《土木工程专业英语 第2版》 课件 Unit1 Introduction to Reinforced Concrete

Unit1IntroductiontoReinforcedConcreteDesignEnglishforCivilEngineering——Teacher:Prof.ZhengLuE-mail:luzheng111@（SchoolofCivilEngineering,TONGJIUNIVERSITY）Unit1IntroductiontoReinforcedConcreteDesign1.1Concrete,ReinforcedConcrete,andPrestressedConcrete（混凝土，钢筋混凝土，以及预应力混凝土）1.2StructuralForms（结构形式）1.3Loads（荷载）1.4Serviceability,Strength,andStructuralSafety（可用性，强度以及结构安全性）1.4.1VariabilityofLoads（荷载变异性）1.4.2Strength（强度）1.4.3StructuralSafety（结构安全性）1.5DesignBasis（设计基础）1.1Concrete,ReinforcedConcrete,andPrestressedConcreteConcreteisastonelikematerialobtainedbypermittingacarefullyproportionedmixtureofcement,sandandgravelorotheraggregate,andwatertohardeninformsoftheshapeanddimensionsofthedesiredstructure.Thebulkofthematerialconsistsoffineandcoarseaggregate.Cementandwaterinteractchemicallytobindtheaggre­gateparticlesintoasolidmass.Additionalwater,overandabovethatneededforthischemicalreaction,isnecessarytogivethemixturetheworkabilitythatenablesittofilltheformsandsurroundtheembeddedreinforcingsteelpriortohardening.混凝土的组成stonelike像石头一样的

cement水泥

gravel砂砾aggregate骨料

coarse粗糙的workability和易性1.1Concrete,ReinforcedConcrete,andPrestressedConcreteConcreteswithawiderangeofpropertiescanbeobtainedbyappropriateadjustmentoftheproportionsoftheconstituentmaterials.Specialcements(suchashighearlystrengthcements),specialaggregates(suchasvariouslightweightorheavyweightaggregates),admixtures(suchasplasticizers,air-entrainingagents,silicafume,andflyash),andspecialcuringmethods(suchassteam-curing)permitanevenwidervari­etyofpropertiestobeobtained.特种混凝土property

特性

constituent构成的

admixture外加剂plasticizer塑化剂air-entrainingagent加气剂silicafume硅粉flyash粉煤灰

steam-curing蒸汽养护1.1Concrete,ReinforcedConcrete,andPrestressedConcreteThesepropertiesdependtoaverysubstantialdegreeontheproportionsofthemix,onthethoroughnesswithwhichthevariousconstituentsareintermixed,andontheconditionsofhumidityandtemperatureinwhichthemixismaintainedfromthemomentitisplacedintheformsuntilitisfullyhardened.Theprocessofcontrollingconditionsafterplacementisknownascuring.Toprotectagainsttheunintentionalproductionofsubstandardconcrete,ahighdegreeofskillfulcontrolandsupervisionisnecessarythroughouttheprocess,fromtheproportioningbyweightoftheindivid­ualcomponents,throughmixingandplacing,untilthecompletionofcuring.混凝土的制作与养护substantial实质的

thoroughness充分性

intermix混合humidity湿度

curing养护1.1Concrete,ReinforcedConcrete,andPrestressedConcreteThefactorsthatmakeconcreteauniversalbuildingmaterialaresopronouncedthatithasbeenused,inmoreprimitivekindsandwaysthanatpresent,forthousandsofyears,startingwithlimemortarsfrom12,000to6000BCEinCrete,Cyprus,Greece,andtheMiddleEast.Thefacilitywithwhich,whileplastic,itcanbedepositedandmadetofillformsormoldsofalmostanypracticalshapeisoneofthesefactors.Itshighfireandweatherresistanceisanevidentadvantage.混凝土的历史与优点pronounced显著的

primitive原始的

limemortars水泥砂浆facility容易

plastic塑性的deposited放置mold模具1.1Concrete,ReinforcedConcrete,andPrestressedConcreteMostoftheconstituentmaterials,withtheexceptionofcementandadditives,areusuallyavailableatlowcostlocallyoratsmalldistancesfromtheconstructionsite.Itscompressivestrength,likethatofnaturalstones,ishigh,whichmakesitsuitableformembersprimarilysubjecttocompression,suchascolumnsandarches.Ontheotherhand,againasinnaturalstones,itisarelativelybrittlematerialwhosetensilestrengthissmallcomparedwithitscompressivestrength.Thispreventsitseconomicaluseinstructuralmembersthataresubjecttotensioneitherentirely(suchasintie-rods)oroverpartoftheircrosssections(suchasinbeamsorotherflexuralmembers).混凝土组成材料的特性additive添加剂

constructionsite施工现场

compressivestrength抗压强度tensilestrength抗拉强度

1.1Concrete,ReinforcedConcrete,andPrestressedConcreteTooffsetthislimitation,itwasfoundpossible,inthesecondhalfofthenineteenthcentury,tousesteelwithitshightensilestrengthtoreinforceconcrete,chieflyinthoseplaceswhereitslowtensilestrengthwouldlimitthecarryingcapacityofthemember.Thereinforcement,usuallyroundsteelrodswithappropriatesurfacedeformationstoprovideinterlocking,isplacedintheformsinadvanceoftheconcrete.将钢材引入到混凝土中（即钢筋混凝土）capacity承载力rod棒，杆interlocking咬合作用1.1Concrete,ReinforcedConcrete,andPrestressedConcreteWhencompletelysurroundedbythehardenedconcretemass,itformsanintegralpartofthemember.Theresultingcombinationoftwomaterials,knownasreinforcedconcrete，combinesmanyoftheadvantagesofeach:therelativelylowcost,goodweatherandfireresistance,goodcompressivestrength,andexcellentformabilityofconcreteandthehightensilestrengthandmuchgreaterductilityandtoughnessofsteel.Itisthiscombinationthatallowsthealmostunlimitedrangeofusesandpossi­bilitiesofreinforcedconcreteintheconstructionofbuildings,bridges,dams,tanks,reservoirs,andahostofotherstructures.钢筋混凝土优点hardened变硬的formability可成形性toughness韧性reservoirs水库1.1Concrete,ReinforcedConcrete,andPrestressedConcreteAspecialwayhasbeenfound,however,tousesteelsandconcretesofveryhighstrengthincombination.Thistypeofconstructionisknownasprestressedconcrete.Thesteel,intheformofwires,strands,orbars,isembeddedintheconcreteunderhightensionthatisheldinequilibriumbycompressivestressesintheconcreteafterhard­ening.Becauseofthisprecompression,theconcreteinaflexuralmemberwillcrackonthetensionsideatamuchlargerloadthanwhennotsoprecompressed.Prestressinggreatlyreducesboththedeflectionsandthetensilecracksatordinaryloadsinsuchstructures,andtherebyenablesthesehigh-strengthmaterialstobeusedeffectively.预应力混凝土prestressed预应力的wire网strand串bar棒equilibrium平衡precompression预压力1.2StructuralFormsFloorsupportsystemsforbuildingsincludethemonolithicslab-and-beamfloorshowninFig.1-1,theone-wayjoistsystemofFig.1-2,andtheflatplatefloor,withoutbeamsorgirders,showninFig.1-3.TheflatslabfloorofFig.1-4,frequentlyusedformoreheavilyloadedbuildingssuchaswarehouses,issimilartotheflatplatefloor,butmakesuseofincreasedslabthicknessinthevicinityofthecolumns,aswellasflaredcolumntops,toreducestressesandincreasestrengthinthesupportregion.Thechoiceamongtheseandothersystemsforfloorsandroofsdependsuponfunc­tionalrequirements,loads,spans,andpermissiblememberdepths,aswellasoncostandestheticfactors.楼层支撑体系monolithic整体的warehouse仓库vicinity临近flared向外展开的esthetic审美的1.2StructuralFormsFig.1-3Flatplatefloorslab,carrieddirectlybycolumnswithoutbeamsorgirders.(PortlandCementAssociation.)Fig.1-1One-wayreinforcedconcretefloorslabwithmonolithicsupportingbeams.(PortlandCementAssociation.)Fig.1-2One-wayjoistfloorsystem,withcloselyspacedribssupportedbymonolithicconcretebeams;transverseribsprovideforlateraldistributionoflocalizedloads.(PortlandCementAssociation.)Fig.1-4Flatslabfloor,withoutbeamsbutwithslabthicknessincreasedatthecolumnsandwithflaredcolumntopstoprovideforlocalstressconcentrationofforces.1.2StructuralFormsWherelongclearspansarerequiredforroofs,concreteshellspermituseofextremelythinsurfaces,oftenthinner,relatively,thananeggshell.ThefoldedplateroofofFig.1-5issimpletoformbecauseitiscomposedofflatsurfaces;suchroofshavebeenemployedforspansof200ftandmore.ThecylindricalshellofFig.1-6isalsorelativelyeasytoformbecauseithasonlyasinglecurvature;itissimilartothefoldedplateinitsstructuralbehaviorandrangeofspansandloads.ShellsofthistypewereoncequitepopularintheUnitedStateandremainpopularinotherpartsoftheworld.混凝土壳roof屋顶shell壳cylindrical圆柱形的curvature曲率；弯曲1.2StructuralFormsFig.1-5Foldedplateroofof125ftspan,inadditiontocarryingordinaryroofloads,carriesthesecondflooraswellfromasystemofcablehangers;thegroundflooriskeptfreeofcolumns.Fig.1-6Cylindricalshellroofprovidingcolumn-freeinteriorspace.1.2StructuralFormsCylindricalconcretetanksarewidelyusedforstorageofwaterorinwastepurifi­cationplants.ThedesignshowninFig.1.11isproofthatasanitaryengineeringfacilitycanbeestheticallypleasingaswellasfunctional.Cylindricaltanksareoftenpre-stressedcircumferentiallytomaintaincompressionintheconcreteandeliminatethecrackingthatwouldotherwiseresultfrominternalpressure.圆柱形混凝土水箱storage储存purifi­cation净化sanitary卫生的esthetically审美地circumferentially圆周地internal内部的1.2StructuralFormsFig.1-11CircularconcretetanksusedasapartofthewastewaterpurificationfacilityatHowden,England.(NorthumbrianWaterAuthoritywithLuderandJones,Architects.)1.3LoadsDeadloadsarethosethatareconstantinmagnitudeandfixedinlocationthroughoutthelifetimeofthestructure.Usuallythemajorpartofthedeadloadistheweightofthestructureitself.Thiscanbecalculatedwithgoodaccuracyfromthedesigncon­figuration,dimensionsofthestructure,anddensityofthematerial.Forbuildings,floorfill,finishfloors,andplasteredceilingsareusuallyincludedasdeadloads,andanallowanceismadeforsuspendedloadssuchaspipingandlightingfixtures.Forbridges,deadloadsmayincludewearingsurfaces,sidewalks,andcurbs,andanallowanceismadeforpipingandothersuspendedloads.恒载deadloads恒载magnitude幅值plasteredceiling灰泥吊顶piping管道系统suspendedload悬挂荷载sidewalk人行道curb路边1.3LoadsLiveloadsconsistchieflyofoccupancyloadsinbuildingsandtrafficloadsonbridges.Theymaybeeitherfullyorpartiallyinplaceornotpresentatall,andmayalsochangeinlocation.Theirmagnitudeanddistributionatanygiventimeareuncer­tain,andeventheirmaximumintensitiesthroughoutthelifetimeofthestructurearenotknownwithprecision.Theminimumliveloadsforwhichthefloorsandroofofabuildingshouldbedesignedareusuallyspecifiedinthebuildingcodethatgovernsatthesiteofconstruction.活载occupancy使用distribution分布1.3LoadsEnvironmentalloadsconsistmainlyofsnowloads,windpressureandsuction,earthquakeloads(i.e.,inertiaforcescausedbyearthquakemotions),soilpressuresonsubsurfaceportionsofstructures,loadsfrompossiblepondingofrainwateronflatsur­faces,andforcescausedbytemperaturedifferentials.Likeliveloads,environmentalloadsatanygiventimeareuncertaininbothmagnitudeanddistribution.Thebook,MinimumDesignLoadsforBuildingsandOtherStructures,containsmuchinformationonenvironmentalloads,whichisoftenmodifiedlocallydepending,forinstance,onlocalclimaticorseismicconditions.环境荷载suction吸力subsurface表面下的ponding积水differential差别1.4Serviceability,Strength,andStructuralSafetyToserveitspurpose,astructuremustbesafeagainstcollapseandserviceableinuse.Serviceabilityrequiresthatdeflectionsbeadequatelysmall;thatcracks,ifany,bekepttotolerablelimits;thatvibrationsbeminimized;etc.Safetyrequiresthatthestrengthofthestructurebeadequateforallloadsthatmayforeseeablyactonit.Ifthestrengthofastructure,builtasdesigned,couldbepredictedaccurately,andiftheloadsandtheirinternaleffects(moments,shears,axialforces)wereknownaccurately,safetycouldbeensuredbyprovidingacarryingcapacityjustbarelyinexcessoftheknownloads.However,thereareanumberofsourcesofuncertaintyintheanalysis,design,andconstructionofreinforcedconcretestructures.结构的可用性，强度以及结构安全性collapse倒塌serviceability可用性foreseeably可预知地1.4.1VariabilityofLoadsSincethemaximumloadthatwilloccurduringthelifeofastructureisuncertain,itcanbeconsideredarandomvariable.Inspiteofthisuncertainty,theengineermustprovideanadequatestructure.Aprobabilitymodelforthemaximumloadcanbedevisedbymeansofaprobabilitydensityfunctionforloads,asrepresentedbythefre­quencycurveofFig.1.14a.Theexactformofthisdistributioncurve,foranyparticulartypeofloadingsuchasofficeloads，canbedeterminedonlyonthebasisofstatisticaldataobtainedfromlarge-scaleloadsurveys.Anumberofsuchsurveyshavebeencom­pleted.Fortypesofloadsforwhichsuchdataarescarce,f