土木工程毕业设计外文文献翻译.docx

土木工程毕业设计外文文献翻译.docx

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土木工程毕业设计外文文献翻译

外文文献翻译

ReinforcedConcrete

（来自《土木工程英语》）

Concreteandreinforcedconcreteareusedasbuildingmaterialsineverycountry.Inmany,includingtheUnitedStatesandCanada,reinforcedconcreteisadominantstructuralmaterialinengineered

construction.Theuniversalnatureofreinforcedconcreteconstructionstemsfromthewideavailabilityofreinforcingbarsandtheconstituents

ofconcrete,gravel,sand,andcement,therelativelysimpleskillsrequired

inconcreteconstruction,andtheeconomyofreinforcedconcrete

compared

tootherformsofconstruction.Concreteandreinforced

concrete

areusedinbridges,buildingsofallsortsunderground

structures,

watertanks,televisiontowers,offshoreoilexplorationand

productionstructures,dams,andeveninships.

Reinforcedconcretestructuresmaybecast-in-placeconcrete,

constructedintheirfinallocation,ortheymaybeprecastconcrete

produced

inafactoryanderectedattheconstructionsite.Concrete

structures

maybesevereandfunctionalindesign,ortheshapeand

layoutandbewhimsicalandartistic.Fewotherbuildingmaterialsoffthearchitectandengineersuchversatilityandscope.

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

TheconstructionofareinforcedconcretememberinvoIvesbuilding

afromofmoldintheshapeofthememberbeingbuilt.Theformmustbe

strongenoughtosupportboththeweightandhydrostaticpressureof

thewetconcrete,andanyforcesappliedtoitbyworkers,concretebuggies,wind,andsoon.Thereinforcementisplacedinthisformandheldinplaceduringtheconcretingoperation.Aftertheconcretehas

hardened,theformsareremoved.Astheformsareremoved,propsofshoresareinstalledtosupporttheweightoftheconcreteuntilithasreachedsufficientstrengthtosupporttheloadsbyitself.

Thedesignermustproportionaconcretememberforadequate

strengthtoresisttheloadsandadequatestiffnesstopreventexcessivedeflections.Inbeammustbeproportionedsothatitcanbeconstructed.

Forexample,thereinforcementmustbedetailedsothatitcanbeassembledinthefield,andsincetheconcreteisplacedintheformafterthereinforcementisinplace,theconcretemustbeabletoflowaround,between,andpastthereinforcementtofillallpartsoftheform

completely.

Thechoiceofwhetherastructureshouldbebuiltofconcrete,steel,

masonry,ortimberdependsontheavailabilityofmaterialsandonanumberofvaluedecisions.Thechoiceofstructuralsystemismadeby

thearchitectofengineerearlyinthedesign,basedonthefollowingconsiderations:

1.Economy.Frequently,theforemostconsiderationistheoverallconstofthestructure.Thisis,ofcourse,afunctionofthecostsofthematerialsandthelabornecessarytoerectthem.Frequently,however,the

overallcostisaffectedasmuchormorebytheoverallconstructiontimesincethecontractorandownermustborroworotherwiseallocate

moneytocarryouttheconstructionandwillnotreceiveareturnonthisinvestmentuntilthebuildingisreadyforoccupancy.Inatypicallargeapartmentofcommercialproject,thecostofconstructionfinancingwillbeasignificantfractionofthetotalcost.Asaresult,financialsavingsduetorapidconstructionmaymorethanoffsetincreasedmaterialcosts.Forthisreason,anymeasuresthedesignercantaketostandardizethedesignandformingwillgenerallypayoffinreducedoverallcosts.

InmanycasestheIong-termeconomyofthestructuremaybemoreimportantthanthefirstcost.Asaresult,maintenanceanddurabilityareimportantconsideration.

2.Suitabilityofmaterialforarchitecturalandstructuralfunction.

Areinforcedconcretesystemfrequentlyallowsthedesignertocombinethearchitecturalandstructuralfunctions.Concretehastheadvantagethatitisplacedinaplasticconditionandisgiventhedesiredshapeandtexturebymeansoftheformsandthefinishingtechniques.Thisallowssuchelementsadflatplatesorothertypesofslabstoserveasload-bearingelementswhileprovidingthefinishedfloorand/orceilingsurfaces.Similarly,reinforcedconcretewallscanprovidearchitecturallyattractivesurfacesinadditiontohavingtheabilitytoresistgravity,wind,orseismicloads.Finally,thechoiceofsizeofshapeisgovernedbythedesignerandnotbytheavailabilityofstandardmanufacturedmembers.

3.Fireresistanee.Thestructureinabuildingmustwithstandtheeffectsofafireandremainstandingwhilethebuildingisevacuatedandthefireisextinguished.Aconcretebuildinginherentlyhasa1-to3-hourfireratingwithoutspecialfireproofingorotherdetails.Structuralsteelortimberbuildingsmustbefireproofedtoattainsimilarfireratings.

4.Lowmaintenance.Concretemembersinherentlyrequirelessmaintenancethandostructuralsteelortimbermembers.Thisisparticularlytrueifdense,air-entrainedconcretehasbeenusedforsurfacesexposedtotheatmosphere,andifcarehasbeentakeninthe

designtoprovideadequatedrainageoffandawayfromthestructure.Specialprecautionsmustbetakenforconcreteexposedtosaltssuchasdeicingchemicals.

5.Availabilityofmaterials.Sand,gravel,cement,andconcretemixingfacilitiesareverywidelyavailable,andreinforcingsteelcanbetransportedtomostjobsitesmoreeasilythancanstructuralsteel.Asa

result,reinforcedconcreteisfrequentlyusedinremoteareas.

Ontheotherhand,thereareanumberoffactorsthatmaycauseone

toselectamaterialotherthanreinforcedconcrete.Theseinclude:

1.Lowtensilestrength.Thetensilestrengthconcreteismuchlowerthanitscompressivestrength（about1/10）,andhenceconcreteissubjecttocracking.Instructuralusesthisisovercomebyusing

reinforcementtocarrytensileforcesandlimitcrackwidthstowithin

acceptablevalues.Uniesscareistakenindesignandconstruction,however,thesecracksmaybeunsightlyormayallowpenetrationof

water.Whenthisoccurs,waterorchemicalssuchasroaddeicingsaltsmaycausedeteriorationorstainingoftheconcrete.Specialdesign

detailsarerequiredinsuchcases.Inthecaseofwater-retainingstructures,specialdetailsand/ofprestressingarerequiredtoprevent

leakage.

2.Formsandshoring.Theconstructionofacast-in-placestructure

invoIvesthreestepsnotencounteredintheconstructionofsteelortimberstructures.Theseare（a）theconstructionoftheforms,（b）theremovaloftheseforms,and（c）proppingorshoringthenewconcretetosupportitsweightuntilitsstrengthisadequate.EachofthesestepsinvoIveslaborand/ormaterials,whicharenotnecessarywithotherformsofconstruction.

3.Relativelylowstrengthperunitofweightforvolume.Thecompressivestrengthofconcreteisroughly5to10%thatofsteel,while

itsunitdensityisroughly30%thatofsteel.Asaresult,aconcretestructurerequiresalargervolumeandagreaterweightofmaterialthandoesacomparablesteelstructure.Asaresult,long-spanstructuresareoftenbuiltfromsteel.

4.Time-dependentvolumechanges.Bothconcreteandsteel

time,possiblydoubling,dueto

engineeringandarchitectureconcreteforstructuresandrequiresbasicknowledgeof

undergo-approximatelythesameamountofthermalexpansionandcontraction.Becausethereislessmassofsteeltobeheatedorcooled,andbecausesteelisabetterconcrete,asteelstructureisgenerallyaffectedbytemperaturechangestoagreaterextentthanisaconcretestructure.Ontheotherhand,concreteundergoesfryingshrinkage,which,ifrestrained,maycausedeflectionsorcracking.Furthermore,deflectionswilltendtoincreasewithcreepoftheconcreteundersustainedloads.

Inalmosteverybranchofcivilextensiveuseismadeofreinforcedfoundations.Engineersandarchitectsreinforcedconcretedesignthroughouttheirprofessionalcareers.Much

ofthistextisdirectlyconcernedwiththebehaviorandproportioningofcomponentsthatmakeuptypicalreinforcedconcretestructures-beams,columns,andslabs.Oncethebehavioroftheseindividualelementsis

understood,thedesignerwillhavethebackgroundtoanalyzeand

designawiderangeofcomplexstructures,suchasfoundations,

buildings,andbridges,composedoftheseelements.

Sincereinforcedconcreteisanohomogeneousmaterialthatcreeps,

shrinks,andcracks,itsstressescannotbeaccuratelypredictedbythetraditionalequationsderivedinacourseinstrengthofmaterialsfor

homogeneouselasticmaterials.Muchofreinforcedconcretedesignin

thereforeempirical,i.e.,designequationsanddesignmethodsarebasedonexperimentalandtime-provedresultsinsteadofbeingderived

exclusivelyfromtheoreticalformulations.

Athoroughunderstandingofthebehaviorofreinforcedconcrete

willallowthedesignertoconvertanotherwisebrittlematerialintotoughductilestructuralelem