《土木工程專業(yè)英語 第2版》 課件 Unit1 Introduction to Reinforced Concrete

Unit1IntroductiontoReinforcedConcreteDesignEnglishforCivilEngineering——Teacher:Prof.ZhengLuE-mail:luzheng111@（SchoolofCivilEngineering,TONGJIUNIVERSITY）Unit1IntroductiontoReinforcedConcreteDesign1.1Concrete,ReinforcedConcrete,andPrestressedConcrete（混凝土，鋼筋混凝土，以及預(yù)應(yīng)力混凝土）1.2StructuralForms（結(jié)構(gòu)形式）1.3Loads（荷載）1.4Serviceability,Strength,andStructuralSafety（可用性，強(qiáng)度以及結(jié)構(gòu)安全性）1.4.1VariabilityofLoads（荷載變異性）1.4.2Strength（強(qiáng)度）1.4.3StructuralSafety（結(jié)構(gòu)安全性）1.5DesignBasis（設(shè)計(jì)基礎(chǔ)）1.1Concrete,ReinforcedConcrete,andPrestressedConcreteConcreteisastonelikematerialobtainedbypermittingacarefullyproportionedmixtureofcement,sandandgravelorotheraggregate,andwatertohardeninformsoftheshapeanddimensionsofthedesiredstructure.Thebulkofthematerialconsistsoffineandcoarseaggregate.Cementandwaterinteractchemicallytobindtheaggre-gateparticlesintoasolidmass.Additionalwater,overandabovethatneededforthischemicalreaction,isnecessarytogivethemixturetheworkabilitythatenablesittofilltheformsandsurroundtheembeddedreinforcingsteelpriortohardening.混凝土的組成stonelike像石頭一樣的

cement水泥

gravel砂礫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)permitanevenwidervari-etyofpropertiestobeobtained.特種混凝土property

特性

constituent構(gòu)成的

admixture外加劑plasticizer塑化劑air-entrainingagent加氣劑silicafume硅粉flyash粉煤灰

steam-curing蒸汽養(yǎng)護(hù)1.1Concrete,ReinforcedConcrete,andPrestressedConcreteThesepropertiesdependtoaverysubstantialdegreeontheproportionsofthemix,onthethoroughnesswithwhichthevariousconstituentsareintermixed,andontheconditionsofhumidityandtemperatureinwhichthemixismaintainedfromthemomentitisplacedintheformsuntilitisfullyhardened.Theprocessofcontrollingconditionsafterplacementisknownascuring.Toprotectagainsttheunintentionalproductionofsubstandardconcrete,ahighdegreeofskillfulcontrolandsupervisionisnecessarythroughouttheprocess,fromtheproportioningbyweightoftheindivid-ualcomponents,throughmixingandplacing,untilthecompletionofcuring.混凝土的制作與養(yǎng)護(hù)substantial實(shí)質(zhì)的

thoroughness充分性

intermix混合humidity濕度

curing養(yǎng)護(hù)1.1Concrete,ReinforcedConcrete,andPrestressedConcreteThefactorsthatmakeconcreteauniversalbuildingmaterialaresopronouncedthatithasbeenused,inmoreprimitivekindsandwaysthanatpresent,forthousandsofyears,startingwithlimemortarsfrom12,000to6000BCEinCrete,Cyprus,Greece,andtheMiddleEast.Thefacilitywithwhich,whileplastic,itcanbedepositedandmadetofillformsormoldsofalmostanypracticalshapeisoneofthesefactors.Itshighfireandweatherresistanceisanevidentadvantage.混凝土的歷史與優(yōu)點(diǎn)pronounced顯著的

primitive原始的

limemortars水泥砂漿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).混凝土組成材料的特性additive添加劑

constructionsite施工現(xiàn)場

compressivestrength抗壓強(qiáng)度tensilestrength抗拉強(qiáng)度

1.1Concrete,ReinforcedConcrete,andPrestressedConcreteTooffsetthislimitation,itwasfoundpossible,inthesecondhalfofthenineteenthcentury,tousesteelwithitshightensilestrengthtoreinforceconcrete,chieflyinthoseplaceswhereitslowtensilestrengthwouldlimitthecarryingcapacityofthemember.Thereinforcement,usuallyroundsteelrodswithappropriatesurfacedeformationstoprovideinterlocking,isplacedintheformsinadvanceoftheconcrete.將鋼材引入到混凝土中（即鋼筋混凝土）capacity承載力rod棒，桿interlocking咬合作用1.1Concrete,ReinforcedConcrete,andPrestressedConcreteWhencompletelysurroundedbythehardenedconcretemass,itformsanintegralpartofthemember.Theresultingcombinationoftwomaterials,knownasreinforcedconcrete，combinesmanyoftheadvantagesofeach:therelativelylowcost,goodweatherandfireresistance,goodcompressivestrength,andexcellentformabilityofconcreteandthehightensilestrengthandmuchgreaterductilityandtoughnessofsteel.Itisthiscombinationthatallowsthealmostunlimitedrangeofusesandpossi-bilitiesofreinforcedconcreteintheconstructionofbuildings,bridges,dams,tanks,reservoirs,andahostofotherstructures.鋼筋混凝土優(yōu)點(diǎn)hardened變硬的formability可成形性toughness韌性reservoirs水庫1.1Concrete,ReinforcedConcrete,andPrestressedConcreteAspecialwayhasbeenfound,however,tousesteelsandconcretesofveryhighstrengthincombination.Thistypeofconstructionisknownasprestressedconcrete.Thesteel,intheformofwires,strands,orbars,isembeddedintheconcreteunderhightensionthatisheldinequilibriumbycompressivestressesintheconcreteafterhard-ening.Becauseofthisprecompression,theconcreteinaflexuralmemberwillcrackonthetensionsideatamuchlargerloadthanwhennotsoprecompressed.Prestressinggreatlyreducesboththedeflectionsandthetensilecracksatordinaryloadsinsuchstructures,andtherebyenablesthesehigh-strengthmaterialstobeusedeffectively.預(yù)應(yīng)力混凝土prestressed預(yù)應(yīng)力的wire網(wǎng)strand串bar棒equilibrium平衡precompression預(yù)壓力1.2StructuralFormsFloorsupportsystemsforbuildingsincludethemonolithicslab-and-beamfloorshowninFig.1-1,theone-wayjoistsystemofFig.1-2,andtheflatplatefloor,withoutbeamsorgirders,showninFig.1-3.TheflatslabfloorofFig.1-4,frequentlyusedformoreheavilyloadedbuildingssuchaswarehouses,issimilartotheflatplatefloor,butmakesuseofincreasedslabthicknessinthevicinityofthecolumns,aswellasflaredcolumntops,toreducestressesandincreasestrengthinthesupportregion.Thechoiceamongtheseandothersystemsforfloorsandroofsdependsuponfunc-tionalrequirements,loads,spans,andpermissiblememberdepths,aswellasoncostandestheticfactors.樓層支撐體系monolithic整體的warehouse倉庫vicinity臨近flared向外展開的esthetic審美的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.混凝土殼roof屋頂shell殼cylindrical圓柱形的curvature曲率；彎曲1.2StructuralFormsFig.1-5Foldedplateroofof125ftspan,inadditiontocarryingordinaryroofloads,carriesthesecondflooraswellfromasystemofcablehangers;thegroundflooriskeptfreeofcolumns.Fig.1-6Cylindricalshellroofprovidingcolumn-freeinteriorspace.1.2StructuralFormsCylindricalconcretetanksarewidelyusedforstorageofwaterorinwastepurifi-cationplants.ThedesignshowninFig.1.11isproofthatasanitaryengineeringfacilitycanbeestheticallypleasingaswellasfunctional.Cylindricaltanksareoftenpre-stressedcircumferentiallytomaintaincompressionintheconcreteandeliminatethecrackingthatwouldotherwiseresultfrominternalpressure.圓柱形混凝土水箱storage儲存purifi-cation凈化sanitary衛(wèi)生的esthetically審美地circumferentially圓周地internal內(nèi)部的1.2StructuralFormsFig.1-11CircularconcretetanksusedasapartofthewastewaterpurificationfacilityatHowden,England.(NorthumbrianWaterAuthoritywithLuderandJones,Architects.)1.3LoadsDeadloadsarethosethatareconstantinmagnitudeandfixedinlocationthroughoutthelifetimeofthestructure.Usuallythemajorpartofthedeadloadistheweightofthestructureitself.Thiscanbecalculatedwithgoodaccuracyfromthedesigncon-figuration,dimensionsofthestructure,anddensityofthematerial.Forbuildings,floorfill,finishfloors,andplasteredceilingsareusuallyincludedasdeadloads,andanallowanceismadeforsuspendedloadssuchaspipingandlightingfixtures.Forbridges,deadloadsmayincludewearingsurfaces,sidewalks,andcurbs,andanallowanceismadeforpipingandothersuspendedloads.恒載deadloads恒載magnitude幅值plasteredceiling灰泥吊頂piping管道系統(tǒng)suspendedload懸掛荷載sidewalk人行道curb路邊1.3LoadsLiveloadsconsistchieflyofoccupancyloadsinbuildingsandtrafficloadsonbridges.Theymaybeeitherfullyorpartiallyinplaceornotpresentatall,andmayalsochangeinlocation.Theirmagnitudeanddistributionatanygiventimeareuncer-tain,andeventheirmaximumintensitiesthroughoutthelifetimeofthestructurearenotknownwithprecision.Theminimumliveloadsforwhichthefloorsandroofofabuildingshouldbedesignedareusuallyspecifiedinthebuildingcodethatgovernsatthesiteofconstruction.活載occupancy使用distribution分布1.3LoadsEnvironmentalloadsconsistmainlyofsnowloads,windpressureandsuction,earthquakeloads(i.e.,inertiaforcescausedbyearthquakemotions),soilpressuresonsubsurfaceportionsofstructures,loadsfrompossiblepondingofrainwateronflatsur-faces,andforcescausedbytemperaturedifferentials.Likeliveloads,environmentalloadsatanygiventimeareuncertaininbothmagnitudeanddistribution.Thebook,MinimumDesignLoadsforBuildingsandOtherStructures,containsmuchinformationonenvironmentalloads,whichisoftenmodifiedlocallydepending,forinstance,onlocalclimaticorseismicconditions.環(huán)境荷載suction吸力subsurface表面下的ponding積水differential差別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.結(jié)構(gòu)的可用性，強(qiáng)度以及結(jié)構(gòu)安全性collapse倒塌serviceability可用性foreseeably可預(yù)知地1.4.1VariabilityofLoadsSincethemaximumloadthatwilloccurduringthelifeofastructureisuncertain,itcanbeconsideredarandomvariable.Inspiteofthisuncertainty,theengineermustprovideanadequatestructure.Aprobabilitymodelforthemaximumloadcanbedevisedbymeansofaprobabilitydensityfunctionforloads,asrepresentedbythefre-quencycurveofFig.1.14a.Theexactformofthisdistributioncurve,foranyparticulartypeofloadingsuchasofficeloads，canbedeterminedonlyonthebasisofstatisticaldataobtainedfromlarge-scaleloadsurveys.Anumberofsuchsurveyshavebeencom-pleted.Fortypesofloadsforwhichsuchdataarescarce,f