砌体1.ppt
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砌体1.ppt
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教学计划砌体结构12学时梁板结构设计8学时框架结构设计10学时施工图的绘制2学时Masonrystructure(砌体结构)参考书:
砌体结构设计苏小卒主编,同济大学出版社砌体结构的诞生标志着土木工程的诞生l石头与碎石干砌体石头与碎石干砌体l土坯砖土坯砖11000年前年前l烧制砖烧制砖3000年前年前l水泥和水泥砂浆水泥和水泥砂浆19世纪世纪20年代年代l配筋砌体配筋砌体l高强、多孔、薄壁、大块等方向发展高强、多孔、薄壁、大块等方向发展1931新西兰新西兰1933美国美国地震地震1.ConceptsMasonryinclude:
Units(砌块)Mortar(砂浆)Accessories(附件)UnitsincludeGlassblockNaturalstoneClaybrickConcreteblock;StructuralclaytileJointingmaterial:
CementmortarCementlimemortarLimemortarAccessoriesinclude:
AnchorsJointreinforcementTiesMasonrycanbeusedinlBuildingwallslFoundationslFireplaces(壁炉)lRetainingwalls(档土墙)lFloorslSidewalks(人行道)lPatios(院子)lDriveways(车道)lVeneer(饰面)24墙和12墙CharacteristicsofMasonryStructureLikeconcrete,masonryisstrongincompressionbutrequirestheincorporationofreinforcingsteeltoincreaseresistancetotensionandflexuralStrongweakweakloadloadCompressionloadTensionloadloadCompressionTensionFlexuralBrickcolumnConcretecolumnR.C.columnMu10M5NuC20C20425NuNuLoadcarryingcapacity(kN)e=0e=0.7ye=yNuyyy43017217(100%)(40%)(4%)2450432238(570%)(100%)(55%)308015601230(716%)(363%)(287%)MaterialStrength(N/mm2)BrickMu10MortarM5Brickmasonary2.38Concrete13.5Concrete13.5Reinforcement335ImportantconceptsforbrickmasonrylThestrengthofbrickmasonryislowerthanthestrengthsofitscomponents:
brickandmortarlBrickmasonryismainlyusedinthecasesofuniaxialloadingoreccentricloadingwithsmalleccentricitieslTheheight/thicknessratiobecomesanimportantconcept2.StrengthofbrickandmortarlBrickMu7.5,Mu10,Mu15,Mu20,Mu25,Mu30Withcharacteristiccompressivestrength7.5,10,15,20,25,30N/mm2lMortarCementmortarHighstrengthandstrongdurabilityPoormaneuverability(操作性)LimemortarLowstrengthCementlimemortar性质介于两者之间M0.4,M1.0,M2.5,M5,M7.5,M10,M15LimemortarCementlimemortarM0l验算新砌筑未硬结时的砌体强度时采用的砂浆强度为“0”3.Brickbondingpatterns(砌砖法)4.ShortbrickcolumnunderuniaxialloadinglStage15070%Nu末期会出现第一批裂缝lStage28090%Nu已有裂缝不断开展新裂缝不断产生lStage3裂缝显著开展,半砖小柱侧向凸出ThecomplexstressstateinbrickmasonrylFirst:
Theun-evennessofmortarjointUneventhicknessNotfullysaturatedUnevencomponents砖支承于凹凸不平的砂浆层上Brickisinbending,shearandlocalcompressionstateslSecond:
ThetransversedeformationdifferencebetweenbrickandmortarInitialstateb2b1Deformfreelyundercompressionb1b2b0b1bb2b(砂浆的帕松比大于砖的帕松比)砂浆的帕松比大于砖的帕松比)MortarBricklThird:
StressconcentrationnearheadmortarjointsSummarylBrickisinbending,shear,localcompression,transversetensionandconcentratedstressstate.lThestrengthofbricktoresistbendingandtensionisquitelow.(10%20%ofcompressivestrength.)lVerticalcracksmayoccurnearverticaljointswhenthecompressivestressinbrickisfairlysmalllBrickcolumnisfailedbyinstabilityofslendersub-columnsFactorsaffectingthecompressivestrengthofbrickmasonrylStrengthofbrickBrick100%masonry50%lThicknessofbricklKindsofmortar,andbrickingquality(砌筑质量)Cementmortar=85%(cementlimemortar)Thicknessofmortarlining8mm12mmStandard10mm太厚,横向拉力大;太薄,不易均匀平整5.CompressivestrengthofmasonrylStandardspecimen:
3704901000mmStrengthfmMeanvalue:
fmfkCharacteristicstrength:
fkDesignstrength:
ffMeanvalueandCharacteristicstrengthCharacteristicstrengthandDesignstrengthf:
Coefficientofvariation相当于在非正常生产情况下的最小值。
砌块种类与砌块高度有关考虑砂浆强度的修正系数f1Themeancompressivestrengthofunits(Mpa)f2Themeancompressivestrengthofmortar(Mpa)Determinationofmeanvalue砌体强度设计值的调整al有吊车房屋砌体l无筋砌体,A0.3m2,l有筋砌体,AfNu11Nu22Nu3M5=0.0015=M0=0.009=M0.25=0.002考虑砂浆强度的影响反映构件细长的参数:
高厚比H0计算高度h墙厚对T形或形柱,采用折算厚度htlEccentricloading纵向弯曲产生了侧向变形,而侧向变形又成为新的附加偏心距,如此交互作用,加剧了长柱的破坏统一采用影响系数考虑细长柱承载力的降低When轴心受压柱的稳定系数偏心距影响系数When表观偏心距等效的初始偏心距稳定系数的确定仍采用时的表达形式为偏心距和高厚比对受压构件承载力的影响系数,简称影响系数When轴心受压时的稳定系数When此处以轴压时得到的等效附加偏心距作为偏压情况下的附加偏心距(近似处理)e3e=03e039.1.4Localcompressionl9.1.4.1Uniformlocalcompression(a)(b)(c)(d)竖向应力分布“套箍”作用情况(c),(d)不存在应力状态分布水平应力分布?
破坏形态竖向裂缝发展破坏劈裂破坏试验结果局部抗压强度放大系数AlA0bl烧结多孔砖l如果未用混凝土灌实空腔9.1.4.2Non-uniformlocalcompressionundertheendsofsupportedbeamBeamNlN0WallNon-uniformlocalcompressionNon-uniformlocalcompressionNLN0DiscountcoefficientforupperlocalN0内拱卸压压作用N0WhenLoadcarryingcapacitynon-uniformcoefficientforstressdistributionEffectivesupportinglengtha0BeamWallBeama0ah梁高(mm)f砌体抗压强度设计值(Mpa)a梁端实际支撑长度(mm)Note:
h9.1.4.3Non-uniformlocalcompressionunderpre-castedrigidblockRigidblocktb180mmbbctbBeamNlN0tbbbcBeambbcabbbFunctionsofrigidblocklIncreasingoflocalcompressivearealMoreevencompressivestressdistributionunderrigidblockCalculatingmethodlTreatasshortcolumn(withcrossareaofAl=bbab)undereccentricloadNlN0既有局部受压的特点,又有偏心受压的特点(局部受压,但是应力不均匀)楼面梁屋面梁刚性垫块上表面有效支撑长度9.2CalculatingmethodformasonryunderuniaxialtensionlDesignformulaDesigntensionforceDesigntensionstrengthl9.3.1Flexuralresistance9.3CalculatingmethodformasonryunderbendingmomentDesigntensilestrengthformasonryunderbending不仅应进行弯曲承载力验算;还应进行受剪承载力验算l9.3.2ShearresistanceDesignshearforceWidthInnerarmofforceIMomentofinertiaSAreamomentDesignshearstrength9.4CalculatingmethodformasonryunderShearforceGB500032001计算方法砌体抗剪强度设计值修正系数,剪压复合受力影响系数永久荷载标准值永久荷载标准值永久荷载标准值永久荷载标准值产生的平均压应力水平截面投影面积砖砌体0.60,混凝土砌体0.64rG=1.2时砖砌体0
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