土木工程外文翻译-钢筋混凝土

土木工程外文翻译—钢筋混凝土PAGEPAGE6外文文献翻译ReinforcedConcreteConcreteandreinforcedconcreteareusedasbuildingmaterialsineverycountry.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.土木工程外文翻译—钢筋混凝土全文共1页，当前为第1页。Theconstructionofareinforcedconcretememberinvolvesbuildingafromofmoldintheshapeofthememberbeingbuilt.Theformmustbestrongenoughtosupportboththeweightandhydrostaticpressureofthewetconc土木工程外文翻译—钢筋混凝土全文共1页，当前为第1页。Thedesignermustproportionaconcretememberforadequatestrengthtoresisttheloadsandadequatestiffnesstopreventexcessivedeflections.Inbeammustbeproportionedsothatitcanbeconstructed.Forexample,thereinforcementmustbedetailedsothatitcanbeassembledinthefield,andsincetheconcreteisplacedintheformafterthereinforcementisinplace,theconcretemustbeabletoflowaround,between,andpastthereinforcementtofillallpartsoftheformcompletely.Thechoiceofwhetherastructureshouldbebuiltofconcrete,steel,masonry,ortimberdependsontheavailabilityofmaterialsandonanumberofvaluedecisions.Thechoiceofstructuralsystemismadebythearchitectofengineerearlyinthedesign,basedonthefollowingconsiderations:1.Economy.Frequently,theforemostconsiderationistheoverallconstofthestructure.Thisis,ofcourse,afunctionofthecostsofthematerialsandthelabornecessarytoerectthem.Frequently,however,theoverallcostisaffectedasmuchormorebytheoverallconstructiontimesincethecontractorandownermustborroworotherwiseallocatemoneytocarryouttheconstructionandwillnotreceiveareturnonthisinvestmentuntilthebuildingisreadyforoccupancy.Inatypicallargeapartmentofcommercialproject,thecostofconstructionfinancingwillbeasignificantfractionofthetotalcost.Asaresult,financialsavingsduetorapidconstructionmaymorethanoffsetincreasedmaterialcosts.Forthisreason,anymeasuresthedesignercantaketostandardizethedesignandformingwillgenerallypayoffinreducedoverallcosts.Inmanycasesthelong-termeconomyofthestructuremaybemoreimportantthanthefirstcost.Asaresult,maintenanceanddurabilityareimportantconsideration.土木工程外文翻译—钢筋混凝土全文共2页，当前为第2页。2.Suitabilityofmaterialforarchitecturalandstructuralfunction.Areinforcedconcretesystemfrequentlyallowsthedesignertocombinethearchitecturalandstructuralfunctions.Concretehastheadvantagethatitisplacedinaplasticconditionandisgiventhedesiredshapeandtexturebymeansoftheformsandthefinishingtechniq土木工程外文翻译—钢筋混凝土全文共2页，当前为第2页。3.Fireresistance.Thestructureinabuildingmustwithstandtheeffectsofafireandremainstandingwhilethebuildingisevacuatedandthefireisextinguished.Aconcretebuildinginherentlyhasa1-to3-hourfireratingwithoutspecialfireproofingorotherdetails.Structuralsteelortimberbuildingsmustbefireproofedtoattainsimilarfireratings.4.Lowmaintenance.Concretemembersinherentlyrequirelessmaintenancethandostructuralsteelortimbermembers.Thisisparticularlytrueifdense,air-entrainedconcretehasbeenusedforsurfacesexposedtotheatmosphere,andifcarehasbeentakeninthedesigntoprovideadequatedrainageoffandawayfromthestructure.Specialprecautionsmustbetakenforconcreteexposedtosaltssuchasdeicingchemicals.5.Availabilityofmaterials.Sand,gravel,cement,andconcretemixingfacilitiesareverywidelyavailable,andreinforcingsteelcanbetransportedtomostjobsitesmoreeasilythancanstructuralsteel.Asaresult,reinforcedconcreteisfrequentlyusedinremoteareas.Ontheotherhand,thereareanumberoffactorsthatmaycauseonetoselectamaterialotherthanreinforcedconcrete.Theseinclude:1.Lowtensilestrength.Thetensilestrengthconcreteismuchlowerthanitscompressivestrength(about1/10),andhenceconcreteissubjecttocracking.Instructuralusesthisisovercomebyusingreinforcementtocarrytensileforcesandlimitcrackwidthstowithinacceptablevalues.Unlesscareistakenindesignandconstruction,however,thesecracksmaybeunsightlyormayallowpenetrationofwater.Whenthisoccurs,waterorchemicalssuchasroaddeicingsaltsmaycausedeteriorationorstainingoftheconcrete.Specialdesigndetailsarerequiredinsuchcases.Inthecaseofwater-retainingstructures,specialdetailsand/ofprestressingarerequiredtopreventleakage.2.Formsandshoring.Theconstructionofacast-in-placestructureinvolvesthreestepsnotencounteredintheconstructionofsteelortimberstructures.Theseare(a)theconstructionoftheforms,(b)theremovaloftheseforms,and(c)proppingorshoringthenewconcretetosupportitsweightuntilitsstrengthisadequate.Eachofthesestepsinvolveslaborand/ormaterials,whicharenotnecessarywithotherformsofconstruction.土木工程外文翻译—钢筋混凝土全文共3页，当前为第3页。3.Relativelylowstrengthperunitofweightforvolume.土木工程外文翻译—钢筋混凝土全文共3页，当前为第3页。4.Time-dependentvolumechanges.Bothconcreteandsteelundergo-approximatelythesameamountofthermalexpansionandcontraction.Becausethereislessmassofsteeltobeheatedorcooled,andbecausesteelisabetterconcrete,asteelstructureisgenerallyaffectedbytemperaturechangestoagreaterextentthanisaconcretestructure.Ontheotherhand,concreteundergoesfryingshrinkage,which,ifrestrained,maycausedeflectionsorcracking.Furthermore,deflectionswilltendtoincreasewithtime,possiblydoubling,duetocreepoftheconcreteundersustainedloads.Inalmosteverybranchofcivilengineeringandarchitectureextensiveuseismadeofreinforcedconcreteforstructuresandfoundations.Engineersandarchitectsrequiresbasicknowledgeofreinforcedconcretedesignthroughouttheirprofessionalcareers.Muchofthistextisdirectlyconcernedwiththebehaviorandproportioningofcomponentsthatmakeuptypicalreinforcedconcretestructures-beams,columns,andslabs.Oncethebehavioroftheseindividualelementsisunderstood,thedesignerwillhavethebackgroundtoanalyzeanddesignawiderangeofcomplexstructures,suchasfoundations,buildings,andbridges,composedoftheseelements.Sincereinforcedconcreteisanohomogeneousmaterialthatcreeps,shrinks,andcracks,itsstressescannotbeaccuratelypredictedbythetraditionalequationsderivedinacourseinstrengthofmaterialsforhomogeneouselasticmaterials.Muchofreinforcedconcretedesigninthereforeempirical,i.e.,designequationsanddesignmethodsarebasedonexperimentalandtime-provedresultsinsteadofbeingderivedexclusivelyfromtheoreticalformulations.Athoroughunderstandingofthebehaviorofreinforcedconcretewillallowthedesignertoconvertanotherwisebrittlematerialintotoughductilestructuralelementsandtherebytakeadvantageofconcrete’sdesirablecharacteristics,itshighcompressivestrength,itsfireresistance,anditsdurability.土木工程外文翻译—钢筋混凝土全文共4页，当前为第4页。Concrete,astonelikematerial,ismadebymixingcement,water,fineaggregate(oftensand),coarseaggregate,andfrequentlyotheradditives(thatmodifyproperties)intoaworkablemixture.Initsunhardenedorplasticstate,concretecanbeplacedinformstoproducealargevarietyofstructuralelements.Althoughthehardenedconcretebyitself,i.e.,withoutanyreinforcement,isstrongincompression,itlackstensilestrengthandthereforecrackseasily.Becauseunreinforcedconcreteisbrittle,itcannotundergolargedeformationsunderloadandfailssuddenly-withoutwarning.Theadditionfosteelreinforcementtotheconcretereducesthenegativeeffectsofitstwoprincipalinherentweaknesses,itssusceptibilitytocrackinganditsbrittleness.Whenthereinforcementisstronglybondedtotheconcrete,astrong,stiff,andductileconstructionmaterialisproduced.Thismaterial,calledreinforcedconcrete,isuse土木工程外文翻译—钢筋混凝土全文共4页，当前为第4页。Acodeisasettechnicalspecificationsandstandardsthatcontrolimportantdetailsofdesignandconstruction.Thepurposeofcodesitproducestructuressothatthepublicwillbeprotectedfrompoorofinadequateandconstruction.Twotypesfcoedsexist.Onetype,calledastructuralcode,isoriginatedandcontrolledbyspecialistswhoareconcernedwiththeproperuseofaspecificmaterialorwhoareinvolvedwiththesafedesignofaparticularclassofstructures.Thesecondtypeofcode,calledabuildingcode,isestablishedtocoverconstructioninagivenregion,oftenacityorastate.Theobjectiveofabuildingcodeisalsotoprotectthepublicbyaccountingfortheinfluenceofthelocalenvironmentalconditionsonconstruction.Forexample,localauthoritiesmayspecifyadditionalprovisionstoaccountforsuchregionalconditionsasearthquake,heavysnow,ortornados.Nationalstructuralcodesgenrallyareincorporatedintolocalbuildingcodes.TheAmericanConcreteInstitute(ACI)BuildingCodecoveringthedesignofreinforcedconcretebuildings.Itcontainsprovisionscoveringallaspectsofreinforcedconcretemanufacture,design,andconstruction.Itincludesspecificationsonqualityofmaterials,detailsonmixingandplacingconcrete,designassumptionsfortheanalysisofcontinuousstructures,andequationsforproportioningmembersfordesignforces.土木工程外文翻译—钢筋混凝土全文共5页，当前为第5页。Allstructure土木工程外文翻译—钢筋混凝土全文共5页，当前为第5页。Althoughthedesignofmostmembersiscontrolledtypicallybydeadandliveloadactingsimultaneously,considerationmustalsobegiventotheforcesproducedbywind,impact,shrinkage,temperaturechange,creepandsupportsettlements,earthquake,andsoforth.Theloadassociatedwiththeweightofthestructureitselfanditspermanentcomponentsiscalledthedeadload.Thedeadloadofconcretemembers,whichissubstantial,shouldneverbeneglectedindesigncomputations.Theexactmagnitudeofthedeadloadisnotknownaccuratelyuntilmembershavebeensized.Sincesomefigureforthedeadloadmustbeusedincomputationstosizethemembers,itsmagnitudemustbeestimatedatfirst.Afterastructurehasbeenanalyzed,thememberssized,andarchitecturaldetailscompleted,thedeadloadcanbecomputedmoreaccurately.Ifthecomputeddeadloadisapproximatelyequaltotheinitialestimateofitsvalue(orslightlyless),thedesigniscomplete,butifasignificantdifferenceexistsbetweenthecomputedandestimatedvaluesofdeadweight,thecomputationsshouldberevisedusinganimprovedvalueofdeadload.Anaccurateestimateofdeadloadisparticularlyimportantwhenspansarelong,sayover75ft(22.9m),becausedeadloadconstitutesamajorportionofthedesignload.Liveloadsassociatedwithbuildingusearespecificitemsofequipmentandoccupantsinacertainareaofabuilding,buildingcodesspecifyvaluesofuniformliveforwhichmembersaretobedesigned.土木工程外文翻译—钢筋混凝土全文共6页，当前为第6页。Afterthestructurehasbeensizedforverticalload,itischeckedforwindincombinationwithdeadandliveloadasspecifiedinthecode.Windloadsdonotusuallycontrolthesizeofmembersinbuildinglessthan16to18stories,butfortallb土木工程外文翻译—钢筋混凝土全文共6页，当前为第6页。PAGE2钢筋混凝土在每一个国家，混凝土及钢筋混凝土都被用来作为建筑材料。很多地区，包括美国和加拿大，钢筋混凝土在工程建设中是主要的结构材料。钢筋混凝土建筑的普遍性源于钢筋的广泛供应和混凝土的组成成分，砾石，沙子，水泥等，混凝土施工所需的技能相对简单，与其他形式的建设相比，钢筋混凝土更加经济。混凝土及钢筋混凝土用于桥梁、各种地下结构建筑、水池、电视塔、海洋石油勘探建筑、工业建筑、大坝，甚至用于造船业。钢筋混凝土结构可能是现浇混凝土结构，在其最后位置建造，或者他们可能是在一家工厂生产混凝土预制件，再在施工现场安装。混凝土结构在设计上可能是普通的和多功能的，或形状和布局是奇想和艺术的。其他很少几种建材能够提供建筑和结构如此的通用性和广泛适用性。混凝土有较强的抗压力但抗拉力很弱。因此，混凝土，每当承受荷载时，或约束收缩或温度变化，引起拉应力，在超过抗拉强度时，裂缝开始发展。在素混凝土梁中，中和轴的弯矩是由在混凝土内部拉压力偶来抵抗作用荷载之后的值。这种梁当出现第一道裂缝时就突然完全地断裂了。在钢筋混凝土梁中，钢筋是那样埋置于混凝土中，以至于当混凝土开裂后弯矩平衡所需的拉力由纲筋中产生。钢筋混凝土构件的建造包括以被建构件的形状支摸板。模型必须足够强大，以至于能够支承自重和湿混凝土的静水压力，工人施加的任何力量都适用于它，具体的手推车，风压力，等等。在混凝土的运作过程中，钢筋将被放置在摸板中。在混凝土硬化后，模板都将被移走。当模板被移走时，支撑将被安装来承受混凝土的重量直到它达到足够的强度来承受自重。设计师必须使混凝土构件有足够的强度来抵抗荷、载和足够的刚度来防止过度的挠度变形。除此之外，梁必须设计合理以便它能够被建造。例如，钢筋必须按构造设计，以便能在现场装配。由于当钢筋放入摸板后才浇筑混凝土，因此混凝土必须能够流过钢筋及摸板并完全充满摸板的每个角落。被建成的结构材料的选择是混凝土，还是钢材、砌体，或木材，取决于是否有材料和一些价值决策。结构体系的选择是由建筑师或工程师早在设计的基础上决定的，考虑到下列因素：土木工程外文翻译—钢筋混凝土全文共7页，当前为第7页。1.经济。常常首要考虑的是结构的总造价。当然，这是随着材料的成本和安装构件的必需劳动力改变的。然而，总投资常常更受总工期的影响，因为承包商和业主必须借款或贷款以便完成建设，在建筑物竣工前他们从此项投资中将得不到任何回报。在一个典型的大型公寓或商业项目中，建筑成本的融资将是总费用的一个重要部分。因此，金融储蓄，由于快速施工可能多于抵消增加材料成本。基于这个原因，设计师可以采取任何措施规范设计土木工程外文翻译—钢筋混凝土全文共7页，当前为第7页。在许多情况下，长期的经济结构可能比第一成本更重要。因此，维修和耐久性是重要的考虑因素。2.用于建筑与结构功能适宜的材料。钢筋混凝土体系经常让设计师将建筑与结构的功能相结合。混凝土被放置在塑性条件下借助于模板和表面加工来造出想要的形状和结构，这是它具有的优势。在提供成品楼或天花板表面时，这使得平板或其他形式的板作为受力构件。同样，钢筋混凝土墙壁能提供有吸引力的建筑表面，还有能力抵御重力、风力，或地震荷载。最后，大小和形状的选择是由设计师而不是由提供构件的标准决定的。3.耐火性。建筑结构必须经受得住火灾的袭击，并且当人员疏散及大火扑灭之时建筑物仍然保持不倒。钢筋混凝土建筑特殊的防火材料及其他构造措施情况下，自身具有1-3个小时的耐火极限。钢结构或木结构必须采取防火措施才能达到类似的耐火极限。4.低维护。混凝土构件本身比结构钢或木材构件需要更少的维修。如果致密，尤其如此，加气混凝土已经被用于暴露于大气中的表面，如果在设计中已经采取谨慎措施，以提供足够的排水和远离的结构。必须采取的特别预防措施是让混凝土接触到盐，如除冰化学品。5.材料的供应。砂、碎石、水泥和混凝土搅拌设备是被非常广泛使用的，以及钢筋比结构钢更容易运到多数工地。因此，钢筋混凝土在偏远地区经常使用。另一方面，有一些因素可能会导致选择钢筋混凝土以外的材料。这些措施包括：1.低抗拉强度。混凝土的抗拉强度是远低于其抗压强度（约1/10），因此，混凝土易经受裂缝。在结构用途时，用钢筋承受拉力，并限制裂缝宽度在允许的范围内来克服。不过，在设计和施工中如果不采取措施，这些裂缝可能会有碍观瞻，或可允许水的浸入。发生这种情况时，水或化学物质如道路除冰盐可能会导致混凝土的恶化或污染。这种情况下，需要特别设计的措施。在水支挡结构这种情况下，需要特别的措施和/或预应力，以防止泄漏。2.支摸。建造一个现浇结构包括三个步骤，在钢或木结构的施工中是遇不到的。这些都是（a）支摸（b）拆摸（c）安装支撑，直至其达到足够的强度以支承其重量。上述每个步骤，涉及劳动力和/或材料，在其他结构形式中，这是没有必要的。3.每单位重量或量的相对低强度。该混凝土抗压强度大约是钢材抗压强度5至10％，，而其单位密度大约是钢材密度的30％。因此，一个混凝土结构，与钢结构相比，需要较大的体积和较大重量的材料。因此，大跨度结构，往往建成钢结构。土木工程外文翻译—钢筋混凝土全文共8页，当前为第8页。4.时间依赖的量的变化。混凝土与钢进行大约同样数量的热膨胀和收缩时，有比较少量的钢材加热或冷却，因为钢与混凝土相比是一个较好的导体，钢结构比混凝土结构在更大程度上更易受温度变化。另一方面，混凝土经历了干缩，如果被抑制，可能会导致变形或开裂。此外，变形随着时间的推移将趋于增加，由于混凝土在持续的负荷土木工程外文翻译—钢筋混凝土全文共8页，当前为第8页。几乎在土木工程和建筑的每一个分支中，钢筋混凝土在结构和基础领域内都得到了广泛的使用。因此，工程师及建筑师在其整个职业生涯中需要钢筋混凝土设计的基本知识。文章的大部分是直接关于组成典型的钢筋混凝土结构的部件如梁、柱和板