混凝土结构设计原理四PPT课件.ppt

ReinforcedConcretedesign混凝土结构设计原理 WuXiaochunWuhanUniversityofScience TechnologyCivilDepartment2007 7 4FlexuralStrengthofReinforcedConcreteBeams受弯构件正截面承载力计算 4FlexuralStrengthofReinforcedConcreteBeams 4 1Introduction概述 Contents 4 3AnalyzeofFlexuralStrength正截面受弯承载力分析 4 4Rectangularbeamwithtensionreinforcementonly单筋矩形截面受弯承载力计算 4 5Rectangularbeamwithcompressionreinforcement双筋矩形截面受弯承载力计算 4 6FlangedsectionbeamwithtensionreinforcementonlyT型截面受弯承载力计算 4 2StudyonTest正截面受弯性能的试验研究 emphases AnalyzeofFlexuralStrength StudyonTest Rectangularbeamwithtensionreinforcementonly Rectangularbeamwithcompressionreinforcement Flangedsectionbeamwithtensionreinforcementonly 4 1Introduction 4 1 1TypesofflexuralmembersBeamslab Beam Slab 4 1Introduction 4 1 2TypesofsectionRectangularsection 4 1Introduction T section Ringsection 4 1Introduction 4 1 3AnalysisandDesigncontents1 Analysis Momentdiagram Sheardiagram Testbeam Failureofnormalsection verticalcrackinmid spanofbeam MFailureofinclinedsection inclinedcracknearthesupportofbeam M VDeflectionandcrackwidthOther 4 1Introduction 2 Designcontents 1 Flexure normalsection StrengthCalculation正截面受弯承载力计算 M As As Chapter4 2 Shear inclinedsection StrengthCalculation斜截面受剪承载力计算 M V Asv Asb Chapter5 3 ReinforcementDetailing钢筋布置 4 CheckofDeformationandCrackinServiceabilityStage正常使用阶段的裂缝宽度和挠度变形验算 Chapter9 5 DrawConstructionMap绘制施工图 4 2StudyonTest 正截面受弯性能的试验研究 ModelofTest Momentdiagram Sheardiagram Testbeam Behaviorunderload Load DeflectionStress StrainInfluencefactors 4 2StudyonTest DataprocessingofTest Actuallymeasurediagramof Actuallymeasurediagramofdeflection 4 2 1ThreeWorkingStagesofunderreinforcedBeam 4 2 2ThreeFailureModesofNormalsectionofRCBeam 1 Under reinforcedBeamThetensilesteelreachesfybeforetheconcretereachesitsmaximumcapacity tensionfailureorplasticfailureductilefactor fu fy fy 4 2 2ThreeFailureModesofNormalsectionofRCBeam 2 Over reinforcedBeamThecompressionconcretereachesitsmaximumcapacitybeforethetensilesteelreachesfy Bpressionfailureorbrittlefailure 4 2 2ThreeFailureModesofNormalsectionofRCBeam 3 Scarce reinforcedBeamThecompressionconcretedoesnotreachitsmaximumcapacitywhilethetensilesteelgetsitshardenstageorfracture largecrackbrittlefailureNotallowedindesign KEYSThreeWorkingStagesofunderreinforcedBeamThreeFailureModesofNormalsectionofRCBeam1 Under reinforced2 Over reinforced3 Scarce reinforced 4 2StudyonTest 4 3FlexureStrengthCalculationofRCBeam 4 3 1BasicAssumptions1 Aplanesectionbeforebendingremainsaplanesectionafterbending 2 Incalculatingtheultimatemomentcapacityofabeam thetensilestrengthofconcreteisneglected 4 3 1BasicAssumptions 3 Thesteelisassumedtobeuniformlystrainedtothestrainthatexistsatthelevelofthecentroidofthesteel s Es s fy su 0 01 s s 0 0 01 y fy 4 3 1BasicAssumptions 4 Thecompressivestrain stressrelationofconcrete 4 3 1BasicAssumptions 5 Thebondbetweenthesteelandconcreteisprefectandnoslipoccurs Thevalueofn 4 3 2EquivalentStressDistribution CompressiveforceCequalityForceCactionpositionycunchangeable ActualCompressiveStressBlock RectangularEquivalentCompressiveStressBlock equivalentrectangularcompressivestressfactorequivalentrectangularcompressivezonefactor 4 3 2EquivalentStressDistribution 4 3 3BalancedFailure BalancedFailure界限破坏ReferringagaintoFigure iftherewerejustenoughsteeltoputtheneutralaxisatlocationwheretheyieldstraininthesteelandthemaximumconcretestrainof0 0033existedatsametime thecrosssectionwouldbesaidtobebalanced 4 3 3BalancedFailure 2 Balanceddepthofcompressionzoneofsectionxb 相对界限受压区高度仅与材料性能有关 与截面尺寸无关 4 3 3BalancedFailure 3 BalancedMomentMb 界限弯矩 4 BalancedReinforcementRatio 界限配筋率 4 3 4Limitations Avoidingover reinforcedfailureorMaximumreinforcementratio max 4 3 4Limitations 2 AvoidingScarce reinforcedfailureorMinimumreinforcementratio min Concretetensilestrength sdisperse temperature shrinketc Concretecode selectthebiggervalue 4 3FlexureStrengthCalculationofRCBeam KEYSBasicAssumptionsEquivalentStressDistributionBalancedFailureLimitations 4 4Rectangularbeamwithtensionreinforcementonly 4 4 1 BasicEquation 4 4Rectangularbeamwithtensionreinforcementonly 4 4Rectangularbeamwithtensionreinforcementonly 2 LimitationsAvoidingover reinforcedfailureAvoidingscarce reinforcedfailure 3 DesignofSectionWithknow Calculation 4 4Rectangularbeamwithtensionreinforcementonly Begin Read IF T F Over reinforced IF END T F Scare reinforced 4 CheckofSectionWithknow calculation 4 4Rectangularbeamwithtensionreinforcementonly Beginning Read Scare reinforced Over reinforced END T T F F 5 DetailingRequirementsofSectionSectionSimplebeamh 1 8 1 16 L0b 1 2 1 3 5 hSimpleslabh 1 25 1 35 L0LongitudinalmainbarBeam HRB400 HRB335Slab HPB235 HRB335 HRB400 4 4Rectangularbeamwithtensionreinforcementonly Singlerowsofbarinbeam Doublerowsofbarinbeam PainSlab KEYSBasicEquationLimitationsDesignofSectionCheckofSectionDetailingRequirementsofSection 4 4Rectangularbeamwithtensionreinforcementonly 4 5Rectangularbeamwithcompressionreinforcement 1 BrifeItisnoteconomictousesteelbartoresistcompressionforceinabeam Doublyreinforcedsectionisonlyusedinthefollowingcase Whenthesizeofabeamandthegradeofconcretearelimited theflexuralstrengthofthebeamisinsufficientbyusing maxWhenthepossiblecombinationsofexternalloadingrevealthatthebendingmomentmaybechangesign Itcanincreasetheductilityandreducedeflectionofbeamsbyusingcompressionsteel 2 BasicEquation 4 5Rectangularbeamwithcompressionreinforcement 4 5Rectangularbeamwithcompressionreinforcement 3 LimitationsAvoidingover reinforcedfailureAvoidingscarce reinforcedfailureToensureyieldingofcompressionsteelbeforecrashofconcrete 4 DesignofSection 4 5Rectangularbeamwithcompressionreinforcement 1 case1Withknow Calculation Begin Read END Set b TherearethreevariablesAs As andxunknownintwocoupledequations Tominimizethetotalsteelarea wetake b IF Why Itmeansthatistoosufficientthatitcan treachitsyieldstrength 4 DesignofSection 4 5Rectangularbeamwithcompressionreinforcement 2 case2Withknow Calculation Begin IF T A sisinsufficient A srequiredmaybecalculatedascase1 END Read 5 CheckofSectionWithknow Calculation Solution 4 5Rectangularbeamwithcompressionreinforcement Begin Read set KEYSBasicEquationLimitationsDesignofSection Case1 Case2 CheckofSection 4 5Rectangularbeamwithcompressionreinforcement 4 6Flangedsectionbeamwithtensionreinforcementonly 4 6 1 Brife 1 Engineeringpractice 4 6 1 Brife 2 EffectivewidthofT beamBecausethedistributionoflongitudinalcompressivestressinthetopslabisnon uniformthecalculationwidthofslabshouldbelimitedasshowninfigure 4 6 2TwoTypesofT section T sectionoftype1 T sectionoftype2 Limitstatus Design Check T sectionoftype1 T sectionoftype1 T sectionoftype2 T sectionoftype2 4 6 3T sectionoftype1 Limitations isalwayssatisfiedbecauseweusuallyhave topreventbrittlefailure 4 6 4T sectionoftype2 Limitations topreventover reinforcedfailure isalwayssatisfied 4 6 5CalculatingMethod 1 DesignofsectionWithknown Calculate Solution omit 2 CheckofsectionWithknown Calculate Solution omit Analysisofaflangedbeamwithcompressionreinforcement KEYSEffectivewidth