钢桥抗震设计

GUIDESPECIFICATIONSFORSEISMICDESIGNOFSTEELBRIDGESFirstEditionStateofCaliforniaDepartmentofTransportationDecember2001GUIDESPECIFICATIONSFORSEISMICDESIGNOFSTEELBRIDGES–FIRSTEDITIONDecember2001iiTABLEOFCONTENTSPREFACEiDEFINITIONSivNOTATIONvii1.INTRODUCTION11.1.Scope11.2.ReferencedSpecificationsandStandards11.3.BridgeCategories21.4.SeismicPerformanceCriteria22.GENERALPROVISIONS32.1.LoadsandLoadCombination32.2.SeismicDesignAcceptanceCriteria32.2.1.StructuralComponentClassification32.2.2.DamageLevels,StrainandDuctilityinStructuralSteel62.2.3.Displacements82.2.4.Forces83.STRUCTURALANALYSIS93.1.AnalysisMethods93.1.1.General93.1.2.Moment-CurvatureAnalysis113.2.StructuralModeling123.2.1.General123.2.2.Materials133.2.3.Geometry133.2.4.EffectiveSectionProperties154.DESIGNREQUIREMENTS164.1.Proportions164.2.Materials174.3.EffectiveNetSections184.4.EffectiveLengthofCompressionMembers184.5.LimitingWidth-ThicknessRatios194.6.LimitingSlendernessParameters194.7.Built-upMembers234.8.ShearConnectors244.9.RestrainingComponents264.10.Welding28GUIDESPECIFICATIONSFORSEISMICDESIGNOFSTEELBRIDGES–FIRSTEDITIONDecember2001iii5.DUCTILESEISMICRESISTINGSYSTEMS295.1.DuctileSubstructureSystems295.1.1.MomentResistingFrames295.1.2.ConcentricallyBracedFrames325.1.3.EccentricallyBracedFrames345.2.DuctileEndCrossFramesandDiaphragms375.2.1.General375.2.2.EffectiveColumnArea385.2.3.BoundaryConditionsofEffectiveColumns385.3.IntegralConnectionSystems395.3.1.General395.3.2.SteelGirderSuperstructures395.3.3.ConcreteColumns405.3.4.ConcreteBentCapBeams405.3.5.ConcreteEndDiaphragmsatAbutments416.DUCTILECOMPONENTS426.1.General426.2.TensionMembers426.3.CompressionMembers426.4.FlexuralMembers436.5.MembersSubjectedtoCombinedFlexureandAxialForce437.CAPACITY-PROTECTEDCOMPONENTS447.1.General447.2.TensionMembers447.3.CompressionMembers447.4.FlexuralMembers457.5.MembersSubjectedtoCombinedFlexureandAxialForce457.6.ConnectionsandSplices457.6.1.General457.6.2.BracingConnections467.6.3.Beam-to-ColumnConnections477.6.4.GussetPlateConnections487.7.FastenersandHoles547.8.AnchorRodsandAnchorageAssemblies54APPENDICESA.STRESS-STRAINRELATIONSHIPSFORSTRUCTURALSTEEL56B.EFFECTIVESECTIONPROPERTIES58C.YIELDSURFACEEQUATIONSFORDOUBLYSYMMETRICALSTEELSECTIONS63D.DESIGNFORMULAS(U.S.UNITS)65E.LATERALSTIFFNESSOFGIRDERBRIDGESINTRANSVERSEDIRECTION67F.REFERENCES71GUIDESPECIFICATIONSFORSEISMICDESIGNOFSTEELBRIDGES–FIRSTEDITIONDecember2001ivDEFINITIONSThefollowingdefinitionsaresupplementaltothedefinitionsgivenintheCaltransSeismicDesignCriteriaVersion1.2(Caltrans2001)andtheCaltransBridgeDesignSpecifications(Caltrans2000).BlockShearRupture–Afailurephenomenonorlimitstateforaboltedwebconnectionofcopedbeamsoranytensionconnectionbythetearingoutofaportionofaplatealongthecenterlinesoftheboltholes.Theblockshearrupturestrengthcombinestensilestrengthononeplaneandshearstrengthonaperpendicularplane.BracingMember-Amemberintendedtobraceamainmemberorpartthereofagainstlateralmovement.Capacity-ProtectedComponent-Acomponentexpectedtoexperienceminimumdamageandtobehaveessentiallyelasticduringthedesignearthquakes.Connections-Acombinationofjointsusedtotransmitforcesbetweentwoormoremembers.ConcentricallyBracedFrame(CBF)-Adiagonallybracedframeinwhichallmembersofthebracingsystemaresubjectedprimarilytoaxialforces.DesignEarthquake–EarthquakeloadsrepresentedbyAccelerationResponseSpectrum(ARS)curvesspecifiedinCaltransSDCorsite-specificARScurves.DesignStrength-Resistance(axial/shearforce,moment,asappropriate)providedbystructuralcomponents,theproductofthenominalstrengthandtheresistancefactor.DisplacementDuctility-Ratioofultimate-to-yielddisplacement.DuctileComponent–AcomponentexpectedtoexperiencerepairabledamageduringtheFEEandsignificantdamagebutwithoutfailureduringtheSEE.Ductility-Ratioofultimate-to-yielddeformation.EccentricallyBracedFrame(EBF)-Adiagonallybracedframethathasatleastoneendofeachbracingmemberconnectedtoalink.ExpectedNominalStrength-Nominalstrengthofacomponentbasedonitsexpectedyieldstrength.FunctionalEvaluationEarthquake(FEE)-Alowerleveldesignearthquakethathasrelativelysmallmagnitudebutmayoccurseveraltimesduringthelifeofthebridge.Itmaybeassessedeitherdeterministicallyorprobabilistically.ThedeterminationofthiseventistobereviewedbyaCaltrans-approvedconsensusgroup.GUIDESPECIFICATIONSFORSEISMICDESIGNOFSTEELBRIDGES–FIRSTEDITIONDecember2001vJoint–Anareawherememberends,surfaces,oredgesareattachedbyplates,fastenersandwelds.Link-InEBF,thesegmentofabeamthatislocatedbetweentheendsoftwodiagonalbracesorbetweentheendofadiagonalbraceandacolumn.Underlateralloading,thelinkdeformsplasticallyinsheartherebyabsorbingenergy.Thelengthofthelinkisdefinedasthecleardistancebetweentheendsoftwodiagonalbracesorbetweenthediagonalbraceandthecolumnface.MaximumCredibleEarthquake(MCE)-Thelargestearthquakethatiscapableofoccurringalonganearthquakefault,basedoncurrentgeologicinformationasdefinedbythe1996CaltransSeismicHazardMap.MomentResistingFrame(MRF)-Aframesysteminwhichseismicforcesareresistedbyshearandflexureinmembers,andconnectionsintheframe.