the variability in the largest value in a storm and the permissible interaction ratio were considered as variables. The following table summarizes the variables and associated probability distributions used in Stage 2 studies [3]: Parameter Distribution Significant Waveheight, Hs Largest value in a storm Permissible Interaction Ratio Gumbel Poisson Log-normal COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 164 Mobile Jack-Up Units Rev 3, August 2008 C8.0.3.2 Limit States Three limit states, namely, overturning, preload and leg strength were considered. These limit states are recognized to possess some degree of reserve of safety from actual failure. As the PRACTICE is focused upon component failures, and target safety levels were determined from average safety levels of exemplary rigs (see section C8.0.3.5 below), reaching any of the selected limit states does not indicate "true" failure. This is not significant to the code calibration. C8.0.3.3 Response Model A major objective of the JUWG has been to develop as comprehensive an analysis method as possible which reflected the behavior of jack-ups in the elevated condition. The developed method was applied to derive the response parameters required for the reliability analysis. It must be noted that time domain analysis was performed in order to properly capture all the non-linearities in jack-up loading and response. The following table summarizes the key facts associated with the simulations and analysis methodology: • 0.5s time step used in simulations • 3 hour simulations used for MPM • 1 hour simulations with correction for response surfaces • Hs increased by factor [1 + 0.5e(-d/30)]* • 75% of max. variable load used in reliability analysis • P-Δ effects included • Hull Sag and Flexibility included • Pinned Foundations • Initial leg inclination included in leg strength evaluation . • Relative velocity Morison's equation used • 4% critical damping (plus damping from above) • Jonswap spectrum used • Winterstein [7], Juncher Jensen [8] used for MPM . This is changed to [1 + 0.5e(-d/25)] in the current draft of the PRACTICE. The following response model, which linked Hs to the safety index (or probability) of exceeding the given limit state in that Hs was derived from three simulations with different but large (near 50-year return) Hs: β = A + B.Hs + C.Hs 2 Once this link was established, then using the probability distribution of the annual extremes of significant wave height, the probability of limit state exceedance in any one year (or the annual safety index) was computed. C8.0.3.4 Safety Index vs. Safety Factor By repeating the procedures described in C8.0.3.3 for different values of the resisting quantities such as righting moment, permissible interaction ratio and preload a rig/location specific link between safety factor and safety index was generated (e.g. see Figure C8.0.1). This then permitted the evaluation of the required safety factor for a specified level of safety. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 165 Mobile Jack-Up Units Rev 3, August 2008 C8.0.3.5 Reference or Target Safety Level No absolute target or reference safety level was imposed. Instead, the four rig/location combinations which were, on average, considered to be close to the limit were analyzed using reliability techniques and the target safety level obtained by averaging the individual safety levels achieved by each rig. This process is described graphically in Figure C8.0.1. The process was repeated for each of the limit states considered. It is not possible to directly compare safety levels achieved by the exemplary rigs with safety levels of other offshore structures. However, the safety levels achieved are broadly comparable. Figure 8.0.1 : Link between safety factor and safety index (β) C8.0.3.6 Derivation/Calibration of Safety Factors As noted in section C8.0.3.5, four exemplary rig/location combinations were analyzed using reliability techniques. The reliability analysis was further extended to tropical cyclone locations by simply modifying the statistical distribution of the environmental parameters to reflect the greater variability. The spread in the safety index vs. safety factor curves was shown to be due to the varying levels of dynamicity of the four different rig/location combinations and the environmental variability between North Sea and tropical cyclone locations. The response quantities were split into quasi-static and dynamic components in order to investigate the potential for reducing the spread in safety levels across rigs and locations. The objective of the optimizing function was to minimize the squared difference between the achieved safety index and the target safety index. This approach did show a reduction in spread of safety levels with the use of partial factors, however, as the initial safety index spread itself was small, the decision was taken to adopt a single load factor which minimized the spread whilst maintaining the target safety level as discussed in section C8.0.3.5. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 166 Mobile Jack-Up Units Rev 3, August 2008 C8.1 STRUCTURAL STRENGTH CHECK C8.1.1 Introduction Code Basis Currently, the most widely used codes for structural strength assessment for the offshore industry are based on "working stress design". Examples of commonly used codes are AISC ASD [9] and API RP2A [10]. Due to a number of inadequacies of these codes, there has been a move by their authors to replace them with the "Load and resistance factor design (LRFD)" approach. Although AISC and API allow use of both the "working stress" and LRFD codes in parallel, it is their intention to phase out the "working stress" methods in the future. To follow the trend in the industry, it was decided that the structural strength assessment code to be used in the PRACTICE should also be based on LRFD. Both the AISC LRFD [11] and API LRFD [12] codes were reviewed as bases for jack-up structural assessment. It was decided that the AISC LRFD should be used as the basis for the PRACTICE, for the following reasons: i) API LRFD covers tubular members thoroughly but refers the user to AISC LRFD for non-tubular members. Since non-tubular members are commonly encountered in jack-ups, AISC LRFD offers the greater applicability. ii) Although a limit state code, the equations used in API LRFD are expressed in terms of stresses and not loads. This would cause difficulties in the integration of AISC LRFD with API LRFD for use in assessment computer programs for the nontubular cases (see (i)). iii) A parametric study of the two codes for tubular members produced results for the AISC LRFD equations (including the η exponent discussed below) similar to those for the API LRFD code. For analysis of a structure using the LRFD approach, it is necessary to define the structure more comprehensively. Certain characteristics which occurred in jack-up structures which could be fitted in with the AISC "working stress" codes had to be dealt with specifically for AISC LRFD. Whether the treatment of these characteristics was correct in the AISC "working stress" code was doubtful and hence the use of LRFD has not created additional problems but has highlighted inadequacies of the previously accepted codes. Particular points of concern include local buckling limit states, hybrid beam-columns and biaxial bending. For the PRACTICE it was desirable to produce a code simple to use, unambiguous and as close as possible to AISC LRFD to avoid the need for validation. Except for the sections on shell members, the code uses the same equations as given in AISC LRFD apart from two areas of extension, relating to beam-column biaxial bending and hybrid beam-columns, discussed below. For instance, the same ranges of D/t ratios have been used as specified in AISC to define the different ranges of limit state. These ranges may not be instantly recognizable since they been given in terms of R/t ratios in many places. This is considered more appropriate for jack-up members which may contain partial tubular sections for which a section radius is a more meaningful quantity than a diameter. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 167 Mobile Jack-Up Units Rev 3, August 2008 Most sections are drawn from the numerous chapters and appendices in AISC LRFD and are placed in a logical sequence. In some cases it has been necessary to interpret which equations are applicable especially in the area of local buckling for beamcolumns. AISC LRFD does not cover very high D/t ratio tubes and tubes with stiffeners, so reference has been made to relevant sections of a different code. The "DNV Rules for Classification - Fixed Offshore Installations" [13] was selected as the most suitable, since this is a limit state code. This document refers the user to "DNV Classification Notes - Note 30.1" [14] for obtaining member resistances or strengths. Some guidance on the use of these notes is given in section C8.1.5. Hybrid beam-columns Hybrid beam-columns are quite common in jack-ups such as chords with high yield stress racks welded to lower yield stress plate constructions. The treatment of hybrid beams of this nature is not adequately covered in AISC LRFD and hence it has been necessary to state rules dictating the method for establishing the axial and bending strengths of such beam-columns. The methods described are based upon engineering understanding of the problem and have been made as straight forward as possible. Limitations The first limitation, (a) has been stated as a warning that the code given in the PRACTICE must be restricted to the type of geometries as described in section 8.1.4. The intention has been to cover all of the geometries likely to be encountered in jackups although there may be some exceptional cases. If this is so, the user must refer to AISC LRFD [11]. One notable exception could be 'I' type sections which are sometimes used in jack house frames. Since AISC LRFD is oriented towards the assessment of 'I' type sections, it is reasonably straight forward to use. It is recommended that the equations given in Appendix H are used for 'I' sections since these should give less conservative results than the general equations in Chapter H. The limitation (b) is stated in AISC LRFD [11] for the reasons that experimental validation has not been carried out for steels with higher yield stresses than 100 k.s.i. The equations may not be valid for higher yield stresses although there does not appear to be any theoretical reason for this to be the case. However, if higher yield stress steels are to be assessed using the practice, it will be necessary to validate the equations for whatever yield stress is used in the design. Currently steels with yield stresses greater that 100 k.s.i. are not generally encountered in jack-ups with the exception of the mechanical components in the holding system which are to be treated under other assessment criteria. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 168 Mobile Jack-Up Units Rev 3, August 2008 C8.1.2 Definitions Structural Members and Components The definitions of members and components have been stated so that the appropriate analysis method can be used for a particular type of geometry. The emphasis of the assessment is on structural members, for which loads and properties must be known. Components are assessed only when the section is identified as being prone to local or lateral torsional buckling. This type of specification is in keeping with conventional jack-up analysis procedures in which chord scantlings are modeled as single beams; the modeling of the individual plates not being necessary. C8.1.3 Factored Loads The load factors used in AISC are inappropriate for jack-up analysis since these have been derived for land based buildings. The derivation of load factors specific to jackups is discussed in Section C8.0. C8.1.4 Assessment of Members - excluding stiffened and high D/t ratio tubulars C8.1.4.1 General interaction equations The treatment of biaxial bending in AISC LRFD tends to be conservative for beamcolumns laterally supported at both ends. This is most apparent when assessing a tubular member. The bending strength of the tube must be the same in all directions, but this is not reflected in the AISC LRFD equations. The linear addition of x- and yaxis bending moment terms in effect reduces the nominal bending strengths in all cases of biaxial bending. For example, a tubular member subject to bending in a plane at 45° to the x-axis has in the AISC LRFD code a nominal strength of 71% of that for uniaxial bending in the x- or y- planes. The problem is not confined to tubulars, as most sections would have a reduction in nominal strength on account of this linear addition. Only for `I' sections does AISC LRFD allow a more liberal formulation. In the AISC ASD formulation, such a problem does not arise, as the stress points are considered explicitly. Since optimal design is required for jack-ups, and since previous ASD-based design did not suffer from this problem, it was considered necessary to remove the conservatism for the PRACTICE. The general interaction equations have therefore been modified from the AISC LRFD equations. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 169 Mobile Jack-Up Units Rev 3, August 2008 In deriving a suitable form the problem for the tubular was considered first. Clearly, since the tubular has equal bending strength in all directions, the correct actual bending moment should be the vectorial sum of the x- and y-axis bending moments. Expressed as a unity check equation for bending only: M M M M ux b nx uy b ny φ φ ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ≤ 2 2 10. and with the addition of axial load (for Pu/φaPn > 0.2) P P M M M M u a n ux b nx uy b ny φ φ φ + ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ≤ 8 9 10 2 2 1 2 . Since most jack-up chords are closed sections with high torsional stiffnesses similar to tubulars, the logical step was to formulate a similar equation which had the ability to account for sections not exhibiting circular symmetry. This was carried out by using a generalized exponent η to form the two equations given in the PRACTICE. One of the equations is given below as an example (for Pu/φaPn > 0.2). This resembles the formulation in the AISC LRFD for I sections, although the exponent η has a different determination procedure. P P M M M M u a n ux b nx uy b ny φ φ φ η η η + ⎧⎨⎩ ⎫⎬⎭ + ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ≤ 8 9 10 1 . With η = 1.0, the equations revert to the standard AISC LRFD equations, and hence a conservative assessment can be made. However, if the limit is required with more accuracy, then it is necessary to determine the value for η (discussed later). If the nominal bending strengths Mux and Muy are the same and η = 2.0, then this would imply that the section has equal bending strength in all directions. A value to η = ∞ implies that the bending capacities in the x- and y-axes are independent of each other. Favorable interaction between, for example, the -Mx and +My moments acting on triangular chords with a single rack cannot be reproduced by the above equation. In such cases recourse to the section-specific interaction surface is recommended (see Section C8.1.4.7). COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 170 Mobile Jack-Up Units Rev 3, August 2008 C8.1.4.2 Nominal Axial Strength C8.1.4.3 Whereas the nominal axial strength of tension members of one material are fully catered for in the AISC LRFD code, some interpretation was required hybrid beamcolumns. The basic measure of tensile strength is 0.9Fyi, but in certain cases this value may be unacceptably close to the ultimate strength. Therefore the provision is introduced that the factored strength is the lesser of 0.9Fyi and 0.75Fui. This ensures that an acceptable margin is applied to each component as illustrated in Figures C8.1.1 and C8.1.2. Figure C8.1.1 : ultimate strength Figure C8.1.2 : yield strength much bigger than yield strength close to ultimate strength For hybrid members a nominal strength is required that takes into account the properties of each component. If there is no likelihood of fracture of any one component then an addition of the nominal strengths of each component is appropriate for the member (Figure C8.1.3.). Figure C8.1.3 : Stress/strain curves for two component member for which addition of nominal strengths is permissible COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 171 Mobile Jack-Up Units Rev 3, August 2008 However it is conceivable that fracture of one component may take place at a strain level below that at which another component is loaded to its nominal strength (Figure C8.1.4.). Figure C8.1.4 : Stress/strain curves for two component member in which one component fractures before the other is loaded to its nominal strength. For such an eventuality it is stipulated that the strength of the whole section is that for the weakest component, applied across the whole section, so that: Pn = FminΣAi This formulation is suitable when component materials are similar. When material properties differ widely from component to component then the formulation may be over conservative, and a rational analysis may be preferred. An example follows. Example Consider a member in tension. The section consists of a rectangular portion of steel 1 sandwiched between two rectangular portions of steel 2. The areas occupied by steels 1 and 2 are both half the total section area A. By symmetry the section is balanced. Figure C8.1.5 : Stress/strain curves for components of example member COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 172 Mobile Jack-Up Units Rev 3, August 2008 Consider the portion of steel 1 as component 1 and the portions of steel 2 as component 2. The stress/strain plots of the materials (Figure C8.1.5.) show that the strain level for component 1 to reach its nominal strength is well below that for fracture of 2. The ductility of 2 means that the component can support a stress of just over Fn2 for strains up to those at which component 1 reaches its nominal capacity. Therefore, a less conservative nominal strength for the member is: Pn = Fn1A/2 + Fn2A/2 Because the section is balanced, plastic deformation of 2 does not induce any extra loads or moments on the member. Were the section not balanced, then this would not be true. It is essential that such aspects are considered in a rational analysis of strength. C8.1.4.4 Effective Applied Moment C8.1.4.5 The PRACTICE allows for structural analyses of a range of levels of sophistication. In some, it may be necessary to manipulate the calculated moment to produce a more "true" value for application in the PRACTICE. This leads to the use of the effective applied moment for members with compressive axial loads. Adjustments for tensile axial loads are not considered significant. It has been noted that the P-Δ effect produces an extra moment on a leg under hull sway, and that this moment should be included in the structural analysis. The similar, local P-Δ effect on the individual members of truss leg must also be included, directly in the structural analysis, or by use of the B term. If for a truss, the structural analysis includes the local P-Δ effect then no manipulation is required. If the local P-Δ is not included, for example through a linear elastic analysis of the leg segment, then the amplifier B is required. For many non-truss leg cases there is no local P-Δ effect, such as for a jack-up with large diameter tubular legs. The use of the single B term differs from that in the AISC LRFD code. There, the first order moment is separated into two parts: a moment assuming no lateral deflection of the frame Mnt, and a moment attributed only to lateral deflection Mlt. Then the effective applied moment is the sum of B1Mnt and B2Mlt, where B1 is similar to B in the PRACTICE and B2 is a second coefficient. It is important to note that both these moments are first order, and do not include P-Δ. The use of B1 and B2 is to simulate the P-Δ effects at local and global level respectively. Therefore, in the PRACTICE the calculated applied moment is not the same as the Mu in the AISC LRFD code. The use of Mue = B Mu performs the necessary step of adding the local P-Δ moment to the calculated moment which already includes global P-Δ. Note that in a plastic analysis, yielding can take place within the members and bending moments can hence be redistributed. The types of analysis to be used for the structural assessment of jack-ups are to be elastic analyses where yielding does not take place, so this aspect is not covered. For reference, AISC LRFD states their code is only valid for plastic analysis if material yield stresses do not exceed 65 k.s.i. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 173 Mobile Jack-Up Units Rev 3, August 2008 C8.1.4.6 Nominal Bending Strength The calculations of nominal bending strength for compact and noncompact sections require knowledge of the plastic moment capacity of the section. For a section composed of uniform material this is given by the lesser of: Mp = FyZ and Mp = 5/6FuZ where Z is the plastic section modulus. For hybrid sections there is more than one set of material properties to consider. Standard techniques are recommended for evaluation of Mp and an example is provided below. Example Consider the simplified problem of a square rack section (component 1) of properties: Fy1 = 700 MN/m2 Fu1 = 828 MN/m2 ; Fy' = 828 x 5/6 = 690 MN/m2 connected to a solid square chord section (component 2) of properties: Fy2 = 345 MN/m2 Fu2 = 485 MN/m2 ; Fy' = 485 x 5/6 = 404 MN/m2 as shown in Figure C8.1.6 below. The nominal strengths are the lesser of the Fyi and 5/6Fui, namely: component 1 strength = 690 MN/m2 component 2 strength = 345 MN/m2 Dimensions are as marked. Figure C8.1.6 Example Figure C8.1.7 Fully plastic hybrid chord section stress distribution On the assumption that the strain for component 1 to be loaded to its nominal strength is not sufficient to lead to fracture of component 2, the plastic stress distribution for pure bending is as shown in Figure C8.1.7. The Plastic Neutral Axis is a distance zo from the back face of the chord component, such that: 345 x 0.3 x zo = 345 x 0.3 x (0.3-zo) + 690 x 0.1 x 0.1 i.e. zo = 0.183 m The section plastic moment is then: Mp = 345 x 0.3 x 0.183 x (0.183/2) + 345 x 0.3 x 0.117 x (0.117/2) + 690 x 0.1 x 0.100 x (0.117 + 0.100/2) = 3.59 MNm COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 174 Mobile Jack-Up Units Rev 3, August 2008 C8.1.4.7 Determination of η Determination of the correct value of η is carried out by calculation of the nominal strength of the member about axes other than the x- and y-axes. This can be done in the normal manner based on the effective plastic section modulus with reductions for local buckling if applicable. Although a beam will not necessarily bend in the same plane as the applied moment when the bending plane is at an angle to the orthogonal axes, it is not expected that the capacity will be greatly affected. Once the nominal bending strength has been calculated for a few angles between the xand y-axes, the value for η can be calculated using the graphical procedure given in the practice, or by an iterative procedure. A successful iterative procedure was found to be by the use of the coupled equations, setting a = M'uex/Mnx and b = M'uey/Mny: ηi+1 = 1 1 1 n( b ) na − ηi with the accelerating step: ηi+2 = 0.5(ηi+1 + ηi) and the initial value η = 1.5. The three angles which were chosen, 30°, 45° and 60° give a good spread over the 90° range. It is not the intention to fit a curve through all the values from the three angles but merely find the lowest value to η. This may still make the equation conservative although considerably less so than for η = 1.0. Plastic Interaction Curve Approach Alternatively, interaction equations and curves for generic families of chords are presented in Figures C8.1.8 - C8.1.11. The offset distance between the elastic centroid (used in the structural analysis) and the 'center of squash', together with other geometric data for the members of each family of chord is presented in Tables C8.1.1 to C8.1.4. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 175 Mobile Jack-Up Units Rev 3, August 2008 C8.1.5 Assessment of Members - other geometries For high D/t ratio tubulars, reference is made to the DNV Rules for Fixed Offshore Installations, as these are based on a suitable LRFD format. Care must be taken to adapt the usage factors in the Rules to the correct resistance factor format. The buckling strength of shells is best described in terms of buckling stress. For this reason, the stress to cause buckling in the shell must be determined and compared with the stresses caused by the factored loads. Since the analysis model usually gives the overall member loads, it is necessary to calculate the stresses in the shell. It may be possible, with caution, to allow the analysis model to also calculate membrane stresses. The detailed stress formulations in the DNV Class note 30.1 are amenable to some simplification. For example, the pressure loading terms may usually be omitted, since high D/t tubulars in jack-up legs are generally flooded. For beam-column interaction, the effects from global axial buckling are added to the effects of local buckling due to flexural bending. Global buckling effects in bending such as lateral-torsional buckling only occur in sections in which the stiffness out of plane is less than the stiffness in the plane of bending. Thus tubular and rectangular sections, hollow or otherwise, in which the depth is less than or equal to the width do not suffer lateral torsional buckling. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 176 Mobile Jack-Up Units Rev 3, August 2008 Strength Interaction Equations M M M M x px y py ' ' . / ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ≤ 2 2 1 2 100 For (P/Py) ≤ 0.6: M'px = Mpx cos . . . π P Py 2 0 7 ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ M'py = Mpy cos . . . π P Py 2 11 ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ For (P/Py) > 0.6: M'px = 1.71Mpx 1− ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ P Py M'py = 1.39Mpy 1− ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ P Py Figure C8.1.8 Interaction equations/curves for tubular chords with double central racks. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 177 Mobile Jack-Up Units Rev 3, August 2008 Chord Dimensions - Tubular Chord with Central Double Racks All dimensions are in millimeters, Yield Stresses are in MPa <--- Yield ---> Stress Design L1 t1 L2 t2 D t3 Fy1 Fy2 Fy3 Bay Ht BMC JU-300-CAN (Zapata Scotian) 991 127 0 0 914 44 690 0 690 5532 48 CFEM T2001 (Hitachi Redesign) 960 18 121 140 960 52 690 690 690 4500 Btm 3 bays 34 4100 Top 3 bays 26 4050 Middle bays 34 42 CFEM T2005 650 20 108 140 800 28 700 685 650 or 5050 30 700 31 32 33 35 36 38 40 700 685 700 44 34 700 685 650 38 42 * Note: Early CFEM T2005 designs use 650 MPa steel for tube, later designs use 700 MPa steel. …continued Table C8.1.1 Data for tubular chords with double central racks COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 178 Mobile Jack-Up Units Rev 3, August 2008 <--- Yield ---> Stress Design L1 t1 L2 t2 D t3 Fy1 Fy2 Fy3 Bay Ht CFEM T2600 650 20 120 140 800 33 700 700 700 6000 35 38 40 41 43 45 47 49 50 51 52 55 56 57 58 MODEC 200 450 15 102 127 559 27 490 690 490 5486 27 MODEC 300 450 25 102 127 559 34 490 690 490 5486 28 34 15 40 20 40 27 40 60 40 115 40 MODEC 400 (Trident 9) 690 20 102 127 800 30 490 690 490 6200 20 35 35 35 Hitachi K1025/31/32 900 18 100 127 900 32 690 690 690 5160 18 36 18 50 20 40 20 42 Hitachi K1026 (Neddrill 4) 950 18 100 127 950 32 690 690 690 4360 18 36 20 42 Hitachi K1056/7 1000 28 130 178 1000 47 690 730 690 4600 30 50 30 52 30 60 30 64 60 60 60 64 4000 ETA Robray 300 (Asia Class) 627 10 127 127 762 22 690 690 690 5486 11 13 14 16 17 19 25 32 ETA Europe Class 627 38 140 140 762 22 690 690 690 5486 51 64 76 89 102 114 127 Table C8.1.1 (Continued) Data for tubular chords with double central racks COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 179 Mobile Jack-Up Units Rev 3, August 2008 Strength Interaction Equations M M M M x px y py ' ' . / ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ ≤ 2 2 1 2 100 where; M'px = Mpx ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − 2.25 1 y P P M'py = Mpy ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − 1.85 1 y P P Figure C8.1.9 Interaction equations/curves for split tubular chords with opposed central racks (doubly symmetrical) COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 180 Mobile Jack-Up Units Rev 3, August 2008 Chord Dimensions - Split Tubulars with Double Central Racks All dimensions are in millimeters, Yield Stresses are in MPa Yield Stress Design L1 t1 D t2 t3 L4 t4 Y1 H1 H2 Fy1 Fy2 Bay Ht F & G L780 (Lower bays) 400 152 381 25 25 0 0 0 191 165 621 690 3658 F & G L780 (Upper bays) 400 127 381 25 25 0 0 0 191 191 621 450 3658 F & G L780 m2 (Lower bays) 400 152 381 32 32 0 0 0 191 165 621 690 3658 F & G L780 m2 (Upper bays) 400 127 381 32 32 0 0 0 191 191 621 517 3658 F & G L780 m5 (Monitor) 401 178 381 81 57 0 0 51 178 178 690 690 4267 F & G L780 m5 (Monarch) 401 178 381 81 51 0 0 51 178 178 690 690 4267 F & G L780 m6 611 178 584 83 38 0 0 95 292 292 690 690 5486 MSC CJ62 (Lower bays) 650 210 600 65 48 0 0 75 270 270 690 690 6927 MSC CJ62 (Upper bays) 650 210 600 55 40 0 0 75 270 270 690 690 6927 MSC CJ50 (1) 550 210 520 25 25 0 0 0 260 260 690 690 5608 MSC CJ50 (2) 550 210 520 25 35 0 0 0 260 260 690 690 5608 Technip TPG 500 (1) 722 160 680 75 61 0 0 20 340 340 690 540 6000 Technip TPG 500 (2) 722 160 680 75 37 0 0 55 340 340 690 540 6000 Technip TPG 500 (3) 722 160 680 62 37 0 0 36 340 340 690 540 6000 Technip TPG 500 (4) 722 160 680 58 37 0 0 30 340 340 690 540 6000 Technip TPG 500 (5) 722 160 680 50 37 0 0 19 340 340 690 540 6000 Technip TPG 500 (6) 722 160 680 50 37 510 30 19 340 340 690 540 6000 Table C8.1.2 Data for split tubular chords with double central racks COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 181 Mobile Jack-Up Units Rev 3, August 2008 Strength Interaction Equations M M M M x px y py ' ' . / ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ ≤ ξ ξ 1 ξ 100 where; M'py = Mpy 1 1 45 − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ P Py . When Mx ≥ 0: ξ = + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟+ ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ 18 2 7 28 5 6 2 3 . . . . P P P P P P y y y and M'px = Mpx 1 112 1 112 − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫⎬ ⎪ ⎭⎪ P Py . / . When Mz < 0: ξ = 1.8 and for (P/Py) ≤ 0.25: M'px = -Mpx for (P/Py) > 0.25: M'px = -Mpx 1 075P 1 3 1 45 − − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭ ⎪ P y . . Figure C8.1.10 Interaction equations/curves for tubular chords with offset double racks. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 182 Mobile Jack-Up Units Rev 3, August 2008 Tubular Chords with Offset Double Racks All dimensions are in millimeters, Yield Stresses are in MPa <--- Yield ---> Stress Design D t1 L1 L2 t2 t3 Fy1 Fy2 Fy3 Bay Ht Yena Ycos E Levingston 011-C 914 29 305 906 127 0 483 621 0 4826 84 100 16 33 75 90 15 Levingston 111 1016 32 305 1047 127 0 690 690 0 4877 73 73 0 35 68 68 0 Mitsui JC-300 (Key Hawaii) 1016 32 305 1046 127 0 690 690 0 5650 78 78 0 34 0 35 66 66 0 Mitsui 1-off (Key Bermuda) 1016 29 305 1046 127 0 690 690 0 4672 0 Most of leg 1016 29 305 1046 127 0 690 690 0 5050 0 Towage Section 32 5050 73 73 0 " 36 5050 66 66 0 " Hitachi Drill-Hope 762 30 190 882 127 0 690 690 0 5500 57 57 0 32 55 55 0 Hitachi C-150 (Ile Du Levant) 762 30 190 890 130 0 690 690 0 5500 60 60 0 Hitachi K1040/44/45 900 30 300 882 127 0 690 690 0 4800 77 77 0 Btm 2 bays 30 5090 77 77 0 Rest of leg 35 5090 42 5090 60 60 0 Hitachi K1060 (Sagar Lakshmi) 900 30 300 854 127 13 690 690 690 5260 84 84 0 31 0 32 0 34 77 77 0 Robco 350-C 876 29 292 881 127 0 690 690 0 5461 83 83 0 Btm 3 bays 876 38 68 68 0 " 864 29 89 89 0 Rest of Leg 864 32 82 82 0 " Table C8.1.3 Data for tubular chords with offset double racks COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 183 Mobile Jack-Up Units Rev 3, August 2008 Strength Interaction Equations M M K M M K M M x px px px y py / ' / ' . / − − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ ≤ ξ ξ 1 ξ 100 where; K P P P P P P y y y = − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ 08 04 0 4 2 3 . . . and M M P py py P y ' . = − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ 1 2 1 When (Mx/Mpx) ≥ K: M M P px px P y ' . = − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ 1 1 45 and ξ = 1.45 When (Mx/Mpx) < K: M M P px px P y ' . / . = − − ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ⎧ ⎨ ⎪ ⎩⎪ ⎫ ⎬ ⎪ ⎭⎪ 1 1 04 1 1 04 and ξ = 145 235 4 7 2 . + . . ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ + ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ P P P P y y Figure C8.1.11 Interaction equations/curves for triangular chords with single racks COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Chord Dimensions - Triangular Chords with Single Rack All dimensions are in millimeters, Yield Stresses are in MPa <-------- Yield Stress --------> Design L1 t1 L2 t2 L3 t3 L4 t4 L5 t5 t6 X1 Y1 Y2 Y3 Fy1 Fy2 Fy3 Fy4 Fy5 Bay Ht Yena Ycos E MarLet Standard (3/4" side plates) 711 51 466 19 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 259 279 20 MarLet Standard (7/8" side plates) 711 51 466 22 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 259 279 20 MarLet Standard (1" side plates) 711 51 466 25 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 260 279 19 MarLet Standard (1.5" side plates) 711 51 466 38 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 262 279 17 MarLet Standard + side stiffeners 711 51 466 19 213 127 0 0 127 25 0 236 457 0 211 483 483 587 0 483 3408 260 279 19 MarLet Std 116 (1"x4" rack stiffeners) 711 51 466 19 213 127 102 25 0 0 0 236 457 524 0 483 483 587 483 0 3408 278 296 18 MarLet 116 North Sea (1"x4"+1"x12" stifnrs) 711 51 466 19 213 127 102 25 305 25 0 236 457 524 118 483 483 587 483 483 3408 276 291 15 MarLet 116 (1"x4"+1.5"x12" stifnrs) 711 51 466 19 213 127 102 25 305 38 0 236 457 524 124 483 483 587 483 483 3408 277 291 14 MarLet 116 Juneau (2"x4"+1"x12" stifnrs) 711 51 466 19 213 127 102 51 305 25 0 236 457 524 118 483 483 587 483 483 3408 290 304 14 MarLet Gorilla (150-88) 813 76 573 57 222 140 0 0 0 0 0 248 600 0 0 483 483 620 0 0 5113 302 323 21 MarLet Super 300 813 76 607 38 222 140 0 0 0 0 0 268 600 0 0 483 483 620 0 0 5113 298 323 25 813 76 607 38 222 140 0 0 305 51 0 268 600 0 296 483 483 620 0 483 5113 327 346 19 MarLet 300 Slant 711 64 441 38 213 127 0 0 0 0 0 218 457 0 0 414 414 414 0 0 2556 245 245 0 LeTourneau 150 (3/4" side pl) 711 51 466 19 213 127 0 0 0 0 0 236 457 0 0 414 414 620 0 0 2556 259 302 43 LeTourneau 150 (1.125" side pl) 711 51 466 29 213 127 0 0 0 0 0 236 457 0 0 414 414 620 0 0 2556 259 303 44 LeTourneau 150 (1.5" side pl) 711 51 466 38 213 127 0 0 0 0 0 236 457 0 0 414 414 620 0 0 2556 262 298 26 LeTourneau 46,47 559 44 432 13 178 89 0 0 0 0 0 166 432 0 0 ? ? ? 0 0 3408 224 224 0 LeTourneau 4,9 559 51 565 13 197 102 0 0 0 0 0 178 533 0 0 ? ? ? 0 0 3430 286 286 0 Mitsubishi MD-T76J 750 50 574 25 225 125 0 0 0 0 0 226 575 0 0 687 687 687 0 0 3456 315 315 0 Gusto 1-off: (Maersk Endeavour) 800 60 592 30 283 127 0 0 0 0 0 359 443 0 0 620 620 620 0 0 4800 284 284 0 800 90 534 40 283 127 0 0 0 0 0 331 443 0 0 620 620 620 0 0 4800 255 255 0 800 110 488 50 283 127 0 0 0 0 0 307 443 0 0 620 620 620 0 0 4800 244 244 0 Gusto 1-off: (Maersk Explorer) 800 76 535 38 279 127 0 0 0 0 0 337 453 0 0 690 690 690 0 0 4539 268 268 0 800 64 549 38 279 127 0 0 0 0 0 344 453 0 0 690 690 690 0 0 4539 282 282 0 800 51 562 32 279 127 0 0 0 0 0 351 453 0 0 690 690 690 0 0 4539 297 297 0 800 51 562 29 279 127 0 0 0 0 0 351 453 0 0 690 690 690 0 0 4539 297 297 0 BMC 1-off design (Trident 7) 711 38 356 19 279 127 0 0 0 0 25 264 204 0 0 ? ? ? 0 0 3353 197 197 0 Table C8.1.4 Data for triangular chords with single racks Commentaries to Recommended Practice for Site Specific Assessment of Page 184 Mobile Jack-Up Units Rev 3, August 2008 COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 185 Mobile Jack-Up Units Rev 3, August 2008 C8.3 FOUNDATION ASSESSMENT The intention of the foundation capacity checks of steps 1 and 2 (Sections 8.3.1 and 8.3.2/8.3.3 of the PRACTICE) is to safeguard against foundation failure. Foundation failure will, in most cases, manifest itself through excessive spudcan vertical and/or horizontal displacements which may cause local or global instability of the jack-up. Local instability occurs when a leg becomes overstressed, with global instability as a consequential effect. Global instability may occur through overturning which will then cause leg overstress. The key to preventing either type of failure mode is to safeguard against excessive spudcan displacements. Since it is difficult to accurately compute the displacements (as proposed in Step 3, Section 8.3.4 of the PRACTICE, the checks of steps 1 and 2 are performed by comparing the bearing capacity with the extreme combinations of load, including applicable partial factors. In steps 1 and 2a the loads are computed assuming pinned footings. In step 2b the check allows for fixity. Selection of the Resistance Factors φ The resistance factor φ is intended to cover uncertainties in the estimation of the bearing capacity. In foundation engineering it is common to adopt φ in the range 1/1.25 - 1/1.30 (0.80 - 0.77) when the capacity is determined on the basis of available soil data and analytical predictions. For a jack-up there is however additional information available in terms of the preload applied at installation, which generally justifies the use of a higher resistance factor. During preloading the spudcan foundation experiences loading similar, but not identical to the conditions of the leeward leg during the extreme event. Taking this information into account, there is greater certainty in the upper part of the bearing capacity curve applicable to bearing failure than in the lower part applicable to sliding failure. However, some uncertainty still remains for the foundation capacity in bearing applicable to the leeward leg determined from the preload value. This uncertainty is due to factors such as: - effect of cyclic loading - effects of consolidation and creep - loading rate effects There is at present insufficient information available to fully quantify the likely distribution in the actual foundation capacity curve. In the study performed by NGI [17] it is concluded that cyclic degradation effects on clay are significantly larger for the leeward leg than for the windward leg. It is also noted that the case of a spudcan which has not penetrated sufficiently to mobilize the maximum available bearing area should be differentiated from the case where the maximum bearing area is utilized. This is because in the former case a small additional penetration will lead to a increase in capacity as a result of the increase in bearing area. On the basis of the above arguments the following resistance factors are proposed: Step 1a - preload, vertical load alone: φ = 0.9 See note overleaf COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 186 Mobile Jack-Up Units Rev 3, August 2008 Note: Section 8.3.1.4 of the PRACTICE requires that the vertical and horizontal load check of step 2a is made when the horizontal leg reaction at the leeward leg exceeds prescribed limits, depending on the penetration and soil. This is because the simplistic check in Step 1a is based on the proven ultimate vertical bearing capacity during preloading and it is therefore assumed that the extreme footing load is the same as the maximum footing load during preloading. This implies that the horizontal loading on the spudcan under extreme conditions is small and it is therefore appropriate to limit the combined horizontal and vertical loading to the values permitted under Step 2. In the selection of the limits for Step 1a two penetration cases can be distinguished: - full embedment to maximum bearing area in foundation layer, - partial embedment in the foundation layer. For full spudcan embedment in sand the lateral soil resistance at a vertical load of 0.9VLo is approximately 0.03VLo. Additional penetration may increase the soil resistance, but to increase the horizontal resistance to 0.1VLo the additional penetration will be in the order of 10% of the spudcan diameter and outside tolerable limits. In the case of partial penetration of the spudcan in sand (i.e., full bearing area not mobilized), any additional penetration will result in a significant increase of bearing capacity due to the rapid increase in the bearing area. An increase in embedded area of approximately 10% will increase the horizontal capacity to 0.1VLo. In clayey soils the requirement of QH < 0.1VLo is met if the ratio of the spudcan laterally projected area to bearing area, AS/A is in the order of 0.3. Step 1b - sliding, vertical and horizontal load vector: φHfc = 0.8 (effective stress - sand/drained) = 0.64 (total stress - clay/undrained) Step 2a - bearing, vertical and horizontal load vector: φVH = 0.9 (maximum bearing area not mobilized) = 0.85 (maximum bearing area mobilized) Step 2b - vertical, horizontal and moment load vector: φVHM = φVH from step 2a for leeward legs = φHfc from step 1b for windward legs Selection of safety factors against punch-through Where the potential for punch-through foundation failure is recognized, detailed consideration regarding foundation integrity will be required. Methods have been proposed for punch-through installation procedures and acceptability criteria but are omitted from this document as they remain ambiguous, (Rapaport [18], Senner [19]). Some jack-up designs are more able to tolerate rapid leg penetration than others and if the magnitude of the potential leg plunge is acceptable then installation could be possible even though punch-through is predicted during preloading. Significant investigation will be required in such circumstances and it is recommended that each potential punch-through situation is assessed on its own merit both at preloading and, should the potential for punch-through remain after installation, for the elevated operational and survival conditions. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 187 Mobile Jack-Up Units Rev 3, August 2008 C8.7 STRUCTURE CONDITION ASSESSMENT C8.7.1 Introduction Where an on-site structural inspection is required Section C8.7.2 provides guidance as to how this may be carried out. Section C8.7.3 provides guidance on monitoring the structural condition during an assignment. C8.7.2 Scope of Condition Assessment The aim of a condition assessment is to verify the condition of the structural components and details that are essential for the ultimate strength of the jack-up in the elevated condition and to confirm that the condition of the jack-up structure is in line with the assumptions made in the site specific analysis. Structural details to be assessed can be identified based on general considerations (see [20]), or on the results of site specific calculations and/or fatigue considerations. Condition assessment may comprise four steps with increasing involvement as described below. It is necessary that step 1 should always be completed and steps 2, 3 and 4 should be carried out as necessary to validate the condition of the jack-up. Step 1 - Review of existing records The review should initially cover the existing certificates and operating/inspection records. These should provide details of any incidents (indications of damage and subsequent repairs). Step 2 - Visual inspection A general visual inspection is carried out to confirm the rig is in a good state of repair and well maintained. The inspection should focus on the critical structural components and will include checks for missing members, mechanical damage, corrosion, etc. Normally this will only cover above water areas and should include a selection of the fatigue sensitive areas listed in Section 7.4.4. The visual inspection may be carried out by the same team visiting the unit for a precontract inspection (safety, drilling, etc.). However it is required that qualified personnel should be part of that team. Step 3 - Close Visual inspection Close visual inspection of key structural areas may be required if the condition can not be validated based on the review of existing records (step 1) and the general visual inspection (step 2). Hence the close visual inspection should focus on specific areas or details that may be in doubt. If fatigue is a consideration, it is recommended that, following steps 1 and 2, a selection of the fatigue sensitive areas should be subjected to close visual inspection. These close visual (weld) inspections should cover a number of locations from each of the groups of fatigue sensitive areas identified in Section 7.4.4. This should possibly be followed with an MPI inspection as outlined below. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 188 Mobile Jack-Up Units Rev 3, August 2008 C8.7.2 Step 4 - Detailed inspection Detailed inspection may be required in special cases and in case of inconclusive findings after completion of the three steps above. The detailed inspection is seen as a continuation of the visual inspection and hence is aimed at confirming that the condition of some specific details are sound for the intended operation. The major concern is the ultimate strength of the unit. Local damage with no significance for the planned mode of operation need not be assessed, but should be recorded for inclusion in future maintenance work. The scope of the inspection may include some NDT (e.g. MPI) and these inspections must be carried out by qualified personnel. The NDT will normally cover areas of specific concern. It may also be necessary to provide some spot checks of fatigue sensitive areas. In this case it is recommended that MPI checks should, as a minimum, be made at a selection of areas from each of the groups of fatigue sensitive locations identified in Section 7.4.4. If defects are found it may be necessary to expand the scope of the inspection so that the full extent of the damage can be assessed. C8.7.3 Condition Monitoring The condition of the jack-up structure should be monitored during the assignment. This is to ensure the continuation of the overall structural integrity during the operations. The requirements for condition monitoring may be based on the approach outlined in steps 1 through 4 above. The operating and maintenance records kept by the owner are the primary source of input for the independent condition monitoring and it should be possible to validate the condition of the unit by reviewing these records at any time during the operation. It is not expected that, for normal operations, the scope of the condition monitoring should extend beyond step 1. It is noted that records should be kept for future reference. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 189 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C8 a = M'uex/Mnx used in determination of η. A = constant in quadratic expression for β. A = cross sectional area. A = effective spudcan bearing area based on cross-section taken at uppermost part of bearing area in contact with the soil. Ai = cross sectional area of component i. As = laterally projected embedded area of spudcan. b = M'uey/Mny used in determination of η. B = constant in quadratic expression for β. B = moment amplification factor. B1 = moment amplification factor applicable to Mnt. B2 = moment amplification factor applicable to Mlt. C = constant in quadratic expression for β. CDD = product of drag coefficient and associated diameter. d = water depth (m). D = diameter of tubular member. Fmin = strength of weakest component. Fn1 = nominal strength of component 1. Fn2 = nominal strength of component 2. Fui = material ultimate strength for component i. Fy = material yield strength. F'y = effective material yield strength = 5Fu/6. Fyi = material yield strength for component i. F1 = factor used in computer axial capacity for plastic interaction. F2 = factor used in computer moment capacity for plastic interaction. Hs = significant wave height. K = parameter in chord strength interaction relationship. L1,L2,etc. = length of chord component 1, 2, etc. Mlt = moment attributed only to lateral deflection. Mnt = moment excluding lateral deflection. Mnx = nominal bending strength about member x-axis. Mny = nominal bending strength about member y-axis. Mp = plastic moment capacity. Mpx = plastic moment capacity about member x-axis. Mpy = plastic moment capacity about member y-axis. M'px = effective allowable x-axis bending capacity used in strength interaction equations. M'py = effective allowable y-axis ending capacity used in strength interaction equations. Mu = applied bending moment. Mue = effective applied bending moment. Mux, Muex = effective applied bending moment about member x-axis. Muy, Muey = effective applied bending moment about member y-axis. Mx = applied bending moment about member x-axis. My = applied bending moment about member y-axis. P,Pu = applied axial load. Pn = nominal axial strength. Py = axial yield strength. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 190 Mobile Jack-Up Units Rev 3, August 2008 GLOSSARY OF TERMS FOR SECTION C8 (Continued) t = wall thickness of tubular member. t1,t2,etc. = thickness of chord component 1, 2, etc. Tp = peak period associated with Hs. VT = tidal current velocity. zo = distance between plastic neutral axis and back face of chord. Z = plastic section modulus. β = safety index. ξ = exponent in chord strength interaction relationship. η = exponent in bending interaction relationship. φ = resistance factor. φa = resistance factor for axial load. φb = resistance factor for bending. φHfc = foundation resistance factor - sliding. φVH = foundation resistance factor - bearing under the action of vertical and horizontal loads. φVHM = foundation resistance factor - bearing under the action of vertical, horizontal and moment loads. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 191 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C8 1 Ahilan R.V., Baker M.J., Hoyle M.J.R. and Robinson N.J., "Reliability Based Development of Jack-up Assessment Criteria". Presented at the Tenth Structures Congress (ASCE), San Antonio, Texas, April 13-15, 1992. 2 Noble Denton Consultancy Services Limited. "Jack-up Assessment Criteria", Stage 1 Report, L15709/NDCS/RVA (Rev. 2) London, dated 28th February 1992. 3 Noble Denton Consultancy Services Limited. "Jack-up Assessment Criteria", Stage 2 Report, L16268/NDCS/RVA (Rev. 1), London, dated 8th January 1993. 4 Ahilan R.V., Baker M.J. and Snell R.O., "Development of Jack-up Assessment Criteria using Probabilistic Methods". OTC7305, Houston, Texas, 1993. 5 Noble Denton Consultancy Services Limited. "Jack-up Assessment Criteria - Interim Scope of Work Items 1.1 to 1.4 on Reliability Analysis". Report No. L15323/NDCS/RVA (Rev. 2) London, dated 4th March 1991. 6 Noble Denton Consultancy Services Limited. "Jack-up Assessment Criteria - Statement of Variable Selection". Report No. L15670/NDCS/RVA (Rev. 0), London, dated 12th September 1991. 7 Winterstein, S. "Nonlinear Vibration Models for Extremes and Fatigue", J. Engineering Mechanics, ASCE, Vol. 114, October 1988. 8 Juncher Jensen J., "Dynamic Amplification of Offshore Steel Platform Responses due to Non-Gaussian Wave Loads", Danish Center for Applied Mathematics and Mechanics Report No. 425, May 1991. 9 Manual of Steel Construction - Allowable Stress Design - Ninth Edition, AISC, 1989. 10 Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - API RP2A, Eighteenth Edition, 1 Sept 1989. 11 Load and Resistance Factor Design Specification for Structural Steel Buildings, AISC, 1 Sept 1986. 12 Draft Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Load and Resistance Factor Design API RP2A - LRFD First Edition, 1 Sept 1989. 13 Rules for Classification - Fixed Offshore Installations, Det Norske Veritas H`vik, July 1991. 14 Buckling strength analysis of Mobile Offshore Units - Classification Notes- Note 30.1, H`vik, October 1987. 15 Dyer A.P., "Plastic Strength Interaction Equations for Jack-Up Chords", MSc Thesis, Dept of Mechanical Engineering, Univ. of Sheffield, Nov. 1992. 16 Duan L., Chen W.-F., "A Yield Surface Equation for Doubly Symmetrical Sections", Engineering Structures, Vol 12, pp. 114-119, April 1990. 17 Norwegian Geotechnical Institute, "Cyclic Effects on Bearing Capacity and Stiffness for Jack-Up Platforms on Clay', Report 913012-1, May 1992. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER Commentaries to Recommended Practice for Site Specific Assessment of Page 192 Mobile Jack-Up Units Rev 3, August 2008 REFERENCES FOR SECTION C8 (Continued) 18 Rapaport V., Alford J., (1987) "Pre-loading of Independent Leg Units at Locations with Difficult Seabed Conditions." Conference title : Recent developments in jack-up platforms - design, construction and operation. The City University, London. 19 Senner D.W.F., (1992) "Analysis of Long Term Jack-up Rig Foundation Performance." Offshore Site Investigation and Foundation Behavior. SUT International Conference, London. 20 Sliggers P.G.F., "SIPM Practice for Site Specific Structural Fitness for Purpose Assessment of Jack-Up Rigs", Paper 21979, SPE/IADC Conference, Amsterdam, 11-14th March 1991. COMPLIMENTARY COPY FOR OC-7 PANEL MEMBER. Oil and gas industries including lower carbon energy — Site specific assessment of mobile offshore units Private Document! Part 1: Jack-ups: elevated at a site International Standard ISO_19905-1-EN-Rev-7-2024 The site-specific assessment (SSA) of a jack-up normally comprises the two parts: an elevated SSA (SSA-E), addressed in this document, and an installation and removal SSA (SSA-I), which is planned to be addressed in an International Standard as part of the ISO 19905 series. In this document, the following verbal forms are used: — “shall” indicates a requirement; — “should” indicates a recommendation; — “can” indicates a possibility or a capability; — “may” indicates a permission. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 INTERNATIONAL STANDARD ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 1 Oil and gas industries including lower carbon energy — Site-specific assessment of mobile offshore units — Part 1: Jack-ups: elevated at a site 1 Scope This document specifies requirements and provides recommendation and guidance for the elevated site-specific assessment (SSA-E) of independent leg jack-up units for use in the petroleum and natural gas industries. It addresses:a) occupied non-evacuated, occupied evacuated and unoccupied jack-ups; b) the installed (or elevated) phase at a specific site. It also addresses the requirement that the as-installed condition matches the assumptions used in the assessment. This document does not address the site-specific assessment of installation and removal (SSA-I).To ensure acceptable reliability, the provisions of this document form an integrated approach, which is used in its entirety for the site-specific assessment of a jack-up. When assessing a jack-up operating in regions subject to sea ice and icebergs, it is intended that the assessor supplements the provisions of this document with the relevant provisions relating to ice actions contained in ISO 19906 and procedures for ice management contained in ISO 35104. This document does not address design, transit to and from site, or installation and removal from site. This document is applicable only to independent leg mobile jack-up units that are structurally sound and adequately maintained, which is normally demonstrated through holding a valid recognized classification society, classification certificate. Jack-ups that do not hold a valid recognized classification society certificate are assessed according to the provisions of ISO 19902, supplemented by methodologies from this document, where applicable. NOTE 1 Well conductors can be a safety-critical element for jack-up operations. However, the integrity of well conductors is not part of the site-specific assessment process for jack-ups and is, therefore, not addressed in this document. See A.1 for guidance on this topic. NOTE 2 RCS rules and the IMO MODU code (International Maritime Organisation Mobile Offshore Drilling Unit code) provide guidance for the design of jack-ups. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 19901-1:2015, Petroleum and natural gas industries — Specific requirements for offshore structures — Part 1: Metocean design and operating conditions ISO 19901-2, Petroleum and natural gas industries — Specific requirements for offshore structures — Part 2: Seismic design procedures and criteria ISO 19901-4, Petroleum and natural gas industries — Specific requirements for offshore structures — Part 4: Geotechnical and foundation design considerations. ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures ISO 19906:2019, Petroleum and natural gas industries — Arctic offshore structures ISO 35104, Petroleum and natural gas industries — Arctic operations — Ice management ISO 35106, Petroleum and natural gas industries — Arctic operations — Metocean, ice, and seabed data 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 19901-2, ISO 19901-4, ISO 19906 and the following apply. ISO and IEC maintain terminology databases for use in standardization at the following addresses:— ISO Online browsing platform: available at https://www.iso.org/obp — IEC Electropedia: available at https://www.electropedia.org/ 3.1 abnormal environmental event environmental hazardous event (3.31) having probability of occurrence not greater than 10-3 per annum (1 in 1 000 years) 3.2 abnormal wave crest wave crest with probability of typically 10−3 to 10−4 per annum 3.3 accidental event non-environmental hazardous event (3.31) having probability of occurrence not greater than 10−3 per annum (1 in 1 000 years)Note 1 to entry: Accidental events, as referred to in this document, are associated with a substantial release of energy, such as vessel collisions, fires, and explosions. Note 2 to entry: Lesser accidents that could be expected during the life of the structure, such as dropped objects and low energy vessel impact, are termed incidents and are addressed under operational design situations. 3.4 action external load applied to the jack-up (3.36) (direct action) or an imposed deformation or acceleration (indirect action) EXAMPLE An imposed deformation can be caused by fabrication tolerances, differential settlement, temperature change or moisture variation. An imposed acceleration can be caused by an earthquake. [SOURCE: ISO 19900:2019, 3.3, modified  "structure" changed to "jack-up".] 3.5 action effect result of actions (3.4) on a structural member (3.87) or structural component (3.86) (e.g. internal force, moment, stress, strain) or on the jack-up (3.36) (e.g. deflection, rotation) [SOURCE: ISO 19900:2019, 3.4, modified  "structural member" added and "structure" changed to "jack-up".] 3.6 assessment site-specific assessment evaluation of the stability and structural integrity of a jack-up (3.36) and, where applicable, its seabed restraint or support against the actions determined in accordance with specific requirements Note 1 to entry: The specific requirements are given in this document. Note 2 to entry: An assessment can be limited to an evaluation of the components or members of the structure which, when removed or damaged, could cause failure of the whole structure, or a significant part of it. 3.7 assessment criteria quantitative formulations describing the conditions to be fulfilled for each assessment situation (3.9) [SOURCE: ISO 19900:2019, 3.15, modified  References to "design" deleted.] 3.8 assessment resistance resistance limit calculated using factored representative values (3.64) of basic variables (3.13) or from factored expressions based on unfactored representative values (3.64) of basic variables (3.13) EXAMPLE Examples of basic variables relevant to resistance are material properties.[SOURCE: ISO 19900:2019, 3.12, modified  "design" changed to "assessment".] 3.9 assessment situation set of physical conditions for which the jack-up (3.36) or its components are verified Note 1 to entry: For discussion on configuration, see 5.4.1. Note 2 to entry: The assessment situations are checked against the acceptance criteria of this document to demonstrate that the relevant limit states are not exceeded. [SOURCE: ISO 19900:2019, 3.16, modified  Reference to "design" deleted and "structure" changed to " jack-up".] 3.10 assessor entity performing the site-specific assessment 3.11 backfill submerged weight of all of the soil that can be present on top of the spudcan . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 4 © ISO 2023 – All right reserved Note 1 to entry: Backfilling can occur during or after preloading. WBF,o refers to the submerged weight of the backfilling that occurs up to achieving the preload reaction. WBF,A refers to the submerged weight of the backfilling that occurs after the maximum preload has been applied and held. Both WBF,o and WBF,A can comprise backflow and/or infill. For discussion of the effects, see A.9.3.2.1.4. 3.12 backflow soil that flows from beneath the spudcan around the sides and onto the top Note 1 to entry: Backflow is part of backfill (3.7). 3.13 basic variable variable representing physical quantities which characterize actions (3.4) and environmental influences, geometric quantities, or material properties including soil properties Note 1 to entry: Basic variables are typically uncertain random variables or random processes used in the calculation or assessment of representative values of actions or resistance. [SOURCE: ISO 19900:2019, 3.7] 3.14 boundary conditions actions and/or constraints on a structural member (or a group of structural members) by other structural members or by the surrounding environment Note 1 to entry: Boundary conditions can be used to generate reaction forces at locations of restraint. 3.15 characteristic value value assigned to a basic variable (3.13) with a prescribed probability Note 1 to entry: In some design/assessment situations, a variable can have two characteristic values, an upper value and a lower value. [SOURCE: ISO 19900:2019, 3.9] 3.16 chart datum CD local datum used to fix water depths on a chart or tidal heights over an area Note 1 to entry: Chart datum is usually an approximation to the level of the lowest astronomical tide. [SOURCE: ISO 19901-1:2015, 3.2] 3.17 consequence category classification system for identifying the environmental, economic and indirect personnel safety consequences of failure of a platform used to determine exposure level (3.21) [SOURCE: ISO 19902:2020, 3.11] 3.18 dynamic amplification factor DAF ratio of a dynamic action effect to the corresponding static action effect . Note 1 to entry: For a jack-up, the dynamic action effect is best simulated by means of a concentrated or distributed inertial loadset. It is usually not appropriate to factor the static actions to simulate the effects of dynamic actions. Note 2 to entry: In this document the DAFs used are either KDAF,SDOF for a single degree of freedom analogy or KDAF,RANDOM, for a stochastic simulation, see 4.1.1. 3.19 deterministic analysis analysis in which the response is determined from a single combination of actions 3.20 earthquake response spectrum function representing the peak elastic response for single degree of freedom oscillators with specific damping ratios in terms of absolute acceleration, pseudo velocity, or relative displacement values against natural frequency or period of the oscillators [SOURCE: ISO 19901-2:2022, 3.13, modified  "earthquake" added to term.] 3.21 exposure level classification system used to establish relevant criteria for a jack-up (3.36) based on consequences of failure Note 1 to entry: An exposure level 1 (L1) jack-up is the most critical and exposure level 3 (L3) the least (see ISO 19900:2019, 7.3). [SOURCE: ISO 19900:2019, 3.20, modified  "structure" replaced with "jack-up" and Note to entry added.] 3.22 extreme storm event extreme combination of wind, wave and current conditions used for the assessment of the jack-up (3.36) Note 1 to entry: This is the metocean event used for ULS storm assessment (see 5.5.4 and 6.4). 3.23 field general area where the jack-up (3.36) is intended to operate Note 1 to entry: The field is a general area as opposed to the site (3.74) which is specific. 3.24 fixed load permanent parts of the jack-up (3.36), including hull, legs and spudcans, outfit, stationary and moveable-fixed equipment Note 1 to entry: Moveable-fixed equipment normally includes the drilling package structure and associated permanently attached equipment. 3.25 footprint sea floor depression that remains when a jack-up (3.36) is removed from a site 3.26 foundation soil and spudcan supporting a jack-up (3.36) leg . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 6 © ISO 2023 – All right reserved 3.27 foundation fixity rotational restraint offered by the soil to the spudcan 3.28 foundation stability ability of the foundation to provide sufficient support to remain stable when subjected to actions and incremental deformation 3.29 global analysis determination of a consistent set of internal forces and moments, or stresses, in a structure that are in equilibrium with a defined set of actions on the entire structure Note 1 to entry: When a global analysis is of a transient situation (e.g. earthquake), the inertial response is part of the equilibrium. 3.30 hazard potential source of harm Note 1 to entry: Harm is typically differentiated between harm to people, harm to the environment, or harm in terms of costs to organization(s) or society in general. [SOURCE: ISO 19900:2019, 3.26] 3.31 hazardous event event that occurs when a hazard (3.30) interacts with a jack-up (3.36) EXAMPLE Wave or iceberg impacting the jack-up, excessive weight added to the jack-up, vessel collision and scour in the vicinity of the jack-up. [SOURCE: ISO 19900:2019, 3.27, modified  "structure" changed to "jack-up", Example modified to include iceberg and to exclude fire, explosion, and landslip.] 3.32 independent leg jack-up jack-up unit with legs that can be raised and lowered independently 3.33 inertial loadset set of actions that approximates the effect of the inertial forces Note 1 to entry: An inertial loadset is used only in quasi-static analyses. 3.34 infill soil above the plan area of the spudcan arising from sediment transport or hole sidewall collapse Note 1 to entry: Infill is part of backfill (3.11). 3.35 intrinsic wave frequency wave frequency of a periodic wave in a reference frame that is stationary with respect to the wave . No further reproduction or distribution permitted. Printed / viewed by: 7 Note 1 to entry: If there is no current, the reference frame is also stationary with respect to the sea floor. If there is a current, the reference frame moves with the same speed and in the same direction as the current. 3.36 jack-up mobile offshore unit with a buoyant hull and one or more legs that can be moved up and down relative to the hull Note 1 to entry: A jack-up reaches its operational mode by lowering the leg(s) to the seabed and then raising the hull to the required elevation. The majority of jack-ups have three or more legs, each of which can be moved independently and which are supported in the seabed by spudcans. 3.37 jack-up owner owner representative of the company or companies owning or chartering the jack-up Note 1 to entry: The energy company, the operator (3.53), contracts the jack-up and is generally not the owner or charterer. 3.38 joint probability metocean data combinations of wind, wave and current that produce the action effect that can be expected to be exceeded at a site, on average, once in the return period 3.39 leaning instability instability of an independent leg jack-up that can arise when the rate of increase of actions on the foundation with jack-up inclination exceeds the rate of increase of foundation capacity with depth 3.40 limit state state beyond which the jack-up (3.36) or a structural member (3.87) no longer satisfies the assessment criteria 3.41 load case compatible load arrangements, sets of deformations and imperfections considered simultaneously with permanent actions and fixed variable actions for a particular design or verification 3.42 long-term operation operation of a jack-up on one particular site for more than the recognised classification society special survey period 3.43 lowest astronomical tide LAT level of low tide when all harmonic components causing the tides are in phase Note 1 to entry: The harmonic components are in phase approximately once every 19 years, but these conditions are approached several times each year. [SOURCE: ISO 19901-1:2015, 3.17] . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 8 © ISO 2023 – All right reserved 3.44 mat-supported jack-up jack-up unit with the leg(s) rigidly connected by a foundation structure, such that the leg(s) are raised and lowered in unison 3.45 mean high water spring tidal level arithmetic mean of all high water spring tidal sea levels measured over a long period, ideally 19 years 3.46 mean low water spring tidal level arithmetic mean of all low water spring tidal sea levels measured over a long period, ideally 19 years 3.47 mean sea level MSL arithmetic mean of all sea levels measured at hourly intervals over a long period Note 1 to entry: Seasonal changes in mean level can be expected in some regions and over many years the mean sea level can change. [SOURCE: ISO 19901-1:2015, 3.20] 3.48 mean zero-upcrossing period average intrinsic period of the zero-upcrossing waves in a sea state Note 1 to entry: In practice, the mean zero-crossing period is often estimated from the zeroth and second moments of the wave spectrum as given by Formula (3.41-1): z202022()()()()TTmfmfmmωω===π (3.41-1) where f is the frequency in cycles per second (Hertz); m0 is the zeroth spectral moment and is equivalent to σ2, the variance of the corresponding time series; m2 is the second spectral moment; T2 and Tz are the average zero-upcrossing period of the water surface elevation, defined by the zeroth and second order spectral moments, (T2 = Tz); ω is the wave frequency in radians per second. [SOURCE: ISO 19901-1:2015, 3.22, modified  "intrinsic" deleted, "(up or down) zero-crossing" changed to "upcrossing" and definitions of terms in the equation added] 3.49 most probable maximum extreme MPME value of the maximum of a variable with the highest probability of occurring over a defined period of time Note 1 to entry: A defined period of time can be, for example, X hours. Note 2 to entry: The most probable maximum extreme is the value for which the probability density function of the maxima of the variable has its peak. It is also called the mode or modus of the statistical distribution. . No further reproduction or distribution permitted. Printed / viewed by: 9 [SOURCE: ISO 19901-1:2015, 3.24, modified  Added "over a defined period of time" and note 1 to entry.] 3.50 nominal strength strength calculated for a cross-sectional area, taking into account the stress raising effects of the macro-geometrical shape of the component of which the section forms a part, but disregarding the local stress raising effects from the section shape and any weldment or other fixing detail 3.51 nominal value value assigned to a variable specified or determined on a non-statistical basis, typically from acquired experience or physical conditions, or as published in a recognized code or standard Note 1 to entry: In some design/assessment situations, a variable can have two nominal values, an upper value 3.52 operating manual marine operations manual latest approved document that defines the operational characteristics and capabilities of the jack-up Note 1 to entry: The assessor (3.10) is should ensure that any updated weight data are provided. 3.53 operator representative of the company or companies leasing the site Note 1 to entry: The operator is normally the oil company acting on behalf of co-licensees. [SOURCE: ISO 19900:2019, 3.35, modified  Note 2 to entry deleted.] 3.54 performance ability of a jack-up (3.36) or a structural member (3.87) and the foundation to fulfil specified requirements Note 1 to entry: Specified requirements include requirements for structural and foundation integrity and functionality. [SOURCE: ISO 19900:2019, 3.36 modified  Added "and the foundation", and "structure" replaced with "jack-up" and " structural component" replaced with "structural member".] 3.55 preloading installation and embedment of the spudcans by vertical loading of the soil beneath a jack-up leg spudcan with the objective of ensuring sufficient foundation capacity under assessment situations through to the time when the maximum load is applied and held Note 1 to entry: While three-legged jack-ups preload by taking water ballast on board, jack-ups with four or more legs typically achieve foundation preload by carrying the hull weight on pairs of legs in turn. This procedure is known as pre-driving and generally does not require the addition of water ballast. For the purposes of this document, no distinction is made between preload and pre-drive. 3.56 preload reaction maximum vertical reaction under a spudcan supporting the in-water weight of the jack-up during the entire preloading operation . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 10 © ISO 2023 – All right reserved Note 1 to entry: The in-water weight is the full weight of the hull, variable load and preload ballast, plus the legs and spudcans and any contained water, reduced by the buoyancy in water of the legs and spudcans (calculated from their external dimensions). Soil buoyancy and the weight of any soil backfill above the spudcan are neglected. It is necessary to take care when accounting for water contained in the spudcan (in some cases this can be included in the quoted leg weight). Note 2 to entry: This is the maximum reaction on a spudcan which would be obtained during preloading if the jack-up were installed on an infinitely rigid foundation. Note 3 to entry: The preload reaction is a key parameter in the geotechnical analysis of independent leg foundations. Assessors consider values that can be reasonably achieved during preload operations. The assessment is invalidated if the value considered in the site assessment is not achieved during preload operations. 3.57 punch-through rapid, uncontrolled vertical leg movement due to soil failure in strong soil overlying weak soil 3.58 quasi-static static representation of a dynamic process Note 1 to entry: In some cases, the influence of structural accelerations can be approximated by using an equivalent inertial loadset. 3.59 rack phase difference RPD relative difference in the position of adjacent leg chords within a leg measured parallel to the longitudinal axis of the chords Note 1 to entry: This is the out-of-plane distortion of the plan-frame. 3.60 recognized classification society RCS member of the international association of classification societies (IACS), with recognized and relevant competence and experience in jack-ups, and with established rules and procedures for classification/certification of such units used in petroleum-related activities [SOURCE: ISO 19901-7:2013, 3.23, modified  "floating structures" replaced by "jack-ups", "installations" replaced by "such units".] 3.61 redundancy ability of a structure to find alternative load paths following structural failure of one or more components, thus limiting the consequences of such failures Note 1 to entry: Statically determinate structures, contrary to statically indeterminate structures, do not generally exhibit redundancy. [SOURCE: ISO 19902:2020, 3.38] 3.62 regulator authority established by a national governmental administration to oversee the activities of the offshore oil and natural gas industries within its jurisdiction, with respect to the overall safety to life and protection of the environment . No further reproduction or distribution permitted. Printed / viewed by: 11 Note 1 to entry: The term "regulator" can encompass more than one agency in any particular territorial waters. Note 2 to entry: The regulator can appoint other agencies, such as marine classification societies, to act on its behalf, and in such cases, regulator as it is used in this document includes such agencies. Note 3 to entry: In this document, the term "regulator" does not include any agency responsible for approvals to extract hydrocarbons, unless such agency also has responsibility for safety and environmental protection. [SOURCE: ISO 19902:2020, 3.39] 3.63 reliability performance (3.54) over a specified period of time Note 1 to entry: When reliability is used in the context of limit states, it can be expressed as the probability that the limit is not exceeded. Note 2 to entry: The specified period of time is typically one year. [SOURCE: ISO 19900:2019, 3.39] 3.64 representative value value assigned to a basic variable (3.13) for verification of a limit state (3.40) in an assessment situation (3.9) Note 1 to entry: Two types of representative value used in verification are characteristic value (3.15) and nominal value (3.51). [SOURCE: ISO 19900:2019, 3.40, modified  "Design" deleted.] 3.65 resistance ability to withstand action effects (3.5) Note 1 to entry: When undertaking an assessment, the resistance checks normally include: Overturning stability, foundation, holding system, structural members (3.83) and structural components (3.82). 3.66 return period average period between occurrences of an event Note 1 to entry: The offshore industry commonly uses a return period measured in years for environmental events. The return period in years is equal to the reciprocal of the annual probability of occurrence of the event. Note 2 to entry: For the purpose of this definition, events include both discrete hazardous events as well as exceedances of a threshold value of a relevant variable. [SOURCE: ISO 19900:2019, 3.42] 3.67 scatter diagram joint probability of two or more (metocean) parameters Note 1 to entry: A scatter diagram is especially used with wave parameters in the metocean context, see ISO 19901-1:2015, A.5.8. The wave scatter diagram is commonly understood to be the probability of the joint occurrence of the significant wave height (Hs) and a representative period (Tz,i or Tp,i). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 12 © ISO 2023 – All right reserved [SOURCE: ISO 19901-1:2015, 3.29, modified  In Note to entry, "(for example in fatigue assessments)" replaced by ", see ISO 19901-1:2015, A.5.8".] 3.68 scour removal of seabed material from the foundation due to current and waves 3.69 sea floor interface between the sea and the seabed (3.71) [SOURCE: ISO 19900:2019, 3.46] 3.70 sea state condition of the sea during a period in which its statistics remain approximately stationary Note 1 to entry: In a statistical sense the sea state does not change markedly within the period. The period during which this condition exists is usually assumed to be three hours, although it depends on the particular weather situation at any given time. [SOURCE: ISO 19901-1:2015, 3.31] 3.71 seabed materials below the sea floor (3.69) [SOURCE: ISO 19900:2019, 3.47] 3.72 shallow gas gas pockets or entrapped gas below impermeable layers at shallow depth 3.73 significant wave height statistical measure of the height of waves in a sea state Note 1 to entry: The significant wave height was originally defined as the mean height of the highest one-third of the mean zero upcrossing waves in a sea state. In most offshore data acquisition systems, the significant wave height is currently taken as 04m(where m0 is the zeroth spectral moment, see ISO 19901-1:2015, 3.37) or 4σ, where σ is the standard deviation of the time series of water surface elevation over the duration of the measurement, typically a period of approximately 30 min. [SOURCE: ISO 19901-1:2015, 3.35] 3.74 site specific position and orientation at which a jack-up (3.36) operates within a field (3.23) 3.75 skirt vertical bulkhead(s), closed in plan view, beneath the main body of a spudcan (3.81) 3.76 skirted spudcan spudcan (3.81) with a skirt (3.75) . No further reproduction or distribution permitted. Printed / viewed by: 13 3.77 sliding horizontal movement of a spudcan 3.78 special survey extensive and complete survey carried out at each nominal year interval, which closes a cycle of annual classification and mandatory surveys Note 1 to entry: This is also referred to as “renewal survey” by some IACS members. The special survey period is normally between five and eight years. 3.79 spectral density function spectrum energy density function measure of the variance associated with a time-varying variable per unit frequency band and per unit directional sector Note 1 to entry: Spectrum is a shorthand expression for the full and formal name of spectral density function or energy density function. Note 2 to entry: The spectrum is, in general, written with two arguments: one for the frequency variable and one for a direction variable. Note 3 to entry: Within ISO 19901-1, the concept of a spectrum applies to waves, wind turbulence and action effects (responses) that are caused by waves or wind turbulence. For waves, the spectrum is a measure of the energy traversing a given space. Note 4 to entry: Not to be confused with an earthquake response spectrum. [SOURCE: ISO 19901-1:2015, 3.39, modified  Deleted first sentence of Note 2 to entry. Added Note 4 to entry.] 3.80 spectral peak period period of the maximum (peak) energy density in the spectrum (3.79) Note 1 to entry: In practice, there is often more than one peak in a spectrum. Note 2 to entry: There are two types of spectral peak period used within this document: intrinsic and apparent. The distinction is discussed in A.7.3.3.5, which is, in turn, based on ISO 19901-1:2015, 8.4.4 and A.8.4.3. [SOURCE: ISO 19901-1:2015, 3.38, modified  Added Note 2 to entry.] 3.81 spudcan structure at the base of a leg supported by the soil 3.82 squeezing lateral movement of weak soil between the spudcan base and an underlying stronger layer, or of weak soil between two stronger layers 3.83 stochastic analysis analysis in which a probabilistic approach is taken to model the random nature of the variables of interest . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 14 © ISO 2023 – All right reserved Note 1 to entry: In general, a linear(ized) stochastic analysis can be performed in the frequency domain or in the time domain, whereas non-linear stochastic analysis can only use time domain simulations. This document does not support frequency domain stochastic analysis. 3.84 stress concentration factor SCF factor relating a local stress to the nominal stress at a detail [SOURCE: ISO 19902:2020, 3.49, modified  Note 1 to entry deleted.] 3.85 structural analysis process or algorithm for determining action effects from a given set of actions Note 1 to entry: Structural analyses are performed at three levels [global analysis of an entire structure, analysis of part of a structure (e.g. a leg), local analysis of a structural member and local analysis of a structural component] using different structural models. [SOURCE: ISO 19902:2020, 3.50, modified  Note 1 to entry with added example and reference to "structural member".] 3.86 structural component component physically distinguishable part of a member cross-section of uniform yield strength Note 1 to entry: The cross-section of a non-tubular member is usually comprised of several structural components. A component consists of only one material. Where a plate component is reinforced by another piece of plating, the reinforcement can be of a different yield strength. See also further discussion in A.12.1.1. 3.87 structural member member physically distinguishable part of a braced structure connecting two joints Note 1 to entry: A structural member can also be defined as the leg of a non-truss leg jack-up. Note 2 to entry: See also further discussion in A.12.1.1. 3.88 sudden hurricane sudden cyclone sudden typhoon sudden tropical revolving storm that forms locally and, due to speed of formation and proximity to infrastructure at time of formation, might not allow sufficient time to evacuate occupied facilities within the time required by the emergency evacuation plan Note 1 to entry: The intent is that the jack-up be assessed to L1 for the specified sudden tropical revolving storm, see 5.5.2 and 5.5.3. 3.89 sustained wind speed time-averaged wind speed with a defined averaging duration of 1 min or longer at a specified elevation [SOURCE: ISO 19901-1:2015, 3.43, modified  Duration changed from “10 min or longer”.] . No further reproduction or distribution permitted. Printed / viewed by: 15 3.90 undrained shear strength maximum shear stress at yielding or at a specified maximum strain in an undrained condition Note 1 to entry: Yielding is the condition of a material in which a large plastic strain occurs at little or no stress increase. Note 2 to entry: Strain softening is also to be considered. [SOURCE: ISO 19901-8:2023, 3.42, modified  Added Note 2 to entry.] 3.91 utilization member utilization foundation utilization maximum absolute value of the ratio of the generalized representation of the assessment action effect to the generalized representation of the assessment resistance in compatible units Note 1 to entry: Utilizations are calculated for each limit state of the assessment situation being considered. Note 2 to entry: Only utilizations smaller than or equal to 1,0 satisfy the assessment criteria for a particular limit state. Note 3 to entry: The assessment action effect is the response to the factored actions. The assessment resistance is the representative resistance divided by the partial resistance factor. Note 4 to entry: For members and foundations subjected to combined forces, the internal force pattern and the resistance combine into an interaction formula. If the interaction formula governing the assessment check is, or can be, reduced to an inequality of the form U ≤ 1,0, then the utilization is equal to U. 3.92 variable load items carried by the jack-up to support its operation that are not included in the fixed load 3.93 water depth vertical distance between the sea floor and still water level Note 1 to entry: As there are several options for the still water level (see A.6.4.4), there can be several water depth values. Generally, assessment water depth is determined to the extreme still water level. Note 2 to entry: The water depth used for calculating wave kinematics varies between the maximum water depth of the mean high water spring tide plus a positive storm surge, and the minimum water depth of the mean low water spring tide less a negative storm surge, where applicable. [SOURCE: ISO 19901-1:2015, 3.47, modified  Notes to entry rewritten.] 4 Symbols and abbreviated terms 4.1 Symbols 4.1.1 General 𝐴𝐴𝐹𝐹d action effect due to factored actions BS soil buoyancy of spudcan below bearing area, i.e. the submerged weight of soil displaced by the spudcan below Dembed, the greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor Cmr moment reduction factor . No further reproduction or distribution permitted. Printed / viewed by: Dembed greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor De equivalent set of inertial actions representing dynamic extreme storm effects or ground motion effects due to earthquakes Ee metocean actions due to the extreme storm event fFD fatigue damage design factor Fd assessment load case (see 8.8) FH horizontal force applied to the spudcan due to the assessment load case (see 8.8) FV gross vertical force acting on the soil beneath the spudcan due to the assessment load case Fd (see 8.8) GF actions due to the fixed load positioned such as to adequately represent their vertical and horizontal distribution Gv actions due to maximum or minimum variable load, as appropriate, positioned at the most onerous centre of gravity location applicable to the configurations under consideration K effective length factor KDAF,RANDOM DAF from random wave time domain (stochastic) analyses, including the mean values, obtained from a random wave calculation. It is the ratio of the absolute value of a dynamic action effect to the absolute value of the corresponding static action effect, each including their mean value KDAF,SDOF DAF from single degree-of-freedom representation of dynamic behaviour, excluding the mean values, obtained from a single degree-of-freedom (SDOF) calculation. It is the ratio of the amplitude of a dynamic action effect to the amplitude of the corresponding static action effect for periodic excitation of a linear one degree-of-freedom model approximation of jack-up behaviour L1 length of the vector from a specified origin to the action effect L2 length of the vector from the origin specified for L1 to the factored interaction surface Lb1 length of the vector from origin used for establishing the bearing utilization (FH, FV)ORG to the environmental response point (determined from the factored actions) (FH, FV) Lb2 length of the vector from origin used for establishing the bearing utilization (FH, FV)ORG and passing through (FH, FV) to the factored vertical-horizontal capacity surface QVH,f Ls1 length of the vector from origin used for establishing the sliding utilization (FH, FV)ORG to the environmental response point (determined from the factored actions) (FH, FV) Ls2 length of the vector from origin used for establishing the sliding utilization (FH, FV)ORG and passing through (FH, FV) to the factored vertical-horizontal capacity surface QVH,fv LAE length of the vector from a specified origin to the action effect LIS length of the vector from the same origin to the factored interaction surface MOTM overturning moment due to factored actions . 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Printed / viewed by: 17 N number of cycles to failure in fatigue of a specified constant amplitude stress range QH maximum horizontal foundation capacity R factored resistance Rd,OTM factored stabilizing moment Rr,OTM representative stabilizing moment Tn jack-up natural period Tp apparent modal or peak period of the wave spectrum Tp,i intrinsic modal or peak period of the wave spectrum Tz,i intrinsic mean zero-upcrossing period of the water surface elevation in a sea state U utilization US,pl utilization of preload US,sl utilization of foundation resistance to sliding US,vhm utilization of vertical and horizontal foundation capacity VLo maximum vertical reaction under the spudcan considered required to support the in-water weight of the jack-up during the entire preloading operation (this is not the soil capacity; see 3.56) Vst vertical force applied to the spudcan due to the assessment load case (see 8.8) (includes effects of leg weight and water buoyancy but excludes effects of backfill and spudcan soil buoyancy) WBF,A submerged weight of the backfill that occurs after the maximum preload has been applied and held WBF,o submerged weight of the overburden on top of the spudcan from backfill during preloading 𝛾𝛾f,D partial action factor applied to the inertial actions due to dynamic response 𝛾𝛾f,E partial action factor applied to the metocean or earthquake actions 𝛾𝛾f,G partial action factor applied to the actions due to fixed load 𝛾𝛾f,V partial action factor applied to the actions due to the variable load 𝛾𝛾R,H partial resistance factor for holding system strength 𝛾𝛾R,Hfc partial resistance factor for horizontal foundation capacity 𝛾𝛾R,OTM partial resistance factor for stabilizing moment 𝛾𝛾R,PRE partial resistance factor for preload 𝛾𝛾R,S partial resistance factor for spudcan strength 𝛾𝛾VH partial resistance factor for foundation capacity 4.1.2 Symbols used in A.6 D1 directional spreading function as a function of n . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 18 © ISO 2023 – All right reserved D2 directional spreading function as a function of s D3 directional spreading function as a function of σ dw water depth F(αw) directionality function f wave frequency Hmax individual extreme wave height Hs increased significant wave height to account for wave asymmetry Hsrp significant wave height for the assessment return period href reference depth for wind-driven current Lw wave length of the wave with Hmax and Tass in water depth dw, according to the periodic wave theory used N inverse exponent of the power law wind profile n parameter exponent in D1 Sy smallest spacing between the legs of 3-legged jack-ups SPM(ω) Pierson-Moskowitz wave spectrum for a sea state SJS(ω) JONSWAP wave spectrum for a sea state Sηη(f) wave spectral density function expressed as a function of wave frequency Sηη(f,α w) directional short-crested power density spectrum s parameter in D2 su,ave average undrained shear strength = (suC + suD + suE)/3 suC static triaxial compression undrained shear strength suD static DSS undrained shear strength suE static triaxial extension undrained shear strength Tass intrinsic wave period associated with Hmax Tp apparent modal or peak period of the wave spectrum Tp,i intrinsic modal or peak period of the wave spectrum Tz,i intrinsic mean zero-upcrossing period of the water surface elevation in a sea state VC current velocity as a function of z Vs downwind component of associated surge current (excluding wind-driven component) Vref 1 min sustained wind speed at elevation Zref (normally at 10 m above MSL) Vt downwind component of mean spring tidal current . 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Printed / viewed by: 19 Vw wind generated surface current VZ the wind speed at elevation Z above SWL under consideration Z elevation above SWL under consideration z vertical coordinate relative to SWL under consideration, positive upwards Zref reference elevation above MSL αw angle between the direction of elementary wave trains and the dominant direction of the short-crested waves γ shape parameter of the peak enhancement factor in the JONSWAP spectrum κ kinematics reduction factor φ directional spreading factor based on latitude σ standard deviation of the normal distribution in D3 Ψ latitude 4.1.3 Symbols used in A.7 Acs cross-sectional area of member Ae equivalent area of leg per unit height Ai equivalent area of member or gusset i AWi projected area of the block i perpendicular to the wind direction CA added mass coefficient CDe equivalent value of the drag coefficient of a leg bay CDei equivalent value of the drag coefficient of member i CD, CDi drag coefficient, drag coefficient of member i CDpr(θ ) drag coefficient related to the projected diameter CD0 drag coefficient for a tubular with appropriate roughness CD1 drag coefficient for flow normal to the rack related to projected diameter, W Cm, Cmi inertia coefficient, inertia coefficient of member i Cme equivalent value of the inertia coefficient of a leg bay Cmei equivalent value of the inertia coefficient of member i Cs shape coefficient Dr, Di reference diameter, reference diameter of member i De equivalent diameter of leg DF face width of leg, outside dimensions, orthogonal to the flow direction . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 20 © ISO 2023 – All right reserved Dpr(θ ) projected diameter dw water depth Hs increased significant wave height to account for wave asymmetry Lw wave length li length of member i node to node centre ma added mass contribution (per unit length) for a member Pi pressure at the centre of block i s height of one bay, or part of bay considered Ti intrinsic period of a periodic wave (in a reference frame that is stationary with respect to the wave, i.e. with no current present) Tn first natural period of surge or sway motion of the jack-up Tp apparent modal or peak period of the wave spectrum Tp,i intrinsic modal or peak period of th wave e spectrum Tz apparent mean zero-upcrossing period of the water surface elevation in a sea state Tz,i intrinsic mean zero-upcrossing period of the water surface elevation in a sea state tm marine growth thickness W projected width nr velocity of the considered member, normal to the member axis and in the direction of the combined particle velocity nr acceleration of the considered member, normal to the member axis and in the direction of the combined particle velocity u wave particle velocity un wave particle velocity resolved normal to the member axis nu wave particle acceleration resolved normal to the member axis VC current velocity for use in the hydrodynamic model Vf far field (undisturbed) current velocity Vzi wind velocity at the centre of block i vn fluid particle velocity resolved normal to the member axis z′ modified coordinate for use in particle velocity formulation z vertical coordinate relative to SWL under consideration, positive upwards αi angle between flow direction and member axis projected onto a horizontal plane . 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Printed / viewed by: 21 βi angle defining the member inclination from horizontal ΔF wave action per unit length ΔFdrag drag action per unit length ΔFinertia inertia action per unit length ρa mass density of air ρw mass density of water θ angle in degrees ζw instantaneous water level (same axis system as z) 4.1.4 Symbols used in A.8 Aeq axial area of equivalent leg model beam Aseff effective shear area of the equivalent leg model beam E Young's modulus of steel F applied axial action G shear modulus I second moment of area Khh horizontal leg-to-hull connection stiffness Krh rotational leg-to-hull connection stiffness Kvh vertical leg-to-hull connection stiffness Lc cantilevered length (from the hull to the seabed reaction point) Lub distance from the spudcan reaction point to the hull vertical centre of gravity M applied moment P applied shear Pg sum of the leg forces due to functional actions on legs at hull, including the weight of the legs above the hull Δ axial deflection (shortening) of the leg at the point of force application from the detailed leg model ΔC axial end displacements of the combined leg and leg-to-hull connection model 𝛥𝛥M lateral deflection of the cantilevered leg at the point of moment application from the detailed leg model 𝛿𝛿C lateral deflection of the cantilevered leg at the point of moment application from the combined leg and leg-to-hull connection model 𝛿𝛿M lateral deflection of the cantilevered leg at the point of moment application from the detailed leg model . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 22 © ISO 2023 – All right reserved θC slope of the end of the cantilever from the combined leg and leg-to-hull connection model θM slope of the cantilever at the point of moment application from the detailed leg model θP slope of the cantilever at the point of shear application from the detailed leg model 4.1.5 Symbols used in A.9 and Annex E A spudcan effective bearing area based on cross-section taken at uppermost part of bearing area in contact with soil (see Figure A.9.3-3) As spudcan laterally projected embedded area a depth interpolation parameter as bearing capacity squeezing factor constant B effective spudcan diameter at uppermost part of bearing area in contact with the soil (for rectangular footing B equal to width) Bmax diameter of the contact area in plan when the spudcan is fully seated BS soil buoyancy of spudcan below bearing area i.e. the submerged weight of soil displaced by the spudcan below Dembed, the greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor bs bearing capacity squeezing factor constant dependent on spudcan diameter CH horizontal capacity coefficient CH,NC horizontal capacity coefficient for the normally consolidated case per A.9.3.3.2 a) i) CH,U horizontal capacity coefficient for the uniform strength case per A.9.3.3.2 a) ii) CH,shallow horizontal capacity coefficient at shallow embedment CH,deep horizontal capacity coefficient at deep embedment CM moment capacity coefficient CM,NC moment capacity coefficient for the normally consolidated case per A.9.3.3.2 a) i) CM,U moment capacity coefficient for the uniform strength case per A.9.3.3.2 a) ii) Dembed greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor (see Figure A.9.3-3) Db depth of backflow; infill should not be considered DR relative density of sand (percent) d depth beneath sea floor dc bearing capacity depth factor dcrit depth at which maximum bearing resistance occurs (layered case) dq depth factor on surcharge for drained soils dγ depth factor on self weight for drained soils . 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Printed / viewed by: 23 fcy,V cyclic degradation factor on vertical capacity fcy,H cyclic degradation factor on horizontal capacity fcy,M cyclic degradation factor on moment capacity FH horizontal force applied to the spudcan due to the assessment load case (see 8.8) FM moment force applied to the spudcan due to the assessment load case (see 8.8) FV gross vertical force acting on the soil beneath the spudcan due to the assessment load case Fd (see 8.8) (FV/QV)t vertical load at intersection of adhesion yield surface and foundation yield surface f1 factor applied to horizontal capacity used in yield surface formula for embedded spudcans on clay f2 factor applied to moment capacity used in yield surface formula for embedded spudcans on clay fr foundation rotational stiffness reduction factor Gmax maximum value of the shear modulus (of the foundation soil) which occurs at small strain H distance from spudcan maximum bearing area to weaker layer below Hcav limiting depth of cavity that remains open above the spudcan during penetration h1 embedment depth to the uppermost part of the spudcan, (if not fully embedded, h1 = 0) h2 spudcan tip embedment depth IrNC rigidity index for normally consolidated clays IP plasticity index j dimensionless stiffness factor ka active earth pressure coefficient (for su = 0) kp passive earth pressure coefficient K1, K2, K3 stiffness factors for vertical, horizontal and rotational foundation stiffness respectively Kd1, Kd2, Kd3 depth factors for vertical, horizontal and rotational foundation stiffness respectively Ks coefficient of punching shear Ls length of strip footing m parameter to define effect of adhesion on the foundation yield surface envelope ns load spread factor for sand overlying clay Nc bearing capacity factor, taken as Nc sc = 6,0 for circular footings Nq bearing capacity factor for a flat rough circular footing . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 24 © ISO 2023 – All right reserved Nγ bearing capacity factor for a flat rough circular footing po′ effective overburden pressure at greatest embedment depth, Dembed, of maximum bearing area pa atmospheric pressure Q0 spudcan bearing capacity at sea floor QH maximum horizontal foundation capacity QHs foundation sliding capacity QM ultimate moment capacity of foundation QMp increased ultimate moment capacity due to further spudcan penetration under environmental actions QMps ultimate moment capacity when further spudcan penetration leads to full contact of the entire underside of the spudcan with the seabed QMpv ultimate moment capacity under further spudcan penetration, when the applied vertical force is too low to achieve full contact of the entire underside of the spudcan with the seabed Qpeak maximum bearing capacity at d = dcrit Qu,b ultimate vertical foundation bearing capacity assuming the spudcan bears on the surface of the lower (bottom) clay layer with no backfill QV gross ultimate vertical foundation capacity QVnet net ultimate vertical foundation capacity QVo initial gross ultimate vertical foundation capacity established by preload operations rf failure ratio ROC over-consolidation ratio sc bearing capacity shape factor su undrained shear strength su,a undrained shear strength of backfill material above the spudcan suo undrained shear strength at greatest embedment depth of maximum bearing area, Dembed, below sea floor suH undrained shear strength at depth of Hcav below sea floor su,l undrained shear strength at the spudcan tip sum undrained shear strength at the sea floor su,b undrained shear strength of lower clay layer below spudcan su,t undrained shear strength of upper clay layer below spudcan . No further reproduction or distribution permitted. Printed / viewed by: 25 su,ned minimum undrained shear strength near (within ¼ spudcan diameter below) the embedment depth su,nml minimum undrained shear strength within ¼ spudcan diameter below the mudline. T thickness of weak clay layer underneath spudcan VD volume of the spudcan below the maximum bearing area that is penetrated into the soil VL available spudcan reaction VLo maximum vertical reaction under the spudcan considered required to support the in-water weight of the jack-up during the entire preloading operation (this is not the soil capacity; see 3.56) Vst vertical force applied to the spudcan by the assessment load case, see 8.8, (includes effects of leg weight and water buoyancy but excludes effects of backfill and spudcan soil buoyancy) Vspud the total volume of the spudcan beneath the backfill Vsw gross vertical spudcan reaction under still water conditions for the spudcan being considered (includes effects of backfill and spudcan soil buoyancy) WBF submerged weight of the backfill WBF,A submerged weight of the backfill that occurs after the maximum preload has been applied and held WBF,o submerged weight of the overburden on top of the spudcan from backfill during preloading WBF,omin minimum value of the submerged weight of the backfill, due to backflow during preloading αs adhesion factor β equivalent cone angle δ steel/soil friction angle in degrees γR, Hfc partial resistance factor for horizontal foundation capacity γR, VH partial resistance factor for foundation capacity γ′ submerged (effective) unit weight of soil ρsu rate of increase in undrained shear strength with depth φ′ effective angle of internal friction for sand in degrees ν Poisson's ratio 4.1.6 Symbols used in A.10 B effective spudcan diameter at uppermost part of bearing area in contact with the soil Crd radiation damping coefficient of a dashpot (force per unit velocity) . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 26 © ISO 2023 – All right reserved De equivalent set of inertial actions representing dynamic extreme storm effects or ground motion effects due to earthquakes Ee metocean actions due to the extreme storm event FBS,Amplitude single amplitude of quasi-static base shear over one wave cycle FBS,(QS)Max maximum quasi-static wave/current base shear FBS,(QS)Min minimum quasi-static wave/current base shear Fin magnitude of the inertial loadset G shear modulus GF actions due to the fixed load positioned such as to adequately represent their vertical and horizontal distribution Go shear modulus of the foundation soil Gv actions due to maximum or minimum variable load, as appropriate, positioned at the most onerous centre of gravity location applicable to the configurations under consideration KDAF,RANDOM DAF from random wave time domain (stochastic) analyses K DAF,SDOF DAF from single degree-of-freedom representation of dynamic behaviour Keff effective system stiffness Meff effective system mass OT total horizontal offset of the leg base with respect to the hull O1 offset due to leg-to-hull clearances O2 offset due to maximum hull inclination permitted by the operating manual Tn first natural period of surge or sway motion of the jack-up Tp apparent modal or peak period of the wave spectrum Tp,i intrinsic modal or peak period of the wave spectrum ν Poisson's ratio (of the foundation soil) Ω ratio of jack-up natural period to wave excitation period ρ total, saturated, (mass) density of the foundation soil ζ damping ratio or fraction of critical damping ζrd radiation modal damping ratio to account for spudcan vertical motion ωn natural frequency (rad/s) 4.1.7 Symbols used in A.11 Dc,e calculated existing fatigue damage prior to arriving at site . 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Printed / viewed by: 27 Dc,s calculated fatigue damage during planned operations on site fFD,e fatigue damage design factor applicable to Dc,e fFD,s fatigue damage design factor applicable to Dc,s N number of cycles to failure in fatigue of a specified constant amplitude stress range, S S constant amplitude stress range 4.1.8 Symbols used in A.12 A gross cross-sectional area Aec total effective area of a slender section in compression of a non-circular prismatic member Ac cross-sectional area for use in the assessment of a non-circular prismatic member in compression Aeff effective area of a plate with reinforcement Aeff,i effective area of a component i of a non-circular prismatic member in compression Af cross-sectional area of a semi-compact section of a non-circular prismatic member Ai cross-sectional area of the ith component comprising the structural member Ao the area enclosed by the median line of the perimeter material of a section Ap fully plastic effective cross-sectional area of a non-circular prismatic member At cross-sectional area for use in the assessment of a non-circular prismatic member in tension Av effective shear area of a non-circular prismatic member in the direction being considered Bmaf member moment amplification factor for the axis under consideration Bs overall breadth of cross-section bw width of the wall of a component forming the closed perimeter of a section b effective width of a component b1 width of base plate b2 width of reinforcing plate Cmr moment reduction factor Cx critical elastic buckling coefficient D outside diameter of a tubular Ds overall depth of cross-section dw,lim limiting equivalent head of water di distance between the centroid of the ith component and the plastic neutral axis . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 28 © ISO 2023 – All right reserved E Young's modulus of steel (elastic modulus) e eccentricity between the axis used for structural analysis and that used for structural strength checks ea effective eccentricity between the axis used for structural analysis and that used for structural strength checks for class 3 members Fcr reduced material strength Fy yield strength in stress units Fyeff effective yield strength of the cross-section of a non-circular prismatic member in stress units Fyi yield strength of the ith component of the cross-section of a non-circular prismatic member in stress units Fymin minimum yield strength of all components in the cross-section of a non-circular prismatic member (minimum value of Fyi, in stress units) Fy,ltb yield strength, Fy of the material that first yields when bending about the minor axis g acceleration due to gravity h subscript referring to the component that produces the smallest value of Ppl I second moment of area Ie effective second moment of area of a non-circular prismatic member cross-section If second moment of area of a plastic, a compact or a semi-compact section of a non-circular prismatic member cross-section Ipt polar moment of inertia of a tubular Ipp polar moment of inertia a non-circular prismatic member I1 major axis second moment of area of the gross cross-section I2 minor axis second moment of area of the gross cross-section J torsion constant K effective length factor Lb effective length of a beam-column between supports Lp limiting plastic length Lr limiting unbraced length for inelastic torsional bucking Lub unbraced length of member for the plane of flexural buckling Mb representative bending moment strength of a tubular or a non-circular prismatic member Mby, Mbz representative bending moment strength about member y- and z-axes, respectively . 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Printed / viewed by: 29 Mp plastic moment strength of a tubular or a non-circular prismatic member Mpy, Mpz plastic moment strengths of a tubular or a non-circular prismatic member about member y- and z-axes, respectively Mu bending moment in a member due to factored actions determined in an analysis that includes global P-Δ effects Mua amplified bending moment determined from Mue Mue corrected effective bending moment determined from Mu Muay, Muaz amplified bending moments due to factored actions about member y- and z-axes, respectively Muey, Muez corrected bending moments due to factored actions about member y- and z-axes, respectively Muy, Muz bending moments due to factored actions about member y- and z-axes, respectively, determined in an analysis that includes global P-Δ effects Pa representative axial compressive strength of a tubular PE Euler buckling capacity Pn representative axial compressive strength based on local strength for column buckling of a non-circular prismatic member Pp representative axial strength of a non-circular prismatic member Ppl representative local axial compressive strength of non-circular prismatic member prismatic members Pt representative axial tensile strength of a non-circular prismatic member Pu axial force in a member due to factored actions determined in an analysis that includes global P-Δ effects Put axial tensile force due to factored actions Puc axial compressive force due to factored actions Pv representative shear strength of a tubular Pvy, Pvz are the representative shear strengths in the local y- and z-directions of a non-circular prismatic member, respectively Pxe representative elastic local buckling strength of a tubular Py plastic strength of a non-circular prismatic member Pyc representative local buckling strength of a tubular p depth below sea floor (zero if above sea floor) . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 30 © ISO 2023 – All right reserved rltb radius of gyration about the minor axis when used for lateral-torsional buckling considerations r radius of gyration for the plane of flexural bending rt maximum distance from centroid to an extreme fibre for torsional shear check Se reduced effective section modulus of a slender section of a non-circular prismatic member Sf elastic section modulus of a semi-compact section of a non-circular prismatic member Sy, Sz section moduli for use in the assessment of a non-circular prismatic member in flexure Tu torsional moment due to factored actions Tv representative torsional strength of a tubular t wall thickness of a tubular t1 thickness of base plate t2 thickness of reinforcing plate tf thickness of a flange component tw thickness of a web component V beam shear due to factored actions Vy, Vz beam shears due to factored actions in the local y- and z-directions, respectively yi distance from the neutral axis associated with Ie to the critical point i Zp fully plastic (effective) section modulus α factor that varies depending on the applied loading γ′ submerged (effective) unit weight of soil γ R,Pa partial resistance factor for axial strength of a non-circular prismatic member γ R,Pb partial resistance factor for bending strength of a non-circular prismatic member γ R,Pcl partial resistance factor for local axial compressive strength of a non-circular prismatic member γ R,Pt partial resistance factor for axial tensile strength of a non-circular prismatic member γ R,Pc partial resistance factor for axial compressive strength of a non-circular prismatic member γ R,Pv partial resistance factor for torsional and beam shear strength of a non-circular prismatic member γ R,Tb partial resistance factor for bending strength of a tubular γ R,Tt partial resistance factor for axial tensile strength of a tubular . 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Printed / viewed by: 31 γ R,Tc partial resistance factor for axial compressive strength of a tubular γ R,Tv partial resistance factor for torsional and beam shear strength of a tubular k buckling coefficient λ column slenderness parameter λh ratio b/t or 2R/t as applicable for component h λc prismatic column slenderness parameter for a non-circular prismatic member λr elastic plate slenderness parameter λp plastic plate slenderness parameter λplim limiting plate slenderness ratio λpo plate slenderness ratio coefficient η exponent for biaxial bending, a constant dependent on the prismatic member cross-section geometry ρ reduction coefficient ρw mass density of water σ1 compressive stress if σ2 tensile or the larger compressive stress if σ2 is also compressive σ2 tensile stress if σ2 tensile or the smaller compressive stress if σ2 is compressive ψ ratio of compression to bending stress 4.2 Abbreviated terms ALE abnormal-level earthquake ALS abnormal/accidental limit state BS base shear BSTF base shear transfer function CD chart datum DAF dynamic amplification factor ELE extreme level earthquake FE finite element FLS fatigue limit state IACS International Association of Classification Societies LAT lowest astronomical tide LRFD load and resistance factor design LTB lateral torsional buckling MPM most probable maximum . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 32 © ISO 2023 – All right reserved MPME most probable maximum extreme MSL mean sea level OCR over-consolidation ratio PDF probability density function PSIIP project specific in-service inspection programme RCS recognized classification society ROV remotely operated vehicle RPD rack phase difference SCF stress concentration factor SDOF single degree-of-freedom SLS serviceability limit state SSA-E site-specific assessment for the elevated condition SSA-I site-specific assessment for installation and removal SWL still water level TRS tropical revolving storm ULS ultimate limit state VIV vortex induced vibration 5 Overall considerations 5.1 General 5.1.1 Interaction with SSA-I The site-specific assessment of a jack-up normally comprises the two parts, an SSA-E, adressed in this document, and an SSA-I. While different personnel can carry out these assessments, much of the same information is used in both, including:  jack-up data;  geotechnical data;  geophysical information. Conversely, there is other data that is only used in an SSA-E or only used in an SSA-I. For example, the metocean extremes are used in an SSA-E only whereas the normally expected metocean conditions and propensity for squalls are used in an SSA-I only. Complicating the issue is that much of the data used for the SSA-I is most efficiently obtained at the same time as the data collected for the SSA-E (e.g. soil data). Failure to collect all the data required for both analyses at the same time can be costly and inefficient. . No further reproduction or distribution permitted. Printed / viewed by: 33 The normal expectation is that the SSA-E will be undertaken before the SSA-I. However, there can be cases in which this order is reversed, e.g. when the SSA-E is likely to produce a favourable conclusion but emplacing the jack-up could be problematic. There can be cases in which the results of the SSA-E can affect how the jack-up is to be emplaced on site. Some examples include:  required heading;  required preloading level;  proximity to adjacent structures;  limits on cantilever extension;  site remediation e.g. gravel bags, etc. These limitations should be passed on to those undertaking the SSA-I. 5.1.2 Competency Assessments undertaken in accordance with this document shall be performed only by persons competent through education, training and experience in the relevant disciplines. 5.1.3 Planning Adequate planning shall be undertaken before a site-specific assessment is started. The planning shall include the determination of all assessment situations relevant for the site under consideration. The assessment criteria shall be in accordance with Clause 13. 5.1.4 Assessment situations and associated criteria The assessment situations shall include both extreme events and operational modes because the critical mode of operation is not always obvious. The assessor shall use site-specific metocean, earthquake and geotechnical data, as applicable, for the assessment. The assessment situations and associated criteria are jointly specified in the remainder of this document. They form one whole and shall not be separated from one another. For mobile offshore drilling units operating in regions subject to sea ice and icebergs, the requirements of this document shall be supplemented with the relevant provisions relating to ice actions contained in ISO 19906 and procedures for ice management contained in ISO 35104. See 10.8 and A.10.8. NOTE In some cases, ice actions can be mitigated by an ice management plan and/or seasonal operations. 5.1.5 Reporting The assessor should prepare a report summarizing the inputs, assumptions and conclusions of the assessment. A recommended contents list is given in Annex G. 5.1.6 Regulations Each country can have its own set of regulations concerning offshore operations. It is the responsibility of the operator and jack-up owner to identify the applicable rules and regulations, depending upon the site and type of operations to be conducted. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 34 © ISO 2023 – All right reserved 5.1.7 Classification of unit This document is applicable to independent leg jack-ups that are structurally sound and adequately maintained. To achieve this, the unit shall either:  hold a valid classification society certification from an RCS throughout the duration of the operation at the specific site subject to assessment; or  have been verified by an independent competent body to be structurally fit for purpose for elevated situations and are subject to periodic inspection, both to the standards of an RCS. Jack-ups that do not conform with this requirement shall be assessed in accordance with the provisions of ISO 19902, supplemented by methodologies from this document, where applicable. 5.2 Assessment approach This subclause provides an overview of the data required, the assessment methodology, and the acceptance criteria. An example of a flow chart for extreme storm assessment is shown in Figure 5.2-1. Annex A provides additional information and guidance, including detailed calculation methodology. Annex B specifies the partial factors for use in the assessment. Annexes C to F provide supplementary information or alternative calculation methodologies. Annex G provides a recommended contents list for the assessment report. Annex H provides regional information and provision for Norway and US Gulf of Mexico. ISO/TR 19905-2 provides background to some of the recommendations given in this document and a detailed sample calculation. Other assessment methodologies may be applied, provided that they have been shown to give a level of structural reliability equivalent, or superior, to that implicit in this document. The assessment of the jack-up can be carried out at various levels of complexity as expanded in a), b) and c) (in order of increasing complexity). The objective of the assessment is to show that the acceptance criteria of Clause 13 are met. If this is achieved at a certain complexity level, there is no requirement to consider a higher complexity level. In all cases, the adequacy of the foundation shall be assessed to level b) or c). a) Compare assessment situations with design conditions or other existing assessments determined in accordance with this document. b) Carry out appropriate calculations in accordance with the simpler methods (e.g. pinned foundation, SDOF dynamics) given in this document. Where possible, compare results with those from existing more detailed/complex (e.g. secant or yield interaction foundation model, time domain dynamics) calculations. c) Carry out appropriate detailed calculations in accordance with the more complex methods (e.g. secant, yield interaction or continuum foundation model, time domain dynamics) given in this document. . No further reproduction or distribution permitted. Printed / viewed by: 35 NOTE 1 A cross-referenced clause number includes reference to the corresponding clause in Annex A. NOTE 2 This figure does not fully address: Long term applications (Clause 11); Temperature (13.10); Earthquake (6.6, 7.7, 8.8.8, 10.7) Figure 5.2-1 — Flow chart for the overall extreme storm assessment . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 36 © ISO 2023 – All right reserved 5.3 Selection of assessment situations ISO 19900 divides the assessment situations into four categories as described in this subclause. a) Operational and Extreme assessment situations. The site-specific assessment shall include evaluation of extreme assessment situations with combinations of extreme level metocean actions and the associated storm mode gravity actions. Earthquake and ice actions shall also be considered in combination with the associated permanent and operational gravity actions; however, evaluation is required only in some areas of the world. The applicable partial action and resistance factors for the extreme assessment situation and exposure level shall be as summarized in Annex B. For the associated Ultimate Limit State (ULS), the integrity of the structure should be unimpaired, but damage to the non safety-critical (secondary) structure of the jack-up can be tolerated. Extreme assessment situations shall be assessed with the jack-up in the most critical operating configuration (increased variable load, cantilever extended and unequal leg loads) when the extreme level metocean conditions are  within the defined serviceability limits for the jack-up (i.e. the metocean conditions are less severe than those defined for changing to the elevated storm configuration), or  severe weather occurs with insufficient warning for the unit to be put in to storm configuration, e.g. squalls. Consideration of the operating configuration is particularly important when the factored functional actions are close to the preload reaction and a small additional leg reaction due to metocean actions can cause significant additional penetration. Operational assessment situations use the operational metocean conditions with the associated operating mode gravity actions and configuration. For jack-ups where the operations manual permits increases in, or redistribution of, the variable load with reduced metocean conditions (operating configuration, nomograms, etc.), the assessor shall establish an operational assessment situation. Where nomograms are used, a representative selection of situations applicable to the site shall be assessed (e.g. the extreme storm event and one or more less severe metocean conditions). NOTE The situations above are often found in benign areas where the extreme level metocean conditions are within the defined serviceability limits for the jack-up and do not exceed the limits for changing the jack-up to the elevated storm configuration. b) Serviceability assessment situations Serviceability assessment situations are normally covered by the limits specified in the operations manual and, therefore, it is not necessary to assess it unless the operational configuration requirements for the site are outside those limits. However, the requirements of a) above always apply. c) Fatigue assessment situations The FLS is generally addressed at the design stage. It is not necessary to evaluate fatigue unless the jack-up is to be deployed for a long-term operation (see Clause 11). d) Abnormal/Accidental assessment situations Accidental assessment situations, addressing abnormal environmental events or accidental events, are generally addressed at the design stage and it is not necessary to evaluate them in the . No further reproduction or distribution permitted. Printed / viewed by: 37 assessment unless there are unusual risks at the site under consideration. Abnormal situations shall be assessed when necessary e.g. abnormal level earthquake (ALE) or abnormal level ice assessment (ALS). 5.4 Determination of assessment situations 5.4.1 General A jack-up can be used in various modes at a single site (e.g. drilling mode/workover mode/tender mode/production mode). In each mode, the jack-up can be in the operating or storm survival configuration. Where more than one configuration is contemplated, the differences (e.g. the varying hull elevations required for each, skidding the cantilever in for a storm, reducing variable deck load) shall be considered in the assessment. The practicality of any required configuration change shall be evaluated and appropriate assumptions incorporated into the assessment calculations. Any required restrictions on the operations shall be included in the operating procedures. The assessment situations shall be determined from appropriate combinations of mode, configuration and limit state. Where the assessment indicates that an assessment situation does not meet the acceptance criteria of Clause 13, the assessment configuration may be adjusted to achieve acceptability, providing that any resulting deviations from the standard operating procedure of the jack-up are practically achievable, are documented and are communicated by the jack-up owner to their offshore personnel and, if relevant, to the operator. Alternatively, metocean data applicable to the season(s) of operation may be considered. 5.4.2 Reaction point and foundation fixity The assumed reaction point at the spudcan shall be documented in the assessment report. The jack-up's legs are normally assumed to be pinned at the reaction point. Any divergence from this assumption shall be stated. NOTE The assumption of pinned footings is a conservative approach for the bending moment in the leg in way of the leg-to-hull connection; see 8.6.3. 5.4.3 Extreme storm event approach angle The critical extreme storm event approach angles relative to the jack-up are usually different for the various checks that shall be made (e.g. strength versus overturning checks). The critical direction for each check shall be used. 5.4.4 Weights and centre of gravity For each limit state and configuration being assessed, the appropriate magnitude and position of the fixed and variable loads shall be used. The tolerances on both magnitude and position shall be considered when determining the weights and centres of gravity to use in the assessment. Where the location of the cantilever, substructure, etc., or the hull elevation, differ between the elevated operating and storm survival configuration, the practicality of making the changes required to achieve the storm survival configuration shall be established. 5.4.5 Hull elevation The hull elevation used in the assessment shall conform with the requirements specified in 13.6. Generally, this is the larger of that required to maintain adequate clearance with  adjacent structures, such as a fixed platform, and  the wave crest. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 38 © ISO 2023 – All right reserved 5.4.6 Leg length reserve The assessor shall determine the necessity for a reserve of leg length above the upper guides to account for any uncertainty in the prediction of penetration and to provide a contingency against settlement or scour. Leg length reserve requirements are given in 13.7. 5.4.7 Adjacent structures The potential interaction of the jack-up with any adjacent structures shall be reported, as appropriate. Aspects requiring consideration by the operator include the effects of potential contact with adjacent infrastructure (jacket, subsea structure, pipeline, etc.), the effects of the jack-up's spudcans on the foundation of the adjacent structure and the effects of relative motions on well casing, drilling equipment and well surface equipment (risers, connectors, flanges, etc.). 5.4.8 Other The assessment is based on the best available information on the conditions at the site. In some cases, it can be found that the actual conditions at the site are inconsistent with the information used, e.g. penetration, eccentricity of spudcan support, orientation, leg inclination. In other cases, the effects of factors such as large guide clearances and sensitivity to RPD cannot be properly quantified prior to installation. In all such cases, the validity of the assessment shall be confirmed once the jack-up has been installed. NOTE The RPD is usually a good indicator of the degree of eccentricity and the acceptability of the resulting action effects when elevated. 5.5 Exposure levels 5.5.1 Determination of exposure level Jack-ups can be categorized by various levels of exposure to determine criteria that are appropriate for their intended service and the assessment situations. The exposure levels are determined by consideration of life-safety and of environmental and economic consequences as described in ISO 19900:2019, 7.3. 5.5.2 Exposure level L1 Occupied, non-evacuated jack-ups and jack-ups with high environmental consequence shall be classified to the most onerous exposure level, L1, for all assessment situations. For extreme storm assessments L1 jack-ups shall be assessed either for the 50 year independent extremes with partial action factor of 1,15 or for the 100 year joint probability metocean data with partial action factor of 1,25 (see 8.8.1 and Annex B). NOTE 1 The equivalency of the alternatives was justified for temperate climates. NOTE 2 During the TRS season in TRS areas, it can be appropriate to also assess to the ALS for abnormal storm conditions. For example the 2 500 year return period full population is typically used in the Gulf of Mexico. 5.5.3 Exposure level L2 Occupied-evacuated jack-ups, where potential life-safety and environmental pollution consequences have been mitigated, may be classified as exposure level L2. The requirements given in ISO 19900:2019, 7.3.3 shall be applied. For extreme storm assessments, L2 jack-ups shall be assessed for the 50 year independent extremes or 100 year joint probability metocean data that can be reached at the site prior to evacuation being completed (e.g. 50 year sudden hurricane in tropical revolving storm areas) with allowance for forecast uncertainty, when appropriate. The assessment shall use the partial factors applicable to L1. . No further reproduction or distribution permitted. Printed / viewed by: 39 The slope of the sudden tropical storm hazard curve can be steeper than that of storms in other areas of the world and of full population tropical storms. The unoccupied post-evacuation case shall be considered in accordance with criteria to be agreed between the jack-up owner and the operator taking account of the slope of the sudden storm hazard curve and the time required to place the jack-up in the storm mode for the unoccupied condition to ensure adequate reliability of the jack-up in the sudden tropical storm ULS condition. Annex H.3 contains useful information on such conditions, developed for the US Gulf of Mexico, that could be used for other tropical storm areas. Any deviation from the storm mode given in the marine operations manual shall be clearly identified and agreed between the jack-up owner and the operator. NOTE Operational and evacuation procedures are outside the scope of this document, however significant time can be required to prepare the jack-up for the unoccupied condition. 5.5.4 Exposure level L3 Jack-ups that meet the requirements for L2 and that are not normally occupied and may be classified as exposure level L3. The requirements given in ISO 19900:2019, 7.3.4 shall be applied. For extreme storm assessments L3 jack-ups shall be assessed to criteria that shall be agreed between the jack-up owner and the operator. 5.5.5 Exposure level for earthquake For earthquake, a jack-up shall be assessed as L1 unless it is normally unoccupied and meets the requirements given in ISO 19900:2019, 7.3.4, where item c) is changed to "visits are not planned to last more than 24 h on jack-ups in regions with seismic zones 1 to 4. When normally unoccupied, the earthquake assessment requirements shall be agreed between the jack-up owner and the operator. 5.6 Analytical tools Guidance is given in ISO 19900:2019, Clauses 11 and A.11 on the use and validation of analytical tools and models. It should be noted that many software suites do not adequately address jack-up specific issues, such as time domain dynamics, foundations, large displacement effects and appropriate code checks. 6 Data to assemble for each site 6.1 Applicability Clause 6 describes the data that are required to undertake an assessment. In this document, the field is the general area where the jack-up is to operate; the site is the specific position/orientation within the field. The site data are normally a subset of the field data. The data that should be included in the assessment report are listed in Annex G, which can be used as a check list. 6.2 Jack-up data The jack-up data required to perform an assessment include the following:  jack-up type;  installed leg length;  latest revision of the drawings, specifications and the operations manual;  any proposed deviations from the operations manual limits for the intended operation;  data pertaining to the strength, stiffness and operation of the leg-to-hull connection; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 40 © ISO 2023 – All right reserved  proposed lightship and variable load and centres of gravity for each configuration, accounting for any changes that are not included in the latest revision of the operations manual;  preloading capacity or pre-drive capability;  limiting spudcan capacity, e.g. reactions and bearing pressure distribution(s) used in the design cases;  design parameters including, where applicable, RPD limits  details of any relevant modifications. 6.3 Site and operational data The site data should include the site coordinates, sea floor topography and water depth referenced to a clearly specified datum, e.g. lowest astronomical tide (LAT) or chart datum (CD). Be aware that charts derived for use by comparatively shallow draft shipping are often not sufficiently accurate for siting jack-ups. At platform sites, platform drawings, the required hull elevation or the required clearances with the platform, the jack-up heading and other interface data shall be obtained from the platform operator. The assessor can use directional metocean data to optimize the jack-up heading. When directional metocean data are used in the assessment, the jack-up heading shall be specified. The overall reliability of the jack-up should not be compromised by the use of such criteria. The data provided by the operator shall include the proposed mode of use (drilling, production, accommodation, etc.) and the number and size of any supported risers or conductors. The life-safety and consequence category of adjacent infrastructure while the jack-up is on site shall be provided. 6.4 Metocean data It is of prime importance to obtain appropriate metocean data for the site with due recognition of the quality of the data. Site-specific data shall be obtained from or on behalf of the operator for the following: a) water depth (LAT or CD); b) tide and storm surge; c) wave data:  significant wave height and spectral peak period (stating whether intrinsic or apparent, as discussed in A.7.3.3.5),  maximum wave height and associated period (stating whether intrinsic or apparent, as discussed in A.7.3.3.5),  abnormal wave crest elevation (see A.6.4.2.4). d) current velocity and profile; e) wind speed and profile. Further reference to metocean data can be found in Table A.7.3-1. . No further reproduction or distribution permitted. Printed / viewed by: 41 Omnidirectional data can be sufficient but, in particular circumstances, directional data can also be required. Other data, such as the following, shall be evaluated, when applicable:  marine growth distribution;  icing;  lowest average daily air temperatures, etc. Directionality of wind, wave and current may be considered if accurate data are available. For deterministic analysis, wave kinematics factors may be applied to account for wave short-crestedness and jack-up leg spacing; see A.6.4.2.3. General information on metocean data are given in ISO 19901-1. Details of the required metocean data for jack-up site-specific assessment are given in A.6.4. Either the 50 year return period of individual extremes or the 100 year return period of joint probability metocean data shall be used for the site-specific assessment of occupied jack-ups. Partial action factors for the alternative return periods are given in 5.5.4, 8.8.1 and Annex B. NOTE To provide consistent reliability levels, different action factors are used with actions determined for a 50 year return period of individual extremes and for a 100 year return period of joint probability metocean data. As a minimum, a occupied-evacuated jack-up shall be assessed for the 50 year independent extremes or 100 year joint probability metocean data that can be reached while the jack-up is still occupied; see 5.5.4. For example in a TRS area, consideration may be given to the use of a 50 year return period “sudden hurricane”. As a minimum, an unoccupied jack-up shall be assessed to an agreed exposure level; see Table 5.5-1. If the jack-up deployment is to be of limited duration, applicable (seasonal) data may be used for the months under consideration, including suitable contingency. 6.5 Geophysical and geotechnical data Site-specific geotechnical information applicable to the anticipated range of penetrations shall be obtained from or on behalf of the operator. The type and amount of geotechnical data required depend on the particular circumstances, such as the type of jack-up and previous experience at the site or nearby sites. Such information can include geophysical survey (sub-bottom profiler, side-scan sonar, bathymetry, magnetometer) data; boring/coring data; in situ and laboratory test data; and visual survey data. The field shall be evaluated for the presence of geohazards. Such hazards and their potential mitigations are described in Table A.6.5-1. For sites where previous operations have been performed by jack-ups of the same basic design, it can be sufficient to identify the location of the existing footprints, to assess the hazards associated therewith and refer to previous site data and preloading or penetration records; however, the accuracy of such information should be verified. At sites where there is any uncertainty, borings/corings and/or in situ testing (e.g. piezocone penetrometer tests) data are recommended at the planned site. Alternatively, the site can be tied-in to such data at another site by means of shallow seismic data, although care must be taken to assess the uncertainty of any such extrapolation. If data are not available prior to the arrival of the jack-up, it can be possible to take boring(s)/coring(s), etc., from the jack-up before preloading and jacking to full hull elevation. Suitable precautions should be taken to ensure the safety of the jack-up during this initial period on site and during subsequent preloading. The newly acquired soils data shall be analysed and assessed to ensure foundation safety during and after preloading. The soil data should be used to update the site-specific assessment as necessary. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 42 © ISO 2023 – All right reserved The site shall be evaluated for potential scour problems. These are most likely to occur at sites with high wave and/or current water particle velocity near a seabed that is composed of non-cohesive soils. See also 9.4.7. Certain sites prone to mudslides can involve additional risks. Such risks should be assessed by carrying out specialist studies. 6.6 Earthquake data Earthquake data shall be obtained through the use of ISO 19901-2. 6.7 Ice data Ice data shall be obtained through the use of ISO 19906 and ISO 35106. 7 Actions 7.1 Applicability This clause presents an overview of, and basic requirements for, the modelling of actions for site-specific assessment in accordance with this document. Details regarding methods and formulations that can be applied to calculate actions are presented in A.7, which also includes presentation of hydrodynamic formulations and coefficients for detailed and equivalent modelling of hydrodynamic actions on legs. In this clause and A.7, actions are presented as representative values. The representative actions shall be multiplied by the partial action factors as given in 8.8 prior to the determination of the assessment load cases. 7.2 General The following outlines the actions that shall be considered in general terms: a) metocean actions: 1) actions on legs and other structures from wave and current; 2) actions on hull and exposed areas (e.g. legs) from wind. c) functional actions: 1) fixed actions; 2) actions from variable load. d) indirect actions resulting from responses: 1) displacement-dependent effects; 2) accelerations from dynamic response. e) earthquake actions; f) ice actions; g) other actions. . No further reproduction or distribution permitted. Printed / viewed by: 43 7.3 Metocean actions 7.3.1 General Wind, wave and current actions are typically considered to act simultaneously and from the same direction. This colinearity should normally be assumed. The directionality of wind, wave and current may be considered when it can be demonstrated that such directionality is applicable at the site under consideration. 7.3.2 Hydrodynamic model The hydrodynamic modelling of the jack-up leg can be carried out by utilizing “detailed” or “equivalent” techniques. The hydrodynamic models shall represent all structures and appurtenances subjected to wave and current action. The effect of different hydrodynamic properties in different directions shall be represented as appropriate for the analysis. Hydrodynamic (drag and inertia) coefficients shall be selected that are appropriate for the flow regime of the actual jack-up leg structure and chosen wave theory. Applicable test results may be used to select the coefficients for non-circular members (and not the complete leg). The effects of raw water piping, ladders and other appurtenances shall be considered in the calculation of the hydrodynamic coefficients for the legs. The effect of marine growth on the actions shall be considered. Because jack-ups are mobile, opportunities are available to clean the leg to reduce hydrodynamic actions. 7.3.3 Wave and current actions Wave and current actions on the legs and appurtenances (e.g. raw water tower) shall be computed using the Morison equation and an appropriate hydrodynamic model. A wave theory appropriate to the wave height, period and water depth shall be used for the determination of particle kinematics. Wave kinematics for the calculation of actions caused by waves shall be derived from the intrinsic wave period or the intrinsic wave frequency. NOTE When waves are superimposed on a (uniform) current, the intrinsic reference frame for the waves travels at the speed and in the direction of the underlying current. An observer travelling at the same speed and in the same direction as the current is stationary with respect to the intrinsic reference frame and, therefore, measures the intrinsic wave period (see A.7.3.3.5 and ISO 19901-1:2015, 8.4.4 and A.8.4.3). The wave has only an intrinsic wave length; there is no apparent wave length. The derived actions are directly affected by the current profile chosen and the method used to modify the profile when the height of the water column varies in the presence of waves. Guidance is provided in A.6.4.3. VIV is normally considered to be covered by class, but should be checked for jack-ups with large-diameter tubular legs when the current velocity exceeds that used in the design; see for example DNV-RP-C205 (DNV 2021d)[60]; Grundmeier, Campbell and Wesselink (1989)[85] and Blevins (1990)[26]. 7.3.4 Wind actions All structures and appurtenances subjected to wind action shall be considered. Wind actions shall be computed using wind velocity, wind profile and exposed areas. Appropriate wind velocities and wind profiles shall be used, guidance is given in A.6.4.6. These actions can be calculated using appropriate formulae and coefficients or can be derived from applicable wind tunnel tests. Generally, block areas are used for the hull, superstructures and appurtenances. Wind actions on legs can be a dominant factor for jack-ups operating at less than their maximum design water depth. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 44 © ISO 2023 – All right reserved The potential effects of wind-induced VIV should be considered, see for example DNV-RP-C205 (DNV 2021d)[60]; Grundmeier, Campbell and Wesselink (1989)[85] and Blevins (1990)[26]. 7.4 Functional actions For functional actions, it is usual to consider the jack-up with the maximum permitted variable load for structural checks and with the minimum anticipated variable load (often 50 %) for the overturning calculation. If the assessment of the jack-up shows that it is marginal in one of these configurations, consideration may be given to limiting the variable load to a lower or higher level (depending on the critical parameter), providing the jack-up can be successfully operated under such restrictions. The assessor shall document any restrictions on the variable load that apply to the operating limits at the site and communicate them to the jack-up owner. The intent is to ensure that these limits are included in the operating procedures for the site. 7.5 Displacement dependent effects Indirect forces that are a consequence of the displacement of the structure and its foundation shall be considered in the analysis. The effects are due to the first-order sway, foundation settlement, and to the enhancement due to the increased flexibility of the legs in the presence of axial actions (Euler amplification); see A.8.8.6. 7.6 Dynamic effects Indirect forces due to dynamic response of the jack-up shall be considered and are particularly important for sea states having significant energy near the natural periods of the jack-up or multiples thereof; see 10.5.2 and 10.5.3. Dynamic effects shall be included in earthquake analyses (see 10.7) and can be important for ice action responses. 7.7 Earthquakes Actions and action effects due to earthquakes shall be considered where appropriate; see 8.8.8 and 10.7. 7.8 Ice actions Actions and action effects due to ice shall be considered where appropriate; see 10.8 and A.10.8. 7.9 Other actions Additional leg moments due to leg inclination resulting from leg-to-hull clearances and hull inclination shall be considered as described in 8.3.6 and 10.5.4. Other types of action, for example actions due to icing and snow or sudden drop due to reservoir subsidence can occur in certain geographical regions. These actions shall be computed and applied in combination with other appropriate concurrent actions. 8 Structural modelling 8.1 Applicability This clause presents methods for the development of an analytical model of an independent leg jack-up structure. Included in a jack-up structure are the legs, hull, leg-to-hull connection, and spudcans. The modelling of the foundation is presented in Clause 9. The modelling provisions cover the generation of stiffness, self-weight, mass and application of actions. . No further reproduction or distribution permitted. Printed / viewed by: 45 In this clause, and the corresponding A.8, values for actions, forces, reactions, masses, stiffnesses, moments and geometry are presented as representative values unless indicated otherwise. Actions shall be multiplied by the partial action factors as given in 8.8 prior to the determination of the assessment load cases. 8.2 Overall considerations 8.2.1 General In general, structural modelling for the assessment of a jack-up shall achieve the following objectives for both static and dynamic responses:  realistic global response (e.g. displacement, base shear, overturning moment) for the jack-up under the applicable environmental and functional actions;  suitable representation of the leg, leg-to-hull connection and the leg-foundation interaction, including non-linear effects as necessary;  adequate detail to enable realistic assessment of the leg structure, the structural/mechanical components of the jacking and/or fixation system and the foundation. 8.2.2 Modelling philosophy The purpose of structural modelling is to estimate the forces and displacements in a structure when subjected to the calculated applied actions. The distribution of global actions and estimates of internal forces and displacements can be obtained through the use of simplified, equivalent modelling techniques. To determine displacements and forces in the leg, leg-to-hull connection, leg/spudcan connection and local hull displacements, a finite element (FE) model shall be developed. An explicit model of the conductor is rarely warranted, however the loading from conductor(s) shall be included. 8.2.3 Levels of FE modelling In general, a jack-up model shall include the leg, leg-to-hull connection and representative hull structure. FE models can contain combinations of detailed and simplified structural modelling. Four modelling techniques are summarized below, with further detail given in 8.3 through 8.6: a) fully detailed model of all legs and leg-to-hull connections, with detailed or representative stiffness model of hull and spudcan; b) equivalent leg (stick model) and equivalent hull; equivalent stiffness model of all legs and spudcans, equivalent leg-to-hull connection springs and representative beam-element hull grillage; c) combined equivalent/detailed leg and hull; simplified lower legs and spudcans, detailed upper legs and leg-to-hull connections with detailed or representative stiffness model of the hull; d) detailed single leg (or leg section) and leg-to-hull connection model. This model shall be used in conjunction with the reactions at the spudcan or the forces and moments in the vicinity of the lower guide obtained from model b). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 46 © ISO 2023 – All right reserved 8.3 Modelling the leg 8.3.1 General The leg can be modelled as a “detailed leg”, an “equivalent leg” or a combination of the two. 8.3.2 Detailed leg A “detailed leg” model consists of all structural members, such as chords, horizontal, diagonal and internal braces of the leg structure and the spudcan (if required). Each structural component of the leg is represented by one or more appropriate finite elements. In the development of a detailed leg model, the use of beam elements is generally accepted practice. However, other finite elements can be utilized, when necessary, to accurately represent individual structural members. 8.3.3 Equivalent leg (stick model) An “equivalent leg” model consists of a series of collinear beam elements simulating the complete leg structure. In this model, a series of one or more beam elements represents the overall stiffness characteristics of the detailed leg. 8.3.4 Combination of detailed and equivalent leg In this model, the areas of interest are modelled in detail and the remainder of the leg is modelled as an equivalent leg. 8.3.5 Stiffness adjustment The leg stiffness used in the overall response analysis can account for a contribution from a portion of the rack tooth material. Unless detailed calculations indicate otherwise, the assumed effective area of the rack teeth should not exceed 10 % of their maximum cross-sectional area. When checking the strength of the chords, the chord properties should be determined discounting the rack teeth. 8.3.6 Leg inclination The additional leg moment due to leg inclination resulting from leg-to-hull clearances and hull inclination shall be considered (see 10.5.4), but it is not necessary that it be explicitly modelled. The designed-in leg inclination of slant-leg jack-ups shall be modelled explicitly. 8.4 Modelling the hull 8.4.1 General The hull structure shall be modelled so that the actions can be correctly transferred to the legs and the hull flexibility is represented accurately. 8.4.2 Detailed hull model The detailed hull model shall include primary load carrying structures, explicitly modelled with appropriate finite elements. 8.4.3 Equivalent hull model If a detailed hull model is not used, an equivalent hull model shall be constructed using a grillage of beams. . No further reproduction or distribution permitted. Printed / viewed by: 47 8.5 Modelling the leg-to-hull connection 8.5.1 General The leg-to-hull connection controls the distribution of leg bending moments and shears carried between the guides and the jacking/fixation system. In the elevated mode, the most heavily loaded portion of the leg is normally within the vicinity of the leg-to-hull connection. The model shall provide the means to identify any possible leg-to-hull contact at locations other than the guides. 8.5.2 Guide systems The guide structures restraining the chord members shall be modelled, accounting for clearances and their direction of action. When chord-to-guide contact occurs in the span between chord-brace connections, significant local chord bending moments can occur. Therefore, various guide positions shall be investigated. 8.5.3 Elevating system The elevating systems shall be modelled using either the stiffness derived from detailed analysis or from testing. Generally, the manufacturer specifies this information. 8.5.4 Fixation system If the jack-up is equipped with a fixation system, e.g. rack chocks, it shall be modelled to resist both vertical and horizontal forces, using appropriate stiffnesses. 8.5.5 Shock pad  floating jacking systems For floating jacking systems, the shock pad stiffness shall be modelled and the shock pad shall be modelled to resist vertical compressive forces only. Generally, the manufacturer specifies the stiffness information. 8.5.6 Jackcase and associated bracing The jackcase or jackhouse structures and associated bracing shall be modelled based on their actual stiffness. 8.5.7 Equivalent leg-to-hull stiffness The model shall represent the overall stiffness characteristics of the leg-to-hull connection. 8.6 Modelling the spudcan and foundation 8.6.1 Spudcan structure The spudcan structure shall be modelled with sufficient detail to accurately transfer the seabed reaction into the leg structure. Where there is insufficient data available regarding the structural strength of the spudcans, the suitability of the spudcans for the site shall be determined from applicable analyses. 8.6.2 Seabed reaction point Selection of the reaction point shall be based on the penetrations (see 9.3.2) and shall consider any anticipated horizontal eccentricity. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 48 © ISO 2023 – All right reserved 8.6.3 Foundation modelling For the analysis of an independent leg jack-up unit in the elevated storm mode, the foundations may be assumed to behave as pinned supports, which are unable to sustain moment. This is a conservative approach for the bending moment in the leg in way of the leg-to-hull connection. In cases where the inclusion of rotational foundation fixity is justified and is included in the structural analysis, the non-linear soil-structure interaction effects shall be taken into account. The model shall include the interaction of rotational, lateral and vertical soil forces. Methods of establishing foundation fixity are given in Clause 9. When fixity brings the structural natural period closer to the excitation frequency, the inclusion of foundation fixity can amplify the response and shall, therefore, be considered. The spudcans, the leg-to-can connection and the lower parts of the leg are addressed at the design stage. In cases where the spudcan reactions could exceed the design values the reactions used to assess these areas shall be obtained from a foundation model that provides a high estimate of the spudcan moment. For foundation modelling under earthquake excitation see 10.7 and A.10.7. 8.7 Mass modelling The mass model shall reflect the mass distribution of the jack-up. The model shall include structural and non-structural mass, including entrapped fluids, marine growth, added mass, etc. The added mass shall be computed based on the displaced volume of the submerged components, including marine growth, acting in the direction of motion normal to the component. The mass of the variable load (e.g. consumables stored on/within the hull) shall be included in the mass model. Some actions that are included in the variable load are not masses and shall not be included in the mass model (e.g. conductor tension and hook loads).  The structural mass shall include:  legs;  hull structure;  spudcans.  The non-structural mass shall include:  hull equipment and outfitting;  mass of the variable load;  sea water supply system;  leg appurtenances;  marine growth;  entrapped water in flooded members and spudcans.  Added mass shall include contributions from: . No further reproduction or distribution permitted. Printed / viewed by: 49  submerged legs and leg components, e.g. chords and braces;  sea water caissons; For earthquake assessments see 10.7 for additional guidance on the mass model. 8.8 Application of actions 8.8.1 Assessment actions 8.8.1.1 General The assessment load case, Fd, shall be determined using the following generalized form in which the partial factors are applied before undertaking the structural response analysis to ensure that the non-linear behaviour is properly captured, as given in Formula (8.8-1): df,GFf,VVf,Eef,De()FGGEDγγγγ=+++ (8.8-1) where GF are actions due to the fixed load positioned such as to adequately represent their vertical and horizontal distribution; see 8.8.2; Gv are actions due to maximum or minimum variable load, as appropriate, positioned at the most onerous centre of gravity location applicable to the configurations under consideration; see 8.8.2; Ee are metocean actions due to the extreme storm event; see 8.8.4 (Ee = 0 for earthquake assessment); De is an equivalent set of inertial actions representing dynamic extreme storm effects; see 8.8.5 (De = 0 for stochastic storm assessment in accordance with 10.5.3); De is an equivalent set of inertial actions induced by the ELE or ALE ground motion for earthquake assessment; see 8.8.8; γ are the partial action factors, as given in 8.8.1.2 to 8.8.1.4. NOTE See Annex B, which contains all of the applicable factors for use in a site-specific analysis. The actions and action effects that shall be included in the analysis are outlined in 8.8.2 to 8.8.8. 8.8.1.2 Two-stage deterministic storm analysis The partial action factors for the deterministic storm analysis described in 10.5.2 and A.10.5.2.2.3 shall be as given below:  γf,G = 1,0 and is applied to the actions due to fixed load;  γf,V = 1,0 and is applied to the actions due to the variable load;  γf,E = 1,15 when applied to the actions due to the 50 year return period independent extreme metocean data;  γf,E = 1,25 when applied to the actions due to the 100 year return period joint probability metocean data; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 50 © ISO 2023 – All right reserved  γf,D = 1,0 and is applied to the inertial actions due to dynamic response. 8.8.1.3 Stochastic storm analysis As discussed in A.10.5.3.2, in a stochastic storm analysis the metocean wind wave and current parameters are increased such that an action factor of 1,0 can be applied while achieving comparable global factored actions. Consequently, the stochastic storm analysis described in 10.5.3 is carried out using unfactored actions. The resulting partial action factors shall be as given below:  γf,G = 1,0 and is applied to the actions due to fixed load;  γf,V = 1,0 and is applied to the actions due to the variable load;  γf,E = 1,0 when applied to the metocean actions derived from the factored wind, wave and current metocean parameters, see 10.5.3, A.10.5.3;  γf,D = 1,0 and is applied to the inertial actions due to dynamic response. 8.8.1.4 Earthquake analysis 8.8.1.4.1 The partial action factors for ELE analysis described in 10.7 shall be as given below:  γf,G = 1,0 and is applied to the actions due to fixed load;  γf,V = 1,0 and is applied to the actions due to the variable load;  γf,E = 0,9 when applied to the ELE actions;  γf,D = 1,0 and is applied to the inertial actions induced by the ELE ground motion (Ee = 0). 8.8.1.4.2 The partial action factors for the ALE shall be as given below:  γf,G = 1,0 and is applied to the actions due to fixed load;  γf,V = 1,0 and is applied to the actions due to the variable load;  γf,E = 1,0 when applied to the ALE actions;  γf,D = 1,0 and is applied to the inertial actions induced by the ALE ground motion (Ee = 0). NOTE The apparent inconsistency between the earthquake partial action factors is due to the differences in the analysis methods used for the ELE and ALE assessments. The 0,9 partial action factor in conjunction with the normal resistance factors is taken from ISO 19902. The 0,9 partial factor was determined in the API calibration of LRFD against WSD. The ALE action factor of 1,0 is used in conjunction with a system survival assessment. 8.8.2 Functional actions due to fixed load and variable load 8.8.2.1 The actions due to fixed load (i.e. hull, legs, outfit, stationary and movable equipment) include:  weight in air including appropriate solid ballast;  weight of permanent enclosed liquid;  buoyancy. . No further reproduction or distribution permitted. Printed / viewed by: 51 8.8.2.2 The actions due to variable load, which comprises supplies or equipment that are expendable, readily removable, or consumable during operations, include:  weight of liquid and solid stores;  applied drilling and conductor loads;  weight of readily removable equipment. The actions due to fixed load and variable load shall be modelled to represent the correct vertical and horizontal weight and mass distribution. 8.8.3 Hull sagging Hull sagging resulting from distributed actions and hull flexibility can impose bending moments on the legs. It shall be verified that the amount of hull sag-induced moment transferred to the legs in the analytical model is appropriate given the operating procedures of the jack-up and site-specific conditions. 8.8.4 Metocean actions Wind actions on the legs and hull shall be modelled to represent their vertical and horizontal distribution. Wave/current actions on the leg and spudcan structures above the sea floor shall be modelled to represent their vertical and horizontal distribution. 8.8.5 Inertial actions The application of inertial actions depends on the dynamic approach adopted; see Clause 10. For the SDOF approach, the inertial actions are applied as horizontal force(s) acting through the hull centre of gravity. For deterministic storm analysis, with dynamics from a stochastic analysis, the forces are distributed to better approximate the dynamic overturning moment. Inertial actions should not normally be applied on the legs below the hull. 8.8.6 Large displacement effects P-Δ effects occur because the jack-up is a relatively flexible structure and is subject to lateral displacement of the hull (sideways) under assessment actions (see 7.5). P-Δ effects shall be included in the structural analysis. 8.8.7 Conductor actions An explicit model of the conductor is rarely warranted. However, the top tension and actions on the jack-up due to the factored hydrodynamic actions on the conductor(s) shall be included in the analysis, if applicable. 8.8.8 Earthquake actions See 10.7 and A.10.7 for earthquake actions. 8.8.9 Ice actions See 10.8 and A.10.8 for ice actions. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 52 © ISO 2023 – All right reserved 9 Foundations 9.1 Applicability This clause addresses the geotechnical considerations, soil-structure interaction, capacity, stiffness and hazards associated with the foundations that support independent leg jack-ups. Additional supporting information can be found in ISO 19901-4, however the provisions of this document shall take precedence in case of conflict. In this clause, and the corresponding A.9, values for actions, forces, loads, preload, reactions, resistances, capacity, moments, weights and geometry are presented as representative values unless indicated otherwise. The representative actions shall be multiplied by the partial action factors as given in 8.8 prior to the determination of the assessment load cases. NOTE The foundations of mat-supported jack-ups are not specifically covered in this document. 9.2 General Adequate geotechnical and geophysical information as outlined in 6.5 shall be gathered and used to assess the spudcan penetration and foundation stability of the jack-up at the site. See further guidance in A.6.5. Applicable information from previous operations, other surveys or activities in the area should be used in the assessment of the site. There are two objectives of gathering geotechnical and geophysical information. The first is to ensure that the foundation is adequate to carry static, cyclic, and transient forces without excessive settlement or movement. The second objective is to provide adequate information for foundation models of increasing sophistication for use in structural response analyses. The assessment shall consider:  the possible range of predicted leg penetrations;  the possibility of rapid leg penetration and/or punch-through;  likely scale of spudcan movements, e.g. due to consolidation, capacity exceedance;  the effects of cyclic loading;  the consequences of specific site conditions, such as are listed in 9.4. 9.3 Geotechnical analysis of independent leg foundations 9.3.1 Foundation modelling and assessment The purpose of preloading is to develop adequate foundation capacity to resist the forces on the foundation due to assessment events. During preloading, the jack-up should normally be capable of generating spudcan reactions in excess of the maximum vertical reactions due to the factored actions determined in the assessment. Where the preload is insufficient to meet the Level 2 assessment criteria, such preload can be acceptable, e.g. if justified by the Level 3 displacement check in 9.3.6. In some circumstances, the foundation capacities and stiffnesses from 9.3 are not sufficient for the unit to satisfy the acceptance criteria (Clause 13) based on the preload to be applied. In such cases the assessment can be based on foundation capacities and stiffnesses calculated using soil strength parameters and partial material factor 𝛾𝛾𝑚𝑚 instead of the applied preload. In such cases the requirements of 9.3 should be supplemented by the guidance and criteria for applicability in E.4. . No further reproduction or distribution permitted. Printed / viewed by: 53 The forces imposed on the foundation due to environmental actions are time-varying and random in nature. The response to the horizontal, vertical and rotational forces on the spudcan and the embedded portion of the leg is non-linear and hysteretic. The non-linearity of the foundation response can have a major effect on the response of the structure. Two types of structural response analyses use a range of foundation models and are carried out as described in 10.4.4. These foundation models can include major simplifications and the limitations of the models should be understood by the assessor. The foundation behaviour under the action of combined forces is appropriately described by a theoretical yield surface in the vertical reaction, horizontal reaction and moment reaction (VHM) space. Foundation safety assessment is achieved by comparing the imposed forces with the yield surface. However, for structural response analysis, the foundation can be modelled as pinned or with a degree of foundation fixity. Foundation fixity is the rotational restraint offered by the soil supporting the spudcan and shall only be used in a model that also includes finite vertical and horizontal foundation stiffnesses. The degree of fixity is dependent on the soil type, the maximum vertical spudcan reaction during installation, the foundation stress history, the structural stiffness of the jack-up, the geometry of the spudcan, the spudcan translational and rotational displacements, and the simultaneous vertical and horizontal actions. The structural response analysis shall be carried out using one of the following foundation models, which have increasing levels of complexity:  pinned model: simple pinned foundation for all legs;  secant model: linear vertical, linear horizontal and secant rotational stiffness where the iterative reduction of rotational stiffness ensures conformity with the yield interaction surface;  yield interaction model: non-linear vertical, horizontal and rotational stiffness model where the non-linear behaviour ensures conformity with the yield interaction surface;  continuum model: non-linear continuum foundation model coupled to the structure; this model shall also account for the load-penetration behaviour beyond the penetration achieved by preloading. The assessment procedures for each of these models are described in 9.3.6. 9.3.2 Leg penetration during preloading The methods for calculating ultimate vertical bearing capacity of a foundation in various types of soil are discussed in A.9.3.2. The gross bearing capacity formulae adopted are based on the assumption that penetration in sand is a drained process, and penetration in clay is an undrained process. Cases that deviate from this assumption shall be assessed using appropriate methods. Uncertainties regarding the geotechnical data should be properly reflected in the interpretation and reporting of the analyses. For the special case of carbonate material, see 9.4.10 and A.9.4.10. The predicted spudcan penetration is obtained from the bearing capacity versus spudcan penetration curve at the specified preload. Soil backfill directly above the spudcan, composed of backflow and infill, shall be included when computing the penetration. The use of predicted leg penetrations during jack-up deployment provides essential information on the compatibility between theoretical assessment and operational reality. Where there is significant deviation, the validity of the site-assessment should be re-evaluated. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 54 © ISO 2023 – All right reserved 9.3.3 Yield interaction The yield interaction surface is used to describe the limiting combinations of vertical, horizontal and moment loading that the soil at a given penetration depth can sustain without becoming fully plastic. When the yield surface is transgressed, plastic deformation occurs and the spudcan reactions are redistributed. During preloading, a significant volume of soil below the spudcan is made to plastically deform as the spudcan penetrates, thus generally expanding its yield surface and increasing its capacity. During removal of the preload, the soil unloads elastically and the foundation response is stiffer than during preload penetration. Provided the jack-up's preload capacity is appropriate for a site's environmental conditions, the soil behaves in an essentially elastic manner for most combinations of vertical, horizontal and moment loading that the spudcan experiences while on site. Inelastic response occurs when the combination of vertical, horizontal and moment loading approaches the yield surface; this is likely only for a few, if any, loading cycles during an extreme storm. Degradation can take the form of a softened foundation and/or additional displacement (vertical, horizontal, and/or rotational). The yield surface can be described by the formulae given in A.9.3.3 for a range of soil types and embedments. The weight of all soil backflow and infill on top of the spudcan shall be included in the spudcan vertical reaction to be assessed against the yield surface. For the case of layered soils, additional analysis should be performed to determine the appropriate yield surface. 9.3.4 Foundation stiffnesses Foundation analysis under time-varying loading requires knowledge of the load-deflection behaviour of the soil. This is usually described by spring stiffnesses in the vertical, horizontal and rotational modes. Initial stiffnesses, as described in A.9.3.4.1, can be estimated from the solutions for a rigid circular plate on an elastic half-space using the small strain shear moduli for clay (see A.9.3.4.3) or sand (see A.9.3.4.4) and Poisson's ratio; alternatively, a continuum model can be used. The soil shear modulus is dependent on strain level; therefore, suitable adjustments should be made for cyclic and dynamic loading. The reduction in stiffness as the spudcan reactions approach or exceed the yield surface shall be included in the analysis. There are different approaches to determining the softening of the stiffnesses. Where the reduction of stiffness is not included in the soil model, the provisions of A.9.3.4.2.2 should be used to determine the reduced rotational secant stiffness; the vertical and horizontal stiffness remain unchanged. The stiffness reduction is implicit in fully coupled yield interaction models and in non-linear continuum foundation models, as discussed in A.9.3.4.2.3 and A.9.3.4.2.4, respectively. When the foundation is comprised of layered soils, additional analysis should be used to determine the effective stiffnesses. The effects of soil-leg interaction for deep penetrations can be included. Guidance is given in A.9.3.4.6. 9.3.5 Vertical-horizontal foundation capacity envelopes When the foundation is represented with the pinned or secant models, the spudcan reactions shall be assessed using the vertical-horizontal capacity envelopes. For the secant model, this assessment shall be performed after achieving conformity with the yield interaction surface. Spudcan reactions resulting from responses based on a model with pinned foundations for all legs may be assessed using the simplified preload and windward leg checks, provided that the individual spudcan reactions satisfy the associated applicability requirements. . No further reproduction or distribution permitted. Printed / viewed by: 55 The envelopes should be developed using the applicable subclause of A.9.3.5. The weight of all soil backfill that occurs during preloading shall be included in the spudcan vertical reaction when evaluating the capacity envelopes. Backfill after preloading shall be considered when its effect is to increase the foundation utilizations. 9.3.6 Acceptance checks The overall jack-up foundation stability shall be assessed for the forces FH and FV, and the moment FM, acting on each spudcan due to the assessment loading case Fd, using Levels 1, 2 or 3, as listed below (in order of increasing complexity and reducing conservatism); see Figure A.9.3-17. If a lower level check fails to meet the foundation acceptance criteria given in A.9.3.6, a higher level check can be performed. The partial factors for the checks required by this subclause are given in Annex B. a) Level 1: Preload and windward leg check with reactions from a response analysis based on a pinned spudcan model for all legs; Steps 1a and 1b shall both be completed for a Level 1 check:  Step 1a: Foundation capacity check of the leeward leg based on the preloading capability (A.9.3.6.2), and  Step 1b: Check of the windward leg (A.9.3.6.3). b) Level 2: Foundation capacity checks. One of the following three steps shall be completed for a Level 2 check:  Step 2a: Foundation capacity check and sliding resistance check (A.9.3.6.4), based on the vertical and horizontal reactions, assuming a pinned spudcan; or  Step 2b: Foundation capacity check and sliding resistance check (A.9.3.6.5), based on the vertical, horizontal and moment reactions from a spudcan model that includes rotational, vertical and horizontal foundation stiffness with rotational stiffness reduction; or  Step 2c: Foundation capacity check (A.9.3.6.5), based on the vertical, horizontal and moment reactions from a spudcan model that includes rotational, vertical and horizontal foundation stiffness with reduction of vertical, horizontal and rotational stiffnesses. A Level 3 displacement check shall be performed. c) Level 3: Displacement check (A.9.3.6.6). One of the following two steps shall be completed for a Level 3 check:  Step 3a: Simple check using the leg-penetration curve based on the results of a Level 2 check when the foundation capacity check fails and/or a check of the effects of windward leg sliding when the Level 2 sliding check fails; or  Step 3b: Numerical analysis of the complete jack-up and non-linear foundation coupled in vertical, horizontal and rotational degrees of freedom, e.g. finite element approach. The maximum vertical reaction is expected to occur on the leeward leg. Likewise, the minimum vertical reaction is expected on the windward leg. In Step 1a, the preload check of the leeward leg is based on the assumption that the net ultimate vertical bearing capacity is equal to the maximum spudcan reaction during preloading. Care shall be taken to account for the submerged weight of any backfill, WBF,A that occurs after the maximum preload has been applied. Typically backflow and infill after preloading, WBF,A is uncertain; for this reason, it should conservatively be included on the leeward leg but not on the windward leg. The check of the windward leg shall be performed to ensure that the sliding resistance is adequate under minimum vertical reaction conditions. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 56 © ISO 2023 – All right reserved In Step 2a, the combined vertical and horizontal forces on the spudcan shall be checked against the factored vertical-horizontal foundation capacity and the factored sliding capacity of all legs. The vertical bearing capacity of the foundation is a function of the horizontal forces and moments. The sliding capacity of the foundation is a function of the vertical forces and moments. However, the moments are ignored in Step 2a analyses as the spudcans are considered to be pinned. For Step 2b, the combined vertical and horizontal forces on the spudcan shall be checked against the factored vertical-horizontal foundation capacity envelope and the factored sliding capacity of all legs. The reactions are determined for a spudcan with "fixity" conditions whereby the interaction of moment with vertical and horizontal reactions is implicitly included through the use of the yield function. For Step 2c, the foundation capacity and sliding checks are performed implicitly through the use of an unfactored yield function as described in A.9.3.3. When a Step 2a or 2b assessment results in calculated factored combined vertical and horizontal forces on the spudcan that lie outside the factored bearing capacity envelope, a Level 3 assessment shall be used to evaluate the associated displacements. For all Step 2c analyses, a Step 3a assessment shall be performed. The procedure shall account for the redistribution of forces resulting from the overload and displacement of the spudcan(s). The acceptability of structural utilizations, overturning utilizations, foundation utilizations and displacements shall be re-evaluated in accordance with the acceptance criteria in Clause 13. The resulting displacement of the jack-up shall neither lead to the possibility of contact with any adjacent structure nor exceed practical limitations for continued operations. Step 3a shall be accomplished by using the load-penetration curve to estimate the additional settlement for leeward legs. Sliding of windward legs shall be investigated. Additional settlement and sliding cause the magnitude and distribution of the foundation reactions to change. The effects on the structure shall be evaluated, including displacement dependent effects. If the effects are significant the procedure shall be iterated. Step 3b shall be performed using a structural model including non-linear response of soil and structure (large displacement effects). 9.4 Other considerations 9.4.1 Skirted spudcans Special consideration shall be given to the analysis of skirted spudcans including, but not limited to:  skirt penetration;  filling of any voids within skirt should partial penetration occur;  bearing capacity (which can exceed preload, see E.4);  settlement, including consolidation of trapped soils;  moment capacity;  sliding resistance;  foundation stiffness;  drainage paths;  resistance to extraction; . No further reproduction or distribution permitted. Printed / viewed by: 57  soil trapped within the skirt after extraction. 9.4.2 Hard sloping strata Problems associated with positioning of spudcans on a hard sloping stratum at or below the sea floor shall be carefully considered. In this respect, a hard stratum is a soil layer where only partial spudcan penetration is expected and can be either a surface or a buried feature. Where a spudcan partially penetrates into a hard sloping stratum, there is potential to generate eccentricity in the spudcan reaction, which should be taken into account. There is also increased potential for slippage on sloping or undulating strata. 9.4.3 Footprint considerations The depressions in the sea floor, or in harder layers within the seabed, that remain when a jack-up is removed from a site are referred to as footprints. The form of the depression depends on several factors such as the spudcan shape, the soil conditions, the spudcan penetration achieved and the method of extraction. The shape and the time period over which the depression exists can also be affected by the local sedimentary regime. The positioning of spudcans very close to, or partially overlapping, footprints shall be carefully considered. This is because of the difference in resistance between the original soil and the disturbed soil in the footprint area and/or the slope at the footprint perimeter. The resulting leg displacements and/or eccentric spudcan loading can cause damage to the jack-up. The situation can be complicated by the proximity of a fixed structure or wellhead. The interaction between a spudcan and a footprint is expected to be minimal when the edge-to-edge distance exceeds one spudcan diameter, see Stewart and Finnie (2001)[173], Cassidy et al. (2009)[48], Gaudin et al. (2007)[78] and Gan et al. (2008)[77]. 9.4.4 Leaning instability Leaning instability of jack-ups can occur during operations in soft clays where the rate of increase in bearing capacity with penetration is small, leading to uncontrollable leg penetration. The potential for and consequences of such instability shall be considered. 9.4.5 Leg extraction difficulties Prior to emplacement of the jack-up, consideration shall be given to potential leg extraction difficulties; see A.9.4.5. 9.4.6 Cyclic mobility, liquefaction and liquefaction-induced lateral flow Cyclic loading can cause a progressive build-up of pore pressures within the foundation soils and consequent soil strength degradation (cyclic mobility or liquefaction). The effects can be either over a large area or local to the soils under the spudcan. Earthquakes cause cyclic loading in the soil and can result in failure of the soil mass locally or over a large area. At a site with, or adjacent to, a sloping seabed, the potential for earthquake induced large-scale liquefaction-induced lateral flow that could affect the jack-up should be assessed; if present, the site should be rejected. Local foundation cyclic loading can be caused by the jack-up response to earthquakes, severe storms, rotating machinery, etc. Depending on the magnitude of pore pressures developed, cyclic loading can result in large vertical and lateral displacements of the spudcans, which can be differential in some cases. The assessment shall consider the effects of cyclic loading on the stability and displacements of foundations. Guidance is provided in A.9.4.6. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 58 © ISO 2023 – All right reserved 9.4.7 Scour When a spudcan is installed on the sea floor, its presence can cause increased local flow velocities (due to wave and current) that can result in the sea floor soils being eroded. The phenomenon of scour is observed around spudcans that are embedded in granular materials at sites with high sea floor flow velocities. If scour is recognized to potentially cause problems, then preventive measures shall be implemented. See A.9.4.7 for further guidance. 9.4.8 Spudcan interaction with adjacent infrastructure For jack-ups located in close proximity to pile-founded structures, soil displacements caused by the spudcan penetration can induce actions on the nearby piles. The magnitude of the soil displacement depends on the spudcan proximity (distance of the spudcan edge to the pile's outside surface), the spudcan diameter, penetration, and soil stratigraphy. If the proximity of the spudcan to the pile is greater than one spudcan diameter, then no significant lateral actions on the pile are expected in a homogeneous single-layer soil system. However, this is not necessarily true for a layered soil system. When the proximity is less than one spudcan diameter or layered soil conditions are encountered, then the assessor should report the possibility of induced actions on the pile(s). Guidance regarding the analytical procedures available for assessing these spudcan induced actions on piles, pipelines and other adjacent infrastructure is given in A.9.4.8. 9.4.9 Geohazards Natural, shallow geological features and conditions such as faults, scarps, fluid expulsion features and gas-charged or over-pressurized sediments can pose additional threats to jack-ups that are independent of the forces on the foundation. These geological hazards, collectively called geohazards, can result in unforeseen events such as submarine slides and uncontrolled fluid releases that can adversely affect jack-up performance and/or stability. These events can be triggered by natural phenomena such as earthquakes or by human activities such as drilling. Shallow geohazard risk assessments are performed routinely in the offshore industry to safeguard well and geotechnical drilling operations from subsurface hazards such as shallow gas. However, it is important that a pre-installation shallow hazard assessment for a jack-up consider the overall geological setting and all the geohazards that can threaten the jack-up or its operations while on site. This work should be conducted and assured by competent geohazard specialists. Further information is given in A.9.4.9. 9.4.10 Carbonate material Carbonate materials can exhibit unexpected behaviour and should be addressed with care (see A.9.3.2.5 and ISO 19901-4). 10 Structural response 10.1 Applicability The response of a jack-up is determined by applying actions in accordance with the assessment load case Fd (see 8.8) to the structural model to determine displacements, internal forces in components and reactions at the foundations. Responses shall be compared with resistances to determine the utilization of the jack-up structure and its foundation; acceptance criteria are given in Clause 13. This clause presents methods for calculating the response of a jack-up including static and dynamic effects. This clause also presents a discussion of the important parameters affecting the dynamic response, including mass, stiffness and damping. Actions are presented in Clause 7. Stiffness and mass modelling and the application of actions are addressed in Clause 8. Foundation modelling is addressed in Clause 9. . No further reproduction or distribution permitted. Printed / viewed by: 59 10.2 General considerations Action effects required for the assessment of jack-ups in the ULS typically include:  component forces that shall be checked to determine the adequacy of individual structural components;  foundation reactions that shall be checked to determine foundation performance and global stability;  displacements to check for interaction with adjacent structures. Action effects required for the assessment of jack-ups in the FLS, when applicable for long-term operations, typically include local cyclic stresses which shall be checked to assess fatigue damage (see Clause 11). 10.3 Types of analyses and associated methods A jack-up shall be assessed for the in-place elevated storm mode. Depending on the geographic location of the site, assessments for earthquake, ice and abnormal environmental events can be required. In unusual circumstances, assessments for fatigue resistance and accidental situations can be required. Different methods of analysis can be used for the various limit states to be considered. The methods of analysis for the in-place elevated storm mode include:  deterministic two-stage analysis, in which the responses of the jack-up are determined by analysing a single combination of actions for each assessment situation;  stochastic one-stage analysis in which extreme values of the responses of the jack-up are determined statistically by analysing multiple combinations of (environmental) actions for each assessment situation. Because of the inherent non-linearity of jack-ups, stochastic analyses are performed in the time domain;  ultimate strength analysis in which the collapse strength of the jack-up structure and its foundation are determined. Table 10.3-1 summarizes the analysis requirements for different assessment situations. The analyses shall consider the parameters discussed in 10.4. Table 10.3-1 — Analysis requirements for different assessment situations In-place elevated mode Deterministic analysis Stochastic analysis Ultimate strength analysis Linear Non-linear Dynamic linear Dynamic non-linear Ultimate and serviceability limit states (ULS and SLS) See 10.5, A.10.5.2 and A.10.5.3 Generally outside the scope of this document. See 10.10 Fatigue limit state (FLS) See 10.6 not applicable See 10.6 not applicable not applicable Accidental/Abnormal limit state (ALS) Appropriate, but can be unduly conservative Appropriate, but outside the scope of this document Appropriate, but can be conservative Appropriate, but outside the scope of this document Generally outside the scope of this document. However see 10.8 for ice Earthquake (ULS or ALS) See 10.7 and A.10.7 Appropriate, but outside the scope of this document Generally outside the scope of this document. See A.10.7.4 . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 60 © ISO 2023 – All right reserved 10.4 Common parameters 10.4.1 General A description of important parameters that are applicable to all analysis methods is given in 10.4. 10.4.2 Natural periods and related considerations 10.4.2.1 General The estimation of natural periods is critical for the determination of the structural responses because jack-ups can exhibit significant dynamic effects. As a result, the dynamic responses can differ markedly from the static responses. The assessment of responses shall consider the possible variation of the natural periods and its implication on the accuracy of the analyses. Determining the natural periods depends upon accurate estimates for  the water depth and hull elevation,  leg penetration and nature of the foundation, and  the magnitude and location of masses associated with actions due to fixed load and variable load. 10.4.2.2 Stiffness The overall stiffness of the jack-up shall be determined including the hull, legs, leg-to-hull connection, foundation and the P-Δ geometric effects as defined by the modelling practices in Clause 8. A range of stiffness values should be considered if stiffness information is not well defined. 10.4.2.3 Mass The mass model shall include contributions from structural, non-structural and added masses (see 8.7). For all analysis types, the most likely mass distribution should be considered, e.g. the position of the cantilever, the distribution of the variable load, and the level of marine growth. A range of values or distributions should be considered if mass information is not well defined or when the tolerances on the known position are significant. 10.4.2.4 Variability in natural period The variability in natural period shall be considered. There are several factors that can cause variability in natural periods including stiffness non-linearities in the structure and foundation. The natural periods of the jack-up are a function of the static and time-varying response due to non-linearities in the structural and foundation behaviour. Structural non-linearities can result from stiffness changes (gap impact, yielding, etc.). Foundation non-linearities can result from changes in stiffness as a function of the force level with respect to the yield surface and force reversal (hysteresis). For example, the variability in natural period should be taken into account when selecting the levels of fixity to use in the analysis as it can affect the influence of wave reinforcement and/or cancellation effects. NOTE The calculated natural periods can vary considerably between linear elastic and non-linear analyses. 10.4.2.5 Cancellation and reinforcement Cancellation is the situation where, due to the spacing between the jack-up legs with respect to the wave length, the wave action on the jack-up is close to zero over the complete wave cycle. The primary parameters for reinforcement and cancellation effects are the wave length and the leg spacing. First cancellation occurs when the crest and trough of the same wave cycle are at two legs (leg spacing one . No further reproduction or distribution permitted. Printed / viewed by: 61 half of the wave length). First reinforcement occurs when the crests of successive wave cycles are at the legs. Subsequent order period cancellations and reinforcements occur at progressively shorter periods. The wave period used in the deterministic extreme storm analysis shall be chosen with the range to minimize the effects of cancellation, see e.g. A.6.4.2.3. In a random wave dynamic analysis, wave action cancellation can significantly reduce the dynamic amplification. This effect should be minimized by adjusting the natural period of the jack-up to be away from the cancellation periods. 10.4.3 Damping Contributions to the system damping include foundation damping, hydrodynamic damping and structural damping. Non-linear behaviour of the foundation and the jacking system also contributes to system damping. The degree to which each of these contributions affects the system damping depends on the type of analysis and the level of system response. 10.4.4 Foundations The analysis of the structure and the assessment of the foundation can be performed essentially in two different ways.  Option 1: Deterministic two-stage approach. The first stage is to calculate the dynamic amplification factor and inertial loadset, often using linearized analyses. The foundation and structural assessment is then performed using a quasi-static iterative or elasto-plastic analysis technique, for which the dynamic actions are approximated by the pre-determined inertial loadset.  Option 2: Stochastic one-stage approach, where dynamic structural analysis and assessment is performed using one model. Here, a fully detailed non-linear time domain stochastic analysis is performed taking into account the elasto-plastic behaviour of the foundation. 10.4.5 Storm excitation Wind, current and waves all contribute to the storm excitation. The primary source of dynamic excitation is from the fluctuating nature of waves. As waves and currents interact, these two metocean factors should be considered in combination when generating time-varying hydrodynamic actions in accordance with Clauses 7 and A.7. Various mean wave directions shall be considered. The effect of wave spreading around the mean direction may be taken into account, provided reliable information is available. When using joint probability metocean data, relevant combinations of wind, waves and current shall be considered to determine the most onerous combination (see A.7.3.1.1). Sea states with a peak period close to the natural period of the jack-up can give larger dynamic amplification resulting in larger responses in lower sea states than the extreme storm event. Therefore, waves with peak periods close to the natural period of the jack-up should be considered (see A.6.4.2.9). 10.5 Storm analysis 10.5.1 General A jack-up responds dynamically to time-varying wave actions (see 10.4.5 and A.10.4.5). This behaviour shall be modelled appropriately in the analysis by including the static and dynamic contributions. These effects can be determined by a two-stage deterministic or by a one-stage stochastic analysis procedure. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 62 © ISO 2023 – All right reserved Static actions due to fixed loads, variable loads and wind actions shall be combined with the time-varying wave and current actions. A two-stage deterministic storm analysis involves developing static metocean actions and an inertial loadset. The inertial loadset can be developed from either a classical SDOF analogy or from a random dynamic analysis, in both cases through the development of a DAF (see 10.5.2). The inertial loadset shall be applied to be in phase with, and to increase the response to, the metocean actions as one of the loadcases. When the natural period divided by the apparent wave period is greater than 0,9, caution shall be exercised and additional loadcases for different inertial phases should be considered. A more detailed time domain stochastic storm analysis procedure, in which inertial actions are directly included, can also be used. This analysis predicts the combined static and dynamic response of the jack-up to random wave actions from which the most probable maximum extreme (MPME) responses are calculated; see 10.5.3. Action effects due to leg inclination shall be combined with action effects due to the extreme storm event to maximize leg and holding system strength utilizations. Table 10.5-1 summarizes the two approaches to incorporating foundation response (10.4.4) and dynamics in the analysis. 10.5.2 Two-stage deterministic storm analysis The most common method of analysis adopted for the determination of the extreme response is the deterministic, quasi-static wave analysis. This method does not reflect the random nature of wave excitation and assumes that the extreme responses are uniquely linked to the occurrence of a single and periodic extreme wave. Deterministic responses are normally calculated by time stepping the single and periodic extreme wave through the structure. The extreme responses are determined from the following:  the actions due to fixed loads, variable loads and wind actions;  the time-dependent, but quasi-static wave/current actions;  an inertial loadset representing dynamic effects. The actions of the first and second list items above shall be determined in accordance with Clause 7. . No further reproduction or distribution permitted. Printed / viewed by: 63 Table 10.5-1 — Methods of extreme storm analysis Parameter Two-stage deterministic storm analysis One-stage stochastic storm analysis Stage 1 Determine DAF Stage 2 Single deterministic storm analysis Multiple random time domain simulations KDAF,SDOF KDAF,RANDOM Wave/current actions not applicable Random (superposition of linear components) High order regular wave Random (linear or higher order) Dynamics Formula (A.10.5-1) (see A.10.5.2.2.2) Time domain simulations (see A.10.5.2.2.3) Inertial loadset determined by means of KDAF,SDOF or KDAF,RANDOM (see A.10.5.2) Time domain simulations (see A.10.5.3) Wind actions not applicable Ignore Quasi-static Quasi-static Foundation Linearized Linearized Non-linear Non-linear Structure Stiffness from non-linear structure Non-linear or calibrated to non-linear Non-linear Non-linear Output KDAF,SDOF KDAF,RANDOM (Global) responses (Global) responses The inertial actions induced by time-varying wave and current actions are approximately represented by an inertial loadset. The magnitude of the inertial loadset is determined from a DAF and the quasi-static wave/current actions. Methods of calculating the DAF include:  a classical single degree-of-freedom analogy;  determining the ratio of dynamic and quasi-static responses from random dynamic analyses. A.10.5.2.2.3 gives load cases that should be considered when KDAF, RANDOM is used to determine the inertial loadset in a two-stage analysis. The first load case that includes in-phase inertial load shall always be considered, e.g. as Formula (A.10.5-4). When (Tn/Tp) > 0,9, additional load cases considering out-of-phase inertial loads should be considered, e.g. the three shown in A.10.5.2.2.3, Formulae (A.10.5-5) to (A.10.5-7). When determining DAFs, P-Δ effects shall be included in both the quasi-static and the dynamic analyses and the contribution of the P-Δ effect to the overturning moment shall be included in the overturning moment. 10.5.3 Stochastic storm analysis In the stochastic method, one or more random dynamic analyses are performed for a given sea state or for a range of sea states. As the stochastic wave and current excitation varies with multiple realizations of a sea state, the extreme responses in each realization also vary. The most probable maximum extreme response can be determined through statistical analysis of one or more simulations. In each simulation, the actions due to fixed loads, variable load and wind actions are combined with the time-varying wave/current actions. The actions shall be determined in accordance with Clause 7. The influence of dynamic effects is inherently included in the results of the dynamic stochastic analyses. When undertaking a fully integrated dynamic stochastic analysis that directly results in a time history of structural and foundation utilizations, it is necessary to determine the MPME of each utilization. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 64 © ISO 2023 – All right reserved The action factors on metocean actions for this analysis method shall be set to 1,0 in accordance with 8.8.1.3. To obtain a consistent level of environmental actions the metocean parameters (i.e. wind velocity, wave height and current velocity) shall be factored; see A.10.5.3. NOTE The inclusion of action factors not equal to unity is complex and open to physical inconsistencies and misapplication. The more logical approach of applying partial factors to the metocean parameters has been adopted for fully integrated dynamic stochastic analyses. However, the partial factors on metocean parameters for stochastic analysis used for determining the DAF are set to unity. 10.5.4 Initial leg inclination The initial leg inclination resulting from guide clearances and from the permitted hull inclination results in additional leg moment. If the initial leg inclination is explicitly modelled, the additional moments are inherently included in the results. If the initial leg inclination is not explicitly modelled, the member forces and holding system forces from the analysis in accordance with 10.5.2 or 10.5.3 shall be increased to account for the effect of the additional leg moment prior to undertaking the structural strength checks; see A.10.5.4. In all cases, the direction of the moment shall be such as to maximize the utilization checks in the vicinity of the hull; this can be achieved simply by considering the base of the legs to be offset in the up-wind direction. 10.5.5 Limit state checks Limit state checks shall be performed for:  strength of leg members, particularly in the vicinity of the upper and lower guides and adjacent to leg to spudcan connections;  strength of the holding system. Hull strength and jackhouse to deck connections are considered to be covered by classification unless special circumstances apply;  overturning stability and spudcan sliding;  spudcan strength and foundation bearing capacity. Checks shall be performed for a range of sea state directions to determine the maximum limit state utilizations. See also Clauses 9, 12 and 13. 10.6 Fatigue analysis A fatigue analysis is normally undertaken during the jack-up design phase. For jack-up operations of shorter duration than the RCS special survey period, fatigue analysis is not required provided that an RCS structural integrity regime, or equivalent, is in place. For jack-up operations of longer duration fatigue shall be considered, see Clause 11. 10.7 Earthquake analysis This subclause addresses analysis of a jack-up using exposure level L1 earthquake data, see 5.5.5. An earthquake assessment shall be performed for sites where the ISO 19901-2 seismic zone is 2 or above. It is not necessary to perform an earthquake assessment for seismic zone 0. For seismic zone 1, an earthquake assessment should be considered when any of the following conditions applies:  sites with the potential for cyclic mobility (e.g. liquefaction) (ISO 19901-2 site class F); . No further reproduction or distribution permitted. Printed / viewed by: 65  sites with the potential for unacceptable additional leg penetrations if the preload reactions are exceeded (settlement limits can be reduced when operating adjacent to other structures);  jack-ups where the ratio between the individual leg preload reaction at the spudcan and the maximum still water operating reaction at the spudcan is less than 1,25. For the relevant zone 1 or higher zones the structure may be assessed using an ELE screening assessment to ULS criteria. The ELE screening earthquake actions shall be derived from the uniform hazard spectrum for a return period of 1 000 years. Guidance on 1 000 year earthquake response spectrum criteria can be found in ISO 19901-2. In this kind of earthquake, the jack-up should sustain little or no damage. If the jack-up does not satisfy this 1 000 year ELE screening to ULS assessment criteria or the ELE screening assessment has not been performed, the alternative assessment methods (see 10.10) in combination with ISO 19901-2 shall be used to evaluate conformity with the earthquake performance requirements. In this case, the jack-up is acceptable if the assessment demonstrates that structural failures causing loss of life and/or major environmental damage do not occur under any of the earthquake events considered although, in some cases, considerable structural damage can be sustained. NOTE 1 The dynamic effects of the soil column are not specifically addressed in the screening assessment, however they are included implicitly in the response spectra amplification coefficients. In the alternative assessment approach, the non-linear soil behaviour and its effect on the soil dynamics can be included in the Site Response Analysis or a more detailed soil representation. The effect of the earthquake on the cantilever hold-down and other critical parts of the jack-up shall be considered. Earthquake actions shall include accelerations due to the fundamental modes of vibration as well as higher frequency modes associated with the legs above and below the hull, and significant drilling facilities. In addition, the local actions from soil movement on the spudcans and the legs should be considered, where relevant. The associated inertial actions on all significant masses shall be taken into account. Partial action factors for earthquake assessments are given in 8.8.1.1 and 8.8.1.4. Since it is not possible to ready the jack-up for an earthquake, it is important to consider reasonable mass and operating configurations. For earthquake assessments, the spudcan internal entrapped mass shall be included in the mass model and the spudcan added mass (surrounding water and/or soil) shall be included where significant. NOTE 2 A low mass tends to lead to a shorter natural period and, hence, greater amplification. A higher mass results in a longer period but can be associated with greater lateral forces depending on the reduction in the transverse accelerations in combination with the increased mass. The assessment model shall include a realistic range of spudcan-soil modelling that encompasses the uncertainties in foundation stiffness and capacities. For earthquake excitation, foundation fixity tends to increase the inertial response and shall be considered - a pinned spudcan model, in general, produces an unconservative representation of the earthquake demand on the jack-up. Where the penetration predictions vary significantly, the range shall be considered. Spudcan settlement resulting from earthquake excitation shall be considered. Differential settlements can have the most serious consequences. At sites where cohesionless soil conditions dominate, the possibility of earthquake-induced soil cyclic mobility shall be considered (see 9.4.6). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 66 © ISO 2023 – All right reserved 10.8 Ice 10.8.1 General Jack-ups operating in arctic and cold regions shall conform with the relevant clauses of this document and ISO 19906, as appropriate. Arctic and cold regions are taken to be those areas that can be affected by sea ice, icebergs and icing conditions. When the annual probability of ice interaction with jack-up is less than 10-4, then ice actions need not be assessed. When 10-4 < (annual probability of ice interaction with jack-up) < 10-2 an ALS ice-assessment shall be undertaken (see 10.8.3). When the annual probability of ice interaction with jack-up is greater than 10-2, ULS and ALS ice-assessments shall be undertaken (see 10.8.2 and 10.8.3). The annual probability of ice interaction can be demonstrated to be reduced through analysis and use of ice management, removal (moving off) and seasonality (see 19906:2019, 8.2.7, ISO 35104). See A.10.8.1.1 for examples of different operating area types. 10.8.2 ULS When undertaking ULS ice assessments in extreme assessment situations, see 5.3 a):  The extreme level wind, wave and current return period shall be taken from this document.  The extreme wind, wave and current action factor shall be taken from this document.  The gravity action factors shall be taken from this document.  The extreme level ice probability of exceedance shall be taken from ISO 19906:2019, 7.2.2.3.  The extreme level ice action factors shall be taken from ISO 19906:2019, Table 7-3.  In the absence of a joint probability analysis, combination factors shall be taken from ISO 19906:2019, Table 7-2. 10.8.3 ALS When undertaking ALS ice assessments in abnormal assessment situations:  The abnormal level wind, wave and current probability of exceedance shall be taken from ISO 19906.  The abnormal level wind, wave and current action factor shall be taken from ISO 19906.  The gravity action factors shall be taken from this document.  The abnormal level ice probability of exceedance shall be taken from ISO 19906:2019, 7.2.2.4.  The abnormal level ice action factor shall be taken from ISO 19906:2019, Table 7-3.  In the absence of a joint probability analysis, combination factors shall be taken from ISO 19906:2019, Table 7-2. . No further reproduction or distribution permitted. Printed / viewed by: 67 10.8.4 Assessments in the area types A.10.8.4 gives examples of the assessment used in the different area types. 10.8.5 Additional factors for arctic and cold regions The assessment of operations in arctic and cold regions shall account for factors additional to those addressed for other regions. See A.10.8.5. 10.9 Accidental situations Accidental situations are not normally addressed as part of an assessment unless specifically required by the jack-up owner, operator or regulator (see also 5.3). 10.10 Alternative analysis methods 10.10.1 Ultimate strength analysis An ultimate strength analysis is intended to identify the collapse strength of the jack-up structure and foundation under applied actions. For occupied situations, the acceptance criteria are typically set by the regulator. For unoccupied/occupied-evacuated situations, the acceptance criteria shall be agreed between the operator and the jack-up owner. In some areas of the world, the analysis can entail:  assessing the jack-up for abnormal wave condition to demonstrate survivability (e.g. for a 10 000 year return period in the North Sea);  scaling the extreme storm actions until failure is predicted to occur, to meet a target reserve strength ratio (e.g. Gulf of Mexico fixed structures; see ISO 19902:2020, 9.10.2);  performing time-history analyses for the ALE (see ISO 19901-2);  performing ice ALS analyses. The uncertainties associated with foundation capacity can be significantly greater than those associated with the ultimate strength of the structure. In performing ultimate strength analyses, it is therefore important to make this distinction and to evaluate both structural and foundation failure modes. Therefore, the following strategy is recommended. a) Structural or foundation failure should be identified using an analysis based on mean (or best estimates) of structural steel properties and soil properties. b) Where foundation failure occurs before structural failure, structural failure should be determined assuming a foundation fixity based on upper bound or, if necessary, artificially strong, estimates of soil properties. The foundation displacement due to the foundation failure should be appropriately modelled. This should provide an assessment of the steel structure strength. Ultimate strength evaluation is used to estimate the most likely collapse strength of a structure with partial resistance factors set to 1,0. Due to the absence of partial resistance factors, an ultimate strength evaluation shall be interpreted and used with care. 10.10.2 Methodology Methodology for performing an ultimate strength analysis can be found in ISO 19902. The determination of actions and foundation properties shall be in accordance with this document. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 68 © ISO 2023 – All right reserved 11 Long-term applications 11.1 Applicability When a jack-up is to be operated at one particular site for longer than the special survey period, the site-specific assessment shall be supplemented by the provisions of Clause 11 and the requirements of the RCS classing the jack-up. There can be additional specific requirements of the jack-up owner, operator and regulator related to the long-term application. 11.2 Assessment data In addition to the data normally required for short-term assessment, further data associated with long-term use are required. These data shall include:  the duration for which the jack-up is intended to be on site;  a list of modifications to the jack-up, which affect the time-varying actions, structural resistance or fatigue endurance of structural components;  the limitations on the ability to re-level the hull and maintain hull elevation, e.g. in connection with supported conductors;  the deviations from the standard operating and elevated storm mode configurations given in the marine operations manual;  the metocean data suitable for fatigue assessment, including directionality of wind, waves and current;  the expected accumulation and vertical distribution of marine growth and relevant mitigation procedures;  the geotechnical data required for the assessment of long-term operations;  other data required for fatigue assessment (see 11.3.1). 11.3 Special requirements 11.3.1 Fatigue assessment The remaining fatigue life of all relevant structural components shall be shown to be adequate for the planned period on site. In the assessment, any fatigue damage contributions from the jack-up's prior service shall be taken into account; historical jack-up and site data shall be requested from the jack-up owner. In view of the inherent uncertainty of fatigue life assessments, a margin of safety shall be applied through a fatigue damage design factor (fFD). See A.11.3.1 for further details. The partial action factors used for fatigue analysis can be reduced to unity when using S-N curves at mean minus two standard deviations of log(N). 11.3.2 Weight control Changes in weight during the long-term operations shall be monitored to ensure conformity with the assessment assumptions. A sufficient allowance for weight growth shall be included in the assessment. . No further reproduction or distribution permitted. Printed / viewed by: 69 11.3.3 Corrosion protection Adequate corrosion protection shall be implemented to cover the entire duration on site. Special attention shall be given to corrosion protection in the splash zone. 11.3.4 Marine growth The assessment shall include the effects of the long-term accumulation of marine growth. 11.3.5 Foundations The assessment shall include consideration of the potential for and effects of  settlement under extreme storm actions,  long-term foundation settlement,  seabed subsidence, e.g. due to reservoir depletion,  scour, and  seabed mobility. 11.4 Survey requirements Surveys are required to ensure that the integrity of the jack-up is maintained during the long-term application. As a minimum, the jack-up owner shall develop a plan that includes the following surveys: a) a special survey prior to deployment on site; b) project specific surveys in accordance with an in-service inspection programme (PSIIP). The PSIIP required for long-term operations shall be developed based on:  RCS requirements;  the jack-up's prior operating and inspection history;  the assessment results for the expected operations. Sea floor surveys shall be included in the PSIIP for sites where scour and/or seabed mobility are known to occur. If changes to the initially planned duration are proposed by the operator, the jack-up owner should document that the jack-up has sufficient remaining fatigue life, and approval is obtained from the RCS and regulator. 12 Structural strength 12.1 Applicability 12.1.1 General This clause provides the basis for the determination of the structural strength of truss type legs. Limited guidance is given for other leg types. The strength of the fixation system and/or the elevating system and the strength of the spudcan are normally provided by the manufacturer. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 70 © ISO 2023 – All right reserved Formulae for the required strength checks are given in this clause, which result in structural strength utilizations in accordance with Clause 13. A suitable method for carrying out the required calculations is given in A.12. The resistance factors given in Annex B are specifically tied to the calculation methods presented in A.12 and shall be re-calibrated if other methods are used. RCS requirements cover the design, construction, and periodic survey of the jack-up and address issues, such as material properties, fabrication tolerances, welding, construction details and parts of the jack-up other than the legs (e.g. jackhouse and hull structure), which are not normally addressed in a site-specific assessment. For example, when the forces within the fixation system are within the limits set by the manufacturer and are approved by the RCS, no additional assessment is required of the hull and jackhouse. Similarly, if the foundation's vertical and rotational reactions on the spudcan are within the structural limits set by the manufacturer, it is not necessary to check the strength of the leg to spudcan connection. In this clause, and the corresponding A.12, values for strength, capacity, properties, modulus and geometry are representative values unless indicated otherwise. 12.1.2 Truss type legs The requirements set out in Clause 12 relate to chords and braces of truss type legs. Weld sizes, gusset plates, the strength of joints, etc., are covered by RCS requirements, and should not control the overall structural integrity. Chords and braces are covered in 12.2 to 12.6. 12.1.3 Other leg types Some of the checks included in Clause 12 are applicable to either tubular or box-type legs, but for these configurations, Clause 12 should be supplemented with other documents to address stiffened sections, e.g. American Petroleum Institute references API Bulletin 2U (2004)[16] and API Bulletin 2V (2004)[17] or DNV-RP-C202 (DNV 2021b)[58] and DNV-CG-0128 (DNV 2021a)[57]. 12.1.4 Fixation system and/or elevating system The factored representative ultimate strength shall be used for the strength assessment. The strength of the fixation system and/or the elevating system is normally supplied by the manufacturer. The manufacturer's data is not necessarily the unfactored representative ultimate strength of the system(s) but can be a working stress limit value. Data can be given separately for the vertical and horizontal directions. If no representative ultimate strength data are given, or cannot be inferred, then representative ultimate strengths shall be determined through rational analysis. NOTE An example of a rational approach to determining the ultimate strength is to multiply the allowable rated capacity by 1,15. 12.1.5 Spudcan strength including connection to the leg The factored representative ultimate strength of the spudcan and the spudcan to leg connection shall be used for the strength assessment. The strength of the spudcan and the spudcan to leg connection is normally supplied by the manufacturer for all applicable vertical and horizontal forces, and for moments about the horizontal axes. The manufacturer's data are not necessarily the unfactored representative ultimate strengths but can be working stress limit values. If no representative ultimate strength data are given, or cannot be inferred, then representative ultimate strengths shall be determined through rational analysis. NOTE An example of a rational approach to determining the ultimate strength is to multiply the allowable rated capacity by 1,15. . No further reproduction or distribution permitted. Printed / viewed by: 71 12.1.6 Overview of the assessment procedure The basic approach consists of the determination of  classification of member cross-sections (see 12.2),  section properties of non-circular prismatic members (see 12.3),  Euler amplification of member forces (if not included within the structural analysis) (see 12.4),  strength of lattice leg members [tubular members (see 12.5), and prismatic members in truss type legs (see 12.6)], and  strength of joints (see 12.7). 12.2 Classification of member cross-sections 12.2.1 Member types The methodology used to classify member cross-sections is different for circular cross-sections of tubular members and for all other cross-sections of prismatic members. Longitudinally reinforced tubulars and tubulars with pin-holes, cut-outs, etc., shall be considered to be non-circular prismatic members. 12.2.2 Material yield strength The material yield strength used in the member classification and the calculation of member strengths shall correspond to the value at 0,2 % strain offset from the initial linear stress-strain behaviour. A lesser value shall be used when the material does not exhibit sufficient work-hardening. 12.2.3 Classification definitions The strength of a steel cross-section is affected by its potential to suffer local buckling when subjected to compression due to a bending moment or an axial force, or a combination thereof. By classifying cross-sections, the requirement to explicitly calculate local buckling strength is avoided. For non-circular prismatic members, the components and cross-sections are classified as plastic, compact, non-compact (or semi-compact) and slender, in order of decreasing strength. When a cross-section is composed of components of different classes, it shall be classified in accordance with the class of its component(s) with the lowest strength in compression. Slender components within a cross-section can be ignored, provided that only the remaining cross-section is used for all aspects of the assessment. The following classification shall be applied.  Class 1 Plastic: Cross-sections with plastic hinge rotation capacity. Conformity with this classification enables a plastic hinge to develop with sufficient rotation capacity to allow redistribution of moments to occur within the member. All plastic sections are inherently compact.  Class 2 Compact: Cross-sections with plastic moment capacity. Conformity with this classification enables the full plastic moment capacity of a cross-section to be developed, but local buckling prevents the development of a plastic hinge with sufficient rotation capacity to permit plastic assessment.  Class 3 Non-compact (or semi-compact): Cross-sections with between full yield moment capacity and plastic moment capacity. Conformity with this classification enables the yield stress to be realized at the extreme compression fibre, but elasto-plastic local buckling prevents development of the full plastic moment capacity. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 72 © ISO 2023 – All right reserved  Class 4 Slender: Cross-sections that buckle locally before the yield stress can be achieved. A cross-section is classified as slender if any of the compression components of the cross-section does not conform with the limits for non-compact components. There is no requirement to classify tubular member cross-sections to the same extent as non-circular prismatic member cross-sections other than to identify those tubulars for which plastic hinge rotation capacity is possible (i.e. class 1). This is because the formulae for tubular member cross-sections presented in A.12.5 account for local buckling, whether plastic or elastic. 12.3 Section properties of non-circular prismatic members 12.3.1 General The requirements in 12.3 apply to rolled and welded non-circular prismatic members comprising one or more components, such as can be found in a chord section of a jack-up leg. Their cross-sectional properties shall be determined as described in 12.3. Cross-sectional properties of tubular members are included within the determination of their strength and addressed in 12.5. 12.3.2 Plastic and compact sections For class 1 plastic and class 2 compact sections, section properties can be determined assuming fully plastic properties. Where elastic section properties are determined for class 1 and 2 sections instead of plastic section properties, these can be based on a fully effective cross-section and shall then be treated as for class 3 sections. 12.3.3 Semi-compact sections Section properties for class 3 semi-compact sections shall be based on elastic properties assuming fully effective cross-sections. When considering a cross-section comprised of components having different yield strengths, the critical stress locations shall be evaluated as these do not necessarily coincide with the minimum section modulus or the principal axes. The strength check is based on an interpolation between class 2 plastic capacity and class 3 elastic capacity. NOTE The critical stress locations are typically at the edges of the components and are a function of the member forces, the yield strength of the component and its position within the cross-section of the member. 12.3.4 Slender sections Cross-section properties for class 4 slender sections shall be determined using elastic principles. When the stress across the entire section is tensile, the full section may be used. If any part of the section is in compression, the sectional properties shall be reduced as required based on effective sections (see A.12.3.5). 12.3.5 Cross-section properties for the assessment The nomenclature and selection of variables for use in the assessment of members are summarized in A.12.3.5. . No further reproduction or distribution permitted. Printed / viewed by: 73 12.4 Effects of axial force on bending moment The moment resulting from the eccentricity between the elastic and plastic centroids of class 1, 2 and 3 sections shall be included in the assessment moment; this can occur in sections that include components of differing yield strengths. Similarly, for class 4 sections, there is an eccentricity between the full elastic centroid that is used in the structural response analysis and the centroid of the reduced section that is used in the member strength check. This moment correction shall be included for members in both tension and compression. Euler moment amplification, or p-δ effects, shall be included for members in axial compression. When p-δ effects are not included in the structural response analysis, they shall be included in the strength checks. The effective length factors (K)and moment reduction factors (Cmr) for use in strength checks are listed in Table A.12.4-1. Alternatively, they can be determined using a rational analysis that includes joint flexibility and side-sway. It is mentioned that, traditionally, the effects of Euler amplification are included in the strength checks. However, some analysis results implicitly include the effects of Euler amplification. The assessment should include the effects of both the global large displacement effects (P-Δ) and the local member moment amplification (p-δ). Large displacement effects (P-Δ) are addressed in Clause 8. 12.5 Strength of tubular members The strength of tubular members shall be checked for combined axial forces and bending, and for shear and torsional shear. The partial factors for the checks required by this subclause are given in Annex B. The requirements given in 12.5 ignore the effects of hydrostatic pressure. The validity of this assumption shall be checked for all sealed tubular sections (see e.g. Table A.12.5-1). 12.6 Strength of non-circular prismatic members The strength of non-circular prismatic members shall be checked for combined axial forces and bending, and for shear and torsional shear. The partial factors for the checks required by this subclause are given in Annex B. The requirements given in 12.6 ignore the effects of hydrostatic pressure. The validity of this assumption shall be checked for all sealed non-circular prismatic members (see e.g. Figure A.12.6-1 and Table A.12.5-1). 12.7 Assessment of joints Joint strength is normally addressed by the RCS for the metocean conditions given in the operations manual. If the assessor has concerns that the site conditions lead to joint loads that exceed those assessed by the RCS, joint strength shall be assessed. 13 Acceptance criteria 13.1 Applicability 13.1.1 General This clause defines the criteria for checking the acceptability of a jack-up for operation at a specific site for the various limit states. The partial action and resistance factors set out in the acceptance criteria have been developed in conjunction with the analysis methodology set out in the rest of this document and are valid only if used . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 74 © ISO 2023 – All right reserved with this methodology. The factors do not necessarily provide adequate reliability if used with other methodologies. The criteria for checking the acceptability of a jack-up include consideration of the following issues:  structural strength of legs, spudcan, and holding system (see 13.3, 13.4, and 13.5, respectively);  hull elevation (see 13.6);  leg length reserve (see 13.7);  overturning stability (see 13.8);  foundation integrity including preload, foundation capacity, sliding displacement, settlement resulting from exceedance of the capacity envelope (see 13.9);  interaction with adjacent infrastructure (see 13.10);  temperature (see 13.11). The assessment checks for structural strength, overturning stability and foundation integrity for each limit state and assessment situation are based on a utilization parameter as described in 13.2. 13.1.2 Ultimate limit states The assessment of the ultimate limit states (ULS) shall ensure that the acceptance criteria are not exceeded in any of the applicable assessment situations; see 5.1, 5.3 and 5.4. The integrity of the foundation is central to the site-specific assessment of a jack-up. Areas on jack-ups that are often critical with regard to structural strength are the legs at the lower guides, the legs between guides, the pinions and/or rack teeth, the fixation system and/or fixation system supports (if fixation system is fitted) and the leg to spudcan connection. Where there is a degree of foundation fixity, the lower parts of the leg shall be checked assuming an upper bound fixity value. Foundation fixity may be included in the evaluation of the upper leg when justified by an applicable and detailed foundation study. Conformity in whole or in part can also be demonstrated through comparison with prior assessments conducted in accordance with the provisions of this document. 13.1.3 Serviceability and accidental limit states Serviceability limit states and accidental limit states are discussed in 5.3. 13.1.4 Fatigue limit states For jack-up operations with a duration less than the RCS special survey period, a fatigue analysis is not required, provided that structural integrity is maintained through an appropriate programme of inspection. For long-term applications, fatigue shall be considered in accordance with Clause 11. NOTE The special survey period is normally between five years and eight years. 13.2 General formulation of the assessment check The assessment shall follow a partial safety factor format. The partial action factors shall be applied to actions, not the action effects. The partial resistance factors shall be applied to representative foundation capacities and structural strengths. When undertaking a stochastic time domain procedure . No further reproduction or distribution permitted. Printed / viewed by: 75 that incorporates fully non-linear foundation responses, the MPME utilizations shall be calculated using the procedure set out in 10.5.3. The utilization for each limit state and assessment situation shall satisfy the requirement of Formula (13.2-1): U ≤ 1,0 (13.2-1) where U is the utilization to one significant decimal place. For assessments where the relevant action effect can be expressed by a single response, U is of the general form given in Formula (13-2-2): 𝑈𝑈=𝐴𝐴𝐹𝐹d𝑅𝑅 (13.2-2) where 𝐴𝐴𝐹𝐹d is the action effect due to factored actions 𝑅𝑅 is the factored resistance For members and foundations subjected to combined forces, the internal force pattern and the resistances combine into a single interaction formula, e.g. combined axial and bending, see A.12.5.3.2 and A.12.6.3. If the interaction formula governing the assessment check is, or can be, reduced to an inequality of the form U ≤ 1,0, then the utilization is equal to U. For assessments where the resistance is given by the yield interaction surface (for foundations) or the plastic interaction surface (for strength of non-circular prismatic members) the utilization is of the general form given in Formula (13-2-3): 𝑈𝑈=𝐿𝐿1𝐿𝐿2 (13-2-3) where L1 is the length of the vector from a specified origin to the factored action effect L2 is the length of the vector from the origin specified for L1 to the factored interaction surface Factored actions shall be determined in accordance with the assessment load case Fd in 8.8. Action effects shall be determined in accordance with the requirements of Clauses 9, 10 and 12. Associated guidance is given in A.9, A.10 and A.12. The particular form of the utilization formula is determined by the foundation and strength checks formulated in these clauses. Annex B summarizes the clause(s)/subclauses(s) in this document where the applicable calculation methodology and the associated assessment check(s) can be found, and lists the values of the partial action and resistance factors that shall be used. NOTE Normally, both partial action and partial resistance factors are greater than unity: actions are multiplied by partial action factors and resistances are divided by partial resistance factors. 13.3 Leg strength assessment Formulae (13.2-2) or (13.2-3), as applicable, shall be used to assess the utilization of the leg structure. The methodology for undertaking checks on the strength of members is described in Clause 12, together with the associated resistance factors. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 76 © ISO 2023 – All right reserved 13.4 Holding system strength assessment The forces on the holding system due to factored actions, for any of the applicable assessment situations, shall be checked against the factored representative value of ultimate strength. A partial resistance factor for holding system strength of γR,H = 1,15 shall be used. 13.5 Spudcan strength assessment The forces on the top and bottom of the spudcan due to factored actions, for any of the applicable assessment situations, shall be checked against the factored representative value of ultimate strength. A partial resistance factor for spudcan strength of γR,S = 1,15 shall be used. Care should be taken when using calculated foundation capacities (e.g. see E.4.9) because the forces can be higher than used in the manufacturer’s design case. NOTE 1 This check addresses issues such as: spudcan overburden (at maximum penetration); spudcan strength (over the range of predicted penetration); and eccentric spudcan support (e.g. due to foundation fixity, sloping seabed or existing spudcan footprints). NOTE 2 The spudcan strength checks are unlikely to be critical unless the assessment vertical seabed reaction exceeds the maximum design preload reaction. 13.6 Hull elevation assessment A hull elevation resulting in at least 1,5 m clearance between the assessment return period extreme wave crest elevation and the underside of the hull shall be provided (see 6.4). The extreme wave crest elevation is normally determined from the extreme still water level (SWL) in A.6.4.4 and the wave crest elevation above SWL in A.6.4.2.4. In some areas of the world an abnormal wave crest elevation (see A.6.4.2.4) that can affect the global response, can be greater than the extreme wave crest elevation plus 1,5 m. The hull elevation shall be sufficient to clear this abnormal wave crest elevation. Where appropriate metocean databases and reliability models exist, the abnormal wave crest elevation can be determined accounting for the joint probability of tide, surge and crest elevation. The hull elevation shall account for any settlement due to the extreme or abnormal storm event. NOTE 1 Metocean studies after hurricanes Katrina and Rita have suggested that there exist local wave crest enhancements with a small area of effect, (Forristall, 2007)[71]. When calculating the hull elevation for jack-ups, it is not necessary to consider these local effects over and above the abnormal crest elevation since they do not affect the jack-up globally. NOTE 2 The air gap is defined in ISO 19900 as the clearance between the highest water surface that occurs during the extreme metocean conditions and the lowest exposed part not designed to withstand wave impingement. This differs from the definition historically used by the jack-up industry. 13.7 Leg length reserve assessment The leg length reserve above the upper guides should account for the uncertainty in the prediction of leg penetration and account for any settlement. The leg length reserve shall be at least 1,5 m. The greater the uncertainty, the larger the leg length reserve that should be available. A larger reserve can also be required due to the following:  strength limitations of the top bay;  the increase in the proportion of the leg bending moment carried by the holding system due to the effective reduction in leg stiffness at the upper guide;  additional settlement due to scour; . No further reproduction or distribution permitted. Printed / viewed by: 77  long-term foundation settlement;  reservoir settlement. 13.8 Overturning stability assessment Formula (13.2-2) shall be used to assess margin of safety against overturning of the jack-up. The utilization shall be calculated as the ratio of overturning moment due to the factored actions, MOTM, and the factored stabilizing moment, Rd,OTM. The overturning moment, MOTM, shall be calculated about the overturning axis in the most critical assessment situation using the assessment load case Fd. For independent-leg jack-ups, the overturning axes shall pass through any two or more spudcan reaction points. The reaction points are described in 8.6.2 and A.8.6.2. The factored representative value of the stabilizing moment Rd,OTM shall be calculated by Formula (13.8-1): 𝑅𝑅d,OTM = 𝑅𝑅r,OTM/𝛾𝛾R,OTM (13.8-1) where Rr,OTM is the representative value of the stabilizing moment; γR,OTM is the partial resistance factor for stabilizing moment, γR,OTM = 1,05. The representative value of the stabilizing moment, Rr,OTM, shall be calculated for the same assessment situation and about the same axis as used for the calculation of the overturning moment and shall account for the following contributions:  large deflection (P-Δ) effects shall be included when computing the overturning utilization;  the minimum stabilizing moment from the most onerous combination of minimum variable load and position of centre of gravity in accordance with 5.3, 5.4.4, 7.4 (see also A.7.4);  the stabilizing moments provided by a degree of foundation fixity; any stabilizing moments from foundation fixity shall be calculated in accordance with Clause 9, taking account of any reduction of the moment fixity to conform with the yield surface of the foundation. Large deflection (P-Δ) effects can be included in one of three ways. a) A reduced stabilizing moment can be calculated from the fixed action with the jack-up at the displaced position resulting from the factored actions. b) An increased overturning moment can be calculated incorporating the additional overturning of the hull at a displaced condition. c) The overturning moment can be calculated from the foundation reactions obtained from a large deflection analysis, so the reduction in stabilizing moment due to large deflection effects is implicitly included within the overturning moment. NOTE The overturning check serves only the purpose of a traditional benchmark; the assessment is governed by the foundation checks. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 78 © ISO 2023 – All right reserved 13.9 Foundation integrity assessment 13.9.1 Foundation capacity check Formulae (13.2-2) or (13.2-3) as applicable shall be used to assess the foundation. The spudcan reactions due to factored actions shall be checked against the factored capacity in accordance with the requirements of 9.3.6 (see also A.9.3.6). For a Level 1 foundation integrity check, the preload utilization, US,pl, shall be computed and reported (see e.g. A.9.3.6.2). The utilization shall satisfy Formula (13.9-1) or the alternative formulation of Formula (13.9-2): stBF,AS,plLoR,PRE10,/VWUVγ+=≤ (13.9-1) or VBF,oSS,plLoR,PRE10,/FWBUVγ−+=≤ (13.9-2) where the symbols are as defined in 4.1 and γR,PRE shall be taken as 1,1. For a Step 2a check with pinned spudcans, the utilization of the vertical and horizontal foundation capacity, US,vhm, shall be determined (see e.g. A.9.3.6.4.1) and shall satisfy Formula (13.9-3): 𝑈𝑈S,vhm=𝐿𝐿𝑏𝑏1𝐿𝐿𝑏𝑏2≤1,0 (13.9-3) where Lb1 is the length of the vector from origin used for establishing the bearing utilization (FH, FV)ORG to the environmental response point (determined from the factored actions) (FH, FV) (see e.g. A.9.3.6.4.1). Lb2 is the length of the vector from origin used for establishing the bearing utilization (FH, FV)ORG and passing through (FH, FV) to the factored vertical-horizontal capacity surface QVH,f (see e.g. A.9.3.6.4.1). For a Step 2a check, the utilization of the foundation resistance to sliding, US,pl, shall be computed (see e.g. A.9.3.6.4.2) and shall satisfy Formula (13.9-4): 𝑈𝑈S,vhm=𝐿𝐿𝑠𝑠1𝐿𝐿𝑠𝑠2≤1,0 (13.9-4) where Ls1 is the length of the vector from origin used for establishing the sliding utilization (FH, FV)ORG to the environmental response point (determined from the factored actions) (FH, FV) (see e.g. A.9.3.6.4.2). . No further reproduction or distribution permitted. Printed / viewed by: 79 Ls2 is the length of the vector from origin used for establishing the sliding utilization (FH, FV)ORG and passing through (FH, FV) to the factored vertical-horizontal capacity surface QVH,f (see e.g. A.9.3.6.4.2). For a Step 2b check with a degree of foundation fixity, the conditions of Formulae (13.9-3) and (13.9-4) remain valid; (see e.g. A.9.3.6.5). In a Step 2c check, using a yield interaction or continuum foundation model, conformity with the foundation yield surface is inherently included and the above utilization checks are generally not performed. However, when sliding is not included in the model, a sliding check shall be undertaken (see e.g. A.9.3.6.4.2) and Formula (13.9-4). 13.10 Displacement check If the forces on any spudcan due to the assessment load case Fd result in a utilization computed in accordance with 13.9.1 that exceeds 1,0, a further assessment may be performed as discussed in A.9.3.6.6. This assessment shall show that any additional settlements and/or the associated additional structural action effects are within acceptable limits. Furthermore, there shall be no operational limitations on levelling the hull and re-establishing a safe hull elevation, or alternatively safely departing the site. NOTE A conservative estimate of the allowable settlement can be derived from the hull inclination limit if this is specified in the operations manual. 13.11 Interaction with adjacent infrastructure The displacement of the jack-up shall not:  lead to contact or adverse interaction with any adjacent structure;  exceed practical limitations for continued operations. 13.12 Temperatures The 50 year lowest mean daily average air and water temperatures shall be in conformity with the limits given in the operating manual. NOTE The purpose of this check is to ensure that the field temperature is compatible with the material used in the jack-up construction. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 80 © ISO 2023 – All right reserved Annex A (informative) Additional information and guidance NOTE The clauses/subclauses in this annex provide additional information and guidance on clauses/subclauses in the body of this document. The same numbering system and heading titles have been used for ease in identifying the subclause in the body of this document to which it relates. A.1 Guidance on scope Although this document does not address the integrity of well conductors, the Institute for Petroleum Guidelines (2001)[106] provide guidance on their assessment. A.2 Guidance on normative references No guidance is offered. A.3 Guidance on terms and definitions No guidance is offered. A.4 Guidance on symbols A.4.1 Symbols used in A.1 No guidance is offered. A.4.2 Symbols used in A.2 No guidance is offered. A.4.3 Symbols used in A.3 No guidance is offered. A.4.4 Symbols used in A.4 No guidance is offered. A.4.5 Symbols used in A.5 No guidance is offered. A.4.6 Symbols used in A.6 See 4.1.2 A.4.7 Symbols used in A.7 See 4.1.3 . No further reproduction or distribution permitted. Printed / viewed by: 81 A.4.8 Symbols used in A.8 See 4.1.4 A.4.9 Symbols used in A.9 See 4.1.5 A.4.10 Symbols used in A.10 See 4.1.6 A.4.11 Symbols used in A.11 See 4.1.7 A.4.12 Symbols used in A.12 See 4.1.8 A.5 Guidance on overall considerations No guidance is offered. A.6 Guidance on data assembled for each site A.6.1 Scope No guidance is offered. A.6.2 Jack-up data No guidance is offered. A.6.3 Site data No guidance is offered. A.6.4 Metocean data A.6.4.1 General The jack-up should be assessed for the extreme storm event (ULS assessment). For occupied jack-ups (category S1), the 50 year return period independent extremes should be used. Alternatively, 100 year joint probability metocean data may be used. The action factors for these two alternatives differ. If the jack-up life safety category is occupied-evacuated, it is assumed that reliable forecasting of the extreme storm event is feasible, that evacuation plans are established and documented, and that time and resources are available to safely evacuate all personnel from the jack-up and any adjacent structures that can be affected by failure of the jack-up (see 5.5). Under these conditions, hindcast storm characteristics may be computed based on the threshold time horizon of storm formation relative to the jack-up site. The time horizon is defined as the time required for safe evacuation, and the extreme storm event is derived from the population of storms that can develop and impact the jack-up site within that time horizon. A sudden hurricane is one that forms locally and, due to speed of formation and proximity to infrastructure at time of formation, might not allow sufficient time to evacuate occupied facilities within . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 82 © ISO 2023 – All right reserved the time required by the emergency evacuation plan. The population of storms used to derive the sudden hurricane at a given site can therefore be defined in terms of the time horizon required to evacuate the site. For occupied-evacuated jack-ups utilized in these circumstances, consideration should be given to the use of a 50 year return period “sudden hurricane”. An unoccupied jack-up may also be assessed using these criteria. Partial factors for each of these options are presented in 5.5.2. Site-specific data, if available, should be used for the assessment as regional data do generally not take account of local variations. Where the actions due to metocean conditions at the site are directional, the jack-up may be aligned on an advantageous heading subject to practical and infrastructure limitations at the site. A.6.4.2 Waves A.6.4.2.1 General The extreme wave environment should be determined in accordance with A.6.4.2.2 to A.6.4.2.10. It should be based on the three hour storm exposure for the relevant assessment return period (e.g. 50 year independent extremes or 100 year joint probability). The seasonally adjusted wave height may be used when appropriate for the proposed operation. When a fatigue analysis is required (see Clause 11), long-term wave data should be obtained. The assessor should check the consistency of the wave data provided, giving particular attention to the wave periods and the ratio of Hmax to Hsrp and query any apparent inconsistencies with the data provider. A.6.4.2.2 Extreme wave height The wave height information for a specific site can be expressed in terms of Hmax, the individual extreme wave height for the assessment return period, or the significant wave height Hsrp. The relationship between Hsrp and Hmax should be determined accounting for the duration of a storm (three hours minimum) and for the additional probability of other return period storms; see ISO/TR 19905-2:2012, 6.4.2.2. This relationship depends on the regional and site-specific conditions however, in the absence of site-specific information, Hsrp may usually be determined from Hmax using the generally accepted relationship for non-cyclonic areas as given in Formula (A.6.4-1): Hmax = 1,86 Hsrp (A.6.4-1) Similarly for cyclonic areas, in the absence of site-specific data, the recommended relationship is as given in Formula (A.6.4-2): Hmax = 1,75 Hsrp (A.6.4-2) The wave action can be computed deterministically (through an individual maximum wave approach) or probabilistically (through a time domain simulation). The two methods are discussed in A.6.4.2.3 and in A.6.4.2.5 to A.6.4.2.8, respectively (see also ISO/TR 19905-2:2012, 6.4.2). The two methods should be used in conjunction with the associated kinematics modelling recommended in A.7.3. A.6.4.2.3 Deterministic waves For the calculation of wave actions using a deterministic (regular) wave, it is appropriate to apply a kinematics reduction factor to the horizontal and vertical velocities and accelerations in order to obtain realistic estimates of the actions for the extreme storm event. This factor ensures that both the . No further reproduction or distribution permitted. Printed / viewed by: 83 deterministic (regular) calculation of wave action using a regular wave and the three-hour stochastic simulation produce statistically comparable results (i.e. both target the MPME response in the 50 year extreme storm event). In addition, the factor takes some account of wave spreading and the conservatism of regular wave kinematics. The kinematics reduction factor can be applied by scaling of wave kinematics. Use of wave height reduction is not appropriate and should not be used. The kinematics reduction factor, κ, to be applied to the kinematics obtained from Hmax can be determined from Formula (A.6.4-3): κ = φ (A.6.4-3) where φ is the directional spreading factor in accordance with ISO 19901-1:2015, A.8.3.2.2, for the site-specific metocean data or for open water conditions; it is based on the latitude Ψ in degrees and the type of storm or region: for low latitude monsoons with typically |Ψ| < 15° φ = 0,88 for tropical cyclones below approximately 40° latitude φ = 0,87 for extratropical storms for the range of latitudes 36° < | Ψ | < 72° φ = 1,019 3 − 0,002 08 | Ψ |. Alternatively, Formulae (A.6.4-4) to (A.6.4-7) can be used; see Hoyle et al. (2009)[101]: 𝜅𝜅=0,824𝜙𝜙+0,426𝜙𝜙2−0,043􀵬𝑆𝑆y𝐿𝐿w􀵰𝜙𝜙−1,450􀵬𝑆𝑆y𝐿𝐿w􀵰2𝜙𝜙−0,800􀵬𝑑𝑑w𝐿𝐿w􀵰𝜙𝜙+⋯ …+0,658􀵬𝑑𝑑w𝐿𝐿w􀵰2−0,640􀵬𝐻𝐻max𝑑𝑑w􀵰+1,303􀵬𝐻𝐻max𝑑𝑑w􀵰2𝜙𝜙2 (A.6.4-4) and subject to the following: 0,08≤􁉀𝑆𝑆𝑦𝑦𝐿𝐿𝑤𝑤􁉁≤0,43 (A.6.4-5) 0,14≤􁉀𝑑𝑑w𝐿𝐿𝑤𝑤􁉁≤0,76 (A.6.4-6) 0,07≤􁉀𝐻𝐻𝑚𝑚𝑚𝑚𝑚𝑚𝑑𝑑w􁉁≤0,58 (A.6.4-7) where Sy is the smallest spacing between the legs of 3-legged jack-ups; dw is the water depth; Hmax is the maximum wave height; Tass is the intrinsic wave period associated with Hmax; Lw is the wave length of the wave with Hmax and Tass in water depth dw, according to the periodic wave theory that is being used. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 84 © ISO 2023 – All right reserved The limiting values 𝑆𝑆𝑦𝑦𝐿𝐿w=0,43, 𝑑𝑑w𝐿𝐿w=0,76 and 𝐻𝐻max𝑑𝑑w=0,07 may be applied for calculation of κ in Formula (A.6.4-4) in case these bounds are transgressed. In all cases, it is not necessary that κ be greater than φ. The kinematics reduction factor formulation was developed for 3-legged drag-dominated jack-ups. Caution should be exercised if it is applied to other cases. The formulae should not be applied for the low wave conditions that dominate in FLS assessment; such cases are likely to be outside the limits of applicability, where κ = φ can be applied. In lieu of using the kinematics reduction factor, the effects of wave spreading can be explicitly included in the analysis method, provided that higher frequency interaction effects (e.g. those due to frequency sum terms) are appropriately modelled through the use of second (or higher) order wave theory. Frequency interaction effects introduce additional actions that offset some of the reduction in actions predicted by three-dimensional linear wave theories. See A.7.3.3.3.2. The wave actions should be determined using an appropriate wave kinematics model in accordance with A.7.3.3.1. In the analysis, a single value for the intrinsic wave period Tass, expressed in seconds, associated with the maximum wave can be used. The “intrinsic” period of the wave as seen by an observer moving with the current should be used in the derivation of wave kinematics required for action calculations; guidance is given in ISO 19901-1:2015, 8.3. Unless site-specific information indicates otherwise, Tass is normally between the limits as given in Formula (A.6.4-8): 3,44􀶧􀵫𝐻𝐻srp􀵯 < 𝑇𝑇ass < 4,42􀶧􀵫𝐻𝐻srp􀵯 (A.6.4-8) where Hsrp is the return period of the extreme significant wave height, expressed in metres. A.6.4.2.4 Wave crest elevation The wave crest elevation used to determine the minimum hull elevation above the extreme still water level in A.6.4.4 can be obtained from the extreme wave height, Hmax in A.6.4.2.2, and the appropriate deterministic wave theory in A.7.3.3.3.1. A reasonably foreseeable extreme return period should be used for this calculation, and should be no shorter than 50 years, even if a lower return period is used for other purposes (e.g. the ULS assessment in tropical storm areas). For some regions, the abnormal wave crest elevation should be calculated based on storm statistics and according to principles described in ISO 19901-1:2015, A.8.7. Examples for the regional application of these principles can be found in Leggett et al (2007)[125], or for general application in DNV-RP-C205 (DNV 2021d)[60]. If a wave height reduction factor is used in a deterministic wave analysis to account for wave spreading and the conservatism of deterministic (regular) wave kinematics (see A.6.4.2.3), it should not be applied in the calculation of the wave crest elevation. A.6.4.2.5 Wave spectrum Where the analysis method requires the use of spectral data, the choice of the analytical wave spectrum and associated spectral parameters should reflect the width and shape of the spectra for the site and the significant wave height under consideration. In cases where the fetch and duration of extreme winds are sufficiently long, a fully developed sea results (this is rarely realized except, for example, in areas subject to monsoons). Such conditions can be represented by a Pierson-Moskowitz spectrum. Where . No further reproduction or distribution permitted. Printed / viewed by: 85 the fetch or duration of extreme winds is limited, or in shallow water depths, a JONSWAP spectrum can normally be applied (see A.6.4.2.7). Further discussions of wave spectra and spectral density functions for the Pierson-Moskowitz, SPM(ω), and the JONSWAP, SJS(ω), wave spectra are presented in ISO 19901-1:2015, A.8.3.1.2. The wave spectral density functions expressed as a function of wave frequency, i.e. Sηη(f), can be found in ISO/TR 19905-2:2012, 6.4.2.5. A.6.4.2.6 Airy wave height correction for stochastic analysis When Airy wave theory is used for stochastic (random) wave action calculations, see A.7.3.3.3.2, then it is necessary to account for wave asymmetry, which is not included in Airy wave theory. The significant wave height should be increased to capture the largest wave actions at the maximum crest amplitude. The increased significant wave height, Hs, should be determined as a function of the water depth, dw, expressed in metres, as given in Formula (A.6.4-9): 𝐻𝐻s= 􀵣1+􀵫10𝐻𝐻srp / 𝑇𝑇p,i2􀵯e(−𝑑𝑑w/25)􀵧𝐻𝐻srp (A.6.4-9) where dw is the still, or undisturbed, water depth (positive); Hsrp is the return period extreme significant wave height, expressed in metres; Tp,i is the intrinsic modal or peak period of the wave spectrum, and should be used with the wave kinematics model described in A.7.3.3.3.2. A.6.4.2.7 Peak and mean zero-upcrossing periods When undertaking a stochastic analysis (either for a one-stage analysis or for determining a DAF for a two-stage analysis), it is necessary to either consider a range of wave periods or a suitable wave spectrum that contains sufficient breadth of the peak to capture the dynamic characteristics. Information on the range of periods to use is given in this sub-clause, however, to avoid the requirement for dynamic analyses with several different wave periods, a practical alternative is to use a two-parameter spectrum, such as Pierson-Moskowitz with γ = 1,0, in combination with the site-specific most probable peak period. When using the relationships in Table A.6.4-1, the value of γ used should be as given by the data provider. For a given significant wave height, the wave period depends on the significant wave steepness which in extreme seas in deep water often lies within the range 1/20 to 1/16. This leads to the expression for intrinsic mean zero-upcrossing period Tz,i, related to Hsrp in metres, given in Formula (A.6.4-10): 3,2􀶧􀵫𝐻𝐻srp􀵯 < 𝑇𝑇z,i < 3,6􀶧􀵫𝐻𝐻srp􀵯 (A.6.4-10) However, in shallow water the wave steepness can increase to 1/12 or more, leading to an intrinsic mean zero-upcrossing period Tz,i as low as 2,8􀶧􀵫𝐻𝐻srp􀵯. This is because in shallow water the wave height increases and wave length decreases for a given Tz,i. When considering a JONSWAP spectrum, the peak enhancement factor γ varies between 1 and 7 with a most probable average value between 2,0 and 3,3. There is no firm relationship between γ, Hs and Tp,i. Relationships between variables for different γ according to Carter (1982)[40] are given in Table A.6.4-1. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 86 © ISO 2023 – All right reserved Table A.6.4-1 — Relationship between γ, Tz,i and Tp,i γ Tp,i/Tz,i 1 1,406 2 1,339 3 1,295 3,3 1,286 4 1,260 5 1,241 6 1,221 7 1,205 Unless site-specific information indicates otherwise values of γ between 2,0 and 3,3 can be used, selecting the value that produces the largest DAF. If a JONSWAP spectrum is applied, the response analysis should consider a range of periods associated with Hsrp based on the most probable value of Tp,i plus or minus one standard deviation. However, it should be ensured that the assumptions made in deriving the spectral period parameters are consistent with the values used in the analysis. Alternatively, applicable combinations of wave height and period can be obtained from a scatter diagram determined from site-specific measurements; in this case, specialist advice should be obtained on a suitable spectral form for the site. For other spectrums the assessor is referred to DNV-RP-C205 (DNV 2021d) for guidance. A.6.4.2.8 Short-crested stochastic waves For calculations of stochastic (random) wave actions, the short-crestedness of waves (i.e. the angular distribution of wave energy about the dominant direction) may be taken into account when site-specific information indicates that such effects are applicable. In all cases the potential for increased response due to short-crested waves should be investigated. The effect may be included by means of a directionality function F(αw), given in Formula (A.6.4-11): 𝑆𝑆ηη(𝑓𝑓,𝛼𝛼)=𝑆𝑆ηη(𝑓𝑓)𝐹𝐹(𝛼𝛼w) (A.6.4-11) where αw is the angle between the direction of elementary wave trains and the dominant direction of the short-crested waves; Sηη(f,αw) is the directional short-crested power density spectrum; 𝐹𝐹(𝛼𝛼w) is the directionality function. Directionality functions for extreme and fatigue analyses can be found in ISO 19901-1:2015, A.8.3.2.1, and ISO/TR 19905-2:2012, 6.4.2.8. When referring to the formulations in ISO 19901-1:2015, A.8.3.2.1, swell sea parameter ranges should be used for extreme analysis and wind sea parameter ranges for fatigue analysis. NOTE If using the approach in ISO 19901-1:2015, A.8.3.2.1, then the directional spreading function D1 with n = 8 gives good agreement with the formulation in ISO/TR 19905-2:2012, 6.4.2.8. For directional spreading function D2 with s = 15 and for directional spreading function D3 with σ = 0,34 there is good agreement with the formulation in ISO/TR 19905-2:2012, 6.4.2.8. . No further reproduction or distribution permitted. Printed / viewed by: 87 The modelling of short-crested stochastic waves should not be combined with the wave kinematics factor used in deterministic wave analysis to represent wave spreading and the conservatism of deterministic (regular) wave kinematics; see A.6.4.2.3. A.6.4.2.9 Maximizing the wave/current response Where the natural period of the jack-up is such that it can respond dynamically to waves; see A.10.4.1, the maximum dynamic response can be caused by waves or sea states with periods outside the ranges given in A.6.4.2.3 and A.6.4.2.7. Such conditions should also be investigated to ensure that the maximum (dynamic plus quasi-static) response is determined by considering sea states with different combinations of significant wave height and spectral period, or deterministic waves with different combinations of individual wave height and period. Such combinations may be limited to probabilities of exceedance that are equal to or lower than the intended probability level of the assessment. A.6.4.2.10 Long-term wave data For fatigue calculations (see 11.3.1), the long-term wave climate is required. For fatigue analysis, the long-term data present the probability of occurrence for each sea state, characterized by wave energy spectra and the associated physical parameters. This can be presented in the form of a significant wave height versus mean zero-upcrossing period scatter diagram or as a table of representative sea states. A.6.4.3 Current Current components should be applied in the downwind direction. The extreme wind-driven surface current velocity should be that associated with the assessment return period wind. When directional information regarding other current velocity components is available, the downwind component of the maximum surface flow of the mean spring tidal current and the assessment return period surge current should be added to the wind-driven surface current as indicated below. When appropriate, the currents can be seasonally adjusted. If directional data are not available, the components should be summed algebraically and assumed to be omnidirectional. A site-specific study should normally define the current velocity components. The current profile can be defined by a series of velocities at a range of elevations from sea floor to water surface. Unless site-specific data indicates otherwise, and in the absence of other residual currents (such as circulation, eddy currents, slope currents, internal waves, inertial currents, etc.), an appropriate method for computing current profile (see Figure A.6.4-1) is as given in Formulae (A.6.4-12) and (A.6.4-13): VC = (Vt + Vs)[(dw+z)/dw]1/7+ Vw [(href + z)/href] for |z| ≤ href (A.6.4-12) VC = (Vt + Vs)[(dw+z)/dw]1/7 for |z| > href (A.6.4-13) where VC is the current velocity as a function of z; NOTE A reduction can be applicable according to A.7.3.3.4. dw is the water depth Vt is the downwind component of mean spring tidal current; Vs is the downwind component of associated surge current (excluding wind-driven component); . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 88 © ISO 2023 – All right reserved Vw is the wind generated surface current; in the absence of other data, this may conservatively be taken as 2,6 % of the 1 min sustained wind speed at 10 m; href is the reference depth for wind-driven current, in the absence of other data, href should be taken as 10 m; z is the vertical coordinate relative to the SWL under consideration, positive upwards (always negative in the water column). Alternative formulations are provided in ISO 19901-1:2015, A.9.3. Comparisons of combined current and wave actions in ISO/TR 19905-2:2012, 6.4.3, show that the constant current profile is on the conservative side compared to the power law formulations presented in ISO 19901-1. Key dw water depth href reference depth for wind-driven current Vs downwind component of surge current Vt downwind component of tidal current Vw wind-driven surface current z vertical coordinate relative to the SWL under consideration, positive upwards (always negative in the water column) Figure A.6.4-1 — Suggested current profile, adapted from DNV-RP-C104 (DNV 2022b) In the presence of waves the current profile should be stretched/compressed such that the surface component remains constant. This can be achieved by substituting the elevation as described in A.7.3.3.3.2. Alternative methods can be suitable, however mass continuity methods are not recommended. The current profile can be changed by wave breaking. In such cases the wind-induced current could be more uniform with depth. For a fatigue analysis, current can normally be neglected. . No further reproduction or distribution permitted. Printed / viewed by: 89 A.6.4.4 Water depths The mean sea level (MSL) is used as the refence level for wind speed and marine growth. The SWLs used for the assessment of the site should be determined and related to LAT. The relationship between LAT and CD is discussed in ISO/TR 19905-2:2012, 6.4.4.  Different extreme water levels are required for the ULS assessment and hull elevation determination.  Unless reliable joint probability data are available, the extreme SWL, expressed as a height above LAT can be taken as follows: mean high water spring tidal level+ relevant return period extreme storm surge.  When lower water levels are more onerous for action calculations, the minimum SWL expressed as a height above LAT should be taken as follows: mean low water spring tidal level + relevant return period negative storm surge.  When determining the SWL for air gap calculations (safe hull elevation), a reasonably foreseeable extreme return period should be used. This should be no shorter than 50 years, even if a lower return period is used for other purposes (e.g. the ULS assessment in tropical storm areas). A.6.4.5 Marine growth Site-specific data should be obtained. In the absence of such data, default values for thickness and distribution are given in A.7.3.2.5. A.6.4.6 Wind A.6.4.6.1 General The wind velocity used for the assessment return period should be the 1 min sustained wind speed, related to a reference level of 10 m above MSL. The wind velocity profile may be defined by a logarithmic function in accordance with ISO 19901-1, or approximated by a power law (see A.6.4.6.2). A comparison of wind actions shows that the power law profile is slightly more severe than the ISO 19901-1 logarithmic profile, see ISO/TR 19905-2:2012, 6.4.6.1. Typically, the average difference is in the range of 7 % for a 1 min average wind speed of 20 m/s at 10 m above sea level, and 2 % for a 1 min average wind speed of 40 m/s. Different jack-up configurations (weight, centre of gravity, cantilever position, etc.) may be specified for operating and elevated storm modes. In such cases, the maximum wind velocity considered for the operating mode should not exceed that permitted for the change to the elevated storm mode. Formulae for the calculation of wind actions are given in A.7.3.4. A.6.4.6.2 Wind profile An expression for the vertical profile of the mean wind speed in the form of a power law is given by Formulae (A.6.4-14) and (A.6.4-15): 𝑉𝑉𝑍𝑍=𝑉𝑉ref(𝑍𝑍/𝑍𝑍ref)1/𝑁𝑁W for Z ≥ Zref (A.6.4-14) refZVV= for Z < Zref (A.6.4-15) . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 90 © ISO 2023 – All right reserved where Vz is the wind speed at elevation Z above the SWL under consideration; Vref is the 1 min sustained wind speed at elevation Zref (normally 10 m); Z is the elevation above the SWL; Zref is the reference elevation above the SWL; NW is the inverse exponent of the power law profile; NW = 10 unless site-specific data indicate that an alternative value of N is appropriate. Alternative profiles may be used when justified by the site-specific data. A.6.5 Geophysical and geotechnical data A.6.5.1 Geoscience data A.6.5.1.1 General Adequate geophysical and geotechnical information should be available to assess the suitability of the site and the foundation stability. The area covered should be sufficiently large to encompass any stand-off location; normally a 1 km × 1 km square is sufficient. For areas with regional geohazard issues, it is prudent to adopt a larger survey area to quantify the risk of potential geohazards, e.g. mud volcanoes, faults. Aspects that should be investigated are shown in Table A.6.5-1 and are discussed in more detail in the referenced subclauses. The information obtained from the surveys and investigations set out in A.6.5.1.2 to A.6.5.1.5 is required for areas where there is no adequate data available from previous operations. In areas where information is available, the recommendations set out herein may be considered using information obtained from other surveys or activities in the field. Detailed guidance on geophysical and geotechnical site investigations can also be found in ISO 19901-10 and ISO 19901-8, respectively. Experience of prior jack-up operations in the same field should be considered, particularly when the previous bearing pressures exceed those for the present operation by an adequate margin. A.6.5.1.2 Bathymetric survey An appropriate bathymetric survey should be supplied for an area approximately 1 km square centred on the proposed site. Line spacing of the survey should typically be not greater than 100 m × 250 m over the survey area. Interlining should be performed within an area 200 m × 200 m centred on the proposed site. Interlining should have spacing less than 25 m × 50 m. Such surveys are normally carried out using acoustic reflection systems (e.g. high-resolution multibeam echosounder). A.6.5.1.3 Sea floor survey The sea floor should be surveyed using sidescan sonar technique and should be of sufficient quality to identify obstructions and sea floor features and should cover the immediate area (normally a 1 km square) around the intended site. The slant range selection should give a minimum of 100 % overlap between adjacent lines. A magnetometer survey should also be undertaken if there are buried pipelines, cables and other metallic debris located on or slightly below the sea floor. Sufficient information should be obtained to enable safe positioning and removal of the jack-up. Sea floor obstructions, such as pipelines and wellheads, should be identified to sufficient depth to avoid the . No further reproduction or distribution permitted. Printed / viewed by: 91 potential for spudcan interference during both installation on and removal from site. In some cases, a visual inspection should be obtained in addition to the sea floor survey. Sea floor and debris surveys can become out-of-date, particularly in areas of construction/drilling activity or areas with mobile sediments. Close to existing installations sea floor surveys should, subject to practical considerations, be undertaken immediately prior to the arrival of the jack-up at the site. At sites with no existing surface or subsea infrastructure, the validity of existing sea floor surveys should be determined taking account of local conditions. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 92 © ISO 2023 – All right reserved Table A.6.5-1 — Foundation hazards, methods for identification and prevention/mitigation Risk Methods for identification and prevention/mitigation Subclause Installation problems Bathymetric survey Sea floor survey A.6.5.1.2 A.6.5.1.3 Punch-through Shallow seismic survey Soil sampling and other geotechnical testing and analysis Modify the spudcans (when punch-through failure is anticipated in advance) A.6.5.1.4 A.6.5.1.5, A.9.3.6 Settlement/bearing failure Shallow seismic survey Soil sampling and other geotechnical testing and analysis Ensure adequate jack-up preload capability A.6.5.1.4 A.6.5.1.5, A.9.3.6 A.9.3.6 Sliding failure Shallow seismic survey Soil sampling and other geotechnical testing and analysis Increase vertical spudcan reaction Modify the spudcans (when sliding failure is anticipated in advance) A.6.5.1.4 A.6.5.1.5, A.9.3.6 Scour and deposition Bathymetric and sea floor survey (identify sand waves) Surface soil samples and sea floor currents Inspect spudcan foundation regularly Install scour protection (gravel bag/artificial seaweed) when anticipated Modify the spudcans (when scour or deposition is anticipated in advance) A.6.5.1.2 A.6.5.1.3 A.9.4.7 Geohazards (liquefaction-induced lateral flow, mudslides, mud volcanoes etc) Sea floor survey Shallow seismic survey Soil sampling and other geotechnical testing and analysis A.6.5.1.3 A.6.5.1.4 A.6.5.1.5 Gas pockets/shallow gas Shallow seismic survey, complemented by pilot-hole drilling (where applicable) during subsequent geotechnical survey A.6.5.1.4 Faults Shallow seismic survey A.6.5.1.4 Metal or other object, sunken wreck, anchors, pipelines etc. Magnetometer and sea floor survey A.6.5.1.3 Local holes (depressions) in sea floor, reefs, pinnacle rocks, non-metallic structures (e.g. grout blanket) or wooden wreck Sea floor survey Visual inspection A.6.5.1.3 Leg extraction difficulties Soil sampling and other geotechnical testing and analysis Consider change in spudcans (when leg extraction difficulty is anticipated in advance) Jetting/Airlifting A.6.5.1.5, A.9.4.5 A.9.4.5 Eccentric spudcan reactions Bathymetry, sea floor & shallow seismic surveys Shallow seismic survey (buried channels or footprints) Soil sampling and other geotechnical testing and analysis Seabed modification A.6.5.1.2, A.6.5.1.3, A.6.5.1.4 A.6.5.1.4 A.6.5.1.5, A.9.4.2 Seabed slope Bathymetry, sea floor & shallow seismic survey Seabed modification A.6.5.1.2, A.6.5.1.3, A.6.5.1.4 A.9.4.2 Footprints of previous jack-ups Evaluate field records Prescribed installation procedures Consider filling/modification of holes as necessary A.6.5.1.1, A.6.5.1.2, A.6.5.1.3 A.9.4.3 A.9.4.3 . No further reproduction or distribution permitted. Printed / viewed by: 93 A.6.5.1.4 Shallow seismic survey A shallow seismic survey uses high resolution acoustic reflection techniques to  determine near surface soil stratigraphy, and  reveal the presence of shallow gas concentrations and other geohazards. NOTE Detection of gas pockets/shallow gas by means of shallow seismic survey alone involves large uncertainties, and shallow gas may not be detectable. In such cases, proportional mitigation measures should be considered, including possible additional detection equipment or drilling of a pilot-hole (see ISO 19901-8 and ISO 19901-10). Due to the qualitative nature of seismic surveys, it is not possible to conduct analytical foundation appraisals based on seismic data alone. The seismic data should be correlated with existing soil boring data in the vicinity and show similar stratigraphy. A shallow seismic survey should be performed over an approximately 1 km square area centred on the proposed site. Line spacing of the survey should typically be not greater than 100 m × 250 m over the survey area. The survey report should include at least two vertical cross-sections passing through the proposed site showing all the relevant reflectors and allied geological information. The equipment used should be capable of stratigraphic resolution to 0,5 m and thicker to a depth equal to the greater of 30 m or the anticipated spudcan penetration plus 1,5 times the spudcan diameter. A.6.5.1.5 Geotechnical investigation A.6.5.1.5.1 General Site-specific geotechnical investigation and testing are recommended in areas where any of the following apply:  relevant and appropriate geotechnical data are not available nearby;  the shallow seismic survey cannot be interpreted with any certainty;  significant layering of the strata is indicated;  the site is known to be potentially hazardous. A.6.5.1.5.2 Geotechnical investigation scope A geotechnical investigation should comprise a minimum of one borehole to a depth below the sea floor of 30 m or the anticipated spudcan penetration plus 1,5 times the spudcan diameter, whichever is the greater. All the layers should be adequately investigated and the transition zones cored at a sufficient sampling rate. The number of boreholes should account for the lateral variability of the soil conditions, regional experience and the geophysical investigation. When a single borehole is made, the borehole should be at the centre of the leg pattern. More detailed recommendations from the InSafeJIP (RPS Energy 2010) are presented in Annex D. Undisturbed soil sampling, in situ testing and laboratory testing should be conducted. Recognized in situ soil testing tools include piezocone penetrometer (CPT/CPTU), vane shear, T-bar and ball penetrometer tests (see ISO 19901-8). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 94 © ISO 2023 – All right reserved A.6.5.1.5.3 Geotechnical report The geotechnical information needed for spudcan emplacement and removal should include borehole logs, in situ test records and documentation of all laboratory tests, together with interpreted soil design parameters. An experienced geotechnical engineer should select design parameters suitable for spudcan foundation assessment. For analyses the geotechnical design parameters should include profiles of undrained shear strength and/or effective stress parameters, soil indices (water content, Atterberg limits, grain size, etc.), relative density, submerged unit weight, remoulded shear strength, soil sensitivity, coefficient of consolidation, and the over consolidation ratio (ROC). All laboratory tests should be performed on high quality samples. Additional geotechnical information should include cyclic or dynamic soil data that consider soil strength deterioration due to cyclic loading conditions including  soil stiffness,  shear modulus,  strain rate effects,  foundation damping from radiation effects and material hysteretic losses, and  shear wave velocities (for use in earthquake site response analysis). Soil information to evaluate spudcan extraction requires the remoulded or residual soil strength that takes account of the in situ soil strength reduction occurring during spudcan emplacement and the time on site. The design undrained shear strength utilized for bearing capacity analyses recommended in A.9.3 and A.9.4 are best established by combining results from:  laboratory tests on unconsolidated samples [e.g. unconsolidated undrained (UU) triaxial and miniature vane tests],  laboratory tests on consolidated samples (e.g. consolidated direct simple shear tests or consolidated triaxial test in compression or extension), and  in situ tests (e.g. cone penetrometer tests, ball or T-bar penetration tests, in situ vane tests). Consideration should be given to available site-specific jack-up installation experience when assessing the appropriate shear strength. In the absence of site-specific experience, it is recommended to use the average undrained shear strength, su,ave, in the equations presented in A.9.3 and A.9.4. Soil strength reduction from spudcan disturbance should be considered when utilizing this design profile. In addition, caution should be taken when applying the average undrained shear strength to bearing capacity calculation procedures that were previously developed and/or calibrated with the undrained shear strength obtained solely from UU triaxial compression tests. If the recommended UU triaxial, direct simple shear, and triaxial extension strength test data is not available, use of a shear strength design profile based on UU triaxial compression tests has been customary. Historically, strength data from high quality 3,0 in.-diameter push samples have been utilized in the customary best practice. In situ test data, soil disturbance assessment utilizing soil sensitivity, and correlation with site-specific spudcan penetration records can be utilized to refine the design profile based predominately on UU triaxial data. . No further reproduction or distribution permitted. Printed / viewed by: 95 A.6.5.2 Data integration The results of bathymetric surveys, sea floor surveys, shallow seismic surveys, seabed samples and geotechnical investigations should be integrated to assess the soil conditions at the proposed site. Lateral variations of geotechnical parameters can be assessed from the correlation of the shallow seismic data and the geotechnical information from the borehole logs and/or in situ tests. A.6.6 Earthquake data No guidance is offered. A.6.7 Ice data No guidance is offered. A.7 Guidance on actions A.7.1 Applicability Clause A.7 presents formulations and methods that can be applied to calculate actions for site-specific assessments. The wave and current actions are presented for quasi-static and dynamic analyses in A.7.3. Normally a quasi-static, deterministic extreme wave analysis is performed for jack-up site-specific assessments, and the dynamic effects are represented by an inertial loadset. Calculations of actions for stochastic analysis in time domain simulations are also presented. Such analyses are applicable for calculation of inertial loadsets or for the direct calculation of the structural responses including dynamic effects. The hydrodynamic formulations and coefficients are presented together with formulae for detailed and equivalent modelling of leg hydrodynamic actions. Wind models, flow coefficients for different structural parts and a formulation for the calculation of static wind actions are presented in A.7.3.4. Guidance on the determination of the functional actions is presented in A.7.4. A.7.2 General No guidance is offered. A.7.3 Metocean actions A.7.3.1 General A.7.3.1.1 Load cases The wave/current actions on the legs and other structures and the wind actions on the hull, legs and other structures should be considered due to either a) the 50 year return period individual extremes, or b) the most onerous combinations of the following 100 year joint probability metocean data: 1) 100 year return period wave, the associated current and associated wind; 2) 100 year 1 min wind, the associated wave and associated current; 3) 100 year current and the associated wave and associated wind. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 96 © ISO 2023 – All right reserved A.7.3.1.2 Methods for the determination of actions This subclause describes how the actions are developed for determining the jack-up response by one of two alternative methods, deterministic and stochastic. A deterministic analysis involves developing static metocean actions and an inertial loadset. The inertial loadset can be developed from either an SDOF method or a stochastic assessment of the wave actions to develop a DAF. A more detailed stochastic time domain analysis procedure implicitly includes inertial actions and can account for non-linearities of the action and foundation interaction. The action calculation procedure should follow the steps in the applicable column of Table A.7.3-1. Table A.7.3-1 — Metocean action calculation procedures Topic Description Deterministic analysis Stochastic DAF method Fully integrated stochastic analysis Water depth Define storm water depth considering LAT, tide and storm surge A.6.4.4 Current Define current velocity and profile. A.6.4.3 Determine the effective local current profile by multiplying the specified current profile by a factor accounting for interference from the structure on the flow field. A.7.3.3.4 Determine the current profile above mean water level in the presence of waves by stretching the current profile such that the surface component remains constant. A.6.4.3 Wave Specify wave height and range of associated wave periods. A.6.4.2.2 A.6.4.2.3 Determine if supplied wave periods are intrinsic or apparent and calculate the other value that has not been supplied A.7.3.3.5, ISO 19901-1:2015, 8.4.4 and A.8.4.3 Define the return period significant wave height and corresponding spectral peak period not applicable A.6.4.2.5, A.6.4.2.7 Calculate effective significant wave height as appropriate not applicable A.6.4.2.6 Specify wave spectrum, wave direction and wave spreading function not applicable A.6.4.2.5, A.6.4.2.8 Calculate wave velocities and accelerations by superposition of intrinsic wave components representing the wave spectrum and wave spreading functions not applicable A.7.3.3.3.2 Is deterministic wave subject to cancellation? A.10.4.2.5 not applicable Wave theory Determine the two-dimensional wave kinematics from an appropriate wave theory for the specified wave height, storm water depth, and intrinsic wave period A.7.3.3.3.1 not applicable Apply a reduction factor to the wave kinematics A.6.4.2.3 not applicable Scale the environment Apply partial factors to wind, wave and current to match factored deterministic actions not applicable A.10.5.3.2 Hydrodynamic modelling Establish detailed or equivalent leg models to represent structural members and appurtenances A.7.3.2.1, A.7.3.2.2, A.7.3.2.3, A.7.3.2.6 . No further reproduction or distribution permitted. Printed / viewed by: 97 Topic Description Deterministic analysis Stochastic DAF method Fully integrated stochastic analysis Determine drag and inertia coefficients (detailed or equivalent) as functions of member shape, roughness (marine growth), size, and orientation. A.7.3.2.4, A.7.3.2.5 Include the marine growth thickness relevant for the site and duration of the planned operation A.7.3.2.5 Wave/current action Combine local current profile vectorially with the wave kinematics to determine locally incident fluid velocities and accelerations for calculation of wave and current actions by Morison's equation. A.7.3.3.3.1, A.7.3.3.3.2 Wind Define wind speed and wind profile A.6.4.6 Wind action Define shape coefficients and calculate the static wind action. A.7.3.4 Functional actions Define functional actions A.7.4 Other actions Define other actions A.7.8 Stochastic DAF Does natural period coincide with cancellation or reinforcement not applicable A.7.3.3.3.3, A.10.4.2.5 not applicable Determine DAF stochastically not applicable A.10.5.2.2.3, A.10.5.3 not applicable Method of inclusion of dynamic effects in analysis Determine DAF either deterministically or stochastically. Represent dynamic effects by an inertial loadset A.10.5.2.2.2 A.10.5.2.2.3  follow deterministic analysis not applicable Does natural period coincide with cancellation or reinforcement? not applicable not applicable A.7.3.3.3.3, A.10.4.2.5 Action factors Apply action factors to the metocean actions and dynamic effects 8.8.1.2 not applicable 8.8.1.3 Load cases Develop assessment load case by linearly combining the factored metocean actions with the factored functional actions 8.8.1.1, A.10.5.2.2.3 not applicable 8.8.1.1 Additional load cases if (Tn/Tp) > 0,9 A.10.5.2.2.3 not applicable not applicable When a fully integrated stochastic analysis is undertaken (see 10.3), partial factors are applied to the metocean parameters instead of the metocean actions, as described in A.10.5.3 and 8.8.1.3. When using stochastic dynamic analyses for the purpose of determining a DAF, no partial action factors are applied; however, in the subsequent deterministic analysis including the inertial loadset based on the stochastic DAF, the action factors described in 8.8.1.2 are applied. A.7.3.2 Hydrodynamic model A.7.3.2.1 General The hydrodynamic modelling of the jack-up leg can be carried out by utilizing “detailed” or “equivalent” techniques. The hydrodynamic properties are then found as described in A.7.3.2.2 to A.7.3.2.4. In all cases, the provisions in the remainder of A.7.3.2.1 should be considered. The drag properties of some chords represented by the product of the drag coefficient CD and reference diameter Di differ for flow in the direction of the wave propagation (in the wave crest) and for flow back in the opposite direction (in the wave trough). Often the combined drag properties of all the chords on a . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 98 © ISO 2023 – All right reserved leg gives a total value along a particular axis that is independent of the flow direction. When this is not the case, it is recommended that the effect is included directly in the wave/current action model. Otherwise, where possible, the following is recommended: a) regular wave deterministic calculations use drag properties appropriate to the flow direction under consideration, noting that the flow direction is that of the combined wave particle motion and current; b) for random wave analyses, which are solely used to determine dynamic effects for inclusion in a final regular wave deterministic calculation on the basis of item a) above, an average drag property is considered; c) for random wave analyses from which the final results are obtained directly, the drag property in the direction of wave propagation is used. Lengths of members are normally taken as the node-to-node distance of the members in order to account for small non-structural items (e.g. anodes, jetting lines of less than 4" nominal diameter); see NOTE below. Large non-structural items, such as raw water pipes and ladders, should be included in the model. Free standing conductor pipes and raw water towers should be considered separately from the leg hydrodynamic model. For the purpose of this calculation, a node is defined as the point where two member axes intersect. Offsets between terminating members along the axis of the continuous member at the node may be used when calculating the equivalent CD. The contribution of the part of the spudcan above the sea floor should be investigated and only excluded from the model if it is shown to be insignificant. In water depths greater than 2,5Hs or where penetrations exceed half the spudcan height, the effect of the spudcan is normally insignificant. Otherwise, hydrodynamic actions should be modelled with hydrodynamic coefficients applicable for large diameter members; see ISO/TR 19905-2:2012, 7.3.2.4 and 7.3.2.5. On some jack-ups, the lower section of the leg adjacent to the spudcan can be heavily reinforced for towage; this should be explicitly modelled. For leg structural members, shielding and solidification effects should not normally be applied in calculating wave actions. The current flow is however reduced due to interference from the structure on the flow field, see A.7.3.3.4. NOTE The solidification effect, which increases the actions from waves due to interference from objects “side by side” in the flow field, is normally not included in the determination of the hydrodynamic coefficients or jack-ups. Jack-ups are usually space frame structures with few parallel members in close proximity so that shielding and solidification effects are usually not important. However, solidification can be important for closely spaced members such as are found in some raw water systems. Coefficients for individual members with closely attached appurtenances should be calculated by accounting for the combined shape with reference to relevant literature (DNV-RP-C205, 2021d). Model test data may be used for non-circular members, if available. In such cases the effects of roughness, Keulegan-Carpenter and Reynolds number dependence should be considered. The building block methodology described below was developed and calibrated for SNAME Technical and Research Bulletin 5-5A (2002)[170]. Model tests and analytical studies for complete legs are difficult to interpret and are unlikely to give results that are consistent with the methodology used here. This is particularly true for legs in which tubular members contribute significantly to the total drag coefficient because of Reynolds number dependency. . No further reproduction or distribution permitted. Printed / viewed by: 99 A.7.3.2.2 “Detailed” leg model All members are modelled with Morison coefficients accounting for member cross-section orientation relative to the flow direction. Members can be lumped together using the corresponding CDDr = ΣCDiDi and CmA = ΣCmiπDi2/4, accounting for flow direction, as defined in A.7.3.2.4. A.7.3.2.3 “Equivalent” leg model The hydrodynamic model of a bay is comprised of one, “equivalent” vertical tubular located at the geometric centre of the actual leg. The corresponding (horizontal) 𝑣𝑣n , 𝑢𝑢̇n and 𝑟𝑟̈n (see A.7.3.3.2) are applied together with equivalent CDD = ΣCDeDe and CmA = ΣCmeAe, as defined in A.7.3.2.4. The model should be varied with elevation, as necessary, to account for changes in dimensions, marine growth thickness, etc. When the hydrodynamic properties of a lattice leg are idealized by an “equivalent” model, the properties can be found using the method given below. The equivalent value of the drag coefficient, CDe, times the equivalent diameter, De, of the bay can be chosen as given in Formula (A.7.3-1): 𝐶𝐶De𝐷𝐷𝑒𝑒=𝐷𝐷𝑒𝑒Σ𝐶𝐶De𝑖𝑖 (A.7.3-1) The equivalent value of the drag coefficient for each member, CDei, is determined as given in Formula (A.7.3-2): 2223/2DeDe[sincossin]iiiiiiiDlCCDsββα=+ (A.7.3-2) where CDi is the drag coefficient of an individual member i as defined in A.7.3.2.4; Di is the reference diameter of member i (including marine growth as applicable) as defined in A.7.3.2.4; De is the equivalent diameter of leg, suggested as 2(/iiDlsΣ; li is the length of member i node to node centre; s is the length of one bay, or part of bay considered; αi is the angle between flow direction and member axis projected onto a horizontal plane; βi is the angle defining the member inclination from horizontal (see Figure A.7.3-1). Σ indicates summation over all members in one leg bay. The above expression for CDei can be simplified for horizontal and vertical members as given in Formulae (A.7.3-3) and (A.7.3-4): vertical members (e.g. chords): DeDe(/)iiiCCDD= (A.7.3-3) . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 100 © ISO 2023 – All right reserved horizontal members: ()3DeDesiniiiiiDlCCDsα= (A.7.3-4) The equivalent value of the inertia coefficient, Cme, and the equivalent area, Ae, representing the bay can be determined from the following: Cme is the equivalent inertia coefficient, which may normally be taken as 2,0 when using Ae; Ae is the equivalent area of leg per unit height, equal to (ΣAili)/s; Ai is the equivalent area of member or gusset, equal to πDi2/4; Di is the reference diameter, chosen as defined in A.7.3.2.4. For a more accurate model, the Cme coefficient may be determined as given in Formula (A.7.3-5): 𝐶𝐶me𝐴𝐴𝑒𝑒=𝐴𝐴𝑒𝑒Σ𝐶𝐶me𝑖𝑖 (A.7.3-5) where 𝐶𝐶me𝑖𝑖= [1+ (sin2𝛽𝛽𝑖𝑖+ cos2𝛽𝛽𝑖𝑖 sin2𝛼𝛼𝑖𝑖)(𝐶𝐶m𝑖𝑖−1)]􁉀𝐴𝐴𝑖𝑖 𝑙𝑙𝑖𝑖𝐴𝐴e𝑠𝑠􁉁 (A.7.3-6) Cmi is the inertia coefficient of an individual member, which is defined in A.7.3.2.4 related to reference dimension Di. For dynamic modelling the added mass of fluid per unit height of leg may be determined as ρAi (Cmi − 1) for a single member or ρAe(Cme − 1) for the equivalent model, provided that Ae is as defined above. Key 1 flow direction 2 member i s bay height αi angle between flow direction and axis of member i projected onto a horizontal plane βi angle defining the inclination of member i from horizontal NOTE Based on DNV-RP-C104, (DNV 2022b). Figure A.7.3-1 — Flow angles appropriate to a lattice leg . No further reproduction or distribution permitted. Printed / viewed by: 101 A.7.3.2.4 Drag and inertia coefficients Hydrodynamic coefficients for leg members are given in this subclause. Tubulars, brackets, split tube and triangular chords are considered. Hydrodynamic coefficients including directional dependence are given together with a fixed reference diameter Di. No other diameter should be used unless the coefficients are scaled accordingly. Unless better information is available for the computation of wave/current actions, the values of drag and inertia coefficients applicable to Morison's equation should be obtained from this subclause. Recommended values for hydrodynamic coefficients for tubulars with a diameter smaller than 1,5 m are given in Table A.7.3-2, based on the data discussed in the supporting ISO/TR 19905-2:2012, 7.3.2.4. Table A.7.3-2 — Base hydrodynamic coefficients for tubulars Surface condition CDi Cmi for wave load analysis Cmi for earthquake Smooth 0,65 2,0 2,0 Rough 1,00 1,8 2,0 The smooth values normally apply above MSL + 2 m and the rough values below MSL + 2 m, where MSL is as defined in A.6.4.4. If the jack-up has operated in deeper water and the fouled legs are not cleaned the surface should be taken as rough for wave actions above MSL + 2 m. Hydrodynamic coefficients for large diameter members may be calculated in accordance with ISO/TR 19905-2:2012, 7.3.2.4 and 7.3.2.5. Actions due to gussets should be determined using a drag coefficient as follows: CDi = 2,0 applied together with the projected area of the gusset visible in the flow direction, unless model test data show otherwise. This drag coefficient may be applied together with a reference diameter Di and corresponding length li chosen such that their product equals the plane area, Ai = Dili and Di = li (see Figure A.7.3-2). In the equivalent model of A.7.3.2.3 the gussets may be treated as an equivalent horizontal member of length li, with its axis in the plane of the gusset. Cmi should be taken as 1,0 and marine growth may be ignored. For non-tubular geometries (e.g. leg chords) the appropriate hydrodynamic coefficients may, in lieu of more detailed information, be taken in accordance with Figure A.7.3-3 or Figure A.7.3-4 and corresponding formulae, as appropriate. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 102 © ISO 2023 – All right reserved Key 1 flow direction 2 visible part of gusset i Ai area of gusset i; Ai = li Di Di reference diameter of gusset i li reference length of gusset i Figure A.7.3-2 — Gusset plates: equivalent modelling Key 1 flow direction 2 rough 3 smooth CDi drag coefficient for use with Di Di reference dimension of chord i W average width of the rack θ angle between flow direction and plane of rack (in degrees) Figure A.7.3-3 — Split tube chord and typical values for CDi . No further reproduction or distribution permitted. Printed / viewed by: 103 For a split tube chord as shown in Figure A.7.3-3 the drag coefficient CDi, related to the reference dimension Di = D + 2tm, the diameter of the tubular, including marine growth as in A.7.3.2.3, should be taken from Formula (A.7.3-7): ()Do2DDoD1Do;0°20°sin2097;20°90°/iiCCWCCCDθθθ<≤=+−−°<≤ (A.7.3-7) where tm is the marine growth thickness; θ is the angle in degrees; see Figure A.7.3-3; CDo is the drag coefficient for a tubular with appropriate roughness, see Table A.7.3-2; CD1 is the drag coefficient for flow normal to the rack (θ = 90°), related to projected diameter, W. CD1 is given by Formula (A.7.3-8): 𝐶𝐶D1= 􀵝1,8 1,4+ (𝑊𝑊/𝐷𝐷𝑖𝑖)/3 2.0 ; (𝑊𝑊/𝐷𝐷𝑖𝑖)<1,2; 1,2< (𝑊𝑊/𝐷𝐷𝑖𝑖)<1,8;1,8< (𝑊𝑊/𝐷𝐷𝑖𝑖) (A.7.3-8) The inertia coefficient CMi = 2,0, related to the equivalent volume πDi2/4 per unit length of member, can be applied to all heading angles and any roughness. Key 1 flow direction CDi drag coefficient for use with Di Di reference dimension (height of backplate) of chord i W width of chord to mid-point of rack tooth θ angle between flow direction and plane of rack (degrees) Figure A.7.3-4 — Triangular chord and typical values of CDi . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 104 © ISO 2023 – All right reserved For a triangular chord as shown in Figure A.7.3-4, the drag coefficient CDi related to the reference dimension Di = D, the backplate width, should be taken from Formula (A.7.3-9): CDi = CDpr(θ) Dpr(θ)/Di (A.7.3-9) where the drag coefficient related to the projected diameter, CDpr, is determined from Formula (A.7.3-10): Dpro170019590140105165180200180,;,;(),;,;,;Cθθθθθθθ=°=° ==°  =°−=° (A.7.3-10) Linear interpolation should be applied for intermediate headings. The projected diameter, Dpr(θ), should be determined from Formula (A.7.3-11): 𝐷𝐷pr(𝜃𝜃)= 􁉐𝐷𝐷𝑖𝑖 cos𝜃𝜃 𝑊𝑊sin𝜃𝜃+ 0,5 𝐷𝐷𝑖𝑖 |cos𝜃𝜃| 𝐷𝐷𝑖𝑖 |cos𝜃𝜃| ; 0< 𝜃𝜃< 𝜃𝜃0 ; 𝜃𝜃0< 𝜃𝜃< 180−𝜃𝜃0 ;180−𝜃𝜃0< 𝜃𝜃< 180 (A.7.3-11) The angle θo is the angle where half the rackplate is hidden, θo = arctan[Di/(2W)]. The inertia coefficient Cmi = 2,0 (as for a flat plate), related to the equivalent volume of πDi2/4 per unit length of member, can be applied for all headings and any roughness. Shapes, combinations of shapes or closely grouped non-structural items which do not readily fall into the above categories should be assessed from relevant literature (DNV-RP-C205, 2021d) and/or appropriate interpretation of (model) tests. The model tests should consider possible roughness, Keulegan-Carpenter and Reynolds number dependence. A.7.3.2.5 Marine growth Some of the influences of marine growth are:  an increase in the hydrodynamic diameter;  increases in weight, buoyancy, mass and added mass;  variation of the hydrodynamic drag coefficient as a function of roughness (see ISO/TR 19905-2). The thickness and type of marine growth depend on the site and can vary with duration on site, depth and season. Where possible, site-specific or regional data should be used. If such data are not available, all members below MSL + 2 m should be considered to have a marine growth thickness equal to 12,5 mm (i.e. total of 25 mm across the diameter of a tubular member). In some areas of the world, this default thickness can be significantly exceeded. The nominal sizes of structural members, conductors, risers, and appurtenances should be increased to account for the thickness of pre-existing and new marine growth. Marine growth on the teeth of elevating racks and protruding guided surfaces of chords can normally be ignored. . No further reproduction or distribution permitted. Printed / viewed by: 105 The marine growth thickness may be ignored if anti-fouling, cleaning or other means are applied. The surface roughness should still be taken into account, see A.7.3.2.4 or ISO/TR 19905-2:2012, A.7.3.2.4. A.7.3.2.6 Hydrodynamic models for appurtenances Raw water caissons on the legs and their guides should be included in the hydrodynamic model of the structure. NOTE The guides for raw water caissons can cause a significant increase in the leg drag load, especially when they are comprised of high drag sections such as I-beams, flat bar, etc. Depending upon the type and quantity, appurtenances can significantly increase the global wave actions. Appurtenances such as stairways, ladders and jetting lines should be considered for inclusion in the hydrodynamic model of the structure. Appurtenances are generally modelled by means of increasing the effective diameter and/or hydrodynamic coefficients of a structural member. A.7.3.3 Wave and current actions A.7.3.3.1 General Hydrodynamic actions for deterministic or stochastic analysis should be calculated using the Morison equation in combination with the hydrodynamic model and appropriate wave theories as described in the remainder of A.7.3.3. The wave and current velocities should be combined before they are used in the Morison equation. The intrinsic and apparent wave periods should be used appropriately; see A.7.3.3.5. A.7.3.3.2 Hydrodynamic actions Wave and current actions on slender members having cross-sectional dimensions sufficiently small compared with the wave length should be calculated using the Morison equation. The Morison equation is normally applicable providing that Lw > 5Di (A.7.3-12) where Lw is the wave length; Di is the reference dimension of member (e.g. tubular diameter). The Morison equation specifies the action per unit length as the vector sum as given in Formula (A.7.3-13): Δ𝐹𝐹=Δ𝐹𝐹drag+Δ𝐹𝐹inertia=0,5𝜌𝜌𝜌 𝐶𝐶D𝑣𝑣n|𝑣𝑣n|+𝜌𝜌𝐶𝐶m𝐴𝐴cs𝑢𝑢̇n−𝜌𝜌𝐶𝐶𝐴𝐴𝐴𝐴cs𝑟𝑟̈n (A.7.3-13) where the terms of the formula are described as follows. To obtain the drag action, the appropriate drag coefficient (CD) should be chosen in combination with a reference diameter, including any increase for marine growth, as described in A.7.3.2. The Morison drag action formulation is as given in Formula (A.7.3-14): Δ𝐹𝐹drag=0,5ρw𝐶𝐶D𝐷𝐷r𝑣𝑣n|𝑣𝑣n| (A.7.3-14) where . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 106 © ISO 2023 – All right reserved ΔFdrag is the drag action (per unit length) normal to the axis of the member considered in the analysis and in the direction of vn; ρw is the mass density of water (normally 1 025 kg/m3); CD is the drag coefficient (= CDi or CDe from A.7.3); vn is the fluid particle velocity resolved normal to the member axis; Dr is the reference dimension in a plane normal to the fluid velocity vn. Dr= Di or De from A.7.3. The fluid particle velocity, vn, may either be the absolute or relative fluid particle velocity. In a deterministic analysis, the absolute fluid particle velocity is applied. In a stochastic analysis, the fluid particle velocity, vn, may be taken as given in Formula (A.7.3-15): nnCnnvuVrα=+− (A.7.3-15) where un + VCn is the combined particle velocity found as the vector sum of the wave particle velocity and the current velocity, normal to the member axis; nr is the velocity of the considered member, normal to the member axis and in the direction of the combined particle velocity; α = 0, if an absolute velocity is to be applied, i.e. neglecting the structural velocity; = 1, if relative velocity is being included. It may be used for stochastic/random wave action analyses only if the following applies: u*Tn/Di ≥ 20 where u* is the particle velocity = VC + πHs/Tz,i; Tn is the first natural period of surge or sway motion; Di is the reference diameter of a chord. NOTE See also A.10.4.3 for relevant damping coefficients depending on α. To obtain the inertia action, the appropriate inertia coefficient (Cm) should be taken in combination with the cross-sectional area of the geometric profile, including any increase for marine growth, as described in A.7.3.2.3. The Morison's inertia action formulation is as given in Formula (A.7.3-16): 𝛥𝛥𝐹𝐹inertia = 𝜌𝜌 𝐶𝐶m 𝐴𝐴cs 𝑢𝑢̇n−𝜌𝜌 𝐶𝐶𝐴𝐴 𝐴𝐴cs 𝑟𝑟̈n (A.7.3-16) where ΔFinertia is the inertia action (per unit length) normal to the member axis and in the direction of nu; Cm is the inertia coefficient; Acs is the cross-sectional area of member (equal to Ai or Ae from A.7.3.2); nu is the wave particle acceleration normal to member; . No further reproduction or distribution permitted. Printed / viewed by: 107 CA is the added mass coefficient, CA = Cm − 1; nr is the acceleration of the considered member, normal to the member axis and in the direction of the combined particle acceleration. The last term in Formula (A.7.3-16) is not included in a deterministic analysis. The term should be included in a stochastic analysis representing the added mass force due to the member acceleration. 𝑚𝑚𝑎𝑎 𝑟𝑟̈ 𝑛𝑛 = 𝜌𝜌 𝐶𝐶𝐴𝐴 𝐴𝐴cs 𝑟𝑟̈ 𝑛𝑛 (A.7.3-17) where ma is the added mass contribution (per unit length) for the member. In a dynamic response analysis, the added mass (ma integrated over the member length) is normally transferred to the left-hand side of the formula of motion and added to the structural mass. A.7.3.3.3 Wave models A.7.3.3.3.1 Deterministic waves For deterministic analyses an appropriate wave theory for the water depth, wave height and period should be used, based on the curves from ISO 19901-1:2015, A.8.4.2, as shown in Figure A.7.3-5. For practical purposes, Stokes' 5th (within its bounds of applicability) or an appropriate order of Dean's Stream Function are acceptable for regular wave elevated storm analysis. If breaking waves are indicated according to ISO 19901-1:2015, A.8.4.2, it is recommended that the wave period is changed to conform with the breaking limit for the specified height. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 108 © ISO 2023 – All right reserved Key dw water depth g acceleration due to gravity H maximum wave height Hb breaking wave height Ti intrinsic wave period A deep water breaking limit <<H/Lw = 0,14, where Lw is the wave length B Stokes' fifth order, New-wave or third order stream function C shallow water breaking limit H/dw = 0,78 D stream function (showing order number) E linear/Airy or third order stream function F shallow water G intermediate depth H deep water NOTE Taken from ISO 19901-1:2015. Figure A.7.3-5 — Regions of applicability of alternative wave theories A.7.3.3.3.2 Stochastic waves Time domain analysis is recommended for stochastic wave jack-up analysis. In such analyses the waves are modelled using a random superposition model to represent the wave spectrum; see A.6.4.2.5 to A.6.4.2.8. It is recommended that the random sea state be generated from the summation of at least 200 component waves of height and frequency determined to match the wave spectrum. The phasing of the component waves should be selected at random. A two-dimensional first order simulation using linear (Airy) waves is normally sufficient. However, when the effects of wave spreading is explicitly . No further reproduction or distribution permitted. Printed / viewed by: 109 included in the analysis method, a three-dimensional simulation using a higher order wave theory should be used to capture higher frequency interaction effects (e.g. those due to frequency sum terms). For first order wave kinematic models, the extrapolation of the wave kinematics to the free surface (wave stretching) is most appropriately carried out by substituting the true elevation at which the kinematics are required with one which is at the same proportion of the still water depth as the true elevation is of the instantaneous water depth. This can be expressed as given in Formula (A.7.3-18): 𝑧𝑧′ =𝑧𝑧k−𝜁𝜁w1+ 𝜁𝜁w𝑑𝑑w (A.7.3-18) where z′ is the modified coordinate for use in particle velocity formulation; zk is the vertical coordinate relative to the SWL under consideration, positive upwards, at which the kinematics are required; ζw is the instantaneous water level (same axis system as z); dw is the water depth, still or undisturbed (positive). This method ensures that the kinematics at the instantaneous free surface are always evaluated from the linear wave theory expressions as if they were at the still water level, see Wheeler (1969)[199] and ISO/TR 19905-2:2012, A.7.3.3.3.2. For higher order wave-kinematic models, an appropriate alternative for stretching the wave profile to the instantaneous wave surface should be adopted. The statistics of the underlying random wave process are Gaussian and fully known theoretically. The empirical modification around the free surface to account for free surface effects, together with the fact that drag actions are a non-linear (squared) transformation of wave kinematics, makes the hydrodynamic action excitation always non-linear. As a result, the random excitation is non-Gaussian. The statistics of such a process are generally not known theoretically, but the extremes are generally larger than the extremes of a corresponding Gaussian random process. For a detailed investigation of the dynamic behaviour of a jack-up, the non-Gaussian effects should be included. Multiple procedures for doing this are presented in Annex C. When the random displacements of the submerged parts are small and the velocities are significant with respect to the water-particle velocities, the damping is not well represented by the relative velocity formulation in the Morison equation, which tends to overestimate the damping and underpredict the response. A criterion for determining the applicability of the relative velocity formulation is given in A.7.3.3.2. A summary of recommendations for the time domain modelling of random waves is given in Table A.7.3-3. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 110 © ISO 2023 – All right reserved Table A.7.3-3 — Recommendations for modelling of time domain stochastic waves Method Recommendations Time domain Generate random sea from at least 200 components and use divisions of generally equal energy. It is recommended that smaller energy divisions be used in the higher frequency portion of the spectrum, which generally contains the reinforcement and cancellation frequencies. For each component, the relationship between wave length and frequency should be taken according to its linear dispersion relationship (Sarpkaya, 1981)[160]. Unless indicated otherwise in the site-specific information, the validity of wave surface simulation should be checked against the criteria given below. The criteria for higher order waves should be taken to ensure that Hs, mean waves and maximum crests are within practical limits.  correct mean wave elevation;  standard deviation = (Hs/4) ± 1 %;  −0,03 < skewness < 0,03;  2,9 < kurtosis < 3,1;  maximum crest elevation = (Hs/4)􀶥2ln(𝑁𝑁C) −5 % to +7,5 %; where 𝑁𝑁C is the number of cycles in the time series being qualified, 𝑁𝑁C ≈ Duration/Tz. Integration time step less than the smaller of Tz/20 or Tn/20 where Tz is the apparent mean zero-upcrossing period of the wave spectrum; Tn is the jack-up natural period, see A.10.4.2.1 (unless it can be shown that a larger time step leads to no significant change in results). Avoid transient effects, discard at least the first 100 s (the “run-in”). Ensure the simulation is of sufficient duration so that the method chosen results in demonstrably stable MPME responses; see also A.10.5.3.4 and C.2. A.7.3.3.3.3 The effect of directionality and spreading on dynamic response Both the magnitude of the actions on the structure and the dynamic amplification are affected by cancellation and reinforcement of wave actions, dependent on leg spacing (heading) and wave length. The effects of directionality and wave spreading should therefore be considered in any random dynamic analysis. The following two methods can be used to develop a representative DAF in conjunction with adjustments to the natural period (A.10.4.2.5.3). Method 1: In a two-dimensional long-crested simulation, the effect of directionality can be included by developing a base shear transfer function (BSTF) accounting for spreading, “BSTF with spreading”, as described below [see 7.6.4 of Sarpkaya (1981)[160]]. a) Develop a set of two-dimensional BSTFs, one for the “principal” direction of interest, and the others offset from the principal direction. b) For each offset direction, calculate a directionality contribution factor from ISO 19901-1:2015, A.8.3.2.1, or from ISO/TR 19905-2:2012, 6.4.2.8. Each factor corresponds to a given percentage of area under the directionality function such that the sum of all the factors is 1,0. c) The “BSTF with spreading” is then the sum of each two-dimensional BSTF (principal one plus the offset directions) multiplied by the corresponding directionality factors. Be aware that only the principal direction vector component of the offset direction BSTFs is used. d) The BSTF for the chosen two-dimensional (long-crested/unspread) analysis direction and the “BSTF with spreading” are compared to determine whether the selected direction is unconservative. Optimally, the direction of the two-dimensional sea state should be chosen to obtain a match with the three-dimensional BSTF for the entire wave frequency range. If this is not possible, the match between the spread and unspread BSTFs should be good at the natural period. . No further reproduction or distribution permitted. Printed / viewed by: 111 Method 2: To minimize reinforcement and cancellation effects, it is suggested that the dynamic analysis be carried out for a single wave heading along an axis that is neither parallel nor normal to a line through two adjacent leg centres. Thus, for a 3-legged jack-up with equilateral leg positions and a single bow leg, suitable analysis headings can be with the weather approaching from approximately 15° or 45° off the bow. The DAFs should be determined for one, or both, of these headings with suitably adjusted natural period; see Figure A.10.4-1. The DAFs (or more conservative DAFs) can then be applied to the final deterministic analysis for all headings. A.7.3.3.4 Current The current velocity and profile as specified in A.6.4.3 should be used. Where the current profile is defined by discrete points, linear interpolation between the data points is sufficient. The current induced drag actions are determined in combination with the wave actions. This is carried out by the vectorial addition of the wave and current induced particle velocities prior to the drag action calculations. The current velocity may be reduced to account for interference from the structure with the flow field of the current, as given in Formula (A.7.3-19); see Taylor (1991)[179] and ISO/TR 19905-2:2012, 7.3.3.4: 1CfDeeF14[/()]VVCDD−=+ (A.7.3-19) where VC is the current velocity for use in the hydrodynamic model; VC should not be taken as less than 0,7Vf; Vf is the far field (undisturbed) current velocity; CDe is the equivalent drag coefficient of the leg, as defined in A.7.3.2; De is the equivalent diameter of the leg, as defined in A.7.3.2; DF is the face width of leg, outside dimensions, orthogonal to the flow direction. A.7.3.3.5 Intrinsic and apparent wave periods The intrinsic wave period is based on a reference frame travelling with the speed and direction of the current, and should be used, except as detailed later in this subclause, to calculate the wave kinematics. The apparent wave period is that which is observed by a stationary observer and is the period that should be used to calculate the jack-up dynamics. The intrinsic wave period, in conjunction with the water depth and appropriate wave theory, are used to calculate the wave length. NOTE 1 There is only the intrinsic wave length; there is no apparent wave length. If one applies the apparent wave period in an analysis, the excitation period is correct but both the kinematics and the wave length are wrong. The wrong wave length means that the legs of a jack-up are at the wrong relative positions in the wave. The conceptual solution is to model the un-modified intrinsic wave with the jack-up moving into the wave at the current velocity. It is important to determine whether the supplied wave period is apparent or intrinsic, taking due care to ensure that ISO 19901-1 terminology is consistently adhered to at all times. ISO 19901-1 terminology can conflict with the definition of these terms used by the supplier of the metocean data. NOTE 2 ISO 19901-1 uses terminology conflicting from that in API RP 2A-LRFD, (1993)[14]. In ISO 19901-1, the “apparent” wave period is defined as the wave period seen by a stationary observer, while the “intrinsic” wave . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 112 © ISO 2023 – All right reserved period is the wave period seen by an observer moving with the current. In API RP 2A the “actual” wave period is defined as the wave period seen by a stationary observer, while the “apparent” wave period is the wave period as it “appears” to an observer moving with the current. By comparison, ISO 19901-1 “intrinsic” equates to RP 2A “apparent”, and ISO 19901-1 “apparent” equates to RP 2A “actual”. Formulae for transformation between the intrinsic and apparent wave periods are given in ISO 19901-1:2015, A.8.4.3. It gives no direct guidance on modifying short-crested sea states, although a suitable method can be inferred. The assessor should ensure that the correct procedure is used by the software in calculating wave particle kinematics and dynamics; it is important to understand the terminology used by the software vendor; see NOTE 2. In summary, the steps taken to convert intrinsic to apparent wave period are as follows. a) Calculate the wave length based on the intrinsic wave period and the water depth, using a suitable wave theory. b) Calculate the intrinsic wave celerity as wave length divided by intrinsic wave period. c) Calculate the apparent wave celerity by adding the resolved current velocity to the wave celerity (the celerity is increased if the current is in the same direction as wave propagation, and decreased if in an opposing direction). d) Calculate the apparent wave period as the wave length divided by the apparent celerity. Conversion from an apparent wave period to an intrinsic wave period follows a similar approach but is undertaken iteratively. Care should be taken with opposing currents that the vector sum of apparent celerity and current is always greater than or equal to zero, otherwise the waves move backwards. This is likely to be relevant only for very short period waves when developing the apparent component periods of a random sea state. This conversion procedure between apparent and intrinsic periods strictly applies in the case of simple uniform currents over the full water depth. It can be used practically if the current is uniform over the top 50 m of the water column. In cases of a non-uniform current profile, a weighted, depth-averaged in-line current speed, VIN-LINE, may be used, as shown in ISO 19901-1:2015, A.8.4.3, and Kirby and Chen (1989)[120] and as given in Formula (A.7.3-20): 𝑉𝑉IN−LINE= 2𝑘𝑘sinh(2𝑘𝑘𝑑𝑑w)∫𝑉𝑉c(𝑧𝑧) cos􀵫𝜃𝜃(𝑧𝑧)􀵯0−𝑑𝑑cosh[2𝑘𝑘(𝑧𝑧+𝑑𝑑w)]dz (A.7.3-20) where k is the wave number = 2π/Lw ; Lw is the actual wave length (i.e. deep water wave length corrected for water depth); dw is the water depth; 𝑉𝑉c(𝑧𝑧) is the current velocity at depth z; z is the vertical coordinate relative to the SWL under consideration, positive upwards; 𝜃𝜃(𝑧𝑧) is the angular direction of the current at depth z relative to the wave propagation direction; 𝜃𝜃(𝑧𝑧) = 0,0 when in line. In a two-stage analysis the deterministic quasi-static wave/current actions should be determined using the intrinsic period. . No further reproduction or distribution permitted. Printed / viewed by: 113 The apparent wave period should be used for the SDOF DAF calculation of KDAF,SDOF. For stochastic calculations, the rigorous approach is to develop the particle kinematics for the components using the intrinsic wave period and to develop the wave/current actions by applying the intrinsic kinematics to the jack-up by using component wave phases based on the apparent wave period. This approach should be used for one-stage analysis and for two-stage analysis with a non-linear foundation model for the DAF calculations. This procedure is difficult if the available analytical tools do not have the feature implemented. When undertaking a two-stage deterministic storm analysis (A.10.5.2) using a DAF developed from a random dynamic analysis (A.10.5.2.2.3) with linearized foundations, it can be acceptable to use a spectrum with an apparent peak period for all stages in the calculation of KDAF,RANDOM and the inertial loadset. The error is expected to be small when the ratio Tp,i/Tp is within the range 1 ± 0,08. If this approach is used, the analysis should also be undertaken without period adjustment and the more onerous DAFs used. When Tp,i/Tp is outside this range, a more rigorous approach should be considered. A.7.3.4 Wind actions A.7.3.4.1 Wind action The wind action on each component (divided into blocks of not more than 15 m vertical extent), FWi, can be computed using Formula (A.7.3-21): WWiiiFPA= (A.7.3-21) where Pi is the pressure at the centre of block i; AWi is the projected area of block i perpendicular to the wind direction. The pressure Pi should be computed using Formula (A.7.3-22): 𝑃𝑃𝑖𝑖=0,5ρa𝑉𝑉Z𝑖𝑖2𝐶𝐶s (A.7.3-22) where ρa is the mass density of air (taken as 1,222 4 kg/m3 unless an alternative value can be justified for the site); Vzi is the specified wind velocity at the centre of block i; see A.6.4.6.2; Cs is the shape coefficient, as given in A.7.3.4.2. Wind actions on legs below the hull should be calculated to either the instantaneous wave surface or to SWL. NOTE The wind area of the hull and associated structures (excluding derrick and legs) can normally be taken as the projected area viewed from the wind direction under consideration. A.7.3.4.2 Shape coefficient Using building block elements, the shape coefficients in Table A.7.3-4 should be used. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 114 © ISO 2023 – All right reserved Table A.7.3-4 — Shape coefficients Type of member or structure Shape coefficient, Cs Hull side (flat side) 1,0 based on total projected area Hull and associated structures (excluding derrick and legs) 1,1 based on the total projected area (i.e. the area enclosed by the extreme contours of the structure) Deckhouses, jack-frame structure, sub-structure, draw-works house, and other above-deck blocks 1,1 based on the projected area Leg sections projecting above jack-frame structure and below the hull Cs = CDe as determined from A.7.3.2.3, normally using smooth drag coefficients (ignoring marine growth) AWi determined from De and section length Isolated tubulars (crane pedestals, etc.) 0,5 Isolated structural shapes (angles, channels, box, I-sections) 1,5 based on member projected area Derricks, crane booms, flare towers (open lattice sections only, not boxed-in sections) The appropriate shape coefficient for the members concerned applied to 50 % of the total projected profile area of the item (25 % from each of the front and back faces) Shapes or combinations of shapes that do not readily fall into the above categories should be subject to special consideration. A.7.3.4.3 Wind tunnel data Wind pressures and resulting actions for the hull and associated structures may be determined from wind tunnel tests on a representative model. Care should be exercised when interpreting wind tunnel data for structures mainly comprised of tubular components, such as truss legs. A.7.4 Functional actions Provided appropriate procedures exist and it is practical to change the mode of the jack-up from operating to elevated storm mode on receipt of an unfavourable weather forecast, it is necessary to assess only the elevated storm mode. Consideration should be given to actions on the conductors if supported by the jack-up. The following should be defined: a) actions due to the maximum and minimum elevated weight. In the absence of other information, the minimum elevated weight can normally be determined assuming 50 % of the variable load permitted by the operating manual; b) extreme limits of the centre of gravity position (or reactions of the elevated weight on the legs) for the configurations in a) above; c) substructure and derrick position, hook load, rotary load, setback and conductor tensions for the configurations in a) above; d) weight, centre of gravity and buoyancy of the legs. If a minimum elevated weight or a limitation of the centre of gravity position is required to meet the overturning acceptance criteria (see 5.4.4 and 13.8), then the addition of water in lieu of variable load is permitted in the assessment, provided that  the functional actions do not exceed the operations manual limits,  procedures, equipment and instructions exist for performing the operation of adding water offshore, and . No further reproduction or distribution permitted. Printed / viewed by: 115  the action due to the maximum variable load, including added water, is used for all appropriate assessment checks (preload, stress, etc.). If a reduction in elevated weight or a limitation of the centre of gravity position is required to meet the foundation acceptance criteria with respect to foundation sliding, see 5.4.4 and 13.9.1, then the variable load used in the assessment can be revised accordingly provided that procedures, equipment and instructions exist for the timely performance of the operation offshore. A.7.5 Displacement dependent actions No guidance is offered. A.7.6 Dynamic effects No guidance is offered. A.7.7 Earthquakes See 10.7 and A.10.7. A.7.8 Ice actions See 10.8 and A.10.8. A.7.9 Other actions Other actions should be represented as relevant for the site. For areas where icing is possible during the planned operation, the effect on weight and on the environmental actions should be considered. Relevant data for the region should be applied. For calculating wave, current and wind actions, increases in dimension and changes in shape and surface roughness can be significant. A.8 Guidance on structural modelling A.8.1 Applicability Techniques for modelling the legs, hull, leg-to-hull connection, and leg/spudcan connection are discussed. The leg-to-hull connection model includes the upper and lower guides, jacking pinions, fixation systems, and jackcase/associated bracing. Modelling of the foundation is limited to the structural details in this clause; geotechnical aspects are presented in A.9. Because of the interaction of the mass and stiffness models, e.g. the effect of mass modelling on hull sag, it is recommended that the assessor be familiar with the whole of this clause before commencing the modelling. A.8.2 Overall considerations A.8.2.1 General No guidance is offered. A.8.2.2 Modelling philosophy The structural model should accurately reflect the complex mechanism of the jack-up; for most jack-up configurations this requires the use of an FE computer model. A.8.3 to A.8.5 describe the structural . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 116 © ISO 2023 – All right reserved aspects of the model. A.8.6 describes the interaction of the structural model with the foundation. A.8.7 describes modelling the mass and A.8.8 describes the application of the actions. A.8.2.3 Levels of FE modelling While it can be desirable to fully model the jack-up when assessing its structural strength, this is rarely necessary for a site-specific assessment. An overly complex model can introduce errors and unnecessarily complicate the assessment. Consequently, assumptions and simplifications, such as equivalent hull, equivalent leg, etc., are often made when building the model(s) used for the assessment. In view of this, one of the various levels of modelling described in a) through d) below can be used. It should be recognized that some of these methods have limitations with respect to the accuracy of assessing the structural adequacy of a jack-up. Table A.8.2-1 outlines the limitations of the various modelling techniques and should be referenced to ensure that the selected model addresses all aspects required for the assessment. When simplified models, such as those described in b) and d) are used, it is usually appropriate to calibrate them against a more detailed model. a) Fully detailed leg model: The model consists of “detailed legs”, hull, leg-to-hull connections and spudcans modelled in accordance with A.8.3.2, A.8.4, A.8.5 and A.8.6, respectively. The results from this model can be used to examine all aspects of a jack-up site-specific assessment, including foundation stability, overturning resistance, leg strength and the adequacy of the jacking system or fixation system. b) Equivalent leg (stick model): The model consists of “stick model” legs (see A.8.3.3), hull structure modelled using beam elements (see A.8.4.3), leg-to-hull connections (see A.8.5) and spudcans modelled as a stiff or rigid extension to the equivalent leg. The results from this model can be used to examine foundation stability and overturning resistance. This model can also be used to obtain reactions at the spudcan and internal forces and moments in the leg in the vicinity of the lower guide for application to the “detailed leg” and leg-to-hull connection model d). c) Combined equivalent/detailed leg and hull model: The model consists of a combination of “detailed leg” for the upper portion of legs and “stick model” for the lower portion of the legs (see A.8.3.4). The hull, leg-to-hull connections and spudcans are modelled in accordance with A.8.4, A.8.5 and A.8.6, respectively. The results from this model can be used to examine foundation stability, overturning resistance, leg strength in the region of the leg-to-hull connections and the adequacy of the jacking and/or fixation systems. See Figure A.8.2-1. d) Detailed single leg and leg-to-hull connection model: The model consists of a “detailed leg” or a portion of a “detailed leg” (see A.8.3.2), the leg-to-hull connection (see A.8.5) and, when required, the spudcan (see A.8.6). The results from this model can be used to examine the leg strength and the adequacy of the jacking and/or fixation systems. . No further reproduction or distribution permitted. Printed / viewed by: 117 Figure A.8.2-1 — Combined equivalent/detailed leg and hull model . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 118 © ISO 2023 – All right reserved Table A.8.2-1 — Applicability of the suggested models Applicability Model type I II III IV V VI VII Base shear and overturning moment Overturning checks Foundation checks Global leg forces Leg member forces Jacking/fixation system reactions Hull element forces a) Fully detailed leg Yes Yes Yes Yes Yes Yes See note b) Equivalent leg (stick model) Yes Yes Yes Yes — — — c) Combined equivalent/detailed leg and hull Yes Yes Yes Yes Yes Yes See note d) Detailed single leg and leg-to-hull connection model — — — — Yes Yes — NOTE Hull stresses are only available from more complex hull models. A.8.3 Modelling the leg A.8.3.1 General For truss legs the model(s) can be generated in accordance with A.8.3.2 to A.8.3.4 as applicable. Single column legs can be modelled with beam elements (see A.8.3.3) or by means of other appropriate finite elements with due consideration for local and global buckling. A.8.3.2 Detailed leg Modelling should account for offsets between member work points and centroids, as omitting this detail can be unconservative. If member offsets are not included in the model, analysis of the relevant joints should consider their effect. Gusset plates are typically omitted in the structural leg model. However, their beneficial effects can be taken into account in the calculation of member and joint strength. A.8.3.3 Equivalent leg (stick model) The leg structure can be simulated by a series of collinear beams with the equivalent cross-sectional properties calculated using the formulae indicated in Tables A.8.3-1 and A.8.3-2 or derived from the application of suitable unit load cases to the 'detailed leg'. The stiffness properties of the equivalent leg should equate to those of the 'detailed leg' model described in A.8.3.2. Where such a model is used, relevant analysis results can be applied to a detailed leg model to determine member stresses, fixation system/pinion forces, etc. The determination of stiffness for the equivalent leg model can be accomplished as outlined below. a) From hand calculations using the formulae presented in Tables A.8.3-1 and A.8.3-2. If the leg scantlings change in different leg sections, this can be accounted for by calculating the properties for each leg section and creating the equivalent leg model accordingly. Provided that there are no significant offsets between the brace work points, these are reasonably accurate for cases A (sideways K bracing), C (X bracing) and D (Z bracing). Case B (normal K bracing) should be used with caution as the values of equivalent shear area and second moment of area are dependent on the number of bays being considered. . No further reproduction or distribution permitted. Printed / viewed by: 119 b) From the application of unit load cases to a detailed leg model prepared in accordance with 8.3.2 and 8.3.5: The leg should be rigidly restrained, generally at the first point of lateral force transfer between the hull and the leg, although it can be more convenient to use a different reference point, e.g. level of the fixation system or neutral axis of the hull. The variables Δ, δM, θM and θP used in Formulae (A.8.3-1) to (A.8.3-4) are obtained from the detailed leg model. The following load cases should be considered, applied about the major and minor axes of the leg:  Axial unit load case: This is used to determine the axial area, Aeq, of the equivalent leg model beam according to standard beam theory as given in Formula (A.8.3-1): 𝛥𝛥 = 𝐹𝐹𝐿𝐿c𝐴𝐴eq𝐸𝐸⇒𝐴𝐴eq=𝐹𝐹𝐿𝐿c𝐸𝐸𝐸𝐸 (A.8.3-1) where Δ is the axial deflection (shortening) of the cantilever at the point of force application; F is the applied axial action; Lc is the cantilevered length from the hull to the seabed reaction point; see A.8.6.2; E is Young's modulus of steel.  Pure moment applied either as a moment or as a couple at the end of the cantilever: This is used to derive the second moment of area (I) according to standard beam theory as given in Formula (A.8.3-2): 𝛿𝛿M=𝑀𝑀𝐿𝐿c22𝐸𝐸𝐸𝐸⇒𝐼𝐼=𝑀𝑀𝐿𝐿c22𝐸𝐸𝛿𝛿M and 𝜃𝜃𝑀𝑀=𝑀𝑀𝐿𝐿c𝐸𝐸𝐸𝐸⇒𝐼𝐼=𝑀𝑀𝐿𝐿c𝐸𝐸𝜃𝜃𝑀𝑀 (A.8.3-2) where δM is the lateral deflection of the cantilever at the point of moment application; M is the applied moment; θM is the slope of the cantilever at the point of moment application. It should be recognized that the value of I resulting from the two formulae can differ somewhat.  Pure shear, P, applied at the end of the cantilever, which can be used to derive I according to standard beam theory as given in Formula (A.8.3-3): 𝜃𝜃𝑃𝑃=𝑃𝑃𝐿𝐿c22𝐸𝐸𝐸 ⇒𝐼𝐼=𝑃𝑃𝐿𝐿c22𝐸𝐸𝜃𝜃𝑃𝑃 (A.8.3-3) where P is the applied shear; θP is the slope of the cantilever at the point of shear application. Using either this value of I, or a value obtained from the pure moment case, the effective shear area, Aseff, of the equivalent leg model beam can then be determined using Formula (A.8.3-4): 𝛿𝛿M=𝑃𝑃𝐿𝐿c33𝐸𝐸𝐸 +𝑃𝑃𝐿𝐿c𝐴𝐴seff𝐺𝐺 ⇒𝐴𝐴seff=7,8𝑃𝑃𝐿𝐿c𝐼𝐼3𝐸𝐸𝐸 𝛿𝛿M−𝑃𝑃𝐿𝐿c3 (A.8.3-4) where G is the shear modulus of steel, G = E/2,6 for Poisson's ratio of 0,3 for steel. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 120 © ISO 2023 – All right reserved Table A.8.3-1 — Formulae for determining the effective shear area for two dimensional structures Structure Effective shear area of frame, Asi A 2si33Dc126()shAdsAAν+=+ B 2si33332Dvc1183()NishAdhsNiAANAν=+=+−−Σ C 2si33Dc1412()shAdsAAν+=− D 2si333Dvc1226()shAdhsAAAν+=++ E Gsi22GB48121()IAIdsshIν+=+ Key s bay height AV area of horizontal brace h centre to centre of chords on face ν Poisson's ratio (0,3 for steel) d length of diagonal brace on face IG largest inertia of chord AC area of chord IB largest inertia of brace AD area of diagonal brace N number of active bays NOTE 1 The stiffness properties are the same for all directions unless the chords have different areas. NOTE 2 The formulae can be inaccurate if significant offsets exist between brace work points. NOTE 3 The equivalent beam end rotations can be inaccurate for bracing type C. This can be important if this modelling is used in conjunction with rotational foundation stiffness. NOTE 4 Based on DNV-RP-C104, (DNV 2022b). . No further reproduction or distribution permitted. Printed / viewed by: 121 Table A.8.3-2 — Formulae for determining the equivalent section properties of three-dimensional lattice legs Leg type Equivalent properties A 𝐴𝐴eq=3𝐴𝐴Ci 𝐴𝐴sy=𝐴𝐴sz=32𝐴𝐴si 𝐼𝐼𝑦𝑦=𝐼𝐼𝑧𝑧=12𝐴𝐴Ciℎ2 𝐼𝐼𝑇𝑇=14𝐴𝐴siℎ2 B 𝐴𝐴eq=4𝐴𝐴Ci 𝐴𝐴sy=𝐴𝐴sz=2𝐴𝐴si 𝐼𝐼𝑦𝑦=𝐼𝐼𝑧𝑧=𝐴𝐴Ciℎ2 𝐼𝐼𝑇𝑇=𝐴𝐴siℎ2 C 𝐴𝐴eq=4𝐴𝐴Ci 𝐴𝐴sy=𝐴𝐴sz=2𝐴𝐴si 𝐼𝐼𝑦𝑦=𝐼𝐼𝑧𝑧=𝐴𝐴Ciℎ2 𝐼𝐼𝑇𝑇=𝐴𝐴siℎ2 Key Asi effective shear area for two-dimensional structure (from Table A.8.3-1) ACi individual chord area As effective shear area about representative axis (y or z) I second moment of area about representative axis (y or z) IT torsional moment of inertia NOTE 1 ACi can be taken as the cord area including a contribution from the rack teeth (see 8.3.5). NOTE 2 Based on DNV-RP-C104 (DNV 2022b). A.8.3.4 Combination of detailed and equivalent leg The combined detailed and equivalent leg model should be constructed with the areas of interest modelled in detail and the remainder of the leg modelled as an equivalent leg. To facilitate obtaining detailed stresses in the vicinity of the leg-to-hull connection (guides, fixation/jacking system, etc.), the detailed portion of the leg model should extend far enough above and below this region to ensure that boundary conditions at the 'detailed leg'/'equivalent leg' connection do not affect stresses in the areas of interest. Care should be taken to ensure an appropriate interface and consistency of boundary conditions at the connections. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 122 © ISO 2023 – All right reserved The plane of connection between the "detailed leg" and the "equivalent leg" should remain a plane and without shear distortion when the leg is bent. The connection should be composed of rigid elements that control local bending and shear distortion. A.8.3.5 Stiffness adjustment No guidance is offered. A.8.3.6 Leg inclination No guidance is offered. A.8.4 Modelling the hull A.8.4.1 General Recommended methods of modelling the hull structure are given in A.8.4.2 and A.8.4.3. Hull mass modelling is discussed in A.8.7 and the modelling of hull sagging is discussed in A.8.8.3. A.8.4.2 Detailed hull model The model should be generated using plate elements in which appropriate directional modelling of the effect of the stiffeners on the plates should be included. The elements should be capable of carrying in-plane shear and out-of-plane moment. A.8.4.3 Equivalent hull model In an equivalent hull model, the deck, bottom, side shell and major bulkheads are modelled as a grillage of beams. The axial and out-of-plane properties of the beams should be calculated based on the depth of the bulkheads, side shell and the "effective width" of the deck and bottom plating. Beam elements should be positioned with their neutral axes at mid-depth of the hull. Due to the continuity of the deck and bottom structures and the dimensions of a typical hull box, the in-plane bending stiffness can be treated as large relative to the out-of-plane stiffness. The torsional stiffness should be approximated from the closed box section of the hull and distributed between the grillage members. A.8.5 Modelling the leg-to-hull connection A.8.5.1 General The leg-to-hull connection modelling is of extreme importance to the analysis since it controls the distribution of leg bending moments and shears carried between the upper and lower guide structures and the jacking or fixation system. It is, therefore, necessary that these systems be properly modelled in terms of stiffness, orientation and clearance. A simplified derivation of the equivalent leg-to-hull connection stiffness can be used for the equivalent leg (stick model). A specific jack-up design concept can be described by a combination of the following components (see also Figure C.1-1): a) with or without fixation system; b) with opposed jacking pinions [see Figure A.8.5-1 a)]; c) with unopposed jacking pinions [see Figure A.8.5-1 b)]; d) with pin and yoke jacking system [see Figure A.8.5-1 c)]; e) with fixed or floating jacking system. . No further reproduction or distribution permitted. Printed / viewed by: 123 a) Single sided rack and pinion b) Opposed rack and pinion c) Pin and yoke Figure A.8.5-1 — Types of elevating system Representative leg-to-hull connections are shown in Figure A.8.5-2. The basic function of the leg-to-hull connection is to transfer forces between the leg and hull as follows.  Horizontal shear is transferred by a set of horizontal forces in the lower guides and/or fixation system.  Vertical force is transferred via a set of vertical forces in the support system.  Bending moment is transferred by a combination of horizontal forces in the upper and lower guides and/or by a set of vertical forces in the support system. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 124 © ISO 2023 – All right reserved System includes:  jackcase;  fixed jacking system with opposed or unopposed jacking pinions. a) Fixed jacking system without fixation system System includes:  jackcase;  shock pads;  floating jacking system with opposed or unopposed jacking pinions. b) Floating jacking system without fixation system Figure A.8.5-2 — Representative leg-to-hull connections (1 of 2) . No further reproduction or distribution permitted. Printed / viewed by: 125 System includes:  jackcase;  jacking system with opposed or unopposed jacking pinions;  fixation system. c) Jacking system with fixation system System includes:  jackhouse;  upper and lower yokes;  upper and lower shock pads;  jacking cylinders;  jacking pins. d) Pin and yoke jacking system Key 1 upper guide reaction 2 lower guide reaction 3 pinion reactions 4 fixation system reactions 5 jacking pin reactions Fv axial force in leg at lower guide Fh shear force in leg at lower guide M bending moment in leg at lower guide Figure A.8.5-2 — Representative leg-to-hull connections (2 of 2) For jack-ups with a fixation system, the leg bending moment is shared by the upper and lower guides, the jacking system and the fixation systems. Normally, the leg bending moment and the axial force at . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 126 © ISO 2023 – All right reserved the leg-to-hull connection due to the environmental actions are transferred largely by the fixation system because of its high stiffness. Depending on the specified method of operation, the stiffnesses, the initial clearances and the magnitude of the applied forces, a portion of the environmental leg loading can also be transferred by the jacking system and the guide structures. After the fixation systems are engaged, some jack-ups release the pinions by disengaging the jacking system. Under this condition, the leg bending moment is shared by the upper and lower guides and the fixation systems. A complete typical shear force and bending moment diagram is shown in Figure A.8.5-3, with a more detailed representation shown in Figure A.8.5-4. In Figure A.8.5-4 a) to c) the part below the lower guide is independent of the leg-to-hull connection. For jack-ups without a fixation system, the leg bending moment is shared by the jacking system and guide structure. For jack-ups with a fixed jacking system, the distribution of leg moment between the jacking system and guide structure mainly depends on the stiffness of the jacking pinions. Typical shear force and bending moment diagrams for this configuration are shown in Figures A.8.5-4 b) and A.8.5-4 c). For a floating jacking system, the distribution of leg bending moment between the jacking system and guide structure depends on the combined stiffness of the shock pads and pinions. Typical shear force and bending moment diagrams for this configuration are shown in Figure A.8.5-4 d). The leg-to-hull connection should be modelled considering the effects of guide and support system clearances, wear, construction tolerances and backlash (within the gear train and between the drive pinion and the rack). . No further reproduction or distribution permitted. Printed / viewed by: 127 Key 1 lower guide 5 shear force without lower guide contact 2 fixation system lower 6 shear force with lower guide contact 3 jacking pinion 7 shear due to wave/current action 4 upper guide 8 net shear or bending moment S shear force M bending moment Figure A.8.5-3 — Complete leg shear force and bending moment — Jack-ups with a fixation system . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 128 © ISO 2023 – All right reserved a) Jack-ups with a fixation system b) Jack-ups without a fixation system and having a fixed jacking system with opposed pinions c) Jack-ups without a fixation system and having a fixed jacking system with unopposed pinions Figure A.8.5-4 — Leg shear force and bending moment within the leg-to-hull connection (1 of 2) . No further reproduction or distribution permitted. Printed / viewed by: 129 d) Jack-ups without a fixation system and having a floating jacking system Key 1 lower guide 6 shear force with lower guide contact 2 fixation system lower 7 opposed pinions 3 jacking pinion 8 jack case rigidly fixed to hull 4 upper guide 9 unopposed pinions 5 shear force without lower guide contact 10 jack case floating on shock pads S shear force M bending moment Figure A.8.5-4 — Leg shear force and bending moment within the leg-to-hull connection (2 of 2) If the jacking system has unopposed pinions, local chord moments arise due to  the horizontal pinion force component (due to the pressure angle of the rack/pinion), and  the vertical pinion force component acting at an offset from the chord neutral axis. The techniques in A.8.5.2 to A.8.5.7 are recommended for modelling leg-to-hull connections (specific data for the various parts of the structure can be available from the design data package). A.8.5.2 Guide systems The guide structures should be modelled to restrain the chord member horizontally only in directions in which guide contact occurs. The upper and lower guides can be considered to be relatively stiff with respect to the adjacent structure, such as jackcase, etc. The nominal lower guide position relative to the leg can be derived using the sum of leg penetration, water depth and hull elevation. It is, however, recommended that at least two positions be covered when assessing leg strength: one at a node and the other at midspan. This is to allow for uncertainties in the prediction of leg penetration and possible differences in penetration between the legs. The finite lengths of the guides can be included in the modelling by means of a number of discrete restraint springs/connections to the hull. Care should be taken to ensure that such restraints carry reactions only in directions/senses in which they can act. Alternatively, the results from analyses ignoring the guide length can be corrected, if necessary, by modification of the local bending moment diagram to allow for the proper distribution of guide reaction; see Figure A.8.5-5. The bending moments in the chord members at the guides determined from a finite element analysis ignoring the guide length, as in Figure A.8.5-5 a) and b), can be corrected using beam analysis for the simplified guide reactions, as shown in Figure A.8.5-5 c) and d) respectively. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 130 © ISO 2023 – All right reserved a) Guide mid-bay–- guide reaction ignoring guide length c) Guide mid-bay–- simplified distribution of the guide reaction b) Guide at node–- guide reaction ignoring guide length d) Guide at node–- simplified distribution of the guide reaction Key F guide reaction h guide length s bay height Figure A.8.5-5 — Correction of point supported guide model for finite guide length A.8.5.3 Elevating system A.8.5.3.1 Jacking (or elevating) pinions The jacking pinions should be modelled using the manufacturer specified pinion stiffness, and should be modelled so that the pinions can resist vertical and the corresponding horizontal forces. A linear spring or cantilever beam can be used to simulate the jacking pinion. The force required to deflect the free end of the cantilever beam a unit distance should be equal to the jacking pinion stiffness. The offset of the pinion/rack contact point from the chord neutral axis should be incorporated in the model. . No further reproduction or distribution permitted. Printed / viewed by: 131 A.8.5.3.2 Other elevating systems Elevating system designs not included above should be modelled using stiffness values obtained from the manufacturer/designer, by appropriate system testing or by rational analysis with due consideration of member interface gap spacing and mechanical component stiffness. A.8.5.4 Fixation system The fixation system should be modelled to resist both vertical and horizontal forces based on the stiffness of the vertical and horizontal supports and on the relative location of their associated foundations. It is important that the model reflects the local moment strength of the fixation system arising from its finite size and the number and location of the supports. A.8.5.5 Shock pad — Floating jacking systems Floating jacking systems generally have two sets of shock pads at each jackcase, one located at the top and the other at the bottom of the jackhouse. Alternatively, shock pads can be provided for each pinion or block of pinions. The jacking system is free to move up or down until it contacts the upper or lower shock pad. In the elevated configuration, the jacking system is in contact with the upper shock pad and in the transit configuration it is in contact with the lower shock pad. The stiffness of the shock pad should be based on the manufacturer's data and the shock pad should be modelled to resist vertical force only. It should also be recognized that the shock pad stiffness characteristics are normally non-linear and can change significantly over time. A.8.5.6 Jackcase and associated bracing The stiffness of the jackcase and associated bracing should be modelled accurately since it can have a direct impact on the distribution of horizontal forces between the guides and the jacking system. If the hull is not modelled, it is normally sufficient to restrain the base of the jackcase and associated bracing, as well as the foundations of the fixation system and the lower guide structures at their connections to the hull. A.8.5.7 Equivalent leg-to-hull stiffness The determination of stiffnesses for the equivalent leg-to-hull connection model can be accomplished by the following means.  The application of unit load cases to a detailed leg model in combination with a detailed leg-to-hull connection model in accordance with 8.3.2 and 8.5: Unit load cases are applied as described in A.8.3.3. The effective stiffness of the connection can be determined from the differences between the results from the detailed leg model alone (see A.8.3.3) and those from the detailed leg plus leg-to-hull connection model as follows.  Axial unit load case: This case is used to determine the vertical leg-to-hull connection stiffness, Kvh from the axial end displacements of the detailed leg model, Δ, and the axial end displacements of the combined leg and leg-to-hull connection model, ΔC, under the action of the same unit load case, F, as given in Formula (A.8.5-1): 𝐾𝐾vh=𝐹𝐹𝛥𝛥𝐶𝐶−𝛥𝛥 (A.8.5-1)  Pure moment applied either as a moment or as a couple: This case is used to derive the rotational leg-to-hull connection stiffness, Krh from either the end slopes, ΘM and ΘC, or the end deflections, 𝛿𝛿M and δC, of the two models under the action of the same end moment, M, as given in Formula (A.8.5-2): . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 132 © ISO 2023 – All right reserved 𝐾𝐾rh=𝑀𝑀/(𝜃𝜃C−𝜃𝜃M) or 𝐾𝐾rh=𝑀𝑀𝑀 /(𝛿𝛿C−𝛿𝛿M) (A.8.5-2)  Pure shear, which can be used to determine the horizontal leg-to-hull connection stiffness, Khh, in a similar manner, accounting for the rotational stiffness already derived: Normally, the horizontal leg-to-hull connection stiffness can be assumed infinite. If the model contains non-linearities, e.g. due to the inclusion of gap elements, care should be taken to ensure that suitable magnitudes of unit load cases are applied to accurately linearize the connection stiffness for the final anticipated displacement including wind actions, etc. A.8.6 Modelling the spudcan and foundation A.8.6.1 Spudcan structure When modelling the spudcan, rigid beam elements are considered sufficient to achieve an accurate transfer of the seabed reaction into the leg chords and bracing. It should be noted that, due to the sudden change in stiffness, these rigid beams can cause artificially high stresses at the leg to spudcan connections. Hence, the modelling and selection of element type should be carefully considered when an accurate calculation of leg member stresses is required in this area. For a strength analysis of the spudcan and its connections to the leg, a detailed model with appropriate boundary conditions should be developed. This analysis can be performed on an independent model of the spudcan. A.8.6.2 Seabed reaction point Unless geotechnical analyses demonstrate otherwise, the vertical position of the reaction point at each spudcan should be located at a distance above the spudcan tip equivalent to a) half the maximum predicted penetration (when spudcan is partially penetrated), or b) half the height of the spudcan (when the spudcan is fully penetrated). The legs of an independent leg jack-up can be either assumed to be pinned or supported with translational and rotational foundation springs at the reaction point. The assumed boundary conditions should be clearly stated together with the assumptions for any moment fixity provided to the spudcans by the soil. The spudcan geometry, sloping seabeds, bottom obstructions, existing spudcan footprints, etc., can result in horizontal eccentricity of the spudcan support. In such cases, the horizontal position (eccentricity) of the reaction point used in the analysis should be established through calculations that consider the spudcan geometry and seabed topology under the action of preload and should, normally, only be taken into account where this is detrimental to the assessment results. In such cases, the strength of the spudcan should also be considered. Non-symmetrical geometries should be specially considered. Further discussion on seabed reaction is contained in Clause 9. A.8.6.3 Foundation modelling Methods of establishing the degree of rotational restraint, or fixity, at the spudcans are discussed further in Clause 9 and A.9. Upper or lower values should be considered as appropriate for the areas of the structure under consideration. When it is necessary to check the spudcans, the leg-to-can connection and the lower parts of the leg, appropriate calculations should be carried out to determine the upper bound spudcan moment . No further reproduction or distribution permitted. Printed / viewed by: 133 considering soil-structure interaction. These areas can be checked by assuming that a percentage of the maximum storm leg moment at the lower guide (derived assuming a pinned spudcan) is applied to the spudcan together with the associated horizontal and vertical seabed reaction forces. This percentage should conservatively be taken as not less than 50 %. For such simplified checks, the spudcan-soil interaction can be modelled assuming that the soil is linear-elastic and incapable of taking tensile stress. For earthquake screening analyses, see A.10.7 A.8.7 Mass modelling The vertical distribution of mass is important for all dynamic analyses as it affects the lateral inertial actions. Care should be taken when modelling the hull mass to ensure that the horizontal distribution of mass is correct as it affects the yaw response. This is important particularly in fatigue and earthquake analysis. The cantilever position should be considered when distributing the mass. For earthquake assessments, see A.10.7. Normally, the correct functional actions cannot be simply obtained from a mass model of the hull and legs with the application of gravity since it is not possible to consistently account for buoyancy, marine growth, added mass, entrapped water, etc. If the mass model is used to develop the functional actions and dynamic response, then extreme care should be taken to ensure that the proper corrections are made to the functional actions. See A.8.8.2 and A.8.8.3. A.8.8 Application of actions A.8.8.1 Assessment actions The assessment follows a partial factor format. The partial action factors are applied to the actions defined in other clauses (i.e. they are action factors, not action-effect factors). The jack-up response is non-linear and, hence, the application of the combined factored actions does not in general develop the same result as the factored combination of individual action effects. The actions and action effects are discussed in turn below. A.8.8.2 Functional actions due to fixed load and variable load The actions on the hull due to fixed load and variable load should be applied to the model in such a manner as to represent their correct vertical and horizontal distribution. The hull functional actions are the hull masses multiplied by the vertical gravitational acceleration. The hull mass distribution can be represented by a combination of self-generated mass and applied point masses at the node points of the model. When redistribution of the hull weight is used to correct for hull sag moment (see A.8.8.3), the correct horizontal weight distribution can be compromised; when this is undesirable, one of the alternative approaches in A.8.8.3 should be used. The mass and weight modelling of the legs is more complex than for the hull (see A.8.7). Separate mass and functional action models should consistently account for buoyancy, marine growth, added mass, entrapped water, etc. In benign areas, the ULS environment is sometimes within the defined SLS limits for the jack-up and the assessment metocean conditions do not exceed the limits for changing to the elevated storm mode (see 5.3). In such cases, the assessment should be for the ULS environment and the proposed operating mode configurations, e.g. with increased variable load, cantilever extended and unequal leg loads. Individual leg reactions under the functional actions can approach the preload reaction. A small additional leg reaction due to environmental actions can then result in additional spudcan penetration. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 134 © ISO 2023 – All right reserved When the operations manual permits the variable load to be increased as metocean conditions reduce, the jack-up should be assessed to the ULS for operational environments and/or lower return periods (see 5.3). This is of particular importance in areas where significant additional penetrations are possible. A.8.8.3 Hull sagging When a jack-up is installed on site, the legs normally engage the seabed with the hull supported by its own buoyancy in a hogged condition. Subsequently, with the hull slightly clear of the water, preload ballast is taken on board thus preloading the legs to achieve their final penetration. This normally leads to an extreme hull sagging condition. Finally, the preload ballast is dumped and the hull elevated to the required elevation for the site. In this configuration, the hull is sagging under self-weight and variable load. The leg shear and bending moments caused by hull sagging are very dependent on leg guide clearances, the design and operation of the jacking system operational parameters, etc. Such moments should be considered in the assessment analyses, and are larger in shallow waters where the leg extension below the hull is small and consequently the leg bending stiffness is higher. An FE model with distributed hull stiffness and distributed functional actions incorporates hull sag effects if the functional actions are applied to the jack-up in its initially undeflected shape at the operating hull elevation. The hull sag moment is generally overpredicted by this modelling technique and may be reduced by up to 75 % of the value that would be obtained from an analysis using a hull model with a) the maximum extreme storm weight distributed according to A.8.8.2, b) guide clearances set to zero, and c) the elevating system loads equalized within each leg. The reduction of the hull sag moment should be achieved by one or more of the following:  applying correcting moments to the hull in the vicinity of each leg;  redistributing the hull weight, whilst maintaining the correct centre of gravity;  including realistic guide clearances; and/or  adjusting position of the spudcan reaction point (prescribed displacement). Methods that affect the stiffness of the model such as increasing the hull stiffness or increasing the conformity at the base of the legs should be avoided. If the jack-up is to be operated in an area where the assessment storm falls within its operating limits (as opposed to between operating and survival limits, see 5.3), and for all earthquake assessments, the hull sag moment should be based on the operating condition. This is found as above with the addition of the full effects due to the increase in hull weight and the revised distribution, e.g. 25 % of the initial hull sag plus 100 % of the sag due to the change to the operating condition. A.8.8.4 Metocean actions A.8.8.4.1 Wind actions Wind actions are determined from 7.3.4. The wind actions on the legs above and below the hull should be modelled to represent their correct vertical and horizontal distribution. Actions can be applied as distributed or as nodal actions. Where nodal actions are used, a sufficient number should be applied to . No further reproduction or distribution permitted. Printed / viewed by: 135 reflect the distributed nature of the actions, and it should be ensured that the correct total shear and overturning moment are achieved on each leg. Similarly, the wind actions on the hull and associated structure can be applied as distributed or as nodal actions. The application should also ensure that the correct total shear and overturning moment on the hull are achieved. A.8.8.4.2 Wave/current actions Wave/current actions are determined from 7.3.3. The wave/current actions on the leg and the spudcan structures above the sea floor should be modelled to represent their correct vertical and horizontal distribution. Where nodal actions are used, their application should ensure that the correct total shear and overturning moment are achieved on each leg, and reflect the distributed nature of the actions. A.8.8.5 Inertial actions A deterministic dynamic storm analysis requires the explicit determination of an inertial loadset, Fin (see Clause 10). This loadset should be applied to the model in combination with the other actions. For the SDOF approach, Fin is applied to the hull as lateral force(s) acting through the hull centre of gravity. When the inertial loadset is derived from a random dynamic analysis, the applied loadset should match both the inertial base shear and the inertial overturning moment. This can be accomplished by a combination of a) lateral force(s) acting on the hull, b) lateral force(s) acting equally on all the legs above the upper guide in the direction of the metocean actions, and c) correcting moment(s) applied as a horizontal or vertical couple(s) to the hull. The ratio of the total lateral forces acting on the legs above the hull to the lateral forces acting on the hull should not exceed the ratio of the mass of the legs above the upper guide to the total mass of the hull. The moment due to the lateral forces applied to the legs above the upper guide should not exceed the correcting moment required to match the overturning moment, i.e. when applying the forces in b) above, the correcting moment in c) should increase the overturning moment. Forces or moments due to inertial actions should normally be applied only to structure above the lower guide. Internal leg forces and foundation forces are both important aspects of a site-specific assessment and application of inertial actions to the legs below the lower guide directly affects these in an unrealistic manner. NOTE The application of the inertial loadset using concentrated forces can result in spurious local stresses. A.8.8.6 Large displacement effects There are two displacement effects that should be captured:  lateral displacement of the hull causes the functional actions to increase global OTM (global P-Δ effects);  Euler amplification of local member forces increases member stresses (local p-δ effects). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 136 © ISO 2023 – All right reserved The assessor should be cognisant of how specific software includes these effects. Global displacement effects are normally accounted for as described below. Euler amplification is frequently accounted for in member code checks through use of the member moment amplification factor Bmaf (see A.12.4). Some methods account for only global effects, while other methods account for both global and local effects. a) Large displacement methods: In large displacement methods, the solution is obtained by applying the load case in increments and generating the stiffness matrix for the next load case increment from the deflected shape of the previous increment, iterating on each step if necessary. This method accounts for both global displacement and Euler amplification effects such that Bmaf = 1,0 in the moment amplification formulae (see A.12.4). b) Geometric stiffness methods: Geometric stiffness methods incorporate a linear correction to the stiffness matrix based on the axial forces present in the elements. It is important that the assessor understand specifically which large displacement effects the software approximates (global and perhaps local) so that the correct value of Bmaf can be chosen for use in the moment amplification formulae (see A.12.4). c) Negative spring method: A simplified geometric stiffness approach allows linear-elastic incorporation of P-Δ effects in an FE program without recourse to iteration. In this approach, a correction term is introduced into the global stiffness matrix prior to analysis. When the analysis is complete, the hull deflections, leg axial forces and leg bending moments include the global P-Δ effects. The derivation of the method is described in ISO/TR 19905-2:2012, A.8. The correction term is −Pg /L where Pg is the sum of the leg forces due to functional actions on legs at the hull including the weight of the legs above the hull; L is the distance from the spudcan reaction point to the hull vertical centre of gravity. This negative stiffness correction term applied at the hull produces an additional lateral force at the hull proportional to the structural deflection. The resulting (additional) base overturning moment is equal to Pg times the hull displacement. The negative stiffness is incorporated into the global stiffness matrix by attaching orthogonal horizontal translational spring elements to a node(s) representing the hull centre of gravity. If sets of orthogonal springs are attached to the hull in the vicinity of each leg, using the total spring stiffness divided by the number of legs, the torsional stiffness is also corrected. If the negative spring(s) are earthed, the additional lateral force (due to the negative stiffness term) causes an overprediction of the horizontal leg reactions. Typically, this is not critical and the horizontal reactions at each leg can be reduced by an amount equal to the force in the spring divided by the number of legs. However, when non-linear foundation elements are used, the earthed-spring approach overpredicts the horizontal foundation reactions and results in erroneous foundation responses. The overprediction of the horizontal leg reactions can be avoided if sets of negative horizontal springs are defined for each leg and connected between the hull and the spudcan. . No further reproduction or distribution permitted. Printed / viewed by: 137 The application of negative springs to the model accounts for global displacement effects but does not include local Euler effects for individual members; therefore, code checks should include appropriate terms to account for amplification of local moments (see A.12.4). A.8.8.7 Conductor actions The conductor actions can be applied as static forces. The reaction due to the tension and hydrodynamic action on the conductor should be included in the jack-up's global analysis model and applied through the support point on the hull. The effects of stiffness and damping in the conductor are not generally modelled in a jack-up structural assessment because they normally have negligible influence on the global jack-up response. Structural integrity assessment of an individual conductor is outside the scope of this document. A.8.8.8 Earthquake actions See 10.7 and A.10.7 for earthquake actions. A.8.8.9 Ice actions See 10.8 and A.10.8 for ice actions. A.9 Guidance on foundations A.9.1 Applicability No guidance is offered. A.9.2 General No guidance is offered. A.9.3 Geotechnical analysis of independent leg foundations A.9.3.1 Foundation modelling and assessment A.9.3.1.1 General In 9.3.1 and A.9.3.1 are addressed the approaches to foundation modelling for  response analysis; and  foundation assessment checks. The response analysis should incorporate dynamic effects using a compatible or conservative foundation model. Dynamic effects can either be applied by means of a set of added inertial actions or be directly included in the analysis. There is a specific set of foundation assessment checks for each of the foundation models that can be selected for the response analysis, as shown in Table A.9.3-1. The foundations of independent-leg jack-ups approximate large inverted cones, commonly known as spudcans. Roughly circular in plan, spudcans typically have a shallow conical underside (in the order of 15° to 30° to the horizontal) and can have a sharp protruding point. Other spudcan geometries are not uncommon (see Figure A.9.3-1). Large jack-up spudcans can be in excess of 20 m in diameter, with shapes varying with manufacturer and jack-up. Non-circular spudcans can be approximated by means of a disc with equivalent diameter. The foundation capacity formulae given in A.9.3.2 are applicable to . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 138 © ISO 2023 – All right reserved circular spudcans. Skin friction on the legs or spudcan is often ignored. Due consideration should be given to the tapered geometry of most spudcans when assessing the foundation capacity. NOTE Symbols that are not defined in the text can be found in 4.1.5. . No further reproduction or distribution permitted. Printed / viewed by: 139 Dimensions in metres Figure A.9.3-1 — Typical spudcan geometries . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 140 © ISO 2023 – All right reserved A.9.3.1.2 Approaches to foundation assessment The jack-up and its foundation can be assessed using any of the fixity treatments in Table A.9.3-1. The overall assessment procedure of the jack-up is given in Figure A.10.4-2. There are certain cases that are not covered in the checks described above, which should be considered separately; some of the more common examples are listed below.  Cases where the long-term (drained) soil bearing capacity is less than the short-term (undrained) capacity, e.g. for overconsolidated clays or cohesive silts with significant sand seams.  Cases where a degradation of soil strength occurs due to cyclic loading. This can be of particular significance for silty soils and/or carbonate materials.  Cases where an increase in spudcan penetration occurs and a potential for punch-through exists, e.g. due to cyclic loading.  Cases where horizontal seams of weak soil are located beneath the spudcan that can result in inadequate horizontal (sliding) capacity and sliding instability. If any of the above circumstances exist, further analysis should be carried out. In the case of partial embedment of a conical spudcan, e.g. in sandy soils, after preloading, additional spudcan embedment can result in a considerable increase in foundation capacity, which can be used in the assessment checks. In some circumstances, the foundation capacities and stiffnesses are not sufficient for the unit to satisfy the acceptance criteria (Clause 13) based on the applied preload. In such cases, the assessment can be based on foundation capacities and stiffnesses calculated using soil strength parameters and partial material factor 𝛾𝛾𝑚𝑚 instead of the applied preload in accordance with the approach described in E.4. . Table A.9.3-1 — Approaches to foundation assessment Fixity treatment in response analysis Foundation assessment Acceptance category Subclause Pinned Simple preload check, Windward leg check (both are subject to limitations) Level 1; Step 1a Level 1; Step 1b A.9.3.6.2 A.9.3.6.3 Bearing and sliding checks using vertical-horizontal capacity envelope Level 2; Step 2a A.9.3.6.4 Displacement check using the vertical-horizontal capacity envelope and load-penetration curve; should also meet the Level 2; Step 2a sliding checks Level 3; Step 3a A.9.3.6.6 Fixity Simple interaction surface (secant model) Bearing and sliding checks (uses the same procedure as in Level 2; Step 2a) Level 2; Step 2b A.9.3.6.5 Displacement check using the vertical-horizontal capacity envelope and load-penetration curve; should also meet the Level 2 sliding checks Level 3; Step 3a A.9.3.6.6 Full interaction surface (yield interaction model) Foundation checks are implicit in the non-linear model; should also meet the Level 2 sliding checks unless implicitly included Level 2; Step 2c or Level 3; Step 3b A.9.3.6.5 A.9.3.6.6 Continuum Foundation checks are implicit in the non-linear model Level 3; Step 3b A.9.3.6.6 . No further reproduction or distribution permitted. Printed / viewed by: 141 A.9.3.1.3 Simple pinned foundation Pinned foundation treatment incorporates a simple preload and sliding check (both subject to limitations). Otherwise a check on foundation capacity in terms of vertical-horizontal capacity and sliding capacity should be performed. A.9.3.1.4 Linear vertical, linear horizontal and secant rotational stiffness This foundation fixity treatment incorporates a check on foundation capacity in terms of vertical-horizontal capacity and sliding capacity. The amount of rotational fixity is not directly involved in a checking formula. However, the moment, bearing and sliding interaction is implicitly checked through the use of the yield surface function. Vertical-horizontal and sliding capacities should still be checked explicitly through the procedures described in A.9.3.6. A.9.3.1.5 Non-linear vertical, horizontal and rotational stiffness The vertical, horizontal and moment interaction is implicitly checked through the use of the yield interaction model as described in A.9.3.4.2.3. No other checks are required providing that sliding is incorporated in the model. A.9.3.1.6 Non-linear continuum foundation model This model should not be used unless one of the simpler analysis methods above has been used to provide a benchmark for the results. The soil model should be capable of capturing the non-linear behaviour for the strain levels expected in the response. The interface between the spudcan and the soil should be modelled to account for effects such as sliding due to insufficient friction. A.9.3.2 Leg penetration during preloading A.9.3.2.1 Analysis method A.9.3.2.1.1 General The conventional procedure for the assessment of spudcan load/penetration behaviour is given in the following steps. a) Model the spudcan. b) Compute the gross ultimate vertical bearing capacity, QV, of an open hole for various depths of the bearing area below sea floor using closed form bearing capacity solutions for the best estimate soil strength profile. A low representative value and a high representative value of the soil strength profile should also be used to assess the implications of the range of spudcan penetrations. c) Use Formula (A.9.3-1) to convert the gross ultimate vertical bearing capacity at each depth to the available structural spudcan reaction, VL, by deducting, when appropriate, the submerged weight of the backfill, WBF, and adding the soil buoyancy of the spudcan below bearing area, BS, calculated as BS = γ'VD as described in A.9.3.2.1.5. VL = QV + BS (with no backfill) VL = QV − WBF + BS (with backfill) (A.9.3-1) See A.9.3.2.1.4. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 142 © ISO 2023 – All right reserved NOTE Formula (A.9.3-1) assumes the gross vertical bearing capacity is equal to the vertical spudcan reaction during preloading. Ultimate vertical bearing capacity can exceed preload spudcan reaction, particularly for competent soil conditions. d) Plot the available structural spudcan reaction, VL as a curve against penetration, accounting for the distance of the spudcan tip beneath the depth of the bearing area by increasing the penetration used in the capacity calculation by this distance. The curve should extend to a suitable depth beyond the expected penetration. This depth should normally be 1,5 times the expected penetration or to the penetration associated with 1,5 times the preload reaction. e) Enter the curve of available structural spudcan reaction versus spudcan penetration with the maximum preload reaction at the spudcans and read off the predicted spudcan penetration. A.9.3.2.1.2 Modelling the spudcan For conventional foundation analyses, the spudcan can often be modelled as a flat circular foundation. The equivalent diameter is determined from the area of the actual spudcan cross-section in contact with the sea floor, or where the spudcan is fully embedded, from the largest cross-sectional area in plan (see Figure A.9.3-2). Foundation analyses are then performed for this circular foundation at the greatest embedment depth, Dembed, of the maximum cross-sectional area in contact with the soil. Since the depth of spudcan penetration is normally reported and presented as the distance from the spudcan tip to the sea floor, care should be taken to use the appropriate value in the analysis and presentation of results. Conical shapes are discussed in Annex E. Other configurations, e.g. rectangular spudcans or legs with significant skin friction, can require alternative treatment. When a penetration analysis uses bearing capacity factors that account for the conical underside of the spudcan, at each depth the equivalent cone angle (β, Figure A.9.3-3 and Annex E) for the amount of spudcan penetrated should be evaluated. With reference to Figure A.9.3-3, the equivalent cone should be taken such that  the diameter, B, of the cone at its top gives an area equal to the largest plan cross-sectional area in contact with the soil,  the cone angle should be determined so as to enclose the same volume as that of the spudcan below the sea floor, and  once the largest plan area is mobilized, the volume and equivalent cone angle remain constant. . No further reproduction or distribution permitted. Printed / viewed by: 143 a) Actual spudcan — Partially embedded b) Actual spudcan — Fully embedded c) Equivalent model — Partially embedded d) Equivalent model — Fully embedded Key A effective bearing area based on cross-section taken at uppermost part of bearing area in contact with soil B effective spudcan diameter Dembed greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor FV gross vertical force acting on the soil beneath the spudcan due to the assessment load case Figure A.9.3-2 — Spudcan foundation model . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 144 © ISO 2023 – All right reserved a) Tip penetration only b) Partial penetration of main cone c) Fully seated at sea floor d) Fully seated beneath sea floor Key Bmax maximum effective spudcan diameter B effective spudcan diameter Dembed greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor β effective cone angle NOTE 1 Effective cone indicated by dashed lines. NOTE 2 Based on Martin (1994)[132]. Figure A.9.3-3 — Calculating an equivalent conical spudcan for various embedments A.9.3.2.1.3 Modelling the soil The soil beneath the spudcan fails as the foundation is loaded during preloading until equilibrium is achieved at the end of the preloading operation. Figure A.9.3-4 shows different failure mechanisms for various soil conditions, which range from conventional bearing capacity failure in uniform soils, potential punch-through for layered soils, squeezing, and combinations of all of these mechanisms. The soil model should be sufficiently accurate to represent the behaviour of spudcan and soil characteristics during preloading. An appropriate soil model should be used for layered soils to account for the effects of punch-through or squeezing, e.g. local failure of a weak layer between two stronger layers. It is mentioned that an artificial punch-through condition can be created as a result of soil consolidation occurring during pauses in leg penetration whilst the spudcan is loaded to less than full preload. Such pauses can occur during installation operations or geotechnical investigation from a jack-up prior to full preloading. The analysis methods in A.9.3.2.1.4 to A.9.3.2.6.6 address the failure mechanisms shown in Figure A.9.3-4. . No further reproduction or distribution permitted. Printed / viewed by: 145 a) Conventional bearing capacity failure: uniform soil b) Deep bearing capacity: uniform soil c) Squeezing d) Punch-through e) Punch-through (with trapped soil plug) f) Punch-through (with trapped soil plug) and squeezing Figure A.9.3-4 — Spudcan bearing failure mechanisms A.9.3.2.1.4 Backfill With reference to Figure A.9.3-5, soil backfill on top of the spudcan can result from backflow or infill. Regardless of the mechanism, this soil, a) increases penetration if it occurs during preloading, b) reduces capacity available to support downward structural loads at the spudcan if it occurs after preloading, and c) always increases the uplift resistance. Backflow is the soil that flows from beneath the spudcan, around the sides, and onto the top and is more likely to occur in clays than in sands. Backflow can occur at shallow penetrations, but is more likely to occur at deeper penetrations. In very soft clays, complete backflow is likely to occur. In firm to stiff clays and granular materials, where spudcan penetration is expected to be small, the possibility of backflow diminishes. In general, backflow due to additional penetration during elevated operations is not expected to occur. If it is predicted, the effects should be taken into account. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 146 © ISO 2023 – All right reserved Infill is the soil on top of the spudcan that results from cavity wall collapse or sediment transport, e.g. where there is a sand veneer over clay. Cavity wall collapse can occur during or after preloading; sediment transport is only of significance after preloading. Cavity wall collapse can occur slowly or suddenly. If it occurs suddenly during preloading, it can cause a rapid increase in penetration. Key 1 backflow 2 infill–- wall failure 3 infill–- sediment transport 4 region subject to infill processes 5 region subject to backflow NOTE Backfill includes backflow and infill. Figure A.9.3-5 — Backflow and infill The submerged weight of backfill (WBF,o) during preloading loads the top of the spudcan and results in additional penetration. Backfill that occurs after preload has been applied and held (WBF,A) provides additional weight on the spudcan. This backfill reduces the vertical reaction that the foundation can support to resist the overturning moment. Conversely, any subsequent backfill increases the available uplift capacity of the windward leg(s). The minimum value of the backfill weight due to backflow during preloading, WBF,omin, depends on the limiting depth of cavity, Hcav, that remains open above the spudcan during penetration as given in Formula (A.9.3-2): 𝑊𝑊BF,omin=𝛾𝛾′􀵣𝐴𝐴(𝐷𝐷embed−𝐻𝐻cav)−􀵫𝑉𝑉spud−𝑉𝑉𝐷𝐷􀵯􀵧 (with backflow, i.e. WBF,omin always positive) BF,omin0W= (with no backfill) (A.9.3-2) where Vspud is the total volume of the spudcan beneath the backfill; VD is the volume of the spudcan below the maximum bearing area that is penetrated into the soil, refer to Figure A.9.3-6; VD is zero for a flat-based spudcan. . No further reproduction or distribution permitted. Printed / viewed by: 147 Care should be taken when calculating Vspud when the spudcan is not fully covered with backflow material; refer to Figure A.9.3-6. Key A partial spudcan penetration B full spudcan penetration with partial backfill, WBF,o during penetration C full spudcan penetration with full backfill, , WBF,o during penetration 1 the total volume of the spudcan below the backfill, Vspud 2 the volume of the spudcan below the maximum bearing area that is penetrated into the soil, VD 3 depth of cavity that remains open above spudcan, Hcav 4 greatest embedment depth, Dembed, of maximum cross-sectional spudcan bearing area below the sea floor Figure A.9.3-6 — Definition of spudcan volumes For a single-layer clay with uniform shear strength or shear strength increasing with depth at a rate, ρ, Formula (A.9.3-3) from Hossain and Randolph (2009a)[94] can be used to estimate Hcav. This expression and the supporting data are graphically presented in Figure A.9.3-7. Formula (A.9.3-4) from Hossain and Randolph (2009a)[94] can be used to estimate Hcav for multi-layer clays with moderate changes of strength, iterating to establish consistent values for Hcav/B and suH. 0,55cav0,25/HBSS=− (A.9.3-3) 0,55cavuHuH0,25/[/()][/()]HBsBsBγγ′′=− (A.9.3-4) where 1umsSBργγ−′=′ (A.9.3-5) suH is the undrained shear strength at a depth of Hcav below sea floor; sum is the undrained shear strength at the sea floor. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 148 © ISO 2023 – All right reserved The onset of backflow marks the transition between shallow and localized failure mechanisms. In addition to affecting the vertical reaction beneath the spudcan during preloading, the degree of backflow influences the embedment condition of the spudcan and, hence, the uplift resistance (see A.9.4.5), horizontal and moment restraint and, therefore, the yield surface (see A.9.3.3.3). In silica sand, it is unusual for a conical spudcan to penetrate beyond its widest point. However, if this is predicted, the potential for soil infilling on top of the spudcan should be considered during preloading (as the soil assumes its angle of repose). a) Experimental data and curve-fit b) Idealized scenario Key 1 spudcan 2 leg truss 3 cavity 4 sea floor 5 soil backflow B effective spudcan diameter (typically 11 m to 20 m) Dembed greatest depth of embedment of maximum cross-section in contact with the soil Hcav limiting depth of cavity that remains open above the spudcan during penetration suH undrained shear strength at base of cavity sum undrained shear strength at sea floor su0 undrained shear strength at depth of maximum spudcan bearing area su undrained shear strength Z depth below sea floor γ' submerged unit weight of soil ρsu rate of increase in undrained shear strength with depth a Centrifuge test data. b Large deformation FE analyses: non-uniform strength. c Large deformation FE analyses: uniform strength. d Typical design range. Figure A.9.3-7 — Estimation of limiting cavity depth, Hcav, due to backflow during installation . No further reproduction or distribution permitted. Printed / viewed by: 149 A.9.3.2.1.5 Required bearing capacity At maximum preload, the initial gross ultimate bearing capacity, QVo, under the spudcan is equal to the preload reaction, VLo, plus the submerged weight of any backfill onto the spudcan, less the soil buoyancy of the spudcan below the bearing area as given in Formula (A.9.3-6): VoLoBF,oSQVWB=+− (A.9.3-6) where WBF,o is the submerged weight of the overburden on top of the spudcan from backfill during preloading, which is not less than WBF,omin; BS = γ′ VD is the soil buoyancy of spudcan below bearing area, i.e. the submerged weight of soil displaced by the spudcan below Dembed, the greatest depth of embedment of the maximum cross-sectional spudcan bearing area below the sea floor; VD is the volume of the spudcan below the lowest level of maximum bearing area that is penetrated into the soil; VD is zero for a flat-based spudcan. The initial gross ultimate vertical bearing capacity, QVo, is established by preload operations and related to VLo. However, in some cases, subsequent actions can cause further penetration and a corresponding increase in QV, as is consistent with the load-penetration formulae given in A.9.3.2.2 through A.9.3.2.6. A.9.3.2.2 Penetration in clays The gross ultimate vertical bearing capacity of a foundation in clay of uniform shear strength (undrained failure in clay, φ = 0°) at a specific depth can be expressed as given in Formula (A.9.3-7): 𝑄𝑄𝑉𝑉___________=(𝑠𝑠𝑢𝑢𝑁𝑁𝑐𝑐𝑠𝑠𝑐𝑐𝑑𝑑𝑐𝑐+𝑝𝑝 o′)π𝐵𝐵2/4 (A.9.3-7) where p′o is the effective overburden pressure at the greatest embedment depth, Dembed, of the maximum bearing area; dc is the bearing capacity depth factor, dc = 1 + 0,2 (Dembed /B) ≤ 1,5. For circular footings, the product Nc·sc should be taken as 6,0. For the selection of the design undrained shear strength su, an evaluation should be made of the sampling method, the laboratory test type and the field experience regarding the prediction and observations of spudcan penetrations. Traditionally, the value of Nc has been determined from solutions for strip footing on homogeneous clay, with shape and depth factors based on Skempton (1951)[169]. However, these factors are significantly affected by the gradient of shear strength with depth [see Young et al. (1984)[212] and Houlsby and Martin (2003)[99]]. Theoretical solutions for circular conical foundations on clays of uniform and increasing strength with depth have been provided by Houlsby and Martin (2003)[99], as presented in E.1. The solutions give a theoretical lower bound to the soil resistance and should, therefore, provide an upper bound prediction of penetration. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 150 © ISO 2023 – All right reserved The total bearing capacity factors for rough spudcans, modelled as rough circular plates, are given in Table A.9.3-2. Further bearing capacity factors are given in E.1 for the following parameter ranges (see Figures A.9.3-2, A.9.3-3 and A.9.3-7):  cone angles β between 60° and a flat plate of 180°;  embedment depths, Dembed, between 0 and 2,5B;  values of shear strength gradient ρsuB/sum between 0 and 5, where ρsu is the rate of increase in undrained shear strength with depth, from a value of sum at the sea floor. NOTE For soil layers that do not extend to the sea floor surface, sum refers to the undrained shear strength at the top of the layer. The tables in Annex E provide a theoretical lower bound to the total bearing factor Nc·sc·dc to apply to the shear strength at the spudcan base level, suo, for the full range of the above parameters. Alternatively, Houlsby and Martin (2003)[99] indicates that using the shear strength, su, at a depth of 0,09B below the spudcan base level together with the bearing factors given in Table A.9.3-2 for a foundation on uniform strength clay provides answers that are within ± 12 % of the theoretical lower bound solutions. Alternatively, field experience in the Gulf of Mexico (Young, 1984)[212] indicates that for typical Gulf of Mexico shear strength gradients and spudcan dimensions, spudcan penetrations in clay are well predicted by selecting su as the average over a depth of B/2 below the widest cross-section in combination with the bearing capacity and simplified depth factor formula from Skempton (1951)[169] provided in Formula (A.9.3-7). A comparison was made Menzies and Roper (2008)[138] between measured load-penetration records from thirteen Gulf of Mexico clay sites with linearly increasing shear strength profiles and spudcan penetration predictions from four bearing capacity formulations, namely Skempton (1951)[169], Hansen (1970)[88], Houlsby and Martin (2003)[99] and Hossain et al. (2006)[93]. The comparisons indicate that the Houlsby and Martin method provides a good lower bound load-penetration prediction indicating deeper penetrations, the Hossain et al. method provides an upper bound load-penetration prediction, usually predicting shallower penetrations than measured, and the Skempton and Hanson bearing capacity factors provide reasonable predictions of average penetrations. The Hossain et al. (2006)[93] bearing capacity method was modified (Hossain et al. 2009)[96] to provide a load-penetration prediction method that accounts for soil strain rate dependency and strain softening during spudcan penetration. Hossain et al. (2014)[97] compared load-penetration results from the modified bearing capacity model with data from Menzies & Roper (2008)[138] and found good agreement. Some jack-up rigs with more than 3 legs are able to apply the pre-drive in minutes; conventional water ballast preload operations take hours or days to complete. The bearing capacity when pre-driving should utilize bearing capacity methods that allow for changes in the shear strength due to strain rate effects. Research performed by Hossain and Randolph (2009c)[96] developed a bearing capacity model that includes the effect of strain rate dependency to predict load-penetration. A discussion of strain rate effects on the prediction of load-penetration is also presented in Versteele et al. (2017)[195]. For clay layers with distinct strength differences, methods for layered soils should be used; see A.9.3.2.6. . No further reproduction or distribution permitted. Printed / viewed by: 151 Table A.9.3-2 — Bearing capacity factors for rough circular plate on homogeneous clay (Houlsby and Martin, 2003[99]) Embedment ratio, Dembed/B Bearing factor, Nc·sc·dc 0 6,0 0,1 6,3 0,25 6,6 0,5 7,0 1,0 7,7 ≥ 2,5 9,0 The bearing factor is nonlinear with respect to the embedment ratio. It is necessary to use caution when estimating an appropriate bearing factor for embedment ratios other than those given in Table A.9.3-2. A.9.3.2.3 Penetration in soils with partial drainage It is recommended that analyses for drained conditions (modelled as sand) and undrained conditions (modelled as clay) be performed to estimate the range of penetrations. Partial drainage conditions and penetration in soils can be assessed using the approaches described by Finnie and Randolph (1994b)[72] and Erbrich (2005)[70]; the latter reference also describes the use of cyclic preloading in silts. A.9.3.2.4 Penetration in silica sands Spudcan penetration in silica sand is usually analysed as a drained process, in which no excess pore water pressure is generated. In drained conditions, the gross ultimate vertical bearing capacity of a circular foundation in homogeneous frictional material can be expressed as given in Formula (A.9.3-8): 𝑄𝑄𝑉𝑉=𝛾𝛾′𝑑𝑑𝛾𝛾𝑁𝑁𝛾𝛾π𝐵𝐵38+𝑝𝑝𝑜𝑜′ 𝑑𝑑𝑞𝑞𝑁𝑁𝑞𝑞π𝐵𝐵24 (A.9.3-8) where dγ is the depth factor on self weight for drained soils, dγ = 1,0; dq is the depth factor on surcharge for drained soils, dq = 1 + 2tanϕ′ (1-sinϕ′)2 arctan(Dembed/B) where arctan(Dembed/B) is in radians and ϕ′is the effective angle of internal friction for sand in degrees; B is the effective spudcan diameter in contact with the soil; γ ′ is the submerged unit weight of the soil; Nγ and Nq are dimensionless bearing capacity factors calculated for the axisymmetric case (no further shape factor should be applied). If the spudcan penetrates beyond its widest point, the overburden of soil above this point creates an effective surcharge, po′, at the level of the widest point, which leads to additional bearing capacity. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 152 © ISO 2023 – All right reserved Theoretical values of Nγ and Nq calculated using the slip-line method for a flat, rough circular footing in Martin (2003)[133] are given in Table A.9.3-3 for soil friction angles from 20° to 40°. These Nγ and Nq factors can also be applied to (blunt) conical spudcans that are not fully rough, since the error involved is generally small compared with that arising from the uncertainty in selecting the soil friction angle; for example, Table A.9.3-3 shows that a 1° change in ϕ′ gives at least a 20 % change in Nγ A more detailed penetration analysis can be performed using the values of Nγ for conical footings tabulated in Annex E; these cover a range of cone apex angles and interface roughness coefficients. Adequate consideration should be given to the selection of an appropriate soil friction angle (see E.2). Table A.9.3-3 — Bearing capacity factors for a flat, rough circular footing (Martin, 2003)[133] Friction angle ϕ′ Degrees Bearing factor Nγ Bearing factor Nq 20 2,4 9,6 21 2,9 10,9 22 3,5 12,4 23 4,2 14,1 24 5,1 16,1 25 6,1 18,4 26 7,3 21,1 27 8,8 24,2 28 10,6 27,9 29 12,8 32,2 30 15,5 37,2 31 18,8 43,2 32 22,9 50,3 33 27,9 58,7 34 34,1 68,7 35 41,9 80,8 36 51,6 95,4 37 63,7 113,0 38 79,1 134,4 39 98,7 160,5 40 123,7 192,7 A.9.3.2.5 Penetration in carbonate sands A.9.3.2.5.1 General Penetrations in carbonate sands are highly unpredictable and can be minimal in strongly cemented materials, or large, in uncemented materials. Cementation, crushable particles, high in situ void ratios and compressibility are some of the characteristics of calcareous sediment that have led to the conclusion that the routine bearing capacity methods linked to the frictional soil strength are inappropriate [Poulos and Chua (1985)[148], Le Tirant and Nauroy (1994)[121] and Finnie and Randolph (1994a)[72]]. Extreme care should be exercised when operating in these materials. . No further reproduction or distribution permitted. Printed / viewed by: 153 A.9.3.2.5.2 Uncemented carbonate materials Relatively large spudcan penetrations have been reported for uncemented carbonate materials despite high laboratory friction angles [Dutt and Ingram (1988)[66]]. This can be attributed to either the high compressibility of these materials or low shear strengths due to high voids ratio and a collapsible structure. The leg penetration is governed by both the strength and deformation characteristics of the soils. The compressibility of carbonate sands is relatively higher than that of silica sands. Hence, greater penetrations should be expected for carbonate sands relative to silica sands despite the similar or even higher laboratory friction angles. This is supported by both experimental studies [Poulos and Chua (1985)[148], Pan (1999)[144], Pan et al. (1999)[145], and Byrne and Houlsby (2001)[39]] and theoretical studies [Yeung and Carter, (1989)[209]] on model foundations. A.9.3.2.5.3 Cemented carbonate materials Natural cementation in calcareous sediments is formed by carbonate precipitation. Model spudcan experiments on artificially cemented calcareous soils have shown that the pure vertical bearing response of circular foundations can also be described as bi-linear, with a yield point that is similar to the yield stress in 1-dimensional compression [Poulos and Chua (1985)[148], Houlsby et al. (1988)[100], Sharp and van Seters (1988)[166], and Randolph and Erbrich (1999)[153]]. The bearing resistance then increases with continuing displacements, with no clear failure point. This behaviour is consistent with local or punching shear failure. Randolph and Erbrich (1999) [153] explain this bi-linear shape as being attributable to the very small settlement expected before the yield pressure is exceeded. A.9.3.2.5.4 Predictive methods The predictions of spudcan penetrations in carbonate sands are likely to be less accurate than those for silica sands because carbonate sands generally have high porosity and a varying degree of cementation. Spudcan penetration occurs due to a combination of soil compression and soil failure. The use of the conventional general shear failure model for sand for predicting the penetration is, therefore, not appropriate. This model is, however, generally adopted for penetration predictions in carbonate sands but requires a careful assessment of the friction angle. The reduction of the friction angles is typically in the range of 3° to 7° for cemented and uncemented carbonate sands. Special attention is required for sites with a stronger cemented soil layer overlying weak, uncemented layers with careful consideration given to the type of punch-through mechanism. Randolph et al. (1993)[154] and Finnie and Randolph (1994a)[71] outline a bearing modulus method for uncemented calcareous sands. This is based on the results of a series of centrifuge experiments of model footings that indicate that the vertical bearing capacity increased linearly with depth. An estimation of the bearing pressure can be performed as a function of the overburden pressure rather than the self-weight as given in Formula (A.9.3-9): uqqzNγ′= (A.9.3-9) where z is the penetration and Nq is the bearing capacity factor. Whilst Nq ≈ 50 was found to provide reasonable predictions of the centrifuge test data, it can overpredict the foundation bearing capacity of spudcans in uncemented carbonate soils. Formula (A.9.3-9) can be adapted to calculate the vertical bearing capacity for a conical spudcan by sub-dividing the spudcan geometry vertically into a number of equivalent circular footings as shown in Figure A.9.3-8. The bearing capacity of the area at the base of each slice in contact with the soil can be summed to calculate iteratively the overall bearing capacity of the conical footing for different footing penetrations. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 154 © ISO 2023 – All right reserved Figure A.9.3-8 — Representation of a conical spudcan by equivalent circular footing “slices” for the calculation of vertical bearing capacity in carbonate sands Other predictive methods for circular spudcans on both cemented and uncemented calcareous sands have been published, including Islam (1999)[107], Islam et al. (2001)[109], Houlsby et al. (1988)[100], Randolph et al. (1993)[154], Finnie and Randolph (1994a)[71], and Yamamoto et al. (2008) [207], (2009)[208]. In concluding that the bearing response of shallow foundations on calcareous sands is better modelled with a compressional deformation mechanism and the punching shear pattern, Yamamoto et al. (2008[207], 2009 [208]) provide simple formulae for the response of shallow footings on compressible sands. A.9.3.2.6 Penetration in layered soils A.9.3.2.6.1 General Three different foundation failure mechanisms should be considered when making spudcan predictions in layered soils: a) general shear; b) squeezing; c) punch-through. The first failure mechanism occurs if soil strengths of subsequent layers do not vary significantly. Thus, an average soil strength (either su or φ' ) can be determined below the spudcan. The spudcan penetration versus foundation capacity relationship is then generated using criteria from A.9.3.2.2 to A.9.3.2.5. Criteria for the other two failure mechanisms (squeezing and punch-through) are given in A.9.3.2.6.2 to A.9.3.2.6.6. Punch-through is of particular significance since it concerns a potentially dangerous situation where a strong layer overlies a weak layer and, hence, a small additional spudcan penetration can be associated with a significant reduction in vertical bearing capacity that results in rapid leg penetration. Backflow and infill should be considered. A.9.3.2.6.2 Squeezing of clay Squeezing failure of a soft clay layer overlying a significantly stronger layer (see Figure A.9.3-4 and Figure A.9.3-9) occurs when the thickness of the soft clay beneath the spudcan is less than that required for the general bearing capacity failure mode to apply. In such cases the soft layer squeezes and the vertical foundation capacity is greater than the vertical foundation capacity given by general failure in the soft clay layer, but less than the vertical foundation capacity given by general failure in the underlying significantly stronger layer. . No further reproduction or distribution permitted. Printed / viewed by: 155 The gross ultimate vertical bearing capacity of a spudcan on a clay layer undergoing squeezing failure can be analysed by methods given by Brown and Meyerhof (1969)[35] and by Vesic (1975)[196] in combination with the bearing capacity and depth factors given by Skempton (1951)[169] as given in Formula (A.9.3-10). 𝑄𝑄𝑣𝑣 = 𝐴𝐴 􀵜􀵬𝑎𝑎𝑠𝑠+ 𝑏𝑏𝑠𝑠𝐵𝐵𝑇𝑇 + 1,2𝐷𝐷embed𝐵𝐵􀵰 𝑠𝑠𝑢𝑢 + 𝑝𝑝𝑜𝑜′ 􀵠 ≥ 𝐴𝐴{𝑁𝑁𝑐𝑐 𝑠𝑠𝑐𝑐 𝑑𝑑𝑐𝑐 𝑠𝑠𝑢𝑢 + 𝑝𝑝𝑜𝑜′ } (A.9.3-10) where the following squeezing factor constants are recommended: as = 5 bs = 1/3 and su is the undrained shear strength of the soft clay layer. Key 1 spudcan with effective bearing area, A 2 softer clay layer with shear strength, su 3 stronger soil 4 no backflow and no infill (i.e. no backfill) B effective spudcan diameter Dembed embedment depth of spudcan effective bearing area, A, below sea floor VL available spudcan reaction; see Formula (A.9.3-1) p′o effective overburden pressure at depth, Dembed T thickness of weaker clay layer beneath the spudcan effective bearing area Figure A.9.3-9 — Spudcan bearing capacity analysis — Squeezing clay layer The squeezing vertical foundation capacity given by Formula (A.9.3-10) should be limited such that it does not exceed the ultimate bearing capacity of the underlying strong soil layer (for T << B). Note that as T increases Formula (A.9.3-10) can give a value of QV that is less than the corresponding value for the general shear bearing capacity in the soft clay layer. In such cases, QV should be taken as the latter. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 156 © ISO 2023 – All right reserved Re-arranging Formula (A.9.3-10) using scNc = 6,0 for the bearing capacity factor at the surface in combination with the expression for the depth factor, dc, given in A.9.3.2.2 indicates that squeezing failure will occur if T ≤ B/3, subject to Dembed/B ≤ 2,5. A.9.3.2.6.3 Punch-through: two clay layers The gross ultimate vertical bearing capacity of a spudcan on the surface of a strong clay layer overlying a weak clay layer can be computed according to Brown and Meyerhof (1969)[35] as given in Formula (A.9.3-11); (see Figure A.9.3-10): Vu,tccu,occcu,to31 + 0,2b[()]()HDHQAsNsspANsdspBB+′′=++≤+ (A.9.3-11) Formula (A.9.3-11) applies to clay layers of uniform undrained shear strengths. Key 1 spudcan with effective bearing area, A 2 stronger clay layer with shear strength, su,t 3 weaker clay layer with shear strength, su,b 4 no backflow and no infill (i.e. no backfill) B effective spudcan diameter Dembed Embedment depth of spudcan effective bearing area, A, below sea floor VL available spudcan reaction; see Formula (A.9.3-1) p′o effective overburden pressure at embedment depth, Dembed H thickness of stronger clay layer beneath the spudcan effective bearing area Figure A.9.3-10 — Spudcan bearing capacity analysis — Two clay layers A.9.3.2.6.4 Punch-through — Sand overlying clay The gross ultimate vertical bearing capacity of a spudcan on a sand layer overlying a weak clay layer can be computed using a load spread model (see Figure A.9.3-11). In this model, the bearing capacity of the spudcan, QV, is calculated by considering a fictitious footing at the interface between the sand and clay layers. Be aware that this is a convenient method for expressing the bearing capacity of the spudcan within the layered soil profile and is not a representation of the actual “punching shear” failure mechanism. . No further reproduction or distribution permitted. Printed / viewed by: 157 The fictitious footing has an equivalent diameter is as given in Formula (A.9.3-12): B′ = B + 2H/ns (A.9.3-12) For sand overlying clay, a load spread factor, ns, of 3 (see Figure A.9.3-11) has been recommended by Young and Focht (1981)[211] for jack-up foundations. However, comparison with model test data [Jacobsen et al. (1977)[110], Higham (1984)[92], and Craig and Chua (1990a)[50]] suggests a range of ns from 3 to 5. Conversely, actual spudcan penetration data are available that suggest smaller ns values (Baglioni, 1982)[21]. It is, therefore, recommended that load spread factors in the range of 3 to 5 be used, consistent with current industry practice. The calculation of the bearing capacity of the fictitious footing should include consideration of the weight of the sand, W, above the fictitious footing at the surface of the lower (clay) layer, based on the assumption of an open cavity being present above the footing, as given in Formula (A.9.3-13): 𝑊𝑊=0,25π􀵣𝐵𝐵′2(𝐷𝐷embed+𝐻𝐻)−𝐵𝐵2𝐷𝐷embed􀵧𝛾𝛾′ (A.9.3-13) The total capacity is, therefore, as given in Formula (A.9.3-14): QV = Qu,b − W (A.9.3-14) where Qu,b is the ultimate vertical foundation bearing capacity for the fictitious footing at the interface between the sand and clay layers with no backfill, which can be calculated using Formula (A.9.3-7). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 158 © ISO 2023 – All right reserved Key 1 spudcan with effective diameter, B 2 sand layer with submerged unit weight of γ′ 3 clay layer 4 void above spudcan, i.e. no backflow and no infill (i.e. no backfill) 5 fictitious spudcan with effective diameter, B′, at the interface between the upper and lower layers Dembed embedment depth of actual spudcan below the sea floor VL available spudcan reaction; see Formula (A.9.3-1) H distance from spudcan to clay layer below ns load spread factor for sand overlying clay (typically 3 to 5) p′o effective overburden pressure at depth Dembed Figure A.9.3-11 — Spudcan bearing capacity analysis — Sand over clay Alternatively, the gross ultimate initial bearing capacity may be calculated using Formula (A.9.3-15) derived from Hanna and Meyerhof (1980)[86]: 𝑄𝑄V= 𝑄𝑄u,b−𝐴𝐴𝐴 𝛾𝛾′+2𝐴𝐴𝐴 (𝐻𝐻𝛾𝛾′+2𝑝𝑝𝑜𝑜′ ) 𝐾𝐾stan(𝜑𝜑)𝐵𝐵 (A.9.3-15) where Qu,b is determined according to A.9.3.2.2, assuming that the spudcan bears on the surface of the lower clay layer with no backfill. The punching shear coefficient, Ks, depends on the strength of both the sand layer and the clay layer, which can be derived from the graphs in the reference paper, Hanna and Meyerhof (1980)[86]; see Figure A.9.3-12. The bearing capacity for Qclay / Qsand ratios less than 0,1 may be calculated using the methods described in either A.9.3.2.6.4 or E.3. . No further reproduction or distribution permitted. Printed / viewed by: 159 Key 1 φ′ = 40° 2 φ′ = 35° 3 φ′ = 30° 4 φ′ = 25° KS coefficient of punching shear Qclay bearing capacity of clay for a surface strip footing of width equal to the spudcan diameter, B Qsand bearing capacity of sand for a surface strip footing of width equal to the spudcan diameter, B φ′ effective angle of internal friction for sand in degrees Figure A.9.3-12 — Bearing capacity ratio versus coefficient of punching shear for spudcans An approach based on a centrifuge study has been proposed by Teh et al. (2010)[184]. The load-penetration curve typical of the punch-through condition is represented by a simplified profile consisting of three bearing capacities, namely bearing capacity at sea floor, Q0 (at d = 0), maximum bearing capacity, Qpeak (at d = dcrit), and bearing capacity in the underlying clay (for d ≥ H). A brief description of the approach is provided in E.3. A.9.3.2.6.5 Punch-through — Cemented crust over weak soil The occurrence of a cemented crust overlying a weak layer of clay or loose sand/silt should be carefully considered. The analysis relies on accurate information on the thickness and strength of the crust and the strength of the underlying layer. The analysis can be performed using simplified load spread models or advanced numerical models. The potential for punch-through can be significantly affected by the shape of the spudcan and its tip. A.9.3.2.6.6 Three layered systems The gross ultimate vertical bearing capacity of a spudcan at the top of a three soil layer system can be computed using the squeezing and punch-through criteria for two layer systems. Firstly, the bearing capacity of a spudcan with diameter B at the top of the lower two layers (layers 2 and 3 in Figure A.9.3- . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 160 © ISO 2023 – All right reserved 13) is computed. These two layers can then be treated as one (lower) layer in a subsequent two layer system analysis involving the upper layer (layer 1 in Figure A.9.3-13). Analysis for the top layer can incorporate load spread effects. a) Analysis 1 — Layer 2 over layer 3 b) Analysis 2 — Layer 1 over layers (2 and 3) Key 1 layer 1 2 layer 2 3 layer 3 VL available spudcan reaction see Formula (A.9.3-1) Figure A.9.3-13 — Spudcan bearing capacity analysis — Three-layer case A.9.3.3 Yield interaction A.9.3.3.1 General During preloading, the soil beneath the spudcan fails plastically and the spudcan penetrates until the bearing capacity is in equilibrium with the preload reaction. When the preload is removed, the soil unloads on the small strain unload-reload stiffness curve. The spudcan geometry and the soil properties at the penetrated position are then used to determine the maximum moment and horizontal capacities that, with the vertical capacity, are the principal values that define the size of the yield interaction surface. The limiting combinations of the spudcan moment, vertical and horizontal reactions are defined by the yield interaction surface; see Figure A.9.3-14. Inside the yield surface the foundation behaviour is considered to be elastic for small strains, but it becomes increasingly inelastic as the yield surface is approached. On the yield surface, the foundation undergoes inelastic deformation with increased reaction beneath the spudcan. Provided the jack-up's preload capacity is appropriate for a site's environmental conditions, the majority of the foundation load-deflection behaviour during a storm should be essentially elastic and only a few, if any, extreme events cause stiffness reduction. When the foundation is considered as pinned, the yield surface degenerates to a vertical-horizontal load space. A.9.3.3.2 to A.9.3.6.7 are generally applicable to spudcan foundation assessment. In some circumstances, the foundation capacities and stiffnesses are not sufficient for the unit to pass the acceptance criteria based on the applied preload. In such cases, the assessment may, where applicable, be based on the foundation capacities and stiffnesses calculated based on soil strength parameters instead of the applied preload in accordance with the approach described in E.4. In such assessments the guidance in these sections should be supplemented by the guidance in E.4. Additional guidance on spudcans fitted with skirts is provided in A.9.4.1. . No further reproduction or distribution permitted. Printed / viewed by: 161 The modelling approach to the interaction of vertical, horizontal and rotational forces on the spudcan was initially developed for shallow foundations based on a plasticity relationship; see Dean et al. (1995)[56], Cassidy et al. (2006)[47], Wong and Murff (1994)[204], Baerheim (1993)[22] and van Langen and Hospers (1993)[193]. The plasticity relationship can account for moment softening at high loading levels, unloading behaviour and work-hardening effects. The shape of the yield surface for shallow foundations is paraboloidal. In clay, a deeply embedded spudcan can achieve a greater moment capacity than a spudcan with a shallow penetration [see Templeton et al. (2003)[189], (2005)[190] and Templeton (2006)[185]]. In addition, the shape of the yield surface changes from paraboloidal to becoming progressively more ellipsoidal with increasing penetration. This was first shown experimentally by Martin and Houlsby (2000)[134], further substantiated via numerical analysis by Martin and Houlsby (2001)[135] and confirmed via finite element analysis by Templeton et al. (2005)[189]. This effect can be taken into account by interpolating between the paraboloidal shape of the shallow embedment yield surface [obtained by setting a = 0 in Formula (A.9.3-16)] and the ellipsoidal shape for deep embedments (Dembed > 2,5B) using the depth interpolation parameter, a. Accomplishment of the necessary interpolation via a single parameter linear variation of the coefficients was shown to be sufficiently accurate by Templeton (2006)[185]. This model does not include sliding; where sliding is important, this should be incorporated separately using the method described in A.9.3.5. There is currently no existing data that can be used to justify increases of horizontal and moment capacity, or change of yield surface shape, for deeply embedded spudcans in sand. The application of the yield surface calibrated to shallow penetrations is likely to be conservative for the deep penetration case. In the yield formula, the gross ultimate vertical bearing capacity, QV, is initially established by preload operations and related to vLo as specified by Formula (A.9.3-6). However, in some cases, subsequent environmental actions can cause further penetration and a corresponding increase in QV, as is consistent with the load-penetration formulae given in A.9.3.2.2 through A.9.3.2.6. In assessment analyses that incorporate work hardening, such possible increases in QV can be included automatically. In other types of analyses, the effects of such increases in QV can be included via calculations using the load-penetration formulae, together with values of any additional penetration. In either case, care should be taken to include all contributions from P-Δ effects associated with leaning due to the additional penetration. The forces FH and FV and the moment FM acting on the spudcan are the forces transferred to the foundation by the jack-up in operational, extreme storm or earthquake conditions due to the assessment load case Fd in 8.8. They include quasi-static contributions due to factored actions, and contributions from dynamic response, as appropriate, in accordance with the procedures of Clause 10.  FH is the horizontal force applied to the spudcan due to the assessment load case Fd (see 8.8).  FV is the gross vertical force acting on the soil beneath the spudcan due to the assessment load case Fd (see 8.8).  FM is the moment applied to the spudcan due to the assessment load case Fd (see 8.8). If a force combination (FV,FH,FM) satisfies Formula (A.9.3-16) for the interaction yield surface, then this combination lies on the yield surface. The force combination (FV,FH,FM) lies outside the yield surface if the left-hand side of Formula (A.9.3-16) is greater than zero. Conversely, the force combination lies inside the yield surface if the left-hand side is less than zero. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 162 © ISO 2023 – All right reserved a) H-V slice when M = 0,0 b) M-V slice when H = 0,0 c) H-M slice when V = V1 Key H horizontal capacity M moment capacity V vertical capacity Figure A.9.3-14 — Three slices through the three-dimensional yield surface (at M = 0,0; H = 0,0; and V = V1 constant) A.9.3.3.2 Ultimate vertical/horizontal/rotational capacity interaction function for spudcans in sand and clay The general formula, Formula (A.9.3-16), from Templeton (2006)[185] can be used for fully or partially penetrated spudcans: 2222VVVVHMHMVVVV1611410()FFFFFFaaQQQQQQ+−−−−−= (A.9.3-16) where, for the vertical direction: QV is the gross ultimate vertical bearing capacity of the soil beneath the spudcan. Where the spudcans are to be founded in clay soils, this capacity should be calculated considering the effects of cyclic loading, as described in A.9.3.3.7. In the absence of additional penetration, the gross ultimate vertical bearing capacity, QV , is equal to the sum of the net vertical bearing . No further reproduction or distribution permitted. Printed / viewed by: 163 capacity achieved during preloading, QVnet, multiplied by the cyclic degradation factor, fcy,V, and the overburden component, per Formula (A.9.3-18). QH is the ultimate horizontal bearing capacity of the soil beneath the spudcan. Where the spudcans are to be founded in clay soils, this capacity should be calculated incorporating the effects of cyclic loading, as described in A.9.3.3.7; QM is the ultimate moment bearing capacity of the soil beneath the spudcan. Where the spudcans are to be founded in clay soils, this capacity should be calculated incorporating the effects of cyclic loading, as described in A.9.3.3.7; FV is the gross vertical force acting on the soil beneath the spudcan due to the assessment load case, Fd (see 8.8) as given in Formula (A.9.3-17): FV = Vst − BS (with no backfill) FV = Vst + WBF,o + WBF,A − BS (with backfill) (A.9.3-17) Vst is the vertical force applied to the spudcan due to the assessment load case, Fd (see 8.8), which includes quasi-static contributions due to factored actions and contributions from dynamic response, as appropriate, in accordance with the procedures of Clause 10, and also includes leg weight and water buoyancy but excludes the submerged weight of backfill (WBF,o + WBF,A) and spudcan soil buoyancy (BS); where, for the horizontal direction and moment, FH is the horizontal force applied to the spudcan due to the assessment load case, Fd (see 8.8); FM is the bending moment applied to the spudcan due to the assessment load case, Fd (see 8.8). a) The clay formulation is given in Formulae (A.9.3-18) to (A.9.3-20) [variables for sand can be found in b)]. The vertical, horizontal and moment capacities QV, QH and QM are calculated in accordance with Formula (A.9.3-18), (A.9.3-19) and (A.9.3-20), respectively. QV = ( fcy,V QVnet ) + (p’o π B2/4) (see A.9.3.3.7) (A.9.3-18) QH = fcy,H CH QVnet (see NOTE 1 and A.9.3.3.7) (A.9.3-19) QM = fcy,M CM QVnet B (see NOTE 1 and A.9.3.3.7) (A.9.3-20) where fcy,V, fcy,H and fcy,M are defined in A.9.3.3.7. QVnet = (su·Nc·sc·dc) π B2/4 (A.9.3-21) CH and CM are determined distinguishing between clays with i) undrained shear strength linearly increasing with depth (from negligible strength at the mudline), ii) constant undrained shear strength and iii) strength profiles intermediate to those of i) and ii). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 164 © ISO 2023 – All right reserved i) For clays with undrained shear strength linearly increasing with depth (from negligible strength at the mudline) the formulations are given in Formulae (A.9.3-22) to (A.9.3-23). The proposed bearing capacity formulae should be used in normally consolidated to lightly overconsolidated clays in which the undrained shear strength increases linearly with depth with a normalised heterogeneity ratio ρsuB/sum that is equal or greater than 1,5. CH = CH,shallow = 0,127 for Dembed < Hcav = fH,deep·CH,deep for Dembed ≥ Hcav + 0,5B (A.9.3-22) CM = CM,shallow = 0,083 for Dembed < Hcav = CM,deep for Dembed ≥ Hcav + 0,5B (A.9.3-23) Values of CH and CM for spudcan penetration depths between Hcav and Hcav + 0,5B should be linearly interpolated. NOTE 1 CH,shallow and CM,shallow are applicable to cases where the cavity above the spudcan remains open (Martin and Houlsby (2001)[135]). CH,deep and CM,deep are based on centrifuge experiments and numerical analyses of deeply penetrated spudcans in normally consolidated clay (Zhang et al. (2013)[218], (2014c)[221]). These are given in Table A.9.3-4 in relation to soil sensitivity, St, and spudcan penetration depth, Dembed/B. Two-way linear interpolation is suggested to calculate CH,deep and CM,deep for St and Dembed/B. The yield surface is paraboloidal, with no evidence of a change of shape to ellipsoidal with increasing penetration depth (Zhang et al. (2014a)[219], (2014b)[220]). Hence, a = 0. The effect of laterally projected area ratio As/A on CH,deep is expressed as factor fH,deep in Figure A.9.3-15. As is the spudcan laterally projected embedded area (the projection of the area in contact with the soil) and A is the spudcan effective bearing area based on cross-section taken at uppermost part of bearing area in contact with soil (see Figure A.9.3-2). CM,deep was found to be unaffected by the spudcan aspect ratio. See Zhang et al. (2012b)[220]. . No further reproduction or distribution permitted. Printed / viewed by: 165 Table A.9.3-4 — Yield surface parameters CH,deep, CM,deep (after Zhang et al. (2014c)[221]) for Dembed ≥ Hcav + 0,5B St Dembed/B CH,deep CM,deep 1 0,5 1 1,5 2 3 0,186 0,228 0,277 0,303 0,325 0,090 0,095 0,102 0,106 0,107 2,2 0,5 1 1,5 2 3 0,170 0,206 0,248 0,267 0,286 0,089 0,092 0,098 0,101 0,104 3 0,5 1 1,5 2 3 0,168 0,199 0,233 0,255 0,278 0,088 0,090 0,096 0,099 0,102 4 0,5 1 1,5 2 3 0,165 0,193 0,216 0,236 0,257 0,087 0,088 0,093 0,096 0,099 Figure A.9.3-15 — Effect of spudcan aspect ratio As/A on CH,deep [after Zhang et al. (2012b)[220]] ii) For clays with constant undrained shear strength the formulations are given in Formulae (A.9.3-24) to (A.9.3-25): . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 166 © ISO 2023 – All right reserved CH = CH,shallow + (CH,deep − CH,shallow) Dembed/B for Dembed < B (see NOTE 3) (A.9.3-24) = CHdeep for Dembed ≥ B CM = [0,1 + 0,05a(1+b/2)] (A.9.3-25) where CH,shallow = [suoA + (suo + su,l) As]/QVnet (A.9.3-26) CH,deep = [1,0 + (su,a/suo)] [0,11 + 0,39(As/A)] (with backfill) (A.9.3-27) NOTE 2 The formulation given in Formula (A.9.3-27) for the case of deep embedments in clay is partly based on the finite element results in Templeton (2009)[187], and reduces to Formula 2 in that paper for the case of su,a = suo, A is the spudcan effective bearing area based on cross-section taken at uppermost part of bearing area in contact with soil (see Figure A.9.3-2); As is the spudcan laterally projected embedded area (the horizontal projection of the area in contact with the soil), a = Dembed/(2,5B) for Dembed < 2,5B (see NOTE 6) (A.9.3-28) = 1,0 for Dembed ≥ 2,5B b = (Db su,a)/(Dembed suo) (see NOTE 4) (A.9.3-29) Db is the depth of backflow (see A.9.3.2.1.4), equal to (Dembed − Hcav); infill should not be considered (see NOTE 2); su is the undisturbed undrained shear strength; su,a is the undrained shear strength of backfill material above the spudcan, accounting for disturbance and soil sensitivity; suo is the undisturbed undrained shear strength at deepest embedment depth of maximum bearing area (Dembed below sea floor); su,l is the undisturbed undrained shear strength at the spudcan tip. Formula (A.9.3-27) is only valid for cases including backfill. In cases without backfill CH,deep should be taken as CH,shallow as per Formula (A.9.3-26). iii) Clays with shear strength profiles intermediate to those of i) and ii). For clays with undrained shear strength at or near the mudline that is substantial but less than the undrained shear strength near the embedment depth, the following formulae should be used. See Templeton (2021)[188]. For the moment coefficient a linear interpolation should be used: CM = CM,NC + (su,nml / su,ned)( CM,U – CM,NC) < CM,U (A.9.3-29) . No further reproduction or distribution permitted. Printed / viewed by: 167 where: CM is the moment capacity coefficient; CM,NC is the moment capacity coefficient for the normally consolidated case per A.9.3.3.2 a) i); CM,U is the moment capacity coefficient for the uniform strength case per A.9.3.3.2 a) ii); su-ned is the minimum undrained shear strength near (within ¼ spudcan diameter below) the embedment depth; su-nml is the minimum (undrained shear) strength within ¼ spudcan diameter below the mudline. For the horizontal factor a similar linear interpolation should be used: CH = CH,NC + (su,nml / su,ned) ( CH,U – CH,NC) < CH,U (A.9.3-30) where: CH is the horizontal capacity coefficient; CH,C is the horizontal capacity coefficient for the normally consolidated case per A.9.3.3.2 a) i); CH,U is the horizontal capacity coefficient for the uniform strength case per A.9.3.3.2 a) ii); su,ned is the minimum undrained shear strength near (within ¼ spudcan diameter below) the embedment depth; su,nml is the minimum undrained shear strength within ¼ spudcan diameter below the mudline. NOTE 3 For CH, Templeton (2021)[188] provides a power law interpolation with m = 0,36 for the power law exponent, but with the choice of m=1,0, the power law reduces to the simpler, cautious, linear interpolation of Formula (A.9.3-30). b) The sand formulation is given in Formulae (A.9.3-31) to (A.9.3-32), 𝑄𝑄H = 0,12􁉆𝑄𝑄V − 𝑝𝑝o′ π𝐵𝐵24􁉇 (see NOTE 5) (A.9.3-31) = 0,12 QVnet 𝑄𝑄M = 0,075𝐵𝐵􁉆𝑄𝑄V − 𝑝𝑝o′ π𝐵𝐵24􁉇 (see NOTE 5) (A.9.3-32) = 0,075 B QVnet a = 0,0 (see NOTE 6) where p′o is the effective overburden pressure at embedment depth, Dembed, of maximum spudcan bearing area; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 168 © ISO 2023 – All right reserved QVnet = (γ′dγNγπB3/8) + (p′odqNqπB2/4) − (p′o πB2/4); dγ is the depth factor on self weight for drained soils; dγ = 1,0; dq is the depth factor on surcharge for drained soils, dq = 1 + 2tanϕ′ (1-sinϕ′)2 arctan(Dembed/B) where arctan(Dembed/B) is in radians; B is the maximum effective spudcan diameter in contact with the soil; γ ′ is the submerged unit weight of the soil; Nγ and Nq are dimensionless bearing capacity factors calculated for the axisymmetric case (no further shape factor should be applied). For sand, the values of 0,12QVnet and 0,075BQVnet are based on experimental evidence that includes Tan (1990)[178], Gottardi and Butterfield (1993)[79], (1995)[80], Gottardi et al. (1999)[81], Byrne and Houlsby (2001)[39], Bienen et al. (2006)[24], and Cassidy (2007)[41]. There are no existing data for spudcans deeply embedded in sand. The application of these parameters, which are calibrated to shallow penetrations, is likely to be conservative for the deep penetration case. At zero vertical loading a shallow sand foundation has no horizontal or moment capacity because it is cohesionless and conforms to the yield interaction formula in bearing. Conversely, for spudcans in clay, when there is adhesion and/or suction, there can be horizontal and moment capacity in excess of the yield interaction surface given above when FV < 0,5 QV. In such cases, the yield surface expansion given in A.9.3.3.3 may be used. For deep penetration cases where suction capacity exists, QV can be less than zero and the yield surface may be enlarged; the simplified expansion given in A.9.3.3.3 should not be used. NOTE 4 Both Dembed (the depth of embedment) and Db (the depth of backflow) are measured upward from the lowest elevation of the largest spudcan width. Db is taken as zero unless the top of the spudcan is effectively covered. NOTE 5 The horizontal capacity in sand or clay is calculated as a function of the net vertical bearing capacity. The moment capacities are calculated as a function of the product of the net vertical bearing capacity and the effective spudcan diameter. For clay, the net vertical bearing capacity is used because the weight of soil on top of the spudcan does not affect the horizontal and moment capacities. For sand, the use of net capacity is conservative because it neglects the increase in capacity due to the weight of any soil on top of the spudcan which has a beneficial effect on the horizontal and moment capacities. For the case of shallow embedment in clay, a conservative value for CH can be established by considering minimal embedment of a flat-bottomed spudcan on very strong clay where the horizontal capacity per unit base area is given by the shear strength, and the vertical capacity per unit base area is approximately six times the shear strength, so that: QH = 0,16 QVnet. This value can be used as an alternative, conservative, horizontal capacity expression for shallow embedment in clay. NOTE 6 The depth interpolation parameter, a, is given as a function of the embedment, Dembed, which is measured as the depth below sea floor of the lowest point of the spudcan's maximum width. Technically, Dembed = 0 does not occur until the spudcan penetration is sufficient to fully seat the spudcan's maximum width. As a practical matter, penetrations shallower than this are not normally expected in clay, but in the event that such shallow penetrations are considered, the value a = 0 can be used. In many cases, simpler forms of the yield interaction formula can be used. Results from finite element analysis [see Templeton et al. (2005)[190] or Templeton (2006)[185]] indicate that insignificant error is incurred by the use of the value, a = 0 for embedment less than 0,3B or by the use of the value, a = 1 for embedment greater than 1,7B. . No further reproduction or distribution permitted. Printed / viewed by: 169 In the case of a = 0, the yield interaction formula reduces to the paraboloidal form given in Formula (A.9.3-3): 2222VVHMHMVV1610FFFFQQQQ+−−= (A.9.3-33) In the case of a = 1, the yield interaction formula reduces to the fully ellipsoidal form given in Formula (A.9.3-34): 22VVHMHMVV410FFFFQQQQ+−−= (A.9.3-34) Formula (A.9.3-16) for the yield surface can be conveniently rewritten to give the maximum available moment on the spudcan FM as a function of the applied horizontal and vertical forces as given in Formula (A.9.3-35): 05222VVVVHMMVVHVV16(1) 141,FFFFFFQaaQQQQQ=−−−+− (A.9.3-35) This formula only applies when VV0FQ<< and the condition given in Formula (A.9.3-36) is satisfied: 222VVVVHVVHVV016(1) 141FFFFFaaQQQQQ<−−−+− (A.9.3-36) A.9.3.3.3 Spudcans in clay with FV < 0,5 QV The yield surface in the region 0 < FV/QV < 0,5 (typically applicable to windward legs) can be replaced by an adhesion envelope that provides additional horizontal and moment capacity due to spudcan-soil adhesion, The adhesion envelope is applicable for vertical load levels less than (FV/QV)t which defines the tangent intercept between the adhesion envelope and the standard form of the yield surface and is dependent upon the adhesion factor, αs , and the “a” parameter that defines the form of the yield surface, The adhesion envelope can be expressed as given in Formula (A.9.3-37): 22HM1H2M100,FFfQfQ+−= (A.9.3-37) where 𝑓𝑓1 is the factor applied to horizontal capacity used in yield surface formula for embedded spudcans on clay, 𝑓𝑓1 = 𝛼𝛼s + 𝑚𝑚𝛼𝛼􁉀𝐹𝐹𝑉𝑉𝑄𝑄𝑉𝑉􁉁 (A.9.3-38) . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 170 © ISO 2023 – All right reserved f2 is the factor applied to moment capacity used in yield surface formula for embedded spudcans on clay, f2 = f1 where suction (i.e. uplift resistance) is available, or (A.9.3-39) f2 = 22VVVVVVVV16(1) 141FFFFaaQQQQ−−+− where suction cannot be relied upon; αs = 1,0 for soft clays (su = 20 to 40 kPa), or (A.9.3-40) αs = 0,5 for stiff clays (su = 75 kPa to 150 kPa), or αs is determined by linear interpolation when 40 < su < 75; mα is the gradient of the adhesion envelope, Figure A.9.3-16 provides a graphical representation of the adhesion envelope and the definitions of the parameters mα and (FV/QV)t, Figure A.9.3-16 — Illustration of the adhesion envelope modification to the standard yield surface for VVVtFFQ< αs is the adhesion factor and accounts for the degree of adhesion. The assessor should consider αs values within the range of 0,5 to 1,0 depending on site-specific soil data, spudcan/soil interface . No further reproduction or distribution permitted. Printed / viewed by: 171 roughness, etc. When hard clay is present at the surface with an αs value below 0,5, the standard form of the yield surface should be used, see Formula (A.9.3-16). The values for mα and (FV/QV)t have been determined for a = 0,0 (paraboloidal) as given in Formulae (A.9.3-41) and (A.9.3-42) and for a = 1,0 (ellipsoidal) as given in Formulae (A.9.3-43) and (A.9.3-44):  For a = 0: 𝑚𝑚𝛼𝛼=4􀵫1−􀶥𝛼𝛼s􀵯 (A.9.3-41) 􁉀𝐹𝐹𝑉𝑉𝑄𝑄𝑉𝑉􁉁𝑡𝑡=􀶧𝛼𝛼s4 (A.9.3-42)  For a = 1: 𝑚𝑚𝛼𝛼=1−𝛼𝛼s2𝛼𝛼s (A.9.3-43) 􁉀𝐹𝐹𝑉𝑉𝑄𝑄𝑉𝑉􁉁𝑡𝑡=𝛼𝛼s2𝛼𝛼s2+1 (A.9.3-44) Values of mα and (FV/QV)t for intermediate values of a can be solved for iteratively. Selected values of (FV/QV)t are provided in Table A.9.3-4: Table A.9.3-4 — Values of (FV/QV)t for various values of a and αs αs a 0,0 0,2 0,4 0,5 0,6 0,8 1,0 0,5 0,354 0,334 0,308 0,293 0,276 0,238 0,200 0,6 0,387 0,373 0,354 0,343 0,331 0,300 0,265 0,7 0,418 0,408 0,396 0,388 0,379 0,357 0,329 0,8 0,447 0,441 0,433 0,428 0,423 0,409 0,390 0,9 0,474 0,471 0,468 0,465 0,463 0,457 0,448 1,0 0,500 0,500 0,500 0,500 0,500 0,500 0,500 Selected values of mα are provided in Table A.9.3-5: Table A.9.3-5 — Values of mα for various values of a and αs αs a 0,0 0,2 0,4 0,5 0,6 0,8 1,0 0,5 1,172 1,200 1,239 1,264 1,295 1,378 1,500 0,6 0,902 0,917 0,937 0,950 0,965 1,006 1,067 0,7 0,653 0,661 0,670 0,676 0,683 0,701 0,729 0,8 0,422 0,425 0,429 0,431 0,434 0,440 0,450 0,9 0,205 0,206 0,207 0,207 0,208 0,209 0,211 1,0 0,000 0,000 0,000 0,000 0,000 0,000 0,000 . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 172 © ISO 2023 – All right reserved Formula (A.9.3-35) can be re-written to give the maximum moment on the spudcan as a function of the horizontal force as given in Formula (A.9.3-45): 052HM2M1H1,FFfQfQ=− (A.9.3-45) Formula (A.9-45) applies only when the conditions given in Formulae (A.9.3-46) and (A.9.3-47) are satisfied: VVVVt0FFQQ<< (A.9.3-46) and H1HFfQ< (A.9.3-47) For a vertical and horizontal force combination that lies inside the yield surface given in A.9.3-45, the moment on the spudcan is limited to the maximum available moment capacity QM. A.9.3.3.4 Modification of the yield surface for partial penetration in sand On seabeds of silica sands, conical spudcans that are not fully seated can develop increased moment capacity due to the rotation of the spudcan causing an eccentric seabed reaction which provides a beneficial resisting moment. The effect may be taken into account for spudcans with FV/QV > 0,5. The increased ultimate moment capacity QMp due to eccentric seabed reaction is estimated as the minimum of QMps and QMpv, calculated from Formulae (A.9.3-48) and (A.9.3-49) respectively; see Svanø (1996)[175]: 3MpsVnetmax0,075(/)QBQBB= (A.9.3-48) MpvV0,15QBF= (A.9.3-49) Note that the horizontal capacity is unaffected. The combined capacity should be checked against the modified yield interaction surface given in Formula (A.9.3-50): 2222VVHMHMpVV1610FFFFQQQQ+−−= (A.9.3-50) A.9.3.3.5 Expansion of the yield surface for additional penetration in sand Additional penetration of a spudcan in sands can be accounted for by using plasticity principles. Recommendations on updating stiffness and the flow of plastic displacements within a work-hardening framework are provided in Houlsby and Cassidy (2002)[98], Cassidy et al. (2002a)[43] and Bienen et al. (2006)[24]. . No further reproduction or distribution permitted. Printed / viewed by: 173 This increase in penetration can also result in increased structural utilizations, which should be assessed; see A.9.3.6.6. A.9.3.3.6 Expansion of the yield surface for additional penetration in clay For additional penetration of spudcans in clay, Wong and Murff (1994)[204] and van Langen and Hospers (1993)[193] provide work-hardening modifications to the yield surface formulae. Updated stiffnesses and capacities are determined through plasticity principles. A.9.3.3.7 Effect of cyclic loading on the yield surface A.9.3.3.7.1 General According to Andersen (2015)[20] and NGI (2018)[141], the degradation of clays under cyclic loading can reduce the capacity of offshore foundations. As the foundations of jack-up units are subjected to cyclic loading during storm events, this soil behaviour should be considered in a site assessment. The results of laboratory tests of soil samples under cyclic loading indicate that the cyclic undrained shear strength of clays under pure two-way cyclic loading (i.e., where the average load is zero) can be less than the corresponding static undrained shear strength. The magnitude of this reduction is dependent on the soil’s plasticity index, Ip, and has some dependency on the overconsolidation ratio, ROC, as indicated in Figure A.9.3-18, adapted from Andersen (2015)[20]. When there is a combination of cyclic and non-zero average loading, the soil strength can be considered to comprise of average and cyclic strength components. Depending on the ratio of the cyclic to average loading during the wave event being assessed, this soil strength can be less than, equal to or greater than the static soil strength. The guidance below, taken from NGI (2018)[141], provides a generalized and simplified approach to estimate the effect of cyclic load on the foundation capacity in clay under combined average and cyclic load components on a leg in the absence of appropriate site-specific cyclic soil strength data, see Figure A.9.3-17. The definition of the average (a) and the cyclic (b) load components is presented in Figure A.9.3-17. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 174 © ISO 2023 – All right reserved Key a average loading component b cyclic loading component F footing loading (on one leg) t time Figure A.9.3-17 — Average and cyclic loading components as per NGI (2018)[141] The ultimate bearing capacity of a foundation in clay can be determined from Formulae (A.9.3-18) to (A.9.3-20) by multiplying each of the static vertical, horizontal and moment bearing capacities by a corresponding cyclic degradation factor, fcy,V, fcy,H and fcy,M respectively. This procedure should be performed for each spudcan separately as Fa,i and/or Qi can vary between spudcans. Due to the simplified nature of the formulation, the ultimate bearing capacity obtained in this manner is limited such that it does not exceed the static ultimate bearing capacity. Guidance on implementing cyclic degradation effects in clay for assessments based on calculated foundation capacities is given in E.4. The unfactored average individual force component on the foundation, Fa,i, is defined as the average of the peak and trough of the total foundation loading for the assessment load case (i.e. including all force contributions due to co-linear actions from wind, wave, current, inertia, weight and buoyancy, etc. during one wave cycle) where the subscript, i, refers to each of the vertical, horizontal and moment average force components on each foundation. It is, in most cases, conservative to calculate the average forces by considering only the unfactored co-linear wind and current actions for each storm direction, as specified in the assessment load case. The average vertical force acting on each spudcan depends upon the storm heading direction, e.g. whether each spudcan is the windward or leeward leg; it should be expressed in terms of net vertical force, i.e. the gross vertical force, FV, less the overburden weight, 􀵫𝑝𝑝o’π𝐵𝐵2􀵯4⁄ The cyclic degradation factor, fcy,i can be determined for each load component i (vertical, horizontal, moment) as given in Formula (A.9.3-51) and should not exceed 1,0: fcy,i = fcy,0 + Fa,i /Qi ≤ 1,0 (A.9.3-51) where fcy,0 is an inherent soil property that represents the ratio of the undrained shear strength (τcy,f) under pure two-way cyclic loading (i.e. zero average load) to the static undrained shear strength (su). These recommendations, and the data plotted in Figure A.9.3-18, are valid for non-calcareous and non-cemented clays only. The majority of the data presented is for normally consolidated soils. The few data points for ROC > 1 soils do not seem to indicate a strong effect of ROC. However, there are not sufficient data to draw strong conclusions with respect to the effect of ROC upon cyclic degradation. Fa,i is the unfactored average vertical, horizontal or moment force component over a wave cycle on the foundation of one leg (see above). Fa,v is the average component of the unfactored net vertical footing force given by 𝐹𝐹V−􀵫𝑝𝑝o’π𝐵𝐵2􀵯4⁄, where FV is defined in Formula (A.9.3-17). Qi is the corresponding unfactored static vertical (QVnet), horizontal or moment bearing capacity (i.e. without cyclic degradation), see A.9.3.3.7.2. . No further reproduction or distribution permitted. Printed / viewed by: 175 A detailed evaluation of the average and cyclic load components at each spudcan for each assessment load case can be substituted by a simplified conservative calculation of fcy,i. Guidance on this simplified approach is provided in A.9.3.3.7.3 Key Data Labels Overconsolidation ratio, ROC. Points labelled p0’ refer to tests on normally consolidated clays that have been consolidated to the in situ effective stress, p0’. ~ means approximately. Line of best fit 0,41 Ip0,224 Ip plasticity index in percent fcy,0 ratio of the cyclic to static shear strength of the soil. Figure A.9.3-18 — Ratio between cyclic and static undrained shear strengths of non-calcareous and non-cemented clays for ten equivalent cycles as a function of plasticity index (valid for symmetrical direct simple shear cyclic loading) [Adapted from Figure 12.31 in Andersen (2015)[20]] A.9.3.3.7.2 Assumptions The methodology described in A.9.3.3.7.1 is based on the following assumptions:  Static foundation capacities (Qi) are calculated using undrained shear strengths, that are applicable for the vertical, horizontal and moment failure modes within the soil, and are obtained using a standard laboratory testing rate of shear strain of 3 to 5% per hour;  That calculations indicating that normalised cyclic shear strengths can be used to estimate normalized cyclic capacities (NGI, 1992)[140];  That a unidirectional cyclic loading history that can be represented by 10 equivalent cycles of the maximum load in the storm with a load period of 10 seconds. This can be conservative for normally and lightly overconsolidated clays (NGI, 1992)[140]. The approach described in A.9.3.3.7 is formulated considering extreme storm conditions and is not valid for cyclic loading due to earthquakes. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 176 © ISO 2023 – All right reserved  The cyclic degradation parameters being applied to the net foundation bearing capacities and fcy,i being evaluated using the ratio of the average net vertical, horizontal or moment force component on the foundation to the net static vertical, horizontal or moment foundation capacity. A.9.3.3.7.3 Simplified conservative calculation of Fa,i The following simplified conservative assessment approach can be used to evaluate the cyclic degradation parameters, fcy,i.  If Fa,V/QVnet > 0,3 then fcy,V = 1,0 where Fa,V can be taken as the lowest value of 𝐹𝐹V −𝑝𝑝o’π𝐵𝐵2/4 for all legs under still water conditions; else fcy,V = fcy,0 + Fa,V /QVnet ≤ 1,0  fcy,H = fcy,0 + Fa,H /QH ≤ 1,0 where Fa,H can, in this simplified approach, be taken as the total unfactored average horizontal load on the jack-up due to horizontal co-linear wind and current actions divided by the number of legs;  fcy,M = fcy,0 based on the conservative assumption that Fa,M = 0,0. Alternatively, in the absence of information on the average force components, fcy,H = fcy,M = fcy,0 for the horizontal and moment capacities and fcy,V can be taken as 1,0 if Fa,V/QVnet > 0,3. • NOTE 1 Fa,V will typically exceed 30% of the net vertical static bearing capacity, resulting in a vertical cyclic degradation factor, fcy,V, of 1,0 in most cases. The horizontal and moment force components can be more symmetrical, i.e. have relatively small average force components; consequently, the assumption that these average load components are zero will result in cyclic degradation factors fcy,H = fcy,M = fcy,0. • NOTE 2 Although the ratio Fa,V/QVnet can be less than 0,3 for windward legs for the assessment load case, for such vertical load levels the horizontal foundation capacity, QH, is mostly governed by the soil strength parameters, rather than the vertical foundation capacity. Consequently, implementation of cyclic degradation of the windward legs’ vertical capacity for such load cases is not necessary as it would not reduce the horizontal and moment capacities, see A.9.3.3.3. A.9.3.4 Foundation stiffness A.9.3.4.1 Vertical, horizontal and rotational stiffness Vertical and horizontal stiffnesses of the foundation are based on the elastic solutions for a rough flat-based circular rigid disk on an elastic half-space with modification factors to account for spudcan embedment. For the effects of leg embedment, see A.9.3.4.6. The elastic stiffness factors are calculated assuming full contact of the spudcan with the seabed. If the vertical reaction is insufficient to maintain full contact as the moment increases, then reduced stiffnesses should be used. The stiffness factors are derived for a homogeneous, linear, isotropic soil as given in Formulae (A.9.3-52) to (A.9.3-54): 𝐾𝐾1 = 𝐾𝐾d1 2𝐺𝐺max𝐵𝐵(1−𝜈𝜈) (vertical stiffness) (A.9.3-52) 𝐾𝐾2 = 𝐾𝐾d2 16𝐺𝐺max𝐵𝐵(1−𝜈𝜈)(7−8𝜈𝜈) (horizontal stiffness) (A.9.3-53) 𝐾𝐾3 = 𝐾𝐾d3 𝐺𝐺max𝐵𝐵33(1−𝜈𝜈) (rotational stiffness for relatively low levels of loading; see Winterkorn and Fang (1975)[202]) (A.9.3-54) Torsional spudcan foundation stiffness (i.e. for spudcan rotation about its vertical axis) should not be used. . No further reproduction or distribution permitted. Printed / viewed by: 177 The selection of the small-strain shear modulus of the foundation soil, Gmax, is discussed in A.9.3.4.3 to A.9.3.4.5. A high or a low representative value should be selected as appropriate for the analysis being undertaken, e.g. the upper value is appropriate for fatigue related analysis. The shear modulus is influenced by the stress level and strain amplitude. In general, the shear modulus decreases with increasing strain amplitude. In this document, the consequences are addressed by reducing the stiffnesses (see A.9.3.4.2.2). NOTE Although the cross-coupling stiffness, K4, which links horizontal footing displacements and footing rotations to moment and horizontal loads, respectively, is not explicitly calculated, it is incorporated to some extent by the choice of the seabed reaction point as described in A.8.6.2. A.9.3.4.2 Stiffness modifications A.9.3.4.2.1 Embedment Table A.9.3-6 provides values for the stiffness depth factors Kd1, Kd2 and Kd3, to account for embedment effects on the stiffness of flat plate and conical type footings on an elastic half space, after Bell (1991)[23]. Values for the case of partial backfill can be interpolated from the values for full and no backfill provided in the tables. Zhang et al. (2012a)[216] also present stiffness depth factors for typical spudcan-shaped footings in undrained clay (Poisson's ratio, ν = 0,5) based on a constant rigidity index profile with depth; care is required when using this approach for soil profiles where this is not the case, e.g. where the overconsolidation ratio is not constant with depth. For embedment depths 2D/B greater than 4,0, the stiffness depth factors for 2D/B = 4,0 should be used (data extrapolation is not recommended). Table A.9.3-6 — Stiffness depth factors Stiffness factors for ν = 0,0 2D/B Kd1 Kd2 Kd3 No backfill Full backfill No backfill Full backfill No backfill Full backfill 0,0 1,00 1,00 1,00 1,00 1,00 1,00 0,5 1,15 1,21 1,33 1,49 1,28 1,64 1,0 1,28 1,41 1,44 1,71 1,43 2,05 2,0 1,42 1,70 1,51 1,92 1,51 2,31 4,0 1,59 2,00 1,61 2,06 1,57 2,41 Stiffness factors for ν = 0,2 2D/B Kd1 Kd2 Kd3 No backfill Full backfill No backfill Full backfill No backfill Full backfill 0,0 1,00 1,00 1,00 1,00 1,00 1,00 0,5 1,11 1,18 1,32 1,47 1,23 1,54 1,0 1,21 1,34 1,42 1,67 1,37 1,90 2,0 1,34 1,59 1,48 1,85 1,44 2,15 4,0 1,49 1,85 1,58 1,98 1,51 2,25 . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 178 © ISO 2023 – All right reserved Stiffness factors for ν = 0,4 2D/B Kd1 Kd2 Kd3 No backfill Full backfill No backfill Full backfill No backfill Full backfill 0,0 1,00 1,00 1,00 1,00 1,00 1,00 0,5 1,08 1,14 1,31 1,45 1,18 1,43 1,0 1,16 1,27 1,41 1,64 1,31 1,76 2,0 1,27 1,48 1,48 1,80 1,39 2,01 4,0 1,41 1,72 1,57 1,92 1,47 2,13 Stiffness factors for ν = 0,5 2D/B Kd1 Kd2 Kd3 No backfill Full backfill No backfill Full backfill No backfill Full backfill 0,0 1,00 1,00 1,00 1,00 1,00 1,00 0,5 1,07 1,10 1,32 1,44 1,18 1,39 1,0 1,15 1,23 1,44 1,62 1,31 1,71 2,0 1,25 1,44 1,51 1,78 1,40 1,99 4,0 1,40 1,69 1,59 1,91 1,51 2,16 A.9.3.4.2.2 Linear vertical, linear horizontal and secant rotational stiffness Except for simple dynamic analyses with linearized foundations contained within A.10.4.4.1.2 Option 1, the following procedure should be used if the reduction of rotational stiffness is not included in the soil model. The method accommodates stiffness reduction in a simple manner for responses within the yield surface. If the force combination (FV, FH, FM) lies outside the yield surface, the linearized rotational stiffness at the spudcan should be reduced using iterative analysis until the force combination lies on the yield surface. Although the force combination (FV, FH, FM) lies inside the yield surface, the initial estimate of linearized rotational stiffness should also be reduced by following the iterative procedure in A.10.4.4.1.2 and using the foundation rotational stiffness reduction factor, fr, which has an increasing effect as the yield surface is approached. The factor is obtained from Formula (A.9.3-55); see Templeton (2007)[186]: fr = (1 − n) rf /ln[(1 − nrf)/(1 − ___________rf)] (A.9.3-55) The parameter, n, accommodates spudcan rotation resistance curves with various degrees of curvature change. In practice, the value of this parameter should be set to suit the data (either empirical or analytical) applicable to the jack-up and site. Finite element analysis for the Gulf of Mexico (Templeton, 2007)[186] clay types indicate the range of n = −0,25 to −1,0, with n = −0,5 providing the best overall representation. In the absence of directly applicable data, the value of n can be set to 0. In this case, the rotational stiffness reduction factor expression takes the simpler form given in Formula (A.9.3-56): fr = −rf /ln(1 − rf ) (A.9.3-56) . No further reproduction or distribution permitted. Printed / viewed by: 179 As n approaches 1,0 the stiffness reduction expression tends towards the form given in Formula (A.9.3-57), which gives the most conservative treatment of stiffness reduction: fr = 1 − rf (A.9.3-57) The variable, rf, in the stiffness reduction expression is the failure ratio defined by Formula (A.9.3-58): 0522HMHMf0522VVVVVVVV10161141,,,()FFQQrFFFFaaQQQQ+=≤−−+− (A.9.3-58) where “a” is as defined in A.9.3.3.2. NOTE rf > 1,0 implies that the force combination (FV, FH, FM) lies outside the yield surface. Under such conditions, the reduced stiffness factor is not applicable, and the rotational stiffness is reduced until the force combination lies on the yield surface. For fully embedded foundations in clays at vertical force ratio VVVVt/FFQQ<, the failure ratio can be expressed as given in Formula (A.9.3-59): 0522HMf1H2M10,,FFrfQfQ=+≤ (A.9.3-59) where VVtFQ, f1 and f2 are as defined in A.9.3.3.3. A.9.3.4.2.3 Non-linear vertical, horizontal and rotational stiffness A full yield interaction surface model that includes non-linear vertical, horizontal and rotational stiffnesses implicitly incorporates the necessary stiffness reduction as a consequence of work-hardening plastic displacement and rotation [van Langen et al. (1997)[194], Wong et al. (1993)[205], and Cassidy et al. (2004b)[46]]. The stiffness reduction factor should not be applied. A.9.3.4.2.4 Non-linear continuum foundation model A continuum foundation model that includes non-linear soil behaviour (e.g. elastic-plastic work hardening) implicitly incorporates the necessary stiffness reduction. The stiffness reduction factor should not be applied. A non-linear continuum foundation model should not be used unless one of the simpler analysis methods has been used to provide a benchmark for the results. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 180 © ISO 2023 – All right reserved A.9.3.4.3 Selection of shear modulus, Gmax , for clay The value of the small-strain shear modulus for clay, Gmax, should be based on the value of the undrained shear strength, su, measured at the depth z = Dembed + 0,15B, where B is the effective diameter of the spudcan in contact with the soil and Dembed is the predicted embedment depth below the sea floor of the lowest point on the spudcan with diameter B. Where the clay is significantly layered, the average strength within the range z = Dembed to z = Dembed + 0,3B should be used. Except in areas with carbonate clays or clayey silts the shear modulus should be calculated from Formula (A.9.3-60), see Cassidy et al. (2002b)[44] and Noble Denton (2006)[142]: 𝐺𝐺max=𝑠𝑠u600(𝑅𝑅OC)0,25 subject to the limitations given below. (A.9.3-60) where Gmax is the maximum value of the shear modulus (of the foundation soil), which occurs at small strain; NOTE In forming estimates of foundation stiffness from linear elastic solutions to represent non-linear soil behaviour, one general method uses the linear elastic stiffness solution with a shear modulus taken as a function of strain level. Another method uses a non-linear stiffness function, which varies with the amplitude of the action and a constant shear modulus. In the former method a distinction is made between Gmax (the maximum value of the shear modulus, which occurs at small strain) and G (the general shear modulus, which varies with strain magnitude). In the latter method, the maximum value of shear modulus is used and no such distinction in terms is made. The process outlined in A.9.3.4.2.2 adopts the latter approach and hence Gmax is referred to throughout this document. ROC is the overconsolidation ratio; For extreme loading situations, and in the absence of other data, Gmax/Su should be conservatively limited to 400; see Noble Denton (2006)[142] which is based on overconsolidated clays with plasticity indices of up to 60 %. Alternatively due consideration should be given to the possibility of determining site-specific shear moduli for cohesive soils other than overconsolidated clays and/or where the plasticity indices exceed 60 %. Gmax/Su = 600 is supported by field data for jack-up responses in low ROC clays in the Gulf of Mexico; see Templeton (2006)[185]. In some cases, higher ratios of Gmax/Su have been reported and it should be recognized that Gmax/Su generally decreases with increasing plasticity index and increases with increasing overconsolidation ratio, as shown in Figure A.9.3-19, reproduced from Figures 11.5 of Andersen (2015)[20]. The normalization with respect to undrained shear strength shown in Figure A.9.3-19a is with reference to the undrained shear strength from direct simple shear tests. Where the shear modulus is not supported by site-specific data, the assessor should account for this trend when determining Gmax. The recommendations given above (Cassidy et al., 2002b)[44] are intended for use in site-specific assessments for both extreme loading and applications involving small strain beneath the spudcan. In the calculation of fixity for extreme loading, the rotational stiffness based on the small-strain Gmax values is degraded, either explicitly in the linearized foundation model using the stiffness reduction formulae given in A.9.3.4.2.2, or implicitly using non-linear foundation models. In the case of small- . No further reproduction or distribution permitted. Printed / viewed by: 181 strain applications such as in structural fatigue analysis, the stiffness reductions do not apply, and it can be appropriate to adopt a high representative value of Gmax. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 182 © ISO 2023 – All right reserved a) Gmax normalized with respect to undrained shear strength from direct simple shear tests b) Gmax normalized with respect to reference effective stress Key Data – OCR = 1,0 Data – OCR = 1,0 – 1,5 Data – OCR = 1,5 – 4,0 Data – OCR = 4,0 – 10,0 Data – OCR = 10,0 – 40,0 Fit: OCR = 1 Fit: OCR = 4 Fit: OCR = 10 Fit: OCR = 40 Ip plasticity index in percent Roc over-consolidation ratio Gmax maximum shear modulus that occurs at small strain suD undrained shear strength from direct simple shear tests σ’ref reference effective stress defined as σ’ref = pa(σ’vc/pa)0.9 where pa = 100kPa σ’vc vertical effective consolidation stress NOTE 1 The determination of Gmax via the use of rigidity index is inherently approximate. NOTE 2 Adapted from Andersen (2015)[20], Figure 11.5. Figure A.9.3-19 — Normalized small-strain shear modulus as a function of plasticity index and overconsolidation ratio A.9.3.4.4 Selection of shear modulus, Gmax, for sand For sands, the small-strain shear modulus should be computed from Formula (A.9.3-61): 𝐺𝐺max𝑝𝑝𝑎𝑎 = 𝑗𝑗􀵬𝑉𝑉sw𝐴𝐴𝑝𝑝𝑎𝑎􀵰0,5 (A.9.3-61) where . No further reproduction or distribution permitted. Printed / viewed by: 183 j is the dimensionless stiffness factor, R23009500,Dj=+; pa is the atmospheric pressure, typically taken as 101,3 kPa; DR is the relative density (expressed in percent); Vsw is the gross vertical spudcan reaction inclusive of backfill under still water conditions (the reaction that would be obtained if the jack-up were supported on an infinitely rigid foundation, plus the reaction due to the submerged weight of any backfill on the spudcan, less the submerged weight of soil displaced by the spudcan below Dembed, the greatest embedment depth of maximum cross-sectional spudcan bearing area below the sea floor). The recommendations given above (Noble Denton Europe and Oxford University, 2006[142] developed from the work of Cassidy et al., 2002b[44] and Wroth et al., 1979[206]) are intended for use in site-specific assessments for both extreme loading and applications involving small strain beneath the spudcan. In the calculation of fixity for extreme loading, the rotational stiffness based on the small-strain Gmax values is degraded, either explicitly in the linearized foundation model using the stiffness reduction formulae given in A.9.3.4.2.2, or implicitly using non-linear foundation models. In the case of small-strain applications such as in structural fatigue analysis, the stiffness reductions do not apply, and it can be appropriate to adopt a high representative value of Gmax. A.9.3.4.5 Selection of shear modulus for layered soils Roesset (1980)[157] provides formulae for the vertical, horizontal, rotational and torsion stiffnesses of a rigid disc on a layer of finite thickness, including the effect of embedment into that layer. Guidance on soil moduli of multilayered systems is available in Ueshita and Meyerhof (1967)[191]. A.9.3.4.6 Soil-leg interaction For deep penetrations, typically experienced in soft clay conditions, the calculation of foundation fixity can be augmented with the inclusion of the lateral soil resistance on the leg members (Brekke et al., 1989)[34]. The lateral soil resistance of the backfill material can be modelled based on concepts proposed by Matlock (1970)[136] for lateral soil resistance of piles. The jack-up leg can be modelled as an equivalent pile for purposes of determining p-y, or load-deflection curves. The diameters of the individual members (i.e. leg chords and braces) give appropriate characteristic dimensions for determining the p-y curves. The p-y curves for each member are directionally combined to form equivalent p-y curves along the leg, accounting for soil layering and changes in leg geometry. Any external face of each leg in compressive contact with the soil may be assumed to contribute to the lateral resistance. Typically, equivalent springs at each bay elevation are used to simplify the calculations. A.9.3.5 Vertical-horizontal foundation capacity envelopes A.9.3.5.1 General ultimate vertical-horizontal foundation capacity envelope The general gross ultimate vertical-horizontal foundation capacity envelope for jack-up spudcans is a two-dimensional slice of the full vertical-horizontal-moment envelope as given in A.9.3.3.2. If the spudcan moment capacity is zero (i.e. FM = 0), the ultimate vertical-horizontal foundation capacity envelope is as given in Formula (A.9.3-62): . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 184 © ISO 2023 – All right reserved 222VVVVHHVVVV1611410()FFFFFaaQQQQQ−−−−−= (A.9.3-62) For small embedments (in the limit as a → 0), this formula reduces to Formula (A.9.3-63): VVHHVV410FFFQQQ−−= (A.9.3-63) where QV is taken to be equal to the gross ultimate vertical foundation capacity of the soil beneath the spudcan (achieved during preloading), evaluated as described in A.9.3.2.2 to A.9.3.2.6, and QH as defined in A.9.3.3.2. A.9.3.5.2 Ultimate vertical-horizontal foundation capacity envelopes for spudcans in sand The yield surface used for checking the vertical-horizontal foundation capacity of spudcans in sand is presented in A.9.3.5.1. The sliding failure envelope used for checking the sliding capacity of a spudcan in sand is as given in Formula (A.9.3-64): QHs = FVtan(δ) + 0,5γ′ (kp − ka) (h1 + h2) As (A.9.3-64) where FV is the gross vertical force acting on the soil beneath the spudcan due to the assessment load case Fd (see 8.8): FV = Vst − BS (with no backfill) FV = Vst + WBF,o + WBF,A − BS (with backfill) (A.9.3-65) h1 is the embedment depth to the uppermost part of the spudcan, (if not fully embedded h1 = 0); h2 is the spudcan tip embedment depth; ka is the active earth pressure coefficient (for su = 0), ka = tan2(45 − φ′/2); kp is the passive earth pressure coefficient, kp = 1/ka; δ is the steel/soil friction angle in degrees: δ = φ′ − 5° (for a flat-bottom spudcan, β = 180°), δ = φ′ − 0,5 (β − 170°) (for 170° < β < 180°), (A.9.3-66) δ = φ′ (for a conically shaped spudcan, β ≤ 170°) where β is the effective cone angle in degrees (see Figure A.9.3-3); φ′ is the effective angle of internal friction for sand in degrees. . No further reproduction or distribution permitted. Printed / viewed by: 185 A.9.3.5.3 Ultimate vertical-horizontal foundation capacity envelopes for spudcans in clay The yield surface used for checking the vertical-horizontal foundation capacity for spudcans in clay for FV > 0,5 QV is presented in A.9.3.5.1 and for FV < 0,5 QV in A.9.3.3.3. The sliding capacity, QHs, in clay can be assumed to be QH as defined in A.9.3.3.2. A.9.3.5.4 Ultimate vertical-horizontal foundation capacity envelopes for spudcans on layered soils The foundation capacity of layered soils can be determined using the principles of limiting equilibrium analysis or the finite element method. Alternatively, the formulae given in A.9.3.5.2 and A.9.3.5.3 can be used to make a conservative estimate of the ultimate vertical-horizontal capacity relationship for layered soils by considering failure through the weakest zones in such a soil profile. A.9.3.6 Acceptance checks A.9.3.6.1 General Figure A.9.3-20 shows the overall approach to the foundation acceptance checks. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 186 © ISO 2023 – All right reserved Figure A.9.3-20 — Approach to foundation acceptance checks . No further reproduction or distribution permitted. Printed / viewed by: 187 A.9.3.6.2 Level 1, Step 1a — Ultimate bearing capacity check for vertical loading of the leeward leg–- preload check (pinned spudcan) The preload check should be applied only when the horizontal force on the leeward leg spudcan, FH, is no greater than FH1 (see Table A.9.3-7) and when the forces are determined from an analysis model with pinned condition for all spudcans. In this case, the maximum gross vertical force FV should conform with the limit given in the applicable Formula (A.9.3-67) or Formula (A.9.3-68): FV ≤ vLo / γR,PRE − BS (with no backfill) (A.9.3-67) FV ≤ vLo / γR,PRE + WBF,o − BS (with backfill) (A.9.3-68) where γR,PRE is the preload resistance factor, γR,PRE = 1,10; WBF,o is the submerged weight of the overburden on top of the spudcan from backfill (backflow and infill) that is predicted to occur during preloading; FV is the gross vertical force acting on the soil beneath the spudcan due to the assessment load case Fd (see 8.8) as given in Formula (A.9.3-69): FV = Vst − BS (with no backfill) FV = Vst + WBF,o + WBF,A − BS (with backfill) (A.9.3-69) Vst is the vertical force applied to the spudcan due to the assessment load case Fd (see 8.8). This includes quasi-static contributions due to factored actions, and contributions from dynamic response, as appropriate, in accordance with the procedures of Clause 10, and also includes leg weight and water buoyancy but excludes the submerged weight of backfill (WBF,o + WBF,A) and the soil buoyancy of the spudcan below the bearing area BS; WBF,A is the submerged weight of any backflow and infill that is predicted to occur after the maximum preload has been applied and held. Table A.9.3-7 — Limiting horizontal capacity, FH1, for Step 1a bearing capacity check Soil type Embedment Limiting horizontal capacity, FH1 for Step 1a to apply Sand Partial [0,1 − 0,07 (B/Bmax)2] QVnet Full 0,03 QVnet Clay Any 0,03 QVnet NOTE 1 The constants in Formulae (A.9.3-62) and (A.9.3-63) include the effects of γR,PRE = 1,10. The limiting horizontal capacity, FH1, for Step 1a was determined from the intersection between unfactored vertical-horizontal bearing capacity envelope and maximum allowable gross vertical reaction, QV,max, with some reduction applied for conservatism. Assuming a = 0, the limiting horizontal capacity, FH1, corresponding to maximum vertical capacity, QV,max, can be computed from Formula (A.9.3-70): . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 188 © ISO 2023 – All right reserved R,PRELoR,PRELoH1HR,PREVR,PREV1141()()VVFQQQγγγγ−−=− (A.9.3-70) For γR,PRE = 1,10, Formula (A.9.3-70) can be approximated by FH1 ≈ 0,33 vLo QH/QV and is equivalent to FH1 ≈ 0,04 QVnet for shallow penetrations in sand. Conservatively, 0,03 was used for the limits given in Table A.9.3-7 (see also NOTE 2). NOTE 2 For shallow spudcan penetrations and vertical reaction of 0,9 QVnet, the available unfactored horizontal capacity is approximately 0,04 QVnet. If the horizontal reaction exceeds 0,04 QVnet, additional penetration can occur. The use of 0,03 QVnet in the check, therefore, includes a level of conservatism. If the spudcan is fully embedded, the additional penetration can be significant. Additional penetration can increase the soil resistance but, to increase the horizontal capacity to 0,1 vLo, the additional penetration is about 10 % of the spudcan diameter and outside tolerable limits. Conversely, where the spudcan is partially embedded (i.e. when the maximum spudcan bearing area is not mobilized), any additional penetration results in a significant increase of bearing capacity due to the rapid increase in the bearing area. An increase in embedded area of approximately 10 % increases the vertical bearing capacity such that, simultaneously, the horizontal foundation capacity increases to 0,1 vLo. NOTE 3 For partial spudcan penetration in sand, QVnet can be taken as being equal to vLo for the purposes of the Step 1a check. A.9.3.6.3 Level 1, Step 1b — Check of the windward leg — Pinned spudcan The windward leg check should be applied only when the horizontal force on the windward leg spudcan, FH, is no greater than FH1 (see Table A.9.3-7). In this case, the sliding stability of the windward leg is checked by ensuring that the vertical reaction complies with Formula (A.9.3-71): FV > (1 − 1/γR,PRE) QV (A.9.3-71) where γR,PRE is the preload resistance factor, γR,PRE = 1,10. In the case of a sand foundation, this check is valid for sand friction angle φ′ ≥ 25°. For friction angles φ′ < 25°, the sliding check in Step 2 should be performed. A.9.3.6.4 Level 2, Step 2a — Foundation capacity and sliding check — Pinned spudcan A.9.3.6.4.1 Step 2a — Foundation capacity check The combined vertical and horizontal forces on all spudcans should be checked against the corresponding factored foundation bearing capacity envelope and the factored sliding capacity envelope, see Figure A.9.3-21. Each leg’s spudcan reaction forces should lie within the corresponding factored vertical-horizontal foundation capacity envelope. In addition, the reaction forces should lie within the corresponding factored sliding capacity envelope. The following describes the construction of the factored vertical-horizontal foundation capacity envelope and the foundation capacity check for Step 2a which is also applicable to Step 2b. The construction of the sliding failure surface and the foundation sliding check is described in A.9.3.6.4.2. A reduction in the ultimate vertical bearing capacity, QV, of a spudcan foundation occurs when it is simultaneously subjected to a horizontal force, FH, and a moment, FM. The latter is ignored in Step 2a analyses as the spudcans are considered to be pinned. The vertical-horizontal foundation capacity for sands and clays can be generated according to A.9.3.5 and the spudcan reactions should be evaluated for each spudcan. To obtain the factored vertical-horizontal bearing envelope, the vertical-horizontal capacity envelope is scaled by the resistance factor, γR,VH, from the point of zero net reaction, i.e. (FH = 0, FV = WBF,o − BS). In effect, the envelope is shrunk towards this scaling origin. . No further reproduction or distribution permitted. Printed / viewed by: 189 A measure of the foundation utilization (see Clause 13) can be obtained by assessing the proximity of the loading point (FH, FV) to the factored vertical-horizontal bearing capacity envelope, see Figure A.9.3-21. When making the check, the magnitude of the vector to the loading point should be compared against the magnitude of the vector to the factored vertical-horizontal bearing capacity envelope. The origin of the vectors is arbitrary; however, for consistency and to help produce a meaningful value of the resulting utilization, the origin of the vectors (FH, FV)ORG should be taken on the vertical capacity axis (at zero shear) at 0,5 QV/γR,VH (see Figure A.9.3-21). Accordingly, each spudcan foundation should satisfy the capacity check given in Formula (A.9.3-72): | (FH, FV) − (FH, FV)ORG | ≤ | QVH,f − (FH, FV)ORG | (A.9.3-72) where (FH, FV) is the environmental response point (determined from factored actions); (FH, FV)ORG is the origin used for establishing the utilization; this should be taken as H = 0,0; V = 0,5QV/γR,VH; QV is the gross ultimate vertical foundation capacity; QVH,f is the point where the vector originating from (FH, FV)ORG and passing through (FH, FV) intersects the applicable factored vertical-horizontal capacity surface as defined in A.9.3.6.4.1 or the factored sliding capacity as defined in A.9.3.6.4.2. The factored vertical-horizontal capacity surface is derived by dividing the coordinates of the applicable surface from A.9.3.5 by the resistance factor γR,VH with respect to the point of zero net reaction (0,WBF,o − BS); γR,VH is the partial resistance factor for vertical-horizontal foundation bearing capacity, γR,VH = 1,10; |…| represents the vector magnitude. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 190 © ISO 2023 – All right reserved a) Sand b) Clay with spudcan buoyancy and no backfill Figure A.9.3-21 — Vertical-horizontal foundation capacity envelopes (1 of 2) . No further reproduction or distribution permitted. Printed / viewed by: 191 c) Clay with spudcan buoyancy and backfill Key 1 vertical-horizontal foundation capacity 2 factored vertical-horizontal foundation capacity (coordinates multiplied by 1/γR,VH) relative to the scaling origin as defined 3 sliding capacity (see A.9.3.6.4.2) 4 factored sliding capacity (unfactored horizontal sliding capacity coordinate multiplied by 1/γR,Hfc) 5 vectors indicating origin for construction of the factored V-H bearing capacity envelope |…| represents the vector magnitude H horizontal reaction or horizontal capacity QV gross ultimate vertical foundation capacity (with zero horizontal load) QVH,f point where the vector originating from (FH, FV)ORG and passing through (FH, FV) intersects the factored vertical-horizontal capacity surface as defined in A.9.3.6.4.1 or the factored sliding capacity surface as defined in A.9.3.6.4.2 U utilization for environmental response point (FH, FV) as given in A.9.3.6.4 V vertical reaction or vertical capacity γR,VH partial resistance factor for foundation (bearing) capacity γR,Hfc partial resistance factor for horizontal (sliding) capacity Figure A.9.3-21 — Vertical-horizontal foundation capacity envelopes (2 of 2) A.9.3.6.4.2 Step 2a — Foundation sliding check In Step 2a, the spudcan foundations should also be assessed using the following sliding check, since the factored sliding failure surface can lie within the factored vertical-horizontal bearing capacity envelope as in A.9.3.6.4.1, see figure A.9.3-21. The same procedure also applies for Step 2b. The horizontal capacity of the foundations of all legs should be checked for the horizontal forces on the spudcans, FH, in association with the gross vertical force FV. NOTE The most onerous case is likely to be with a single windward leg, the minimum variable load and the centre of gravity offset to leeward. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 192 © ISO 2023 – All right reserved The foundation should satisfy the capacity check given in Formula (A.9.3-73): | (FH, FV) − (FH, FV)ORG | ≤ | QVH,f − (FH, FV)ORG | (A.9.3-73) where QVH,f is the point where the vector originating from (FH, FV)ORG and passing through (FH, FV) intersects the applicable factored sliding capacity surface derived by dividing the horizontal coordinates of the applicable surface QHs from A.9.3.5.2 (sand) or A.9.3.5.3 (clay) by the resistance factor, γR,Hfc; QHs is the foundation sliding capacity; see A.9.3.5.2 (sand) or A.9.3.5.3 (clay); γR,Hfc is the partial resistance factor for horizontal foundation capacity where γR,Hfc = 1,25 for both sand (based on drained conditions and effective stress) and clay (based on undrained conditions and total stress); |…| represents the vector magnitude. A.9.3.6.5 Level 2, Steps 2b and 2c — Foundation capacity and sliding check — Spudcan with moment fixity and vertical and horizontal stiffness Step 2b and 2c foundation analyses inherently ensure conformity with the unfactored foundation yield surface, except that in a Step 2b analysis conformity is no longer assured when the moment fixity has reduced to zero, i.e. the spudcan has become pinned. The capacity checks to undertake in a Step 2b assessment are identical to those undertaken for Step 2a in which vertical-horizontal capacity and sliding capacity for sands and clays can be generated in accordance with A.9.3.5 and the spudcan reactions are evaluated for each spudcan. If the vertical and horizontal reactions from the response analysis (which has accounted for spudcan moment fixity with stiffness reduction) lie within the factored foundation capacity envelopes, the foundation is satisfactory. A Step 2c analysis implicitly includes a check on conformity with the unfactored foundation yield surface. When the frictional sliding surface intersects the foundation capacity envelope, sliding can occur before the response reaches the yield surface. When this sliding effect is included in the response analysis, no further Level 2 checks are required. When this sliding effect is not included, a sliding check should be undertaken in accordance with A.9.3.6.4.2. In all cases, the Level 3, Step 3a displacement check should be performed. A.9.3.6.6 Level 3, Steps 3a and 3b — Displacement check — Settlements resulting from exceedance of the foundation capacity Vertical settlement and/or sliding of a spudcan can occur if the forces on the spudcan due to the extreme event are outside the yield interaction surface computed for the spudcan at the penetration achieved during installation. Such settlements often result in a gain in capacity through expansion of the yield interaction surface. However, the integrity of the foundation can decrease in the situation where a potential punch-through exists, e.g. where dense sand overlies soft clay. More thorough analyses should be performed for such cases and for the complex and/or potentially dangerous foundation conditions listed in A.9.3.2.5 and A.9.3.2.6. A Step 3a check can be accomplished by identifying the “equivalent” preload level that would be required to expand the V-H yield surface used in Step 2 such that the factored capacity exceeds the forces on the spudcan. The added penetration associated with this “equivalent” preload is calculated using each of the three predicted load-penetration curves [using the best estimate, a high representative value and a low representative value of soil strength profile and separate global . No further reproduction or distribution permitted. Printed / viewed by: 193 response analyses as appropriate; see A.9.3.2.1.1 b)]. If any of these three additional penetrations is significant, the effects on the spudcan foundation and the structure should be evaluated and the procedure iterated to establish whether the consequences of the displacement on the other utilization checks are acceptable. A Step 3a check can also be performed when the Level 2a or 2b sliding or capacity check of a windward leg is not satisfied, or is no longer satisfied due to the additional penetration of a leeward leg as described above. In the case of a windward leg, sliding can occur when the factored load exceeds the factored capacity resulting in redistribution of the horizontal reaction to the leeward leg foundations. This effect can be assessed by limiting the factored horizontal reaction to the factored sliding limit (dependent on FV) and iteratively determining the redistribution of loads and the associated non-linear displacement of the structure. The effects on all spudcan foundations and the structure should be evaluated and the procedure iterated to establish whether the consequences of the displacement on all the other utilization checks are acceptable, including the foundation capacity of the other legs. A Step 3b analysis inherently includes a check on the direct consequences of spudcan displacement. Therefore, no foundation checks are required, although it should be shown that the results are not sensitive to the load-penetration assumptions, i.e. that small changes in the forces on the spudcan or assumed soil strength do not lead to large increases in penetration. When assessing the acceptability of displacements, due consideration should be given to operational limitations, e.g. jacking operations to level the unit and re-establish a safe hull elevation or to depart the site. The limits are dependent upon the jack-up and the configuration at the site. A.9.3.6.7 Foundation settlement not specifically addressed elsewhere Settlement of the spudcans should be estimated and checked. If necessary, corrective actions should be taken. The settlements of installed spudcans can be assessed from a combination of:  elastic settlements;  consolidation settlement;  settlements due to cyclic loading;  settlements due to seabed instability. The elastic settlements and consolidation settlements can be calculated using conventional analytical or numerical geotechnical models (see ISO 19901-4). The elastic settlements occur concurrently with applied actions and can be calculated as function of the basic elastic soil properties (ν and G) and the applied actions. The consolidation settlements of cohesive soils can be calculated using conventional models accounting for time effects. Cyclic environmental actions or operational vibrations can induce further settlements. Special attention should be given to cyclic loading in silty sand or silt. Cyclic loading can also involve a soil strength reduction. This can induce settlements due to bearing failure. Seabed instability due to scour or gas seeps involves a decrease in the effective bearing capacity. This can induce settlements due to local bearing failure. The settlements should be checked regularly. If necessary, level adjustments should be made or protective measures against scour development should be taken (see A.9.4.7). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 194 © ISO 2023 – All right reserved A.9.4 Other considerations A.9.4.1 Skirted spudcans Skirts are added to spudcans to provide additional foundation capacity and stiffness compared to conventional conical spudcan geometries. Within the skirt, the typical geometry of the underside of a skirted spudcan is either relatively flat or conical. In some cases, the leg chords may protrude below the skirt tip and achieve first contact with the sea floor, thus protecting the skirt whilst going on and off site. In the case of skirted spudcans with a flat underside, a level and undisturbed sea floor surface is required in order to minimize the potential for eccentricity of the foundation reaction. In order to realise the maximum benefit from using a skirted spudcan, the underside of the skirted spudcan should achieve full contact with the sea floor surface. Calculations should be performed to determine the penetration resistance of the skirt, including any bulkheads and internal or external stiffeners and, hence, whether the applied preload is sufficient to ensure that full contact is achieved. Methods for calculating the tip and skin friction components of the skirt penetration resistance are described in DNV-RP-C212 (DNV 2021f). In cases where the skirt tip has a greater thickness than the rest of the skirt, consideration should be given to the potential for a gap to form above the skirt tip during penetration into the seabed, especially in cohesive soils. If the penetration resistance exceeds the available preload spudcan reaction and partial penetration of the skirt occurs, consideration can be given to measures such as applying suction for increasing the penetration or infilling the resulting void within the skirt with suitable material introduced through valved pipes that penetrate into the skirt void. If, after preloading, the skirt is partially penetrated, the assessment should be revised to determine the consequences, including a consideration of the strength of the skirt. Consideration should also be given to the effects of compaction and/or consolidation of the soils within the skirt or any infill material used during preloading. If the voids within the skirt are not completely infilled, consideration should be given to the effect of movement of the enclosed seawater within the skirt due to spudcan rotation, especially for compartmentalized skirts in cohesionless soils where “piping” can occur due to flow of the enclosed water around stiffener plates or bulkheads. Once full contact has been achieved, the vertical bearing capacity of the skirted spudcan essentially corresponds to that of an embedded footing. As the soil within the spudcan skirt is effectively part of the spudcan, the weight of the enclosed soil plug should be incorporated in the penetration resistance calculations. At sites with relatively strong soils and where the underside of the skirted spudcan is flat, or any remaining voids are filled with an appropriate material, the ultimate bearing capacity of the foundation can be significantly greater than the applied preload. Guidance is provided in E.4 for the use of foundation capacities that are greater than those developed by preloading. The bearing capacity envelopes appropriate for skirted footings have been the subject of much research; see Dean et al. (1995)[56], Bransby and Randolph (1998[27], 1999[32]), Bransby and Yun (2009)[33], Cassidy et al. (2004a)[45], Eide et al. (1996)[69], Gourvenec (2003)[82], (2008)[83], Gourvenec and Randolph (2002)[84], Kellezi et al. (2005a[116], 2007[118], 2008[119]), Leland et al. (1994)[126] and Svanø and Tjelta (1996)[176]. The skirted spudcan has generally been modelled as a solid footing, however, care is warranted before making such an assumption as weaker soil from the seabed surface trapped within the spudcan skirt can influence the failure mechanisms developed, reducing the additional capacity available; see Bransby and Yun (2009)[33]. . No further reproduction or distribution permitted. Printed / viewed by: 195 When full spudcan-seabed contact is achieved, the embedment of the skirted spudcan can permit the use of elastic foundation stiffness depth factors corresponding to a solid footing as described in Bell (1991)[23]. The extraction resistance for a skirted spudcan can be substantial; consequently, skirted spudcans are not usually employed at sites where soil backfill can occur on top of the spudcans. Extraction can be assisted through the use of drainage and/or the application of water pressure within the skirt in order to minimize the development of suction within the soil below the spudcan. Soil can remain within the skirts after extraction of a skirted spudcan from a site with cohesive soils, which can influence the penetration response during subsequent installations. A.9.4.2 Hard sloping strata A hard, sloping stratum can be created by a sand wave, sand bank, scour around a platform, buried geomorphic features such as channels, footprints produced by previous jack-up emplacements, human-related seabed activity, or a combination of the above. Such slopes can cause eccentricity in the spudcan reaction, which can lead to emplacement and removal difficulties, particularly for leg designs with slender braces, as in the following examples.  The eccentric reaction can result in a significant leg bending moment in the region of the hull. Where this bending moment is reacted by the leg guides, the resulting large shear force can overstress the leg members.  If a fixation system (rack chocks) is employed at the leg-to-hull interface, the bending moment present at the time when the fixation system is engaged is locked into the leg. If the eccentricity of the spudcan reaction is subsequently exacerbated (e.g. by scouring around the spudcan), then the effective leg bending moment in the region of the hull can increase. When the fixation system is later disengaged, the redistribution of the moment in the leg for the revised support condition provided by the pinions and guides can cause overstress. Anticipated installation-induced stresses should be considered in the site-specific assessment (see 5.4.8). The foundation reactions should be assessed against bearing and sliding capacities of the sloping hard stratum. Consideration can be given to the potential benefit of seabed preparation prior to emplacement of the jack-up. A.9.4.3 Footprint considerations Surface or buried footprints from prior jack-up operations in the proposed field can cause eccentric reactions or lateral movement of the spudcan. One preventive approach is avoidance (i.e. positioning spudcans at some minimum distance away from the footprints) while mitigations include working the legs, leg stomping, seabed remediation, etc. Information on spudcan-footprint interaction can be found in Stewart and Finnie (2001)[173], Cassidy et al. (2009)[48], Dean and Serra (2004)[55], Jardine et al. (2001)[111], Teh et al. (2006)[181], Gaudin et al. (2007)[78], Gan et al. (2008)[77] and Foo et al. (2003)[73]. A.9.4.4 Leaning instability A lower bound estimate of the leaning stability can be obtained using the theory of Hambly (1985)[87]. However, such estimates have proven to be generally conservative due to the omission of beneficial effects such as spudcan fixity and lateral soil resistance on the legs. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 196 © ISO 2023 – All right reserved At locations where a relatively large proportion of the leg length is below the hull, a potentially unsafe condition (comparable to a punch-through situation) can occur. The potential for such incidents can be mitigated if appropriate installation procedures are adopted. These can, for example, include preloading the spudcans individually. A.9.4.5 Leg extraction difficulties Leg extraction difficulties can be caused by conditions including the following:  deeply penetrated spudcan in soft clay or loose silt;  skirted or caisson-type spudcan where uplift resistance can be greater than the installation reaction;  sites where the soil exhibits increased strength with time. A jack-up pulls its legs from the seabed by lowering the hull into the water, thereby generating a buoyant uplift force and inducing tensile forces in the legs. The force required to extract the leg is affected by several factors, including the nature of the soils, the depth of penetration, the geometry of the spudcan and whether soil backfill has occurred. The force available for leg extraction is frequently less than the force applied during installation. Where significant leg penetrations are attained, it is not uncommon for pulling of the legs to take several days, or in some cases much longer. Where leg extraction problems are predicted, a warning should be included in the site-specific assessment report. Potential mitigations include jetting and/or excavation of the surface soils. However, these measures can alter soil strength and the seabed topography, which can affect the future emplacement of jack-ups at the same site. Further details can be found in Byrne and Cassidy (2002)[38], Craig (1998)[49], Craig and Chua (1990b)[51], Craig et al. (2002)[52], Erbrich (2005)[70] and Purwana et al. (2005)[149]. A.9.4.6 Cyclic mobility, liquefaction and liquefaction-induced lateral flow A.9.4.6.1 General Liquefaction and/or cyclic mobility can occur as a result of low frequency excitation (waves) and higher frequency excitation (such as earthquakes and ice-flow-induced vibrations). Wave-induced liquefaction of the seabed soils can occur. Dean (1991)[54] presents approximate methods for estimating settlements of submerged foundations subjected to low frequency, non-earthquake, time dependent loading (these are not discussed further here). General guidance on the assessment of the potential for liquefaction and/or cyclic mobility from earthquakes is given by Kramer (1996)[121]; Idriss and Boulanger (2004)[104]; Kayen et al. (2013)[115]; Robertson (2015)[156]; and Boulanger and Idriss (2016)[30]. Large strains and degraded shear strength can also occur in very soft clay due to ground shaking (Boulanger and Idriss (2007)[28]) (this is not discussed further here). Assessment of the potential for, and the effects of, earthquake induced liquefaction on the jack-up involves addressing a) Liquefaction-induced lateral flow in the vicinity of the jack-up, Edgers and Karlsrud (1982)[68] and Stewart and Kwok (2008)[171], . No further reproduction or distribution permitted. Printed / viewed by: 197 b) Liquefaction initiation in the zone of influence of the spudcan foundation, c) Spudcan displacements and/or loss of support induced by liquefaction, and d) Actions on the leg from liquefied zones. The risk of earthquake induced liquefaction at the specific site can be assessed by simplified (A.9.4.6.5) or detailed (A.9.4.6.6) procedures. The liquefaction assessment discussed in A.9.4.6.3 – A.9.4.6.6 is applicable only to siliceous sands and non-plastic silts and should not be applied to other soil types, such as carbonate soils, see 9.4.10 and A.9.4.10. It is emphasized that the simplified methods in A.9.4.6.5 are based on the 1 000 year earthquake and free-field conditions, i.e. not considering the effects of the presence of the jack-up. This is a significant limitation of these methods and potentially unconservative. Unless these methods indicate that the likelihood of liquefaction is low, a detailed assessment should be performed based on the ALE event and include the presence and dynamic response of the jack-up. A.9.4.6.2 Glossary A.9.4.6.2.1 Cyclic mobility Temporary or permanent deformation of soil that occurs when cyclic loading creates (excess) pore pressure. A.9.4.6.2.2 Liquefaction Liquefaction is a phenomenon in which the strength and/or stiffness of a soil is reduced due to an increase in pore-water pressure caused by earthquake shaking or other cyclic loading. A.9.4.6.2.3 Liquefaction potential Susceptibility of the soil to the onset of liquefaction under a reference earthquake motion. A.9.4.6.2.4 Free-field Seabed not subject to the effect of geotechnical works or structures. A.9.4.6.2.5 Liquefiable Susceptible to liquefaction or cyclic mobility for a contemplated means of initiation. A.9.4.6.2.6 Liquefaction-induced lateral flow Liquefaction leading to mass flow. A.9.4.6.3 Assessment of earthquake-induced liquefaction Where spudcans are founded on liquefiable soils, actions from an earthquake can cause large movements of a spudcan in both vertical as well as horizontal directions. The potential consequences on jack-ups can include: a) loss or reduction of bearing capacity; b) excessive settlement; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 198 © ISO 2023 – All right reserved c) differential settlement among the legs; d) lateral spreading of the seabed resulting in either uniform or differential leg displacements; e) loss or reduction of spudcan rotational stiffness. Consideration should be given to possible effects of additional actions that can occur from liquefied soil surrounding or above the spudcans. To assess the potential consequences of liquefaction to the jack-up on a site, the following three clauses provide possible methods with increasing level of complexity: 1) Identify whether soils on the site are susceptible to liquefaction (A.9.4.6.4). 2) Perform a free-field liquefaction triggering assessment based on simplified procedures or non-linear site response analysis (A.9.4.6.5). 3) Assess liquefaction and its consequences in a detailed analysis including the jack-up (A.9.4.6.6). An assessment of the potential for triggering of liquefaction can be performed by evaluating the ratio of Cyclic Stress Ratio and Cyclic Resistance Ratio. This can be done by  Using simple formulae with available geotechnical data, such as CPT and shear wave velocity data (simplified calculations A.9.4.6.5.2), or preferably by  Using a non-linear Site Response Analysis (see for example Stewart and Kwok (2008)[171]) including pore pressure development (more detailed time history analyses A.9.4.6.5.3). A detailed assessment should be performed as part of an ALE assessment (A.10.7.4) unless the likelihood of triggering of liquefaction is assessed as low. More information can be found in ISO 19901-2, ISO 23469 and EN 1998-5:2004. A.9.4.6.4 Assessment of site susceptibility to liquefaction The first consideration in a hazard evaluation is the assessment of site's susceptibility to liquefaction as can be determined by historical, geological, compositional and stress state criteria, see Kramer (1996)[121]. An evaluation of the site susceptibility to liquefaction should be made when the foundation soils include layers or thick lenses of loose to medium dense sands and non-plastic silts. Case histories indicate that liquefaction usually occurs within a depth of 20 m or less (Kramer (1996)[121], Boulanger and Idriss (2016)[30]). For many years liquefaction was thought to be limited to sands. However, liquefaction of non-plastic silts has been observed and therefore plasticity characteristics are of significance. Coarse silts which are non-plastic and with bulky particles are at risk of liquefaction; clays are non-susceptible. Well graded soils are generally less susceptible than poorly graded soils and soils with rounded grains have a greater tendency to contract and therefore liquefy under cyclic loading. Dense sands are less susceptible to cyclic loading and to the accumulation of strains and displacements. According to Boulanger and Idriss (2006)[27], soils with fines content less than 35% can be susceptible to liquefaction. The liquefaction hazard may be neglected (Eurocode 8 [EN 1998-5:2004]) if peak ground acceleration (at the sea floor) is less than 1,5 m/s2 (0,15g) and at least one of the following conditions is fulfilled: . No further reproduction or distribution permitted. Printed / viewed by: 199 a) the soil has a clay content greater than 20% with plasticity index greater than 10; b) the strata has cone tip resistance, normalized with respect to atmospheric pressure, greater than 180 and shear wave velocity greater than 250 m/s. Historical assessment is useful for seismic studies, since it is known that susceptibility is dependent on magnitude and proximity to the earthquake epicentre. Geological assessment is useful since soils that are loose and of uniform grain size are most susceptible. Therefore, fluvial soils of Holocene age are more susceptible than Pleistocene deposits. In general, older deposits are less susceptible than younger deposits. Furthermore, the applied cyclic shear stresses from historical wave loading and low-level earthquakes over time can reduce the risk of liquefaction, Sassa and Sekiguchi (1999)[161], Clukey et al. (1989)[53]. A.9.4.6.5 Simplified free-field assessment of liquefaction A.9.4.6.5.1 General Free-field liquefaction can occur when the earthquake induced Cyclic Stress Ratio exceeds the Cyclic Resistance Ratio of a soil layer. An initial screening assessment of the margin against triggering of liquefaction can be performed based on simplified methods. Two approaches are given in the following subclauses. The simplified methods provide a ratio of normalized cyclic resistance ratio λCRR over normalized cyclic stress ratio λCSR giving a margin against triggering of liquefaction, i.e. ftrig = λCRR/λCSR A factor ftrig larger than 1,0 typically implies no liquefaction. However, these methods are approximate (Pyke and North, 2019[152]) and should be used only as a screening tool (Pyke, 2015)[150]. Even if liquefaction is not triggered, the soil can exhibit reduction in strength and/or stiffness due to increases in pore water pressure. The effects of these increases in pore water pressure should be accounted for during evaluations of stability and settlement. Simplified methods for evaluating liquefaction-induced liquefaction and settlement are adversely affected by the fact that cone penetration resistance provides only an indirect indication of the response of soils to cyclic loading, especially if the soils contain clayey fines. Transition and thin layer effects, the use of peak ground accelerations at the sea floor, standard depth reduction and magnitude weighting factors, and the failure to account for excess pore pressure redistribution and dissipation will add to the uncertainty in the results. External factors, such as discontinuous sand layers, the thickness of any overlying “crust”, and partial saturation, are not considered in simplified methods. These various shortcomings are discussed in more detail by Pyke and North (2019)[152]. Effects from the spudcan footing, such as stresses from the structure and its dynamic response, drainage conditions, preloading, consolidation etc., can also affect liquefaction susceptibility. These effects are not included in these simplified methods. The above limitations and effects should be considered in the assessment of earthquake-induced liquefaction. Liquefaction-induced ground deformations should also be considered. A.9.4.6.5.2 Cyclic shear stress ratio and cyclic resistance ratio Simplified methods Seed and Idriss (1971)[165], Idriss (1999)[101], Youd et al. (2001)[210], Zhang et al. (2002)[214], Idriss and Boulanger (2006)[105] can be used to further assess the free-field liquefaction potential within the upper part of the soil profile by estimating the normalized cyclic stress ratio (λCSR ) and comparing it to the normalized cyclic resistance ratio (λCRR) computed from cone penetration test . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 200 © ISO 2023 – All right reserved resistance (Moss et al., 2006[139]; Boulanger and Idriss, 2016[30]) or in situ shear wave velocity (Kayen et al., 2013[115]; Robertson, 2015[156]). Possible free-field liquefaction assessment methods to calculate the ratio of λCRR over λCSR are provided in Annex E.5. A.9.4.6.5.3 Site response analysis A non-linear site response analysis (including softening) in combination with pore pressure development calculations can give a more realistic value of liquefaction, as discussed in Pyke and North (2019)[151]. Ideally, this will also be a bi-directional analysis which uses both horizontal components of motion as input (Pyke, 2019)[151], Hashash et al. (2010)[89], Olson et al. (2020)[143]. A.9.4.6.6 Detailed analysis In ALE Stage 3 time-history analyses the effects of the presence and dynamic response of the jack-up are considered with the jack-up footings supported by a soil model, such as in Galanes-Alvarez et al. (2020)[76]. See also 10.10 and A.10.7.4. Vertical settlement of the soils under the applied spudcan load should be considered for each leg of the jack-up. The differential displacements between the legs can be critical to structural stability and should be evaluated. Detailed analyses are also recommended to evaluate “lateral spreading” if the site is located on or near sloping ground. Lateral deformations could potentially cause stability issues for the jack-up. Consideration of lateral deformations can be important when surface layers are decoupled from deeper layers as a result of liquefaction of intermediate layers see Zhang et al. (2004)[215]. This decoupling can occur whether the sea floor is sloped or level. A.9.4.6.7 Liquefaction-induced lateral flows The potential for liquefaction-induced lateral flow in the vicinity of the jack-up should be considered, see A.6.5.1. A.9.4.7 Scour The key conditions for scour are  hydrodynamic conditions,  flow disturbance due to presence of an obstruction, and  potential for erosion of the sea floor material. For the hydrodynamic conditions, the combination of tidal and non-tidal current velocities (e.g. storm-driven currents) are key parameters, so that the effects of scour can increase rapidly during storms, particularly when the two contributions are aligned. The maximum depth of scour adjacent to the spudcan is related to the dimensions of the obstruction introduced, e.g. the spudcan itself, the spudcan in combination with the leg structure and/or adjacent infrastructures. Particle size has a strong influence on the erodibility; see Figure A.9.4-2. Particle sizes larger than those of the original sea floor, such as gravels and cobbles can be useful for scour protection. . No further reproduction or distribution permitted. Printed / viewed by: 201 Scour is more important for spudcans with limited sea floor penetration, as removal of the soil can result in the following:  a redistribution of leg forces or loss of jack-up hull trim;  a reduction of the bearing capacity of the foundation and seabed fixity;  eccentricity in the spudcan reaction;  an increase in an existing potential for punch-through in layered soils. There is no definitive procedure for the evaluation of scour potential, but useful reference material can be found in Sweeney et al. (1988)[177]; Whitehouse (1998)[201] and Rudolph et al. (2005) [158]. Previous operational experience can help in the management of scour, either in the development of scour protection measures or of an awareness of the critical combination of tidal and non-tidal (storm driven) currents that can induce scour. Scour protection measures include the following: a) gravel dumping prior to installation, provided the selected gravel gradation does not cause damage to the jack-up spudcans: Particularly for the larger materials, care should be taken to ensure that this activity does not adversely affect future jack-up emplacements; b) use of frond mats, gravel bags, gravel dumping or grout mattresses after installation, the effectiveness of which can be evaluated from scour surveillance monitoring; c) monitoring and adjusting for reduction in hull elevation. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 202 © ISO 2023 – All right reserved Key X particle size, expressed in millimetres Y mean flow velocity, expressed in metres per second 1 erosion 2 transport/erosion 3 transport 4 sedimentation/transport 5 sedimentation Figure A.9.4-2 — Soil particle size and seabed mobility [after McDowell and O'Connor (1977)[137]] A.9.4.8 Spudcan interaction with adjacent infrastructure The interaction of the spudcans with adjacent infrastructure can be addressed with reference to the literature, e.g. Siciliano et al. (1990)[168], Stewart (2005)[171], Leung et al. (2006)[127], and Kellezi et al. (2005b)[117]. A.9.4.9 Geohazards Certain areas of the world, including the US, require shallow geohazard surveys and publish documents that can give some useful guidance, e.g. US Department of the Interior Minerals Management Service (2008)[192] and IOGP (2009)[107]. It is important that the work is planned, performed and assured by qualified geohazard specialists to ensure that it is fit-for-purpose and meets the actual regulatory requirements of the host country. See also ISO 19901-10. A.9.4.10 Carbonate material No guidance is offered. A.10 Guidance on structural response A.10.1 Applicability No guidance is offered. A.10.2 General considerations The ULS responses typically include overturning moments of the jack-up, reactions and displacements at the spudcans, horizontal deflections of the hull, the internal forces in the leg members and forces in the holding system. The responses should be obtained using appropriate combinations of functional actions, metocean or earthquake actions, and dynamic, second order and leg inclination effects with the action factors in Annex B. The application of actions is described in 8.8 and A.8.8. In 5.4.3, it is required that the analysis be carried out for a range of headings with respect to the jack-up such that the most onerous loading(s) for each item in the list above is/are determined. When determining the FLS response, the cumulative number of stress cycles should be used to estimate the fatigue lives of steel components (see 10.6). Clause 10 is specifically aimed at short-term operations where fatigue is typically not a consideration. However, fatigue response can be important for long-term applications of a jack-up (see Clause 11). A.10.3 Types of analyses and associated methods The extreme storm ULS response can be determined either by a two-stage deterministic storm analysis procedure using a quasi-static analysis that includes an inertial loadset (see A.10.5.2) or by a more . No further reproduction or distribution permitted. Printed / viewed by: 203 detailed fully integrated (random) dynamic analysis procedure that uses a stochastic storm analysis (see A.10.5.3). Table 10.3-1 gives a list of some of the references used in an extreme storm response analysis. A common approach can be to start with a relatively simple analysis and to increase the level of complexity if the simple method shows the jack-up is unsuitable for the site. Table A.10.3-1 — Cross references for extreme storm responses Topic Reference location Comments and additional references Metocean action calculation procedure Table A.7.3-1 A.7 discusses actions, but Table A.7.3-1 gives an overview of the calculation procedure and gives references to the required input data, methods of calculating actions, and action factors. Structural model A.8 Table A.8.2-1 discusses the levels of detail in different structural models, and the information that can be obtained from them. A.8.3 to A.8.5 discuss modelling of the legs (including some simplified methods for calculating equivalent leg stiffness properties), the hull, and the leg to hull connection, respectively. A.8.7 discusses mass modelling. Action factors 8.8 Action factors are given for both the two-stage, and one-stage stochastic storm analysis. Application of actions A.8.8 Wind and wave/current actions are determined through use of A.7.3. A.8.8 discusses application of actions, including functional actions, hull sagging, metocean actions, and inertial actions. Additional load cases that should be considered when (Tn/Tp) > 0,9, are given in A.10.5.2.2.3. Large displacement effects A.8.8.6 Different modelling techniques are discussed, including large displacement methods, geometric stiffness methods and negative springs. Conductor actions A.8.8.7 — Damping A.10.4.3 Table A.10.4-1 gives recommended explicit damping levels. A.7.3.3.2 describes relative velocity hydrodynamic damping and Formula (A7.3-15) gives the specific limits for when relative velocity formulation may be used. A.10.4.3.3 describes the hysteretic foundation damping that may be used in certain cases. Two-stage deterministic storm analysis A.10.5.2 In this method, a DAF is calculated and used to develop an inertial loadset that is combined with the maximum quasi-static wave action. The DAF can be from an SDOF analysis (A.10.5.2.2.2) or a random dynamic analysis (A.10.5.2.2.3). Figure A.10.4-2 gives an overview of a two-stage approach incorporating foundation fixity, which is normally included in the analysis. A.10.4.4.1.2 gives foundation modelling for a two-stage analysis. SDOF analysis A.10.5.2.2.2 This method is very simple and often used for a first pass assessment, but it has a limited range of applicability and, while normally conservative, can underestimate the DAF. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 204 © ISO 2023 – All right reserved Topic Reference location Comments and additional references Random dynamic analysis A.10.5.2.2.3 Commonly used to develop the dynamic response and then the DAF in a two-stage analysis Sets out the metocean and inertial loadset components of the basic load case that should be assessed for all values of (Tn/Tp), and the extra load cases that should be considered when (Tn/Tp) > 0,9 Table A.7.3-3 gives specific recommendations on qualifying storm simulations. A.6.4.2.3 gives information on wave spreading using either three-dimensional analysis or a kinematics reduction factor. ISO 19901-1:2015, 8.4.4 and A.8.4.3, give information on the intrinsic and apparent wave periods, and the methodology for modifying the wave spectrum from intrinsic to apparent. A.10.5.3.3 gives additional details on all random wave dynamic analyses, regardless of whether it is for a one-stage or two-stage assessment. A.10.5.3.4 gives information on determining the MPME response, which is the result of the random analysis. Table A.10.5-1 gives recommendations for calculating the MPME and on the storm duration to use in the simulations. Stochastic storm analysis A.10.5.3 In this method, the MPMEs of the responses of interest (e.g. member utilizations) are determined directly in a one-stage analysis, although multiple one-stage dynamic analyses can be required (10.5.3). DAFs are not specifically developed. A.10.5.3.2 describes the determination and application of partial factors to the metocean parameters, as required in 10.5.3. Figure A.10.5-4 shows the analysis procedure for a one-stage stochastic storm analysis including foundation fixity. A.10.5.3.4 describes the determination of MPME responses. Leg inclination A.10.5.4 The effect of leg inclination is included in the structural code checks, but not in the global response analysis. A.10.4 Common parameters A.10.4.1 General The ULS response can be calculated either by using a quasi-static analysis procedure including an inertial loadset or by using a more detailed (random) dynamic analysis procedure. Clause 8 and A.8 identify the factors that affect the structural stiffness of the jack-up and discuss the structural stiffness modelling at various levels of complexity. The actions are discussed in Clause 7 and A.7. The magnitude of the dynamic response is affected by the following: a) the dynamic characteristics (natural periods) of the structural system formed by the jack-up on its foundation; b) the characteristics of the excitation. For metocean excitation at sites with high current, there can be significant contributions from higher order harmonics in addition to those normally associated with quadratic drag terms and free surface effects. The factors that affect these two characteristics are discussed in A.10.4.2 to A.10.4.5 . No further reproduction or distribution permitted. Printed / viewed by: 205 A.10.4.2 Natural periods and affecting factors A.10.4.2.1 General The natural period of the jack-up on its foundation in the fundamental (or first) mode of vibration is an important indicator of the degree of dynamic response to be expected. The first and second vibrational modes are normally the surge and sway modes. The natural periods of these vibrational modes are usually close together; which of the two is the higher depends on which direction is less stiff. Where the natural or wave period varies with heading, care should be taken that the periods used are applicable to the direction being considered in the analysis. The third vibrational mode is normally a torsional mode, the three-dimensional effects of which can be important, in particular for headings where the legs and, hence, wave actions are not symmetric about the direction of wave propagation. The natural period is dictated by the characteristics of the structural system, which are governed by the overall (global) structural stiffness, the mass and mass distribution, and the damping. The undamped natural period is determined from Formula (A.10.4-1): n2(/)TMK=π (A.10.4-1) where Tn is the first natural period of surge or sway motion of the jack-up; M is the effective system mass; K is the effective system stiffness. ISO/TR 19905-2 contains a manual method for calculating the natural period. The method is not recommended for use in analyses but is useful for demonstrating some of the factors that affect the natural period of a jack-up. A.10.4.2.2 Stiffness The jack-up on its foundation represents a multi degree-of-freedom system. If available, a finite element structural model, containing the mass and stiffness properties of the jack-up should be used to obtain the various natural periods and mode shapes. Structural modelling at various levels of complexity is discussed in A.8 and should consider stiffness contributions from the following: a) bending deformation of the legs; b) shear deformation of the legs; c) axial deformation of the legs; d) hull bending deformation; e) horizontal vertical and rotational leg-to-hull connection stiffness; f) horizontal, vertical and rotational foundation stiffness; g) second order P-Δ due to lateral displacement of the hull; The model can contain a number of non-linear elements, notably the leg-to-hull connections and the spudcan-foundation interfaces. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 206 © ISO 2023 – All right reserved The system stiffness for the fundamental modes can be estimated from an idealized single degree-of-freedom system as described in ISO/TR 19905-2. The method is not recommended for use in analyses but is useful for demonstrating some of the factors that affect the natural period of a jack-up. A.10.4.2.3 Mass No guidance is offered. A.10.4.2.4 Variability in natural period No guidance is offered. A.10.4.2.5 Cancellation and reinforcement A.10.4.2.5.1 General If the legs of the jack-up were lumped together at one position, waves passing through would cause each leg to have the same applied force history and the base shear transfer function (base shear versus wave period) would be a relatively smooth function. Assuming the leg kinematic parameters are axisymmetric, this transfer function would be the same for all wave headings. As the legs are moved apart, at an instant in time the wave position relative to each leg is different for each wave period. Since each leg is at a different phase for each wave period, the amplitude of the base shear transfer function at every period is bounded by the value with all legs together. Essentially, there is some force cancellation for almost all periods (smaller amplitudes than all legs together). Since the spacing between the legs changes by approach direction, different wave headings also result in different base shear transfer functions, even if the kinematic properties are still axisymmetric. Figure A.10.4-1 shows cancellation and reinforcement periods. It can be used for a first evaluation of the position of the calculated natural period(s) relative to the cancellation and reinforcement points in the global loading. These can be characterized by the total horizontal wave loading or by the overturning moment; cancellation and reinforcement of points for these can occur at slightly different wave periods. The assessor should aim to maximize the overall jack-up responses and not just, for example, the DAF. The DAF calculated through the SDOF is independent of cancellation and reinforcement. A.10.4.2.5.2 Quasi-static deterministic waves Care should be taken to avoid cancellation in the quasi-static deterministic wave actions. This is not normally an issue; rarely is the extreme storm wave period close to a cancellation period, but if it is, a range of wave periods should be investigated (see A.6.4.2.9 and A.6.4.2.3). A.10.4.2.5.3 Stochastic dynamic wave response The natural period(s) used in the dynamic analysis should be selected such that a realistic but conservative value of the dynamic response is obtained for the particular application envisaged. Care should be taken to ensure that the response is maximized, not just the dynamic amplification, since it is possible to have a large DAF combined with low metocean excitation, due to cancellation, leading to low combined response. When the DAF is determined through a stochastic analysis, care should be taken to minimize cancellation (see also A.7.3.3.3.3) as this can result in significant underestimation of the DAF. In a two-stage stochastic analysis, the DAF is determined as the ratio of the responses of two models (see A.10.5.2.2.3): one that includes and one that excludes dynamic effects. A significant percentage of the dynamic effect is due to excitation of the natural period of the jack-up by that component of the wave trace having that same period. If there is cancellation at that period, there is little excitation, so the calculated DAF is unrealistically small. . No further reproduction or distribution permitted. Printed / viewed by: 207 Care should also be taken when there is significant current velocity as this can lead to slightly different cancellation effects. When combining current with a cyclic Morison wave loading, the drag term causes a harmonic excitation at half the wave period. This second harmonic can result in significant dynamic excitation, especially when the current is large and the period of the second harmonic is the same as the natural period. If cancellation of the second harmonic actions occurs, the DAF can be significantly underestimated. In order to prevent cancellation resulting in potential underestimation of the DAF, the range of possible natural period(s) should be bracketed and compared with the relevant cancellation points in the global wave loading and the second harmonic of the wave period. When the natural period occurs at a cancellation point in the transfer functions, the mass or stiffness should be adjusted in a logical manner to move the natural period away from the cancellation point. This generally ensures that the dynamic response is maximized within reasonable limits. The definitive selection of natural period(s) should be based on the shape of the global horizontal wave loading (base shear) and overturning moment transfer functions for the case under consideration. If the analysis is for pinned spudcans with maximum hull mass, then the adjustment should be made by reducing the hull mass (within the normal range) and/or by introducing a degree of rotational fixity at the seabed. If the analysis is for a case with a degree of spudcan moment fixity, then the adjustment can most logically be made by varying the degree of rotational fixity at the seabed. Alternatively, when the metocean data is omni-directional, the effects of wave spreading can be used to reduce the effects of cancellation by carrying out the dynamic analysis for a single wave heading along an axis which is neither parallel nor normal to a line through two adjacent leg centres. Thus, for a 3-legged jack-up with equilateral leg positions and a single bow leg, suitable analysis headings can be with the environment approaching from approximately 15° or 45° off the bow. The DAFs should be determined for one, or both, of these headings. The DAFs (or more conservative DAFs) can then be applied to the final quasi-static analysis for all headings. In a one-stage stochastic analysis, similar care should be taken to avoid cancellation effects at both the natural period and at the predominant wave spectral energy. Figure A.10.4-1 presents the periods at which first and second cancellations and reinforcements occur in the total wave actions. It is valid for the main wave directions of 3- and 4-legged jack-ups in water depths exceeding 30 m. The potential for increased response due to short-crested waves should be considered (see A.7.3.3.3.3). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 208 © ISO 2023 – All right reserved Dimensions in metres a) Sample of wave period in relation to wave force cancellation and reinforcement at all phase angles, including diagrammatic arrangement of jack-up legs with wave length b) Horizontal action on jack-up versus wave frequency showing reinforcement and cancellation Figure A.10.4-1 — Periods for wave force cancellation and reinforcement as a function of leg spacing (1 of 2) . No further reproduction or distribution permitted. Printed / viewed by: 209 c) Diagrammatic arrangement of legs on 3-legged jack-up in beam seas that can result in complete horizontal wave action cancellation at all wave phase angles Key 1 3 legged jack-up 2 4 legged jack-up 3 wave direction versus leg locations associated with wave action curve 5 4 wave direction versus leg locations associated with wave action curve 6 5 indicative curve of wave action on jack-up versus frequency due waves in directions 3 6 indicative curve of wave action on jack-up versus frequency due waves in directions 4 7 first reinforcement point 8 second reinforcement point 9 first cancellation point 10 second cancellation point A static wave action on jack-up f wave frequency t wave period S jack-up leg spacing a First wave force cancellation over all wave phase angles; water depth ≥ 50 m. b First wave force reinforcement over all wave phase angles; water depth ≥ 30 m. c Second wave force cancellation over all wave phase angles; water depth ≥ 30 m. d Second wave force reinforcement over all wave phase angles; water depth ≥ 30 m. NOTE 1 Figure A.10.4-1 a) has been drawn for effectively deep water cases only. The reduced wave length in shallow water results in slightly longer wave periods producing first cancellation. NOTE 2 On a 4-legged jack-up, it is possible to get complete cancellation of the horizontal actions at certain wave lengths (e.g. in a wave of specific length that results in two legs at the wave crest and two at the wave trough, as shown by line 'a' in Figure A.10.4-1 a). It is not possible to get complete cancellation of the horizontal actions on a 3-legged jack-up oriented with two legs parallel to the wave crest. There is partial cancellation in waves that result in one leg at a trough when two legs are at a crest, as shown by line 6 of Figure A.10.4-1 b), but there is not sufficient cancellation in any wave length to result in line 5. It can be possible to get complete cancellation on a 3-legged jack-up oriented with any two legs parallel to the direction of wave propagation, as shown in Figure A.10.4-1 c), but it is not for precisely the wave periods given in Figure A.10.4-1 a). Figure A.10.4-1 — Periods for wave force cancellation and reinforcement as a function of leg spacing (2 of 2) . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 210 © ISO 2023 – All right reserved A.10.4.3 Damping A.10.4.3.1 General The main components of system damping are foundation, hydrodynamic and structural damping. Each of these can be modelled either linearly or non-linearly and can be calculated as part of the analysis or input as a percentage of critical damping (see Table A.10.4-1). Structural damping is normally modelled linearly and input as a percentage of critical damping, however there are non-linear components (e.g. gaps in guides, pinion backlash). Hydrodynamic damping is mainly due to fluid-structure relative velocity effects (see A.7.3.3.2); alternatively, a percentage of critical damping can be applied. Foundation damping comprises three components: small strain material, hysteretic and radiation damping. The small-strain soil material damping is typically small. At larger strains, amplitude-dependent hysteretic damping can also occur. Where a non-linear foundation model is adopted for dynamic response analysis, the hysteretic foundation damping and soil stiffness reduction are accounted for directly. Where linearized soil stiffness is used in a time domain analysis, hysteretic damping should not be included. A.10.4.3.2 Linear system damping Where the model relies on damping defined as a percentage of critical, the total linear system damping should not exceed 7 % without credible, applicable justification. Lower values can be appropriate for fatigue analyses and lower sea states. Care should be taken to avoid the duplication of damping components when explicit and implicit representations are used simultaneously in the analyses. Table A.10.4-1 summarizes typical upper bounds when using percentages of critical damping. Table A.10.4-1 — Recommended explicit damping from various sources Damping source Global linear damping not to exceed (% of critical damping) Structure, holding system, etc. 2 Small strain foundation 2a Hydrodynamic 3 or 0b a The small-strain soil material damping is typically small; in the absence of specific data, 2 % is considered to be a reasonable estimate. b In cases where the relative velocity formulation is used [α = 1 in Formula (A.7.3-15)], the hydrodynamic damping is accounted for directly and should not be included as a percentage of critical damping. A.10.4.3.3 Hysteretic damping Foundation hysteretic damping can, in certain situations, increase the 2 % small-strain foundation damping given in Table A.10.4-1 and is discussed further in ISO/TR 19905-2. A.10.4.3.4 Vertical radiation damping in earthquake analysis In earthquake analyses, the foundation radiation damping from wave propagation can be included for vertical motion of the spudcan in addition to other foundation damping. Radiation damping should not normally be used in extreme storm or fatigue jack-up assessments. Radiation damping effects are implicitly included when the dynamic foundation analysis is performed using a continuum finite element analysis with a model that can accurately capture the effects of wave propagation in the foundation soils. Additional information on radiation damping is given in ISO/TR 19905-2. In simpler analyses, the vertical foundation radiation damping can be estimated from the work of Lysmer and Richart (1966)[130], as given in Formula (A.10.4-2): . No further reproduction or distribution permitted. Printed / viewed by: 211 Crd = R [0,85 B2/(1 − ν)] √(Goρs) (A.10.4-2) where Crd is the radiation damping coefficient of a dashpot (force per unit velocity); R is a reduction factor applied to avoid unconservatism, which should normally be taken as 0,5; B is the effective spudcan diameter at uppermost part of bearing area in contact with the soil; ν is Poisson's ratio (of the foundation soil); Go is the shear modulus of the foundation soil [for clay, Go = Gmax, the maximum value of the shear modulus, that occurs at small strain (see A.9.3.4.3); for sand, Go = Gmax, the initial small-strain shear modulus (see A.9.3.4.4)]; ρs is the total, saturated, (mass) density of the foundation soil. In non-linear dynamic analyses, or in linear time domain dynamic analyses using direct integration, Formula (A.10.4-2) can be used directly to establish the damping coefficients for the foundation dashpots. In linear modal dynamic analyses, the additional contribution of vertical radiation damping to the linear damping ratio for the vertical mode only can be calculated as given in Formula (A.10.4-3): ζrd = R 0,213 Ns B ωn √(ρs/Go) (A.10.4-3) where ζrd is the radiation modal damping ratio to account for spudcan vertical motion; Ns is the number of spudcans; ωn is the angular natural frequency of the vertical mode, expressed in radians per second. NOTE 1 The suggested value of 0,5 for R is a reduction on the amount of radiation damping and is comparable with values used in other industries. The reduction is intended to account for the frequency dependence and spatial variance (e.g. stratification) in soil conditions below the spudcan. NOTE 2 Formula (A.10.4-2) is obtained by combining the definition of the damping coefficient, C, with the damping ratio of Formula (A.10.4-3) and the corresponding formula for stiffness given by Lysmer and Richart (1966)[130]. NOTE 3 Radiation damping increases with increasing excitation frequency. Radiation damping levels from ocean wave excitation are expected to be less than 1 %, whereas for earthquake actions, radiation damping ratios can be large (>10 %). Radiation damping values this large can have significant effects on dynamic response. A.10.4.4 Foundations A.10.4.4.1 Foundations for extreme storm assessment A.10.4.4.1.1 General A.10.4.4.1 describes the analysis of the structure and the foundation evaluation which can be performed in two different ways: . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 212 © ISO 2023 – All right reserved  option 1: deterministic two-stage approach;  option 2: stochastic one-stage approach. A.10.4.4.1.2 Option 1 — Deterministic two-stage approach Figure A.10.4-2 illustrates the procedure schematically. In this approach, the dynamic response of the structure is evaluated based on either a simple linear analysis or a more complex elasto-plastic analysis in order to determine an inertial loadset. The dynamic analysis can include linearized springs. Typically, the initial linearized rotational stiffness for the dynamic analysis can be taken as 80 % of the value determined from A.9.3.4.1. This simplified approach does not capture the temporary reductions in stiffness that occur during plasticity events (generally with detrimental effects), but also does not capture the increased damping associated with these events (with beneficial effects). The foundation and structural assessment is next performed using a quasi-static, iterative analysis technique, for which the dynamic actions have already been determined. This quasi-static analysis can be accomplished by means of either an elasto-plastic foundation model or by a simplified application of the full plasticity analysis as described below. This simple approach is used to apply moments on the spudcan by inclusion of a simple linear rotational spring. The moments thus applied are limited to a capacity based on the yield interaction relationship between the gross vertical force (FV), the horizontal force (FH) and the moment (FM) acting on the spudcan. This simple procedure is described in the following steps (see the right hand side of Figure A.10.4-2). a) Include vertical, horizontal and (initial) rotational stiffnesses (using linear springs, see A.9.3.4.1) in the analytical model and apply the factored functional and factored metocean actions together with the associated and separately calculated inertial loadset from a linearized dynamic analysis, to determine the resulting forces FH, FV and the moment FM on each spudcan. b) Calculate the value of the yield interaction function (see A.9.3.3) using the resulting forces on each spudcan. If the value is zero, the force combination falls on the yield surface; for values greater than zero, it is outside; and for values smaller than zero, it is inside the yield surface. c) If a force combination initially falls within the yield surface, the rotational stiffness should be further checked to satisfy the reduced stiffness conditions in A.9.3.4.2. d) If the force combination initially falls outside the yield surface, the rotational stiffness should be arbitrarily reduced and the analysis should be repeated until the force combination at each spudcan lies essentially on the yield surface. If at that point the moment is reduced to zero and the force combination is still outside the yield surface, then a bearing failure (either vertical or horizontal) is indicated. e) Additional penetration due to a bearing failure can result in increased foundation capacity, which, in turn, expands the yield interaction surface. See A.9.3.3.5 and A.9.3.3.6 for guidance on expansion of yield interaction surface and A.9.3.6.6 for guidance on the displacement check. . No further reproduction or distribution permitted. Printed / viewed by: 213 Figure A.10.4-2 — Analysis procedure for two-stage assessment with foundation fixity — Option 1 A.10.4.4.1.3 Option 2 — Stochastic one-stage approach Figure A.10.5-4 illustrates the procedure schematically. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 214 © ISO 2023 – All right reserved In this approach, the dynamic structural analysis and assessment is performed using one model. A fully detailed, non-linear time domain analysis is performed taking into account the elasto-plastic behaviour of the foundation. The effects of the foundation fixity on the dynamic response and on the foundation reactions are simultaneously considered. This approach is more complete and often requires a complex incremental and iterative calculation procedure. The following outline procedure can be used. a) Use a time domain random dynamic analysis to determine structural response and foundation forces at each time step. b) Determine the foundation behaviour using a non-linear elasto-plastic model, such that at each time step the plastic and elastic portions of the behaviour are captured. If desired, this model can include hysteresis. This is likely to require an iterative procedure. c) As the dynamic response is influenced by the time history of the actions, a number of random dynamic analyses should be performed for differing input wave histories, and the MPMEs determined from a procedure described in A.10.5.3.4. If, due to wave force cancellation effects, small changes in foundation stiffness result in significant changes in the response, the foundation stiffness should be selected with care to maximize the response (see A.10.4.2). A.10.4.4.2 Foundations for earthquake assessment For the simple screening assessment, the foundation should be modelled with a high representative value of 𝐺𝐺o from Clause 9, without degradation but with appropriate rate adjustments. For more detailed assessments, a fully non-linear coupled yield interaction model or a continuum model should be used with degradation effects. A.10.4.5 Storm excitation Currents change slowly compared with the natural periods at which jack-ups oscillate and can be considered to be a steady phenomenon. Variations in wind velocity cover a wide range of periods, but the main wind energy is associated with periods that are considerably longer than the natural periods of jack-up oscillations. Therefore, the wind can generally also be represented as a steady flow of air. The periods of waves typically lie between 3 s and 20 s. Since natural periods of jack-up in typical applications fall within this range, the primary source of dynamic excitation is from waves. Sea waves are not regular but random in nature, with a more predominant periodicity when a swell is present. This has important implications that should be considered for both the dynamic excitation and the resulting dynamic response. A.10.5 Storm analysis A.10.5.1 General No guidance is offered. A.10.5.2 Two-stage deterministic storm analysis A.10.5.2.1 General In the first stage, an inertial loadset is determined from a dynamic amplification factor using either a single degree-of-freedom analogy (K DAF,SDOF), see A.10.5.2.2, or a random wave time domain random . No further reproduction or distribution permitted. Printed / viewed by: 215 dynamic analysis (KDAF,RANDOM), see A.10.5.2.2.3. In the second stage, the maximum quasi-static wave/current action is determined by stepping the maximum wave through the structure. The maximum wave/current action is then combined with the inertial loadset to determine the responses. The maximum wave is defined in 6.4 and the methodology for calculating the quasi-static wave/current actions is described in 7.3. Load cases and combinations are discussed in 8.8. The spudcan-foundation interface can be modelled as described in 9.3.1. A.10.5.2.2 Dynamic amplification factors (DAFs) and inertial loadsets A.10.5.2.2.1 General When using a deterministic analysis for calculating the jack-up's responses, the dynamic response is represented by equivalent inertial actions as described in A.8.8.5. The inertial loadset can be derived from the classical SDOF analogy described in A.10.5.2.2.2, or from the more complex random dynamic analysis method discussed in A.10.5.2.2.3; see Figure A.10.5-1. It should be recognized that dynamic amplification is the result of inertial actions that are dominated by the hull mass. Therefore, amplifying the hydrodynamic actions is not a correct physical representation. NOTE The difference between the height of the applied wave actions and the height of the system centre of mass means that the global response (e.g. base shear, overturning moment, hull deflection) and local response (e.g. member forces, holding system reactions, spudcan reactions) are not equally amplified by the inertial actions. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 216 © ISO 2023 – All right reserved Fin = (KDAF,SDOF − 1)[ABS(t)static] where ABS(t)static is the amplitude of FBS(t)static, is equal to 0,5(FBS,max − FBS,min) a) SDOF KDAF,RANDOM = RMPME,dynamic/RMPME,static Fin = (K DAF,RANDOM − 1) Fstatic b) Stochastic/random Key t time BS base shear Y normalized stochastic response FBS,min minimum static base shear 1 static response FBS,max maximum static base shear 2 dynamic response Fin magnitude of inertial loadset 3 mean of static response Fdynamic magnitude of total dynamic loadset RMPME,static stochastic response Fstatic magnitude of total static loadset RMPME,dynamic stochastic response RBS base shear response Figure A.10.5-1 — Dynamic amplification factors . No further reproduction or distribution permitted. Printed / viewed by: 217 A.10.5.2.2.2 The classical SDOF analogy (K DAF,SDOF) This representation assumes that the jack-up on its foundation can be modelled as an equivalent single degree-of-freedom mass-spring-damper mechanism. The (highest) natural period of the jack-up's vibrational modes can be determined as described in A.10.4.2. The torsional mode and corresponding three-dimensional effects cannot be included in this representation. The SDOF method is fundamentally empirical because:  the wave/current action does not occur at the hull;  the excitation is non-periodic (random) and non-linear. The method described below generally leads to an approximation of the jack-up's real behaviour that has been calibrated against more rigorous methods. The following cautions are noted when using the SDOF method. a) If the ratio of the jack-up natural period to the wave excitation period, Ω, is in the range 0,4 to 0,8 and the current velocity is small relative to the wave particle velocities, the SDOF method can give reasonable results, subject to items b) to d) below. b) The SDOF method does not account for reinforcement, as discussed in A.10.4.2.4, and this can make the method unconservative, particularly when Ω > 0,5. When Ω > 0,5, there can be significant energy in an irregular sea at the jack-up natural period, and this is not accounted for in the SDOF method because the DAF is not affected by any periodicity other than the excitation at 0,9Tp. This lack of excitation is particularly important when the jack-up natural period is close to a wave reinforcement point. In this case, the resonant response, combined with reinforcement, can result in a significantly higher action than that calculated from the SDOF method. In the calculation of the natural period, a range in foundation fixity should be considered as this variability can shift the jack-up natural period within the base shear transfer function, resulting in different dynamic amplifications. c) The SDOF method can be unconservative for cases where the current velocity is large relative to the wave particle velocities. If the results of the assessment are close to the acceptance criteria, further detailed analysis is recommended. d) The SDOF method can be unconservative and should not normally be used in an extreme storm assessment when Ω is greater than 1,0, i.e. when Tn > 0,9Tp. However, the SDOF analogy may be used when the calculated Ω is greater than 1,0 providing Ω is taken as 1,0. When using the SDOF method, a minimum value of 1,2 should be taken as the DAF in an extreme storm assessment, regardless of the DAF calculated using the SDOF method. NOTE The DAF calculated in the SDOF analogy (KDAF,SDOF) cannot be meaningfully compared to the DAF determined with a stochastic wave assessment (KDAF,RANDOM). This is because the methods for determining the relevant inertial loadsets are different, thus the same value of KDAF,SDOF and KDAF,RANDOM produce different total global responses; see Figure A.10.5-1. The ratio of (the amplitudes of) dynamic to quasi-static response as a function of frequency (ω) or period (T) steady state, periodic and sinusoidal excitation is calculated by means of the classical dynamic amplification factor (K DAF,SDOF) as given in Formula (A.10.5-1): DAF,SDOF222112012,()()KΩζΩ=≥−+ (A.10.5-1) . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 218 © ISO 2023 – All right reserved where Ω is the jack-up's natural period (Tn) divided by the wave excitation period (Tw); nw10,TTΩ=≤; ζ is the damping ratio or fraction of critical damping, ζ ≤ 0,07 (see A.10.4.3); Tw = 0,9Tp; Tp is the apparent peak wave period (modal or most probable period of the wave spectrum, corrected to account for current velocity; see A.7.3.3.5 and ISO 19901-1:2015, A.8.4.3); Tn is the natural period as derived in A.10.4.2.1. The damping parameter, ζ, in this model represents the total of all damping contributions (structural, hydrodynamic and foundation damping). For the evaluation of extreme jack-up responses using the SDOF method, a value not exceeding 0,07 is recommended. The calculated KDAF,SDOF from the SDOF analogy is used to estimate an inertial loadset, which represents the contribution of dynamics over and above the quasi-static response as illustrated in Figure A.10.5-1 a). The inertial loadset should be determined as given in Formula (A.10.5-2) and applied at the hull centre of gravity in the direction of wave propagation: Fin = (K DAF,SDOF − 1) FBS,Amplitude (A.10.5-2) where Fin is the magnitude of the inertial loadset; FBS,Amplitude is the single amplitude of quasi-static base shear over one wave cycle, FBS,Amplitude = [FBS,(QS)Max − FBS,(QS)Min]/2; FBS,(QS)Max is the maximum quasi-static wave/current base shear; FBS,(QS)Min is the minimum quasi-static wave/current base shear. Formula (A.10.5-2) is part of a calibrated procedure and should not be altered. A more general inertial loadset procedure, using the results from random dynamic analysis, is described in A.10.5.2.2.3. A.10.5.2.2.3 Inertial loadset based on random dynamic analysis (K DAF,RANDOM) In the time domain random dynamic analysis procedure, two DAFs are calculated, one for the BS and one for the overturning moment (OTM). The inertial loadset, Fin, is calculated from these DAFs. The BS and OTM DAFs are the ratios of the MPME of the dynamic BS/OTM to the MPME of the static BS/OTM (RMPME,dynamic/RMPME,static), see Figure A.10.5-1 b), determined from corresponding dynamic and quasi-static time domain analyses for random-wave excitation according to the recommendations of the stochastic storm analysis in A.10.5.3. The MPME is defined in Table A.10.5-1. Damping effects, including relative velocity effects, should not be included in the quasi-static (zero mass) analysis. P-Δ effects should be included in both the quasi-static (zero mass) and the dynamic analyses. When P-Δ effects are included using negative springs, the same springs should be used in both analyses, although when calculating the BS DAF the shear force induced by the negative spring should be excluded. When . No further reproduction or distribution permitted. Printed / viewed by: 219 the P-Δ effects are developed from gravity actions, the effects of vertical gravity loads should be modelled in the zero-mass analysis, i.e. weight is included even though there is no mass. The inertial loadset, Fin, normally should be such that it increases both the BS and OTM from the deterministic quasi-static analysis by the same ratios as those determined between the random quasi-static (zero mass) analysis and the random dynamic analysis. In such cases, the structural model (used for dynamic analysis) may be simplified and it is not necessary that it contain all the structural details, but should nevertheless be a multi degree-of-freedom model. See A.8.8.5 for guidance on applying an inertial loadset to the model that matches both dynamic BS and OTM. Caution should be exercised when the wave period approaches resonance and additional load cases should be considered when (Tn/Tp) is greater than 0,9. These extra load cases account for the changing phase between the forcing action and the inertial action as (Tn/Tp) approaches and exceeds 1,0 (see Figure A.10.5-3 and NOTE 1). The basic load case is the inertial loadset applied in phase with, and to increase the response to, the metocean actions, Formula (A.10.5-4). This load case is required for all ratios of (Tn/Tp). Three additional load cases, Formulae (A.10.5-5) to (A.10.5-7), should be considered when (Tn/Tp) is greater than 0,9. Four sample load cases are shown diagrammatically in Figure A.10.5-3. In each case, the inertial loadset should be applied to the structure as described with A.8.8.5, using the same directional pair of KDAF,RANDOM values calculated for base shear and overturning moment. NOTE 1 Figure A.10.5-3 shows the phase between the forcing action and the inertial action for an SDOF system for varying values of Tn/Tp and represents the underlying reason the extra load cases are assessed in a two stage deterministic analysis when Tn/Tp is greater than 0,9. As the value of Tn/Tp increases beyond 0,9 the phase between the exciting action and the inertial action changes from being approximately in phase for low values of Tn/Tp, through being 90° out of phase when Tn/Tp = 1,0 to being approximately 180° out of phase when Tn/Tp is greater than 1,2. While Figure A.10.5-3 is drawn for an SDOF system, a similar phasing analogy can be made in a random dynamic analysis, albeit without the same degree of fine definition. It is because the phasing is not so well defined in a random sea state that the extra cases are specified above when Tn/Tp is greater than 0,9. The total base shear and overturning moment is the same in the first three load cases. Formulae (A.10.5-4 to A.10.5-6) provide a match to the base shear but it is still necessary to correct the overturning moment. Both the base shear and overturning moment can be different in the fourth case: Formula (A.10.5-7); see NOTES 5 and 6. The base shear inertial loadsets are calculated as given in Formula (A.10.5-3): Fin,PHASE(a) = KDAF,RANDOM FSTATIC − FSTATIC,PHASE(a) (A.10.5-3) and are applied in load cases as given in Formulae (A.10.5-4) to (A.10.5-7): [Ee + γf,D De](0) = FWIND + FSTATIC + γf,D Fin,PHASE(0) (A.10.5-4) [Ee + γf,D De](90) = FWIND + γf,D Fin,PHASE(90) (A.10.5-5) [Ee + γf,D De](180) = FWIND + FSTATIC.UP + γf,D Fin,PHASE(180) (A.10.5-6) [Ee + γf,D De](−180) = FWIND + FSTATIC − γf,D Fin,PHASE(−180) (A.10.5-7) where [Ee + γf,D De](a) is the combined metocean actions and inertial actions for use as (Ee + γf,D De) in Formula (8.8-1); . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 220 © ISO 2023 – All right reserved (a) is a subscript representing the notional phasing of the four different load cases given in Formulae (A.10.5-4) to (A.10.5-7) in which (a) is (0), (90), (180), and (−180), respectively (see NOTE 4); FSTATIC is the deterministic quasi-static wave/current loadset in the direction of the MPME values; FWIND is the wind loadset; FSTATIC,PHASE(a) is the deterministic quasi-static wave/current loadset for the relevant load case: it is equal to FSTATIC for the normal PHASE(0) case when used to calculate Fin,PHASE(0) in Formula (A.10.5-4), which represents the normal case with inertia down-wind and crest wave loading [see Figure A.10.5-2 a)]; when Tn/Tp > 0,9: it is equal to 0,0 for the PHASE(90) case when used to calculate Fin,PHASE(90) in Formula (A.10.5-5), which represents the inertia only load case [see Figure A.10.5-2 b)]; it is equal to FSTATIC.UP for the PHASE(180) case when used to calculate Fin,PHASE(180) in Formula (A.10.5-6), which represents the case with inertia down-wind and trough wave loading [see Figure A.10.5-2 c)]; it is equal to FSTATIC.UP for the PHASE(−180) case when used to calculate Fin,PHASE(−180) in Formula (A.10.5-7), which represents the case with inertia up-wind and crest wave loading [see Figure A.10.5-2 d)]; FSTATIC.UP is the deterministic quasi-static wave/current loadset in the up-wind direction (i.e. maximum upwind loadset, which is normally in the opposite direction to the wind action). Formulae (A.10.5-4) to (A.10.5-7) represent the metocean and dynamic components, Ee and De, in Formula (8.8-1). The gravity components GF and Gv should also be included when developing the complete assessment load case Fd in Formula (8.8-1). The response analysis should include P-Δ and hull sagging effects and the effects of leg inclination should be taken into account (see 7.8). NOTE 2 It is relatively unusual to undertake a jack-up assessment where Tn/Tp is greater than 1,0 but such situations do exist, e.g. in relatively benign conditions in deep water and with low spudcan fixity. Experience has shown that in some cases the introduction of additional spudcan fixity reduces the natural period to below the wave period and this action results in an increased DAF. NOTE 3 Formula (A.10.5-3) is a scalar formula. It is used to determine the magnitude of the inertial loadset, but has no associated point of action or direction. Formulae (A.10.5-4) to (A.10.5-7) are vector formulae in which, for example, the inertial loadset is applied in the relevant direction and at the relevant elevation above the seabed. NOTE 4 The subscript (a) is not the actual phase, but a notional, or indicative, phase taken from the SDOF analogy, similar to that given in Figure A.10.5-3, (in the full knowledge that the assessment is using a multi-degree of freedom model and loading). For example, PHASE(0) is not necessarily at the wave crest. It is simply used to represent the phase when the inertial loading is in-phase with the maximum down-wind wave/current action. Likewise PHASE(90) is used to represent the phase when the wave/current action is zero. PHASE(180) is used to represent the case when the inertia and direct wave/current actions are out of phase, with the inertial actions in the downwind direction and the wave/current actions, represented by the wave trough actions, in the up-wind . No further reproduction or distribution permitted. Printed / viewed by: 221 direction. PHASE(−180) is the reverse; the inertial actions are up-wind and the maximum wave/current actions are down-wind. NOTE 5 The same total vectored sum of the actions and moments that comprise (Ee + γf,D De)(a) is used in Formulae (A.10.5-4) to (A.10.5-6). In effect, the base shear and overturning moment are the same for all of the first three cases: Formulae (A.10.5-4) to (A.10.5-6). This is because the load cases are designed to represent different interpretations of the same results from the random time domain dynamic analysis. When assessing the results of such an analysis, a procedure is used to capture both the maximum base shear and the maximum overturning moment. It is possible that the relationship between these two values is not known (i.e. the maximum base shear can occur at a different time than the maximum overturning moment). It is, however, known that the values of both items are maximized. MPMEs are then calculated by the method of choice, and KDAF,RANDOM values are calculated for base shear and overturning moment. These DAFs are well defined, but it is not necessarily known of what components they are comprised. The intent of Formulae (A.10.5-4) to (A.10.5-6) is to present three different sets of actions that can result in the different maxima base shear and overturning moments. Large correcting moments are likely to be necessary in Formula (A.10.5-5), the inertia-only load case. In Formula (A.10.5-5), the point of application of the actions has effectively moved from being predominantly close to the waterline (due to wave/current) with a relatively small inertial component at the hull centre of gravity to having the predominant action applied at the hull centre of gravity. Given that the hull centre of gravity is significantly higher than the point of application of the wave/current action and the requirement to have a consistent base shear and overturning moment, the introduction of large correcting couples at the hull is likely to be necessary. NOTE 6 The base shear and overturning moments are the same in Formula (A.10.5-4) to (A.10.5-6), so there are unlikely to be significant differences in global jack-up response. The importance of the different load cases is the location of the actions and the components that comprise them. This can result in different member loads and stresses. NOTE 7 Formula (A.10.5-7) can have a different combined base shear and overturning moment than Formulae (A.10.5-4) to (A.10.5-6). In Formula (A.10.5-7), the magnitude of γf,D Fin,PHASE(−180) is identical, for both base shear and overturning moment, to the value of γf,D Fin,PHASE(180) in Formula (A.10.5-6), but it is applied in the opposite direction. This case represents the wave/current actions in the down-wind direction and the inertial actions in the up-wind direction. In most cases, the magnitude of the vector (Ee + γf,D De)(−180) is smaller than the magnitude of the equivalent vector in Formulae (A.10.5-4) to (A.10.5-6). It is, however, possible that the internal leg stresses can be higher due to changes in internal leg shear and bending moments. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 222 © ISO 2023 – All right reserved a) Representation of Formula (A.10.5-4) b) Representation of Formula (A.10.5-5) c) Representation of Formula (A.10.5-6) d) Representation of Formula (A.10.5-7) Key 1 direction of storm 2 wind action FWIND 3 wave action FSTATIC 4 up-wind wave action at wave trough FSTATIC.UP 5 inertial loadset Fin,PHASE(0) 6 inertial loadset Fin,PHASE(90) 7 inertial loadset Fin,PHASE(180) 8 inertial loadset Fin,PHASE(−180) with magnitude of base shear and overturning moment equal to Fin,PHASE(180) but applied in the opposite direction 9 simplified representation of wave/current action on jack-up 10 simplified representation of inertial action on jack-up 11 line indicating relative phase of wave/current action and inertial action for (a) = (0) 12 line indicating relative phase of wave/current action and inertial action for (a) = (90) 13 line indicating relative phase of wave/current action and inertial action for (a) = (180) 14 line indicating relative phase of wave/current action and inertial action for (a) = (−180) Figure A.10.5-2 — Diagrammatic representation of the load cases given in Formulae (A.10.5-4) to (A.10.5-7) with the jack-up schematics showing the actions and the lower curves showing the phase between wave/current action and inertial action Key ω ratio of the natural period, Tn, to the period of the forcing action, Tf θ phase angle in degrees between the forcing action and the inertial action Figure A.10.5-3 — Phase between the forcing action and the inertial action for an SDOF system for varying ratios of natural period to forcing period (Tn/Tf) and damping of 7 % of critical . No further reproduction or distribution permitted. Printed / viewed by: 223 A.10.5.3 Stochastic storm analysis A.10.5.3.1 General In a stochastic storm analysis the extreme response can be predicted by stochastic methods where the intent is to determine the MPME of the responses of interest using statistical methods (see A.10.5.3.4). In the two-stage deterministic storm analysis, the MPMEs of the base shear and overturning moment are used to develop DAFs. For a one-stage stochastic storm analysis, the intent is to determine time histories of the utilizations from which the MPME utilizations can be calculated; see Figure 10.5-4. In all stochastic analyses all action factors are set to 1,0 (see 8.8.1.3). When the stochastic storm analysis is used to determine a DAF (the first stage of a two-stage analysis), the metocean actions are unfactored in both the dynamic and the quasi-static analyses; the appropriate metocean action factor, γf,E, is applied in the second stage. However, when undertaking a fully integrated one-stage dynamic stochastic storm analysis that directly results in a time history of structural and foundation utilizations, the metocean parameters (i.e. wind velocity, wave height and current velocity) are factored; see A.10.5.3.2. The waves can be modelled using a random superposition model, which is fully described in A.7.3.3.3.2, that identifies important constraints associated with this method of random wave dynamic analysis. Figure A.10.5-4 — Analysis procedure for one-stage assessment with foundation fixity — Option 2 A.10.5.3.2 Application of partial factors to metocean parameters When undertaking a one-stage fully integrated dynamic stochastic storm analysis, partial factors are applied to the metocean parameters. To ensure consistency between the one-stage stochastic and the two-stage deterministic approaches, the partial factors on metocean parameters should produce metocean action levels comparable to the factored quasi-static metocean actions used in the deterministic method. When using dynamic stochastic storm analyses to determine a DAF for application in a two-stage deterministic analysis, the partial factors should be set to unity. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 224 © ISO 2023 – All right reserved The partial factors on metocean parameters for fully integrated one-stage dynamic stochastic storm analyses can be determined as follows.  Partial factor on wind velocity: The wind velocity used when generating the applied actions in accordance with A.7.3.4.1 should be factored by  √1,15 if 50 year return period independent metocean extreme storm actions are used, or  √1,25 if 100 year return period joint probability metocean data are used.  Partial factors on wave height and current velocity: The partial factors for wave height and current velocity for use in the stochastic analysis are determined through an iterative process. The process involves factoring the wave height and current velocity until the metocean parameter-factored quasi-static stochastic wave/current action matches the action-factored quasi-static deterministic wave/current action computed using higher-order wave theory (see NOTE below). The effects of wave spreading (see A.6.4.2.8) should be consistently included or consistently excluded in the stochastic and deterministic calculations used in the calibration. As a first approximation, the same partial factors can be used as given above for wind velocity. Some adjustment can be necessary to achieve a good or conservative match between the following two pairs of action values:  the stochastic MPME and the deterministic maximum;  the stochastic mean and deterministic mean, the latter determined from integration over a full wave cycle (i.e. not from the average of the maximum and minimum values). The match of MPME/maximum and mean actions is necessary to capture the cyclic behaviour. The adjustment generally results in different partial factors for the wave height and current velocity. The wave period used in the stochastic analysis should be modified to maintain the same wave steepness as that of the unfactored sea state. For the two-stage approach, the reference level for the wave and current actions is the quasi-static deterministic action. This reference level action is then modified through a DAF and the action factor to arrive at the final factored action. The important point is that the final action is founded on the quasi-static wave/current deterministic action. Conversely, in a fully integrated single stage analysis, there is no simple equivalent reference. It is, therefore, necessary to determine a stochastic equivalent to the factored deterministic quasi-static wave-current action. This is achieved by calculating the stochastic actions over three hours until partial metocean factors are found that match the MPME and mean actions with those from the action-factored quasi-static deterministic analysis. These partial metocean factors can, then, be used in the fully integrated stochastic dynamic analysis. A.10.5.3.3 Random wave dynamic analysis method Time domain simulations require that a suitable random sea state is generated, that the validity of the generated sea state is checked, and that the time step for the solution of the formulae of motion is sufficiently small. It is also necessary to ensure that the duration of the simulation(s) is sufficient for the method being used to determine the MPME. Specific recommendations are given in Tables A.7.3-3 and A.10.5-1. Wave spreading may be taken into account, either by using a three-dimensional analysis method or by using the kinematics reduction factor in a two-dimensional analysis (see A.6.4.2.3). Accounting for wave spreading generally results in a smaller DAF. . No further reproduction or distribution permitted. Printed / viewed by: 225 A.10.5.3.4 Methods for determining the MPME The extreme response that should be checked in the assessment is the MPME response which has a 63 % chance of exceedance in a three-hour storm. This MPME response is defined in Table A.10.5-1 as the mode value or highest point on the PDF. The stochastic waves modelled using a random superposition model result in non-Gaussian responses. Four methods for obtaining the MPME of the response are included in Table A.10.5-1. Considerable care should be taken when Tn/Tp is greater than 0,8 and the use of any method to determine the MPME response should be critically assessed. When Tn/Tp > 0,8 other Tn/Tp ratios should be considered. The intent is to maximize the relevant responses (see A.10.4.2), but while not being unnecessarily conservative. This can be done by  assessment of other wave height and period combinations (see A.6.4.2.9), or  including or changing the level of spudcan fixity. For the two-stage random dynamic analysis procedure the ratio of MPMEs of the dynamic to the quasi-static BS and OTM are used to determine the DAFs that are used to calculate the inertial loadset (see A.10.5.2.2.3). Table A.10.5-1 — Recommendations for determining MPME Method Recommendations General The MPME is defined as the extreme with a 63 % chance of exceedance (typically this is the mode or highest point on the PDF). This is approximately equivalent to the 1/1000 highest peak level in a three-hour storm and the extreme with approximately a 63 % chance of exceedance. Determination of the MPME from time domain simulations Fit a Weibull distribution to the distribution of response maxima and determine the maximum value for the probability level of one exceedance in 3 hours. Take results as the average of MPMEs from at least 5 simulations. Each input wave simulation should be of sufficient length (usually more than 60 min, see Table A.7.3-3). See C.2.1. or Use multiple three-hour simulations and fit a Gumbel distribution to the absolute maximum from each simulation. Sufficient simulations (usually 10 or more) should be used to obtain stable MPME response values. See C.2.2. or Use Winterstein's Hermite polynomial model; when the kurtosis is > 5 use the improvements proposed by Jensen. Simulations of sufficient duration to provide stable skewness and kurtosis of responses (normally in excess of several hours). See C.2.3. or Use the drag-inertia method with appropriate scaling based on period ratio, to determine the DAFs for use in a two-stage deterministic storm analysis. Simulations of sufficient duration to obtain stable standard deviation of responses are required (usually more than 60 min). See C.2.4. A.10.5.4 Initial leg Inclination The effects of initial leg inclination should be considered. Leg inclination can occur due to leg-to-hull clearances and hull inclination. Generally, hull inclination limits are set in the operations manual. The total horizontal offset due to leg inclination, OT, can be estimated as given in Formula (A.10.5-8): OT = O1 + O2 (A.10.5-8) where OT is the total horizontal offset of the leg base with respect to the hull; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 226 © ISO 2023 – All right reserved O1 is the offset due to leg-to-hull clearances; O2 is the offset due to maximum hull inclination permitted by the operating manual. If detailed information is not available, OT should be taken as 0,5 % of the leg length below the lower guide. It is necessary to account for the effects of leg inclination only in structural strength checks. This can be accomplished by increasing the effective moment in the leg at the lower guide by an amount equal to the offset OT times the factored vertical reaction at the leg base due to fixed, variable, environmental, inertial and P-Δ actions. A.10.5.5 Limit state checks The ULS responses for assessment should be determined using appropriate combinations of actions due to fixed and variable load, wave/current actions and wind actions as required by the acceptance criteria in Clause 13. The application of actions is described in 8.8; 5.4.3 requires that the analysis be carried out for a range of headings with respect to the jack-up such that the most onerous force(s) for each item listed in Table A.10.5-2 is(are) determined. The relevant ULS response parameters (action effects) are indicated in Table A.10.5-2. . No further reproduction or distribution permitted. Printed / viewed by: 227 Table A.10.5-2 — Action effects for limit state checks Limit state check Clause/Subclause Response parameters(s)a Action effect GF GVb Ee De min max Strength of members 12, 13.3 Member force vectorsc Y Yd Y Y Y Spudcan strength 13.4 Forces on the spudcan Y Y Y Y Holding system 13.5 Holding system force vectors Y Yd Y Y Y Overturning stability 13.8 Overturning moment Y Y Stabilizing moment Ye Yd,e Foundation capacity: 13.9, 9.3.6  preload A.9.3.6.2 Vertical leg reaction Y Y Y Y  sliding  pinned A.9.3.6.3 or A.9.3.6.4.2 Vertical and horizontal leg reactions Y Y Y Y  with moment fixity A.9.3.6.5 (A.9.6.3.4.2) Vertical, horizontal (and moment) leg reactions Y Y Y Y  bearing  pinned A.9.3.6.4.1 Vertical and horizontal leg reactions Y Y Y Y  with moment fixity A.9.3.6.5 Vertical, horizontal (and moment) leg reactions Y Y Y Y  displacement A.9.3.6.6 Spudcan displacements and reactions Y Yf Yf Y Y Key Y = yes GF = actions due to the fixed load positioned such as to adequately represent the vertical and horizontal distribution Gv = actions due to maximum or minimum variable load, as appropriate, positioned at the most onerous centre of gravity location applicable to the configurations under consideration Ee = metocean action due to the extreme storm event De = equivalent set of inertial actions representing dynamic extreme storm effects a In all instances the responses are assessed including the effects of deformation under functional actions (hull sag) and large displacement (P-Δ) effects. b Placed at most onerous centre of gravity position. c The effects of leg inclination to be included, which may be added after global response analysis (see A.10.5.4). d Consider minimum variable load if this is more onerous. e Fixed and variable load are included in response calculation so that P-Δ effects are captured. f As appropriate for the case under consideration: maximum for bearing and minimum for sliding. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 228 © ISO 2023 – All right reserved A.10.6 Fatigue analysis For jack-up operations of relatively long duration, see Clause 11. A.10.7 Earthquake analysis A.10.7.1 General The provisions in A.10.7 complement ISO 19901-2 by presenting special aspects of an earthquake assessment procedure for jack-ups. The general procedures in Clauses 6 to 10 with the associated guidance in Annex A remain valid where appropriate; more specific reference to earthquake situations is provided in 6.6, 7.7, 8.6.3, 8.8, 9.4 and 10.3. The greatest structural threat to a jack-up subjected to an earthquake is likely to be associated with vertical excitations that result in uneven settlement of the spudcans, which can cause lateral instability of the jack-up. In situations where the jack-up is working over a platform, the relative motions between the platform and jack-up should be evaluated. The relative motions can affect the conductor and should be considered. A.10.7.2 Earthquake assessment procedure ISO 19901-2 gives alternative procedures for determining earthquake actions and alternative methods for the evaluation of earthquake activity. The selection of the procedure and the method of evaluation depend on the seismic risk category (SRC). The SRC depends on the exposure level and seismic zone in which the jack-up is to be located and is given in ISO 19901-2. The effects of near-source excitation should be considered (see A.10.7.5). The simplified ELE screening methodology is given below and steps a) and b) are summarized in Table A.10.7-1. a) Determine earthquake actions using either the simplified earthquake action procedure or the detailed earthquake action procedure specified in ISO 19901-2 to develop spectral response accelerations for a bedrock base. Use of the simplified procedure (maps) for the initial screening of jack-ups is encouraged. b) Evaluate earthquake activity and the associated response acceleration spectra for the assessment of a jack-up against excitation of its base by ground motions using either ISO maps, regional maps or a site-specific earthquake hazard analysis, as specified in ISO 19901-2. Since ISO map accelerations are for a 1 000 year return period on rock, adjust the spectral shape for the 1 000 year event as described in ISO 19901-2 at the spudcan depth as a function of site soil characteristics. c) Perform response spectrum analysis in accordance with A.10.7.3. d) Evaluate the performance of the jack-up using the ULS assessment procedures provided in Clause 13. e) If the jack-up does not pass the simplified procedure, proceed to a more detailed assessment in accordance with A.10.7.4 using alternative analysis methods (see 10.9) and the ISO 19901-2 ALE procedures. . No further reproduction or distribution permitted. Printed / viewed by: 229 Table A.10.7-1 — Simplified procedure to develop 1 000 year ELE screening spectra using ISO 19901-2 Item Source in ISO 19901-2:2022 1 000 year accelerations – determine Sa,map Annex B or site-specific Determine the site seismic zone 6.4a Simplified seismic action procedure Clause 7 Determine soil site class 7.1a and Table 5 Spectral parameters Ca and Cv 7.1b and Tables 6 and 7 Develop horizontal spectrum 7.1c and Figure 2 Develop vertical spectrum 7.1d and Figure 3 Select damping 7.1e – use 5 % unless an alternate value justified Seismic action procedure 7.2, NALE = 1 and Cr = 1 A.10.7.3 ELE assessment A.10.7.3.1 Partial action factors The foundation, leg members and leg-to-hull connection should be assessed for the factored assessment actions defined in 8.8.1 for earthquake situations. The inertial action induced by the ELE ground motions should be determined using dynamic analysis procedures such as response spectrum analysis or time history analysis. NOTE Reference can be made to Annex B, which contains all of the applicable partial action and resistance factors for a site-specific analysis. Spudcan sliding should be considered for the minimum vertical reaction (uplift case) when the earthquake actions oppose the weight. A.10.7.3.2 Structural and foundation modelling The mass used in the dynamic analysis should consist of the mass of the structure associated with  the fixed load GF,  the best estimate of the variable actions; in lieu of specific data, 75 % of the maximum variable load Gv can be used,  the mass of entrapped water in the leg components and spudcans, and  the added mass. The added mass can be estimated as the mass of the displaced water for motion transverse to the longitudinal axis of individual structural members and appurtenances (see A.7.3.2). Table A.7.3-2 gives the hydrodynamic inertia coefficients that should be used in an earthquake assessment. For motions along the longitudinal axis of the structural members and appurtenances, the added mass may be neglected (except for spudcans). The spudcan internal entrapped mass should be included in the mass model and the spudcan added mass (surrounding water and/or soil) should be included where significant. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 230 © ISO 2023 – All right reserved The structural model should include the three-dimensional distribution of the stiffness and mass of the structure and account for large-displacement effects. The vertical distribution of mass is important for earthquake analyses as it affects the lateral inertial actions. Care should be taken when modelling the hull mass to ensure that the horizontal distribution of mass is correct as it affects the yaw response. The cantilever position should be considered when distributing the mass. Asymmetry in the distribution of the stiffness and mass of the jack-up can lead to significant torsion and should be considered in the assessment. The jack-up model should represent the operational configuration but the effects of the drill string can be ignored. Where the jack-up is supporting more than one conductor, their mass, added mass and stiffness should be considered in the model. For earthquake assessments, the hull sag moment should be based on the operating condition (see A.8.8.3). In computing the dynamic characteristics of the jack-up, a modal damping ratio of up to 5 % of critical may be used in constructing spectra for the ELE event. In addition, for the primary vertical mode, radiation damping in accordance with A.10.4.3.4 can be included in the vertical response spectra definition. Additional damping, including hydrodynamic or soil induced damping (hysteretic and radiation), should be substantiated by special studies. Guidance on structural damping, hydrodynamic damping, foundation damping and vertical radiation damping are given in A.10.4.3. Soil springs derived from small strain initial stiffnesses should be used to determine the natural periods. For earthquake screening analyses, the simplest adequate spudcan-soil models should normally be used. These models should incorporate the maximum interpreted small strain stiffnesses and maximum capacities (see Clause 9 and A.10.4.4.2). Soil stiffness degradation should not normally be included in an earthquake screening analysis. More detailed spudcan-soil interaction representations may be used. The minimum soils information should be obtained in accordance with A.6.5, but to a depth of 2 diameters below the deepest spudcan penetration. Depth to bedrock or a competent soil layer is required and can be estimated from geophysical investigation data or regional considerations. Foundation performance should be determined on the basis of studies that consider the assessment actions. Except for the simplified screening analysis, the non-linear stiffness and capacity of the foundation should be addressed in a manner compatible with Clause 9. If uplift or sliding is indicated from the screening analysis, non-linear dynamic time history or pushover analyses can be used to evaluate cumulative displacements and the resulting structural condition. Vertical actions on the foundations should not normally exceed the preload. If the vertical actions on the foundations exceed the preload and the ULS Step 3 displacement check (see A.9.3.6.6) reveals the potential for excessive additional penetration, non-linear dynamic time history analyses with cyclic degradation can be used to evaluate cumulative displacements and the resulting structural condition, e.g. encroachment on an adjacent fixed platform. A.10.7.4 ALE assessment For jack-ups that do not satisfy the ULS criteria for the ELE screening assessment, a site-specific non-linear ALE assessment can be used to try and demonstrate acceptability. This can be satisfied by a pushover analysis or by time history analyses using ALE excitation. Where substantial spudcan settlement or liquefaction is a possibility, a fully non-linear cyclic degrading analysis using best available soils modelling technology is recommended. . No further reproduction or distribution permitted. Printed / viewed by: 231 A.10.7.5 Near-source excitation If operating close to an active fault (typically within about 15 km), it can be necessary to consider near-source ground motions. At these near-source distances, the ground motions can exhibit substantial rupture directivity effects and directionality, with motion characteristics often considerably in excess of normal design values, including permanent offsets, larger amplitude ground motions at relatively longer periods (e.g. T ≥ 1 s), and vertical motions equal to or greater than horizontal motions at shorter periods (e.g. T ≤ 0,3 s). A.10.8 Ice A.10.8.1 General A.10.8.1.1 Operating area types For the purposes of this document, arctic and cold regions can be split into three types of area. These area types are not absolutely distinct, but have been delineated to give guidance on how the site-specific assessment should be undertaken. The three area types are: Area type 1 Areas that have a well-defined ice-free season during which ice development is extremely low probability, and there is no possibility of large scale ice features. An example of Area type 1 is upper Cook Inlet after all the ice has melted in the Inlet, and the intrusion of ice from Gulf of Alaska is not possible. Area type 2 Areas that have a well-defined season during which the area is free of sea ice, but can be affected by large scale ice features such as icebergs. An example of Area type 2 is the East Coast of Canada during the summer months. Area type 3 Areas that can have ice free periods, but can be subject to ice, in certain years, at any time of the year (e.g. parts of the Chukchi Sea) and areas that are not normally free from ice for any extended period at any time of the year. When deciding the classification of the proposed area of operations guidance should be sought from the operator and the relevant coastal state. The unit should be operated in conformity with its Marine Operations Manual. A.10.8.2 ULS No guidance offered. A.10.8.3 ALS No guidance offered. A.10.8.4 Assessments in the area types A.10.8.4.1 Area type 1 Jack-ups operating in type 1 areas, during the ice free season should be assessed in accordance with this document. Studies should be undertaken to define when the ice free season starts and ends (see ISO 19906 and ISO 35106). Operations should not commence until the area has been confirmed to be ice free. Ice detection and threat assessment should follow the guidelines of ISO 35104. The jack-up should be moved to a safe location before the start of the next ice season, even if planned operations have not been completed (see A.10.8.7). Plans, including contingencies, should be developed using risk analysis. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 232 © ISO 2023 – All right reserved For an area type 1, the potential for ice encroachment from other areas (e.g. open ocean into a bay or inlet) should be assessed to have an annual probability of ice interaction less than 10-4. Given this low probability of ice interaction [below the abnormal-level ice event (ALIE) requirements of ISO 19906] there is no requirement for establishment of physical ice management procedures. Since operations occur only when the area is free of ice and ALIE criteria are met, there is no extreme level ice event (ELIE) to be considered. A.10.8.4.2 Area type 2 Jack-ups operating in type 2 areas should be assessed to this document, supplemented by an ice management system. The ice management system should be developed to ensure that the annual probability of interaction between ice and the jack-up is below the 10-4 (the ALIE annual probability given in ISO 19906:2019, 7.2.2.4). Studies should be carried out to demonstrate that the ice management system can reduce the probability of iceberg interaction to below 10-4. Iceberg detection procedures should be established to ensure there is sufficient time for iceberg management, see ISO 35104. It should be demonstrated that the probability of sea ice is below the ALIE without recourse to physical ice management. Ice management plans can include moving the jack-up off site. If moving the jack-up is part of the methodology for reducing the ALIE probability, then due account should be taken of potential delays (see A.10.8.6). A.10.8.4.3 Area type 3 Jack-ups operating in type 3 areas should be assessed using the provisions relating to ice and actions contained in ISO 19906, ice management in ISO 35104, and supplemented by this document. The applicable combinations of wind, wave, current and ice actions are set out in ISO 19906. The sources of the annual probabilities associated with the actions and action factors are given in 10.8.2 and 10.8.3. The resistance factors should be in conformity with this document. The type, dimensions and properties of the ice used for the ice actions should be in accordance with ISO 19906, accounting for the season of operation and ice management procedures per ISO 19906. A detailed risk assessment should be conducted to determine, document and mitigate the ice related risks to the safety of the unit and its operation. Factors to be considered in such a risk assessment include, but are not limited to:  the capability of the unit to locally and globally withstand the ice actions given in ISO 19906 (e.g. increased wave actions on braces with increased ice build-up and the effects of the accumulation of ice rubble within the leg);  the reliability and effectiveness of ice forecasting and ice monitoring services, see ISO 35104 and ISO 35106;  the reliability and effectiveness of ice management services, see ISO 35104;  the ability to remove the unit from approaching iceberg tracks in a timely manner;  the feasibility of transit to and from the area of operations within the allowable temperature and ice conditions limitations;  the effects of ice accretion on the elevated and floating stability of the unit, see ISO 19906 and ISO 35106; . No further reproduction or distribution permitted. Printed / viewed by: 233  reliability of emergency evacuation and rescue systems, see ISO 19906:2019, Clause 18 and ISO 35102. Iceberg and sea ice detection procedures should be established that will ensure ice is detected far enough in advance for ice management to be effective, see ISO 35104. Ice management plans can include the effects of moving the jack-up off site, but if moving the jack-up is part of the methodology for reducing the ALIE actions, then due account should be taken of potential delays (see A.10.8.5.5). A.10.8.5 Additional factors to be considered for arctic and cold regions A.10.8.5.1 General As specified in A.10.8.1, jack-ups operating in arctic and cold regions should be assessed to this document and ISO 19906, as appropriate. Notwithstanding the general requirement for conformity with relevant clauses in these documents, some areas of specific consideration are discussed in A.10.8.5.2 to A.10.8.5.4. A.10.8.5.2 Geotechnical and geophysical considerations Geotechnical assessment should be carried out using information, penetrations, resistance factors, and additional penetration assessment calculated in accordance with Clause 9 of this document. However, due consideration should be given to arctic and cold region specific geophysical and geotechnical conditions with particular consideration given to the potential for permafrost at the site (see ISO 19906:2019, Clause 6; ISO 35106). The possible interaction between the spudcan and permafrost during and after preloading should be carefully considered taking full account of the potential for punch-through during preloading and sudden additional penetration during operations. The methodology for assessing permafrost given in ISO 19906 is not directly applicable to spudcan foundations, because they are small, but can be used to help establish a more spudcan-specific methodology. The potential for strudel scour near the mouth of a river should be assessed (see ISO 19906, ISO 35106). A.10.8.5.3 Dynamic ice actions Dynamic sea ice actions (see ISO 19906) can affect jack-ups. The magnitude of the effect is currently unknown for jack-ups specifically and should be investigated, since structures that have experienced ice-induced vibrations have had natural frequencies in excess of most jack-ups (0,4 to 10 Hz versus a likely jack-up frequency of 0,1 to 0,3 Hz). The same ice failure mechanisms are likely to apply to jack-ups as for jacket structures and other slender/flexible structures, see Yue and Bi (2000)[213], Blenkarn (1970)[25], Määttänen (1975)[131] and Johnston et al. (1999)[113]. Wave induced velocity of ice features (see ISO 19906, 8.3.2) can adversely affect the structure of a jack-up and should be assessed. A.10.8.5.4 Factors to consider for moving a jack-up off site in arctic and cold regions Normal field moves of jack-ups are not part of the scope of this document, but in arctic and cold regions, when moving a jack-up off site is part of the specified contingency plans for jack-up elevated operations, some special considerations should be taken. The limits on jacking the unit down and moving off site can be more restrictive than the elevated limits of the jack-up. Under these circumstances, plans should be established to move the jack-up based on the jacking and move limitations, not the elevated limits. Due consideration should be given to all the factors that could affect the ability of the jack-up to move off site. Some of the factors can include, but are not limited to: . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 234 © ISO 2023 – All right reserved  time to pull legs;  effect of permafrost on leg extraction (e.g. possible adhesion of the spudcan to permafrost);  potential for water freezing in the jetting lines, thereby making them ineffective;  consequences of jacking iced leg/chords/braces through the guides in event of leg icing;  potential for ice accumulation on top of the spudcan as leg is jacked up;  jack brakes freezing;  ability to skid the cantilever in;  jacking the hull down onto ice features;  ice actions on the hull while pulling legs;  effects of ice accretion on the floating stability of the unit;  towing speed when leaving site can be slower than in open water conditions;  reliability of the tugs and other necessary equipment in arctic and cold regions;  availability of a safe location to which to tow the jack-up. The above list is not intended to be complete. It is intended to give some guidance on factors that should be considered. A risk assessment of the operation of moving the jack-up off site should be carried out prior to commencing site-specific operations on the site. The risk analysis should consider all the factors that could adversely affect the ability and timing of a move. Any high risks identified during the risk assessment should be suitably mitigated. A.10.9 Accidental situations No guidance is offered. A.10.10 Alternative analysis methods A.10.10.1 Ultimate strength analysis No guidance is offered. A.10.10.2 Methodology When using the provisions of ISO 19902:2020, 7.11 (reserve strength), care should be taken in modelling non-linear behaviour of chords and holding system of a jack-up structure. A.11 Guidance on long-term applications A.11.1 Applicability No guidance is offered. . No further reproduction or distribution permitted. Printed / viewed by: 235 A.11.2 Assessment data A.11.2.1 Jack-up data A list of relevant modifications should be compiled including information about weights, wind areas and appurtenances added or removed that affect mass, applied actions and structural integrity. For a long-term application, such modifications can typically include:  increased weight and wind area from such items as production modules, risers, flare towers, accommodation blocks, and conductors;  increased wave and current actions due to risers, conductors or other structures exposed to waves. A.11.2.2 Metocean data The data required for a fatigue analysis should include long-term wave data in the form of a wave scatter diagram or a table of representative sea states, refer to A.6.4.2.10. Joint probability and/or directional metocean data can be used to optimize the ULS and FLS assessment for the long-term application. A.11.2.3 Geotechnical data Effects of seabed scour, differential settlement, consolidation settlement, expected reservoir subsidence, sand waves, etc. can be of greater significance for long-term applications. For this reason, the site-specific geotechnical data should include the information necessary to evaluate these phenomena. A.11.2.4 Other data Further data associated with the long-term application can be required. Examples include the possible effect on geotechnical properties due to top-hole construction activities, marine growth, effects from adjacent structures, etc. A.11.3 Special requirements A.11.3.1 Fatigue assessment A.11.3.1.1 Historical damage The assessment should take into account the fatigue history of critical details prior to installation on the planned site and focus on details of member connections that are essential to the overall structural integrity of the jack-up. In order to assess existing fatigue damage, specific information relevant to prior installations is required. The availability of the information depends on the information collected and retained by the jack-up owner over the life of the jack-up. The quality of the database affects the historical results. The historical data can have a large variability, requiring the assessor to make assumptions in the historical fatigue assessment. The assessment can include detailed fatigue analysis of the historical data and/or evaluation of inspection records. Parameters identified as important in addressing the historical aspects of jack-up fatigue are as follows:  geographic region (e.g. Gulf of Mexico, North Sea, Eastern Canada) and, where available, the co-ordinates of the previous sites so that metocean parameters can be developed for use in historical analysis;  hull elevation and orientation; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 236 © ISO 2023 – All right reserved  water depth;  penetration;  soil type and characteristics. A.11.3.1.2 Fatigue sensitive areas Areas that are susceptible to fatigue damage include  leg members and joints in the vicinity of the upper and lower guides for the operating leg/guide location,  leg-to-hull holding system,  leg members and joints adjacent to the waterline,  leg members and joints in the lower part of the leg near the spudcan, and  spudcan-to-leg connection. Normally, it is not necessary that the fatigue assessment include consideration of the hull structure since the long-term cyclic loading is similar to that experienced in multiple short-term operations. Generally the hull is not fatigue sensitive. A.11.3.1.3 Special considerations for fatigue assessment Special considerations in the fatigue assessment are listed below.  Inclusion of detailed models to arrive at local stress levels: Areas in the structure with high stress levels can be identified using models developed for global analysis and the stress ranges determined using appropriate stress concentration factors (SCFs) from literature. Alternatively, more detailed fine-mesh finite element models can be used to determine the hotspot stress ranges [suitable methodologies are given in DNV-OS-C104 (DNV 2022a)[63], DNV-RP-C203 (DNV 2021c)[59], ABS 115 (2003a)[11], ABS 115 (2003b)[12], API RP 2A-LRFD (1993)[14], HSE (2001)[91] and HSE (1999)[90]].  Effect of foundation stiffness (seabed fixity): The stiffnesses of the foundations are a function of the soil properties, the strain amplitudes and loading history (see A.9.3.4). As a consequence, the foundation modelling should consider upper and lower bound stiffnesses (see A.9.3.4.3 for clay and A.9.3.4.4 for sand). Typically, the fatigue assessment of the spudcan and lower part of the leg requires the use of upper bound stiffness, while the fatigue assessment for the upper leg and the leg-to-hull interface requires lower bound stiffness. Although the foundation stiffness varies as a function of the reactions beneath the spudcan, the variation is unlikely to be of significance except, possibly, for low-cycle fatigue.  Inclusion of non-linearities and dynamics: The structural response of a jack-up is such that pure linear techniques can be inadequate. Therefore, the analysis should include the non-linear effects of the structure. These can include  hydrodynamic actions,  large displacement effects (see 8.8.6), . No further reproduction or distribution permitted. Printed / viewed by: 237  dynamic amplification (see 10.5.2, 10.5.3), and  leg-to-hull interface, e.g. ensuring that those structures that transfer force in compression contact only are properly modelled. A.11.3.1.4 Fatigue analysis methodology A robust analysis method should be used to determine the fatigue damage. The method should determine the response of the jack-up structure to various sea states representing the operational environment. The jack-up should be considered in the operational configuration, which includes the levels of variable load, hull elevation and cantilever position. Wave spreading and directionality effects can be included. Foundation stiffnesses are generally assumed to be linear in smaller sea states. A check of non-linearity should be performed to validate this assumption for higher sea states. For guidance on suitable fatigue analysis methodology, S-N curves and SCFs the assessor is referred to one of the integral methods outlined in Table A.11.3-1. These should be used taking account of the specific structural characteristics of the jack-up as described above. For fatigue analysis the partial action factor should be reduced to unity when using S-N curves at the mean minus two standard deviations of log(N). Table A.11.3-1 — Sources of guidance on fatigue analysis methodology Organization Document Reference DNV Methods are given in DNV-OS-C104 Technical guidance on fatigue calculations, e.g. calculation methods, SN-curves, SCFs are given in DNV-RP-C203 Fatigue design of offshore steel structures DNV-OS-C104 (2022a)[63] DNV-RP-C203 (2021c)[59] ABS Methods are given in the Guide for the Fatigue Assessment of Offshore Structures (April 2003) Commentary on the Guide for the Fatigue Assessment of Offshore Structures (April 2003) ABS 115 (2003a)[11] ABS 115 (2003b)[12] API Methods are given in API RP2A-LRFD-2019 API RP 2A-LRFD (2019)[14] UK HSE Guidance is given in OTO 2001/015 and OTH92 390 HSE (2001)[91] HSE (1999)[90] ISO Methods are given in ISO 19902 — A.11.3.1.5 Fatigue acceptance criteria The fatigue analysis should determine the fatigue damage in the period before, as well as during the long-term application of the jack-up. The margin of safety of a structural detail depends on its accessibility for inspection and the availability of one or more alternative load paths (redundancy) after failure of the detail investigated. The acceptance criterion for fatigue strength is as given in Formula (A.11.3-1): fFD,eDc,e + fFD,sDc,s < 1,0 (A.11.3-1) where . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 238 © ISO 2023 – All right reserved Dc,e is the calculated existing fatigue damage prior to arriving at the site; Dc,s is the calculated fatigue damage during planned operations on site; fFD,e is the fatigue damage design factor applicable to Dc,e; generally, fFD,e = fFD,s, but fFD,e should not be taken larger than 2 if the detail has been inspected thoroughly before the long-term application; fFD,s is the fatigue damage design factor applicable to Dc,s; see Table A.11.3-2 or A.11.3-3. Table A.11.3-2 — Fatigue damage design factor fFD,s Fatigue damage design factor, fFD,s Full access for inspection and repair Access for inspection, no repair during operation No access for inspection, no repair during operation Full redundancy/minor consequence 2 3 5 No redundancy/major consequence 3 5 10 The values in Table A.11.3-3 give more detailed guidance for structures that are fully redundant, i.e. the structure does not have single members or member connections that, when damaged, can cause a failure with major consequence. This is typical of RCS approved jack-ups with braced legs. Table A.11.3-3 — Fatigue damage design factor fFD,s — Redundant structure Description (assumes there is structural redundancy for every member and member connection) Fatigue damage design factor, fFD,s Can inspect and repair Hull structure Primary hull structure 1 Leg-to-hull interface structure with access for inspection and repair 2 Leg structure in air Leg chords, brace to chord joints, brace joints 2 Can inspect but not repair Leg structure in splash zone Leg chords, brace to chord joints, brace joints 3 Leg structure under water Leg chords, brace to chord joints, brace joints, leg to spudcan connection 3 Spudcan Structure with access for inspection and repair 3 Cannot inspect or repair Hull structure Leg-to-hull interface structure without access for inspection and repair 5 Leg structure under sea floor Leg chords, brace to chord joints, brace joints, leg to spudcan connection 5 Spudcan Structure without access for inspection and repair 5 If necessary, fatigue life enhancement methods such as weld profiling, weld toe grinding and peening may be used, subject to RCS approval. Peening should only be used for improving fatigue lives after appropriate inspection. A.11.3.2 Weight control A weight control procedure should be prepared by the party responsible for operating and maintaining the jack-up during the long-term application. The procedure should be used to track the changes in weights and to ensure ongoing conformity with the assumptions used in the assessment. . No further reproduction or distribution permitted. Printed / viewed by: 239 The weight control procedure should be sufficient to satisfy the RCS requirements in lieu of the periodic dead weight survey. This should include wet weights where applicable. A.11.3.3 Corrosion protection No guidance is offered. A.11.3.4 Marine growth Marine growth should be taken into account in the site-specific assessment. The assessment can be for either the growth specified for the application period or for a pre-determined limit. In either case, the actual growth should be monitored and, when necessary, removed to ensure conformity with the assessment assumptions. A.11.3.5 Foundations Settlements can occur (see A.9.3.6.7, 11.3.5 and A.11.2.3), resulting in the loss of air gap or the hull being out-of-level. The consequences of resolving these should be considered in the assessment, e.g. the effect of guide position on the fatigue or strength analyses, changes in conductor support, etc. Consolidation of the soil through dissipation of pore pressures during the long-term operation can result in changes in foundation strength and stiffness. This affects the redistribution of leg moments and changes the dynamic response. The effects on fatigue life and strength should be considered, especially at the leg to spudcan connection. In conditions where scour can occur, scour protection can be required. A.11.4 Survey requirements A.11.4.1 Pre-deployment inspection plan The RCS special survey requirements prior to a long-term application can be more extensive than those of a typical special survey. Therefore, it is advisable to plan the surveys prior to mobilisation to a shipyard for modifications. The inspection plan should specify the locations and types of inspection, taking into account the areas that the assessor has identified as being critically stressed during the extreme storm or being fatigue sensitive during the long-term application. Areas that are not accessible, or are difficult to access for in-service inspection, should be subject to more detailed pre-deployment inspection and should be specially evaluated (see A.11.3.1). A.11.4.2 Project specific in-service inspection programme The project specific in-service inspection programme (PSIIP) should be developed by modifying and updating the existing in-service inspection programme normally required by the RCS. The PSIIP should reflect the requirements for the planned long-term application. NOTE The PSIIP is likely to be subject to direction and approval by the RCS. Areas that require special inspection procedures, such as underwater parts, should have documented inspection procedures, giving due consideration to the most suitable and practical methods. The results of the in-service inspections should be reviewed and, if appropriate, the PSIIP modified to reflect the results of this review. This information can be relevant to ensure the ongoing validity of the PSIIP and for extending the jack-up's time on site beyond that originally planned. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 240 © ISO 2023 – All right reserved A.11.4.3 Alternative project specific in-service inspection programme (PSIIP) An alternative can be derived using a probabilistic approach. The safety philosophy behind the alternative PSIIP should be in accordance with the RCS's safety philosophy and the structural reliability level inherent in the RCS rules should be maintained. The approach developed should be documented. When using a probabilistic approach, it should be recognized that uncertainties are associated with prediction of the fatigue performance and the inspection techniques applied. Key uncertainties should be accounted for in the probabilistic analysis. A.12 Guidance on structural strength A.12.1 Applicability A.12.1.1 General Clause A.12 applies to steel structures only. Where necessary, the formulae included in A.12 have been non-dimensionalized using Young's modulus, E, of 205 000 N/mm2 (or 29 700 ksi). For the purposes of strength assessment, it is necessary to consider the truss type leg structure as being comprised of structural members. Typically, each structural member can be represented by a single beam-column element in an appropriate analytical model of the structure. Examples of structural members are braces and chords in truss type legs and box or tubular legs, all of which form a part of the structure for which the properties can readily be calculated. The cross-section of a non-circular prismatic structural member is usually comprised of several structural components. Table A.12.2-1 shows classification limits for circular and non-circular prismatic members in typical jack-up chords comprising split-tubulars, rack plates, side plates and back plates (see Figure A.12.1-1). A component is by definition comprised of only one material. Therefore, where a plate component is reinforced by another piece of plating of a different yield strength (see Figure A.12.2-1) the reinforcing plate should be treated as a separate component. Non-circular prismatic members should be assessed using the provisions of A.12.6. . No further reproduction or distribution permitted. Printed / viewed by: 241 a) Opposed rack split tubular chord member section b) Triangular type chord member section Key 1 rack plate 2 split tubular 3 side plate 4 back plate 5 rack tooth Figure A.12.1-1 —Typical components of typical jack-up chord cross-sections Tubulars should be assessed as structural members using the provisions of A.12.5. In Clause 12, subscripts y and z are used to define the two axes of bending of tubular and prismatic members, however Fy is used to define the yield strength in stress units. NOTE The structural resistance factors for tubular members given in Clause 12 are based on an independent interpretation of the theoretical values derived from the data used in the calibration of API RP 2A LRFD, 1st edition, to API RP 2A, 15th edition, and the data used in the development of the ISO 19902 tubular members strength formulations. The values for non-tubular prismatic members were taken from AISC; see American Institute for Steel Construction (AISC) (2005)[13], which changed its equivalent resistance factor from 1,18 to 1,1 between the 1986 and 2005 editions because of a reassessment of the applicable data, which resulted in an effective reduction in the coefficient of variation. A.12.1.2 Truss type legs No guidance is offered. A.12.1.3 Other leg types No guidance is offered. A.12.1.4 Fixation system and/or elevating system No guidance is offered. A.12.1.5 Spudcan strength including connection to the leg No guidance is offered. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 242 © ISO 2023 – All right reserved A.12.1.6 Overview of the assessment procedure No guidance is offered. A.12.2 Classification of member cross-sections A.12.2.1 Member type No guidance is offered. A.12.2.2 Material yield strength The value of the yield strength taken from a tensile test should correspond to the 0,2 % offset value. Where this value is greater than 90 % of the ultimate tensile strength (UTS), the yield strength, Fy, used in A.12 should be taken as 90 % of UTS. The following variables are used in A.12: Fy is the yield strength in stress units (minimum of the yield strength and 90 % of the UTS); Fyi is the yield strength of the ith component of the cross-section of a prismatic member, in stress units (minimum of the yield strength and 90 % of the UTS of the ith component of the cross-section); Fymin is the minimum yield strength of the Fyi of all components in the cross-section of a prismatic member, in stress units; Fyeff is the effective yield strength of the cross-section of a prismatic member, in stress units, determined from the plastic tensile axial strength divided by the minimum cross-sectional area. A.12.2.3 Classification definitions A.12.2.3.1 Tubular member classification A cross-section of a tubular member is a class 1 section when Formula (A.12.2-1) applies: D/t ≤ 0,051 7 E/Fy (A.12.2-1) where D is the outside diameter; t is the wall thickness; Fy is the yield strength in stress units; E is Young's modulus of steel (E = 205 000 N/mm2). NOTE Conformity with class 1 classification is relevant only when undertaking earthquake, accidental or alternative strength analyses (see 10.7, 10.8 and 10.9). In all other cases, the distinction between class 1 (plastic) and class 2 (compact) is irrelevant to the assessment. A.12.2.3.2 Non-circular prismatic member classification Non-circular prismatic members that contain curved or tubular components should have the curved components classified based on the values given in Table A.12.2-1 and their flat components classified based on Tables A.12.2-2 to A.12.2-4. The limits given in Table A.12.2-1 tend to be conservative as, in most cases, there is additional support for the curved component by the flat components (e.g. the rack . No further reproduction or distribution permitted. Printed / viewed by: 243 in a split tube chord reinforces the split tube and helps to prevent local buckling). When the limits given in Table A.12.2-1 are considered to be too onerous, it can be possible to justify the use of alternative limits through rational analysis. NOTE The use of Tables A.12.2-3 and A.12.2-4 to classify cross-sections subject to axial compression and bending is complicated and requires knowledge of the cross-section stress distribution. It is always acceptable to conservatively base the cross-section classification on the relevant axial compressive case. Table A.12.2-1 — Classification limits for non-circular prismatic members containing curved components Class D/t limits Section in bending Section in compression 1 D/t ≤ 0,052 E/Fy D/t ≤ 0,052 E/Fy 2 D/t ≤ 0,103 E/Fy D/t ≤ 0,077 E/Fy 3 D/t ≤ 0,220 E/Fy D/t ≤ 0,102 E/Fy 4 D/t > 0,220 E/Fy D/t > 0,102 E/Fy When classifying non-circular prismatic components in accordance with Table A.12.2-2 to A.12.2-4, a distinction is made between internal components and outstand components as follows: a) internal components are components that are supported by other components along both longitudinal edges, i.e. the edges parallel to the direction of compression stress, and include  flange internal components: internal components parallel to the axis of bending;  web internal components: internal components perpendicular to the axis of bending; b) outstand components are components that are supported by other components along one longitudinal edge and at both ends of the member under consideration, with the other longitudinal edge free. When a cross-section is composed of components of different classes, it is classified according to the highest (least favourable) class of its compression components. Components within a cross-section can be ignored, provided that only the remaining cross-section is used for all aspects of the assessment. However, if a component that has been ignored is required to carry local loading, e.g. horizontal pinion thrust, the effects of the global actions should be considered when that component is assessed for the local loading. The effects of the global actions can normally be included by considering the global deformations of the member in addition to the local loading. In calculating the ratios given in Tables A.12.2-2 to A.12.2-4, the dimensions that should be used are those given in the relevant table. The components are generally of constant thickness; for components that taper in thickness, the average thickness over the width of the component should be adopted. Members that do not satisfy the applicable simplified lateral torsional buckling (LTB) criteria should be assessed further to determine a reduced representative member bending moment strength, Mb, using the guidance in A.12.6.2.6. The LTB criterion for singly symmetric open sections is taken from F2-5 of AISC (2005)[13], as given in Formula (A.12.2-2): . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 244 © ISO 2023 – All right reserved bltby,ltb176,LErF≤ (A.12.2-2) The LTB criterion for any closed section is derived from BS 5400-3, as given in Formula (A.12.2-3): 𝐿𝐿𝑏𝑏𝑟𝑟ltb≤0,36𝐼 1𝐸𝐸𝑍𝑍𝑝𝑝𝐹𝐹ymin􀶧𝐴𝐴g𝐽𝐽(𝐼 1−𝐼 2)(𝐼 1−𝐽𝐽/2,6) (A.12.2-3) where I1 is the major axis second moment of area of the gross cross-section; I2 is the minor axis second moment of area of the gross cross-section; Lb is the effective length of a beam-column between supports, i.e. the length between points that are either braced against lateral displacement of the compression flange, or braced against twist of the cross-section, in addition to lateral support; Ag is the gross cross-sectional area; J is the torsion constant, ()2ow4/AJbt=Σ where Ao is the area enclosed by the median line of the perimeter material of the section, bw is the width of each component (wall of the section) forming the closed perimeter, t is the thickness of each component (wall of the section) forming the closed perimeter; rltb is the radius of gyration about the minor axis as defined in Formula (A.12.3-6); Fy,ltb is the yield strength, Fy of the material that first yields when bending about the minor axis. Conservatively, Fy in Formulae (A.12.2-2) and (A.12.2-3) may be taken as the maximum yield strength of all the components in a non-circular prismatic cross-section; E is Young's modulus of steel; Zp is the fully plastic effective section modulus about the major axis determined from Formula (A.12.3-2); Fymin is the minimum yield strength of the Fyi of all components in the cross-section of a non-circular prismatic member, in stress units, as defined in A.12.2.2. A.12.2.3.3 Reinforced components Reinforcement of member cross-sections is often of the form shown in Figure A.12.2-1. . No further reproduction or distribution permitted. Printed / viewed by: 245 Key 1 base plate 2 reinforcing plate b1 width of base plate b2 width of reinforcing plate t1 thickness of base plate t2 thickness of reinforcing plate Figure A.12.2-1 — Definitions for reinforced plate To be considered a reinforcing plate, the plate should nominally be in contact with the base plate across its full width and continuously welded to the base plate on all edges with adequate welds. When a reinforcing component is used, there should be four independent checks of the cross-section classification in accordance with Tables A.12.2-2 to A.12.2-4: a) the reinforcing plate (using t2) over the width b2, using buckling coefficient increased by a factor of 1,573 (see below in A.12.2.3.3); b) the combined plate using tcheck over width b1; see Formula (A.12.2-4); c) the base plate (using t1) over the width b2 using buckling coefficient increased by a factor of 1,573 (see below in A.12.2.3.3); d) the base plate (using t1) over the dimension of the unreinforced widths (conservatively taken as b1 − b2). If any component in the cross-section is found to be slender (class 4), then the effective width of those components, used in determining the thickness of the effective combined plate, should be determined from Table A.12.3-1. If the combined plate is found to be slender (class 4), its effective width should be determined from Table A.12.3-1. Because the reinforcing plate is welded to the base plate around all edges, their ability to buckle independently over the width b2 is restricted. Therefore, the coefficients in Tables A.12.2-2, A.12.2-4, and A.12.3-1 may be increased by a factor of 1,573 for cases a) and c) to account for this limited buckling capability. NOTE As an example, the first limit in Table A.12.3-1, 0,72tf√(E/Fy), can be increased to 1,13 tf√(E/Fy) as derived from 1,13 = 0,72 × 1,573. The reinforcing plate should be classified as a compression flange internal component or web internal component in accordance with Tables A.12.2-2 and A.12.2-4 depending on the type of in-plane loading. The value of yield stress used is that of the reinforcing plate. The composite section should be classified as a compression flange internal component, a web internal component or a compression flange outstand component in accordance with Tables A.12.2-2 to A.12.2-4 depending on the type of in-plane loading and support conditions. The value of thickness tcheck for use . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 246 © ISO 2023 – All right reserved with width b1 in the formulae in Table A.12.2-2 and A.12.2-4 should be determined from Formula (A.12.2-4): tcheck = (t3eff t1)1/4 (A.12.2-4) where teff = (12 I/b1)1/3 (A.12.2-5) I = [b1(t1 + t2)3 − (b1 − b2)t23]/3 − Aeff(t1 + t2 − y1)2 (A.12.2-6) y1 = [b1t12 + b2t2(2t1 + t2)]/(2A) (A.12.2-7) Aeff = b1t1 + b2t2 (A.12.2-8) The value of yield stress for use in Tables A.12.2-2 to A.12.2-4 is the larger of the yield stress values for the reinforcing plate or the base plate. Table A.12.2-2 — Cross-section classification — Flange internal components Limiting width-to-thickness ratios for compressed internal components A-A is the axis of bending Class Type Section in bending Section in compression Plastic stress distribution in component and across section (compression positive) Plastic — Class 1 Rolled or welded b/tf ≤ 1,03√(E/Fy) b/tf ≤ 1,03√(E/Fy) Compact — Class 2 Rolled or welded b/tf ≤ 1,17√(E/Fy) b/tf ≤ 1,17√(E/Fy) Elastic stress distribution in component and across section (compression positive) Semi-Compact — Class 3 Rolled or welded b/tf ≤ 1,44√(E/Fy) b/tf ≤ 1,44√(E/Fy) Slender — Class 4 Rolled or welded b/tf > 1,44√(E/Fy) b/tf > 1,44√(E/Fy) . No further reproduction or distribution permitted. Printed / viewed by: 247 Table A.12.2-3 — Cross-section classification — Outstand components Limiting width-to-thickness ratios for outstand components A-A is the axis of bending Class Type Outstand subject to compression Outstand subject to compression and bending Tip in compression Tip in tension Plastic stress distribution in component (compression positive) Plastic — Class 1 Rolled Welded b/tf ≤ 0,33√(E/Fy) b/tf ≤ 0,30√(E/Fy) b/tf ≤ (0,33/α)√(E/Fy) b/tf ≤ (0,30/α)√(E/Fy) b/tf ≤ [0,33/(α√α)]√(E/Fy) b/tf ≤ [0,30/(α√α)]√(E/Fy) Compact — Class 2 Rolled Welded b/tf ≤ 0,37√(E/Fy) b/tf ≤ 0,33√(E/Fy) b/tf ≤ (0,37/α)√(E/Fy) b/tf ≤ (0,33/α)√(E/Fy) b/tf ≤ [0,37/(α√α)]√(E/Fy) b/tf ≤ [0,33/(α√α)]√(E/Fy) Elastic stress distribution in component (compression positive) Maximum compression at tip Maximum compression at connected edge Semi-Compact — Class 3 Rolled Welded b/tf ≤ 0,55√(E/Fy) b/tf ≤ 0,50√(E/Fy) b/tf ≤ 0,84√(kσE/Fy) b/tf ≤ 0,76√(kσE/Fy) ψ = σ2/σ1 kσ = 0,57 − 0,21ψ + 0,07ψ2 for 1 ≥ ψ ≥ −1 b/tf ≤ 0,84√(kσE/Fy) b/tf ≤ 0,76√(kσE/Fy) ψ = σ2/σ1 kσ = 0,578/(ψ + 0,34 for 1 ≥ ψ ≥ 0 kσ = 1,7 − 5ψ + 17,1ψ2 for 0 > ψ ≥ −1 Slender — Class 4 Rolled or Welded b/tf > than for Class 3 b/tf > than for Class 3 b/tf > than for Class 3 In the figures relating to stress distributions, the dimension, b, is illustrated only in the case of rolled sections. For welded sections, b should be assigned as shown in the diagrams at the top of the table. When determining α for Class 1 and 2 members, the loads should be scaled to give a fully plastic stress distribution. For all classes, it is conservative to use the relevant compression case. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 248 © ISO 2023 – All right reserved Table A.12.2-4 — Cross-section classification — Web internal components Limiting width-to-thickness ratios for web internal components A-A is the axis of bending Class Web subject to bending Web subject to compression Web subject to bending and compression Plastic stress distribution in component (compression positive) Plastic — Class 1 α = 0,5 d/tw ≤ 2,56√(E/Fy) α = 1,0 d/tw ≤ 1,03√(E/Fy) when α > 0,5 yw51860431,(/)/(,)EFdtα≤− when α ≤ 0,5 d/tw ≤ 1,28√(E/Fy)/α Compact — Class 2 d/tw ≤ 3,09√(E/Fy) d/tw ≤ 1,17√(E/Fy) when α > 0,5 yw4825121,(/)/(,)EFdtα≤− when α ≤ 0,5 yw155,(/)/EFdtα≤ Elastic stress distribution in component (compression positive) Semi-Compact — Class 3 d/tw ≤ 4,14√(E/Fy) d/tw ≤ 1,44√(E/Fy) when ψ > −1,0 yw14466740327,(/)/(,,)EFdtψ≤+ when ψ ≤ −1,0 d/tw ≤ 2,07(1 − ψ)√(−ψ)√(E/Fy) Slender — Class 4 d/tw > than for Class 3 d/tw > than for Class 3 d/tw > than for Class 3 When determining α for Class 1 and 2 members, the loads should be scaled to give a fully plastic stress distribution. For all classes it is conservative to use the relevant compression case. . No further reproduction or distribution permitted. Printed / viewed by: 249 A.12.3 Section properties of non-circular prismatic members A.12.3.1 General Cross-sectional properties appropriate for the strength assessment of non-circular prismatic members of all classes should be determined as described in A.12.3.2 to A.12.3.4; the nomenclature and definition of variables is summarized in A.12.3.5. The properties appropriate for the stiffness assessment of prismatic members should be based on elastic considerations. Where elastic section properties are determined for class 1 and class 2 sections in place of plastic section properties (e.g. for Euler amplification calculations or structural analysis input of stiffness parameters), these should be determined in accordance with A.12.3.3. Cross-sectional properties are normally required in respect of both major and minor axes of a non-circular prismatic member. Cross-sectional properties for tubular members are specified in A.12.5. The cross-sectional properties used in the stiffness model (e.g. when determining structural deflections and natural periods) can differ from those used when assessing member strengths. For example, leg chord properties may include 10 % of the maximum rack tooth area when determining the leg stiffness. This additional material should not be included when calculating the section properties for strength assessment, except it may be used when determining the column buckling strength (see A.12.6.2.4) and moment amplification (see A.12.4). A.12.3.2 Plastic and compact sections A.12.3.2.1 Axial properties — Class 1 and class 2 sections For class 1 plastic and class 2 compact sections, section properties should be determined assuming that fully plastic behaviour can occur. The properties required for a strength assessment should be determined taking into account the physical distribution of components comprising the cross-section and their yield strengths. For simplicity, the following approximations can be used to determine the relevant properties. For axial tension and compression, the fully plastic effective cross-sectional area for use in a strength assessment, Ap is as given in Formula (A.12.3-1): Ap = (ΣFyi Ai)/Fymin (A.12.3-1) where Fyi is the yield strength of the ith component of the cross-section of a prismatic member, as defined in A.12.2.2; Ai is the cross-sectional area of the ith component comprising the structural member; Fymin is the minimum yield strength of the Fyi of all components in the cross-section of a prismatic member, in stress units as defined in A.12.2.2. NOTE 1 The centroid of the plastic section (or squash centre) of a member comprising components of differing yield strength can be offset from the centroid of the elastic section. NOTE 2 Ap can be larger than the physical cross-section of the member. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 250 © ISO 2023 – All right reserved A.12.3.2.2 Flexural properties — Class 1 and class 2 sections The second moment of area, If, should be determined using the fully effective cross-section. The fully plastic effective section modulus Zp is as given in Formula (A.12.3-2): Zp = (Σ Fyidi Ai)/Fymin (A.12.3-2) where di is the distance between the centroid of the ith component and the plastic neutral axis. NOTE The plastic neutral axis does not necessarily coincide with the equal area axis for cross-sections composed of different yield strengths. When using this definition of Zp, the value of yield stress that should be used in the calculation of plastic moment strengths should be Fymin as defined in A.12.2.2. A.12.3.3 Semi-compact sections For class 3 semi-compact sections, the section properties should be based on elastic properties assuming that the full cross-section is effective. The relevant variables are the cross-sectional area, Af, as given in Formula (A.12.3-3), the second moment of area, If, and the elastic section modulus, Sf. Af = Σ Ai (A.12.3-3) The properties If and Sf should be determined assuming that the full cross-section is effective for bending about both major and minor axes. When considering a cross-section comprised of components having different yield strengths, the section moduli used in the calculations should encompass all critical points on the cross-section. NOTE Critical stress locations are typically those at the edges of components and are a function of the member forces, the yield strength of the component and its position within the cross-section of the member. A.12.3.4 Slender sections A.12.3.4.1 General Class 4 classification is determined from Tables A.12.2-1 to A.12.2-4. Cross-sectional properties for class 4 slender sections should be determined using elastic principles. In tension, fully effective sections should be assumed, i.e. Af and Sf. In compression, the sectional properties should be based on effective sections as described here. When analysing structures that contain class 4 sections, care should be taken when determining the force distributions. It is recommended that the structural analysis be performed using full elastic section properties and that the reduced section properties are used only for the member strength checks. Since this overestimates the forces in class 4 members, care should be taken when the use of the reduced sections causes a significantly different force distribution. In this case, an iterative analysis process can be required. Effective sections should be based on actual plating thicknesses combined with plating effective widths. The effective widths of compression flange internal or outstand components should be determined in accordance with the formulae presented in Table A.12.3-1 a) or b), respectively. The effective widths of web internal components subject to compression and/or bending should be determined as shown in Table A.12.3-1 c) for which the following definitions apply (compression is taken as positive and tension as negative): . No further reproduction or distribution permitted. Printed / viewed by: 251 ψ is the ratio of compressive stress to bending stress; σ1 is the compressive stress if σ2 is tensile or the larger compressive stress if σ2 is also compressive; σ2 is the tensile stress if σ2 is tensile or the smaller compressive stress if σ2 is compressive; k is the buckling coefficient (used in the assessment of the effective width of each components in a cross section); ρ is the reduction coefficient; λp is the plate slenderness parameter; λplim is the limiting plate slenderness ratio; λpo is the plate slenderness ratio coefficient. When determining effective widths for web internal components, the stress ratio, ψ, used in Table A.12.3-1 should be based on compression flange internal and outstand component effective widths, but the gross web section properties may be used. The area reduction of curved components should be determined through the use of A.12.5.2.4. The following steps should be followed. a) The representative local buckling strength should be determined for a tubular member with the wall thickness and diameter equivalent to the curved component in the non-circular prismatic member. b) The strength of a tubular, of the same diameter and wall thickness used in step a), should be determined based on its full cross section and material yield. c) The ratio of the strengths should be determined as in step a) strength divided by step b) strength. d) This ratio of strengths should then be used to determine an equivalent reduced area of the curved component in the non-circular prismatic member. The use of plating effective widths generally leads to a shift in the neutral axis compared with that found using gross sectional properties. This shift should be taken into account when determining effective widths. When the structural analysis is performed using gross section properties, the additional moment caused by the shift in the neutral axis should be found as the product of the axial force acting on the member and the shift in the neutral axis. This moment should be treated as additional to other moments acting on the effective section unless more onerous conditions arise if it is omitted. A.12.3.4.2 Effective areas for compressive loading The effective area Aeff,i of a compressed component i should be found as the product of its thickness and its effective width (which should never be taken as greater than the actual width). The effective area of a curved component subject to uniform compression should be determined from its actual area reduced by the ratio of its strength when treated as a class 3 or class 4 tubular [Formula (A.12.5-8), when 0,170 < AFy/Pxe] versus its strength when treated as class 1 or class 2 tubular [Formula (A.12.5-8), when AFy/Pxe ≤ 0,170], as set out in steps a) to d) in A.12.3.4.1. The total effective area, Aec, is the sum of the component effective areas, as given in Formula (A.12.3-4): . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 252 © ISO 2023 – All right reserved Aec = Σ Aeff,i (A.12.3-4) A.12.3.4.3 Effective moduli for flexural loading For web or flange internal components subject to combinations of flexural and compression loading, effective widths should be determined from Table A.12.3-1 c). For web or flange outstand components subject to combinations of flexural and compression loading, effective widths (which should never be taken as greater than the actual widths) should be determined from Table A.12.3-1 b). The effective area of a curved component subject to flexure should be determined from its actual area reduced by the ratio of its strength when treated as class 3 or class 4 tubular [Formula (A.12.5-13), for 0,103 4 < (Fy D)/(E t)] versus its strength when treated as class 1 tubular [Formula (A.12.5-13), for (Fy D)/(E t) ≤ 0,051 7], as set out in steps a) to d) in A.12.3.4.1. The effective second moment of area Ie should be found by calculating the properties of the section based on fully effective areas for components subject to tension, on effective areas as defined in A.12.3.4.2 for components subject to compression, and on effective areas as defined in the first paragraph for components subject to combinations of compression and flexure. Application of this procedure to determine effective second moments of area when applied to cross-sections with slender components, especially when the section is not symmetric with respect to a particular axis, leads to two values of Ie about such an axis, depending upon the sign of the bending moment. Conservatively, the smaller value of Ie can be used throughout the strength analysis. When considering a cross-section comprised of components having different yield strengths, the reduced elastic section modulus Se used in the calculations should encompass all critical points on the cross-section: Se = Ie/yi (A.12.3-5) where yi is the distance from the neutral axis associated with Ie to the critical point i. NOTE Critical stress locations are typically those at the edges of components and are a function of the member forces, the yield strength of the component and its position within the cross-section of the member. . No further reproduction or distribution permitted. Printed / viewed by: 253 Table A.12.3-1 — Section properties — Effective widths for components in slender sections a) Compression internal components b) Outstand components under compression and/or bending ψ = σ2/σ1 1 ≥ ψ ≥ 0 deff = ρ d de1 = 2deff/(5 − ψ) de2 = deff − de1 λp = 1,04(d/tw) √[Fy/(Ek)] ρ = 1 if λp ≤ 0,75 ρ = [λp − 0,047(3 + ψ)]/λp2 ≤ 1,0 if λ p > 0,75 and (3 + ψ) ≥ 0 k = 8,2/(1,05 + ψ) if 1 ≥ ψ > 0 k = 7,81 − 6,29 ψ + 9,78 ψ2 if 0 ≥ ψ > −1 k = 5,98 (1 − ψ)2 if −1 ≥ ψ > −3 ψ ≤ 0 deff = ρ dc = ρ d /(1 − ψ) de1 = 0,4 deff de2 = 0,6 deff c) Internal components under compression and/or bending Key A-A axis of bending ineffective area, which is ignored when calculating effective section properties NOTE 1 a) is a special case of c) with no bending and is included for clarity. NOTE 2 The formula for Kσ, used in b), is given in Table A.12.2-3 in the row for “Semi-compact – Class 3” members. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 254 © ISO 2023 – All right reserved A.12.3.5 Cross-sectional properties for the assessment A.12.3.5.1 Tension In tension, the cross-sectional area for use in the assessment should be At where At = Ap for class 1 plastic or class 2 compact sections, see Formula (A.12.3-1); = Af for class 3 semi-compact sections as defined in Formula (A.12.3-3); = Af as defined in Formula (A.12.3-3) for class 4 slender sections in tension across the whole of the cross-section (including bending); otherwise use Aec for class 4 sections as defined by Formula (A.12.3-4). Where the cross-section contains cut-outs, pin-holes, etc., At should be determined at the location of the minimum cross-section, unless the section is equipped with doubler plates surrounding the hole that at least replace all the lost area. A.12.3.5.2 Compression In compression, the cross-sectional area for use in the assessment should be Ac where Ac = Ap for class 1 plastic or class 2 compact sections, see Formula (A.12.3-1); = Af for class 3 semi-compact sections as defined in Formula (A.12.3-3); = Aec for class 4 slender sections as defined in Formula (A.12.3-4). A.12.3.5.3 Flexure In flexure, the second moment of area with respect to the y and z axes of bending that should be used in the assessment should be determined from the following: Iy, Iz = If for class 1 plastic and class 2 compact sections as defined in A.12.3.2.2; = If for class 3 semi-compact sections as defined in A.12.3.3; = Ie for class 4 slender sections as described in A.12.3.4.3 accounting for both the chosen axis and the direction of bending. The section moduli for the two bending axes should be determined from the following: Sy, Sz = Zp for class 1 plastic or class 2 compact sections, see Formula (A.12.3-2); = Sf for class 3 semi-compact sections as defined in A.12.3.3 for each critical stress location; = Se for class 4 slender sections as defined in A.12.3.4.3 for each critical stress location, accounting for both the chosen axis and the direction of bending. The radius of gyration about the minor axis that should be used for lateral-torsional buckling considerations, rltb, should be determined as given in Formula (A.12.3-6): rltb = (If /Ac)0,5 for sections in classes 1 to 3; (A.12.3-6) . No further reproduction or distribution permitted. Printed / viewed by: 255 = (Ie /Aec)0,5 for sections in class 4. A.12.4 Effects of axial force on bending moment A.12.4.1 General Euler moment amplification (p-δ) applies to all members in axial compression. For classes 1, 2, and 3 cross-sections, the eccentricity between the elastic and plastic centroids induces an additional moment. This affects members in both tension and compression. For class 4 members, in addition to the Euler moment amplification, there is an eccentricity between the full cross-section area normally used in the structural analysis and the effective neutral axis used in the member strength check. This can affect members in both tension and compression. A.12.4.2 Member moment correction due to eccentricity of axial force The plastic centroid or “centre of squash” is defined as the location at which the axial force produces no moment on the fully plastic section. For chords with material asymmetry (e.g. when the section includes components of differing yield strengths) the centre of squash can be offset from the elastic centroid. Before a section is checked, the moments should be corrected by the moment due to the axial force times the eccentricity between the elastic centroid (used in the structural analysis) and the “centre of squash” in accordance with Formula (A.12.4-1). There is no eccentricity for tubular members or for non-circular prismatic members with material symmetry. The corrected effective moment, Mue, should be calculated for each axis of bending, as given in Formula (A.12.4-1): Mue = Mu + ePu (A.12.4-1) where Mu is the moment in a member due to factored actions determined in an analysis that includes global P-Δ effects; Pu is the axial force in the member due to factored actions determined in an analysis that includes global P-Δ effects; e is the eccentricity between the axis used for structural analysis and that used for structural strength checks, taking due account of the sign in combination with the sign convention for Pu: e for class 1 and 2 members, is the distance between the elastic and plastic neutral axes orthogonal to the axis of bending under consideration. Annex F presents data including this offset distance (together with other geometric data) for many members of each chord family, e for class 3 members, is equal to ea as defined in A.12.6.2.3, e for class 4 members, is the distance between the neutral axes of the full and effective cross-sections, orthogonal to the axis of bending under consideration, e is equal to 0 if the structural model fully accounts for the offset between the neutral axes of the modelled member in the strength checks, e is equal to 0 for tubular members; for other cross-sections in classes 1, 2 and 3 with material symmetry and when an elastic strength check is used for the assessment of members in classes 1, 2 and 3. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 256 © ISO 2023 – All right reserved A.12.4.3 Member moment amplification and effective lengths The amplified moment, Mua, should be calculated for each axis of bending as given in Formula (A.12.4-2): Mua = Bmaf Mue (A.12.4-2) where Mue is as defined in A.12.4.2; Bmaf is the member moment amplification factor for the axis under consideration, equal to one of the following:  Bmaf = 1,0 for (i) members in tension, or (ii) members in compression where the individual member forces are determined from a second order analysis, i.e. the equilibrium conditions are formulated on the elastically deformed structure so that local p-δ effects are already included in Mu;  𝐵𝐵maf =𝐶𝐶𝐦𝐦𝐦𝐦(1−𝑃𝑃u/𝑃𝑃𝐸𝐸)for members in compression where the local member forces are determined from a first-order linear elastic analysis, i.e. the equilibrium conditions are formulated on the undeformed structure and therefore Mu does not include the local member p-δ effects: where PE = (π2 E I)/(K Lub)2, and should be calculated for the plane of bending; I is the second moment of area for the plane of bending as defined in A.12.3.5.3 (including percentage of rack teeth of chords, see A.12.3.1); K and Cmr are given in Table A.12.4-1; K is the effective length factor for the plane of flexural buckling; Lub is the unbraced length of member for the plane of flexural buckling normally taken as one of the following:  face to face length for braces;  braced point to braced point length for chords;  longer segment length of X-braces (one pair is in tension, if not braced out-of-plane). When the analysis of a jack-up with single-column tubular or box section legs has been undertaken accounting for the member moment amplification effects of global P-Δ/hull-sway, Bmaf may be taken as 1,0 as local p-δ and global P-Δ are the same. For these jack-ups, local strength due to guide reactions should be assessed in conjunction with the member forces. . No further reproduction or distribution permitted. Printed / viewed by: 257 Table A.12.4-1 — Effective length and moment reduction factors Structural member K Cmra Tubular or box complete legs 2,0b A Chords with lateral loading 1,0 C Chords without lateral loading 1,0 B Tubular braces Primary diagonals and horizontals 0,7 B or C K-bracesc 0,7 C X-bracec Longer segment length 0,8 C Full lengthd 0,7 C Secondary horizontals (e.g. span-breakers) 0,7 B or C a The value of Cmr can be determined from rational analysis. In lieu of such analysis, the following values may be used: A For members whose ends are restrained against sidesway Cmr = 0,85 For members whose ends are unrestrained against sidesway Cmr = 1,0 B For members with no significant transverse loading, ignoring self-weight; buoyancy; and direct wave/current and wind actions: Cmr = 0,6 − 0,4 M1/M2 ≤ 0,85 where M1/M2 is the ratio of the smaller to the larger non-amplified end moments of the segment of the member in the plane of bending under consideration. M1/M2 is positive for the segment subject to reverse curvature and negative when subject to single curvature. M1 = Mue at end 1; similarly for M2 C For members with significant transverse loading, other than distributed actions including self-weight; buoyancy; and direct wave/current and wind actions: Cmr = 1,0 − 0,2 Pu/PE ≤ 0,85 (AISC (2005)[13] Table C-C2.1, point actions) PE = PEy or PEz as appropriate for the axis of bending under consideration. b Alternatively use effective length alignment chart in Figure A.12.4-1. c For either in-plane or out-of-plane effective lengths, at least one pair of members framing into a K- or X-joint is in tension if the joint is not braced out-of-plane. d For X-braces, when all members are in compression and the joint is not braced out-of-plane. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 258 © ISO 2023 – All right reserved To estimate the effective length of an unbraced column, such as tubular or box complete legs, the use of the alignment chart in Figure A.12.4-1 provides a simplified method for determining adequate K values. The alignment chart can be modified to allow for conditions different from those assumed in developing the chart. The subscripts A and R refer to the joints at the two ends of the column section being considered. G is defined as 𝐺𝐺=Σ𝐼𝐼𝑐𝑐𝐿𝐿𝑐𝑐Σ𝐼𝐼0𝐿𝐿0 in which Σ indicates a summation of all members rigidly connected to that joint and lying in the plane in which buckling of the column is being considered. Ic is the moment of inertia and Lc the unsupported length of the column section, and I0 is the moment of inertia and L0 the unsupported length of a girder or other restraining member. Ic and I0 are taken about axes perpendicular to the plane of buckling being considered. For column ends supported by a pinned restraint, G is theoretically infinite but, unless truly friction free, can be taken as 10 for practical cases. If the column end is rigidly restrained, G may be taken as 1,0. Smaller values may be used if justified by analysis. NOTE Taken from ISO 19902:2020, Figure A.13.5-4. Figure A.12.4-1 — Alignment chart for determining the effective length of unbraced columns A.12.5 Strength of tubular members A.12.5.1 Applicability The strength of unstiffened tubular members that satisfy Formula (A.12.5-1) should be assessed in accordance with A.12.5. D/t ≤ 0,2 E/Fy (A.12.5-1) Tubulars that do not satisfy Formula (A.12.5-1) should be assessed using alternative methods that result in levels of reliability comparable to those implicit in this document, such as DNV-RP-202 (DNV 2021b)[58] and API Bulletin 2U (2004)[16]. The strength formulae in A.12.5.1 to A.12.5.3 for D/t ≤ 0,2 E/Fy are unconservative for tubulars with reductions in their cross-section. Where a tubular includes cross-sections with cut-outs, pin-holes, etc., it should be treated as for a non-circular prismatic member, unless it is adequately reinforced. Reinforcement can comprise either doubler plates that surround the hole or stiffeners that extend at least half the width of the hole above and below the hole. If the reinforcement replaces all the lost area of the tubular, the strength formulae in A.12.5 may be used. The strength formulae are considered applicable for steels with a yield strength up to 800 N/mm2. The yield strength used should be as specified in A.12.2.2. . No further reproduction or distribution permitted. Printed / viewed by: 259 NOTE The strength formulae for tubular members are based on ISO 19902:2020, Clause 13. However, for use in this document, the ISO 19902 formulations have been converted to a force base rather than a stress base. In addition, the combined axial, bending, beam shear and torsion checks have been simplified in A.12.5. The formulae ignore the effect of hydrostatic pressure. The condition under which hydrostatic pressure can be ignored for a specific member is as given in Formula (A.12.5-2): 𝑑𝑑w≤𝑑𝑑w,lim (A.12.5-2) where dw is the equivalent head of water in metres applicable to the tubular in question; it is the depth below the water surface (including penetration into the seabed where applicable) plus the additional soil pressure pγ′/(ρwg); dw,lim is the limiting head of water in metres applicable to the tubular in question, 𝑑𝑑w,lim=􁉀211(𝐷𝐷/𝑡𝑡)􁉁2,985; p is the depth below the sea floor in metres (zero if above sea floor); γ ′ is the submerged (effective) unit weight of the soil; ρw is the mass density of water; g is the acceleration due to gravity. For convenience, some typical maximum values of D/t, are given for a range of effective heads of water in Table A.12.5-1. Table A.12.5-1 — Maximum (D/t)m values for given equivalent head of water Equivalent head of water dw,lim m Maximum tubular (D/t) 43 60,0 50 56,9 75 49,7 100 45,1 125 41,9 150 39,4 200 35,8 If the member D/t exceeds the maximum value of (D/t), the assessor should refer to ISO 19902, which is based on stress rather than strength. A.12.5.2 Tension, compression and bending strength of tubular members A.12.5.2.1 Yield strength to be used in calculating capacities The presence of torsion can affect the axial, bending and shear capacities of tubular members. The flow of A.12.5 has been set up that all the basic member strength calculations include the effects of torsion, where appropriate. When the torsion is small, these effects reduce to zero impact. If there is a need to calculate simple axial and bending capacities without any torsional effects, then the actual yield . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 260 © ISO 2023 – All right reserved strength of the material may be used in these checks to give an indicated, informative value. However, all reported strengths should include the effects of torsion. The yield strength, Fy,T, which includes the effects of member torsion to be used in A.12.5 should be calculated using Formula (A.12.5-3): 𝐹𝐹y,T=𝐹𝐹y when 𝑇𝑇u≤0,2 𝑇𝑇v𝛾𝛾R,Tv 𝐹𝐹y,T=􁉀1−𝑇𝑇u(𝑇𝑇v 𝛾𝛾R,Tv⁄)􁉁𝐹𝐹y when 𝑇𝑇u>0,2 𝑇𝑇v𝛾𝛾R,Tv (A.12.5-3) where Fy is the yield strength in stress units as defined in A.12.2.2; Tu is the torsional moment due to factored actions; Tv is the representative torsional strength, calculated as given in Formula (A.12.5-4): Tv = 2IptFy /(D √3) (A.12.5-4) Ipt is the polar moment of inertia of a tube, calculated as given in Formula (A.12.5-5): Ipt = (π/32) [D4 − (D − 2t)4] (A.12.5-5) γR,Tv is the partial resistance factor for torsional and beam shear strengths, γR,Tv = 1,05. A.12.5.2.2 Axial tensile strength check Tubular members subjected to axial tensile forces, Put, due to factored actions should satisfy Formula (A.12.5-6): Put ≤ A Fy,T /γR,Tt (A.12.5-6) where A is the gross cross-sectional area; γR,Tt is the partial resistance factor for axial tensile strength, γR,Tt = 1,05. A.12.5.2.3 Axial compressive strength check Tubular members subjected to axial compressive forces, Puc, due to factored actions should satisfy Formula (A.12.5-7): Puc ≤ Pa /γR,Tc (A.12.5-7) where Pa is the representative axial compressive strength as determined in A.12.5.2.5; γR,Tc is the partial resistance factor for axial compressive strength, γR,Tc = 1,15. A.12.5.2.4 Local buckling strength The representative local buckling strength, Pyc, should be determined as given in Formula (A.12.5-8): . No further reproduction or distribution permitted. Printed / viewed by: 261 Pyc = A Fy,T (for A Fy,T/Pxe ≤ 0,170) Pyc = (1,047 − 0,274 A Fy,T/Pxe) A Fy,T (for 0,170 < A Fy,T/Pxe ≤ 0,333) (A.12.5-8) where, in addition to the variables in A.12.5.2.1, Pxe is the representative elastic local buckling strength, calculated as given in Formula (A.12.5-9): Pxe = 2 Cx E A (t/D) (A.12.5-9) where Cx is the critical elastic buckling coefficient. The theoretical value of Cx for an ideal tubular is 0,6. However, a reduced value of Cx = 0,3 is recommended for use in the determination of Pxe to account for the effect of initial geometric imperfections. A reduced value of Cx = 0,3 is also implicit in the limits for A Fy,T/Pxe given in Formula (A.12.5-8). A.12.5.2.5 Column buckling strength The representative axial compressive strength of tubular members, Pa, should be determined from Formulae (A.12.5-10) and (A.12.5-11): Pa = (1,0 − 0,278λ2)Pyc (for λ ≤ 1,34) Pa = 0,9 Pyc/λ2 (for λ > 1,34) (A.12.5-10) where λ = (Pyc/PE)0,5 (A.12.5-11) Pyc is the representative local buckling strength (see A.12.5.2.4); λ is the column slenderness parameter; PE is the smaller of the Euler buckling strengths about the y- or z-direction, PE = π2 E I/(KLub)2; E is Young's modulus as defined in A.12.1.1; K is the effective length factor in y- or z-direction; see A.12.4.3; Lub is the unbraced length in y- or z-direction; see A.12.4.3; I is the second moment of area of the tubular. A.12.5.2.6 Bending strength check Tubular members subjected to bending moments, Mu, should satisfy Formula (A.12.5-12): Mu ≤ Mb /γR,Tb (A.12.5-12) where . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 262 © ISO 2023 – All right reserved Mu is equal to 􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5; it is the resolved bending moment due to factored actions about member y- and z-axes, respectively, determined in an analysis that includes global P-Δ effects; Mb is the representative bending moment strength, determined as given in Formula (12.5-13): Mb = Mp for (Fy,T D)/(E t) ≤ 0,051 7 Mb = [1,13 − 2,58 (Fy,TD)/(E t)] Mp for 0,051 7 < (Fy,T D)/(E t) ≤ 0,103 4 (A.12.5-13) Mb = [0,94 − 0,76 (Fy,TD)/(E t)] Mp for 0,103 4 < (Fy,T D)/(E t) ≤ 0,2 Mp is the plastic moment strength as given in Formula (A.12.5-14): Mp = Fy,T [D3 − (D − 2t)3]/6 (A.12.5-14) γR,Tb is the partial resistance factor for bending strength, γR,Tb = 1,05. A.12.5.2.7 Torsional shear strength check Tubular members subjected to torsional shear forces due to factored actions should satisfy Formula (A.12.5-15): Tu ≤ Tv /γR,Tv (A.12.5-15) where Tu is the torsional moment due to factored actions; Tv is given in Formula (A.12.5-4). A.12.5.2.8 Beam shear strength check Tubular members subjected to beam shear forces due to factored actions should satisfy Formula (A.12.5-16): V ≤ Pv/γR,Tv (A.12.5-16) where V is the beam shear due to factored actions; Pv is the representative shear strength, as given in Formula (A.12.5-17): Pv = A Fy,T/(2√3) (A.12.5-17) NOTE Pv is calculated from Fy,T according to Formula (A.12.5-3) and therefore accounts for the effects of torsion. A is the gross cross-sectional area; γR,Tv is the partial resistance factor for torsional and beam shear strengths, γR,Tv = 1,05. . No further reproduction or distribution permitted. Printed / viewed by: 263 A.12.5.3 Tubular member combined strength checks A.12.5.3.1 Axial tension and bending strength check Tubular members subjected to combined axial tension and bending should satisfy the conditions given in Formulae (A.12.5-18) at all cross-sections along their length: 1−cos􀵬𝜋𝜋2𝛾𝛾R,Tt𝑃𝑃ut𝐴𝐴𝐹𝐹y,T􀵰+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b≤1,0 and 𝛾𝛾R,Tt𝑃𝑃ut≤ 𝐴𝐴𝐹𝐹y,T (A.12.5-18) where, in addition to the previously defined variables Put is the axial tensile force due to factored actions; A is the gross cross-sectional area; Fy,T is the yield strength in stress units as defined in A.12.5.2.1; Muy, Muz are the bending moments due to factored actions about member y- and z-axes, respectively, determined in an analysis that includes global P-Δ; Mb is the representative bending moment strength, as defined in Formula (A.12.5-13); γR,Tt is the partial resistance factor for axial tensile strength, γR,Tt = 1,05; γR,Tb is the partial resistance factor for bending strength, γR,Tb = 1,05. NOTE If 𝛾𝛾R,Tt𝑃𝑃ut>𝐴𝐴𝐴 y,T Formula (A.12.5-18) is not an appropriate measure of member utilization. A measure of the member utilization, U, can be obtained by calculating 𝑈𝑈=𝛾𝛾R,Tt𝑃𝑃ut𝐴𝐴𝐹𝐹y,T+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b A.12.5.3.2 Axial compression and bending strength check Tubular members subjected to combined axial compression and bending should satisfy the conditions given in Formulae (A.12.5-19) and (A.12.5-20) at all cross-sections along their length: beam-column check: (γR,Tc Puc/Pa) + (γR,Tb/Mb) (Muay2 + Muaz2)0,5 ≤ 1,0 (A.12.5-19) and local strength checks: 1−cos􀵬𝜋𝜋2𝛾𝛾R,Tc𝑃𝑃uc𝑃𝑃yc􀵰+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b≤1,0 and 𝛾𝛾R,Tc𝑃𝑃uc≤𝑃𝑃yc (A.12.5-20) where Puc is the axial compressive force due to factored actions; Pyc is the representative local buckling strength in A.12.5.2.4; Pa is the representative axial compressive strength as determined in A.12.5.2.5; Muay is the amplified bending moment about the member y-axis due to factored actions as determined in A.12.4.3; Muaz is the amplified bending moment about the member z-axis due to factored actions as determined in A.12.4.3; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 264 © ISO 2023 – All right reserved Mb is the representative bending moment strength, as defined in Formula (A.12.5-13); γR,Tb is the partial resistance factor for bending strength, γR,Tb = 1,05; γR,Tc is the partial resistance factor for axial compressive strength, γR,Tc = 1,15. NOTE If 𝛾𝛾R,Tc𝑃𝑃uc > 𝑃𝑃yc Equation A.12.5-20 is not an appropriate measure of member utilization. A measure of the member local strength utilization, U, can be obtained by calculating 𝑈𝑈=𝛾𝛾R,Tc𝑃𝑃uc𝑃𝑃yc+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b . A.12.5.3.3 Combined axial tension or compression, bending, shear and torsion strength check The effect of shear on the strength of tubular members subjected to axial tension or compression or bending can be ignored if Formula (A.12.5-21), using the definitions of A.12.5.2.8, is satisfied: 𝑉𝑉≤0,7 𝑃𝑃v𝛾𝛾R,Tv (A.12.5-21) If Formula (A.12.5-21) is not satisfied, reduced representative strengths should be calculated. The unreduced and reduced tensile strengths, AFy,T,v, are given by Formula (A.12.5-22) 𝐴𝐴𝐴 y,T,v=𝐴𝐴𝐹𝐹y,T if 𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv≤0,7 𝐴𝐴𝐴 y,T,v=􀵥0,7+1,2𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv􀵭1−𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv􀵱􀵩𝐴𝐴𝐴 y,T if 𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv>0,7 (A.12.5-22) the unreduced and reduced representative local buckling strengths, Pyc,v, are given by Formula (A.12.5-23): 𝑃𝑃yc,v=𝑃𝑃yc if 𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv≤0,7 𝑃𝑃yc,v=􀵥0,7+1,2𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv􀵭1−𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv􀵱􀵩𝑃𝑃yc if 𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv>0,7 (A.12.5-23) and the unreduced and reduced representative bending moment strengths, Mb,v, are given by Formula (A.12.5-24): 𝑀𝑀b,v= 𝑀𝑀b if 𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv≤0,7 𝑀𝑀b,v=􀵥0,7+1,2𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv􀵭1−𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv􀵱􀵩𝑀𝑀b if 𝑉𝑉𝑃𝑃v𝛾𝛾R,Tv>0,7 (A.12.5-24) NOTE 1 Formulae (A.12.5-22), (A.12.5-23) and (A.12.5-24) demonstrate that the reduced tensile strength, reduced local buckling strength and reduced bending strength equate to 70 % of their representative strengths even when fully utilized in shear. Consequently, combinations of axial tension, bending and shear should satisfy Formula (A.12.5-25): 1−cos􀵬𝜋𝜋2𝛾𝛾R,Tt𝑃𝑃ut𝐴𝐴𝐹𝐹y,T,v􀵰+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b,v≤1,0 and 𝛾𝛾R,Tt𝑃𝑃ut ≤ 𝐴𝐴𝐹𝐹y,T,v (A.12.5-25) . No further reproduction or distribution permitted. Printed / viewed by: 265 NOTE 2 If 𝛾𝛾R,Tt𝑃𝑃ut > 𝐴𝐴𝐹𝐹y,T,v Equation (A.12.5-25) is not an appropriate measure of member utilization. A measure of the member utilization, U, can be obtained by calculating U = 𝛾𝛾R,Tt𝑃𝑃ut𝐴𝐴𝐹𝐹y,T,v+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b,v Combinations of axial compression, bending and shear should satisfy Formulae (A.12.5-26) and (A.12.5-27): 𝛾𝛾R,Tc𝑃𝑃uc𝑃𝑃a+𝛾𝛾R,Tb􀵫𝑀𝑀uay2+𝑀𝑀uaz2􀵯0,5𝑀𝑀b,v≤1,0 (A.12.5-26) 1−cos􀵬𝜋𝜋2𝛾𝛾R,Tc𝑃𝑃uc𝑃𝑃yc,v􀵰+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b,v≤1,0 and 𝛾𝛾R,Tc𝑃𝑃uc≤𝑃𝑃yc (A.12.5-27) In Formula (A.12.5-26), the axial compression strength, Pa, should be calculated from Formula (A.12.5-10) using Pyc,v instead of Pyc. NOTE 3 If 𝛾𝛾R,Tc𝑃𝑃uc>𝑃𝑃yc then Formula (A.12.5-27) is not an appropriate measure of member utilization. A measure of the local strength member utilization, U, can be obtained by calculating 𝑈𝑈=𝛾𝛾R,Tc𝑃𝑃uc𝑃𝑃yc+𝛾𝛾R,Tb􀵫𝑀𝑀uy2+𝑀𝑀uz2􀵯0,5𝑀𝑀b,v . A.12.6 Strength of non-circular prismatic members A.12.6.1 General The structural strength provisions for rolled and welded non-circular prismatic members are generally based on the AISC (2005)[13]. The AISC (2005)[13] specification for LRFD was interpreted and, in some cases, modified for use in the assessment of mobile jack-up structures. The strength formulae for column buckling for lower strength steels in A.12.6.2.4 were modified for consistency with the approach used for higher strength steels, which was taken from Galambos (1998)[75]. Interpretation of the specifications was necessary to enable presentation of a straightforward method for the assessment of beam-columns with components of varying yield strength and/or with cross-sections having only a single axis of symmetry. Development of the specifications was necessary to provide the following: a) a method to deal with member cross-sections comprising components constructed of steels with different yield strengths; b) a method for the assessment of beam-columns under biaxial bending to overcome a conservatism that has been identified in the standard AISC interaction formulae. The yield strength used in A.12.6 should be as specified in A.12.2.2. The effects of hydrostatic loading on non-circular prismatic members should be considered. The critical condition for hydrostatic loading on non-circular prismatic chord members is likely to occur when high spudcan fixity results in high chord axial loads in deep water. Hydrostatic pressure effects on split tubular and similar members should be addressed as described in A.12.5.1. If the section fails to meet the un-reinforced tubular check, additional analysis can be used to determine the effects of the stiffening provided by the non-tubular components. Hydrostatic pressure effects on flat plate components of members should be assessed as shown in Figure A.12.6-1 for values of β less than 2,0. If the component is used under conditions with an equivalent head of water greater than the limiting equivalent head of water given in Figure A.12.6-1, or if the calculated β is greater than 2,0, then rational analysis should be used to assess the effects of hydrostatic pressure on member utilization. For convenience, Table A.12.6-1 gives the limiting equivalent head of water for components of differing plate slendernesses. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 266 © ISO 2023 – All right reserved dw,lim = 298β4 − 2 092β3 + 5 542β2 − 6 603β + 3 025 for β ≤ 2,0 Key b width of base plate t thickness of base plate dw,lim limiting equivalent head of water in metres for which additional analysis is not required; it is the depth below the water surface (including penetration into the seabed where applicable) plus the additional soil pressure pγ′/(ρwg) β plate slenderness parameter β = (b/t)(Fy/E)0,5 p is the depth below the sea floor in metres (zero if above sea floor) γ ′ is the submerged (effective) unit weight of the soil ρw is the mass density of water Figure A.12.6-1 — Example chord showing plate dimensions for hydrostatic pressure screening check Table A.12.6-1 — Maximum plate slenderness parameter β for given equivalent head of water Equivalent head of water dw,lim m Maximum plate slenderness parameter β 170 1,0 120 1,1 85 1,2 48 1,4 32 1,6 24 1,8 20 2,0 In A.12.6.2 and A.12.6.3, y and z are used to define the axes of a non-circular prismatic member. A.12.6.2 Non-circular prismatic members subjected to tension, compression, bending or shear A.12.6.2.1 General Non-circular prismatic members subjected to axial tension, axial compression, bending or shear should satisfy the applicable strength and stability checks specified in A.12.6.2.2 to A.12.6.2.7. A.12.6.2.2 Axial tensile strength check Non-circular prismatic members subjected to axial tensile forces, Put, due to factored actions should satisfy Formula (A.12.6-1): Put ≤ Pt/γR,Pt (A.12.6-1) . No further reproduction or distribution permitted. Printed / viewed by: 267 where Pt is the representative axial tensile strength of a non-circular prismatic member, calculated as given in Formula (A.12.6-2) Pt = Σ(FyiAi) (A.12.6-2) Fyi is the yield strength of the ith component of the cross-section of a prismatic member, in stress units, as defined in A.12.2.2; Ai is the cross-sectional area of the ith component comprising the structural member; γR,Pt is the partial resistance factor for axial tensile strength, γR,Pt = 1,05. A.12.6.2.3 Axial compressive local strength check Non-circular prismatic members subjected to axial compressive forces, Puc, due to factored actions should satisfy Formula (A.12.6-3): Puc ≤ Ppl/γR,Pcl (A.12.6-3) where, in addition to the definitions given in A.12.6.2.2 γR,Pcl is the partial resistance factor for local axial compressive strength, γR,Pcl = 1,1; Ppl is the representative local axial compressive strength of a non-circular prismatic member as given in Formulae (A.12.6-4) to (A.12.6-6); Ppl = ΣFyiAi for class 1 and class 2 members (A.12.6-4) Ppl = ΣFyiAi − (ΣFyiAi − FyminΣAi)hprphλλλλ−− for class 3 members (A.12.6-5) Ppl = FyminAc for class 4 members (A.12.6-6) Fymin is the minimum yield stress of the Fyi of all components in the cross-section of a prismatic member, in stress units, as defined in A.12.2.2; Ai is the cross-sectional area of the ith component comprising the structural member; Ac is the cross-sectional area for use in the assessment of a non-circular prismatic member as defined in A.12.3.5.2; h is the subscript referring to the component that produces the smallest value of Ppl; λh = b/t or 2R/t as applicable for component h, with effective width b, or outside radius R; λp is as determined for component h from Tables A.12.2-2 to A.12.2-4 as given in Formulae (A.12.6-7) to (A.12.6-10):  for rectangular rolled or welded web or flange components supported along both edges: . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 268 © ISO 2023 – All right reserved py117,/iEFλ= (A.12.6-7)  for rectangular rolled flange or web components supported along one edge: py037,/iEFλ= (A.12.6-8)  for rectangular welded flange or web components supported along one edge: py033,/iEFλ= (A.12.6-9)  for components derived from tubulars (with reference to Table A.12.2-1): p0077,/yiEFλ= (A.12.6-10) λr is determined for component h from Tables A.12.2-2 to A.12.2-4 as given in Formulae (A.12.6-11) to A.12.6-14):  for rectangular rolled or welded web or flange components supported along both edges: ry144,/iEFλ= (A.12.6-11)  for rectangular rolled flange or web components supported along one edge: ry055,/iEFλ= (A.12.6-12)  for rectangular welded flange or web components supported along one edge: ry050,/iEFλ= (A.12.6-13)  for components derived from tubulars (with reference to AISC (2005)[13] and Table A.12.2-1): r0102,/yiEFλ= (A.12.6-14) The eccentricity between the elastic and plastic neutral axes, ea, for class 3 members (see A.12.4) can be calculated as given in Formula (A.12.6-15): rharpheeλλλλ−=− (A.12.6-15) where e is as defined in A.12.4.2, but calculated for the cross section as if it were class 1 or 2. A.12.6.2.4 Axial compressive column buckling strength There is no axial compressive column buckling strength check because it is inherent in the combined strength check for compression in A.12.6.3. However, the representative axial compressive strength of . No further reproduction or distribution permitted. Printed / viewed by: 269 all member classifications subjected to flexural buckling should be determined as given Formulae (A.12.6-16) to (A.12.6-19): a) for all grades of steel (conservative for high strength steel): 2cnpl0658 ,PPλ= for λc ≤ 1,5 [derived from AISC (2005)[13], Formula E3-2] (A.12.6-16) ()2ncpl0877,PPλ= for λc > 1,5 [derived from AISC (2005)[13], Formula E3-3] (A.12.6--17) b) alternatively, for high-strength steels (Fy > 450 MPa), the following may be used (see F.1): 322cnpl07625,,PPλ= for λc ≤ 1,2 (A.12.6-18) ()1854ncpl08608,,PPλ= for λc > 1,2 (A.12.6-19) where, in addition to the definitions in A.12.6.2.3, 05plcE,PPλ= (derived from AISC (2005)[13], Ch. E3; see also F.1) (A.12.6-20) PE is the minimum Euler buckling load for any plane of bending, as defined in A.12.4.3 (including percentage of rack teeth of chords; see A.12.3.1). When section contains un-reinforced cut-outs, the slenderness parameter, λc, should be based on the minimum section unless otherwise determined by analysis. A.12.6.2.5 Bending moment strength A.12.6.2.5.1 General The classification of member cross-sections in A.12.2 is used to identify the potential for local buckling. The slender section properties determined in A.12.3.4 account for the local buckling of class 4 cross-sections. The bending moment strength of typical closed section jack-up chord members used in truss legs is not normally limited by lateral torsional buckling. However, this should be checked as described in A.12.2.3.2. A.12.6.2.5.2 Class 1 plastic and class 2 compact section bending moment strength The representative bending moment strength, Mb, is given by the plastic bending moment of the entire section as given in Formula (A.12.6-21): Mb = ZpFymin (A.12.6-21) where Mb is the representative bending moment strength; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 270 © ISO 2023 – All right reserved Zp is the fully plastic effective section modulus, determined from Formula (A.12.3-2); Fymin is the minimum yield strength of all components in the cross-section of a prismatic member, in stress units, as defined in A.12.2.2. NOTE Hybrid sections built up from components of different yield strengths are addressed by the methodology described in A.12.3.2. A.12.6.2.5.3 Class 3 semi-compact section bending moment strength The representative bending strength, Mb, is obtained by interpolating between the plastic bending moment and the limiting buckling moment as given in Formula (A.12.6-22): ()hpbppRrphMMMMλλλλ−=−−− (A.12.6-22) where, in addition to the definitions in A.12.6.2.5.2 Mp is the plastic moment strength; Mp = ZpFymin as calculated by Formula (A.12.6-21); MR = Sf Fy < Mp (A.12.6-23) Sf is the elastic section modulus of a semi-compact section of a non-circular prismatic member for the plane of bending under consideration; see A.12.3.3; Fy is the yield strength of the material at the critical point in the cross-section, determined when calculating the section modulus (see A.12.3.3); h is the subscript referring to the component which produces the smallest value of Mb; λh = b/t or 2R/t as applicable for component h; λp is as determined for component h from Tables A.12.2-2 to A.12.2-4, as given in Formulae (A.12.6-24) to (A.12.6-29):  for rectangular rolled or welded flange components supported along both edges when the bending results in uniform compression: py117,(/)iEFλ= (A.12.6-24)  for rectangular rolled flange or web components supported along one edge and subject to combinations of compression and bending: py037,(/)iEFλ= (A.12.6-25)  for rectangular welded flange or web components supported along one edge and subject to combinations of compression and bending: py033,(/)iEFλ= (A.12.6-26) . No further reproduction or distribution permitted. Printed / viewed by: 271  for rectangular rolled or welded web components supported along both edges and subject to combinations of compression and bending: py4825121,(/)/(,)iEFλα=− (for α > 0,5) (A.12.6-27) py155,(/)/iEFλα= (for α ≤ 0,5) (A.12.6-28) where α is a factor that varies depending on the applied loading, given in Table A.12.2-4, and equals 0,5 in bending, 1,0 in compression, and variable between these values for combined bending and compression.  for components derived from circular tubes and subject to pure bending (see Table A.12.2-1): p0103,/yiEFλ= (A.12.6-29) When the location of the tubular component results in combined bending and compression the value of λp can conservatively be taken from Formula (A.12.6-10). Alternatively, the value of λp may be interpolated between the values for pure bending and pure compression. λr is determined for component h from Tables A.12.2-2 to A.12.2-4, as given in Formulae (A.12.6-30) to (A.12.6-35):  for rectangular rolled or welded flange components supported along both edges when the bending results in uniform compression: ry144,(/)iEFλ= (A.12.6-30)  for rectangular rolled flange or web components supported along one edge and subject to combinations of compression and bending: ry055,(/)iEFλ= (A.12.6-31)  for rectangular welded flange or web components supported along one edge and subject to combinations of compression and bending: ry050,(/)iEFλ= (A.12.6-32)  for rectangular rolled or welded web components supported along both edges and subject to combinations of compression and bending: ()ry14406740327,(/)/,,iEFλψ=+ (for ψ > −1,0) (A.12.6-33) ()()()r2071,/ yiEFλψψ√−=− (for ψ ≤i−1,0) (A.12.6-34) where ψ is the stress ratio as shown in Table A.12.2-4. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 272 © ISO 2023 – All right reserved  for components derived from circular tubes and subject to pure bending (see Table A.12.2-1): r022,/yiEFλ= (A.12.6-35) When the location of the tubular component results in combined bending and compression, the value of λr can conservatively be taken from Formula (A.12.6-14). Alternatively, the value of λr may be interpolated between the values for pure bending and pure compression. A.12.6.2.5.4 Class 4 slender-section bending moment strength The representative bending moment strength, Mb, of class 4 sections is given by the limiting flexural bending moment in Formula (A.12.6-36): Mb = Se Fy (A.12.6-36) where Se is the reduced elastic section modulus of a slender section of a non-circular prismatic member for the plane of bending under consideration, see A.12.3.4.3 and Fy is the yield strength of the material at the critical point in the cross-section, determined when calculating the section modulus (see A.12.3.3). A.12.6.2.6 Bending moment strength affected by lateral torsional buckling The reduced representative bending moment strength Mb due to LTB should be calculated for all members that do not meet the screening checks of either Formula (A.12.2-2) or Formula (A.12.2-3) for open and closed sections, respectively, regardless of the class of section. When the representative bending moment strength is reduced due to LTB compared to the strength calculated in A.12.6.2.5, the reduced bending moment strength should be used in the strength checks. Further guidance on the bending moment strength accounting for LTB can be found in the AISC Specification (2005)[13] and BS 5400-3. A.12.6.2.7 Bending strength check Non-circular prismatic members subjected to bending moments, Mu, should satisfy Formula (A.12.6-37): Mu ≤ Mb/γR,Pb (A.12.6-37) where Mu is Muy or Muz, the bending moment due to factored actions about member y- and z-axes, respectively; Mb is the representative bending moment strength, determined from A.12.6.2.5 and A.12.6.2.6; γR,Pb is the partial resistance factor for bending, γR,Pb = 1,1. . No further reproduction or distribution permitted. Printed / viewed by: 273 A.12.6.3 Non-circular prismatic member combined strength checks A.12.6.3.1 General There are two different assessment approaches for the strength of non-circular prismatic members subjected to combined axial forces and bending moments: a) the interaction formula approach (see A.12.6.3.2), which is applicable to all member classifications; b) the plastic interaction surface approach (see A.12.6.3.3), which is applicable to members in class 1 and class 2. A.12.6.3.2 Interaction formula approach Each non-circular prismatic structural member should satisfy the following conditions in Formulae (A.12.6-38) to (A.12.6-40) at all cross-sections along its length. When the shear due to factored actions is greater than 60 % of the shear strength, the bending moment strength should be reduced parabolically to zero when the shear equals the shear strength (Pv in A.12.6.3.4). Local strength check (for all members) is as given in Formula (A.12.6-38): 1R,PbueyR,PauR,Pbuezplsbybz1,0MPMPMMηηηγγγ++≤ (A.12.6-38) Beam-column check (for members subject to axial compression) is as given in Formula (A.12.6-39) or Formula (A.12.6-40):  if γR,PaPu/Pp > 0,2, then (after AISC (2005)[13], Formula H1-1a) 1R,PbuayR,PauR,Pbuazpbybz81,09MPMPMMηηηγγγ++≤ (A.12.6-39)  if γR,PaPu/Pp ≤ 0,2, then (after AISC (2005)[13], Formula H1-1b) 1R,PbuayR,PauR,Pbuazpbybz1,02MPMPMMηηηγγγ++≤ (A.12.6-40) where Pu is the applied axial force in a member due to factored actions, determined in an analysis that includes P-Δ effects (see A.12.4); Ppls is the representative local axial strength of a non-circular prismatic member where Ppls = Pt for members in tension, as defined A.12.6.2.2, . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 274 © ISO 2023 – All right reserved Ppls = Ppl for members in compression, as defined A.12.6.2.3; Pp is the representative axial strength of a non-circular prismatic member where Pp = Pn for members in compression, as defined A.12.6.2.4; Muey is the corrected bending moment due to factored actions about the member y-axis from A.12.4; Muez is the corrected bending moment due to factored actions about the member z-axis from A.12.4; Muay is the amplified bending moment due to factored actions about the member y-axis from A.12.4; Muaz is the amplified bending moment due to factored actions about the member z-axis from A.12.4; Mby is the representative bending moment strength about the member y-axis, as defined in A.12.6.2.5 or A.12.6.2.6; When the shear due to factored actions is greater than 60 % of the shear strength, the bending moment strength should be reduced parabolically to zero when the shear equals the shear strength (Pvz in A.12.6.3.4). For a more detailed description of the method see EN 1993-1-1, Eurocode 3; Mbz is the representative bending moment strength about the member z-axis, as defined in A.12.6.2.5 or A.12.6.2.6; When the shear due to factored actions is greater than 60 % of the shear strength, the bending moment strength should be reduced parabolically to zero when the shear equals the shear strength (Pvy in A.12.6.3.4). For a more detailed description of the method see EN 1993-1-1, Eurocode 3; γR,Pb is the partial resistance factor for bending strength, γR,Pb = 1,1; γR,Pa is the partial resistance factor for axial strength where γR,Pa = γR,Pt for axial tensile strength, γR,Pa = 1,05 in Formulae (A.12.6-38), (A.12.6-39) and (A.12.6-40); γR,Pa = γR,Pcl for axial compressive strength, γR,Pa = 1,1 in Formula (A.12.6-38); γR,Pa = γR,Pc for axial compressive strength, γR,Pa = 1,1 in Formulae (A.12.6-39) and (A.12.6-40). η is the exponent for biaxial bending, a constant dependent on the member cross-section geometry, determined as follows:  for purely circular tubular members η = 2,0;  for solid or hollow rectangular sections η = 5/3;  for doubly symmetric open section members η = 1,0; . No further reproduction or distribution permitted. Printed / viewed by: 275  for all geometries, a conservative value of η = 1,0 may be used. Annex F presents an approach to determining the value of η by manual calculation. The following mapping of the variables should be applied. a) M′uey, M′uez should be set to the applicable of Muey, Muez or Muay, Muaz, respectively, as described above. b) Mny, Mnz should be set to Mby, Mbz, respectively. A.12.6.3.3 Interaction surface approach In the interaction surface approach, the assessor develops a plastic strength interaction surface in terms of the axial strength and biaxial moment strengths. The interaction surface can be based on Dyer (1992)[67] and can be used for the strength checks. The approach is based on axial force applied at the “centre of squash”, which is defined as the location at which the axial force produces no moment on the fully plastic section. IMPORTANT — The assessor should be aware that the sign of the moment is crucially important for sections without material or geometric symmetry. The sign convention should, therefore, be observed with care. NOTE A common case where errors in sign can be introduced is when taking the results of a computer analysis and applying them to a series of parametric formulae that can have a different axis convention. A measure of the interaction ratio can, then, be obtained as the ratio between the vector length from the functional origin to the member forces, and the vector length from the functional origin to the nearest point on the surface. The functional origin is the force point associated with the functional actions in the absence of environmental actions. Annex F provides, by way of example, conservative interaction formulae and curves for generic families of chord cross-sections based on plastic strengths Py, Mpy, and Mpz. The resistance factors should be introduced by the assessor. This is achieved by the definitions as given in Formulae (A.12.6-41) to (A.12.6-43): Py = Ppls/γR,Pa strength check (for all members) (A.12.6-41) or Py = Pp/γR,Pa beam-column check (for members subject to axial compression) Mpy = Mby/γR,Pb (A.12.6-42) Mpz = Mbz/γR,Pb (A.12.6-43) where Mby is the representative bending moment strength, as defined in A.12.6.3.2; Mbz is the representative bending moment strength, as defined in A.12.6.3.2; Pp is the representative axial strength of a non-circular prismatic member, as defined in A.12.6.3.2; Ppls is the representative local axial strength of a non-circular prismatic member, as defined in A.12.6.3.2; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 276 © ISO 2023 – All right reserved γR,Pb is the partial resistance factor for bending strength, γR,Pb = 1,1; γR,Pa is the partial resistance factor for axial strength where γR,Pa = γR,Pt for axial tensile strength, γR,Pt = 1,05; γR,Pa = γR,Pc for axial compressive strength, γR,Pc = 1,1; γR,Pa = γR,Pcl for local strength, γR,Pcl = 1,1. For the strength check, the applied member forces (P, My, Mz in Annex F) should be Pu, Muey, Muez as defined in A.12.6.3.2. For the beam-column check, the applied member forces (P, My, Mz in Annex F) should be Pu, Muay, Muaz as defined in A.12.6.3.2. A.12.6.3.4 Beam shear Non-circular prismatic members subjected to beam shear forces due to factored actions should satisfy Formulae (A.12.6-44) and (A.12.6-45): Vy ≤ Pvy/γR,Pv (A.12.6-44) Vz ≤ Pvz/γR,Pv (A.12.6-45) where Vy, Vz is the beam shear due to factored actions in the local y- and z-direction, respectively; Pvy, Pvz is the representative shear strength in the local y- and z-directions, respectively, as given in Formula (A.12.6-46): Pvy, Pvz = Av Fymin/√3 (A.12.6-46) Av is the effective shear area in the direction being considered; see Table A.12.6-2; γR,Pv is the partial resistance factor for torsional and beam shear strengths, γR,Pv = 1,1. . No further reproduction or distribution permitted. Printed / viewed by: 277 Table A.12.6-2 — Effective shear area for various chord component cross-sections Section Effective shear area, Av Rolled I, H and channel sections, load parallel to web t Ds Welded I sections, load parallel to web t d Rectangular hollow sections, load parallel to webs A Ds/(Ds + Bs) Welded box sections, load parallel to web 2 t d Rolled Tee-sections, load parallel to web t Ds Welded Tee-sections, load parallel to web t (Ds − T) Circular hollow sections with diameter/wall thickness is less than or equal to 60 0,6 A Circular hollow sections with diameter/wall thickness greater than 60 Use rational analysis Solid bars and plates 0,9 A Closed sections with inclined plates 0,9 Σ[cos(θi) Aoi] T is the flange thickness of a welded T-section. t is the web thickness. Ds is the overall depth of cross-section. d is the web depth; for rolled sections measured with respect to root radii, for welded sections measured between inside faces of flanges. Bs is the overall breadth of cross-section. A is the area of cross-section. Aoi is the area of rectilinear component i. θi is the angle between the shear force direction being considered and the larger dimension of the cross-section of component i. The effective shear area of closed-section triangular chords [see Figure A.12.1-1 b)] in the local y- and z-directions, respectively, can be calculated using elastic theory as given in Formula (A.12.6-46): Avy , Avz = (Iv tv)/Q (A.12.6-46) where Ivy , Ivz is the second moment of area of the cross section, excluding rack tooth (see A.12.3.1 and Figure A.12.1-1), about the y- and z- neutral axes, respectively; tvy , tvz is the collective width of components through the cross section at the location to be assessed, perpendicular to the y- and z- axes, respectively; Qy , Qz is the first moment of the area between the cross sectional location to be assessed and the outer fibre, about the neutral axis It can be necessary to calculate effective shear areas at various locations on the cross section in order to determine the maximum shear stress for each axis. The effective shear area of a chord containing split tubular components can be calculated following the examples given in Figure A.12.6-2. Alternatively, other rational methods can be used. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 278 © ISO 2023 – All right reserved Additional information on calculating the shear stresses in a sample of split tubular and triangular cross sections can be found in ISO/TR 19905-2. a) Split tubular with solid rack, full penetration weld of tubular to rack b) Split tubular with solid rack, full penetration weld of tubular to rack, but tubular tapered to reduce wall thickness where connected to the rack c) Split tubular with rack split into two parts connected by backing plate (6) with full penetration welds to back side of each rack component d) Split tubular with rack split into two parts connected by two lapped plates (8) with fillet welds to sides of each rack component Key 1 Structural split tubular part of chord with diameter Dt and wall thickness Tt. The area of cross section, At, is defined below 2 Chord rack of width Wr and thickness Tr 3 Two artificial areas that have maximum dimensions of the thickness of the rack, Tr and the width of the welded contact area between the chord tube and the chord rack, Ttr, with a maximum value of the chord tube wall thickness (Ttr ≤ Tt), as shown in diagram (b) 4 Rack tooth, not part of structural area 5 Two artificial areas through the chord rack that have the thickness of the backing plate (item 6), Tb, and the width of the structural part of each of the two rack sections, Wrs 6 Backing plate of width Wb and thickness Tb that has continuous full penetration welds to the backside of each rack chord rack section 7 Two rack sections, one on each side of the chord with dimensions Wrs width and Tr thickness . No further reproduction or distribution permitted. Printed / viewed by: 279 8 Two lap plates connecting the two sections of chord rack X Axis parallel to the chord rack Y Axis perpendicular to the chord rack At Area of cross section of the split tubular components of the member to be used in determining Avx and Avy. In diagrams (a), (c), and (d), At is the total area of cross section of both halves of the split tubular components having diameter Dt and wall thickness Tt. In diagram (b) At is the effective area of cross section of both halves of the split tubular components with diameter Dt but with a wall thickness Ttr Avx Shear area in the X direction. The value of Avx can be determined from rational analysis. In lieu of such analysis, the following values may be used: Diagram (a) Avx = 0,9 Dt Tr + 0,6 At Diagram (b) Avx = 0,9 Dt Tr + 0,6 At Diagram (c) Avx = 0,6 At Diagram (d) Avx = 0,6 At Avy Shear area in the Y direction. The value of Avy can be determined from rational analysis. In lieu of such analysis, the following values may be used: Diagram (a, b) Avy = 0,6 At + 0,9 Tr Wr Diagram (c, d) Avy = 0,6 At + 2(0,9 TrIr) In diagrams (c), & (d) Ttr = Tt Figure A.12.6-2 — Examples of shear areas of leg chords containing split tubular components A.12.6.3.5 Torsional shear Closed-section non-circular prismatic members subjected to torsional shear forces due to factored actions should satisfy Formula (A.12.6-47): Tu ≤ Tvp/γR,Pv (A.12.6-47) where Tu is the torsional moment due to factored actions; Tvp is the representative torsional strength of the non-circular prismatic member as given in Formula (A.12.6-48): Tvp = Ipp Fymin/(rt √3) (A.12.6-48) Ipp is the polar moment of inertia of the non-circular prismatic member; rt is the maximum distance from centroid to an extreme fibre; γR,Pv is the partial resistance factor for torsional and beam shear strengths, γR,Pv = 1,1. Open-section non-circular prismatic members subjected to torsional shear forces should be checked as appropriate. A.12.7 Assessment of joints Joints should be assessed when the site conditions (metocean combinations, eccentric spudcan loading, etc.) fall outside the limits that are normally assessed by the RCS. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 280 © ISO 2023 – All right reserved The designer can make joint strengths available to the assessor. When the supplied axial joint strength is less than the member strength, the supplied joint strength should be used in lieu of the member axial strength in member strength checks. If it is considered necessary to evaluate joint strength, the resistance of tubular joints can be assessed in accordance with ISO 19902:2020, 14 and A.14 (Strength of tubular joints), and that of non-tubular joints by rational analysis. The internal forces (action effects) due to factored actions should be determined in accordance with 8.8, rather than using ISO 19902 and ISO 19901-3. NOTE The intent of the joint check is to ensure that the joint is strong enough to resist the internal forces due to factored actions. The joint strength is not required to meet or exceed the full member strength. Guidance on non-tubular joint strength can be found in other provisions of ISO 19902 and ISO 19901-3. A.13 Guidance on acceptance checks No guidance is offered. . No further reproduction or distribution permitted. Printed / viewed by: 281 Annex B (normative) Summary of partial action and partial resistance factors Table B-1 — Summary of partial action factors Symbol Description Factor Subclause(s) γf,D partial action factor applied to the inertial actions De due to dynamic response, in combination with γf,E 1,0 8.8.1.1 to 8.8.1.4 γf,G partial action factor applied to the fixed actions GF 1,0 8.8.1 γf,V partial action factor applied to the actions due to variable load Gv 1,0 8.8.1 γf,E partial action factor applied to the metocean or earthquake actions 8.8.1.1 to 8.8.1.4 when applied to deterministic ULS storm action Ee (used with 50 year independent extreme values) 1,15 8.8.1.2 when applied to the deterministic ULS storm action Ee (used with 100 year joint probability metocean data) 1,25 8.8.1.2 when applied to the stochastic ULS storm actions Ee using factored metocean parameters determined in accordance with A.10.5.3.2a 1,0 8.8.1.3 when applied to the inertial action induced by the ELE ground motions in earthquake analysis 0,9 8.8.1.4.1 when applied to the inertial action induced by the ALE ground motions in earthquake analysis 1,0 8.8.1.4.2 NOTE The reference subclauses provide the methods of application and the factors are specifically tied to the calculation methodologies given in each reference subclause. a The metocean partial factors used in the quasi-static stochastic analysis are determined through an iterative procedure. The procedure involves factoring the metocean parameters (wave height, current velocity and wind) until the partial-factored quasi-static stochastic force matches the action-factored quasi-static deterministic force. The start point for the iteration can be taken as (γf,E)0,5. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 282 © ISO 2023 – All right reserved Table B-2 — Summary of partial resistance factors Symbol Partial resistance and material factor description Factor Subclause where the factor can be used γm partial material factor for calculated foundation capacities 1,25 E.4.6 γR,PRE partial resistance factor for preload 1,1 A.9.3.6.2 γR,Hfc partial resistance factor for horizontal foundation sliding capacity for effective stress (sand/drained) 1,25 A.9.3.6.2 partial resistance factor for horizontal foundation sliding capacity for total stress (clay/undrained) 1,25 A.9.3.6.2 partial resistance factor for horizontal foundation sliding capacity when considering material factored representative soil strength 1,0 E.4.8 γR,VH partial resistance factor for vertical-horizontal foundation bearing capacity 1,1 A.9.3.6.4 partial resistance factor for vertical-horizontal foundation bearing capacity when considering material factored representative soil strength 1,0 E.4.7 γR,Tb partial resistance factor for bending strength of a tubular membera 1,05 A.12.5 γR,Tc partial resistance factor for axial compressive strength of a tubular membera 1,15 A.12.5 γR,Tt partial resistance factor for axial tensile strength of a tubular membera 1,05 A.12.5 γR,Tv partial resistance factor for torsional and beam shear strengths of a tubular membera 1,05 A.12.5 γR,Pb partial resistance factor for bending strength prismatic of a non-circular prismatic membera 1,1 A.12.6 γR,Pc partial resistance factor for axial compressive strength of a non-circular prismatic membera 1,1 A.12.6 γR,Pcl partial resistance factor for local axial compressive strength of a non-circular prismatic membera 1,1 A.12.6 γR,Pt partial resistance factor for axial tensile strength of a non-circular prismatic membera 1,05 A.12.6 γR,Pv partial resistance factor for torsional and beam shear strengths of a non-circular prismatic member 1,1 A.12.6 γR,S partial resistance factor for spudcan strength 1,15 13.4 γR,H partial resistance factor for holding system 1,15 13.5 γR,OTM partial resistance factor for stabilizing moment 1,05 13.8 NOTE The requirements for partial factors are given in the normative clauses e.g. 9.3.6, 12.5, 12.6, etc. however examples of the specific application of these factors are given in Annexes A and E in the subclauses shown above. The reference subclauses provide the methods of application and the factors are specifically tied to the calculation methodologies given in each reference subclause. a The structural resistance factors for tubular members given here and referenced in Clause 12 are based on an independent interpretation of the theoretical values derived from the data used in the calibration of API RP 2A LRFD 1st edition to API RP 2A 15th edition and the data used in the development of the ISO 19902 tubular members strength formulations. The values for non-tubular prismatic members were based on AISC (2005)[13] which changed its equivalent resistance factor from 1,18 to 1,1 between the 1986 and 2005 editions because a reassessment of the applicable data resulted in an effective reduction in the coefficient of variation. . No further reproduction or distribution permitted. Printed / viewed by: 283 Annex C (informative) Additional information on structural modelling and response analysis C.1 Guidance on 8.5 — Modelling the leg-to-hull connections The potential leg-to-hull connection component arrangements are shown in Figure C.1-1, which also gives examples of jack-ups designs in each category. Examples of jack-ups in each category FandG - L780 II - JU 2000 - Alpha 350 - Super M2 - Universal M class GustoMSC - CJ 46 - CJ 50 (new) Hitachi - Giant class Keppel FELS - KFELS Mod V - KFELS Mod VI - A Class - B Class - N Class LeTourneau - Super GORILLA - Super GORILLA XL - Jaguar 250-C GustoMSC - CJ36 - CJ46 - CJ50 (old) - CJ54 - CJ62 - CJ70 NONE NONE Baker Marine - Pacific 375 LeTourneau - Workhorse - Tarzan Modec - 300C - 400 CFEM - 2005 - 2600 Levingston - 111C Baker Marine - Freedom class - 350 - 300 - 250 - 200 - 150 GustoMSC - Gusto designs LeTourneau - 53 - 84 - 82-SD-C - 116C - Super 116 - Super 116E - Super 300 - Gorilla NONE Figure C.1-1 — Sample leg-to-hull connection component combinations . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 284 © ISO 2023 – All right reserved C.2 Guidance on A.10.5.3.4 — Methods for determining the MPME C.2.1 Guidance on the first method of Table A.10.5-1 — Fitting Weibull distributions to the results of a number of time domain simulations to determine responses at the required probability level and average the results This procedure, outlined in Steps 1 to 7 below, requires several suitable length time domain simulations for each response of interest. The input sea state simulation should be checked for Gaussianity. Guidance is given in Table A.7.3-3. For each simulation record, the procedure for computing the MPME comprises the following steps. The final MPME value is taken as the average over all of the simulations conducted.  Step 1: The response time history, R(t), is first analysed to calculate the mean, μR, as given in Formula (C.2.1-1): 1R()niiRtnμ==Σ (C.2.1-1) where R(ti) is the time history of the response of interest; ti is the time point i; n is the number of useable time points in simulation (discounting the run-in).  Step 2: The individual response maxima in the simulations are next extracted in accordance with the following criteria: A maximum occurs at ti if Formula (C.2.1-2) apply: R(ti−1) < R(ti) and R(ti+1) ≤ R(ti) (C.2.1-2) Suppose Nmax maxima are found in the extraction.  Step 3: From the Nmax response maxima, the mean of the signal, μR, is subtracted and the resulting maxima Mk, where k varies from 1 to Nmax, are ranked into 20 blocks having mid-points in ascending order. The blocks all have the same width; the upper bound of block 20 is taken as 1,01 times the largest value, and the lower bound of the first block is set to zero. Any maxima with a value less than zero are discarded. The blocks are numbered in ascending order from q = 1 to 20, and are defined by their midpoint value M*q and the probability of non-exceedance of that value Fq. A distribution of the observed maxima is then found, using for each block the Gumbel plotting position in order to obtain the best possible description of the distribution for large values of M. If the number of maxima in each block, q, is nq, the cumulative probability Fq to plot against the mid-point for block q is then as given in Formula (C.2.1-3): . No further reproduction or distribution permitted. Printed / viewed by: 285 ()0510011,maxqqqjjjjFnnN−===++ΣΣ (C.2.1-3) where n0 is equal to the number of negative maxima peaks (the number of points not fitting into the 20 blocks).  Step 4 a): A Weibull distribution is fitted [see Steps 4 b) to 4 d)] through the cumulative distribution of the blocks of observed maxima as defined under Step 3 [this is done in accordance with Steps 4 b) to 4 d)]. The 3-parameter Weibull cumulative distribution function is defined as given in Formula (C.2.1-4): 1*(*;,,)expMFMβγαβγα−=−− (C.2.1-4) where (*;,,)FMαβγ is the probability of non-exceedance of the value M* where α is the scale parameter, β is the slope parameter, γ is the threshold parameter. 00,,(*),Mαβγ−>  Step 4 b): Only data blocks with a probability of non-exceedance greater than a threshold value of 0,2 are used to fit the Weibull distribution, i.e. only the blocks for which Formula (C.2.1-5) applies: Fq > 0,2 (C.2.1-5) Notice that qM* are in ascending order.  Step 4 c): For each of these blocks, q, the deviations, δ q, of the observed probability from the corresponding probability of the Weibull cumulative distribution function, F, (transformed to Weibull scales) are calculated as given in Formula (C.2.1-6): δq = ln{−ln[1 − F(*qM;α,β,γ)]} − β [ln(*qM − γ) − ln(α)] (C.2.1-6)  Step 4 d): The parameters α, β, γ are now estimated by a non-linear least squares technique such that the summation as given in Formula (C.2.1-7) is minimized: . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 286 © ISO 2023 – All right reserved 202qqxδ=Σ where x is the value of q for which Fq > 0,2. (C.2.1-7) The procedure may be based on a Levenberg-Marquardt algorithm, using the parameters of a 2-parameter Weibull distribution (found by the maximum likelihood method) as initial estimates.  Step 5: The MPM value, MMPM, is found as the value of M for which Formula (C.2.1-8) applies: 3hmaxsim11(*;,,)FMTNTαβγ=− (C.2.1-8) where T3h is 3 hours; Tsim is the simulation duration.  Step 6: The corresponding MPME value, RMPME is then found as given in Formula (C.2.1-9): RMPME = μ R + MMPM (C.2.1-9) where μ R is the mean value of R(t) established in Step 1; MMPM is the MPME value (excluding the mean) established in Step 5.  Step 7: The procedure is repeated for each required response parameter. C.2.2 Guidance on the second method of Table A.10.5-1: Fitting Gumbel distribution to histogram of absolute maximum responses from a number of time domain simulations to determine responses at required probability level The basic assumption of this method is that the absolute maximum values in three-hour simulations follow a Gumbel distribution as given in Formula (C.2.2-1): 3h()expexpxFxψκ−=−− (C.2.2-1) where F3h(x) is the probability that the three-hour maximum does not exceed value x; . No further reproduction or distribution permitted. Printed / viewed by: 287 ψ is the location parameter; κ is the scale parameter. The following steps are followed for each required response parameter:  Step 1: Extract absolute maximum (and minimum) value for each of at least ten three-hour response simulations.  Step 2: Fit a Gumbel distribution through these 10 or more maxima/minima. This can be done using the maximum likelihood method, yielding ψ and κ. Alternatively, Lu et al. (2001)[129] have shown that the method of moments closed form solution produces results consistent with the maximum likelihood method for values of ψ, although they showed significant variation in the values of κ. However, when calculating the MPME, with a 63 % probability of exceedance, the effects of κ approach zero, as shown in Step 3 below, and the only remaining influence is on the calculated value of ψ, as given in Formula (C.2.2-3). Therefore, the method of moments closed form solution normally can be used to calculate ψ and κ: as given in Formulae (C.2.2-2) and (C.2.2-3): κ = (σ √6)/π (C.2.2-2) ψ = μ − 0,577κ (C.2.2-3) where μ is the mean of the maxima/minima; σ is the standard deviation of the maxima/minima.  Step 3: The value RMPME is found as given in Formulae (C.2.2-4) and (C.2.2-5): {}MPME3hMPMEInln()RFRψκ=−− (C.2.2-4) where F3h (RMPME) = 0,37 (C.2.2-5) The 0,37 lower quantile is used because the extreme of recurrence of once in three hours has a probability of exceedance of 0,63 (= 1 − 0,37). In this case, it can be seen that RMPME = ψ  Step 4: The procedure of Steps 2 and 3 can similarly be applied for minima although, because of the potential error in κ, and because the standard deviation of the minima can be large by comparison to the mean, the method of moments should not be used for calculating κ and ψ. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 288 © ISO 2023 – All right reserved C.2.3 Guidance on the third method of Table A.10.5-1 — Application of Winterstein's Hermite polynomial method to the results of time domain simulation(s) For Gaussian processes, analytical results exist for the determination of the MPM values (e.g. MPM wave height is 1,86 times the significant wave height). For general non-linear, non-Gaussian, finite band-width processes, approximate methods are used to generate the probability density function of the process. The method proposed by Winterstein (1988)[203] fits a Hermite polynomial of Gaussian processes to transform the non-linear, non-Gaussian process into a mathematically tractable probability density function. This has been further refined by Jensen (1991)[112] for processes with large kurtosis. This procedure requires a suitable length time domain simulation for each quantity of interest. The input sea state simulation should be checked for Gaussianity. Guidance is given in Table A.7.3-3. The calculation procedure to determine the maximum of a time series, R(t), with a simulation duration Tsim for a three-hour exposure, T3h, is as follows.  Step 1: Calculate the mean, μ, the standard deviation, σ, and the following quantities of the time series for the parameter under consideration as given in Formulae (C.2.3-1) and (C.2.3-2): α3 = (1/n)Σ[(R − μ)3]/σ3 (C.2.3-1) α4 = (1/n)Σ[(R − μ)4]/σ4 (C.2.3-2) where α3 is the skewness; α4 is the kurtosis. When the kurtosis is less than 3,0, the approach given here is not valid and the alternative given in Winterstein (1988)[203] should be used.  Step 2: Construct a standardized response process, z = (R − μ)/σ. Using this standardized process, calculate the number of zero-upcrossings, N. In lieu of an actual cycle count from the simulated time series, N = 1 000 may be assumed for a three-hour simulation.  Step 3: Compute the following quantities from the characteristics of the time series for the response of interest as given in Formulae (C.2.3-3) to (C.2.3-5): ()334421153,hαα=++− (C.2.3-3) {}441153118,()hα=+−− (C.2.3-4) ()122234126Khh−=++ (C.2.3-5) . No further reproduction or distribution permitted. Printed / viewed by: 289 It is necessary to seek a more accurate result by determining a solution for C1, C2 and C3 from Formulae (C.2.3-6) to (C.2.3-8): σ 2 = C12 + 6C1C3 + 2C22 + 15C32 (C.2.3-6) σ 3α 3 = C2(6C12 + 8C22 + 72C1C3 + 270C32) (C.2.3-7) σ 4α 4 = 60C24 + 3C14 + 10 395C34 + 60C12C22 + 4 500C22C32 + 630C12C32 + ... ... + 936C1C22C3 + 3 780C1C33 + 60C13C3 (C.2.3-8) using as initial guesses the values given in Formulae (C.2.3-9) to (C.2.3-11): C1 = σ K(1 − 3h4) (C.2.3-9) C2 = σ Kh3 (C.2.3-10) C3 = σ Kh4 (C.2.3-11) where σ is obtained from Step 1; K, h3 and h4 are obtained from Formulae (C.2.3-3) to (C.2.3-4). Following the solution for C1, C2 and C3, the values for K, h3 and h4 are recomputed as given in Formulae (C.2.3-12) to (C.2.3-14): K = (C1 + 3C3)/σ (C.2.3-12) h3 = C2/(σK) (C.2.3-13) h4 = C3/(σK) (C.2.3-14)  Step 4: The most probable value, U, of the transformed process is computed as given in Formula (C.2.3-15): 3hsim2lnTUNT=⋅ (C.2.3-15) where U is a Gaussian process of zero mean, unit variance; T3h is three hours; Tsim is the simulation duration, expressed in hours. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 290 © ISO 2023 – All right reserved  Step 5: The most probable maximum, transformed back to the standardized variable, z, is then as given in Formula (C.2.3-16): zMPM = K [U + h3(U 2 − 1) + h4(U3 − 3U)] (C.2.3-16)  Step 6: Finally, the MPME in the required three hour exposure period for the response under consideration, can be computed from Formula (C.2.3-17): RMPME = μ + σ zMPM (C.2.3-17) C.2.4 Guidance on the fourth method of Table A.10.5-1: Application of drag-inertia method to determine the base shear and overturning moment DAF from time domain simulation The method, based on Shell International Petroleum, SIPM EPD/51/52 (1991)[167], may be used to determine KDAF,RANDOM used to compute the inertial loadset for a two-stage deterministic storm analysis (see 10.5.2). The method combines two components of the total dynamic response, namely the static and inertial parts. The inertial part is computed as the difference between the total dynamic and static responses and should not be confused with the response to inertial wave loading. The method requires a determination of the response of the jack-up for four conditions. In all four cases, the storm simulation (random seed) should be identical, but with different components of the loading and/or response simulated. The responses considered are usually total wave and current base shear and total wave and current overturning moment, for computing the base shear and overturning moment DAFs, respectively. The four cases being simulated are full dynamic response, full static response, static response to inertia only wave loading (setting CD = 0) and static response to drag only loading (setting Cm = 0). From these the inertial response is obtained as the full dynamic response minus the full static response. The means and standard deviations of the response are extracted from the time domain responses and the DAFs computed as illustrated in Figure C.2.4-1. The drag-inertia method given here includes a final step to scale the DAF based on the period ratio Tn/Tp. This step is included to ensure that the DAF values are not underestimated for cases where Tn approaches Tp; see Perry and Mobbs (2011)[147]. The formula for the scaling factor is shown in Figure C.2.4-1 and is illustrated graphically in Figure C.2.4-2. This method should not be used to compute MPME values for use in a one-stage stochastic analysis. It should be used only in a two-stage analysis when the foundation is modelled as either pinned or based on linearized stiffness in the DAF calculation. Further details on the background to, and limitations of, this method can be found in ISO/TR 19905-2. . No further reproduction or distribution permitted. Printed / viewed by: 291 Figure C.2.4-1 — The drag-inertia method including DAF scaling factor . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 292 © ISO 2023 – All right reserved Figure C.2.4-2 — Graphical representation of DAF scaling factor, FDAF, applied in the drag-inertia method . No further reproduction or distribution permitted. Printed / viewed by: 293 Annex D (informative) Foundations — Recommendations for the acquisition of site-specific geotechnical data This annex, based on a report by RPS Energy in the InSafeJIP (2010)[158] provides recommendations for the acquisition of site-specific geotechnical data for jack-up foundation assessment purposes. It is assumed that regional geological information is available, a geological desk study has been conducted and that a site geophysical survey (see ISO 19901-10) has been performed in advance of the offshore geotechnical works as this information is required in order to plan and optimize the geotechnical site investigation work-scope (see ISO 19901-8). Regional geohazards, if present, are unlikely to be identified using the site-specific geotechnical data in isolation, which should be integrated with the local geophysical survey, regional geological data and any other information that can be useful in assessing the potential presence of regional geohazards. The primary objective of the geotechnical works is to acquire adequate data in order to minimize the seabed risk and allow for risk avoidance or mitigation should it be necessary. The geotechnical risks associated with jack-up operations are listed elsewhere; see Table A.6.5-1. Ideally during a field development planning stage, adequate consideration should be given to the acquisition and integration of geophysical and geotechnical data prior to the installation of any facilities. If jack-ups are used for work-over or as installation support facilities throughout the field life, then it is necessary to give due consideration to the positioning of these units and the implication of the seabed depressions and zones of disturbed soil (footprints) caused during spudcan installation on other operations. The range of jack-up designs suitable for operating within the field should be considered and the implications of each on each other's operation, in terms of spudcan-footprint interaction, should be assessed. Although there can be exceptions, it is generally necessary to acquire geotechnical data to a depth below sea floor of either 30 m, or the anticipated spudcan penetration depth plus 1,5 spudcan diameters, whichever is the greater. It is also recognized that conducting an optimally designed offshore work-scope is not always possible so that a compromise solution is necessary. Such factors include:  availability of dedicated geotechnical site investigation vessel with experienced personnel;  availability of specific geotechnical systems and tools;  weather conditions precluding or reducing offshore operations;  site accessibility. Tables D.1 to D.3 list various site conditions and provide recommendations for offshore geotechnical site investigation works that can be required to conduct a jack-up foundation site-specific assessment for both “open” and “work-over” sites. “Open sites” refer to sites where no jack-up has previously operated, whereas “work-over” sites are sites at which jack-ups have previously been installed. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 294 © ISO 2023 – All right reserved At work-over sites, the ground is likely to have been disturbed and craters, or “footprints”, left at the seabed at previously installed spudcan locations. These operations are likely to have modified the soil properties and such ground modification should be considered during the scoping of the geotechnical site investigation for the assessment of future jack-up installation operations. Spudcan-footprint interaction issues are not covered in this annex. Tables D.1 to D.3 provide guidance on the number and positioning of geotechnical boreholes (purely sampling or combined or “composite” sampling and down-hole testing) and continuous piezocone penetration tests for a range of circumstances. Refer to A.6.5 and RPS Energy (2010)[158] for further comment on soil sampling and cone penetration test data acquisition. Soil laboratory testing requirements and specifications are discussed elsewhere, A.6.5 and RPS Energy (2010)[158]. These recommendations are for guidance and do not imply any legislative requirements, responsibilities or guarantee of applicability. Table D.1 — Geotechnical work scope for open sites for simple geological conditions Programme type Geological setting Site conditions Minimum suggested site investigation work scopea Illustrated views 1S Simple Regional, local geology and near surface conditions reasonably well understood. Site conditions suitable for jack-up rig (JU) operations. High-quality geophysical data available and sub-bottom profiling data tied-back to a geotechnical borehole(s) and/or local JU installation sites. Mature JU operating province where foundation issues are not expected and with laterally continuous ground conditions. Desk top study corroborates geophysical data. Adverse foundation performance risk extremely remote and any potential risk is expected to be manageable Acquisition of site-specific geotechnical data may not be necessary.a not applicable 2S Simple As 1S above but with a layer of soft sediments over a hard layer of known geology, where it is expected that the spudcans are founded on the hard interface beneath the soft sediments. Formation present below the soft/hard interface known to be competent and able to safely support spudcans. The ground conditions are known to be laterally continuous and the interface between soft to harder sediments does not undulate adversely. Seabed piezocone tests or gravity cores may be used to confirm the absence of potentially adverse layering within the soft upper sediments and to tag the hard layer. If data proves the soil conditions are not as expected, then deeper piezocone tests and/or soil boring(s) may be required to investigate and confirm the soil conditions and identify any variability. If potentially adverse conditions for JU foundations are present, consider increasing the geotechnical investigation scope of work.a or combinations of both across the area; be aware that this is example layout only . No further reproduction or distribution permitted. Printed / viewed by: 295 Programme type Geological setting Site conditions Minimum suggested site investigation work scopea Illustrated views 3S Simple Regional, local geology and near surface conditions reasonably well understood and suitable for JU operations. High-quality geophysical data available and sub-bottom profiling data tied back to a geotechnical borehole/s and/or local JU installation sites. Soils expected to be laterally continuous. Desk top study corroborates geophysical data. Knowledge of regionally successful JU performance and local geotechnical borehole data available. Unlikely adverse foundation performance risk Continuous sampling borehole or continuous seabed piezocone test from 0 to TD placed in the centre of the JU footprint or at one spudcan location. Composite borehole may be acceptable if ground conditions are simple and well defined, and proved to be as expected. Data gaps are kept to a minimum (target gaps at < 0,2 m). If data gaps > 0,2 m, or there are concerns regarding the suitability of the ground for jack-up operations, then consider additional adjacent borehole(s) with downhole piezocone tests (as opposed to seabed piezocone tests if unable to reach TD), or sampling intervals conducted over data gaps of the previously conducted borehole. If concerns remain regarding the suitability of ground conditions for the JU operations, then perform additional geotechnical site investigation. 4S Simple Regional and local geology reasonably well understood and near surface conditions expected to be continuous and suitable for JU operations. High-quality geophysical survey data available without sub-bottom profiler data tie lines. Desk top study correlates with geophysical data. No local geotechnical data or knowledge of successful JU performance regionally. Foundation performance risk considered unlikely One continuous sample borehole and an adjacent piezocone test from 0 to TD within the JU footprint, or combination of composite and/or continuous sampling and piezocone test boreholes at spudcan centres, so that sufficient data are available to define the ground model. If data illustrate soil conditions suitable for JU operations and the geophysics confirms stratigraphic continuity across the site, then no further geotechnical investigation is required. If variations occur, additional data acquisition should be considered. Key gravity piston corer shallow seabed piezocone test composite borehole (downhole piezocone tests and sampling) continuous sampling borehole continuous piezocone test NOTE 1 If appropriate, the jack-up geotechnical SI can be conducted in consultation with the field development teams in order to optimize data acquisition. NOTE 2 Target depth (TD) is the greater of either 30 m or 1,5 times the spudcan diameters beneath the calculated spudcan tip penetration depth at the maximum preload. NOTE 3 At minimum, the ground model is generated to TD, with adequate data acquired for reliable definition of the model. a The requirement for and specification of the geotechnical site investigation work scope should always be defined by a competent geotechnical engineer(s), and discussed and agreed by the operator and, when possible, the jack-up owner. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 296 © ISO 2023 – All right reserved Table D.2 — Geotechnical work scope for open sites for complex/very complex geological conditions Programme type Geological setting Site conditions Minimum suggested site investigation work scopea Illustrated views 1C Complex Regional and local geology reasonably understood without specific details of near-surface ground conditions. Desk top study and geophysical survey data ambiguous and suggests that near-surface ground conditions are likely to be variable across the site and potential for foundation performance risk recognised. No knowledge of successful JU performance locally available and potential for adverse foundation performance is recognized. One continuous sampling borehole and one adjacent continuous piezocone test at one spudcan location and piezocone tests from 0 to TD at each of the other two spudcan locations, or continuous piezocone tests at one spudcan location with continuous sampling boreholes at the others from 0 to TDa 1VC Very complex Regional and local geological data available without specific details of near -surface ground conditions at the site. The desk top study and geophysical survey data suggest near-surface ground conditions are variable across the site. The potential for JU foundation performance risk is identified perhaps with knowledge of adverse JU foundation performance locally. Continuous sampling and adjacent piezocone tests at all spudcan locations from 0 to TD. Or as above with centrally located continuous sampling and/or piezocone test borehole to TDa Key continuous sampling borehole continuous piezocone test NOTE 1 If appropriate, the jack-up geotechnical SI can be conducted in consultation with the field development teams in order to optimize data acquisition. NOTE 2 Target depth (TD) is the greater of either 30 m or 1,5 times the spudcan diameters beneath the calculated spudcan tip penetration depth at the maximum preload. NOTE 3 At minimum, the ground model is generated to TD, with adequate data acquired for reliable definition of the model. a The requirement for and specification of the geotechnical site investigation work scope should always be defined by a competent geotechnical engineer(s), and discussed and agreed by the operator and, when possible, the jack-up owner. . No further reproduction or distribution permitted. Printed / viewed by: 297 Table D.3 — Geotechnical work scope for work-over sites for simple to very complex geological settings Programme type Geological setting Site conditions Minimum suggested site investigation work scopea,b Illustrated views 1S-WO Simple First JU operation at the site, no existing spudcan footprints to consider. High-quality geophysical survey available with recent seabed clearance survey. Appropriate geotechnical and geophysical data acquired for fixed platform and JU installation purposes confirms suitable conditions for JU installation. Local JU operations without foundation hazards. Acquisition of additional geotechnical data may not be necessarya,b not applicable 2S-WO Simple Repeat visit with identical JU footprint and spudcan size. Identical spudcan positions - footprint interaction issues unlikely. No previous foundation issues and previous jack-up operations not able to adversely alter the ground conditions with identical jack-up emplacement Acquisition of additional geotechnical data may not be necessarya,b not applicable 3S-WO Simple Repeat visit with identical JU. New spudcan positions with possible spudcan-foot print issues. Known ground conditions. No previous foundation issues Survey of existing footprints advisable with seabed clearance survey. Consideration of spudcan-footprint interaction mitigation. Additional geotechnical data can be requireda,b — 4S-WO Simple First visit of JU to this platform where units have previously operated at the site. Known ground conditions. No previous foundation issues. It is necessary to consider spudcan-footprint interaction issues. Consideration of spudcan-footprint interaction mitigation. Survey of existing footprints advisable with seabed clearance survey. Additional geotechnical data can be required.a,b — 1C-WO Complex First visit of JU to a platform where units have not previously operated with the knowledge of local jack-up foundation performance. New unit with spudcan bearing pressures and/or spudcan diameters different than those units previously operated at the site. Check adequacy of existing geotechnical data – additional site investigation can be required. It is necessary to consider spudcan - footprint interaction issues. Survey of existing footprints advisable with seabed clearance survey. Consideration of spudcan-footprint interaction mitigation. Additional geotechnical data can be required.a The previous JU operations can have modified the ground conditions where the intended spudcan installation position is being placed and this can require investigation.a,b — . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 298 © ISO 2023 – All right reserved Programme type Geological setting Site conditions Minimum suggested site investigation work scopea,b Illustrated views 1VC-WO Complex First visit of JU to this platform where units have previously operated at the site but on a different side of jacket. Previous foundation issues or no knowledge of successful JU performance locally available and potential for foundation performance recognised. Regional and local geology reasonably understood without specific details of near-surface ground conditions. At sites where the desk top study and geophysical survey data suggest near-surface ground conditions are variable across the site or risk identified and knowledge of adverse JU foundation performance locally, high potential for foundation performance risk identified. New unit with spudcan bearing pressures and/or spudcan diameters different than those units previously operated at the site It is necessary to consider spudcan - footprint interaction issues as well as potential degradation of lateral capacity of jacket piles. Continuous piezocone tests from 0 to TD at each spudcan location with one continuous sampling borehole centrally located or at a spudcan location adjacent to a piezocone test, or suitable combination of continuous sampling and piezocone tests to determine the ground model.a,b or similar combinations of continuous sampling and piezocone tests to TD, increase or decrease work scope depending upon local geological variationa,b Key composite borehole (downhole piezocone tests and sampling) continuous sampling borehole continuous piezocone test NOTE 1 If appropriate, the jack-up geotechnical SI can be conducted in consultation with the field development teams in order to optimize data acquisition. NOTE 2 Target depth (TD) is the greater of either 30 m or 1,5 times the spudcan diameters beneath the calculated spudcan tip penetration depth at the maximum preload. NOTE 3 At minimum, the ground model is generated to TD, with adequate data acquired for reliable definition of the model. a The requirement for and specification of the geotechnical site investigation work scope should always be defined by a competent geotechnical engineer(s), and discussed and agreed by the operator and, when possible, the jack-up owner. b The requirement for additional geotechnical site investigation data should consider the existing soil data previously acquired for the design of the adjacent infrastructure. . No further reproduction or distribution permitted. Printed / viewed by: 299 Annex E (informative) Foundations — Additional information and alternative approaches CAUTION — The guidance in E.5 should not be used because inconsistencies have been identified. The Clause will be corrected in an Amendment. E.1 Guidance on A.9.3.2.2: Penetration in clays — Bearing capacity factors of Houlsby and Martin Presented below is the theoretical solution for the bearing capacity of circular conical foundations on weightless clays of uniform and increasing strength with depth as provided by Houlsby and Martin (2003)[99]. In Tables E.1-1 through to E.1-5, the bearing capacity factors are defined for  cone angles β of 60°, 90°, 120°, 150° and a flat plate of 180°,  normalized embedment depth (Dembed/B) of 0,0; 0,1; 0,25; 0,5; 1,0 and 2,5,  values of shear strength gradient ρsuB/sum between 0 and 5 where ρsu is the rate of increase in undrained shear strength with depth, from a value of sum at the sea floor, and  roughness between smooth (a = 0) and fully rough (a = 1). Roughness is defined as a = au/su where au is the maximum shear stress that can be mobilized at the cone surface and su is the local value. Intervals of 0,2 are provided. Definition of these parameters is provided in Figure E.1-1. Tables E.1-1 through E.1-5 provide a theoretical lower bound to the bearing factor Nc·sc·dc to apply to the shear strength at the spudcan base level, suo, for the full range of the above parameters, provided that Dembed is not greater than Hcav as defined in A.9.3.2.1.4. The bearing factor is nonlinear with respect to the non-dimensional soil strength gradient, embedment ratio and roughness factor. It is necessary to use caution when estimating appropriate bearing factors for non-dimensional soil strength gradients, embedment ratios and roughness factors other than those in the tables below. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 300 © ISO 2023 – All right reserved Key 1 undrained shear strength profile 2 footing base level 3 footing/soil interface with adhesion (au) and roughness factor, ar B effective spudcan diameter at uppermost part of bearing area Dembed greatest embedment depth of maximum cross-sectional spudcan bearing area QV gross bearing capacity at depth, Dembed sum undrained shear strength at sea floor suo undrained shear strength at footing base level: suo = sum + ρDembed au maximum shear stress that can be mobilized at the cone surface (adhesion) ar roughness factor: ar = au/su β spudcan cone angle ρsu rate of increase in undrained shear strength with depth NOTE Based on Tresca Yield Criterion for φ = 0 and γ'' = 0. Figure E.1-1 — Conical spudcan bearing capacity — Problem definition and notation . No further reproduction or distribution permitted. Printed / viewed by: 301 Table E.1-1 — Values of Nc.sc.dc = [(QV/A) − p′o]/suo for cone angle β = 60° ρB/sum Dembed/B Roughness factor ar = au/su 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,0 4,45 4,96 5,45 5,90 6,32 6,69 0,0 0,1 4,68 5,19 5,67 6,12 6,53 6,90 0,0 0,25 4,98 5,50 5,96 6,40 6,81 7,18 0,0 0,5 5,41 5,90 6,37 6,81 7,21 7,57 0,0 1,0 6,07 6,55 7,01 7,43 7,84 8,18 0,0 2,5 7,33 7,81 8,25 8,66 9,05 9,39 1,0 0,0 5,81 6,51 7,15 7,77 8,34 8,87 1,0 0,1 5,92 6,59 7,23 7,83 8,38 8,89 1,0 0,25 6,04 6,70 7,30 7,88 8,42 8,91 1,0 0,5 6,20 6,84 7,41 7,96 8,47 8,94 1,0 1,0 6,43 7,05 7,58 8,12 8,59 9,03 1,0 2,5 6,97 7,55 8,08 8,54 8,98 9,39 2,0 0,0 7,14 8,02 8,84 9,60 10,32 10,99 2,0 0,1 6,92 7,73 8,49 9,21 9,88 10,50 2,0 0,25 6,74 7,50 8,18 8,84 9,46 10,03 2,0 0,5 6,59 7,29 7,91 8,53 9,09 9,61 2,0 1,0 6,55 7,20 7,76 8,33 8,83 9,30 2,0 2,5 6,99 7,49 8,03 8,50 8,95 9,37 3,0 0,0 8,49 9,54 10,50 11,42 12,29 13,10 3,0 0,1 7,77 8,70 9,56 10,38 11,14 11,85 3,0 0,25 7,24 8,03 8,80 9,53 10,20 10,82 3,0 0,5 6,82 7,56 8,21 8,86 9,45 10,00 3,0 1,0 6,60 7,27 7,85 8,44 8,94 9,43 3,0 2,5 6,99 7,47 8,01 8,49 8,94 9,36 4,0 0,0 9,83 11,02 12,16 13,24 14,26 15,18 4,0 0,1 8,51 9,52 10,48 11,38 12,22 13,00 4,0 0,25 7,61 8,44 9,26 10,04 10,75 11,41 4,0 0,5 6,97 7,74 8,41 9,08 9,69 10,26 4,0 1,0 6,64 7,31 7,90 8,49 9,01 9,51 4,0 2,5 6,86 7,45 8,00 8,48 8,94 9,35 5,0 0,0 11,17 12,52 13,83 15,06 16,20 17,26 5,0 0,1 9,14 10,23 11,26 12,25 13,15 13,99 5,0 0,25 7,90 8,78 9,63 10,43 11,17 11,87 5,0 0,5 7,08 7,84 8,55 9,24 9,86 10,45 5,0 1,0 6,66 7,32 7,94 8,53 9,06 9,56 5,0 2,5 6,85 7,44 7,99 8,47 8,93 9,35 . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 302 © ISO 2023 – All right reserved Table E.1-2 — Nc.sc.dc = [(QV/A) − p′o]/suo for cone angle β= 90° ρB/sum Dembed/B Roughness factor ar = au/su 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,0 4,64 5,02 5,36 5,67 5,95 6,17 0,0 0,1 4,90 5,28 5,61 5,91 6,18 6,41 0,0 0,25 5,22 5,59 5,93 6,23 6,49 6,71 0,0 0,5 5,68 6,03 6,36 6,66 6,92 7,14 0,0 1,0 6,37 6,71 7,05 7,32 7,58 7,79 0,0 2,5 7,65 8,03 8,32 8,60 8,86 9,05 1,0 0,0 5,57 6,05 6,47 6,87 7,22 7,53 1,0 0,1 5,74 6,21 6,62 7,00 7,36 7,65 1,0 0,25 5,94 6,38 6,79 7,16 7,50 7,79 1,0 0,5 6,16 6,61 6,99 7,36 7,68 7,97 1,0 1,0 6,50 6,93 7,30 7,64 7,95 8,21 1,0 2,5 7,25 7,57 7,94 8,25 8,53 8,78 2,0 0,0 6,46 7,03 7,54 8,01 8,45 8,82 2,0 0,1 6,41 6,94 7,43 7,88 8,28 8,65 2,0 0,25 6,41 6,88 7,35 7,76 8,14 8,46 2,0 0,5 6,40 6,88 7,29 7,69 8,03 8,35 2,0 1,0 6,54 6,99 7,37 7,73 8,06 8,33 2,0 2,5 7,16 7,49 7,86 8,18 8,47 8,72 3,0 0,0 7,36 8,00 8,59 9,14 9,65 10,08 3,0 0,1 6,99 7,57 8,10 8,60 9,05 9,45 3,0 0,25 6,70 7,24 7,73 8,17 8,59 8,94 3,0 0,5 6,54 7,04 7,47 7,88 8,24 8,57 3,0 1,0 6,56 7,02 7,41 7,78 8,11 8,39 3,0 2,5 7,12 7,46 7,83 8,15 8,44 8,46 4,0 0,0 8,22 8,96 9,64 10,25 10,82 11,33 4,0 0,1 7,49 8,11 8,68 9,22 9,70 10,14 4,0 0,25 6,94 7,50 8,01 8,48 8,92 9,29 4,0 0,5 6,63 7,15 7,58 8,01 8,38 8,72 4,0 1,0 6,57 7,03 7,43 7,80 8,14 8,42 4,0 2,5 7,05 7,44 7,81 8,13 8,42 8,67 5,0 0,0 9,11 9,93 10,66 11,35 12,00 12,56 5,0 0,1 7,87 8,55 9,17 9,74 10,26 10,75 5,0 0,25 7,12 7,71 8,24 8,72 9,17 9,57 5,0 0,5 6,70 7,22 7,67 8,09 8,47 8,82 5,0 1,0 6,57 7,04 7,44 7,82 8,16 8,44 5,0 2,5 7,03 7,42 7,80 8,12 8,41 8,66 . 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Printed / viewed by: 303 Table E.1-3 — Nc.sc.dc = [(QV/A) − p′o]/suo for cone angle β= 120° ρB/sum Dembed/B Roughness factor ar = au/su 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,0 4,96 5,25 5,51 5,73 5,92 6,05 0,0 0,1 5,23 5,52 5,77 5,99 6,17 6,30 0,0 0,25 5,57 5,85 6,10 6,31 6,49 6,62 0,0 0,5 6,04 6,31 6,55 6,76 6,93 7,05 0,0 1,0 6,74 7,01 7,24 7,44 7,61 7,72 0,0 2,5 8,07 8,32 8,55 8,75 8,90 8,99 1,0 0,0 5,69 6,04 6,36 6,65 6,89 7,09 1,0 0,1 5,89 6,24 6,55 6,82 7,07 7,26 1,0 0,25 6,12 6,45 6,76 7,02 7,26 7,45 1,0 0,5 6,39 6,72 7,01 7,27 7,48 7,66 1,0 1,0 6,80 7,10 7,37 7,61 7,82 7,97 1,0 2,5 7,52 7,82 8,08 8,29 8,49 8,61 2,0 0,0 6,38 6,79 7,16 7,50 7,80 8,04 2,0 0,1 6,41 6,80 7,16 7,47 7,75 7,97 2,0 0,25 6,46 6,83 7,17 7,46 7,72 7,94 2,0 0,5 6,56 6,91 7,22 7,49 7,74 7,92 2,0 1,0 6,80 7,12 7,40 7,65 7,87 8,03 2,0 2,5 7,43 7,72 7,99 8,21 8,41 8,53 3,0 0,0 7,04 7,51 7,93 8,31 8,66 8,93 3,0 0,1 6,84 7,27 7,65 8,00 8,31 8,57 3,0 0,25 6,71 7,09 7,45 7,76 8,05 8,27 3,0 0,5 6,66 7,02 7,34 7,63 7,88 8,08 3,0 1,0 6,81 7,11 7,41 7,67 7,89 8,06 3,0 2,5 7,38 7,68 7,95 8,17 8,38 8,51 4,0 0,0 7,70 8,22 8,69 9,11 9,49 9,81 4,0 0,1 7,20 7,66 8,07 8,44 8,77 9,03 4,0 0,25 6,88 7,28 7,65 7,98 8,27 8,53 4,0 0,5 6,72 7,08 7,42 7,71 7,97 8,18 4,0 1,0 6,80 7,12 7,41 7,68 7,90 8,08 4,0 2,5 7,39 7,66 7,93 8,15 8,36 8,49 5,0 0,0 8,35 8,91 9,43 9,89 10,31 10,67 5,0 0,1 7,52 7,99 8,43 8,82 9,18 9,95 5,0 0,25 7,01 7,43 7,81 8,15 8,45 8,72 5,0 0,5 6,77 7,13 7,47 7,77 8,03 8,25 5,0 1,0 6,80 7,12 7,42 7,69 7,91 8,09 5,0 2,5 7,34 7,64 7,91 8,14 8,34 8,48 . 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Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 304 © ISO 2023 – All right reserved Table E.1-4 — Nc.sc.dc = [(QV/A) − p′o]/suo for cone angle β= 150° ρB/sum Dembed/B Roughness factor ar = au/su 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,0 5,32 5,55 5,74 5,89 6,01 6,05 0,0 0,1 5,60 5,82 6,00 6,16 6,26 6,30 0,0 0,25 5,94 6,16 6,34 6,49 6,59 6,61 0,0 0,5 6,41 6,62 6,80 6,94 7,03 7,05 0,0 1,0 7,13 7,32 7,49 7,62 7,71 7,72 0,0 2,5 8,46 8,65 8,81 8,93 8,99 8,99 1,0 0,0 5,94 6,22 6,46 6,67 6,84 6,97 1,0 0,1 6,16 6,43 6,67 6,87 7,04 7,15 1,0 0,25 6,41 6,67 6,90 7,09 7,25 7,36 1,0 0,5 6,71 6,96 7,18 7,36 7,51 7,60 1,0 1,0 7,13 7,36 7,57 7,73 7,86 7,95 1,0 2,5 7,91 8,12 8,31 8,44 8,56 8,61 2,0 0,0 6,50 6,82 7,11 7,35 7,57 7,73 2,0 0,1 6,59 6,90 7,16 7,40 7,59 7,74 2,0 0,25 6,69 6,98 7,23 7,45 7,63 7,76 2,0 0,5 6,84 7,10 7,34 7,54 7,70 7,82 2,0 1,0 7,11 7,35 7,57 7,74 7,89 7,99 2,0 2,5 7,81 8,01 8,21 8,35 8,47 8,53 3,0 0,0 7,03 7,40 7,72 7,98 8,24 8,43 3,0 0,1 6,94 7,27 7,56 7,81 8,03 8,21 3,0 0,25 6,88 7,18 7,45 7,68 7,88 8,03 3,0 0,5 6,91 7,18 7,43 7,63 7,81 7,94 3,0 1,0 7,10 7,35 7,57 7,75 7,90 8,00 3,0 2,5 7,76 7,97 8,16 8,31 8,43 8,49 4,0 0,0 7,55 7,94 8,30 8,58 8,88 9,10 4,0 0,1 7,23 7,58 7,89 8,16 8,40 8,59 4,0 0,25 7,02 7,34 7,62 7,86 8,07 8,23 4,0 0,5 6,95 7,23 7,49 7,70 7,88 8,01 4,0 1,0 7,09 7,34 7,56 7,75 7,90 8,00 4,0 2,5 7,72 7,94 8,13 8,29 8,41 8,47 5,0 0,0 8,05 8,48 8,86 9,19 9,48 9,74 5,0 0,1 7,46 7,83 8,16 8,44 8,69 8,90 5,0 0,25 7,13 7,45 7,74 7,99 8,20 8,37 5,0 0,5 6,99 7,27 7,53 7,74 7,93 8,07 5,0 1,0 7,09 7,34 7,56 7,75 7,91 8,01 5,0 2,5 7,70 7,93 8,12 8,27 8,40 8,46 . 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Printed / viewed by: 305 Table E.1-5 — Nc.sc.dc = [(QV/A) − p′o]/suo for cone angle β= 180° ρB/sum Dembed/B Roughness factor ar = au /su 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,0 5,69 5,86 5,97 6,03 6,05 6,05 0,0 0,1 5,97 6,13 6,24 6,29 6,30 6,30 0,0 0,25 6,31 6,47 6,57 6,61 6,61 6,61 0,0 0,5 6,79 6,93 7,02 7,05 7,05 7,05 0,0 1,0 7,49 7,63 7,70 7,71 7,71 7,71 0,0 2,5 8,82 8,94 8,99 8,99 8,99 8,99 1,0 0,0 6,25 6,47 6,65 6,79 6,90 6,95 1,0 0,1 6,48 6,69 6,87 7,00 7,10 7,14 1,0 0,25 6,74 6,94 7,11 7,23 7,32 7,35 1,0 0,5 7,05 7,24 7,39 7,51 7,58 7,60 1,0 1,0 7,47 7,64 7,79 7,88 7,93 7,94 1,0 2,5 8,26 8,32 8,52 8,60 8,61 8,61 2,0 0,0 6,73 6,98 7,20 7,39 7,53 7,63 2,0 0,1 6,85 7,08 7,30 7,46 7,59 7,68 2,0 0,25 6,98 7,20 7,39 7,55 7,66 7,72 2,0 0,5 7,15 7,36 7,53 7,67 7,76 7,80 2,0 1,0 7,45 7,63 7,78 7,90 7,96 7,98 2,0 2,5 8,16 8,27 8,43 8,50 8,53 8,53 3,0 0,0 7,16 7,45 7,69 7,91 8,08 8,21 3,0 0,1 7,13 7,40 7,62 7,81 7,96 8,07 3,0 0,25 7,15 7,37 7,58 7,75 7,88 7,96 3,0 0,5 7,21 7,42 7,61 7,75 7,86 7,91 3,0 1,0 7,43 7,62 7,78 7,90 7,97 7,99 3,0 2,5 8,13 8,23 8,38 8,46 8,49 8,49 4,0 0,0 7,56 7,87 8,15 8,38 8,58 8,73 4,0 0,1 7,38 7,64 7,89 8,09 8,26 8,39 4,0 0,25 7,26 7,50 7,71 7,89 8,03 8,13 4,0 0,5 7,25 7,46 7,65 7,80 7,92 7,98 4,0 1,0 7,44 7,61 7,77 7,89 7,97 8,00 4,0 2,5 8,09 8,19 8,36 8,44 8,47 8,47 5,0 0,0 7,94 8,27 8,57 8,83 9,05 9,23 5,0 0,1 7,56 7,85 8,10 8,32 8,50 8,64 5,0 0,25 7,34 7,59 7,81 8,00 8,15 8,25 5,0 0,5 7,27 7,49 7,68 7,84 7,96 8,02 5,0 1,0 7,43 7,60 7,77 7,89 7,97 8,00 5,0 2,5 8,07 8,18 8,35 8,43 8,46 8,46 . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 306 © ISO 2023 – All right reserved E.2 Guidance on A.9.3.2.4 — Penetration in silica sands Theoretical values of Nγ calculated by Cassidy and Houlsby (2002)[42] using the slip-line method for circular footings with a conical underside are given in Tables E.2-1 to E.2-5 (see also Figure E.2-1). These values cover cone apex angles from 60° to 180°, spudcan-soil interface roughness coefficients (α = tanδ/tanφ′) from 0,6 to 1, and soil friction angles from 20° to 40°. It is noted that the Nγ values are non-linear with φ′ and this should be accounted for in any interpolation of Tables E.2-1 to E.2-5. The soil–steel interface friction angle, δ, is typically in the range 22° to 29°, decreasing with increasing grain size API (2007)[18]. This implies that the roughness coefficient, α, is at least 0,6 for typical soil friction angles (φ′ = 30° ± 5°). Be aware that the Nγ values given in Table A.9.3-3 for the special case of a flat, rough circular footing (i.e. a 180° cone with α = 1) were calculated using a different implementation of the slip-line method, Martin (2003)[133]. Key 1 homogeneous soil with friction angle, φ’ 2 spudcan-soil interface, with roughness coefficient α B/2 effective spudcan radius β spudcan cone apex angle VL available spudcan reaction; see Formula (A.9.3-1) Figure E.2-1 — Definition of parameters for Tables E.2-1 to E.2-5 Table E.2-1 — Bearing capacity factors (Nγ) for a conical apex angle of 60° β = 60° φ ′ (°) α = 1 α = 0,8 α= 0,6 20 7,33 6,55 5,64 25 14,69 12,99 10,94 30 31,99 27,45 22,50 35 79,26 62,95 48,81 40 209,20 163,20 122,30 Table E.2-2 — Bearing capacity factors (Nγ) for a conical apex angle of 90° β = 90° φ ′ (°) α = 1 α = 0,8 α= 0,6 20 4,54 4,11 3,62 25 9,58 8,50 7,26 30 21,12 18,87 15,58 35 51,76 47,42 37,01 40 142,80 132,60 99,18 . No further reproduction or distribution permitted. Printed / viewed by: 307 Table E.2-3 — Bearing capacity factors (Nγ) for a conical apex angle of 120° β= 120° φ ′ (°) α = 1 α = 0,8 α= 0,6 20 3,37 3,15 2,81 25 7,46 6,99 6,05 30 17,58 16,80 14,30 35 44,73 42,99 35,79 40 129,40 124,90 103,30 Table E.2-4 — Bearing capacity factors (Nγ) for a conical apex angle of 150° β = 150° φ ′ (°) α = 1 α = 0,8 α= 0,6 20 2,72 2,61 2,39 25 6,44 6,13 5,60 30 15,93 15,13 14,02 35 42,36 40,42 36,41 40 128,10 120,50 110,50 Table E.2-5 — Bearing capacity factors (Nγ) for a conical apex angle of 180° β = 180° φ ′ (°) α = 1 α = 0,8 α= 0,6 20 2,16 2,04 1,99 25 5,27 5,37 5,14 30 14,13 13,91 12,98 35 42,56 40,93 36,81 40 129,40 121,50 117,00 The bearing capacity calculated using Formula (A.9.3-8) is strongly dependent on the adopted soil friction angle, φ ′. The apparent friction angle mobilized during spudcan penetration in sand is influenced by: a) the soil relative density (and therefore the dilatancy): peak friction angle increases with relative density; b) the size of the spudcan, and, therefore, the stress level within the failing soil: peak friction angle decreases as the stress level increases; c) progressive failure: soil elements at different locations within the failure mechanism have undergone widely differing levels of shear strain; d) progressive failure due to pre-shearing of the soil by the conical spudcan tip, which acts to reduce the mobilized peak strength; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 308 © ISO 2023 – All right reserved e) compression of the foundation soil, which generates additional settlement; f) the level of drainage (i.e. excess pore pressure development), which changes the effective stress and therefore the soil strength. The soil friction angle can be assessed from laboratory tests, such as triaxial compression tests. To obtain the appropriate response, these tests should be carried out on samples at the relevant relative density and stress level, due to effects a) and b) above. Many procedures have been proposed for selecting a representative stress level between the in situ stress and the (average) foundation bearing pressure; a stress of around 10 % of the bearing pressure is typically found to be appropriate [see e.g. Perkins and Madson (2000)[146], Randolph et al. (2004)[155] and White et al. (2008)[200]]. Alternatively, correlations with CPT parameters can be used to assess the spudcan penetration directly according to Schmertmann et al. (1978)[164] and Schmertmann (1970[162], 1978[163]), or to infer the soil relative density, from which the peak friction angle can be estimated. However, the apparent friction angle mobilized during spudcan penetration is lower than the peak value measured in the laboratory (or inferred using CPT correlations), due to mechanisms c) to e) above. Back-analyses of field penetration records [Cassidy et al. (2002b)[44]] and centrifuge tests [White et al., (2008)[200]] have indicated that this apparent friction angle is similar to the critical state friction angle, increasing by up to 5° with increasing relative density. Further guidance on the selection of appropriate friction angle can be found in Section 3.4 of RPS Energy (2010)[158]. If preloading is conducted too quickly for drained conditions to prevail, then positive excess pore pressures can be generated beneath the spudcan, leading to a reduction in bearing capacity [mechanism f) above]. This possibility is particularly relevant for skirted spudcans. E.3 Guidance on A.9.3.2.6.4 — Punch-through — Sand overlying clay — Further details on alternate methods Research reported by Hossain and Randolph (2009b)[95], Hu et el. (2015)[102], Lee et al. (2009)[123] and Teh et al. (2009)[183] has proposed alternative methodologies to those described in A.9.3.2.6.3 and A.9.3.2.6.4 for assessing the bearing capacity of spudcans in layered soil conditions. These are based on the results of centrifuge model experiments and include an evaluation of the penetration resistance of the soil plug formed by the punch-through failure mechanism into the underlying clay. The specific details of each method are described in Lee (2009)[123], Teh et al. (2008)[182] and Teh (2007)[180]; a précis of the method of Teh et al. (2008)[182] for analysing the situation where sand overlies extensive clay is included in the following sections. Teh et al. (2008)[182] investigated the change in bearing failure mechanism during spudcan continuous penetration in sand overlying clay. This led to an alternative approach of evaluating the spudcan penetration resistance-depth (Qnom − d) profile based on a simplified profile shown in Figure E.3-1. The spudcan bearing resistance can hence be represented by the bearing capacity at sea floor (i.e. d = 0), Q0, followed by the maximum bearing capacity, Qpeak (at d = dcrit), and finally the ultimate spudcan bearing capacity when penetrating into the underlying clay (for d ≥ H). Hence, dcrit refers to the depth where punch-through occurs and H is the thickness of the upper sand layer. . No further reproduction or distribution permitted. Printed / viewed by: 309 Key 1 measured spudcan bearing capacity 2 simplified interpretation of measured spudcan bearing capacity 3 sand-clay interface 4 nominal spudcan bearing capacity in clay = Qnom for d ≥ H H thickness of upper sand layer Heff effective thickness of upper sand layer Q0 spudcan bearing capacity at sea floor Qpeak peak spudcan bearing capacity in sand layer at the critical depth Qint spudcan bearing capacity at the sand-clay interface Q spudcan bearing capacity d depth, expressed in metres dcrit critical depth where punch-through occurs Figure E.3-1 — Measured and simplified spudcan ultimate bearing capacity-depth profile in sand overlying clay The formulations for estimating the three characteristic ultimate bearing capacities are given in Teh et al. (2009)[183] and summarized as follows. a) When the spudcan widest cross-section is at the original ground surface (at d = 0), the failure mechanism shown in Figure E.3-2 a) shows that the ultimate bearing capacity, Q0, consists of shearing developing along vertical planes in the overlying sand layer; and general bearing shear failure in the underlying clay. Consideration of soil backflow is not applicable. b) The failure mechanism at the instant of punch-through illustrated in Figure E.3-2 b) reveals that Qpeak consists of shearing along logarithmic spiral failure planes in the upper sand layer; and the mobilisation of underlying clay bearing capacity subjected to vertical and inclined loadings. The inclusion of the inclined loading in the assessment of the underlying clay bearing capacity is made . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 310 © ISO 2023 – All right reserved in view of the presence of shear stress at the clay surface [Love et al. (1987)[128], Burd and Frydman (1997)[36] and Teh et al. (2008)[182]]. Soil backflow is minimal and can hence be ignored. c) When the spudcan penetrates through the underlying sand layer, the failure mechanism shown in Figure E.3-2 c) shows that Qnom for d ≥ H can be assessed by considering the resistance of a sand plug trapped underneath the spudcan with additional side friction [Craig and Chua (1990a)[50]] and a new design depth at the sand plug base elevation. Deep flow mechanism is assumed to occur around the sand plug base. Complete soil backflow is considered here. Figures E.3-3 a) and E.3-3 b) compare the ratio of calculated over measured Q0 and Qpeak, respectively. The calculated values were produced by various methods as indicated in the figures; whereas the measured values were obtained from 18 centrifuge tests reported by Teh et al. (2010)[184] and Craig and Chua (1990a)[50]. The above verification is based on limited test data and further studies can be necessary to evaluate the above proposed approach in the determination of spudcan punch-through in sand overlying clay. a) Bearing capacity at sea floor, Q0 b) Bearing capacity at instant of punch-through, Qpeak c) Spudcan bearing capacity, Qnom, for d ≥ H Key 1 sand layer 2 clay layer 3 shearing along a vertical plane 4 general bearing shear failure 5 shearing along logarithmic spiral failure surface 6 clay bearing shear failure subjected to vertical and inclined loads 7 sand plug 8 side friction 9 deep flow mechanism in clay H thickness of sand layer Q0 bearing capacity at sea floor Qpeak bearing capacity at instant of punch-through Qnom spudcan bearing capacity when d ≥ H d depth of spudcan below top of sand layer Figure E.3-2 — Schematic of spudcan failure mechanisms . No further reproduction or distribution permitted. Printed / viewed by: 311 a) Summary of Q0,calculated/Q0,measured ratio given by various methods b) Summary of Qpeak,calculated/Qpeak,measured ratio given by various methods Key 1 maximum value 2 mean value 3 minimum value Y ratio of calculated bearing capacity over measured bearing capacity (Q0,calculated/Q0,measured) based on various calculation methods (as described for lines designated as a to e) and 18 centrifuge tests reported by Teh et al. (2010)[184] Z ratio of calculated peak bearing capacity over measured peak bearing capacity (qpeak,calculated/qpeak,measured) based on various calculation methods (as described for lines designated as a to e) and 18 centrifuge tests reported by Teh et al. (2010)[184] σ standard deviation a punching shear [Hanna and Meyerhof (1980)[86]] b punching shear [SNAME (2002)[170]] c projected area – 1:3 [SNAME (2002)[170]] d projected area – 1:5 [SNAME (2002)[170]] e Teh et al. (2009)[183] Figure E.3-3 — Comparison calculated and experimental bearing capacities . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 312 © ISO 2023 – All right reserved E.4 Calculated foundation capacities approach E.4.1 General The purpose of this annex is to provide an approach and criteria, in the context of a Step 2b assessment, for the use of calculated foundation capacities based on the factored soil strength (as opposed the use of unfactored strength developed from the preload). This approach can be used in lieu of basing the capacities on the applied preload. Where the criteria are satisfied, assessments adopting such an approach can yield greater foundation capacities and stiffnesses, and consequently an improved outcome from the site assessment. This is typically applicable when the main spudcan-soil contact area is at the sea floor or just within the seabed. See also the considerations in E.4.10. E.4.2 Background The base of a spudcan foundation progressively penetrates deeper into the seabed when subjected to vertical loading from the unit’s self-weight and subsequent preloading operations. In standard jack-up site assessments, the gross vertical bearing capacity of the spudcan, QV, is related to the applied preload spudcan reaction, VLo, and determines the size of the foundation yield surface and bearing capacity envelope. However, the ultimate vertical bearing capacity of the soil can be greater than the applied preload spudcan reaction. For certain combinations of soil profiles and specific spudcan geometries, further inelastic penetration of the spudcan into the soil does not occur when the vertical loading exceeds the applied preload. These situations generally occur where the ultimate vertical bearing capacity of the soil beneath the spudcan is significantly greater than the applied preload at the spudcan. The higher bearing capacity can be available where the spudcan-soil contact area is achieved not as a result of the applied preload, but due to the spudcan underside presenting a flat base, or due to an increase in the spudcan-seabed contact area by filling of voids inside a skirted spudcan. The Step 2b approach is usually based on the assumptions that  the size of the yield surface is determined by the applied preload reaction, and  the foundation rotational stiffness reduces as the footing loading approaches the foundation’s yield surface, becoming zero (i.e. a pinned footing) if the factored loading exceeds the yield surface. Such a response, however, conservatively underestimates the final foundation rotational stiffness for cases where the vertical bearing capacity can reliably be identified to be significantly higher than the applied preload. Where one of the above foundation situations applies, a larger foundation yield surface based on the calculated foundation capacities may be adopted for the determination of the structural and non-linear foundation responses. The foundation rotational stiffness increases with the use of higher calculated capacities due to its dependency upon the size of the foundation yield surface; the use of a larger yield surface reduces the failure ratio, rf defined in A.9.3.4.2.2, for a given load and consequently results in less foundation fixity reduction. NOTE The increased foundation stiffnesses redistribute the moment loading in the legs thereby improving the structural utilisations in the upper leg structure and leg holding system and increasing the moment loading in the legs at the spudcan level and around the leg-to-spudcan connection and the utilisations in these areas, see 13.1.2 and 13.5. The approach outlined in this annex is not intended for preloading a jack-up at a site. The unit should be preloaded to the maximum preload spudcan reaction as defined in the unit's marine operations manual. Preloading of the foundations in such situations serves both as a confirmation of the unfactored . No further reproduction or distribution permitted. Printed / viewed by: 313 predicted penetration response and to ensure that the spudcan-soil contact condition assumed by the site assessment is realized during installation. E.4.3 Suitable spudcan geometries Figure E.4-1a shows examples of spudcan geometries and penetration conditions after preloading for which calculated foundation capacities may be used. These examples are not an exhaustive list of suitable foundation geometries; other foundation geometries not shown can also be suitable. In all cases it should be demonstrated that the application of a vertical loading exceeding the applied preload, up to the vertical bearing capacity calculated in accordance with the methods described in this annex, does not result in further inelastic penetration. The foundation geometries and penetration conditions after preloading shown in Figure E.4-1b where the application of a vertical loading exceeding the applied preload results in further penetration of the spudcan into the soil. These are not suitable for the use of calculated foundation capacities. Provided that full base contact is achieved, the full contact diameter, B, as shown in Figure E.4-1a, can be used to calculate the foundation capacities and fixities. Alternatively, it should be demonstrated that the remaining voids do not affect the foundation stiffnesses and capacities, or that they have been accounted for in the calculations. In these sketches the spudcan tip or skirt tip penetration required to achieve full base contact by preloading is denoted as h2,fullcontact. In the case whereby full contact is achieved by infilling of the voids after preloading, h2,fullcontact corresponds to the spudcan tip or skirt tip penetration achieved by preloading prior to infilling of the void(s). For flat-based spudcans, or skirted spudcans with a predominantly flat-underside, full contact should be achieved between the portion of the spudcan underside and the seabed surface that is used to calculate the foundation capacities. This is especially important where the seabed is not flat or where footprints or other undulations are present. Full contact can be achieved by preloading or, when this is not possible, by the subsequent filling of any remaining internal voids, caused by portions of the spudcan base not in contact with the soil, with competent material. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 314 © ISO 2023 – All right reserved a) Geometries and penetration conditions after preloading that are suitable for use with calculated foundation capacities with corresponding spudcan-soil contact diameter, B b) Geometries and penetration conditions after preloading that are not suitable for use with calculated foundation capacities Figure E.4-1 — Illustration of spudcan geometries and penetration conditions after preloading that are suitable and not suitable for use with calculated foundation capacities Key 1 full contact achieved by void filling 2 void space B effective spudcan-soil contact diameter h2,fullcontact skirt tip penetration required to achieve full base contact . No further reproduction or distribution permitted. Printed / viewed by: 315 E.4.4 Criterion for use of calculated foundation capacities Calculated foundation capacities may be used when the calculated gross vertical bearing capacity, QVC, using material factored representative soil strength parameters, is greater than the gross spudcan reaction during preloading, QVo: QVC > QVo (E.4.3.1) The condition described in Formula (E.4.3.1) arises only for the suitable spudcan geometries and conditions indicated in E.4.3 and where the spudcans are founded upon competent soil layers. The consequences to the calculated capacities and/or stiffnesses of any material entrapped within spudcan skirts during penetration should be considered. The consequences of spudcan internal void filling material should also be considered. The gross vertical bearing capacity should be calculated for the penetration condition after preloading. The spudcan tip or skirt tip penetration is taken as that which is predicted for the applied preload without the application of material factors. The definition of representative soil strength parameters, in this context and the appropriate material factor to be used, are discussed in E.4.5. QVC is calculated using material factored representative soil strength parameters and is related to the vertical load level above which further penetration is predicted from the spudcan vertical bearing capacity profile. The relationship between vertical loading level at which further penetration is predicted and QVC is shown in Figure E.4-2a and Figure E.4-2b for lower estimate and upper estimate soil strength parameters, respectively. Note that for skirted spudcans, the foundation embedment depth, Dembed, is effectively equal to the skirt tip penetration, consequently the submerged weight of any soil within the skirt is above the foundation base level and should be included. The weight of soil plug within the skirts can be accounted for by treating it as additional backfill that has occurred during preloading, and would thus be added to WBF,o. The weight of any void infilling material can be accounted for by treating it as backfill that has occurred after preloading, and would thus be added to WBF,A. The material factor, γm, should be applied when calculating gross capacity QVC; it should not be applied to the soil buoyancy or the weight of soil plug or backfill. Where the unfactored load-penetration curve indicates the possibility for punch-through to occur for vertical loading that exceed the applied preload, specific consideration should be given to the assessment of the punch-through resistance. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 316 © ISO 2023 – All right reserved a) Visualisation of QVC in relation to the spudcan vertical bearing capacity profile calculated using material factored lower estimate representative soil strength parameters b) Visualisation of QVC in relation to the spudcan vertical bearing capacity profile calculated using material factored upper estimate representative soil strength parameters Key 1 available structural spudcan reaction, as defined in Equation A.9.3-1 in A.9.3.2.1.1, calculated using material factored lower estimate representative soil strength parameters 2 available structural spudcan reaction, as defined in Equation A.9.3-1 in A.9.3.2.1.1, calculated using (unfactored) lower estimate representative soil strength parameters 3 available structural spudcan reaction, as defined in Equation A.9.3-1 in A.9.3.2.1.1, calculated using (unfactored) upper estimate representative soil strength parameters 4 available structural spudcan reaction, as defined in Equation A.9.3-1 in A.9.3.2.1.1, calculated using material factored upper estimate representative soil strength parameters h2,fullcontact skirt tip penetration required to achieve full base contact Figure E.4-2 — Visualisation of QVC in relation to the spudcan vertical bearing capacity profile calculated using material factored lower and upper estimate representative soil strength parameters (see E.4.9) E.4.5 Representative soil strength parameters A greater margin of safety should be used when VHM foundation capacities are calculated from estimates of the soil strength parameters, (e.g. for assessments of gravity-based structures, mat-supported jack-ups or mat-supported structures) as compared to situations where the vertical bearing capacity is proven by preloading during installation, as is usually the case for independent leg jack-up . No further reproduction or distribution permitted. Printed / viewed by: 317 units. Consequently, a material factor is incorporated to account for the uncertainties related to the determination of VHM foundation capacity based on the soil strength and the associated foundation settlements beyond the preload-based yield surface. In accordance with ISO 19901-4:2016, 7.3, a material factor, γm, of 1,25 is applied to the estimates of the representative soil strength parameters of undrained shear strength, su, for cohesive soils and the coefficient of friction, tan(φ’), for cohesionless soils. The upper estimate representative soil strength parameter, used in E.4.9, should be multiplied by γm. The material-factored representative soil strength parameters are used to calculate the foundation bearing capacities that can be used for determination of the structural and non-linear foundation responses. In the context of this annex, the representative soil strength should represent a site-specific cautious estimate of the soil strength that exists within the extent of influence that could affect the foundation response. The selected value of the representative soil strength should account for the variability in the soil, and the uncertainty arising from the quantity and quality of the soil strength tests performed. The potential effects of softening or remoulding of the soil due to pre-loading, cyclic loading and changes in shear strength with time should also be considered, see E.4.10.6 and E.4.10.7, respectively. For most scenarios the selected representative soil strength should be a value that is lower than the most probable value. However, for some scenarios, a higher soil strength is more critical to the assessment outcome, such as discussed in E.4.9, and in such situations the selected value should be higher than the most probable value. Where sufficient data exists for a particular soil layer, a statistical treatment of the soil strength data may be used to define the representative soil strength for that layer, for example as described in DNV-RP-C207 (DNV 2021e)[61]. Where limited data exists, subject to the guidance in E.4.10.2, the choice of representative soil strength should correspond to conservative low representative and high representative parameters, depending on which is more critical to the assessment outcome. Further considerations regarding the quality and quantity of soil data are provided in E.4.10.2. E.4.6 Calculated foundation yield surface and fixity When adopting foundation capacities that are based on soil strength parameters rather than proven by preloading, the yield surface used in the foundation fixity analysis should be calculated using material factored representative soil strength parameters. The same factored yield surface should be used for both structural and foundation checks . The assessment should be performed in accordance with a Step 2b level check incorporating the material factor, γm, of 1,25 applied to the estimates of the representative soil strength parameters of undrained shear strength, su, for cohesive soils and the coefficient of friction, tan(φ’), for cohesionless soils, as given in ISO 19901-4. The spudcan (or skirt) tip penetration is taken as that predicted without the application of material factors based on the applied preload for the corresponding soil profile being assessed. The shape of the yield surface can be determined using the approach described in A.9.3.3, or other methods, e.g. finite element analyses. The soil shear modulus and initial foundation rotational stiffnesses can be determined using the approach described in A.9.3.4 without application of material factors, taking into account the effective spudcan diameter and any embedment of the applicable maximum bearing area. For skirted spudcans, the effective weight of the soil plug contained within the spudcan skirt and any void filling material above the plug (see Figure E.4-1a) should be included, see E.4.4. A rotational stiffness reduction relationship is described in A.9.3.4.2.2. Due consideration should be given to select the value of the parameter, n, that provides an appropriate representation of the foundation stiffness reduction factor, fr, in the context of the present annex where the foundation capacity (i.e. yield surface) exceeds the applied preload. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 318 © ISO 2023 – All right reserved The stiffness reduction parameter, n, permits a range of spudcan rotational stiffness reduction relationships to be represented with the stiffness reduction formula, Formula (A.9.3-55). In practice the value of this parameter should be set to suit the best available data (either empirical or analytical) applicable to the jack-up and site. In the absence of directly applicable data, the value of n can be set close to 1,0; it is noted that as n approaches 1,0 the stiffness reduction expression tends towards the form given in Formula (E.4.5-1), which gives the most conservative treatment of stiffness reduction within the framework described in A.9.3.4.2.2. fr = 1 - rf . (E.4.5-1) Alternative yield surfaces and fixity reduction relationships may be adopted if based on, or verified by, an appropriate and detailed study of the soil-structure interaction, for example using finite element analysis. Guidance on the selection of n, for cases where higher foundation stiffnesses are more onerous is provided in E.4.9. E.4.7 Bearing capacity check The bearing capacity check should be performed following the approach described in A.9.3.6.4 by comparing the factored spudcan reactions with the V-H bearing capacity envelope calculated using material factored representative soil strength parameters. No additional bearing capacity resistance factor is required, i.e. γR,VH = 1,0, as the material factor, γm, accounts for the uncertainties in the calculated bearing capacity envelope. If the foundation fails this check a Step 3 analysis can be performed, including the material factors given in E.4.5 and E.4.8. NOTE The foundation bearing capacity utilisations are calculated using vectors from an arbitrary origin in accordance with A.9.3.6.4. To reduce the potential for unrealistic load vectors for leeward legs, when using calculated foundation capacities, the origin of the vectors is taken as 50% of the initial gross ultimate vertical foundation capacity established by preload operations, QVo. When the ground conditions indicate the potential for punch-through, specific consideration should be given to the assessment of the punch-through resistance. For skirted spudcans, the bearing capacity check should include the submerged weight of the soil contained within the spudcan skirt, as discussed in E.4.4. E.4.8 Sliding capacity check The sliding envelope is calculated using material factored representative soil strength parameters and no additional resistance factor, i.e. γR,Hfc = 1,0 as the material factor, γm, accounts for the uncertainties in the calculated sliding capacity. For skirted spudcans the sliding capacity check should include the submerged weight of the soil contained within the spudcan skirt, if applicable. The potential for the critical sliding failure mechanism to pass through the material contained within the skirts (including any infill material) should be assessed. See A.9.4.1: Bransby and Yun (2009)[33] for the case of skirted strip footings; Vulpe et al. (2013)[197] and Vulpe (2015)[198] for skirted spudcans. NOTE The foundation sliding capacity utilisations are calculated using vectors from an arbitrary origin in accordance with A.9.3.6.4. To reduce the potential for unrealistic load vectors for leeward legs when using calculated foundation capacities, the origin for the vectors are taken as 50% of the initial gross ultimate vertical foundation capacity established by preload operations, QVo. E.4.9 Spudcan-to-leg connection and spudcan structural integrity checks Where calculated foundation capacities are used as the basis for the foundation yield surface, the spudcan reactions should be verified as being within the designed structural capacity of the spudcans and the spudcan-leg connections. Alternatively, a detailed spudcan integrity check should be performed. The spudcan reactions resulting from separate assessments that use material factored lower and upper . No further reproduction or distribution permitted. Printed / viewed by: 319 estimate representative soil strength parameters should be considered in the verification of the spudcan-to-leg connection and spudcan structural integrity checks. The upper estimate representative soil strength parameters used throughout the assessment should be multiplied by γm (the lower estimate representative soil strength parameters used throughout the assessment are divided by γm ). Due consideration should be given to select the value of the parameter, n, that provides a conservative representation of the foundation stiffness reduction factor, fr, in the context of the spudcan-to-leg connection and spudcan structural integrity checks. In the absence of directly applicable data, the value of n can be set to -1,0. E.4.10 Precautions and considerations when adopting calculated foundation capacities E.4.10.1 General In addition to the general considerations described in 9.4 and A.9.4, the following precautions and considerations are provided for situations where calculated foundation capacities are used. E.4.10.2 Quality and quantity of soil data In order to use the calculated foundation capacities approach, the quality and quantity of the soil data should be sufficient to enable a reliable assessment of the representative value of the strength of each contributing layer as discussed in E.4.5. These data should be more extensive than for foundations proved by preloading. Potential variations in soil properties below each spudcan, including lateral variability, should be evaluated using geotechnical data correlated with geophysical data and, if applicable, with knowledge from previous operations at the site. E.4.10.3 Hydraulic stability The potential for hydraulic instability, i.e. piping and/or scour, to reduce the contact area between the spudcan and soil should be assessed. Where piping or scour are recognized as a potential risk to the foundation, the effects should be considered and any mitigation measures required should be implemented to ensure foundation integrity. See 9.4.7 and A.9.4.7 for general considerations regarding scour. E.4.10.4 Filling of voids within skirted spudcans For skirted spudcans, where portions of the base are not in contact with the soil after preloading, full contact can be achieved by filling any remaining internal voids with competent material to ensure the calculated foundation capacities and stiffnesses are developed, as illustrated in Figure E.4-1a. The spudcan-soil contact area should, as much as possible, be achieved by preloading to minimise the uncertainties associated with the behaviour of infill material during storm and earthquake loading. The properties of the infill material can influence the horizontal foundation capacity, as described in E.4.8. For certain spudcan types and soil conditions suction can be used to increase the spudcan penetration achieved during preloading and thereby reduce the volume of infilling material required. Where infill material is to be used, the spudcans should be equipped with the necessary pipework and valve arrangements to permit infilling of the voids after preloading and verification of the infilling. The valves should be closed prior to elevated operations to prevent the escape of the infilling material. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 320 © ISO 2023 – All right reserved E.4.10.5 Seabed unevenness, spudcan-footprint interactions and sloping strata 9.4.2 and 9.4.3 provide general considerations regarding hard sloping strata and spudcan-footprint interactions respectively. Relatively flat-based spudcans, such as some of those shown in Figure E.4-1a, are more susceptible to adverse eccentric spudcan support caused by seabed unevenness or sloping strata. Consequently, the potential for seabed unevenness, spudcan footprints or sloping strata to be present at the site should be carefully evaluated for such spudcan geometries. Any voids present between the base of the footing and the seabed surface, caused by seabed unevenness or footprints, should be infilled in accordance with E.4.10.4 or accounted for in the assessment. E.4.10.6 Cyclic degradation/effects from cyclic loading The effects of cyclic degradation can reduce the capacity and should be considered. A.9.3.3.7 provides an approach for incorporating the effects of cyclic loading on the static bearing capacity of clays and should be used for calculated foundation capacities in clays. In the context of calculated foundation capacities, the ratio of the average net vertical loading to the static net vertical bearing capacity can be less than 0,3; in such cases the parameter fcy,V should be calculated using Formula (A.9.3-51) where QVnet is defined as QVC – p’oπB2/4. Further information on such approaches to incorporate the effects of cyclic loading, including for sands, can be found in DNVGL-RP-C212 (DNV 2021f)[62]. Significant cyclic degradation can occur in soils including, amongst others, any un-cemented carbonate soils or any other soils where silt-sized particles, and in particular non-plastic silt, comprise a significant fraction of the material. For such soil types, a detailed assessment would be required to incorporate cyclic effects on the soil parameters to determine whether the material factored vertical foundation capacity is greater or less than the applied preload. Further information on such approaches can be found in Amodio et al. (2015)[19]. The approach described in E.4 can only be used if the calculated material factored vertical foundation capacity, including strength degradation under cyclic loading, is greater than the applied preload. E.4.10.7 Effects of soil drainage The analysis methods outlined in this document are applicable primarily for use in seabed conditions comprising uniform all drained (sand) or all undrained (clay) profiles. For cases where fully drained conditions are assumed to apply it should be confirmed that this assumption applies to both the preloading stage and during storm and earthquake loading. If this is not ensured then partially drained or undrained conditions can apply. This is a particular concern where the material includes silt sized particles and/or compressible soil grains such as carbonate soils. In such situations there is the potential for the material factored vertical foundation capacity during storm and earthquake loading to be less than those developed by preloading. In such cases the approach described in E.4 does not apply. Where undrained conditions are assumed to apply, the in situ undrained soil strength beneath the spudcans can increase over time under the static loading imposed by the jack-up due to consolidation. The favourable effect upon the undrained shear strength may be accounted for, however, assessment of the resulting bearing capacity for this situation requires advanced analysis. Due consideration should be given to the realistic available consolidation time prior to the storm condition being assessed, that accounts for possible delays to the installation that reduce the time for consolidation prior to installation e.g. waiting-on-weather. . No further reproduction or distribution permitted. Printed / viewed by: 321 For the situations discussed in this subclause, a detailed Step 3 assessment involving advanced analysis methods should be performed. E.4.10.8 Silt and carbonate soils As implied in E.4.10.6 and E.4.10.7, the approach described in E.4 is not suited for the following soil conditions:  uncemented carbonate soils;  other soils where silt-sized particles, and in particular non-plastic silt, comprise a significant fraction of the material. These soils should be addressed with care, see 9.4.10. E.4.10.9 Foundation damping Where the ultimate foundation capacity is significantly greater than the loading applied to the foundation, such as for cases where calculated foundation capacities are used, the strains induced in the soil can be less than is assumed for typical assessments of spudcan foundations. In such cases the foundation damping could be less than described in A.10.4.3 and reduced foundation damping should be considered. E.5 Example of simplified free-field liquefaction assessment calculation method CAUTION — The guidance in E.5 should not be used because inconsistencies have been identified. The Clause will be corrected in an Amendment. E.5.1 General Various methods are available for a simplified liquefaction-induced liquefaction assessment. A simplified method (Boulanger and Idriss, 2014[29]), is proposed here. In this method the Cyclic Resistance Ratio (λCRR), based on either shear wave velocity or cone resistance from CPT, is compared to the Cyclic Stress Ratio (λCSR) for a specific site and earthquake intensity. E.5.2 Calculation of cyclic resistance ratio (λCRR) based on shear wave velocity When shear wave velocity data are available, Formula (E.5-1) can be used. λCRR can be computed from the in situ shear wave velocity (Kayen et al., 2015[115]): 𝜆𝜆CRR=𝑒𝑒𝑒𝑒𝑒 􁉊(0,0073𝑉𝑉𝑠𝑠1)2,8011−2,6168ln(𝑀𝑀𝑤𝑤)−0,0099ln􀵫𝜎𝜎v0′􀵯+0,0028𝑅𝑅FC+0,4809𝛷𝛷􀵫PL􀵯−11,946􁉋 (E.5-1) where 𝑉𝑉s1 is the shear wave velocity, 𝑉𝑉s (m/s), normalized to a vertical overburden stress of 1 atmosphere, equal to Vs𝐶𝐶Vs; 𝐶𝐶Vs is a stress correction factor, equal to (Pa𝜎𝜎v0′⁄)0,25 or a maximum value of 1,5 at shallow depths; 𝑃𝑃a is the atmospheric pressure (kPa); 𝑀𝑀w is the earthquake moment magnitude; 𝜎𝜎v0′ is the vertical effective overburden stress (kPa); . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 322 © ISO 2023 – All right reserved 𝑅𝑅FC is the fines content (%) estimated from laboratory or cone data, see also (E.5-3); 𝑃𝑃L is the probability of liquefaction, equal to 0,5 for a best estimate or 0,15 for a more cautious estimate (equivalent deterministic liquefaction relationship); 𝛷𝛷 is the cumulative normal distribution for a normal distribution with a mean of zero and a standard deviation of one; 𝛷𝛷(PL)−1 is the inverse of the normal cumulative distribution with mean of zero and standard deviation of one for the probability of liquefaction of interest, equal to zero for 𝑃𝑃𝐿𝐿 of 0,5 and -1,0364 for 𝑃𝑃𝐿𝐿 of 0,15. E.5.3 Calculation of the cyclic resistance ratio(λCRR) based on CPT data If CPT data are available, 𝜆𝜆CRR can be computed with Formula (E.5-2) (Boulanger and Idriss, 2016[30]). 𝜆𝜆CRR=𝑒𝑒𝑒𝑒𝑒 􀵤𝑞𝑞𝑐𝑐1𝑁𝑁𝑁 113+􁉀𝑞𝑞𝑐𝑐1𝑁𝑁𝑁 1 000􁉁2−􁉀𝑞𝑞𝑐𝑐1𝑁𝑁𝑁 140􁉁3+􁉀𝑞𝑞𝑐𝑐1𝑁𝑁𝑁 137􁉁4−2,60+𝜎𝜎ln(𝑅𝑅)𝛷𝛷(𝑃𝑃L)−1􀵨 (E.5-2) where 𝑞𝑞c1Ncs is the equivalent cone resistance for clean sand corrected to an overburden pressure of 1 atmosphere and equal to 𝑞𝑞c1N+Δ𝑞𝑞c1N; 𝑞𝑞c1N is the cone resistance corrected for overburden stress equal to 𝐶𝐶N(𝑞𝑞c𝑃𝑃a⁄); 𝑞𝑞c is the cone tip resistance, or if a piezocone was used, the cone tip resistance corrected for pore pressure, 𝑞𝑞t, equal to qc+(1−𝑎𝑎)𝑢𝑢2 (kPa); 𝑎𝑎 is the area ratio of the cone equal to the ratio of cross-sectional area of the load cell or shaft to the projected area of the cone; 𝑢𝑢2 is the pore pressure measured behind the cone (kPa); 𝐶𝐶𝑁𝑁 is the overburden correction factor equal to the minimum of (𝑃𝑃a𝜎𝜎v0′⁄)𝑚𝑚 or 1,7; 𝑚𝑚 is an exponent equal to 1,338−0,249𝑞𝑞c1Ncs0,264 Δ𝑞𝑞c1N is an adjustment to compute the equivalent clean-sand cone resistance equal to 􀵬11,9+𝑞𝑞𝑐𝑐1𝑁𝑁14,6􀵰𝑒𝑒𝑒𝑒𝑒 􁉈1,63−9,7𝑅𝑅FC+2−􀵬15,7𝑅𝑅FC+2􀵰2􁉉 𝜎𝜎ln(𝑅𝑅) is the standard deviation of the natural log of 𝑅𝑅, approximately 0.20; 𝑅𝑅 is the cyclic resistance ratio for 𝑀𝑀𝑤𝑤 of 7.5 corrected to an overburden pressure of 1 atmosphere; 𝑅𝑅FC is the fines content (%) and can be estimated from cone data. For example, Boulanger and Idriss (2016)[30] give the relationship in Formula (E.5-3): 𝑅𝑅FC=80(𝐼𝐼𝑐𝑐+𝐶𝐶𝐹𝐹𝐹 )−137, 0%≤𝑅𝑅FC≤100% (E.5-3) 𝐼𝐼c is the soil behaviour type index equal to {[3,47−log(𝑄𝑄)]2+[1,22+log(𝐹𝐹)]2}0,5; 𝑄𝑄 is the normalized cone tip resistance equal to . No further reproduction or distribution permitted. Printed / viewed by: 323 􀵬𝑞𝑞c−𝜎𝜎v0𝑃𝑃a􀵰􁉆𝑃𝑃a𝜎𝜎v0′􁉇𝑛𝑛 𝜎𝜎v0 is the total overburden pressure relative to the sea floor (kPa); 𝑛𝑛 is an exponent, typically 0,5 for sand; 𝐹𝐹 is the normalized sleeve friction equal to 􀵬𝑓𝑓s𝑞𝑞c−𝜎𝜎v0􀵰100% 𝑓𝑓s is the sleeve friction, corrected for pore pressure effects if any (kPa); 𝐶𝐶FC is a curve fitting parameter, typically between ±0,29. E.5.4 Cyclic stress ratio (λCSR) calculation A normalized cyclic stress ratio (𝜆𝜆CSR∗) is given by Formula (E.5-4): 𝜆𝜆CSR∗=𝜆𝜆csr,𝑀𝑀𝑀 =7.5,𝜎𝜎′𝑣𝑣0=1𝑎 𝑎𝑎𝑎 ,=𝜆𝜆CSR(𝐹𝐹DW𝐾𝐾𝜎𝜎)􀵗 (E.5-4) where 𝜆𝜆CSR is the cyclic stress ratio, equal to: 0,65𝑎𝑎max𝑔𝑔𝜎𝜎v0𝜎𝜎v0′𝑟𝑟d 𝑎𝑎max is the peak horizontal ground acceleration (m/s2); 𝑔𝑔 is the acceleration of gravity (m/s2); 𝜎𝜎v0 is the total overburden stress relative to the sea floor (kPa); 𝑟𝑟d is the non-linear shear mass participation parameter, equal to 􁉆1+−23,013−2,949𝑎𝑎max+0,999𝑀𝑀w+0,0525𝑉𝑉s,12m∗16,258+0,201𝑒𝑒0,341􀵫−𝑑𝑑+0,0785𝑉𝑉s,12m∗+7,586􀵯􁉇􁉆1+−23,013−2,949𝑎𝑎max+0,999𝑀𝑀w+0,0525𝑉𝑉s,12m∗16,258+0,201𝑒𝑒0,341􀵫0,0785𝑉𝑉s,12m∗+7.586􀵯􁉇±𝜎𝜎εrd 𝑑𝑑 is the depth in metres (m) beneath the sea floor; 𝑉𝑉s,12m∗ is the average 𝑉𝑉s (m/s) in the upper 12,2 m of the soil column; 𝜎𝜎εrd is the standard deviation of 𝑟𝑟d equal to the minimum of 0,0198𝑑𝑑0,850 or 0,166; 𝜆𝜆csr,Mw=7.5,σ′v0=1atm equivalent uniform cyclic stress ratio for 𝑀𝑀w of 7,5 normalized to a vertical overburden stress of 1 atmosphere; 𝐹𝐹DW is the duration weighting factor equal to 15𝑀𝑀w−1,342 for 5,5<𝑀𝑀w<9,0; 𝐾𝐾𝜎𝜎 is approximately 1,0 for depths of interest to seismic liquefaction assessments; . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 324 © ISO 2023 – All right reserved The following can alternatively be used for rd from Boulanger and Idriss (2016)[30]: 𝑟𝑟𝑑𝑑=exp[𝑎𝑎(𝑑𝑑)+𝑏𝑏(𝑑𝑑) 𝑀𝑀w] where 𝑎𝑎(𝑑𝑑)= −1,012−1,126sin􀵬𝑑𝑑11,73+5,133􀵰 𝑏𝑏(𝑑𝑑)=0,106+0,118sin􀵬𝑑𝑑11,28+5,142􀵰 E.5.5 Ratio of cyclic resistance ratio to cyclic shear stress ratio The simplified methods are based on comparing the cyclic resistance ratio (𝜆𝜆CRR) of a soil layer to the earthquake induced cyclic shear stress ratio (𝜆𝜆CSR). Liquefaction is indicated where the 𝜆𝜆CSR exceeds 𝜆𝜆CRR. . No further reproduction or distribution permitted. Printed / viewed by: 325 Annex F (informative) Guidance on Clause A.12 — Structural strength F.1 Guidance on A.12.6.2.4 — Axial compressive column buckling strength The formulations in AISC (2005)[13] are based on the SSRC column buckling curves (Galambos, 1998)[75] primarily curve 2P. Prior to the introduction of AISC (2005)[13], the compression curve addressed fabricated sections from mill run steel and different material standards covering a range of material yield. In the development of AISC 2005, the reliability evaluation was updated to reflect the general use of 345 N/mm2 material, better steel manufacturing practices, and the limited use of mill steel in fabrication. This review supported the increase in the partial resistance factor for compression to 0,9 (equivalent to 1/0,9 in this document). The referenced AISC column curve represents curve 2P for λ up to Euler Buckling. Curve 2P, and thus the AISC curve, relates primarily to traditional building construction steels typically with yield stresses up to 345 N/mm2, open sections such as wide flanges, and non-symmetrical sections together with their corresponding column tolerances of length/1 000. The AISC formula also applies to prismatic members fabricated from production runs of steel plates and rolled sections. When this type of prismatic member is used on a jack-up the traditional column formulae should be used. However, SSRC found that for high strength steel, up to 700 N/mm2, as used in the construction of chords, and for closed sections the SSRC curve 1P is applicable. The high-strength steels used in jack-up fabrication are required to meet higher manufacturing requirements (e.g. limits on Charpy impact, chemistry and improved welding procedures). In addition, the tighter column tolerances at around length/1 500 for jack-up chord fabrication results in better geometry control than a production run of rolled sections. The effects of residual stresses due to welding and rolling reduce as the yield stress of the material increases. For this reason, the “high-strength” SSRC column curve 1P is appropriate for the assessment of chord members. A good approximation to this, within 0,8 % of the SSRC expression from λ = 0,0 to 2,0, is shown in Figure F.1-1 and used in Formulae (A.12.6-18) and (A.12.6-19) in A.12.6.2.4 b). . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 326 © ISO 2023 – All right reserved Key 1 allowable curve for high strength steel (Fy > 450 N/mm2) 2 allowable curve for normal strength steel (Fy < 450 N/mm2) 3 λ for “tear drop” shaped chord with cross-section area of 0,091 m2 and 3,35 m bay height 4 λ for “tear drop” shaped chord with cross-section area of 0,158 m2 and 4,88 m bay height 5 λ for a split tubular chord with cross-section area of 0,079 m2 and 3,35 m bay height λ column slenderness parameter as defined in A.12.6.2.4 Pp/(AFyeff) ratio of maximum allowable axial force based on member slenderness to axial force required to yield entire cross-section a SSRC column curve 1P. b SSRC column curve 2P. c ISO 19905-1 curve for normal strength steel (Fy < 460 N/mm2). d ISO 19905-1 curve for high strength steel (Fy > 460 N/mm2). e Allowable curve for normal steel (including the partial resistance factor of 1,1). f Allowable curve for high strength steel (including the partial resistance factor of 1,1). Figure F.1-1 — Comparison of column curves F.2 Guidance on A.12.6.3.2 — Interaction formula approach — Determination of η Determination of the correct value of η is carried out by calculation of the nominal strength of the member about axes other than the x- and y-axes. This can be done in the normal manner based on the effective plastic section modulus with reductions for local buckling if applicable. Although a beam does not necessarily bend in the same plane as the applied moment when the bending plane is at an angle to the orthogonal axes, it is not expected that the capacity is greatly affected. Once the nominal bending strength has been calculated for a few angles between the x- and y-axes, the value for η can be calculated using a graphical procedure (see Figure F.2-1), or by an iterative procedure. It has been found that a successful iterative procedure is the use of coupled formulae, setting a = M′uex/Mnx and b = M′uey/Mny resulting in Formula (F.2-1): . No further reproduction or distribution permitted. Printed / viewed by: 327 +1ln(1)ln()ibaηη−= (F.2-1) where the initial value η = 1,5 and the accelerating step is as given by Formula (F.2-2): ηi+2 = 0,5(ηi+1 + ηi) ( F.2-2) The three angles chosen, 30°, 45° and 60° give a good spread over the 90° range. It is not the intention to fit a curve through all the values from the three angles but merely find the lowest value to η. This can still make the formula conservative although considerably less so than for η = 1,0. The interaction formula exponent for biaxial bending, η, is calculated from the formula 1uayuazbzby10,MMMMηηη+= Key X ratio of the applied bending moment to the allowable bending moment about the z axis: Muaz/Mbz Y ratio of the applied bending moment to the allowable bending moment about the y axis: Muay/Mby 1 interaction formula exponent for biaxial bending, η = 2,0 2 interaction formula exponent for biaxial bending, η = 1,5 3 interaction formula exponent for biaxial bending, η = 1,25 4 interaction formula exponent for biaxial bending, η = 1,0 5 interaction formula exponent for biaxial bending, η = 0,75 Figure F.2-1 — Graphical approach to the determination of η F.3 Guidance on A.12.6.3.3 — Interaction surface approach The following interaction surfaces and data are based on Dyer (1992)[67]. There are likely to be other sections that are not included in the tables associated with each diagram. Sections not included in F.3 should be developed from first principles, see for example Duan and Chen (1990)[65]. For sections that . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 328 © ISO 2023 – All right reserved are unsymmetric about a particular axis, the proper positive sign conventions for the moments are given on the cross-sectional diagrams. The utilization developed for each cross section is calculated for a specific value of P/Py. The limiting utilization is based on a function of the two applied moments, My and Mz, and the two moment capacities, M'py and M'pz, for a specific value of P/Py. It takes account of the amount of axial load only by specifying which of the concentric plots should be used. It is, therefore, possible to have a high axial utilization (i.e. a high value of P/Py) but a low overall member utilization because there are small moments My and Mz. While this gives the correct limiting utilization, it can give an unrealistic impression of the member utilization when compared to unity. In order to correct this, a relative utilization Uint.rel can be approximated by determining the function as given by Formula (F.3-1): 1yzpzint.relyypypzpz1///MMMKPPUPPMMMKξξξ−=+−+′′− (F.3-1) where the parameters are defined in Figures F.3-1 to F.3-4 and K is zero except when assessing triangular chords with single racks (Figure F.3-4). It is important that Uint.rel not be used for any purpose except to give a measure of the overall section relative utilization; the check against unity is given in each of the individual Figures F.3-1 to F.3-4. For the strength check, the applied member forces (P, My, Mz in Annex F) should be Pu, Muey, Muez as defined in A.12.6.3.2. For the beam-column check, the applied member forces (P, My, Mz in Annex F) should be Pu, Muay, Muaz as defined in A.12.6.3.2. . No further reproduction or distribution permitted. Printed / viewed by: 329 Strength interaction formulae (for mapping of the variables; see A.12.6.3.3) are as given by Formula (F.3-2): 1222yzpypz10/,MMMM+≤′′ (F.3-2) where for (P/Py) ≤ 0,6: 1,1pypyycos2π′=PMMP 07pzpzy2,cosPMMPπ′= for 1,0 > (P/Py) > 0,6: pypyy1391,PMMP′=− pzpzy1711,PMMP′=− When (P/Py) ≥1,0, the member has failed. Key P chord member axial force Py chord member axial strength My and Mz local y- and z-axis bending moments Mpy and Mpz local y- and z-axis bending strengths M'py and M'pz adjusted local y- and z-axis bending strengths used in simplified interaction formulae Figure F.3-1 — Interaction formulae/curves for tubular chords with double central racks . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 330 © ISO 2023 – All right reserved Table F.3-1 — Data for tubular chords with double central racks Legend: Chord dimensions: All dimensions are in millimetres, yield stresses are in MPa <--- Yield ---> Stress Design L1 t1 L2 t2 D t3 Fy1 Fy2 Fy3 Bay Ht BMC JU-300-CAN (Zapata Scotian) 991 127 0 0 914 44 690 0 690 5532 48 CFEM T2001 (Hitachi Redesign) 960 18 121 140 960 52 690 690 690 4500 Btm 3 bays 34 4100 Top 3 bays 26 4050 Middle bays 34 42 CFEM T2005 650 20 108 140 800 28 700 685 650 or 5050 30 700 a 31 32 33 35 36 38 40 700 685 700 44 34 700 685 650 38 42 CFEM T2600 650 20 120 140 800 33 700 700 700 6000 35 38 40 41 43 45 47 49 50 51 52 55 56 57 58 a Early CFEM T2005 designs use 650 MPa steel for tube; later designs use 700 MPa steel. . No further reproduction or distribution permitted. Printed / viewed by: 331 Table F.3-1 (continued) <--- Yield ---> Stress Design L1 t1 L2 t2 D t3 Fy1 Fy2 Fy3 Bay Ht MODEC 200 450 15 102 127 559 27 490 690 490 5486 27 MODEC 300 450 25 102 127 559 34 490 690 490 5486 28 34 15 40 20 40 27 40 60 40 115 40 MODEC 400 (Trident 9) 690 20 102 127 800 30 490 690 490 6200 20 35 35 35 Hitachi K1025/31/32 900 18 100 127 900 32 690 690 690 5160 18 36 18 50 20 40 20 42 Hitachi K1026 (Neddrill 4) 950 18 100 127 950 32 690 690 690 4360 18 36 20 42 Hitachi K1056/7 1000 28 130 178 1000 47 690 730 690 4600 30 50 30 52 30 60 30 64 60 60 60 64 4000 ETA Robray 300 (Asia Class) 627 10 127 127 762 22 690 690 690 5486 11 13 14 16 17 19 25 32 ETA Europe Class 627 38 140 140 762 22 690 690 690 5486 51 64 76 89 102 114 127 a Early CFEM T2005 designs use 650 MPa steel for tube; later designs use 700 MPa steel. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 332 © ISO 2023 – All right reserved Strength interaction formulae (for mapping of the variables; see A.12.6.3.3) are as given by Formula (F.3-3): 1222yzpypz10/,MMMM+≤′′ (F.3-3) where for (P/Py) <1,0: 185pypyy1,PMMP′=− for (P/Py) <1,0: 225pzpzy1,PMMP′=− When (P/Py) ≥1,0 the member has failed. Key P chord member axial force Py chord member axial strength My and Mz local y- and z-axis bending moments Mpy and Mpz local y- and z-axis bending strengths M′py and M′pz adjusted local y- and z-axis bending strengths used in simplified interaction formulae Figure F.3-2 — Interaction formulae/curves for split tubular chords with opposed central racks (doubly symmetrical) . No further reproduction or distribution permitted. Printed / viewed by: 333 Table F.3-2 — Data for split tubular chords with double central racks Legend: Chord dimensions All dimensions are in millimetres, yield stresses are in MPa a) Sections used in the derivation of Figure F.3-2 and Formula (F.3-3): Yield stress Design L1 t1 D t2 t3 L4 t4 Y1 H1 H2 Fy1 Fy2 Bay Ht F & G L780 (Lower bays) 400 152 381 25 25 0 0 0 191 165 621 690 3658 F & G L780 (Upper bays) 400 127 381 25 25 0 0 0 191 191 621 450 3658 F & G L780 m2 (Lower bays) 400 152 381 32 32 0 0 0 191 165 621 690 3658 F & G L780 m2 (Upper bays) 400 127 381 32 32 0 0 0 191 191 621 517 3658 F & G L780 m5 (Monitor) 401 178 381 81 57 0 0 51 178 178 690 690 4267 F & G L780 m5 (Monarch) 401 178 381 81 51 0 0 51 178 178 690 690 4267 F & G L780 m6 611 178 584 83 38 0 0 95 292 292 690 690 5486 MSC CJ62 (Lower bays) 650 210 600 65 48 0 0 75 270 270 690 690 6927 MSC CJ62 (Upper bays) 650 210 600 55 40 0 0 75 270 270 690 690 6927 MSC CJ50 (1) (Concept) 550 210 520 25 25 0 0 0 260 260 690 690 5608 MSC CJ50 (2) (Concept) 550 210 520 25 35 0 0 0 260 260 690 690 5608 Technip TPG 500 (1) 722 160 680 75 61 0 0 20 340 340 690 540 6000 Technip TPG 500 (2) 722 160 680 75 37 0 0 55 340 340 690 540 6000 Technip TPG 500 (3) 722 160 680 62 37 0 0 36 340 340 690 540 6000 Technip TPG 500 (4) 722 160 680 58 37 0 0 30 340 340 690 540 6000 Technip TPG 500 (5) 722 160 680 50 37 0 0 19 340 340 690 540 6000 Technip TPG 500 (6) 722 160 680 50 37 510 30 19 340 340 690 540 6000 b) Additional data for newer sections that were NOT used in the derivation of Figure F.3-2 and Formula (F.3-3). Figure F.3-2 and Formula (F.3-3) should not be used for their evaluation: Yield stress Design L1 t1 D t2 t3 L4 t4 Y1 H1 H2 Fy1 Fy2 Bay Ht LeTourneau TARZAN 381 165 356 44 32 - - 54 178 178 690 690 LeTourneau WORKHORSE & 240-C 381 165 356 63 38 - - 66 178 178 690 690 LeTourneau Super Gorilla (Hull 219 - “Gorilla V”) 584 191 559 108 38 - - 121 279 279 690 690 LeTourneau Super Gorilla & Super Gorilla XL 584 191 559 115 38 - - 92 279 279 690 690 MSC CJ70-150-MC (lower part) 650 210 600 95 70 - - 100 285 285 690 690 7587 MSC CJ70-150-MC (top part inner chord) 650 210 600 82,5 60 - - 90 285 285 690 690 7587 MSC CJ70-X150-A (lower part) 640 210 600 95 70 - - 100 285 285 690 690 7587 MSC CJ70-X150-A (top part inner chord) 640 210 600 82,5 60 - - 90 285 285 690 690 7587 MSC CJ50 (W-Larissa) 610 150 520 24 24 - - 0 257 257 690 690 5969 MSC CJ50 (Tam Dao) 640 150 520 18 18 - - 0 257 257 690 690 5969 MSC CJ50-X100-MC (lower part) 550 160 520 55 40 - - 60 235 235 690 690 4618 MSC CJ50-X100-MC (top part inner chord) 550 160 520 55 40 - - 60 235 235 690 690 5938 MSC CJ50-X80SJ (lower part) 550 152,4 520 55 40 - - 60 238,8 238,8 690 690 4948 MSC CJ50-X80SJ (top part inner chord) 550 152,4 520 55 40 - - 60 238,8 238,8 690 690 5938 MSC CJ46-X100-D (lower part) 540 150 520 28 28 - - 0 193 193 690 690 4084 MSC CJ46-X100-D (top part inner chord) 540 150 520 28 28 - - 0 193 193 690 690 5027 MSC CJ46-X100-D COSL (lower part) 540 150 520 32 32 - - 0 193 193 690 690 4084 MSC CJ46-X100-D COSL (top part inner chord) 540 150 520 28 28 - - 0 193 193 690 690 5027 MSC NG-2500X (lower part) 400 120 356 30 25 - - 30 143 143 690 690 2827 MSC NG-2500X (top part inner chord) 400 120 356 35 25 - - 35 143 143 690 690 3142 MSC NG-1700 (Bima) 391,5 95 355,6 18,5 18,5 - - 0 152,5 152,5 690 500 5670 . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 334 © ISO 2023 – All right reserved Strength interaction formulae (for mapping of the variables; see A.12.6.3.3) as given by Formula (F.3-4): 1yzpypz10/,MMMMξξξ+≤′′ (F.3-4) where, for (P/Py) <1,0: 145pypyy1,PMMP′=− when Mz ≥ 0,0: 23yyy18272856,,,,PPPPPPξ=++− and 1112112pzpzy1/,,PMMP′=− when Mz < 0,0: ξ = 1,8 and either for 1,0 > (P/Py) > 0,25: 145pzpzy110753,,PMMP′=−−− for 0,25 ≥ (P/Py): M′pz = −Mpz When (P/Py) ≥ 1,0 the member has failed. Key P chord member axial force Py chord member axial strength My and Mz local y- and z-axis bending moments Mpy and Mpz local y- and z-axis bending strengths M′py and M′pz adjusted local y- and z-axis bending strengths used in simplified interaction formulae ξ interaction formula exponent for biaxial bending used in simplified interaction formulae Figure F.3-3 — Interaction formulae/curves for tubular chords with offset double racks . No further reproduction or distribution permitted. Printed / viewed by: 335 Table F.3-3 — Data for tubular chords with offset double racks Legend: Chord dimensions All dimensions are in millimetres; Yield stresses are in MPa <--- Yield ---> Stress Design D t1 L1 L2 t2 t3 Fy1 Fy2 Fy3 Bay Ht Yena Ycos E Levingston 011-C 914 29 305 906 127 0 483 621 0 4826 84 100 16 33 75 90 15 Levingston 111 1016 32 305 1047 127 0 690 690 0 4877 73 73 0 35 68 68 0 Mitsui JC-300 (Key Hawaii) 1016 32 305 1046 127 0 690 690 0 5650 78 78 0 34 0 35 66 66 0 Mitsui 1-off (Key Bermuda) 1016 29 305 1046 127 0 690 690 0 4672 0 Most of leg 1016 29 305 1046 127 0 690 690 0 5050 0 Towage Section 32 5050 73 73 0 " 36 5050 66 66 0 " Hitachi Drill-Hope 762 30 190 882 127 0 690 690 0 5500 57 57 0 32 55 55 0 Hitachi C-150 (Ile Du Levant) 762 30 190 890 130 0 690 690 0 5500 60 60 0 Hitachi K1040/44/45 900 30 300 882 127 0 690 690 0 4800 77 77 0 Btm 2 bays 30 5090 77 77 0 Rest of leg 35 5090 42 5090 60 60 0 Hitachi K1060 (Sagar Lakshmi) 900 30 300 854 127 13 690 690 690 5260 84 84 0 31 0 32 0 34 77 77 0 Robco 350-C 876 29 292 881 127 0 690 690 0 5461 83 83 0 Btm 3 bays 876 38 68 68 0 " 864 29 89 89 0 Rest of Leg 864 32 82 82 0 " where Yena is the distance from the origin to the elastic neutral axis; Ycos is the distance from the origin to the centre of squash (plastic neutral axis); E is the distance between the elastic and plastic neutral axes. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 336 © ISO 2023 – All right reserved Strength interaction formulae (for mapping of the variables; see A.12.6.3.3) as given by Formula (F.3-5): 1yzpzpypzpz10//,/MMMKMMMKξξξ−+≤′′− (F.3-5) where, for (P/Py) < 1,0: 23yyy080404,,,PPPKPPP=−++ and 21pypyy1,PMMP′=− When (Mz/Mpz) ≥ K: 145pzpzy1,PMMP′=− and ξ = 1,45 When (Mz/Mpz) < K: 1104104pzpzy1/,,PMMP′=−− and 2yy14523547,,,PPPPξ=++ When (P/Py) ≥ 1,0, the member has failed. Key P chord member axial force Py chord member axial strength My and Mz local y- and z-axis bending moments Mpy and Mpz local y- and z-axis bending strengths M′py and M′pz adjusted local y- and z-axis bending strengths used in simplified interaction formulae ξ interaction formula exponent for biaxial bending used in simplified interaction formulae K major axis moment limiting value used to define simplified interaction formula exponent; it is the value of Mz/Mpz at which My/Mpy is a maximum. Figure F.3-4 — Interaction formulae/curves for triangular chords with single racks . No further reproduction or distribution permitted. Printed / viewed by: 337 Table F.3-4 — Data for triangular chords with single rack . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 338 © ISO 2023 – All right reserved Design L1 t1 L2 t2 L3 t3 L4 t4 L5 t5 t6 X1 Y1 Y2 Y3 Fy1 Fy2 Fy3 Fy4 Fy5 Bay Ht Yena Ycos E MarLet Standard (3/4" side plates) 711 51 466 19 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 259 279 20 MarLet Standard (7/8" side plates) 711 51 466 22 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 259 279 20 MarLet Standard (1" side plates) 711 51 466 25 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 260 279 19 MarLet Standard (1.5" side plates) 711 51 466 38 213 127 0 0 0 0 0 236 457 0 0 483 483 587 0 0 3408 262 279 17 MarLet Standard + side stiffeners 711 51 466 19 213 127 0 0 127 25 0 236 457 0 211 483 483 587 0 483 3408 260 279 19 MarLet Std 116 (1"x4" rack stiffeners) 711 51 466 19 213 127 102 25 0 0 0 236 457 524 0 483 483 587 483 0 3408 278 296 18 MarLet 116 North Sea (1"x4"+1"x12" stifnrs)711 51 466 19 213 127 102 25 305 25 0 236 457 524 118 483 483 587 483 483 3408 276 291 15 MarLet 116 (1"x4"+1.5"x12" stifnrs) 711 51 466 19 213 127 102 25 305 38 0 236 457 524 124 483 483 587 483 483 3408 277 291 14 MarLet 116 Juneau (2"x4"+1"x12" stifnrs) 711 51 466 19 213 127 102 51 305 25 0 236 457 524 118 483 483 587 483 483 3408 290 304 14 MarLet Gorilla (150-88) 813 76 573 57 222 140 0 0 0 0 0 248 600 0 0 483 483 620 0 0 5113 302 323 21 MarLet Super 300 813 76 607 38 222 140 0 0 0 0 0 268 600 0 0 483 483 620 0 0 5113 298 323 25 813 76 607 38 222 140 0 0 305 51 0 268 600 0 296 483 483 620 0 483 5113 327 346 19 MarLet 300 Slant 711 64 441 38 213 127 0 0 0 0 0 218 457 0 0 414 414 414 0 0 2556 245 245 0 LeTourneau 150 (3/4" side pl) 711 51 466 19 213 127 0 0 0 0 0 236 457 0 0 414 414 620 0 0 2556 259 302 43 LeTourneau 150 (1.125" side pl) 711 51 466 29 213 127 0 0 0 0 0 236 457 0 0 414 414 620 0 0 2556 259 303 44 LeTourneau 150 (1.5" side pl) 711 51 466 38 213 127 0 0 0 0 0 236 457 0 0 414 414 620 0 0 2556 262 298 26 LeTourneau 46,47 559 44 432 13 178 89 0 0 0 0 0 166 432 0 0 ? ? ? 0 0 3408 224 224 0 LeTourneau 4,9 559 51 565 13 197 102 0 0 0 0 0 178 533 0 0 ? ? ? 0 0 3430 286 286 0 Mitsubishi MD-T76J 750 50 574 25 225 125 0 0 0 0 0 226 575 0 0 687 687 687 0 0 3456 315 315 0 Gusto 1-off: (Maersk Endeavour) 800 60 592 30 283 127 0 0 0 0 0 359 443 0 0 620 620 620 0 0 4800 284 284 0 800 90 534 40 283 127 0 0 0 0 0 331 443 0 0 620 620 620 0 0 4800 255 255 0 800 110 488 50 283 127 0 0 0 0 0 307 443 0 0 620 620 620 0 0 4800 244 244 0 Gusto 1-off: (Maersk Explorer) 800 76 535 38 279 127 0 0 0 0 0 337 453 0 0 690 690 690 0 0 4539 268 268 0 800 64 549 38 279 127 0 0 0 0 0 344 453 0 0 690 690 690 0 0 4539 282 282 0 800 51 562 32 279 127 0 0 0 0 0 351 453 0 0 690 690 690 0 0 4539 297 297 0 800 51 562 29 279 127 0 0 0 0 0 351 453 0 0 690 690 690 0 0 4539 297 297 0 BMC 1-off design (Trident 7) 711 38 356 19 279 127 0 0 0 0 25 264 204 0 0 ? ? ? 0 0 3335 197 197 0 ADDITIONAL DATA - THESE SECTIONS WERE NOT INCLUDED IN THE ANALYSES USED TO DERIVE Figure F.3-4 AND THEREFORE Figure F.3-4 SHOULD NOT BE USED FOR THEIR EVALUATION LeTourneau Super 116 No Strapping - Hull 222 & Up 711 51 460 32 222 127 - - - - - 240 448 - - 587 587 690 With Strapping 711 51 460 32 222 127 - - 254 32 - 240 448 - 180 587 587 690 - 587 LeTourneau Super 116E 127 mm Rack Plate 711 51 460 32 222 127 - - - - - 240 448 - - 587 587 690 - - 165 mm Rack Plate 711 51 392 38 286 165 - - - - - 233 384 - - 690 690 690 - - Where Yena is the distance from the origin to the elastic neutral axis; Ycos is the distance from the origin to the centre of squash (plastic neutral axis); E is the distance between the elastic and plastic neutral axes. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 339 Annex G (informative) Contents list for typical site-specific assessment report Tables G.1 to G.15 provide an outline for the contents of a site-specific assessment report. Table G.1 — Jack-up and site Element Jack-up name Jack-up type Operator Site name Latitude Longitude Table G.2 — Data check Data Does it exist? Jack-up data Is jack-up in class? Soils data Prior experience Adjacent infrastructure Metocean data Arrangement at site Jack-up heading (required if using directional data) Water depth Hull clearance above LAT Conductor top tension/support mechanism Conductor diameter and number Earthquake data Accidental situations Operator requirements (e.g. required airgap) Exposure level Agreed consequence class Life safety category . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 340 © ISO 2023 – All rights reserved Table G.3 — Site-specific assessment results summary Site-specific assessment results summary Is it acceptable? Is jack-up suitable for the specified operation at the site and time of year? Are there specific seasonal and/or operational restrictions or limitations Minimum leg reserve above upper guide Foundation fixity used? Preload OK Foundation OK Member strength OK Overturning OK Possible infrastructure interaction Hull displacement Earthquake Accidental . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 341 Table G.4 — Jack-up data Jack-up data Value Length Breadth Depth Standard leg length No of legs No of chords/leg (1 to 4) Longitudinal leg spacing Transverse leg spacing Chord spacing Chord spacing Reference point for chord spacing, e.g. pitch points Weight of one leg including spudcan, including permanent ballast, but excluding water ballast and buoyancy Weight of one spudcan, including permanent ballast, but excluding water ballast and buoyancy Are legs (not spudcans) free-flooding? Type of holding system (jacks or fixation system) Number of jacks per leg Jack holding strength (jacking) Jack holding strength (design maximum holding) Jack holding strength (preload holding) Jack holding strength (ultimate) Light ship Movable fixed load Variable load Total maximum hull weight Total minimum hull weight Overall hull centre of gravity (and tolerance where applicable) Total available preload Type of preload procedure (e.g. one leg at a time) Maximum preload spudcan reactions at the seabed using chosen preload method (including leg/spudcan weight and buoyancy) Bow leg Port leg Starboard leg Other legs Spudcan diameter Spudcan height Spudcan volume Maximum bearing area of spudcan Distance from spudcan maximum bearing area to tip Advertised operating water depth Designer Class/type Classification society . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 342 © ISO 2023 – All rights reserved Table G.5 — Arrangements at site Arrangements at site Value Installed leg length Distance from keel to top of upper guide Hull clearance above LAT Water depth Expected penetration with full preload Reserve of leg Table G.6 — Metocean conditions Metocean conditionsa Value/answer 50-year independent extremes or 100 year joint probability? Partial action factor Has directional metocean data been used? Has seasonal metocean data been used? Water depth Wave details Maximum wave height Associated wave period Type of associated wave period supplied (intrinsic or apparent) Significant wave height Peak period Type of peak wave period supplied (intrinsic or apparent) Wave crest height Wind speed (at 10 m above water level, collinear with wave) 1 hour wind speed 1 minute wind speed (required) 3 second gust Surge Tide Reserve on hull clearance Hull elevation above LAT Expected storm settlement Other allowances, e.g. reservoir settlement Current Surface current (collinear with wind and wave) Bottom current (collinear with wind and wave) Current profile details Marine growth Profile Predeployment marine growth profile Are there operational restrictions (e.g. variable load limits, heading, air gap, leg/guide location)? Are there specific operator requirements that may affect the suitability for the site? a The contents of this table should be expanded as necessary to account for directional and seasonal data. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 343 Table G.7 — Site investigation Site investigation Does it exist? Year Bathymetry survey Shallow seismic survey Intrusive site investigation (soils boring/CPT) Magnetometer survey Table G.8 — Site hazards Site hazards Description Pipeline hazards Adjacent structures Site move-on hazards, e.g. mudslides, sand waves, footprints, seabed slope Table G.9 — Soils Soils Value/description Distance from location of survey General soils description Seabed slope/features Profile details Variability over area Confidence in data Previous experience in the field Load penetration curve Range of predicted penetrations after preloading Is there a punch-through potential during installation? Yes/No Method for mitigating hazards Is there a risk of punch-through or significant settlement if the foundation reactions exceed capacity developed by preloading? Yes/No Method for mitigating hazards Does the predicted penetration curve show potential for punch-through or significant settlement (precipitous settlement) if the foundation reactions exceed those assessed? NOTE For information only: there is no acceptance criterion. Previous spudcan footprints? Yes/No Method for mitigating hazards Other geotechnical hazards? Yes/No Method for mitigating hazards Is there scour potential? Yes/No Method for mitigating hazards . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 344 © ISO 2023 – All rights reserved Table G.10 — Analysis path/route/assumptions Analysis path/route/assumptions Table G.11 — Spudcan fixity used in analysis Spudcan fixity used in analysis Value Initial stiffness (for each spudcan, if soils differ) Rotational Lateral Vertical Ultimate capacity Rotational Lateral Vertical Table G.12 — Earthquake analysis Earthquake analysis Description Does site fall below the ISO 19905-1 cut-off (ISO 19901-2 seismic zone 2, or level 1 under the conditions specified in 10.7)? Was an earthquake analysis performed? Source of the earthquake data What vertical ground motions were used (in many cases the critical condition)? Was vertical spectrum some ratio of lateral ground motion spectrum, and if so, how was it derived? Is spudcan fixity different from metocean analysis and, if so, what value was used? Was linear analysis sufficient to prove acceptability of site? Describe non-linear analysis, if used What was limit on vertical settlement, and differential settlement? Were effects on platform that jack-up was working over considered, if applicable (e.g. effects of interaction due to lateral motions or vertical settlement)? Table G.13 — Accidental situations Accidental situations Description Were any accidental situations assessed (e.g. collision)? What were the results of the analyses? . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 345 Table G.14 — Intermediate results Intermediate results Value Natural period (with fixity and P-Δ effects) DAF If SDOF, give DAF on BS, KDAF,SDOF Stability of DAF with simulation duration (2-stage) Stability of static and dynamic MPME (1-stage) If random, give DAFs on BS and OTM, KDAF,RANDOM Factored wind, wave/current, inertial BSs and OTMs The DAF calculated in the SDOF analogy (KDAF,SDOF) should not be directly compared to the DAF determined with a stochastic wave assessment (KDAF,RANDOM). Because the method of determining the relevant inertial loadset is different, the same value of KDAF,SDOF and KDAF,RANDOM produces different total global responses; see Figure A.10.5-1. Table G.15 — Analysis results (utilization checks) Analysis results (utilization checks) Value Preload Potential for punch-through when preloading? Mitigations proposed Foundation Bearing check Sliding check Magnitude of additional penetration under storm loads Potential for punch-through when elevated? Mitigations proposed Overturning Chord member strength Horizontal member strength Diagonal member strength Jacks/fixation system Results of earthquake analysis (if applicable) . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 346 © ISO 2023 – All rights reserved Annex H (informative) Regional information H.1 General This annex contains provisions for a limited number of regions; the content has been developed by ISO/TC 67 experts from the region or country concerned to supplement the provisions of this document. Each provision can be considered to constitute the additional information required for regional implementation for the particular region or country defined. The regional information can provide regional and national data that can include regional environmental conditions and local assessment and operating practices. The regulatory framework can be explained but neither regulatory requirements nor reference to specific legislation is included in this document. H.2 Norway H.2.1 Description of region The provisions in H.2 apply to areas under Norwegian jurisdiction. H.2.2 Technical requirements H.2 contains additional requirements for site-specific assessment of jack-ups in Norwegian waters. The following provisions are in addition to, or an alternative to, those specified in the appropriate referenced subclauses.  5.3 d) The site-specific risks, such as collision risk and geohazard, shall be evaluated. ALS actions shall be defined based on a site-specific risk analysis.  5.5.2 and 8.8 An action factor of 1,25 should be used for jack-ups in L1, in combination with environmental conditions with an annual probability of exceedance 10−2. An action factor of 1,25 should be applied for jack-ups in L2 in occupied conditions. An action factor of 1,15 can be used for evacuated jack-ups in L2, in combination with environmental conditions an annual probability of exceedance 10−2.  6.4 100 year joint probability metocean data shall be used for extreme storm event assessments (ULS assessment) for jack-ups in Norwegian waters. If reliable 100 year site-specific joint probability data do not exist, a combination of 100 year waves, 100 year wind and 10 year current can be applied.  6.5 The relaxation “For sites where previous operations have been performed by jack-ups...” shall be applied only if the previous jack-up has been evaluated in accordance with this document and has an equal or a more severe performance than the jack-up in question.  6.5 Soil investigations after installation are not considered good practice.  8.8.1 When checking the ULS, the SLS, the ALS and the FLS, the action factors shall be used in accordance with Table H.2.2-1 for L1. For L2 the action factor 1,25 can be reduced to 1,15 for environmental actions. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 347 Table H.2.3-1 — Partial action factor for the limit states controls for site-specific evaluations Limit state Load case Action due to fixed load GF Action due to variable load Gv Environmental action Ea SLS — 1,0 1,0 1,0 ULS ab 1,2c 1,3 0,7 ULS b 1,0 1,0 1,25 ALS Abnormal effectsd 1,0 1,0 1,0 ALS Damaged conditionse 1,0 1,0 1,0 FLS — 1,0 1,0 1,0 a Earthquake shall be handled as environmental action within the limit state design for ULS and ALS. b For fixed and/or variable loads, GF and Gv, an action factor of 1,0 shall be used where this gives the most unfavourable action effect. c If the actions do not have a well-defined upper limit, e.g. uncertainty in the fixed loads, the coefficient 1,2 should be increased to 1,3. d Actions with annual probability of exceedance of 10−4. e Environmental actions with annual probability of exceedance of 100 (one year return period). The ULS load case “a” and the FLS are normally covered by the RCS class certificates. If the facility is used for more than five years on the same site, a site-specific fatigue analysis shall be performed.  10.5.2 The SDOF-method can be used only when it is conservative.  10.7 An annual probability of exceedance of 10−2 in ULS and 10−4 in ALS shall be used for earthquakes.  13.6 For L1 platforms, the hull elevation shall be sufficient to clear the crest elevation of waves with an annual probability of exceedance 10−4. Alternatively, it may be documented that the platform has sufficient strength to withstand metocean actions (for the ALS) with an annual probability of exceedance 10−4.  13.11 An annual probability of exceedance 10−2 shall be used for temperature.  Annex A Statements related to return periods and action factors are covered by the additional requirements above.  A.6.4.2.2 A factor of 1,9 can be used between the individual extreme wave height (Hmax) and the significant 100 year wave.  A.7.3.1.1 If site-specific joint probability data does not exist, a combination of 100 year waves, 100 year wind and 10 year current can be applied.  A.7.3.2.5 The marine growth should be in accordance with ISO 19901-1:2015, Table B.2, if the jack-up is on one site for a long time. The default value given in A.7.3.2.5 shall only be used when an effective antifouling system is in place or systematic cleaning is to be performed.  A.10.5.2.2.2 and Table A.10.4-1 The damping should be based on measured values from the actual jack-up, or from jack-ups with similar spudcans, foundation and leg to hull connection system. If measurements do not exist, a damping of 2 % to 4 % should be used for FLS analysis. Specific evaluations can be needed to justify the values adopted.  A.12.2.2 The maximum value of the yield strength used in the analyses should not be greater than the ultimate tensile strength divided by 1,2. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 348 © ISO 2023 – All rights reserved  A.12.5 and A.12.6 The partial resistance factors should be increased by a factor of at least 1,05.  Annex B Several of the partial factors are replaced by the factors given above. H.2.3 Technical requirements for jack-up rigs operating close to a permanent occupied installation H.2.3.1 Introduction For jack-up rigs operating close to a permanent occupied installation, the following additional requirements shall apply to document acceptable hazard from the jack-up to the permanent installation, and thereby also ensure compliance with authority regulations for the permanent installation. H.2.3.2 Dynamic response and structural analyses Jack-ups are in general susceptible to significant wave induced dynamic response and shall be assessed by means of time-domain simulations. a) Estimation of the dynamics, taking into account the following: 1) EDAF analysis in accordance with NORSOK N-003[9] utilizing second order surface elevation process, or alternatively using the TDAF recipe from DNV-RP-C104[64]; 2) total damping 4 %; 3) a reasonable soil stiffness interval to be investigated for dynamic analysis, as further detailed below; 4) verification of the fact that the design approach agrees with the degree of dynamic behaviour. b) Structural analysis: 1) Stokes 5th wave from the metocean design basis combined with wave period within the 90 % interval that gives the largest response. (or mean wave period ± 2 s); 2) kinematic reduction factor 0,95; 3) verification of the ALS (10 000 year environmental event). H.2.3.3 Advanced geotechnical analyses Advanced geotechnical analyses shall be performed in layered soils, for skirted jack-up spudcan foundations and when jack-up foundations interact with other foundations (e.g. jacket piles). It is critical in such cases that the following is documented through detailed analysis by a qualified geotechnical engineer: a) Bearing and sliding capacity, considering at least: 1) simultaneously acting vertical, horizontal loads and moments for the different load cases; 2) foundation capacity and safety margin with respect to the different failure modes; 3) cyclic loading and cyclic effects; 4) additional settlements that may occur. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 349 f) Rotational stiffness considering both best and high estimate conditions using Finite Element Analysis or equivalent. Rotational stiffness sensitivity shall be documented for at least: 1) variations in foundation loading and the different load cases; 2) variation in soil parameters and soil models used; 3) drained and undrained conditions; 4) cyclic loading and cyclic effects. g) Skirt penetration, considering at least: 1) penetration resistance; 2) water evacuation during penetration and suitability of water evacuation system; 3) maximum landing velocity; 4) soil – base contact. h) Interaction between jack-up foundation and other foundations, where as a minimum the following should be presented: 1) soil displacements for the different load cases; 2) soil stresses affecting neighboring structures for the different load cases. Where applicable, spudcan interaction with existing footprints shall be assessed. H.2.3.4 Documentation Documentation shall in detail present methodology, input, results and discussion. If utilizations are found to be unacceptable, evacuation criteria shall be established based on the procedure described in NORSOK N-006[10]. H.2.4 Additional national requirements The regulations relating to health, environment and safety in the petroleum activities (the framework regulation), laid down by Royal Decree 31 August 2001 stipulates in § 3 that mobile facilities registered in a national register of shipping, and that follow a maritime operational concept, relevant technical requirements contained in rules and regulations of the Norwegian Maritime Directorate in the form following the 2007 regulations and later amendments, together with supplementary classification regulations issued by Det Norske Veritas, or international flag state rules with supplementary classification rules achieving the same level of safety, may be used as an alternative to technical requirements laid down in the facility regulation or pursuant to the Petroleum Act. Facilities not using the option in the framework regulation § 3 are subject to the Petroleum Safety Authority Norway: Regulations relating to design and outfitting of facilities, etc., in the petroleum activities (the facility regulation). Independent of flag state, the technical requirements in the Norwegian Maritime Directorate: Regulations of 4 September 1987, no. 856, concerning construction of mobile offshore units are valid for facilities using the option in the framework regulation § 3. Units used in Norway are also subject to the technical requirements of Det Norske Veritas standard DNV-OS-C104 (DNV 2022a)[63]. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 350 © ISO 2023 – All rights reserved H.3 US Gulf of Mexico H.3.1 Description of region The geographical extent of the region are the waters of the Gulf of Mexico that fall within the United States exclusive economic zone (EEZ), which is generally the portion of the Gulf of Mexico north of 26° N, as shown on Figures H.3-1 and H.3-2, and which includes the shallow water lease blocks shown on Figures H.3-2. H.3.2 Regulatory framework The U.S. Bureau of Safety and Environmental Enforcement (BSEE) and United States Coast Guard (USCG) have jurisdiction over the operations of MOUs on the U.S. Outer Continental Shelf. Supplementing its regulations, BSEE has issued requirements for the operation of jack-ups, including site assessments, in its “Notice to Lessees and Operators” (NTLs). The current BSEE regulations and NTLs for site assessment should be consulted when applying this document, including this clause. Figure H.3-1 — Northern Gulf of Mexico — Outer continental-shelf and deep water US lease areas[37] Key 1 South Padre Island 17 West Cameron South 33 Grand Isle 2 South Padre Island East 18 West Cameron 34 Grand Isle 3 North Padre Island 19 East Cameron 35 West Delta 4 North Padre Island East 20 East Cameron South 36 West Delta South 5 Mustang Island 21 Vermilion 37 South Pass South & East . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 351 6 Mustang Island East 22 Vermilion South 38 South Pass 7 Matagorda Island 23 South Marsh Island North 39 Breton Sound 8 Brazos 24 South Marsh Island 40 Main Pass 9 Brazos South 25 South Marsh Island South 41 Main Pass South & East 10 Galveston 26 Eugene Island 42 Chandeleur 11 Galveston South 27 Eugene Island South 43 Chandeleur East 12 High Island 28 Ship Shoal 44 Bay Marchand 13 High Island South 29 Ship Shoal South 45 Sabine Pass (TX) 14 High Island East South 30 South Pelto 46 Sabine Pass (LA) 15 High Island East 31 South Timbalier 16 West Cameron West 32 South Timbalier South Figure H.3-2 — Northern Gulf of Mexico: Inner continental-shelf US lease areas[37] H.3.3 Metocean conditions H.3.3.1 General The climate in the northern Gulf of Mexico ranges from tropical to temperate. Summer wind and wave conditions are generally benign, with warm temperatures and high relative humidity. There are occasional squalls and thunderstorms. The extreme wind and wave climate in the Gulf is dominated by hurricanes in the summer season and the passage of non-tropical frontal systems in the winter season. Swell is not a major factor except when associated with a hurricane. Waves tend to be correlated with winds (either hurricane or winter storm) and temporarily strong currents can be associated with storm systems, although there are also prevailing circulation currents even in the shallow Gulf. The hurricane season officially runs from the beginning of June to the end of November, and on average three tropical storms can be expected to form in or enter the region each year. These storms can originate in the Gulf of Mexico, the Caribbean Sea or in the North Atlantic Ocean. The National Hurricane Center monitors the gestation and development of all tropical disturbances in the Atlantic region. Information is released to the public on the formation, development, the expected track and speed and wind speeds. Other public and private organizations develop forecast metocean conditions from these data. Government bodies, operators and jack-up owners can use these data to plan for the evacuation of offshore personnel. This also allows the operators and owners time to prepare jack-ups for the storm event prior to evacuation. The standard practice is to evacuate all personnel in the predicted direct or indirect path of the storm prior to the arrival of severe weather. The exception to this situation is when a sudden TRS forms within the Gulf (sudden hurricane). In this case, it might not be possible to evacuate personnel; however, historical metocean data indicates that tropical storms or hurricanes that develop within the Gulf are less severe than the major hurricanes that develop in the Atlantic basin and migrate into the Gulf. Even in the case of a sudden hurricane, there is normally sufficient time to make safe the well and prepare the jack-up for severe weather. H.3.3.2 Metocean conditions and their assessment H.3.3.2.1 General An L1 jack-up shall be assessed to metocean data applicable to the season of operation using either the independent 50 year extreme with a partial action factor of 1,15 or the 100 year joint probability metocean data with a partial action factor of 1,25. An L2 jack-up shall be assessed to L1 criteria using the 50 year independent extremes or 100 year joint probability data for hurricanes that can reach the site prior to evacuation being completed. API RP-2MET, 2019, provides 50 year sudden hurricane data for the northern Gulf of Mexico. Relevant data and criteria are given in H.3.3.2.2 and H.3.3.2.3. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 352 © ISO 2023 – All rights reserved An L2 jack-up shall also be assessed as unoccupied unit for the post evacuation case (see H.3.3.2.4). Other requirements for the hurricane season are given in H.3.3.3. An L3 jack-up shall be assessed to criteria agreed between the jack-up owner and the operator. H.3.3.2.2 Hull elevation during hurricane season In accordance with 5.4.5 and 13.6, the assessor shall consider the possibility of wave impingement on the hull. The hull elevation shall be appropriate for the water depth, spring tide, and the expected maximum wave crest height and storm surge due to the 100 year return period hurricane. The hull elevation shall also include an allowance for any settlement predicted by the post evacuation assessment. In the absence of a site-specific hull elevation assessment, the curve given in Figure H.3-3 may be used. Key X water depth, expressed in metres Y minimum recommended hull elevation above LAT, expressed in metres Figure H.3-3 — Recommended hull elevation above LAT for hurricane season H.3.3.2.3 Sudden hurricane case When it can be demonstrated that the jack-up can be placed in storm survival mode and evacuation effected within 24 h to 48 h (see 5.5.1, 5.5.2, 5.5.4, A.6.4.1), the jack-up shall be assessed to the 50 year return period sudden hurricane conditions defined in API RP-2MET[15] using the action and resistance factors given in this document, as summarized in Annex B. When an effective evacuation cannot be accomplished within 24 h to 48 h, 50 year return period site-specific metocean data shall be used for the necessary longer evacuation time. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) © ISO 2023 – All rights reserved 353 50 year return period sudden hurricane metocean data are given in API RP-2MET[15]. The significant wave height should be taken as Hmax/1,75. The wave periods given in API RP-2MET[15] should be considered with a ±0,5 second range unless a more detailed study indicates otherwise. H.3.3.2.4 Unoccupied post-evacuation case In accordance with 5.5.4, the jack-up shall also be considered for the unoccupied post-evacuation case. The assessment shall proceed using one of the following metocean conditions developed using the methodology set out in API RP-2MET[15]. Metocean conditions may consider, for example, joint probability of metocean parameter occurrence, seasonal data, operating site, duration of operations with contingency, etc. Metocean conditions that satisfy the requirements of this clause (in decreasing order of severity) include the following: a) 50 year full population hurricane for the central zone, as set out in API RP-2MET[15]. b) 50 year full population hurricane for the zone in which the unit is operating, as set out in API RP-2MET[15]. c) 2 500 year sudden hurricane, as set out in API RP-2MET[15]. d) 50 year full population hurricane using metocean data developed for the specific site. NOTE The intent of the unoccupied, post-evacuation assessment is to demonstrate that the jack-up will survive the storm with no critical damage, and foundation settlement is limited such that wave impingement on the hull and leaning instability are precluded. Two methods of analysis that can be used are as follows: 1) Elastic analysis: Perform an assessment to the ULS requirements of this document, but with the action and resistance factors set to 1,0. 3) Plastic collapse (pushover) analysis: Create load cases for the environmental conditions selected for the post evacuation assessment using the calculation methodology in this document. The component strength checks are replaced by a system strength check based on plastic collapse techniques; see 10.9. The effect of additional settlement shall be included. For post evacuation analyses described above, the added P-Δ effect due to leg settlement shall be considered and a Step 3 displacement check shall be performed for the foundations. H.3.3.3 Other requirements H.3.3.3.1 Preloading The maximum feasible preload reaction should normally be applied. This can require individual leg preloading, which is, in general, recommended. NOTE The shape of the hazard curve in TRS areas is such that there can be a significant increase in actions for a small increase in return period. Jack-ups that experienced a major hurricane event often had increased spudcan penetration(s). In some cases they survived without damage, in other cases the resulting hull inclination exceeded the capability of the leg(s) and they either remained on location with damage or collapsed. In the latter case the hull ended up in the water and often drifted away from the location. Therefore, where the soil characteristics and strength considerations permit, it is beneficial to increase preload over the MOM values since this provides additional fixity and foundation capacity. Whether or not increased preload is feasible, the load-penetration curve can be evaluated for the consequences of such significant increases in the storm actions. . No further reproduction or distribution permitted. Printed / viewed by: @ 2024-08 ISO 19905-1:2023(E) 354 © ISO 2023 – All rights reserved The preload shall be applied and held for a reasonable period after penetration has ceased. Frequently the holding period is from one hour to two hours for a typical Gulf of Mexico site. This guidance should be tempered with knowledge of the soils at the site. For instance, where punch-through potential exists, holding times should be increased. H.3.3.3.2 Storm preparation The evacuation plan describes the tasks to place the jack-up in survival mode prior to evacuation as described in the Marine Operations Manual (MOM) or supplementary studies. The plan should include those discretionary well operational tasks such as completing the drilling of a particular well section, running casing or similar operations which can lengthen the time required to secure the well, place the jack-up in survival mode and evacuate rig personnel. Where required by the MOM, the drill and cantilever packages shall be skidded to a storm position. Where possible the jack-up can be lowered as far as possible towards the minimum safe hull elevation according to Figure H.3-3 with the lower-guide located at an optimal position. Consideration should also be given to changing the hull elevation so that the potential for impingement on adjacent structures is reduced (see 5.4.7 and 13.10). The conductor support requirements should not normally impede the placing of the jack-up into survival mode when this is prescribed by the MOM or other site-specific requirements. However, if the operator requires that the conductor is to remain supported during a storm, the resulting loads effect on the jack-up shall be considered in the assessment.