Guidance Note for the Classification of

Self-Elevating Units

September 2010

Guidance Note NI 534 DT R00 E

Marine Division 92571 Neuilly sur Seine Cedex France

Tel: + 33 (0)1 55 24 70 00 Fax: + 33 (0)1 55 24 70 25 Marine website: http://www.veristar.com Email: veristarinfo@bureauveritas.com

2010 Bureau Veritas - All rights reserved

ARTICLE 1

1.1. - BUREAU VERITAS is a Society the purpose of whose Marine Division (the "Society") is the classi-fication (" Classification ") of any ship or vessel or structure of any type or part of it or system therein col-lectively hereinafter referred to as a "Unit" whether linked to shore, river bed or sea bed or not, whetheroperated or located at sea or in inland waters or partly on land, including submarines, hovercrafts, drillingrigs, offshore installations of any type and of any purpose, their related and ancillary equipment, subseaor not, such as well head and pipelines, mooring legs and mooring points or otherwise as decided by theSociety.

The Society: prepares and publishes Rules for classification, Guidance Notes and other documents (Rules); issues Certificates, Attestations and Reports following its interventions (Certificates); publishes Registers.

1.2. - The Society also participates in the application of National and International Regulations or Stand-ards, in particular by delegation from different Governments. Those activities are hereafter collectively re-ferred to as " Certification ".1.3. - The Society can also provide services related to Classification and Certification such as ship andcompany safety management certification; ship and port security certification, training activities; all activi-ties and duties incidental thereto such as documentation on any supporting means, software, instrumen-tation, measurements, tests and trials on board.

1.4. - The interventions mentioned in 1.1., 1.2. and 1.3. are referred to as " Services ". The party and/or itsrepresentative requesting the services is hereinafter referred to as the " Client ". The Services are pre-pared and carried out on the assumption that the Clients are aware of the International Maritimeand/or Offshore Industry (the "Industry") practices.1.5. - The Society is neither and may not be considered as an Underwriter, Broker in ship's sale or char-tering, Expert in Unit's valuation, Consulting Engineer, Controller, Naval Architect, Manufacturer, Ship-builder, Repair yard, Charterer or Shipowner who are not relieved of any of their expressed or impliedobligations by the interventions of the Society.

ARTICLE 22.1. - Classification is the appraisement given by the Society for its Client, at a certain date, following sur-veys by its Surveyors along the lines specified in Articles 3 and 4 hereafter on the level of compliance ofa Unit to its Rules or part of them. This appraisement is represented by a class entered on the Certificatesand periodically transcribed in the Society's Register.

2.2. - Certification is carried out by the Society along the same lines as set out in Articles 3 and 4 hereafterand with reference to the applicable National and International Regulations or Standards.

2.3. - It is incumbent upon the Client to maintain the condition of the Unit after surveys, to presentthe Unit for surveys and to inform the Society without delay of circumstances which may affect thegiven appraisement or cause to modify its scope.2.4. - The Client is to give to the Society all access and information necessary for the safe and efficientperformance of the requested Services. The Client is the sole responsible for the conditions of presenta-tion of the Unit for tests, trials and surveys and the conditions under which tests and trials are carried out.

ARTICLE 33.1. - The Rules, procedures and instructions of the Society take into account at the date of theirpreparation the state of currently available and proven technical knowledge of the Industry. Theyare not a standard or a code of construction neither a guide for maintenance, a safety handbookor a guide of professional practices, all of which are assumed to be known in detail and carefullyfollowed at all times by the Client.Committees consisting of personalities from the Industry contribute to the development of those docu-ments.3.2. - The Society only is qualified to apply its Rules and to interpret them. Any reference to themhas no effect unless it involves the Society's intervention.3.3. - The Services of the Society are carried out by professional Surveyors according to the applicableRules and to the Code of Ethics of the Society. Surveyors have authority to decide locally on matters re-lated to classification and certification of the Units, unless the Rules provide otherwise.

3.4. - The operations of the Society in providing its Services are exclusively conducted by way ofrandom inspections and do not in any circumstances involve monitoring or exhaustive verifica-tion.

ARTICLE 4

4.1. - The Society, acting by reference to its Rules: reviews the construction arrangements of the Units as shown on the documents presented by the Cli-

ent; conducts surveys at the place of their construction; classes Units and enters their class in its Register; surveys periodically the Units in service to note that the requirements for the maintenance of class are

met.

The Client is to inform the Society without delay of circumstances which may cause the date or theextent of the surveys to be changed.

ARTICLE 55.1. - The Society acts as a provider of services. This cannot be construed as an obligation bearingon the Society to obtain a result or as a warranty.5.2. - The certificates issued by the Society pursuant to 5.1. here above are a statement on the levelof compliance of the Unit to its Rules or to the documents of reference for the Services providedfor.In particular, the Society does not engage in any work relating to the design, building, productionor repair checks, neither in the operation of the Units or in their trade, neither in any advisory serv-ices, and cannot be held liable on those accounts. Its certificates cannot be construed as an im-plied or express warranty of safety, fitness for the purpose, seaworthiness of the Unit or of its valuefor sale, insurance or chartering.5.3. - The Society does not declare the acceptance or commissioning of a Unit, nor of its construc-tion in conformity with its design, that being the exclusive responsibility of its owner or builder,respectively.

5.4. - The Services of the Society cannot create any obligation bearing on the Society or constitute anywarranty of proper operation, beyond any representation set forth in the Rules, of any Unit, equipment ormachinery, computer software of any sort or other comparable concepts that has been subject to any sur-vey by the Society.

ARTICLE 66.1. - The Society accepts no responsibility for the use of information related to its Services which was notprovided for the purpose by the Society or with its assistance.

6.2. - If the Services of the Society cause to the Client a damage which is proved to be the directand reasonably foreseeable consequence of an error or omission of the Society, its liability to-wards the Client is limited to ten times the amount of fee paid for the Service having caused thedamage, provided however that this limit shall be subject to a minimum of eight thousand (8,000)Euro, and to a maximum which is the greater of eight hundred thousand (800,000) Euro and oneand a half times the above mentioned fee.The Society bears no liability for indirect or consequential loss such as e.g. loss of revenue, lossof profit, loss of production, loss relative to other contracts and indemnities for termination of oth-er agreements.6.3. - All claims are to be presented to the Society in writing within three months of the date when the Serv-ices were supplied or (if later) the date when the events which are relied on of were first known to the Client,and any claim which is not so presented shall be deemed waived and absolutely barred. Time is to be in-terrupted thereafter with the same periodicity.

ARTICLE 77.1. - Requests for Services are to be in writing.7.2. - Either the Client or the Society can terminate as of right the requested Services after givingthe other party thirty days' written notice, for convenience, and without prejudice to the provisionsin Article 8 hereunder. 7.3. - The class granted to the concerned Units and the previously issued certificates remain valid until thedate of effect of the notice issued according to 7.2. here above subject to compliance with 2.3. here aboveand Article 8 hereunder.

7.4. - The contract for classification and/or certification of a Unit cannot be transferred neither assigned.

ARTICLE 88.1. - The Services of the Society, whether completed or not, involve, for the part carried out, the paymentof fee upon receipt of the invoice and the reimbursement of the expenses incurred.

8.2. Overdue amounts are increased as of right by interest in accordance with the applicable leg-islation.8.3. - The class of a Unit may be suspended in the event of non-payment of fee after a first unfruitfulnotification to pay.

ARTICLE 9

9.1. - The documents and data provided to or prepared by the Society for its Services, and the informationavailable to the Society, are treated as confidential. However: clients have access to the data they have provided to the Society and, during the period of classifica-

tion of the Unit for them, to the classification file consisting of survey reports and certificates whichhave been prepared at any time by the Society for the classification of the Unit;

copy of the documents made available for the classification of the Unit and of available survey reportscan be handed over to another Classification Society, where appropriate, in case of the Unit's transferof class;

the data relative to the evolution of the Register, to the class suspension and to the survey status of theUnits, as well as general technical information related to hull and equipment damages, are passed onto IACS (International Association of Classification Societies) according to the association workingrules;

the certificates, documents and information relative to the Units classed with the Society may bereviewed during certificating bodies audits and are disclosed upon order of the concerned governmen-tal or inter-governmental authorities or of a Court having jurisdiction.

The documents and data are subject to a file management plan.

ARTICLE 1010.1. - Any delay or shortcoming in the performance of its Services by the Society arising from an eventnot reasonably foreseeable by or beyond the control of the Society shall be deemed not to be a breach ofcontract.

ARTICLE 1111.1. - In case of diverging opinions during surveys between the Client and the Society's surveyor, the So-ciety may designate another of its surveyors at the request of the Client.

11.2. - Disagreements of a technical nature between the Client and the Society can be submitted by theSociety to the advice of its Marine Advisory Committee.

ARTICLE 1212.1. - Disputes over the Services carried out by delegation of Governments are assessed within theframework of the applicable agreements with the States, international Conventions and national rules.

12.2. - Disputes arising out of the payment of the Society's invoices by the Client are submitted to the Courtof Nanterre, France.

12.3. - Other disputes over the present General Conditions or over the Services of the Society areexclusively submitted to arbitration, by three arbitrators, in London according to the ArbitrationAct 1996 or any statutory modification or re-enactment thereof. The contract between the Societyand the Client shall be governed by English law.

ARTICLE 1313.1. - These General Conditions constitute the sole contractual obligations binding together theSociety and the Client, to the exclusion of all other representation, statements, terms, conditionswhether express or implied. They may be varied in writing by mutual agreement.13.2. - The invalidity of one or more stipulations of the present General Conditions does not affect the va-lidity of the remaining provisions.

13.3. - The definitions herein take precedence over any definitions serving the same purpose which mayappear in other documents issued by the Society.

BV Mod. Ad. ME 545 k - 17 December 2008

MARINE DIVISION

GENERAL CONDITIONS

GUIDANCE NOTE NI 534

NI 534Guidance Note for the Classification of

Self-Elevating Units

SECTION 1 GENERAL

SECTION 2 STRUCTURE DESIGN PRINCIPLES

SECTION 3 DESIGN CONDITIONS

SECTION 4 ENVIRONMENTAL CONDITIONS

SECTION 5 ANALYSIS IN ELEVATED POSITION

SECTION 6 ANALYSIS IN TRANSIT CONDITIONS

SECTION 7 STRENGTH OF LEGS

SECTION 8 EQUIPMENTS, APPURTENANCES AND OUTFITTINGS

SECTION 9 CONSTRUCTION SURVEY - WELDING - TESTS AND TRIALSSeptember 2010

APPENDIX 1 HYDRODYNAMIC ANALYSIS OF SELF-ELEVATING UNITS INFLOATING CONDITION

Section 1 General1 Scope 9

1.1 Application

2 Definitions 92.1 Self-elevating unit2.2 Modes of operation2.3 Water depth, water levels and crest elevation2.4 Configuration of a self-elevating unit in elevated position2.5 Configuration of a self-elevating unit in floating position

3 Classification requirements 103.1 General provision3.2 Ship and offshore rules3.3 Classification limits3.4 Classification restrictions3.5 Design Criteria Statement3.6 Design life3.7 Operating Manual

4 Statutory requirements 124.1 General4.2 Project specification4.3 Conflict of Rules

5 Classification notations 125.1 Class symbol, construction mark and notations5.2 Elevating system

6 Required documentation 136.1 General

7 Rule application 147.1 Structure7.2 Stability7.3 Other subjects

8 Maintenance of class 158.1 General

9 Reference co-ordinate system 159.1 Hull

Section 2 Structure Design Principles1 Steel grade and structural categories 16

1.1 Material strength1.2 Steel grade selection1.3 Structural categories1.4 Steels with specified through thickness properties1.5 Corrosion allowances2 Bureau Veritas September 2010

2 Structural principles 172.1 Accessibility for inspection during service2.2 General construction2.3 Plating2.4 Ordinary stiffeners2.5 Primary supporting members2.6 Leghouse2.7 Legs2.8 Spudcans and bottom mat2.9 Deckhouses and superstructures2.10 Reinforcements in way of supporting structures for hull attachments

Section 3 Design Conditions1 General 21

1.1 Definition1.2 Modes of operation and accidental conditions

2 Self-elevating unit in elevated condition 212.1 Calculation methodology2.2 Loading conditions

3 Self-elevating unit in transit conditions 223.1 Design considerations for hull structure3.2 Design considerations for legs and hull / legs connection3.3 Dry tow transit

4 Installation / retrieval design conditions 234.1 Leg impact

Section 4 Environmental Conditions1 General 24

1.1 Application1.2 References1.3 Environmental data1.4 Environmental load1.5 Documentation to be submitted

2 Waves 252.1 General2.2 Design wave approach2.3 Random / stochastic wave approach

3 Wind 253.1 Wind specification

4 Current 264.1 Current specification

5 Waterdepth and tides 265.1 Waterdepth and tide specificationSeptember 2010 Bureau Veritas 3

6 Design temperatures 266.1 Air temperature6.2 Water temperature

7 Marine growth 267.1 Marine growth specification

8 Soil 268.1 General

Section 5 Analysis in Elevated Position1 General 27

1.1 Application1.2 Reference1.3 Calculation procedures1.4 Definitions

2 Structural modelling 272.1 General2.2 Hull modelling2.3 Leg modelling2.4 Leg / hull connection modelling2.5 Boundary conditions

3 Hydrodynamic modelling 283.1 Marine growth3.2 Drag and inertia coefficients

4 Loads and load effects 294.1 Fixed and operational loads4.2 Leg inclination4.3 Wind loads4.4 Hydrodynamic loads4.5 Dynamic amplification loads4.6 P and Euler effect

5 Loading conditions and load combinations 335.1 Loading conditions5.2 Load cases5.3 Loads combination

6 Resistance check 346.1 Air gap6.2 Leg length reserve6.3 Overturning stability6.4 Structural strength in elevated position6.5 Fatigue analysis

Section 6 Analysis in Transit Conditions1 General 39

1.1 Application1.2 Material4 Bureau Veritas September 2010

2 Stability 402.1 General

3 Loads application in transit condition 403.1 General3.2 Forces and moments for leg examination3.3 Forces and moments for hull / leg

connection examination3.4 Sea and internal pressure loads

4 Loads application in installation condition 434.1 General4.2 Forces and moments for leg examination4.3 Forces and moments for hull / leg

connection examination

5 Structure elements to be checked 445.1 General5.2 Legs structure5.3 Leg / hull connections5.4 Hull structure

6 Hull scantling 446.1 General6.2 Platings6.3 Ordinary stiffeners6.4 Primary members6.5 Reinforcement of the flat bottom forward area6.6 Superstructures and deckhouses

Section 7 Strength of Legs

1 General 461.1 Subject1.2 References1.3 Stress factor1.4 Convention

2 Cylindrical and rectangular hollow section legs 472.1 General2.2 Yielding2.3 Overall buckling2.4 Curve shell plating of cylindrical legs2.5 Plate shell plating of rectangular hollow section legs2.6 Ordinary stiffeners subject to lateral pressure and axial compressive stress2.7 Horizontal ring stringers of cylindrical legs

3 Lattice legs 503.1 Methodology3.2 Actual stresses for chords and bracings3.3 Allowable stresses for chords and bracings3.4 Checking criteria for chords and bracingsSeptember 2010 Bureau Veritas 5

4 Additional local analysis 534.1 General4.2 Stress criteria4.3 Fatigue4.4 Spudcans and bottom mat4.5 Local punching

Section 8 Equipments, Appurtenances and Outfittings1 Supports for hull attachments and appurtenances 55

1.1 General1.2 Structural strength1.3 Calculations

2 Crane connections 552.1 Rules to be applied

3 Superstructures and deckhouses 553.1 General

4 Helicopter deck 564.1 Reference standards4.2 Structure

5 Hull outfitting 565.1 Bulwarks and guard rails

6 Launching appliances 566.1 Launching appliances used for survival craft or rescue boat

7 Equipment 567.1 General7.2 Towing equipment

Section 9 Construction Survey - Welding - Tests and Trials1 Construction survey 57

1.1 General

2 Welding and weld connections 572.1 Reference2.2 General2.3 Weld category2.4 Weld types2.5 Post welded treatment2.6 Hull2.7 Other structures

3 Tests and trials 583.1 Strength and watertightness testing3.2 Jacking systems3.3 Preloading test6 Bureau Veritas September 2010

Appendix 1 Hydrodynamic Analysis of Self-Elevating Units in FloatingCondition

1 General 591.1 Principle

2 Modelling principles 592.1 Environmental data2.2 Hydrodynamic model2.3 Loading conditions2.4 Sensitivity analysis

3 Unit response 593.1 Response amplitude operators3.2 Hull girder loads, motions and

accelerationsSeptember 2010 Bureau Veritas 7

SymbolsE : Young modulus, in N/mm2, to be taken equal to

2,06 105 N/mm2 for steelRf : Reference stress of the material, in N/mm2, as

defined in Sec 2, [1.1.1]

l : Span of the leg, in m, defined as follows: hull in elevated position: length of the leg

between the bottom of the spudcan andeither the lower guide or the center of thelocking mechanism if any

transit condition: length of the leg betweenthe upper guide and the top of the leg

installation condition (leg impact): length ofthe leg from the bottom of the spudcan tothe lower guide

A : Cross-sectional area of the leg, in cm2. Formu-lae given in Sec 2, Tab 2 may be applied if rele-vant

I : Minimum moment of inertia of the leg, in cm4,about its principal axis. Formulae given inSec 2, Tab 2 may be applied if relevant

s : Spacing of ordinary stiffeners or length of theshorter side of the plate panel, in m

ls : Span, in m, of ordinary stiffeners, measuredbetween the supporting members

Hmax : Maximum wave height, in mTass : Associated period to Hmax , in s

g : Gravity acceleration taken equal to 9,81 m/s2.8 Bureau Veritas September 2010

NI 534, Sec 1SECTION 1 GENERAL

1 Scope

1.1 Application

1.1.1 The present Guidance Note gives requirements andrecommendations to be considered for the classificationand/or certification activities regarding the offshore self-ele-vating or jack-up units, as defined in [2.1].

The requirements of the present Note are complementary toprovisions of NR445 Rules for the Classification of OffshoreUnits, which remain applicable, except where otherwisespecified.

The present Guidance Note applies from small structuresoperating in shallow water to large structures operating indeep water.

The present Guidance Note is applicable to the design andconstruction of newbuilt units and to reassessment and con-version work of an existing unit.

2 Definitions

2.1 Self-elevating unit

2.1.1 A self-elevating unit is a unit with a floating hull fittedwith legs capable of being lowered to the sea bed and ofraising the hull above the sea level (see Fig 1).

The hull is to have sufficient buoyancy to safely move theunit from one location to another.

The legs may be of a shell or truss type. The legs may beequipped with a lower mat, a gravity based structure or withfootings designed to penetrate the sea bed.

The legs may be vertical or slanted.

2.2 Modes of operation

2.2.1 A self-elevating unit is to be designed to resist loadsthat may occur during all stages of the life-cycle of the unitsuch as working, survival, transit, installation and retrievalmode.

a) Working mode:

The unit is on location supported on the sea bed foroperating, and combined environmental and opera-tional loading are within the appropriate design limitsestablished for such operations

b) Survival mode:

The unit is on location supported on the sea bed andmay be subject to the most severe environmental load-ing for which the unit is designed. Operations for whichthe unit has been designed such as drilling, well servic-ing, installation may have been interrupted due to theseverity of the environmental loadings

c) Transit mode:

The unit moves from one location to another within theappropriate design limits established for such operations

The transit mode includes short duration field moves,between locations in close proximity, and ocean transit,for which a specific preparation of the unit is generallyneeded

The unit may be self-floating or supported by a transpor-tation barge or ship during ocean tow

d) Installation mode:

Period during which the unit is firstly lowering legs tothe sea bed, secondly elevating hull at the required ele-vation above the sea level, and pre-loading the legs tothe extreme loading

e) Retrieval mode:

Period during which the unit is lowering the hull andelevating legs to be in transit mode.

2.3 Water depth, water levels and crestelevation

2.3.1 The reference water levels and crest elevation aredefined as follows in the present Guidance Note (see alsoFig 1):

the Mean Water Level (MWL) is defined as the meanlevel between the Highest Astronomical Tide (HAT) andthe Lowest Astronomical Tide (LAT)

the astronomical tidal range is defined as the rangebetween the Highest Astronomical Tide (HAT) and theLowest Astronomical Tide (LAT)

the maximum Still Water Level (SWL) is defined as thelevel at the Highest Astronomical Tide (HAT) includingstorm surge

the crest elevation is defined as the height of wave crestabove the Still Water Level (SWL).

2.3.2 Except otherwise specified, the reference waterdepth, to be considered, is the distance between the seabed and the maximum SWL.

2.4 Configuration of a self-elevating unit inelevated position

2.4.1 The configuration of the self-elevating unit is to bedefined based on site data associated to the unit servicesuch as drilling geotechnical or work-over, assistance, lift-ing, accommodation

2.4.2 The configuration is defined with the followingparameters (see also Fig 1):September 2010 Bureau Veritas 9

NI 534, Sec 1Figure 1 : Definition of sea levels, clearance and air gap

a) Leg length penetration:

The leg length penetration is the maximum leg penetra-tion into sea bed including spudcans

b) Leg length reserve:

The leg length reserve is the reserve above upper guideto avoid any soil settlement or punch through and toprovide a contingency in case the penetrations exceedthat predicted

c) Air gap:

The air gap is defined as the distance between theunderside of the hull and the LAT

d) Clearance:

The wave crest clearance is defined as the distancebetween the highest wave crest and the underside of thehull.

2.5 Configuration of a self-elevating unit infloating position

2.5.1 In floating position the legs are usually elevated andsupported in the hull.

The draft is defined as the distance from the lowest point ofthe bottom leg, or spudcan if any, to the waterline.

3 Classification requirements

3.1 General provision

3.1.1 The general provision of Part A, Chapter 1 of theRules for the Classification of Offshore Units, where theprincipal conditions and other aspect of the classificationprocess are defined, are applicable.

3.2 Ship and offshore rules

3.2.1 When reference is made to the Ship Rules, the latestversion of NR467 Rules for the Classification of SteelShips is applicable.

When reference is made to the Offshore Rules, the latestversion of NR445 Rules for the Classification of OffshoreUnits is applicable.

Wave crestclearance

Wave crest

Airgap

Leg penetration

Max Still Water Level (SWL)Highest Astronomical Tide (HAT)Mean Water Level (MWL)Lowest Astronomical Tide (LAT)

Jackhouse

Hull

Leg

Sea bed

Spudcan

Bracings

Chord

Storm Surge10 Bureau Veritas September 2010

NI 534, Sec 13.3 Classification limits

3.3.1 Site conditionsIt is incumbent to the owners/operators:

to perform the necessary investigations, including envi-ronmental and geotechnical surveys, prior to operatingthe unit at a given site

to ascertain that the actual conditions met at the con-templated operating site remain on the safety side whencompared to design data and assumptions (particularlythose listed in the Design Criteria Statement). Such siteassessment is not part of the classification.

Classification does not cover the following item:

the assessment of sea bottom conditions and geotechni-cal investigations

the prediction of footing penetration during pre-loading

the jack-up foundation stability after pre-loading

the assessment of the possible sea floor movement.

3.3.2 Operating proceduresClassification does not cover the procedures to be used forthe unit's positioning, leg lowering and jacking, preloading,jetting and other related to operations.

It is the responsibility of the owner, or the operator if distinctfrom the owner, to ascertain that the said procedures andtheir implementation satisfy the design criteria of the unitand the design of the related equipment.

For other classification limits applicable to operating proce-dures, refer to Part B, Chapter 2 of the Offshore Rules.

3.3.3 Hull attachments and appurtenancesThe class limit for the review of the supports of appurte-nances is defined as follows:

for classed equipments, the whole structure supportingthe equipments is included in the scope of classificationand subject to the requirements of Sec 8, [1]

for non-classed equipments, the scope of review is lim-ited, in principle, to the review of the hull attachmentand the affected supporting structure to any non-weldedconnection of the equipment (pinned, bolted connec-tion, sliding support ...). For appurtenances welded onthe hull, the scope of class is defined on a case by casebasis but remains limited to the connection with hullonly.

3.4 Classification restrictions

3.4.1 When the design data and assumptions specified bythe party applying for classification do not comply with theapplicable Rules requirements, restrictions may be placedupon the unit's class.

3.4.2 When deemed necessary, restrictions may be placedon the duration of the service life of the unit.

3.4.3 Class restrictions, if any, will be entered as a Memo-randa on the unit's Certificates of Classification and are tobe incorporated in the Operating Manual (see Pt A, Ch 1,Sec 4, [2.4] of the Offshore Rules).

3.5 Design Criteria Statement

3.5.1 GeneralClassification is based upon the design data or assumptionsspecified by the party applying for classification.

A Design Criteria Statement is to list the service(s) per-formed by the unit and the design conditions and otherassumptions on the basis of which class is assigned to theunit.

The Design Criteria Statement is issued by the Society,based on information provided by the party applying forclassification.

The Design Criteria Statement is to be referred to on theunit's Classification Certificates.

The Design Criteria Statement is to be incorporated in theOperating Manual as prescribed in Pt A, Ch 1, Sec 1, [3.4.]of the Offshore Rules.

3.5.2 Units activitiesThe Design Criteria Statement is to list the main services forwhich the unit is designed, the service notation and othernotations assigned to the unit.

The nature of the units activity is to be duly accounted forin the application of the Offshore Rules, as far as classifica-tion is concerned.

3.5.3 Structural design criteriaThe Design Criteria Statement is to list the necessary datapertaining to the structural design of the unit for the differ-ent conditions of operation of the unit, according to provi-sions of Part B, Chapter 2 of the Offshore Rules.

3.5.4 Machinery, electrical and other system designconditions

The party applying for classification is to submit the neces-sary description, diagrammatic plans, design data of all sys-tems, including those used solely for the service (drilling,lifting, etc.) performed by the unit and, where applicable,their cross connections with other systems. The submitteddata are to incorporate all information necessary to theassessment of the unit for the purpose of the assignment ofclass or for the assignment of additional class notations.

In accordance with Pt A, Ch 1, Sec 1, [4.8.2] of the Off-shore Rules, the party applying for classification is to givean estimation of electric balance for the different conditionsof operation of the unit. The specifications are to list allimportant equipment and apparatus, their rating and thepower factors, as applicable.

3.6 Design life

3.6.1 The requirements about Service life, Design life,unit modifications and unit re-assessment are given in Pt A,Ch 1, Sec 1, [1.7] of the Offshore Rules.September 2010 Bureau Veritas 11

NI 534, Sec 13.7 Operating Manual

3.7.1 An Operating Manual, which includes instructionsregarding the safe operation of the unit and of the systemsand equipment fitted on the unit, is to be placed on boardthe unit. The Operating Manual is to be, at all times, madeavailable to all concerned. A copy of the Operating Manualis to be retained ashore by the Owners of the unit or theirrepresentatives.

The Operating Manual is to incorporate a dedicated sectioncontaining all information relating to classification, particu-larly environmental, loading and other design criteria aswell as classification restrictions. The Operating Manual ofa self elevating unit is also to stipulate the instructionsrelated to transit conditions, preloading and the emergencyprocedures in case of punch through.

It is the responsibility of the party applying for classificationto prepare the contents of the Operating Manual.

3.7.2 The Operating Manual is to be submitted for reviewto the Society, this review being limited to checking that theclassification related material as listed above is consistentwith data given in the Design Criteria Statement defined in[3.5].

4 Statutory requirements

4.1 General

4.1.1 The classification of a unit does not relieve owners,designers, builders and other interested parties from com-pliance with any requirements issued by administration(international conventions, national laws and regulationsand other instruments).

4.1.2 The Society's activities do not cover the above men-tioned requirements.

4.1.3 When authorized by the administration concerned,the Society will act on its behalf within the limits of suchauthorization. In this respect, the Society will take intoaccount the relevant national requirements, survey the unit,report and issue or contribute to the issue of the corre-sponding certificates. (see Pt A Ch 1, Sec 1, [3.1.3.] of theOffshore Rules).

4.2 Project specification4.2.1 Prior to designing the unit, the complete list of Rules,Codes and Statutory requirements to be complied with is tobe established and submitted. This list is to detail therequirements to be complied with:

international conventions, (SOLAS,ILLC, MARPOL, ILOand IMO Assembly Resolutions)

flag state requirements

coastal state requirement

owner standards and procedures

industry standards

classification notations.

4.2.2 The project specification is also to specify the list ofowner requested certificates.

4.3 Conflict of Rules

4.3.1 In case of conflict between this Guidance Note andany Statutory Requirement as given by Flag State or CoastalState, the latter ones are to take precedence over therequirement of the present Guidance Note.

4.3.2 In case of conflict between owner or industry stand-ards and the present Guidance Note, the latter one is nor-mally to take precedence.

5 Classification notations

5.1 Class symbol, construction mark andnotations

5.1.1 The classification notations give the scope accordingto which the class of the units has been based and refer tothe specific rule requirements which are to be compliedwith for their assignment.

5.1.2 The types of classification assigned to a self-elevatingunit are described in Tab 1.

5.1.3 A site notation specifying the name of field and/or thegeographical area, where the unit is to operate, is to beassigned. When the self-elevating unit is not intended tooperate on a specific geographical area, the site notation isto be characterized by the most unfavorable sea conditionsfor the unit.

Whatever the site notation, the party applying for classifica-tion is to provide the most unfavorable environmental con-ditions for which the self-elevating is designed, as stipulatedin Sec 3. These conditions are to be reported in Design Cri-teria Statement.

All changes of the geographical area or stipulated environ-mental conditions are to be submitted to the Societysexamination and the site notation may be modified accord-ingly after approval of the design for the new conditions,and if applicable, execution of the necessary reinforce-ments.

5.1.4 The transit notation Transit - Specified criteria isassigned to units for which the transit is restricted to speci-fied environmental conditions as stipulated in the DesignCriteria Statement.

5.2 Elevating system

5.2.1 The structural type notation Offshore Self-elevatingunit lays down that the jacking mechanism for self-elevatingunits are to be approved by the Society as mentioned inPt C, Ch 1, Sec 11 of the Offshore Rules. It includes:

review of design, manufacturing and testing documents

witnessing of testing

visits during the manufacturing

inspection at suppliers works, as needed.12 Bureau Veritas September 2010

NI 534, Sec 1Table 1 : Classification notations for a self-elevating unit

5.2.2 The elevating systems are to be arranged with redun-dancy in order to avoid any uncontrolled descent of the unitand impair the possibility to jack the unit to a safe position.

5.2.3 Hydraulic system and electrical system associatedwith the elevating system are to comply with the relevantchapters in Part C of the Offshore Rules.

6 Required documentation

6.1 General

6.1.1 The required documentation is listed in Part A, Chap-ter 1 of the Offshore Rules.

6.1.2 The required documentations are to clearly show allessential features, arrangement and scantling of the struc-ture, machinery, boilers, auxiliaries and other equipmentcover by the classification.

6.1.3 In addition to what is specified in [6.1.1], the docu-mentation is to include the following information for planreview purposes:

a) Design data

Design condition data, as stipulated in Sec 3, includingenvironmental data (see Sec 4)

The data are to be as comprehensive as possible and toclearly give evidence of all applicable environmentalrestrictions:

maximum loading for all decks areas

results of model basin tests, when performed

results of wind tunnel tests, when performed

for equipment liable to induce, when in use, signifi-cant loads within the structure of the unit, all infor-mation on these loads, such as:

- drilling loads

- crane loads on pedestal and on boom and hookrests (lifting)

- other loads from lifting and handling equipment

b) Structural calculations

calculations of environmental loadings includingforces and moments from wind, waves, currents, ice,snow, earthquakes as applicable

calculations of loads induced by equipment

stability calculations for the intact and damaged con-ditions including detailed computation of windexposed areas and, if applicable, ice formation effects

global analysis in elevated position

calculations of the unit's resistance against overturn-ing while resting on the sea bed

hydrodynamic calculation in floating condition, ifrelevant

hull calculation in floating condition

leg strength calculation in floating condition

local strength calculations of legs, leg/hull connec-tion, hull attachments and appurtenances, ...

fatigue calculation of structural details

jacking systems (including locking system, if any)calculations

calculation of segregation of loads between jackingand locking system

calculations of cathodic protection system

Classification notations References

Class symbol I or II

Pt A, Ch 1, Sec 2 of the Offshore Rules

Construction mark

{, [ or to be separately assigned before: - HULL notation- MACH notation- additional class notation, when relevant

Structural type notation offshore self-elevating unit

Service notations

- drilling (geotechnical) or drilling (workover)- drilling assistance- lifting- production- accommodation- special service ( )

Site notation- name of field- geographical area of operation- most unfavorable sea conditions

Transit notation transit - specific criteria

Additional class notations / additional service features (may be optional)

- ALM (lifting appliance)- DYNAPOS (dynamic positioning)- AUTO (automation system)- HEL (Helideck)- ...September 2010 Bureau Veritas 13

NI 534, Sec 1c) Structural drawings

general arrangement plan (in elevating and towingconditions)

deck loading plans

main structural drawings showing structural arrange-ments, scantlings, grades of steel, welded connec-tions and structural details. These drawings are toinclude, as applicable:

- transverse and longitudinal sections of the hull

- decks including helicopter deck

- shell plating and framing

- bulkheads and flats

- legs including racks, chords, bracings and theirconnections for lattice legs, shell plating, stiffen-ers, stringers, struts, connections of racks withshell plate and supporting leg rack members,potential openings, for shell type legs

- detailed drawings of racks, if any, including theirarrangement in towing and elevating conditions

- footings (spudcans) and mats

- leghouses

- superstructures and deck houses

detailed structural drawings in the areas of connec-tions between main structural members in way of:

- foundations of elevating systems

- leghouse guides

- drilling derrick

- anchoring equipment

- crane foundations, and

- all other parts liable to be subject to high localloadings or stress concentrations

d) Operating Manual

As a minimum, the Operating Manual is to include thefollowing information, where applicable:

general description and principal particulars of theunit

general arrangement plan showing watertight com-partments, closures, vents, intakes and discharges,down flooding points

capacity plan showing the capacity, centre of gravityand free surface correction for each tank, fixed andvariable deck loads, permanent ballast, and thelocation of draught gauges and draught marks

loading manual

permissible loadings for all decks

amount of snow and ice allowable on deck

stability drawings including body plan, incliningexperiment results and allowable KG curves

amount of allowable marine growth

towing arrangements

temporary mooring and position anchoring arrange-ments

ballast control system drawings including pipingdiagram showing remote and manual controldevices

bilge system

hazardous areas drawings

fire bulkhead arrangement drawing

fire and gas drawings showing types and locations ofdetection and extinguishing equipment

schematic diagrams of main emergency power sup-plies and electrical installations

corrosion protection system including:

- in case of impressed current system, operatingmanual and detail of maintenance operations

- in case of sacrificial anodes: detail of mainte-nance/ retrofit operations

key as-built drawings

design limitations:

- on site

- during installation (leg lowering and preloading)

- for self-elevating unit removal (lowering the hull,leg retrieval)

- during transit (leg arrangement, rig and otherequipment sea fastening)

emergency procedures in case of punch through

Design Criteria Statement issued by the Society,including classification restrictions, if any

Classification Certificates, continuous survey listsand other certificates issued by the Society.

7 Rule application

7.1 Structure

7.1.1 The Sections of the present Guidance Note (and Off-shore Rules) are to be applied for the scantling and arrange-ment of unit items according to Tab 2.

Table 2 : Applicable Sectionsfor the scantling of unit items

ItemApplicable

Section / Article

Hull and legs structure

Sec 2 Sec 5 Sec 6 Sec 7

Hull attachment and appurtenances Sec 2

Sec 8, [1]

Superstructures and deckhouses Sec 8, [3]

Crane Sec 8, [2]

Helicopter decks Sec 8, [4]

Hull outfitting Sec 8, [5]

Launching appliances Sec 8, [6]

Jacking systemPt C, Ch 1, Sec 11

of the Offshore Rules14 Bureau Veritas September 2010

NI 534, Sec 17.2 Stability

7.2.1 Article Sec 6, [2] of the present Guidance Note is tobe applied for the stability assessment.

7.3 Other subjects7.3.1 Other subjects such as electricity, automation,machinery, piping and safety are dealt with the OffshoreRules.

8 Maintenance of class

8.1 General

8.1.1 Conditions for the maintenance of Class are definedin Part A, Chapter 2 of the Offshore Rules.

9 Reference co-ordinate system

9.1 Hull

9.1.1 Except specified otherwise, the units geometry andloads are defined with respect to the following right-handco-ordinate system:

Origin: at the intersection among the longitudinal planeof symmetry of unit, the aft end and the baseline

X axis: longitudinal axis, positive forwards

Y axis: transverse axis, positive towards portside

Z axis: vertical axis, positive upwards.

9.1.2 Positive rotations are oriented in anti-clockwisedirection about the X, Y and Z axes.September 2010 Bureau Veritas 15

NI 534, Sec 2SECTION 2 STRUCTURE DESIGN PRINCIPLES

1 Steel grade and structural categories

1.1 Material strength1.1.1 According to the Offshore Rules, the reference stressof material Rf , in N/mm2, to be considered for strength cal-culation is defined by:

where:ReG : Minimum specified yield stress of the material,

in N/mm2

R : Tensile strength of the material, in N/mm2.

1.1.2 For steel having a yield stress above 690 N/mm2, spe-cial consideration will be given by the society.

1.2 Steel grade selection1.2.1 The selected steels are to have mechanical propertiessatisfying the structural design of the unit and the require-ments of this Article.

1.2.2 The steel grade for a structural element is to beselected in accordance with Pt B, Ch 3, Sec 2 of the Off-shore Rules, on the basis of: the design service temperature defined in Sec 4, [6] the structural category set out in [1.3] the reference thickness of the element defined in Pt B,

Ch 3, Sec 2 of the Offshore Rules.

The design air temperature is to be considered for structuralelements located above the minimum water depth (i.e.LAT).

The design water temperature is to be considered for struc-tural elements located below the minimum water depth(refer to Sec 4, [6] for complementary information).

1.2.3 For elements having a yield stress above 460 N/mm2and below 690 N/mm2, thickness limitations for differentsteel grades are to be considered according to IACS Recom-mendation No. 11 (Rev 1. 1996) "Material Selection Guide-line for Mobile Offshore Drilling Units", taking into accountthe structural categories defined in [1.3].

1.3 Structural categories1.3.1 Categories to be consideredStructural elements in welded steel constructions areclassed into three categories: second, first and special cate-gories, as listed hereafter: Second category: second category elements are struc-

tural elements of minor importance, the failure of whichmight induce only localized effects

First category: first category elements are main load car-rying elements essential to the overall structural integrityof the unit

Special category: special category elements are parts offirst category elements located in way or at the vicinityof critical load transmission areas and of stress concen-tration locations.

1.3.2 Categories of structural members of self-elevated units

The structural members of self-elevated units are to be cate-gorized as indicated in Tab 1.

Structural categories are to be indicated on the drawingssubmitted to the Society for approval.

The Society may, where deemed necessary, upgrade anystructural element to account for particular considerationssuch as novel design features or restrictions regardingaccess for quality control and in-service inspections.

1.4 Steels with specified through thicknessproperties

1.4.1 The designer is to evaluate the risk of any lamellartearing.

1.4.2 The maximum allowable stress through thickness is50% of the yield stress. For Z-grade plates as defined in theShip Rules, a maximum stress of 75% of the yield stress canbe accepted as through thickness stress.

Special attention to the welding of Z-grade plates is to bepaid by the designer. The Society may require ultrasonicinspection before and after welding of the plate.

1.5 Corrosion allowances

1.5.1 The scantling obtained by applying the criteria speci-fied in the present Guidance Note are gross scantlings i.ethose which provide the strength characteristics required tosustain the loads including corrosion margin. The strengthcriteria take into account a moderate and progressive corro-sion, up to an amount of 4% in 20 years.

1.5.2 For the particular case of legs without cathodic pro-tection, a corrosion rates of 0,4 mm per year is to be consid-ered in the splash zone (i.e. in the area limited by LATminus trough of wave and the SWL plus the crest of wave)to be deduced from the as-built thickness minus the Ownermargin, as specified in [1.5.3]. The corrosion rate applieson the external shell and internal one, if relevant.

1.5.3 Any additional thickness increment, as may be pro-vided in accordance with the provisions of the OffshoreRules Pt B, Ch 3, Sec 5, is to be deduced from actual nomi-nal thicknesses prior to application of strength criteria.

Rf min ReGR

1 2,---------( , )=16 Bureau Veritas September 2010

NI 534, Sec 2Table 1 : Application of structural categories

1.5.4 When the unit is converted from an existing unit, theassessment of strength is to be based on actual measuredthicknesses reduced by any specified corrosion predictionor corrosion allowance.

2 Structural principles

2.1 Accessibility for inspection duringservice

2.1.1 Principle

Accessibility for inspection, and also for maintenance, isrequired with respect to the durability and integrity of thestructure.

2.1.2 Means of accessThe means of access in the self-elevating unit are to allowinspection of the critical structure connections identifiedduring the drawing review by the Society and/or thedesigner.

The number of inaccessible areas is to be limited andclearly identified on the structure drawings. The Societyreserves the right to require additional corrosion allowancesfor these areas. Special attention is to be paid to fatiguestrength.

Web frame numbers are to be attached to structure or walk-way inside of tanks to the satisfaction of the attending Sur-veyor.

Equipment on deck are to be arranged to allow inspectionsof the deck plating and to avoid permanent concentration ofdust and remaining water.

Structural member category

SECOND CATEGORY: second category elements are structural elements which are classed neither in the special nor in the first categories

FIRST CATEGORY: bottom plating strength deck plating, excluding that belonging to the special category side shell plating bulkhead plating belonging to main structure of the hull legs, except part classed in the special category shell plates of boxed jackhouses and main girders of truss jackhouses platings and bulkheads in spudcans deck plating, shell plating and bulkheads in mat structure heavily loaded elements forming main truss or frames of integrated decks, support frames or heavy modules structure supporting crane pedestals, large flare towers or long span bridges helideck frames cantilever beams and substructure of drill floor (legs and main beams) appurtenances connections to hull when used for essential operations excluding that belonging to the special category

SPECIAL CATEGORY: sheer strake at strength deck (1) stringer plate in strength deck (1) deck strakes in way of bulkheads participating to overall bending moment (1) strength deck and bottom plating at outboard corners of large hatch openings (monpool) bilge strake (1) vertical members of cylindrical and rectangular hollow section legs (external shell plating including vertical stiffeners if any,

racks, ...) chords, including nodes and racks, and main bracings of lattice legs connection of legs with spudcans or mat structure nodes in truss of jackhouses cast steel structural members structure in way of jacking or other elevating arrangements including padeyes or bearing members structure in way of leg locking including padeyes or bearing members leghouse guides for leg loads transferring to the hull connections of leghouses to the hull highly stressed area of appurtenance connections to the hull (including padeyes if any), when used for essential operations

(1) Single strakes are required to be of special category or of grade E/EH and are to have breadths not less than (800 + 5 L) mm,where L is the length of the hull, as defined in Sec 6.

Note 1: Any welded attachments of loaded equipments on hull plating are not to have grade lower than that used for the hull plating.September 2010 Bureau Veritas 17

NI 534, Sec 22.2 General construction

2.2.1 Structural continuityAttention is to be paid to the structural continuity:

of the leg structure

in way of the connections of leg houses (jackhouses,spudhouses) ends with the hull

of the leg connections with spudcans or mat structure

in way of changes in the framing system

at the connections of primary or ordinary stiffeners

in way of deck equipment connections.

The framing system of the hull is to consider the globalstress flow in both elevated and floating positions. In princi-ple, several framing types are adopted for triangular hulls toensure a better hull strength continuity between leghouses.Rectangular hulls are usually longitudinally framed.

Where stress concentrations may occur in way of structuraldiscontinuities, adequate compensation and reinforcementsare to be provided.

Openings are to be avoided, as far as practicable, in way ofhighly stressed areas.

Where necessary, the shape of openings is to be speciallydesigned to reduce the stress concentration factors. Particu-lar attention is to be paid to the passage of secondary stiff-eners through web plating in the stress vicinity of heavyloads.

Openings are to be generally well rounded with smoothedges.

Primary supporting members are to be arranged in such away that they ensure adequate continuity of strength.Abrupt changes in height or in cross-section are to beavoided.

2.2.2 Sniped endsIn principle, sniped ends of primary and secondary stiffen-ers are to be less than 30 degrees.

2.3 Plating

2.3.1 A local increase in plating thickness is generally to beachieved through insert plates.

Insert plates are to be made of materials of a quality at leastequal to that of the plates on which they are welded.

Plating under heavy concentrated loads may be reinforcedwith doublers (only compression loads allowed) and/or stiff-eners where necessary. Doublers in way of equipment areto be limited in size and avoided in areas of the deck withhigh stress.

Doublers having width, in mm, greater than:

20 times their thickness, for thicknesses 15 mm

25 times their thickness, for thicknesses > 15 mm

are to be fitted with slot welds, according to the Ship Rules,Pt B, Ch 12, Sec 1.

2.4 Ordinary stiffeners

2.4.1 The strength principles requirements for the ordinarystiffeners are those given in Pt B, Ch 4, Sec 3, [3] of the ShipRules.

2.5 Primary supporting members

2.5.1 The strength principles requirements for the primarysupporting members are those given in Pt B, Ch 4, Sec 3, [4]of the Ship Rules.

Additional strength principles requirements for bottom,side, deck and bulkhead structure are respectively given inthe Ship Rules, Pt B, Ch 4, Sec 4 to Pt B, Ch 4, Sec 7.

2.6 Leghouse

2.6.1 The leghouse includes all the structural elements ofthe hull allowing the load transfer between legs and hull.Therefore the horizontal guides (hull structural members incontact with the legs), the elevating and locking systemswith their supporting structure are part of the leghouse.

The leghouse is usually formed by spudhouse and jack-house.

2.6.2 Load carrying members of the leghouses are to bedesigned for the maximum design loads and are to be soarranged that loads transmitted from the legs are properlydiffused into the hull structure.

2.6.3 For the purposes of better contact and gap reductionbetween the legs and guides doubling plates may be fitted.The contact area is to be as large as possible and the extentof doublers is to cover the whole contact area.

In case several doubling plates are fitted for shell to shellcontact, the contact area is not to be interrupted because ofthe presence of doublers. The welded connections of thedoublers between them are to be as flush as possible.

In addition to normal loads due to leg-guide contact, ana-lysed according to Sec 5 and Sec 6, the welds between thedoublers and guide structure are also to withstand tangen-tial friction forces provided by leg displacements againstguides ones.

2.7 Legs

2.7.1 Legs may be either of shell type or of lattice type(truss leg type). Individual footings (spudcans) may be fittedor legs may be permanently attached to a bottom mat.

2.7.2 Shell type legs (cylindrical or rectangular hollow sec-tion) may be designed as either stiffened or unstiffenedshells.

All structural elements participating to the global strength ofthe legs (shell, ordinary stiffeners) are to be continuouswhen crossing primary members.18 Bureau Veritas September 2010

NI 534, Sec 2Table 2 : Equivalent leg strength properties

Leg type Equivalent properties

1

A = 3 ACAShy = AShz = 3/2 AShIy = Iz = 1/2 AC b2

IT = 1/4 ASh b2

2

A = 4 ACAShy = AShz = 2 AShIy = Iz = AC b2

IT = ASh b2

3

A = 4 ACAShy = AShz = 2 AShIy = Iz = AC b2

IT = ASh b2

4

A = (D t) t

AShy = AShz = A/2

5

A = 2 t (b1 + b2)AShy = 2 t b2AShz = 2 t b1

A : Cross sectional areaAC : Cross sectional area of the chords (including racks as stipulated in Sec 5, [2.3.1]AShy : Shear area with respect to y-axis of the legAShz : Shear area with respect to z-axis of the legASh : Shear area of the one leg side, as defined in Tab 3Iy : Moment of inertia about the y-axis of the legIz : Moment of inertia about the z-axis of the legIT : Torsion moment of inertiab : Distance between chordsD : Outer diameter of cylindrical shell leg typeb1, b2 : Respectively depth and breadth of rectangular hollow section legt : Thickness of the leg shell.

b

b

y

z

Ac

b

b

Ac

y

z

b

b

y

z

Ac

t

D y

z

Iy Iz t D t( )3

8-------------------------= =

IT t D t( )3

4-------------------------=

t

tb1

b2

y

z

Iy1

12------ b2b1

3 b2 2t( ) b1 2t( )3[ ]=

Iz1

12------ b1b2

3 b1 2t( ) b2 2t( )3[ ]=September 2010 Bureau Veritas 19

NI 534, Sec 2Table 3 : Equivalent shear area of one leg side for lattice legs

2.7.3 Lattice leg type are usually made of tubular members.Particular attention is to be paid to tubular connectionswhich are highly stressed areas subject to fatigue. Generallyexcentricities are to be minimized.

The bracing system of lattice legs is to be so arranged toensure structural redundancy.

2.7.4 The mechanical properties of lattice and shell leg typemay be obtained from formulae given in Tab 2 and Tab 3.

2.8 Spudcans and bottom mat

2.8.1 When spudcans are fitted, particular attention is to bepaid on the connection to the legs which may be subject tofatigue. Suitable overlapping of the legs are to be fitted so asto transfer the loads from the legs to the spudcan.

2.8.2 When the bottoms of the legs are attached to a mat,particular attention is to be given to the attachment and theframing and bracing of the mat, in order that the loadsresulting from the legs are properly distributed.

2.9 Deckhouses and superstructures

2.9.1 Deckhouses and superstructures are to have sufficientstrength for their size, function and location, with due con-sideration given to the environmental conditions to whichthe unit may be exposed. Their scantling is to be designedin transit conditions for sustaining green water pressure onunprotected front bulkheads as defined in Sec 8, [3].

2.10 Reinforcements in way of supportingstructures for hull attachments

2.10.1 Generally, the supports for attachments and appur-tenances are to be fitted in way of longitudinal and transver-sal bulkheads or in way of deck beams. Other supports areto be fitted in way of large primary supporting members.The main structure may be locally reinforced by means ofinsert plates.

Cut outs in local structure in way of hull attachments are tobe closed by full collar plates.

Particular attention is to be paid to buckling below supports.

Structure Equivalent shear area of one leg side

1

2

3

4

ASh : Shear area of one leg side legAD : Cross-sectional area of diagonal bracingsAC : Cross-sectional area of chords (including racks as stipulated in Sec 5, [2.3.1]AT : Cross-sectional area of vertical bracingsb : Distance between chordss : Spacing of baysd : Length of diagonal bracings : Poissons ratio. Unless otherwise specified, a value of 0,3 is to be taken into account.

dAD

b

S

ASh1 +( )sb2

d3

2AD----------

--------------------------=

AD

ATb

S

d

ASh1 +( )sb2d3

AD-------

b3

8AT----------+

--------------------------=

d

AD b

S

ASh1 +( )sb2

d3

4AD----------

--------------------------=

d

AD

ATb

S

ASh1 +( )sb2d3

2AD----------

h3

2AT----------+

---------------------------=20 Bureau Veritas September 2010

NI 534, Sec 3SECTION 3 DESIGN CONDITIONS

1 General

1.1 Definition

1.1.1 The design conditions are data on which the struc-tural design is based. The data are to include a descriptionof:

the general configuration of the unit (air gap, leg lengthpenetration, leg length reserve )

the distribution of fixed and operational loads (see Sec 5,[4.1])

the environmental conditions (see Sec 4)

the wind screen areas

any other relevant data.

1.2 Modes of operation and accidentalconditions

1.2.1 The design conditions are to be specified by the partyapplying for classification for all modes of operation (seealso Sec 1, [2.2]) and accidental conditions:

a) Operating design conditions:

The operating design conditions are defined as the moststringent conditions for the strength and the stability ofthe self- elevating unit during working mode.

The environmental data to be specified for these condi-tions are to constitute the limits for a condition of opera-tion of the unit or for the operation of a particularequipment or system.

b) Severe storm design conditions:

The severe storm design conditions are defined as themost stringent conditions for the strength and the stabil-ity of the self-elevating unit during survival mode. Theyare considered as extreme conditions.

The environmental data for these conditions, as speci-fied in Sec 4, are to be provided for a return period notlower than:

50 years, in general

100 years,, for self-elevating units permanentlyinstalled on site.

c) Transit design conditions:

The transit design conditions are the most stringent con-ditions for the strength and the stability of the self-ele-vating unit during field or ocean transit mode (seedefinitions in Sec 1, [2.2.1]).

If ocean transit is not allowed, it is to be stipulated in theDesign Criteria Statement.

In principle, the legs are elevated in transit operations

The initial transportation to site of a permanent installa-tion is also considered as a transit condition.

d) Installation/retrieval design conditions:

Installation/retrieval design conditions are defined as themost stringent conditions for the strength and the stabil-ity of the self-elevating unit during installation orretrieval mode.

Installation/retrieval design conditions cover leg impactconditions while lowering the legs and pre-loading con-dition (for units without bottom mats).

Pre-loading condition is a condition where the legs arestatically loaded at the maximum vertical loading asso-ciated with extreme storm condition.

e) Accidental conditions, if relevant:

The design of the unit may consider the possibility ofaccidental loads resulting from collisions, droppedobjects, fire or explosions.

For accidental conditions, broken bracings, brokenjoints, leg deformation, punch through and boat impactmay be studied.

In principle, the environmental data for the accidentalconditions, as specified in Sec 4, are to be taken for areturn period of 1 year.

1.2.2 All the above loading conditions are to be describedin details in the Operating Manual.

2 Self-elevating unit in elevatedcondition

2.1 Calculation methodology

2.1.1 A global analysis of the self-elevating unit in elevatedposition is to be carried out for checking the overall behav-iour.September 2010 Bureau Veritas 21

NI 534, Sec 32.1.2 The self-elevating unit response is generally non-lin-ear for the following reasons:

the non-linear wave loadings, due to:

- the hydrodynamic drag loads

- the wave kinematic

- the variation of the submerged portion of the legs

- the interaction between wave and current

the non-linear amplification of the large deflections ofthe legs

the resonance of the structure at wave period

the non-linear interactions such as:

- leg/hull interaction

- leg/sea bottom interaction

the static inclination of the legs, due to:

- fabrication tolerance

- fixation system

- hull inclination.

These non-linearities are to be properly taken into accountfor the resistance assessment.

2.1.3 In general, a deterministic analysis (design wavemethodology) is accurate enough for resistance assessment.Calculation methodology for deterministic analysis, model-ling, loads and load effects are described in Sec 5. The pro-cedures for wave load calculation is defined in Sec 5, [4.4].

Stochastic analysis (irregular sea state described by waveenergy spectrum) is required for structure with significantdynamic response (see Sec 5, [4.5.4]) and fatigue assesse-ment. Further information of stochastic analysis, in both fre-quency and time domain, are mentioned in Technical andResearch Bulletin 5-5A, Guidelines for Site Specific Assess-ment of Mobile Jack-up Units published by the Society ofNaval Architects and Marine Engineers (SNAME).

2.2 Loading conditions

2.2.1 The structural strength assessment of a self-elevatingunit in elevated position, is to be based on the followingdesign conditions:

operating design conditions

severe storm design conditions

accidental conditions

pre-loading conditions.

The corresponding load cases are specified in Sec 5, [5.2].

3 Self-elevating unit in transitconditions

3.1 Design considerations for hull structure

3.1.1 The hull of the self-elevating unit is to be designed towithstand sea pressure, internal tank pressure, inertia loadsand hull girder loads.

The hull strength is to comply with requirements given inSec 6.

3.2 Design considerations for legs and hull /legs connection

3.2.1 GeneralStructural elements of the unit (legs, leg/hull connection)are to be designed for the static and inertia forces inducedby the motions and accelerations of the self-elevating unitin the most severe environmental conditions for the two fol-lowing conditions:

field transit conditions

ocean transit conditions.

Legs and legs/hull connection structure are to be assessedusing the simplified approach defined in Sec 6. Alternativemethodology may be accepted by the Society on a case bycase basis.

3.2.2 Leg arrangementThe legs and legs/hull connection structure are to beassessed for any proposed leg arrangement with respect tovertical position during field and ocean transit moves, andthe approved positions are to be specified in the OperatingManual (see Sec 1, [3.7]). Such leg arrangements are also tobe considered for stability assessment.

3.2.3 Motions and accelerationsLegs and legs/hull connection structure are to be designedfor bending moments and forces caused by motions takinginto account:

a minimum value of single amplitude of roll or pitchequal to 6 at the natural period of the unit (see Sec 6,[3.1.3]) plus 120% of the gravity caused by the legsangle of inclination for field transit conditions

values given by the hydrodynamic calculation as speci-fied in [3.2.4] or, as an alternative, a value of singleamplitude of roll or pitch equal to 15 at a 10 s periodplus 120% of the gravity caused by the legs angle ofinclination for ocean transit conditions.

3.2.4 Hydrodynamic calculations and model testsMotions and accelerations to take into account for both fieldand ocean transit conditions may be derived from hydrody-namic calculations (see App 1 for the methodology) and/orobtained from model tests on the basis of the units charac-teristics and intended environmental transit conditions.22 Bureau Veritas September 2010

NI 534, Sec 3Motions and accelerations for transit conditions are to bedetermined based on significant metocean data with areturn period of at least:

50 years for mobile units

10 years for permanent units, except when otherwisespecified by the party applying for the Classification.

In no case, these values of motions and accelerations are tobe lower than those given in [3.2.3] for field transit condi-tion.

Hydrodynamic calculation may be required by the Societywhen deemed necessary.

3.2.5 Wind loads

The effect of wind forces resulting from maximum windvelocity, as defined in Sec 5, [4.3], is to be taken intoaccount in addition to [3.2.3].

3.3 Dry tow transit

3.3.1 Dry tow transit (transit mode where the unit is carriedas cargo on another ship) is not covered within the scope ofclassification.

4 Installation / retrieval designconditions

4.1 Leg impact4.1.1 Legs are to be designed to withstand the dynamicloads which may be encountered by their unsupportedlength just prior to touching bottom, and also to withstandthe shock of touching bottom while the unit is afloat andsubject to wave motions.In principle, leg strength due to its impacts on sea bottom isto be examined in accordance with Sec 6, [4.2.1], except ifmore detailed analysis is provided.September 2010 Bureau Veritas 23

NI 534, Sec 4SECTION 4 ENVIRONMENTAL CONDITIONS

Symbols

Hs : Significant wave height, in m, corresponding tothe mean wave height of the third highest waves

Tp : Peak period of the wave spectrum, in s

Tz : Zero up-crossing period, in s.

1 General

1.1 Application

1.1.1 The purpose of this Section is to provide requirementsregarding the necessary environmental information to bespecified by the party applying for classification for assess-ing the structural design of a self-elevating unit.

1.2 References

1.2.1 Industry Standards

a) ISO 19901-1:2005 Petroleum and natural gas industries- Specific requirements for offshore structures - Part 1:Metocean design and operating conditions

b) Technical and Research Bulletin 5-5A, Guidelines forSite Specific Assessment of Mobile Jack-up Units pub-lished by the Society of Naval Architects and MarineEngineers (SNAME)

c) API RP 2A-WSD Recommended Practice for Planning,Designing, and Constructing Fixed Offshore Platforms -Working Stress Design - latest edition

d) ISO/DIS 19905-1 Petroleum and natural gas industries -Site-specific assessment of mobile offshore units - Part 1:Jack-ups.

1.3 Environmental data

1.3.1 Environmental data are to be specified by the partyapplying for classification. They are to include:

data for the severe storm design condition (extreme, sur-vival), in accordance with requirements of Sec 3, [1.2.1]

data for the limiting environmental (threshold) condi-tions considered for operating, transit, installation andpreloading design condition of the unit

the long term distribution of environmental data onwhich the design of the structure for fatigue is based

data for any other particular design condition of the sub-ject unit.

Note 1: Different limiting conditions may be associated with differ-ent operational loads arising from the various equipment related toeach unit service but also from a given equipment (e.g. crane, etc.).

1.3.2 It is the responsibility of the party applying for classi-fication to ascertain that the environmental parameters arecorrect, complete and compatible with the use of the unit,in accordance with provisions of the present Section.

1.4 Environmental load

1.4.1 Environmental loads are loads resulting from theaction of the environment and include loads resulting from:

wave

wind

current

ice and snow, where relevant

earthquake, where relevant.

Dynamic loads induced by unit's motions (inertia forces) orby dynamic response to environment actions are to be con-sidered as environmental loads.

Reactions to environmental loads (foundations) are to beconsidered as environmental loads.

1.4.2 Specific environmental loadings such as loadings dueto ice, snow or earthquake are not dealt with the presentGuidance Note. In case such loadings are to be considered,the Offshore Rules are to be referred.

1.5 Documentation to be submitted

1.5.1 The data defining the environmental conditions are tobe specified in terms of:

wave data

wind data

current data

waterdepth and tide data

atmospheric and sea temperatures data,

and, where applicable:

marine growth

any other relevant conditions.24 Bureau Veritas September 2010

NI 534, Sec 42 Waves

2.1 General

2.1.1 Waves data are to be specified, for the purpose ofresistance assessment for each condition of the unit.

2.1.2 For a given condition of operation of the unit, thewave height is to be specified for a sufficient range of peri-ods, such that the maximum response of the unit is properlycovered for all sea states liable to be met in such a condi-tion. Directional data may be considered, where applica-ble.

2.1.3 Wave conditions to be considered for design pur-poses of the unit in elevated position (see Sec 3, [2.1]) maybe described by design wave methods or by stochasticmethod using wave energy spectrum. Stochastic method isto be used for fatigue analyses.

2.2 Design wave approach

2.2.1 In design wave approach (deterministic or quasi-static method), the sea states are represented by regularwaves.

2.2.2 The design waves are to be those that produce themost unfavorable load on the structure taking into accountthe size and shape of the structure.

2.2.3 Where the design wave approach is used, waves dataare to be specified for each design condition in terms of:

maximum wave height Hmax

associated wave period Tass

wave direction.

2.2.4 For a 3 hours sea state, the following relationshipbetween the significant wave height HS and the maximumwave height Hmax is to be considered:

Hmax = 1,86 Hs

If no associated period to Hmax is specified, it is to be takenas follows:

2.2.5 In addition to [2.2.3], wave data are to be specifiedfor wave periods equal or close to the natural period of theunit (see Sec 5, [4.5]).

2.3 Random / stochastic wave approach

2.3.1 In random / stochastic wave approach, the irregularsea states are described by wave energy spectrum.

2.3.2 For structure with significant dynamic response (seeSec 5, [4.5.4]) and for fatigue assessment, the sea state is tobe described by a random wave mode.

2.3.3 Short term irregular sea-stateA short term irregular sea state is described by means ofwave energy characterized by:

the significant wave height (Hs)

the peak period (Tp) or the zero-up crossing period (Tz)

a wave spectrum

the mean wave direction

a directional spreading function, where applicable.

Irregular sea states are actually divided into two broadtypes: wind seas and swells. Wind seas are generated bylocal wind whereas swells are waves which have no con-nection to the local wind but have travelled out the areawhere they were generated. Spectra for swells and windseas are to be clearly distinguished.

In general, the Pierson Moskowitz spectrum is to beapplied. Narrower spectrum, such as JONSWAP or swellspectrum, should be considered for location with limitedfetch or shallow water (see [1.2], item a).

2.3.4 Long term distribution of the irregular seaA long term distribution of the sea is described by a familyof wave spectra with their associated probability of occur-rence.

The sea state statistic data are generally provided under theform of a scatter diagram (table Significant wave - Waveperiod):

Tp (or Tz) intervals of 1 second

Hs interval of 1 meter

number of occurrences, with reference duration of3 hours.

The scatter diagram summarizes directions, together withnumber / percentage of occurrence of each heading sector.

Information about extreme environmental conditions, eitherdirectional or seasonal extremes (typhoons, etc.) given bymetocean specialist, is to be separately described and docu-mented in specification and is to be submitted to the Soci-ety for information.

3 Wind

3.1 Wind specification

3.1.1 Wind data are to be specified for the purpose ofresistance assessment in elevated position and for stabilityin floated position.

3.1.2 As the wind velocity changes both with time andheight above sea level, the wind design data are to be spec-ified as the wind speed at a reference height above thewater level (usually taken as 10 m above the mean waterlevel) and averaged over 1 min., or another suitable refer-ence time interval.

The wind speeds averaged over other time intervals and thevertical profiles of wind speed, which are required for thecalculation of wind loads, are to be derived from the abovereference wind speed using recognized relations.

Tass 2 5 Hmax,=September 2010 Bureau Veritas 25

NI 534, Sec 43.1.3 Wind is to be considered from any direction relativeto the unit. Directional data may be considered whereapplicable.

4 Current

4.1 Current specification4.1.1 Current data are to be primarily specified for the pur-poses of resistance assessment of the self-elevated unit inelevated position.

4.1.2 The current velocity profiles are to be specified fromthe sea bed to the water depth (SWL) and taking intoaccount the contribution of all relevant components such astidal current, wind generated current and circulation cur-rent. Unusual bottom or stratified effects are to be clearly stated.

Directional profiles may be considered, where applicable.

5 Waterdepth and tides

5.1 Waterdepth and tide specification

5.1.1 The maximum Still Water Level (SWL), as defined inSec 1, [2.3], is to be specified for the purposes of resistanceassessment of the self-elevated unit in elevated position.

5.1.2 For the purpose of strength analysis at a given site,consideration is also to be given to the minimum water-depth associated with extreme waves.

6 Design temperatures

6.1 Air temperature

6.1.1 For the emerged part of the structure (splash zone andabove), the design temperature is defined as the mean airtemperature of the coldest day (24 h) of the year for anyanticipated area of operation.

6.1.2 Where no particular value is specified, the followingdesign air temperature may be considered:

0C for units not intended to operate in cold areas

10C for units intended to operate in cold areas.

6.2 Water temperature

6.2.1 For the immersed part of the structure, the designtemperature is the water temperature of the coldest day(24 h) of the year for any anticipated area of operation.

6.2.2 Where no particular value is specified, a design watertemperature of 0C may be considered.

7 Marine growth

7.1 Marine growth specification

7.1.1 Marine growth data are to be specified for the pur-pose of global analysis of the self-elevating unit since ittends to modify the drag and inertia forces and increase theleg mass.

7.1.2 Thickness of marine growth and height of applicationon the legs of the self-elevating unit are to be specified.

8 Soil

8.1 General

8.1.1 The nature, strength and behavioural parameters(such as liquefaction potential, long term consolidation,etc.) of soil for which the unit is designed in relation withthe expected type of foundation are to be specified.

8.1.2 As a minimum, the maximum design penetration ofleg tip, footings, mat, etc., below mud line is to be speci-fied.26 Bureau Veritas September 2010

NI 534, Sec 5SECTION 5 ANALYSIS IN ELEVATED POSITION

Symbols

: Wave length to be taken equal to:

Actual value in shallow water is to be consid-ered if necessary

Pa : Average vertical loads, in kN, in the leg in wayof the locking system, if any, or at mid-distancebetween upper and lower guides otherwise

PEuler : Euler critical loads, in kN, defined by:

where k is the effective leg length factor to betaken equal to 2, except otherwise duly justified

: Sea water density taken equal to 1,025 ton/m3.

1 General

1.1 Application

1.1.1 The purpose of this Section is to provide requirementsrelated to the global analysis of the self-elevating unit in ele-vated position.The requirements in [2] and [3] apply to the structural andhydrodynamic modelling of the self-elevating unit.

The requirements in [4] and [5] apply to the determination,application and combination of loads.

The resistance assessment is dealt in [6]. It includes air gap,leg length reserve, stability and structure checks. Additionallocal analyses are specified in [6] for critical structuralmembers.

1.2 Reference

1.2.1 Industry standardsa) Technical and Research Bulletin 5-5A, Guidelines for

Site Specific Assessment of Mobile Jack-up Units pub-lished by the Society of Naval Architects and MarineEngineers (SNAME)

b) API RP 2A-WSD Recommended Practice for Planning,Designing, and Constructing Fixed Offshore Platforms -Working Stress Design - latest edition

c) ISO/DIS 19905-1 Petroleum and natural gas industries -Site-specific assessment of mobile offshore units - Part 1:Jack-ups

1.3 Calculation procedures

1.3.1 A global analysis of the self-elevating unit in elevatedposition is to be performed for checking the overall behav-

ior, assessing the air gap, the overturning stability and deter-mining the maximum strength capacity of legs, elevatingand locking system(s) and leghouses. The analysis is to bebased on environmental data submitted by the party apply-ing for classification in compliance with Sec 4.

1.3.2 Non-linear characteristics of the self-elevating unitmay be modelled either accurately or with equivalent sim-plified assumptions. In most cases, the latter ones are suffi-cient for representing a realistic global response.

1.3.3 Critical structural areas may be identified during theglobal analysis. They are to be locally analysed throughfinite element analysis.

1.4 Definitions

1.4.1 A self-elevating unit is to sustain global loads due tothe application of external environmental loads. For thepurpose of the present Guidance Note, the following defini-tions are reminded:

the overturning moment is defined as the total momentwhich is generated by environmental loads and tends tocapsize the unit

the base shear force is defined as the total horizontalresulting force transferred to the soil by the footings.

2 Structural modelling

2.1 General

2.1.1 The structural modelling is to take accurately intoaccount the geometric and mechanical properties of theunit, the distribution of the inertia and the boundary condi-tions.

The simplified and detailed levels of modelling presentedfrom [2.2] to [2.5] may be combined. In principle, a simpli-fied model performed in accordance with [2.2.1], [2.3.2]and [2.4.2] is accurate enough for assessing the overallbehavior of the self-elevating unit in elevated position.

2.2 Hull modelling

2.2.1 Beam modelIn case beam model is used for modelling the hull, the stiff-ness and inertia of the model are to represent the hull ones.The model is to be based on a grillage of equivalent beamsmodelling side shell, longitudinal and transverse bulkheads.These equivalent beams are positioned at their neutral axis.Their span, spacing, attached plating and mechanical prop-erties are to be determined according to Sec 2, [2.5].

g2-------Tass

2=

PEuler

2 EIkl( )2

-------------10 5=September 2010 Bureau Veritas 27

NI 534, Sec 5The hull is usually a closed box shape and, so, not made ofseveral open section beams. Therefore, particular attentionis to be paid to the assessment of torsional inertiae of theequivalent beams. The overall torsional inertia of the hullmay be estimated considering the hull girder as a box-typesection beam and distributed between the beams.

2.2.2 Finite element modelsThe structural model is to represent the primary supportingmembers with the plating to which they are connected.

Ordinary stiffeners are also to be represented in order toreproduce the stiffness and inertia of the actual hull struc-ture. In principle, they are to be represented by beam ele-ments.

Meshing is to be carried out following uniformity criteriaamong the different elements, i.e.:

Most of quadrilateral elements are to be such that theratio between the longer side length and the shorter sidelength does not exceed 2. Some of them may have aratio not exceeding 4. Their angles are to be greater than60 and less than 120. The triangular element anglesare to be greater than 30 and less than 120

In principle, the size of elements is not to exceed thespacing of secondary stiffeners. Finer mesh (typically100 mm x 100 mm) are to be used for local strengthassessment.

2.3 Leg modelling

2.3.1 GeneralThe leg stiffness used in the global analysis may account fora contribution from a portion of the rack tooth material. Theassumed effective area of the rack teeth is not to exceed10% of their maximum cross sectional area. When check-ing the capacity of the chords, the chord properties are tobe determined discounting the rack teeth.

2.3.2 Equivalent leg modelLattice legs may be represented as equivalent beam model.In that case, special care is to be paid on representing theactual cross-sectional and shear areas as well as bendingand torsional moments of inertia.

The formulae given in Sec 2, Tab 2 and Sec 2, Tab 3 may beused as a guidance.

2.3.3 Detailed leg modelThe legs are to be modelled using either shell or beam ele-ments. The model geometry of the leg is to be fully inaccordance with the design. For lattice leg modelled withbeam, chords and braces are to be represented at their neu-tral axis. Brackets normally need not to be taken intoaccount for the global analysis, but is to be considered forthe local analysis.

2.4 Leg / hull connection modelling

2.4.1 GeneralParticular attention is to be paid for the modelling of the leg/ hull connection since it influences the force and momentdistribution over the whole structure.

2.4.2 Simplified modellingFor simplified modelling, the connection between the legand the hull is to be assumed fixed in way of the fixatingsystem, if any; otherwise, it is to be assumed fixed at mid-distance between upper and lower guides.

2.4.3 Detailed modellingLeghouse guides and elevating / locking systems stiffnessesare to be accurately modelled and their modelling is to beduly justified (see [1.2.1], items a) and c).

2.5 Boundary conditions

2.5.1 The boundary conditions are to be considered as fol-lows:

for designing the upper part of legs as well as the leg /hull connection, the spudcans are assumed to be simplysupported

for designing the lower part of the leg, the spudcans areassumed to be fixed.

2.5.2 For the natural period assessment of the self-elevatingunit (see [4.5]), the spudcans are assumed to be simply sup-ported.

In case of self elevating units having a natural period equalto or greater than the wave period, special considerationsmay be given by the Society to the boundary conditions.

2.5.3 In lie