简介：Accurateestimatesofductilitydemandsonbuckling-restrainedbracedframes(BRBFs)arecrucialtoperformance-baseddesignofBRBFs.AnanalyticalstudyontheseismicbehaviorofBRBFshasbeenconductedattheATLSSCenter,LehighUniversitytoprepareforanupcomingexperimentalprogram.TheanalysisprogramDRAIN-2DXwasusedtomodelaone-bay,four-storyprototypeBRBFincludingmaterialandgeometricnonlinearities.Thebucklingrestrainedbrace(BRB)modelincorporatesbothisotropicandkinematichardening.NonlinearstaticpushoverandtimehistoryanalyseswereperformedontheprototypeBRBF.PerformanceobjectivesfortheBRBsweredefinedanduscdtoevaluatethctime-historyanalysisresults.ParticularemphasiswasplacedonglobalductilitydemandsandductilitydemandsoatheBRBs.Thesedemandswerecomparedwithanticipatedductilitycapacities.Theanalysisresults,alongwithresultsfromsimilarpreviousstudics,areusedtoevaluatetheBRBFdesignprovisionsthathavebeenrecommendedforcodificationintheUnitedStates.ThcresultsshowthatBRBmaximumductilitydemandscanbeashighas20to25.ThesedemandssignificantlyexceedthoseanticipatedbytheBRBFrecommendedprovisions.Resultsfromthestaticpushoverandtimehistoryanalysesareusedtodemonstratewhytheductilitydemandsexceedthoseanticipatedbytherecommendedprovisions.TheBRBqualificationtestingprotocolcontainedintheBRBFrecommendedprovisionsisshowntobeinadequatebecauseitrequiresonlyamaximumductilitydemandofatmost7.5.Modificationstothetestingprotocolarerecommended.

简介：Thedynamictorsionalbucklingandpost-bucklingofelasto-plasticcircularcylindricalshellisstudied.BytheusageoftheBodner-Partomconstitutiverelation,thepresentvisco-plasticproblemistreat-edasanorthotropicelasticproblem.Basedonthenonlinearlargedeflectionshelltherory,thegoverningdynamicbucklingequationissolvedbytheRunge-Kuttamethod,andthecriticalbucklingstressisdeter-minedbytheB-Rcriterion.Thepresentpaperismainlyfocusedontheimperfectionsensitivity,thestrainratesensitivity,andthedynamicpost-bucklingcharactersfortheshellloadeddynamicallywithaconstantshearstrainrate.Numericalresultsshowthatthecriticalshearstressandimperfectionsensitivitywillin-creasewiththeincreaseofstrainrate.Itisfoundthattheelasticbucklingstressismoresensitivetoimperfectionthanthevisco-plasticbuckling.Thepresentresearchalsorevealssomedynamicpost-bucklingcharactersforthecylindricalshell,anditisshownthattheshellwillvibra

简介：-Thispaperadoptsapproximateformulasforresidualstressescausedbycoldbendingforplateswithstress-straincurveforma=Kn.Atypicaldistributionofthelongitudinalresidualstressduetoweldingisalsoassumed.Theeffectsofresidualstressduetocoldbendingandweldingonplasticbucklingofaxiallycompressedcylindricalshellsarestudiedbythefiniteelementmethod.

简介：Theimpactbucklingofalaminatedcompositebarisinvestigatedincaseofoneofitsendsmovingduetoaxialimpactcompression.Thegoverningequationsconsideringthefirst-ordersheardeformationeffectarederivedbytheHamiltonprincipleandsolvedbythefinitedifferencemethod.ThecriticalaxialshortnessisdeterminedbytheB-Rcirterion.Thegivenexampleisusedtohighlightthein-fluencesofinitialimperfection,impactvelocity,stresswaveandcoupledstiffness.Itisfoundthattheunsymmetricallylaminatedbarhasaquitedifferentdynamicbucklingbehaviourfromthatofthesymmetricallylaminatedbar.

简介：Inordertostudybucklingpropagationmechanismindeepseapipelines,thecontactbetweenpipeline’sinnerwallsinbucklingprocesswasstudied.Atwo-dimensionalringmodelwasusedtorepresentthepipelineandanonlinearspringmodelwasadoptedtosimulatethecontactbetweeninnerwalls.Basedontheelastoplasticconstitutiverelationshipandtheprincipleofvirtualworktheory,thecouplingeffectofpipeline’snonlinearlargedeformationandwallcontactwasincludedinthetheoreticalanalysiswiththeaidofMATLAB,andtheapplicationscopeofthetheoreticalmodelwasalsodiscussed.Thecalculatedresultsshowthatduringtheloadingprocess,thechangeinexternalpressureiscloselyrelatedtothedistributionofsectionstress,andoncethewallsarecontactingeachother,theexternalpressureincreasesandthenremainsstableafteritreachesaspecificvalue.Withoutfracture,thepipelinesectionwillstopshowingdeformation.Theresultsoftheoreticalcalculationsagreewellwiththoseofnumericalsimulations.Finally,inordertoensurereliabilityandaccuracyofthetheoreticalresults,thecollapsepressureandpropagationpressurewerebothverifiedbynumericalsimulationsandexperiments.Therefore,thetheoreticalmodelcanbeusedtoanalyzepipeline’sbucklingdeformationandcontactbetweenpipeline’sinnerwalls,whichformsthebasisforfurtherresearchonthree-dimensionalbucklingpropagation.

简介：-Thedynamicbucklingofelasto-plasticcylindricalshellsunderaxialfluid-solidimpactisinvestigatedtheoretically.Asimplifiedliquid-gas-structuremodelisgiventoapproximatelyimitatetheproblem.Thebasicequationofthestructureisderivedfromaminimumprincipleindynamicsofelasto-plasticcontinuaatfinitedeformation,andtheflowtheoryofplasticityisemployed.Theliquidisincompressibleandthegasiscompressedadiabatically.Anumberofnumericalresultsarepresentedandthecharacteristicsofthebucklingbehaviorunderfluid-solidimpactareillustrated.

简介：Thispaperaddressesthefreetransversevibrationsofthinsimplysupportednonhomogeneousisotropicrectangularplatesofbilinearlyvaryingthicknesswithelasticallyrestrainededgesagainstrotation.TheGram-Schmidtprocesshasbeenusedtogeneratetwo-dimensionalboundarycharacteristicorthogonalpolynomials,whichhavebeenusedintheRayleigh-Ritzmethodtostudytheproblem.Thelowestthreefrequencieshavebeencomputedforvariousvaluesofnonhomogeneousparameters,thicknessparameters,aspectratioandflexibilityparameters.Acomparisonoftheresultswiththoseavailableintheliteraturehasbeenmade.Three-dimensionalmodeshapesforthespecifiedplatehavebeenpresented.

简介：Inordertotheoreticallystudythebucklepropagationofsubseapipelineswithslip-onbucklearrestors,atwo-dimensionalringmodelwassetuptorepresentthepipelineandanonlinearspringmodelwasadoptedtosimulatethecontactbetweenpipeline’sinnerwallsandbetweenpipeline’souterwallandslip-onbucklearrestor’sinnerwallduringbucklepropagation.Inaddition,somereversespringsareaddedtopreventthewallofleftandrightsidesseparatingfromtheinnerwallofslip-onbucklearrestors.Consideringlargedeformationkinematicsrelationsandtheelastic-plasticconstitutiverelationofmaterial,balanceequationswereestablishedwiththeprincipleofvirtualwork.Thevariationofexternalpressurewithrespecttothecross-sectionalareaofpipelineswasanalyzed,andthelowerboundofthecrossoverpressureofslip-onbucklearrestorswascalculatedbasedonMaxwell’senergybalancemethod.Bycomparingthetheoreticalresultswithexperimentandfiniteelementnumericalsimulation,thetheoreticalmethodisprovedtobecorrectandreliable.