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ComparisonsonAPIRP2A WSD21st edition
2000Publicationvs.2007Publication
Fatigue
3/3/2011 1EngineeringDynamics,Inc
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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API S-N Curves API X' API XAPI WJT in Water API WJT in Air
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
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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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Thisistheendofthisreport.
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