完整版土木工程毕业设计外文文献翻译91914196.docx

完整版土木工程毕业设计外文文献翻译91914196.docx

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完整版土木工程毕业设计外文文献翻译91914196

外文文献翻译

ReinforcedConcrete

Concreteandreinforcedconcreteareusedasbuildingmaterialsineverycountry.Inmany,includingtheUnitedStatesandCanada,reinforcedconcreteisadominantstructuralmaterialinengineeredconstruction.Theuniversalnatureofreinforcedconcreteconstructionstemsfromthewideavailabilityofreinforcingbarsandtheconstituentsofconcrete,gravel,sand,andcement,therelativelysimpleskillsrequiredinconcreteconstruction,andtheeconomyofreinforcedconcretecomparedtootherformsofconstruction.Concreteandreinforcedconcreteareusedinbridges,buildingsofallsortsundergroundstructures,watertanks,televisiontowers,offshoreoilexplorationandproductionstructures,dams,andeveninships.

Reinforcedconcretestructuresmaybecast-in-placeconcrete,constructedintheirfinallocation,ortheymaybeprecastconcreteproducedinafactoryanderectedattheconstructionsite.Concretestructuresmaybesevereandfunctionalindesign,ortheshapeandlayoutandbewhimsicalandartistic.Fewotherbuildingmaterialsoffthearchitectandengineersuchversatilityandscope.

Concreteisstrongincompressionbutweakintension.Asaresult,cracksdevelopwheneverloads,orrestrainedshrinkageoftemperaturechanges,giverisetotensilestressesinexcessofthetensilestrengthoftheconcrete.Inaplainconcretebeam,themomentsabouttheneutralaxisduetoappliedloadsareresistedbyaninternaltension-compressioncoupleinvolvingtensionintheconcrete.Suchabeamfailsverysuddenlyandcompletelywhenthefirstcrackforms.Inareinforcedconcretebeam,steelbarsareembeddedintheconcreteinsuchawaythatthetensionforcesneededformomentequilibriumaftertheconcretecrackscanbedevelopedinthebars.

Theconstructionofareinforcedconcretememberinvolvesbuildingafromofmoldintheshapeofthememberbeingbuilt.Theformmustbestrongenoughtosupportboththeweightand.Thereinforcementisplacedinthisformandplaceduringtheconcretingoperation.Aftertheconcreteaconcretememberforadequatestrengthtoresisttheloadsandadequatestiffnesstopreventexcessivedeflections.Inbeammustbeproportionedsothatitcanbeconstructed.Forexample,thereinforcementmustbedetailedsothatitcanbeassembledinthefield,andsincetheconcreteisplacedintheformafterthereinforcementisinplace,theconcretemustbeabletoflowaround,between,andpastthereinforcementtofillallpartsoftheformcompletely.

Thechoiceofwhetherastructureshouldbebuiltofconcrete,steel,masonry,ortimberdependsontheavailabilityofmaterialsandonanumberofvaluedecisions.Thechoiceofstructuralsystemismadebythearchitectofengineerearlyinthedesign,basedonthefollowingconsiderations:

1.Economy.Frequently,theforemostconsiderationistheoverallconstofthestructure.Thisis,ofcourse,afunctionofthecostsofthematerialsandthelabornecessarytoerectthem.Frequently,timesincethecontractorandownermustborroworotherwiseallocatemoneytocarryouttheconstructionandwillnotreceiveareturnonthisinvestmentuntilthebuildingisreadyforoccupancy.Inatypicallargeapartmentofcommercialproject,thecostofconstructionfinancingwillbeasignificantfractionofthetotalcost.Asaresult,financialsavingsduetorapidconstructionmaymorethanoffsetincreasedmaterialcosts.Forthisreason,anymeasuresthedesignercantaketostandardizethedesignandformingwillgenerallypayoffinreducedoverallcosts.

Inmanycasesthelong-termeconomyofthestructuremaybemoreimportantthanthefirstcost.Asaresult,maintenanceanddurabilityareimportantconsideration.

2.Suitabilityofmaterialforarchitecturalandstructuralfunction.Areinforcedconcretesystemfrequentlyallowsthedesignertocombinethearchitecturalandstructuralfunctions.Concreteaplasticconditionandisgiventhedesiredshapeandtexturebymeansoftheformsandthefinishingtechniques.Thisallowssuchelementsadflatplatesorothertypesofslabstoserveasload-bearingelementswhileprovidingthefinishedfloorandorceilingsurfaces.Similarly,reinforcedconcretewallscanprovidearchitecturallyattractivesurfacesinadditiontoabuildingmustwithstandtheeffectsofafireandremainstandingwhilethebuildingisevacuatedandthefireisextinguished.Aconcretebuildinginherentlysimilarfireratings.

4.Lowmaintenance.Concretemembersinherentlyrequirelessmaintenancethandostructuralsteelortimbermembers.Thisisparticularlytrueifdense,air-entrainedconcreteusedforsurfacesexposedtotheatmosphere,andifcaretakeninthedesigntoprovideadequatedrainageoffandawayfromthestructure.Specialprecautionsmustbetakenforconcreteexposedtosaltssuchasdeicingchemicals.

5.Availabilityofmaterials.Sand,gravel,cement,andconcretemixingfacilitiesareverywidelyavailable,andreinforcingsteelcanbetransportedtomostjobsitesmoreeasilythancanstructuralsteel.Asaresult,reinforcedconcreteisfrequentlyusedinremoteareas.

Ontheotherreinforcedconcrete.Theseinclude:

1.Lowtensilestrength.Thetensilestrengthconcreteismuchlowerthanitscompressivestrength（about110）,andstructuralusesthisisovercomebyusingreinforcementtocarrytensileforcesandlimitcrackwidthstowithinacceptablevalues.Unlesscareistakenindesignandconstruction,ofwater.Whenthisoccurs,waterorchemicalssuchasroaddeicingsaltsmaycausedeteriorationorstainingoftheconcrete.Specialdesigndetailsarerequiredinsuchcases.Inthecaseofwater-retainingstructures,specialdetailsandofprestressingarerequiredtopreventleakage.

2.Formsandshoring.Theconstructionofacast-in-placestructureinvolvesthreestepsnotencounteredintheconstructionofsteelortimberstructures.Theseare（a）theconstructionoftheforms,（b）theremovaloftheseforms,and（c）proppingorshoringthenewconcretetosupportitsweightuntilitsstrengthisadequate.Eachofthesestepsinvolveslaborandormaterials,whicharenotnecessarywithotherformsofconstruction.

3.Relativelylowstrengthperunitofweightforvolume.Thecompressivestrengthofconcreteisroughly5to10%thatofsteel,whileitsunitdensityisroughly30%thatofsteel.Asaresult,aconcretestructurerequiresalargervolumeandagreaterweightofmaterialthandoesacomparablesteelstructure.Asaresult,long-spanstructuresareoftenbuiltfromsteel.

4.Time-dependentvolumechanges.Bothconcreteandsteelundergo-approximatelythesameamountofthermalexpansionandcontraction.Becausethereislessmassofsteeltobeisaconcretestructure.Ontheotheralmosteverybranchofcivilengineeringandarchitectureextensiveuseismadeofreinforcedconcreteforstructuresandfoundations.Engineersandarchitectsrequiresbasicknowledgeofreinforcedconcretedesignthroughouttheirprofessionalcareers.Muchofthistextisdirectlyconcernedwiththebehaviorandproportioningofcomponentsthatmakeuptypicalreinforcedconcretestructures-beams,columns,andslabs.Oncethebehavioroftheseindividualelementsisunderstood,thedesignerwillawiderangeofcomplexstructures,suchasfoundations,buildings,andbridges,composedoftheseelements.

Sincereinforcedconcreteisanoacourseinstrengthofmaterialsforinthereforeempirical,i.e.,designequationsanddesignmethodsarebasedonexperimentalandtime-provedresultsinsteadofbeingderivedexclusivelyfromtheoreticalformulations.

Athoroughunderstandingofthebehaviorofreinforcedconcretewillallowthedesignertoconvertanotherwisebrittlematerialintotoughductilestructuralelementsandtherebytakeadvantageofconcrete’sdesirablecharacteristics,itssand）,coarseaggregate,andfrequentlyotheradditives（thatmodifyproperties）intoaworkablemixture.Initsunhardenedorplasticstate,concretecanbeplacedinformstoproducealargevarietyofstructuralelements.Althoughthecompression,itlackstensilestrengthandthereforecrackseasily.Becauseunreinforcedconcreteisbrittle,itcannotundergolargedeformationsunderloadandfailssuddenly-withoutwarning.Theadditionfosteelreinforcementtotheconcretereducesthenegativeeffectsofitstwoprincipalinherentweaknesses,itssusceptibilitytocrackinganditsbrittleness.Whenthereinforcementisstronglybondedtotheconcrete,astrong,stiff,andductileconstructionmaterialisproduced.Thismaterial,calledreinforcedconcrete,isusedextensivelytoconstructfoundations,structuralframes,storagetakes,shellroofs,whenconcreteisreinforcedareshrinkageandcreep,butthenegativeeffectsofthesepropertiescanbemitigatedbycarefuldesign.

Acodeisasettechnicalspecificationsandstandardsthatcontrolimportantdetailsofdesignandconstruction.Thepurposeofcodesitproducestructuressothatthepublicwillbeprotectedfrompoorofinadequateandconstruction.

Twotypesfcoedsexist.Onetype,calledastructuralcode,isoriginatedandcontrolledbyspecialistswhoareconcernedwiththeproperuseofaspecificmaterialorwhoareinvolvedwiththesafedesignofaparticularclassofstructures.

Thesecondtypeofcode,calledabuildingcode,isestablishedtocoverconstructioninagivenregion,oftenacityorastate.Theobjectiveofabuildingcodeisalsotoprotectthepublicbyaccountingfortheinfluenceofthelocalenvironmentalconditionsonconstruction.Forexample,localauthoritiesmayspecifyadditionalprovisionstoaccountforsuchregionalconditionsasearthquake,ConcreteInstitute（ACI