risk263企业邮箱设置
263企业邮箱设置 时间:2021-02-20 阅读:()
The14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China1DeterminationofSeismicFortificationLevelofOffshorePlatformsinChinaYuejunLU1,YanjuPENG2,RongyuTANG3andHaijunSHA41Researcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,ChinaEmail:luyj1@263.
net2AssociateResearcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,China3Researcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,China4AssociateResearcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,ChinaABSTRACT:ThecurrentseismicdesigncodecommonlyusedintheworldisRP2A-WSDcompiledbyAmericanPetroleumInstitute,thereisstillnospecificseismicdesigncodeforoffshoreplatformsinChina.
Inthispaper,abriefintroductionofRP2A-WSDcodeisgivenatfirst,andthecomparisonbetweentheseismicfortificationlevelsofRP2A-WSDandthatofChineseGB17503-1998andGB50011-2001suggeststhatthelevelsofChineseCodesareoverestimated.
Secondly,theseismicdamagesandanti-seismicdesignrequirementsofoffshoreplatformsarediscussedinviewoftheirstructuralcharacteristics.
Onthebasisoftheanalysisabove,summingupthefactors,suchastheseismicactivityinthewatersofChina,structuralcharacteristicsofoffshoreplatform,seismicdesigngoal,andtheseismicfortificationexperiencesofrelatedengineering,werecommendthattheseismicfortificationlevelofstrengthdesigntakeareturnperiodof200years,andthatofdeformationdesigntakeareturnperiodof3000yearsrespectivelyforoffshoreplatformsinChina.
Finally,thecomparisonwithotherChineseCodesofrelatedindustriesshowsthattherecommendedfortificationlevelissafeandrational.
KEYWORDS:OffshorePlatform,SeismicDesign,SeismicFortificationLevel,ReturnPeriod0INTRODUCTIONSincethe80soflastcentury,theexploitationofoceanoilgainedverygreatprogressinChina,Over100offshoreoilplatformshavebeenbuiltinBohai,Huanghai,EastChinaSeaandSouthChinasea,another100willbeerectedinthecoming5years.
Thedamageofoffshoreoilplatformsmaycauseseveresecondarydisasters,andtheseismicityintheseasofChinaisrelativelyhigh,thus,theseismicdesignproblemofoffshoreplatformshasattractedconsiderableattention(LuYuejun,etal,2003).
FixedplatformsaremostlyusedintheexploitationofoceanoilinChina,theirlifespanisratherlong,commonlyismorethan15years.
Duringthelifespantheplatformcannotmove,andmustsupportsomeenvironmentalloads,includingwind,wave,current,ice,earthquakeandsoon.
Thestructuraldamagewillcauseseriouspersonnelcasualty,equipmentloss,oilproductionstop,andenvironmentalpollution.
Inplatformdesigning,earthquakeloadshouldbeimposedontheplatformasaseparateenvironmentalloadingcondition,otherenvironmentalloadsshouldbecombinedinamannerconsistentwiththeprobabilityoftheirsimultaneousThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China2occurrenceduringtheloadingconditionbeingconsidered.
Andearthquakeloadisseriouslydestructive,andcannotbepredicted.
Therefore,theseismicanalysismustbetakenintoaccountinstructuraldesigning.
NospecificseismicdesigncodehasyetbeendraftedforoffshoreplatformsinChinabecauseofinsufficientknowledgeontheseismiccharacteroftheseaareas.
ThecurrentseismicdesigncodecommonlyusedintheworldisRP2A-WSDcompiledbyAmericanPetroleumInstitute(AmericanPetroleumInstitute,2002).
Seismicfortificationistoprovideresistancetoearthquakeforengineeringstructures.
Thefollowingthreefactorsshouldbetakenintoconsiderationinthedeterminationoftheseismicfortificationofengineeringstructures,socialeconomiclevel,seismichazardandimportanceofstructures.
Thekeycontentoftheseismicfortificationisseismiclevelandgrade(XieLili,etal,1996).
Inthispaper,acomparisonbetweentheseismicfortificationlevelsofRP2A-WSDandthatofChineseGB17503-1998andGB50011-2001iscarriedout,anditisregardthatthelevelsofChineseCodesareoverestimated.
Summingupthefactors,suchasseismicactivityintheseasofChina,structuralcharacteristicsofoffshoreplatforms,seismicdesigngoal,andtheseismicfortificationexperiencesofrelatedengineering,werecommendthattheseismicfortificationleveltakesareturnperiodof200yearsforstrengthdesign,and3000yearsfordeformationdesignrespectivelyforoffshoreplatformsinChina.
Finally,thecomparisonwithotherChineseCodesofrelatedindustryshowsthattherecommendedfortificationlevelissafeandrational.
1.
THECURRENTSEISMICDESIGNCODEOFOFFSHOREPLATFORMANDEXISTINGPROBLEMS1.
1.
ThecurrentseismicfortificationcodeThereisnoseismicdesigncodeofoffshoreplatforminChinaatpresent.
TheGB17503-1998suggeststhatthelevelsofthestrengthanddeformationdesigntake10%and0.
5%probabilitiesofexceedancein50years.
The10%and0.
5%probabilitiesofexceedancein50yearscorrespondtoareturnperiodof475and10000yearsrespectively.
Butthiscodedoesnotgiveacorrespondinginterpretationoftheiritems.
BasedontheseismicactivityandseismicriskmapinthecostalwatersoftheUnitedStates,RP2A-WSDiscompiledbyAmericanPetroleumInstitute(AmericanPetroleumInstitute,2002).
Thecodestatesthattwolevelsofgroundmotionintensityduetomoderateandrareintenseearthquakesinthelifespanofoffshoreplatformshouldbeconsideredinstrengthdesignanddeformationdesignrespectively.
Thedesignseismiclevelmeetsthestrengthrequirements,thatis,toprovideresistancetomoderateearthquakeswithoutsignificantstructuraldamage,arecurrenceintervalof200yearsforpermanentstructuresinSouthernCaliforniaisrecommended.
Therareintenseearthquakeistheinputfordeformationdesign,nolifelossandsignificantenvironmentpollutionisallowedatthislevel,structuraldamageislikelytooccur,buttheprovisionsareintendedtopreventcollapseoftheplatform,thereturnperiodmaybeseveralhundredtoafewthousandyears.
Thefirstlevelprovidesthegroundmotioninputfortheelasticdesignofthestructure,andthesecondlevel,ifitisdeemednecessarytoanalyzethestructureforrareintenseearthquakes,providesthegroundmotioninputfortheThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China3analysis.
1.
2.
ExistingproblemsTheprovisionsandmethodofRP2A-WSDCodeareusedinseismicanalysisoftheplatform,namely,strengthdesignanddeformationdesignarecarriedoutrespectively(WangZhongcang,2005).
ButtheseismicfortificationlevelsareaccordingtoGB50011-2001(MinistryofConstructionP.
R.
China,2001)andGB17503-1998.
TheseCodesareinconsistent.
AcomparisonofseismicityismadebetweenSouthernCaliforniaandBohaiSeabyPengYanjuetal(2006),whichshowsthattheearthquakenumber,strainenergyrelease,andPGAinSouthernCaliforniaareallhigherthanthatinBohaianditsadjacency.
TheoilfieldPL19-3isajointventureprojectofChinaandtheUnitedStates,anddesignedinlightofAPIRP2A-WSDcode.
AccordingtoAPIRP2A-WSDandtheChineseCodeGB17503-1998,PengYanjuetal(2007)obtainedtheseismicdesignparametersattheoilfieldsite,thePGAatthestrengthdesignlevelanddeformationdesignlevelis252cms-2and570cms-2respectivelybytheChineseGB17503-1998,andthatis162cms-2and333cms-2respectivelybyAPIRP2A-WSDcode,theratiois1.
55and1.
71times.
Therefore,Chinaisadevelopingcountrywithlimitedfinanceandresources,thereisnoneedtoadoptaseismicfortificationlevelofoffshoreplatformhigherthanthatindevelopedcountries.
2.
STRUCTURALCHATACTERISTICSOFTHEOFFSHOREPLATFORMANDENGINEERINGSEISMICPROBLEMS2.
1.
AbriefintroductionofthestructureofoffshoreplatformThestructuralformsoffixedplatformincludejacket,gravity,tower,andsoon.
Thejacketplatformisthemostpopularstructuralformintheexploitationofoceanoil(gas),andconsistofthefollowing:redundantweldedtubularspaceframeservesasthemainstructuralelementoftheplatform,transmittinglateralandverticalforcestothefoundation,pilespermanentlyanchortheplatformtotheoceanfloor,andcarrybothlateralandverticalloads,asuperstructureprovidingdeckspaceforsupportingoperationalandotherloads.
Theintrinsicperiodofthestructureis1to3sdependingonitssize,weight,pilesdeepness,andwaterdepth.
2.
2EngineeringseismologicalproblemsoftheoffshoreplatformAsformostothertypesoffacilities,itisnotwarrantedandnoteconomicaltodesignoffshoreplatformtoprecludeanydamageforthemostsevereearthquakegroundshakingpossible.
Theactualprincipleisintendedtoprovideresistancetomoderateearthquakes,whichhaveareasonablelikelihoodofnotbeingexceededduringThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China4thelifespanoftheplatform.
Itisneededtoconstituteascientificandreasonableseismicdesigncodeanddetermineseismicfortificationlevel.
Whiledesigningoffshoreplatform,earthquakeforcesaretakenintoaccounttoensurethestructureatlinearelasticityinthelife.
Oncetherearesomestructuralmemberswhicharebendedanddestroyed,thestructureisregardedasreachingtheutmostcarryingcapacityandcannotbeusednormally.
Accordingtotheponderanceofthestructuralmembersinthewholestructure,thedestructivestateofplatformisdividedintotworanksbyWeiWei(2004):(1)Thenon-importancedestructivestate,thisistheutmostbeforethestructuregoesintoplasticstate,butthestructureisstillatlinearelasticity.
Hereon,theplatformcanstillbeused,orcanberepaired.
(2)Thelocalcollapsestate,thisstateisattheutmostofcarryingcapacity,thestructureoritsmembersreachthebiggestallowablecarryingfunction.
Theplatformcannotbeusedanyfurther,somestructuralmembersorthewholestructureundergomortaldeformation,butwithoutcollapsing.
Thestudyresultprovidedatheoreticalbasisforthedeterminationofseismicfortificationgoal.
Theseismicinfluenceontheplatformstructureismostlybroughtbythebasemovement,tofulfillseismicanalysis,someseismicparametersatthebasesitearerequired,includingthepeakvalues,responsespectra,andtimehistoryofthegroundmotion.
Theparticularityofengineeringseismicproblemsoftheoffshoreplatformisthelongperiodgroundmotion,theoffshoreplatformisalongperiodstructure,atthesametime,thereciprocityofplatformandwater(appendedmass)alsomakestheresonanceperiodlonger.
Commonly,themajorityofconstructsandstructuresusethepeakvaluesofseismicaccelerationastheindexofseismicanalysis,andtheplatform,whichislongperiodstructure,shouldusevelocityordisplacement,butthecurrentseismicanalysisoftheplatformstillusesaccelerationbecauseofinsufficiencyofengineeringseismicstudy.
LuYuejunetal(2003)discussedsomeengineeringseismicproblemsofplatformindetail,includingscenarioearthquake,longperiodgroundmotion,andsoon.
3.
DETERMINATIONOFSEISMICFORTIFICATIONLEVELFORLEVELFOROFFSHOREPLATFORM3.
1.
DeterminationofdesignruleBasedontheanalysisofengineeringseismicproblemsoftheoffshoreplatforminabovesection,seismicfortificationforplatformmayhaveananalogywithsomespecialstructureinland,suchasTVtransmissiontower,oversizebridge,greatdamandsoon.
Referringtotheseismicfortificationexperiencesofrelatedengineering,thefollowingfactorsshouldbetakenintoconsiderationinthedeterminationoftheseismicfortificationofplatform.
(1)TomeettheChineseandforeigncurrentcodePresently,inordertofittothedevelopingtrendofinternationalanti-seismictechnology,theseismicdesignThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China5thinkingistransferringfromsafetyfactortoreliabilitydesigninChina.
Sotheseismicfortificationlevelbasedonprobabilityisneededtomeetthedemandofreliabilitydesign.
(2)Considerationoffortificationclassificationandmultiple-stagedesignReliabilitydesignmakesthestructuretomeetthedemandofspecificultimatestatebycontrollingthemajorconditions.
AccordingtoactualengineeringstructuredesigninChina,theultimatestatemaybedividedintothreestates:serviceabilitylimit,ultimatecarryingcapacity,andultimatedeformation.
Theengineeringstructuredesignismadeaccordingtocarryingcapacityforeachstate,andtheseismicfortificationisgivenbasedonthedifferentultimatecarryingcapacity.
Forexample,GB50011-2001adoptsthreeseismicfortificationlevelsandtwo-stagedesign.
(3)KeeptheconsistencywiththestatepolicyofseismicfortificationThestateseismicdesignpolicyrestrainsthefortificationlevel.
Thegroundmotionparameters(e.
g.
peakaccelerationandresponsespectrum)specifiedinthepresentcodessuchasGB50011-2001,arealllowerthanobservationvalues.
Thereforetheseismicfortificationlevelforoffshoreplatformsshouldnotbetooconservative,andthereisnoneedtotakeahighervaluethanthatindevelopedcountries.
3.
2Determinationofseismicfortificationlevelforoffshoreplatform(1)DesignreferenceperiodDesignreferenceperiodliesonthelifespanoffacilities.
Becausethedurationofexploitationofoceanoil(gas)isabout30years,asuitabledesignreferenceperiodofoffshoreplatformis30years.
(2)SeismicfortificationgoalThedestructivestateofplatformisdividedintotworanks:thenon-importantdestructionstateandthelocalcollapsestate.
Hereby,consideringtheexistingdesignrule,theseismicfortificationgoalforoffshoreplatformisdeterminedaccordingtotwolevelsduetofrequentandrareearthquakesduringthelifespan.
Thefrequentearthquakelevelmeetsthestrengthrequirements,thatis,toprovideresistancetofrequentlyencounteredearthquakeswithoutsignificantstructuraldamage,theplatformmaintainserviceability,orcanberepaired.
Therareearthquakeistheinputfordeformationdesign,structuraldamageislikelytooccur,buttheprovisionsareintendedtopreventcollapseofthewholestructure,nolifelossandsignificantenvironmentpollutionisallowedatthislevel.
(3)Thefrequent-earthquakelevelThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China6Thefrequentearthquakescorrespondtoearthquakeforcesunderserviceabilitylimitdesignstate.
Forcommonconstructandstructure(theclassC),thedesignreferenceperiodis50years,thefrequentearthquakeleveltakes63%probabilitiesofexceedancein50years,correspondingtoareturnperiodof50years.
Offshoreplatformisanimportantengineeringstructure,consequentlytheseismicfortificationlevelshouldbehigherthanthatforcommonconstructandstructure.
AccordingtotherecommendedvalueforSouthernCaliforniainRP2A-WSD,thestrengthdesignlevelforoffshoreplatformisareturnperiodof200years,correspondingto14%probabilitiesofexceedancein30years.
Theintensityatfrequent-earthquakelevelforcommonstructuresis1/3ofmediumearthquakes(returnperiod475years).
Accordingtostatisticof128resultsofseismicsafetyassessmentthroughoutthewholecountry,earthquakeforcesatreturnperiodof200yearsis2/3ofreturnperiodof475years,therefore,thefrequent-earthquakelevelforoffshoreplatformtakesareturnperiodof200years,whichcorrespondsto2timesthestrengthatthefrequent-earthquakelevelforclassCstructuresandisequivalenttothatforclassAstructures.
(4)TherareintenseearthquakelevelTherareintenseearthquakescorrespondtoearthquakeforcesinutmostdeformationdesign.
Inthedesignreferenceperiodofplatform,thestructuresuffersfromsuchearthquakeforcesbyaccident,thestructureislikelytoincurthebiggestdeformation,butcankeepoverallstabilitywithoutcollapse.
Thelevelofrareintenseearthquaketakes2~3%probabilityofexceedancein50yearsforclassCstructures,correspondingtoareturnperiodof1500to2500years,thatforclassAstructurestakes2~3%in100years,correspondingtoareturnperiodof3000to5000years.
Usuallythedesignreferenceperiodofoffshoreplatformsis30years,becausethedamageofplatformsmaycausegreateconomiclossandenvironmentpollution,itisappropriatethatthedeformationdesignleveltakes1%in30years,correspondingtoareturnperiodof3000,whichisalreadyhigherthanthatforclassAstructuresandapproximatestotheupperlimitinRP2A-WSD.
Accordingtotheanalysisabove,andtakingRP2A-WSDasareference,itissafeandrationaltotaketheearthquakeswithareturnperiodof200yearsand3000yearsforoffshoreplatformsinChinaasthestrengthanddeformationdesignlevelrespectively.
4.
ACOMPARISONWITHRELATEDCODES4.
1.
Acomparisontothecodesofoil/gasandotherchemicalstructuresOil/gasandotherchemicalstructuresarelargeandcomplexengineeringsystems,includingcomprehensivestation,pipeline,oilstorage,chemicalstructure,andsoon.
Incaseofearthquakedemolishment,thestructuraldamagewillcauseseriouseconomicallossandenvironmentalpollution,sotheseismicproblemsaretakenseriously.
Basedonthestructuralcharacteristicsandimportance,oil/gasandotherchemicalstructuresaredividedintothreeclasses:A,B,andC;theoffshoreplatformisaffirmedasclassAoftheutmostimportance.
Werecommendthattheseismicfortificationlevelofstrengthdesigntakesareturnperiodof200years,andthatThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China7ofdeformationdesigntakesareturnperiodof3000yearsrespectively,thereturnperiodisthelongestinoil/gasandchemicalindustry.
Wemayregardthattheseismicfortificationmeasuresforoffshoreplatformsarestricter,itsseismicriskissmaller.
Table1TheseismicfortificationlevelforoilandgasstructuresClassStructureReferenceperiod(a)Returnperiodforfrequentearthquakes(a)Returnperiodforrareintenseearthquakes(a)AOffshorePlatform302003000BLargecomprehensivestation,importantsectionofoil&gaspipeline,largeoilstructureandimportantchemicalstructure50100300030502500COilgasandotherchemicalstructuresbesidesClassA&B50502500303015004.
2.
ComparisonwithseismicfortificationlevelsofrelevantindustriesBecausetheseismicdesignideavariesindifferentindustrialfields,itisobviouslydifficulttocomprehensivelycomparethedifferencebetweentheirseismiclevels.
Therefore,onlythoseindustrialdepartments,whichhavethesameseismicdesignideaandsimilarseismicfortificationgoal,areselectedtocompare;hereweemphasizeacomparisonofthereturnperiodofrareearthquakebetweendifferentstructures.
Inordertorationallyreflectthedifferenceofseismicfortificationforstructureswithdifferentreferenceperiodandreturnperiod,weconvertreturnperiodtoprobabilityofexceedance(PT)inreferenceperiod,then(PT)canindicatetherelativeseismicriskinthereferenceperiod.
Table2isthedeformationdesignlevelofdifferentstructures.
Thedatashowsthatthereferenceperiodofoffshoreplatformsisrelativelyshort,theprobabilityofexceedanceofrareearthquaketakes0.
01inthereferenceperiod.
Itsseismiclevelisjustlowerthanthatfornuclearpowerstation,andmatchesuptothatfortheThreeGorgeDam.
Thereforeareturnperiodof3000yearsofrareearthquakeforoffshoreplatformissafe.
Table2ThedeformationdesignlevelofdifferentstructuresStructureReferenceperiod(a)RareearthquakeReturnperiod(a)PTOffshoreplatform3030000.
01Nuclearplant40100000.
004ThreeGorgeDam100100000.
01HydraulicstructuresofClassAreservingwater10050000.
02BuildingsandStructuresofClassA1003000~50000.
02~0.
03Large-scaleBridge10033000.
03The14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China8TelevisionTowerofClassA10020000.
05BuildingsandStructuresofClassB5025000.
02BuildingsandStructuresofClassC50~20000.
02~0.
03HydraulicStructureofClassAwithoutwater5010000.
055.
SUMMARYOnthebasisofseismicactivityintheseaareasofChina,structuralcharacteristicsofoffshoreplatform,seismicdesigngoal,andtheseismicfortificationexperiencesofrelatedengineering,werecommendthattheseismicfortificationlevelofstrengthdesigntakesareturnperiodof200years,andthatofdeformationdesigntakesareturnperiodof3000yearsforoffshoreplatformsinChina.
ThereturnperiodsrecommendinthispaperareonlyusedinthecomparisonbetweenChineserelatedCodes,hasnotbeenappliedinstructuralanalysisofoffshoreplatform,alsothereliabilityanalysisofthedesignhasnotbeendonefordifferenceplatformstructures.
Thereisstillalongwaytogobeforetheconstitutionofseismiccodeforoffshoreplatforms,andmanyresearchesshouldbedoneinfuture.
ReferenceLuYue-jun,PengYan-ju,TangRong-yu.
(2003).
Engineeringseismicproblemsoftheoffshoreoilplatforms.
ProgressinGeophysics18:4,662-665.
AmericanPetroleumInstitute,RP2A-WSD.
(2002).
Planning,Designing,andConstructingFixedOffshorePlatforms-WorkingStressDesign.
Houston:AmericanPetroleumInstitute.
ChinaStateBureauofQualityandTechnicalSupervision.
(2005).
ChinaStandardGB17741-2005.
StandardsPressofChina.
ChinaStateBureauofQualityandTechnicalSupervision.
(1998).
GB17503-1998.
StandardsPressofChina.
MinistryofConstructionP.
R.
China.
(2001).
GB50011-2001.
ChinaBuildingIndustryPress.
XieLiliZhangXiaozhiZhouYongnian.
(1996).
OntheDesignEarthquakeLevelforearthquakeResistantWorks.
EarthquakeEngineeringandEngineeringVibrationl6:1,1-18.
WangZhongchang.
(2005).
Thediscussiononsomeproblemsinanti-seismicanalysisforfixedplatform.
ChinaOffshoreOilandGas17:6,421-423PengYanju,LuYuejun,TangRongyu.
(2006).
ResearchontheseismicfortificationlevelforoffshoreplatforminBohaiSeaandadjacentareas,ActaSeismologicaSinica,27:6,647-655WeiWei.
(2004).
Researchonseismicdamagestatesofjacketoffshoreplatformstructures.
AdissertationofOceanUniversityofChinaforDoctoralDegreePengYanju,LuYuejun,TangRongru,etal.
(2007).
ResearchonseismicdesignparametersandearthquakeresistantlevelforanoilfieldplatforminBohaiSea.
Journalofearthquakeengineeringandengineeringvibration.
27:4,8-14
net2AssociateResearcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,China3Researcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,China4AssociateResearcher,InstituteofCrustalDynamics,ChinaEarthquakeAdministration,Beijing,ChinaABSTRACT:ThecurrentseismicdesigncodecommonlyusedintheworldisRP2A-WSDcompiledbyAmericanPetroleumInstitute,thereisstillnospecificseismicdesigncodeforoffshoreplatformsinChina.
Inthispaper,abriefintroductionofRP2A-WSDcodeisgivenatfirst,andthecomparisonbetweentheseismicfortificationlevelsofRP2A-WSDandthatofChineseGB17503-1998andGB50011-2001suggeststhatthelevelsofChineseCodesareoverestimated.
Secondly,theseismicdamagesandanti-seismicdesignrequirementsofoffshoreplatformsarediscussedinviewoftheirstructuralcharacteristics.
Onthebasisoftheanalysisabove,summingupthefactors,suchastheseismicactivityinthewatersofChina,structuralcharacteristicsofoffshoreplatform,seismicdesigngoal,andtheseismicfortificationexperiencesofrelatedengineering,werecommendthattheseismicfortificationlevelofstrengthdesigntakeareturnperiodof200years,andthatofdeformationdesigntakeareturnperiodof3000yearsrespectivelyforoffshoreplatformsinChina.
Finally,thecomparisonwithotherChineseCodesofrelatedindustriesshowsthattherecommendedfortificationlevelissafeandrational.
KEYWORDS:OffshorePlatform,SeismicDesign,SeismicFortificationLevel,ReturnPeriod0INTRODUCTIONSincethe80soflastcentury,theexploitationofoceanoilgainedverygreatprogressinChina,Over100offshoreoilplatformshavebeenbuiltinBohai,Huanghai,EastChinaSeaandSouthChinasea,another100willbeerectedinthecoming5years.
Thedamageofoffshoreoilplatformsmaycauseseveresecondarydisasters,andtheseismicityintheseasofChinaisrelativelyhigh,thus,theseismicdesignproblemofoffshoreplatformshasattractedconsiderableattention(LuYuejun,etal,2003).
FixedplatformsaremostlyusedintheexploitationofoceanoilinChina,theirlifespanisratherlong,commonlyismorethan15years.
Duringthelifespantheplatformcannotmove,andmustsupportsomeenvironmentalloads,includingwind,wave,current,ice,earthquakeandsoon.
Thestructuraldamagewillcauseseriouspersonnelcasualty,equipmentloss,oilproductionstop,andenvironmentalpollution.
Inplatformdesigning,earthquakeloadshouldbeimposedontheplatformasaseparateenvironmentalloadingcondition,otherenvironmentalloadsshouldbecombinedinamannerconsistentwiththeprobabilityoftheirsimultaneousThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China2occurrenceduringtheloadingconditionbeingconsidered.
Andearthquakeloadisseriouslydestructive,andcannotbepredicted.
Therefore,theseismicanalysismustbetakenintoaccountinstructuraldesigning.
NospecificseismicdesigncodehasyetbeendraftedforoffshoreplatformsinChinabecauseofinsufficientknowledgeontheseismiccharacteroftheseaareas.
ThecurrentseismicdesigncodecommonlyusedintheworldisRP2A-WSDcompiledbyAmericanPetroleumInstitute(AmericanPetroleumInstitute,2002).
Seismicfortificationistoprovideresistancetoearthquakeforengineeringstructures.
Thefollowingthreefactorsshouldbetakenintoconsiderationinthedeterminationoftheseismicfortificationofengineeringstructures,socialeconomiclevel,seismichazardandimportanceofstructures.
Thekeycontentoftheseismicfortificationisseismiclevelandgrade(XieLili,etal,1996).
Inthispaper,acomparisonbetweentheseismicfortificationlevelsofRP2A-WSDandthatofChineseGB17503-1998andGB50011-2001iscarriedout,anditisregardthatthelevelsofChineseCodesareoverestimated.
Summingupthefactors,suchasseismicactivityintheseasofChina,structuralcharacteristicsofoffshoreplatforms,seismicdesigngoal,andtheseismicfortificationexperiencesofrelatedengineering,werecommendthattheseismicfortificationleveltakesareturnperiodof200yearsforstrengthdesign,and3000yearsfordeformationdesignrespectivelyforoffshoreplatformsinChina.
Finally,thecomparisonwithotherChineseCodesofrelatedindustryshowsthattherecommendedfortificationlevelissafeandrational.
1.
THECURRENTSEISMICDESIGNCODEOFOFFSHOREPLATFORMANDEXISTINGPROBLEMS1.
1.
ThecurrentseismicfortificationcodeThereisnoseismicdesigncodeofoffshoreplatforminChinaatpresent.
TheGB17503-1998suggeststhatthelevelsofthestrengthanddeformationdesigntake10%and0.
5%probabilitiesofexceedancein50years.
The10%and0.
5%probabilitiesofexceedancein50yearscorrespondtoareturnperiodof475and10000yearsrespectively.
Butthiscodedoesnotgiveacorrespondinginterpretationoftheiritems.
BasedontheseismicactivityandseismicriskmapinthecostalwatersoftheUnitedStates,RP2A-WSDiscompiledbyAmericanPetroleumInstitute(AmericanPetroleumInstitute,2002).
Thecodestatesthattwolevelsofgroundmotionintensityduetomoderateandrareintenseearthquakesinthelifespanofoffshoreplatformshouldbeconsideredinstrengthdesignanddeformationdesignrespectively.
Thedesignseismiclevelmeetsthestrengthrequirements,thatis,toprovideresistancetomoderateearthquakeswithoutsignificantstructuraldamage,arecurrenceintervalof200yearsforpermanentstructuresinSouthernCaliforniaisrecommended.
Therareintenseearthquakeistheinputfordeformationdesign,nolifelossandsignificantenvironmentpollutionisallowedatthislevel,structuraldamageislikelytooccur,buttheprovisionsareintendedtopreventcollapseoftheplatform,thereturnperiodmaybeseveralhundredtoafewthousandyears.
Thefirstlevelprovidesthegroundmotioninputfortheelasticdesignofthestructure,andthesecondlevel,ifitisdeemednecessarytoanalyzethestructureforrareintenseearthquakes,providesthegroundmotioninputfortheThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China3analysis.
1.
2.
ExistingproblemsTheprovisionsandmethodofRP2A-WSDCodeareusedinseismicanalysisoftheplatform,namely,strengthdesignanddeformationdesignarecarriedoutrespectively(WangZhongcang,2005).
ButtheseismicfortificationlevelsareaccordingtoGB50011-2001(MinistryofConstructionP.
R.
China,2001)andGB17503-1998.
TheseCodesareinconsistent.
AcomparisonofseismicityismadebetweenSouthernCaliforniaandBohaiSeabyPengYanjuetal(2006),whichshowsthattheearthquakenumber,strainenergyrelease,andPGAinSouthernCaliforniaareallhigherthanthatinBohaianditsadjacency.
TheoilfieldPL19-3isajointventureprojectofChinaandtheUnitedStates,anddesignedinlightofAPIRP2A-WSDcode.
AccordingtoAPIRP2A-WSDandtheChineseCodeGB17503-1998,PengYanjuetal(2007)obtainedtheseismicdesignparametersattheoilfieldsite,thePGAatthestrengthdesignlevelanddeformationdesignlevelis252cms-2and570cms-2respectivelybytheChineseGB17503-1998,andthatis162cms-2and333cms-2respectivelybyAPIRP2A-WSDcode,theratiois1.
55and1.
71times.
Therefore,Chinaisadevelopingcountrywithlimitedfinanceandresources,thereisnoneedtoadoptaseismicfortificationlevelofoffshoreplatformhigherthanthatindevelopedcountries.
2.
STRUCTURALCHATACTERISTICSOFTHEOFFSHOREPLATFORMANDENGINEERINGSEISMICPROBLEMS2.
1.
AbriefintroductionofthestructureofoffshoreplatformThestructuralformsoffixedplatformincludejacket,gravity,tower,andsoon.
Thejacketplatformisthemostpopularstructuralformintheexploitationofoceanoil(gas),andconsistofthefollowing:redundantweldedtubularspaceframeservesasthemainstructuralelementoftheplatform,transmittinglateralandverticalforcestothefoundation,pilespermanentlyanchortheplatformtotheoceanfloor,andcarrybothlateralandverticalloads,asuperstructureprovidingdeckspaceforsupportingoperationalandotherloads.
Theintrinsicperiodofthestructureis1to3sdependingonitssize,weight,pilesdeepness,andwaterdepth.
2.
2EngineeringseismologicalproblemsoftheoffshoreplatformAsformostothertypesoffacilities,itisnotwarrantedandnoteconomicaltodesignoffshoreplatformtoprecludeanydamageforthemostsevereearthquakegroundshakingpossible.
Theactualprincipleisintendedtoprovideresistancetomoderateearthquakes,whichhaveareasonablelikelihoodofnotbeingexceededduringThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China4thelifespanoftheplatform.
Itisneededtoconstituteascientificandreasonableseismicdesigncodeanddetermineseismicfortificationlevel.
Whiledesigningoffshoreplatform,earthquakeforcesaretakenintoaccounttoensurethestructureatlinearelasticityinthelife.
Oncetherearesomestructuralmemberswhicharebendedanddestroyed,thestructureisregardedasreachingtheutmostcarryingcapacityandcannotbeusednormally.
Accordingtotheponderanceofthestructuralmembersinthewholestructure,thedestructivestateofplatformisdividedintotworanksbyWeiWei(2004):(1)Thenon-importancedestructivestate,thisistheutmostbeforethestructuregoesintoplasticstate,butthestructureisstillatlinearelasticity.
Hereon,theplatformcanstillbeused,orcanberepaired.
(2)Thelocalcollapsestate,thisstateisattheutmostofcarryingcapacity,thestructureoritsmembersreachthebiggestallowablecarryingfunction.
Theplatformcannotbeusedanyfurther,somestructuralmembersorthewholestructureundergomortaldeformation,butwithoutcollapsing.
Thestudyresultprovidedatheoreticalbasisforthedeterminationofseismicfortificationgoal.
Theseismicinfluenceontheplatformstructureismostlybroughtbythebasemovement,tofulfillseismicanalysis,someseismicparametersatthebasesitearerequired,includingthepeakvalues,responsespectra,andtimehistoryofthegroundmotion.
Theparticularityofengineeringseismicproblemsoftheoffshoreplatformisthelongperiodgroundmotion,theoffshoreplatformisalongperiodstructure,atthesametime,thereciprocityofplatformandwater(appendedmass)alsomakestheresonanceperiodlonger.
Commonly,themajorityofconstructsandstructuresusethepeakvaluesofseismicaccelerationastheindexofseismicanalysis,andtheplatform,whichislongperiodstructure,shouldusevelocityordisplacement,butthecurrentseismicanalysisoftheplatformstillusesaccelerationbecauseofinsufficiencyofengineeringseismicstudy.
LuYuejunetal(2003)discussedsomeengineeringseismicproblemsofplatformindetail,includingscenarioearthquake,longperiodgroundmotion,andsoon.
3.
DETERMINATIONOFSEISMICFORTIFICATIONLEVELFORLEVELFOROFFSHOREPLATFORM3.
1.
DeterminationofdesignruleBasedontheanalysisofengineeringseismicproblemsoftheoffshoreplatforminabovesection,seismicfortificationforplatformmayhaveananalogywithsomespecialstructureinland,suchasTVtransmissiontower,oversizebridge,greatdamandsoon.
Referringtotheseismicfortificationexperiencesofrelatedengineering,thefollowingfactorsshouldbetakenintoconsiderationinthedeterminationoftheseismicfortificationofplatform.
(1)TomeettheChineseandforeigncurrentcodePresently,inordertofittothedevelopingtrendofinternationalanti-seismictechnology,theseismicdesignThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China5thinkingistransferringfromsafetyfactortoreliabilitydesigninChina.
Sotheseismicfortificationlevelbasedonprobabilityisneededtomeetthedemandofreliabilitydesign.
(2)Considerationoffortificationclassificationandmultiple-stagedesignReliabilitydesignmakesthestructuretomeetthedemandofspecificultimatestatebycontrollingthemajorconditions.
AccordingtoactualengineeringstructuredesigninChina,theultimatestatemaybedividedintothreestates:serviceabilitylimit,ultimatecarryingcapacity,andultimatedeformation.
Theengineeringstructuredesignismadeaccordingtocarryingcapacityforeachstate,andtheseismicfortificationisgivenbasedonthedifferentultimatecarryingcapacity.
Forexample,GB50011-2001adoptsthreeseismicfortificationlevelsandtwo-stagedesign.
(3)KeeptheconsistencywiththestatepolicyofseismicfortificationThestateseismicdesignpolicyrestrainsthefortificationlevel.
Thegroundmotionparameters(e.
g.
peakaccelerationandresponsespectrum)specifiedinthepresentcodessuchasGB50011-2001,arealllowerthanobservationvalues.
Thereforetheseismicfortificationlevelforoffshoreplatformsshouldnotbetooconservative,andthereisnoneedtotakeahighervaluethanthatindevelopedcountries.
3.
2Determinationofseismicfortificationlevelforoffshoreplatform(1)DesignreferenceperiodDesignreferenceperiodliesonthelifespanoffacilities.
Becausethedurationofexploitationofoceanoil(gas)isabout30years,asuitabledesignreferenceperiodofoffshoreplatformis30years.
(2)SeismicfortificationgoalThedestructivestateofplatformisdividedintotworanks:thenon-importantdestructionstateandthelocalcollapsestate.
Hereby,consideringtheexistingdesignrule,theseismicfortificationgoalforoffshoreplatformisdeterminedaccordingtotwolevelsduetofrequentandrareearthquakesduringthelifespan.
Thefrequentearthquakelevelmeetsthestrengthrequirements,thatis,toprovideresistancetofrequentlyencounteredearthquakeswithoutsignificantstructuraldamage,theplatformmaintainserviceability,orcanberepaired.
Therareearthquakeistheinputfordeformationdesign,structuraldamageislikelytooccur,buttheprovisionsareintendedtopreventcollapseofthewholestructure,nolifelossandsignificantenvironmentpollutionisallowedatthislevel.
(3)Thefrequent-earthquakelevelThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China6Thefrequentearthquakescorrespondtoearthquakeforcesunderserviceabilitylimitdesignstate.
Forcommonconstructandstructure(theclassC),thedesignreferenceperiodis50years,thefrequentearthquakeleveltakes63%probabilitiesofexceedancein50years,correspondingtoareturnperiodof50years.
Offshoreplatformisanimportantengineeringstructure,consequentlytheseismicfortificationlevelshouldbehigherthanthatforcommonconstructandstructure.
AccordingtotherecommendedvalueforSouthernCaliforniainRP2A-WSD,thestrengthdesignlevelforoffshoreplatformisareturnperiodof200years,correspondingto14%probabilitiesofexceedancein30years.
Theintensityatfrequent-earthquakelevelforcommonstructuresis1/3ofmediumearthquakes(returnperiod475years).
Accordingtostatisticof128resultsofseismicsafetyassessmentthroughoutthewholecountry,earthquakeforcesatreturnperiodof200yearsis2/3ofreturnperiodof475years,therefore,thefrequent-earthquakelevelforoffshoreplatformtakesareturnperiodof200years,whichcorrespondsto2timesthestrengthatthefrequent-earthquakelevelforclassCstructuresandisequivalenttothatforclassAstructures.
(4)TherareintenseearthquakelevelTherareintenseearthquakescorrespondtoearthquakeforcesinutmostdeformationdesign.
Inthedesignreferenceperiodofplatform,thestructuresuffersfromsuchearthquakeforcesbyaccident,thestructureislikelytoincurthebiggestdeformation,butcankeepoverallstabilitywithoutcollapse.
Thelevelofrareintenseearthquaketakes2~3%probabilityofexceedancein50yearsforclassCstructures,correspondingtoareturnperiodof1500to2500years,thatforclassAstructurestakes2~3%in100years,correspondingtoareturnperiodof3000to5000years.
Usuallythedesignreferenceperiodofoffshoreplatformsis30years,becausethedamageofplatformsmaycausegreateconomiclossandenvironmentpollution,itisappropriatethatthedeformationdesignleveltakes1%in30years,correspondingtoareturnperiodof3000,whichisalreadyhigherthanthatforclassAstructuresandapproximatestotheupperlimitinRP2A-WSD.
Accordingtotheanalysisabove,andtakingRP2A-WSDasareference,itissafeandrationaltotaketheearthquakeswithareturnperiodof200yearsand3000yearsforoffshoreplatformsinChinaasthestrengthanddeformationdesignlevelrespectively.
4.
ACOMPARISONWITHRELATEDCODES4.
1.
Acomparisontothecodesofoil/gasandotherchemicalstructuresOil/gasandotherchemicalstructuresarelargeandcomplexengineeringsystems,includingcomprehensivestation,pipeline,oilstorage,chemicalstructure,andsoon.
Incaseofearthquakedemolishment,thestructuraldamagewillcauseseriouseconomicallossandenvironmentalpollution,sotheseismicproblemsaretakenseriously.
Basedonthestructuralcharacteristicsandimportance,oil/gasandotherchemicalstructuresaredividedintothreeclasses:A,B,andC;theoffshoreplatformisaffirmedasclassAoftheutmostimportance.
Werecommendthattheseismicfortificationlevelofstrengthdesigntakesareturnperiodof200years,andthatThe14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China7ofdeformationdesigntakesareturnperiodof3000yearsrespectively,thereturnperiodisthelongestinoil/gasandchemicalindustry.
Wemayregardthattheseismicfortificationmeasuresforoffshoreplatformsarestricter,itsseismicriskissmaller.
Table1TheseismicfortificationlevelforoilandgasstructuresClassStructureReferenceperiod(a)Returnperiodforfrequentearthquakes(a)Returnperiodforrareintenseearthquakes(a)AOffshorePlatform302003000BLargecomprehensivestation,importantsectionofoil&gaspipeline,largeoilstructureandimportantchemicalstructure50100300030502500COilgasandotherchemicalstructuresbesidesClassA&B50502500303015004.
2.
ComparisonwithseismicfortificationlevelsofrelevantindustriesBecausetheseismicdesignideavariesindifferentindustrialfields,itisobviouslydifficulttocomprehensivelycomparethedifferencebetweentheirseismiclevels.
Therefore,onlythoseindustrialdepartments,whichhavethesameseismicdesignideaandsimilarseismicfortificationgoal,areselectedtocompare;hereweemphasizeacomparisonofthereturnperiodofrareearthquakebetweendifferentstructures.
Inordertorationallyreflectthedifferenceofseismicfortificationforstructureswithdifferentreferenceperiodandreturnperiod,weconvertreturnperiodtoprobabilityofexceedance(PT)inreferenceperiod,then(PT)canindicatetherelativeseismicriskinthereferenceperiod.
Table2isthedeformationdesignlevelofdifferentstructures.
Thedatashowsthatthereferenceperiodofoffshoreplatformsisrelativelyshort,theprobabilityofexceedanceofrareearthquaketakes0.
01inthereferenceperiod.
Itsseismiclevelisjustlowerthanthatfornuclearpowerstation,andmatchesuptothatfortheThreeGorgeDam.
Thereforeareturnperiodof3000yearsofrareearthquakeforoffshoreplatformissafe.
Table2ThedeformationdesignlevelofdifferentstructuresStructureReferenceperiod(a)RareearthquakeReturnperiod(a)PTOffshoreplatform3030000.
01Nuclearplant40100000.
004ThreeGorgeDam100100000.
01HydraulicstructuresofClassAreservingwater10050000.
02BuildingsandStructuresofClassA1003000~50000.
02~0.
03Large-scaleBridge10033000.
03The14thWorldConferenceonEarthquakeEngineeringOctober12-17,2008,Beijing,China8TelevisionTowerofClassA10020000.
05BuildingsandStructuresofClassB5025000.
02BuildingsandStructuresofClassC50~20000.
02~0.
03HydraulicStructureofClassAwithoutwater5010000.
055.
SUMMARYOnthebasisofseismicactivityintheseaareasofChina,structuralcharacteristicsofoffshoreplatform,seismicdesigngoal,andtheseismicfortificationexperiencesofrelatedengineering,werecommendthattheseismicfortificationlevelofstrengthdesigntakesareturnperiodof200years,andthatofdeformationdesigntakesareturnperiodof3000yearsforoffshoreplatformsinChina.
ThereturnperiodsrecommendinthispaperareonlyusedinthecomparisonbetweenChineserelatedCodes,hasnotbeenappliedinstructuralanalysisofoffshoreplatform,alsothereliabilityanalysisofthedesignhasnotbeendonefordifferenceplatformstructures.
Thereisstillalongwaytogobeforetheconstitutionofseismiccodeforoffshoreplatforms,andmanyresearchesshouldbedoneinfuture.
ReferenceLuYue-jun,PengYan-ju,TangRong-yu.
(2003).
Engineeringseismicproblemsoftheoffshoreoilplatforms.
ProgressinGeophysics18:4,662-665.
AmericanPetroleumInstitute,RP2A-WSD.
(2002).
Planning,Designing,andConstructingFixedOffshorePlatforms-WorkingStressDesign.
Houston:AmericanPetroleumInstitute.
ChinaStateBureauofQualityandTechnicalSupervision.
(2005).
ChinaStandardGB17741-2005.
StandardsPressofChina.
ChinaStateBureauofQualityandTechnicalSupervision.
(1998).
GB17503-1998.
StandardsPressofChina.
MinistryofConstructionP.
R.
China.
(2001).
GB50011-2001.
ChinaBuildingIndustryPress.
XieLiliZhangXiaozhiZhouYongnian.
(1996).
OntheDesignEarthquakeLevelforearthquakeResistantWorks.
EarthquakeEngineeringandEngineeringVibrationl6:1,1-18.
WangZhongchang.
(2005).
Thediscussiononsomeproblemsinanti-seismicanalysisforfixedplatform.
ChinaOffshoreOilandGas17:6,421-423PengYanju,LuYuejun,TangRongyu.
(2006).
ResearchontheseismicfortificationlevelforoffshoreplatforminBohaiSeaandadjacentareas,ActaSeismologicaSinica,27:6,647-655WeiWei.
(2004).
Researchonseismicdamagestatesofjacketoffshoreplatformstructures.
AdissertationofOceanUniversityofChinaforDoctoralDegreePengYanju,LuYuejun,TangRongru,etal.
(2007).
ResearchonseismicdesignparametersandearthquakeresistantlevelforanoilfieldplatforminBohaiSea.
Journalofearthquakeengineeringandengineeringvibration.
27:4,8-14
- risk263企业邮箱设置相关文档
- 企业邮箱合同书
- 证券代码:002596
- 审计263企业邮箱设置
- 公告编号:2019-006
- 目录法界要闻】
- 企业263企业邮箱设置
日本美国站群服务器raksmart站群新增,限量低至月1.99美元
RAKsmart 商家八月份的促销活动今天更新。基本上和上个月的产品套餐活动差不多的，不过也是有简单的微调。对于RAKsmart商家还是比较了解的，他们家产品虽然这两年增加多个机房，以及在VPS主机方案上有丰富的机房和调整到一些自营机房，他们家的策划能力还是有限，基本上每个月的套餐活动都差不多。RAKsmart 在八月份看到有新增香港高防服务器可选，最高100GB防御。同时原来上个月缺货的日本独立...
hosthatch：14个数据中心15美元/年
hosthatch在做美国独立日促销，可能你会说这操作是不是晚了一个月？对，为了准备资源等，他们拖延到现在才有空，这次是针对自己全球14个数据中心的VPS。提前示警：各个数据中心的网络没有一个是针对中国直连的，都会绕道而且ping值比较高，想买的考虑清楚再说！官方网站：https://hosthatch.com所有VPS都基于KVM虚拟，支持PayPal在内的多种付款方式！芝加哥（大硬盘）VPS5...
亚州云-美国Care云服务器，618大带宽美国Care年付云活动服务器，采用KVM架构，支持3天免费无理由退款！
官方网站：点击访问亚州云活动官网活动方案：地区：美国CERA（联通）CPU：1核（可加）内存：1G（可加）硬盘：40G系统盘+20G数据盘架构：KVM流量：无限制带宽：100Mbps（可加）IPv4：1个价格：￥128/年（年付为4折）购买：直达订购链接测试IP：45.145.7.3Tips：不满意三天无理由退回充值账户！地区：枣庄电信高防防御：100GCPU：8核（可加）内存：4G（可加）硬盘：...
263企业邮箱设置为你推荐
-
根目录什么叫固件？什么叫根目录？可以发外链的论坛可以发外链的论坛有那些?51自学网站网上自学网站有哪些？最好是免费的，我想学习网页设计邮箱打不开怎么办我的邮箱打不开怎么办二叉树遍历怎么正确理解二叉树的遍历机械键盘轴机械键盘什么轴好，机械键盘轴有几种小米手柄小米手柄和飞智手柄哪个好？系统分析员一个优秀的系统分析师应该具备哪些方面的知识和素质?网站优化方案网站优化方案怎么写？发邮件怎么发怎样发邮件？