ComparisonsonAPIRP2A WSD21st edition

2000Publicationvs.2007Publication

Fatigue

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OverviewTheold(wewillcallitAPI2000):APIRP2A WSD21st edition2000PublicationRecommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms Working Stress Design

Upstream Segment

API RECOMMENDED PRACTICE 2A-WSD (RP 2A-WSD)TWENTY-FIRST EDITION, DECEMEBER 2000

Andthelatest(wewillcallitAPI2007):APIRP2A WSD21st edition2007Publication(API2007)Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms Working Stress Design

Upstream Segment

API RECOMMENDED PRACTICE 2A-WSD (RP 2A-WSD)TWENTY-FIRST EDITION, DECEMEBER 2000ERRATA AND SUPPLEMENT 1, DECEMBER 2002ERRATA AND SUPPLEMENT 2, SEMPTEMBER 2005ERRATA AND SUPPLEMENT 3, AUGUST 2007

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Conclusions1. Thelatest.ThenewAPIRP2A WSD21st editionwithErrataandSupplement1,2an3hasmadewiderangingchangesontubularconnections,fatigueandfoundationsoverthe2000publication.ThenewcodeshouldbeusediftheAPIRP2A WSD21st editionisselectedasdesigncode.2. Onestopsolution,nointerfacehandling.Basedon35+yearsexperienceinsupplyingoffshorestructuresoftwaresystem,EDIistheleadingsoftwarecompanywithintegratedgraphicsmodeling,preprocessing,solvingandgraphicspostprocessingcapabilities.3. Demandthebest.Fullyimplementedinpostprocessor,fatigueprograminSACS5.3release,thenewAPIRP2A WSD21st editionwithErrataandSupplement1,2and3isnowanessentialpartinthemostcomprehensiveoffshorepackageintheworld.

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FatigueCodeContents

API20005 Fatigue5.1 Fatigue Design5.2 Fatigue Analysis5.3 S-N curves for all members and

connections, except tubular connections5.4 S-N curves for tubular connections5.5 Stress concentration factors

API20075 Fatigue5.1 Fatigue Design5.2 Fatigue Analysis5.3 Stress concentration factors5.4 S-N curves for all members and

connections, except tubular connections5.5 S-N curves for tubular connections5.6 Fracture mechanics

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Fact:ThenewAPISNcurvesfortubularconnectionsarederivedonthebasisoftheproposedISOhotspotdesignapproach.ThenewAPIWJcurvesarebilinear,withslopeexponentsofm=3andm=5,andnoendurancelimit.

FatigueBackground

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Fact:ThemainconclusionfromtheEWIstudywasthattheEfthymiouequationsandtheLloydsdesignequationshaveconsiderableadvantagesinconsistencyandcoverageincomparisonwithotheravailableequations.UseofEfthymiouSCFequationsisrecommendedbecausethissetofequationsisconsideredtoofferthebestoptionforalljointtypesandloadtypes.

FatigueBackground

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API2000Fatiguesafetyfactorsnowdependonexposurecategories

API2007

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Fatigue MajorUpdate

ExposureCategoriesExplained:

LevelBased onLifeSafetyBasedonFailureConsequencesL1 Mannednonevacuated HighConsequencesL2 MannedevacuatedMedium ConsequencesL3 UnmannedLowConsequences

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Fatigue MajorUpdateSNcurvesfortubularconnectionschanged

API2007

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API2000BasicCurves:Profilecontrol 11.1.3d:XcurveNonprofiledJoints XcurveEnduranceLimit:Yes

Fatigue MajorUpdateS-N curves for tubular connections changed - continued

API2007BasicCurves:Profiling 11.1.3d:WJ1curveBurrGrinding WJ2curveHammerPeening WJ3curveNonprofiledJoints WJcurveCastJoints CJcurveEnduranceLimit:No

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API2000

Fatigue MajorUpdateThicknesseffectcorrectionsarenowdependentonweldimprovementtechniques

API2007

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API2000Nospecificrequirement.C5.4listedempiricalformulastoestimatehotspotSCF:1) TheKuang formulas;2) SCFformulasbasedontheKelloggformula;3) SCFformulasdevelopedbyLloydsRegister;4) OthermorerecentworksbyGibstein,Buitrago andTebbett.

Fatigue MajorUpdateRecommendedSCFformulationsinunstiffenedtubularjointschanged

API2007Forunstiffenedweldedtubularjoints,SCFsshouldbeevaluatedusingtheEfthymiou equations.

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API2000

Fullyimplemented

ImplementationintoSACSfatigueprogram

API2007

Fullyimplemented

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Fatigue MajorUpdate

Exampleframe:Twobayframewith10mx10mforeachbay.Twobasicloadcases:

Loadcase1:Fx =60.0kN atjoint3,4,5and6

Loadcase2:Fx =60.0kN atjoint3,4,5and6

Fatigue Example

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API2000Fatigueparameters

Lifesafetyfactor=2.0Designfatiguelife=20yrsPeriodforcycledata=20yrsNumberofoccurrences=250000Dynamicamplificationfactor=1.5Stressrangedeterminedbymax/minsearchonloadcases.

SNcurve:APIXcurvewiththicknesscorrection.

Fatigue ExampleAPI2007Fatigueparameters

Lifesafetyfactor=2.0forinspectableandnonfailurecriticaljointcaseLifesafetyfactor=5.0forinspectableandfailurecriticaljointcase

Othersaresameaslefthandside

SNcurve:APIstandardWJcurvewiththicknesscorrection.

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Fatigue ExampleResultsCompared

API2000fatigueResultsBasedonSafetyFactor=2foralljoints

JOINT MEMBER GRUP MEM FATIGUE RESULTS ID TYP DAMAGE LOC SVC LIFE

3 3- 2 D01 BRC 1.683053 T 11.88317

3 1- 3 COL CHD 1.450054 T 13.79259

3 3- 6 D01 BRC .2674743 T 74.77355

3 3- 5 COL CHD .1664706 T 120.1414

3 3- 4 H01 BRC .1002682 B 199.4651

3 1- 3 COL CHD .1029080 B 194.3484

4 3- 4 H01 BRC .0552595 T 361.9287

4 2- 4 COL CHD .0903428 T 221.3790

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API2007fatigueResultsBasedonSafetyFactor=2forInspectableandnonfailurecriticaljoints

JOINT MEMBER GRUP MEM FATIGUE RESULTS ID TYP DAMAGE LOC SVC LIFE

3 3- 2 D01 BRC .3836923 T 52.125103 1- 3 COL CHD .5487570 T 36.446013 3- 6 D01 BRC .0877449 T 227.93353 3- 5 COL CHD .0966789 T 206.87043 3- 4 H01 BRC .0341228 B 586.11793 1- 3 COL CHD .0610985 B 327.34034 3- 4 H01 BRC .0153856 T 1299.9174 2- 4 COL CHD .0550383 T 363.3832

API2007fatigueResultsBasedonSafetyFactor=5forInspectableandfailurecriticaljoints

JOINT MEMBER GRUP MEM FATIGUE RESULTS ID TYP DAMAGE LOC SVC LIFE

3 3- 2 D01 BRC .9592308 T 20.850043 1- 3 COL CHD 1.371892 T 14.578403 3- 6 D01 BRC .2193622 T 91.173423 3- 5 COL CHD .2416972 T 82.748153 3- 4 H01 BRC .0853071 B 234.44723 1- 3 COL CHD .1527462 B 130.93614 3- 4 H01 BRC .0384640 T 519.96674 2- 4 COL CHD .1375958 T 145.3533

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