土木工程畢業(yè)設(shè)計(jì)外文文獻(xiàn)翻譯

1、外文文獻(xiàn)翻譯ReinforcedConcreteConcreteandreinforcedconcreteareusedasbuildingmaterialsineverycountry.Inmany,includingtheUnitedStatesandCanada,reinforcedconcreteisadominantstructuralmaterialinengineeredconstruction.Theuniversalnatureofreinforcedconcreteconstructionstemsfromthewideavailabilityofreinforcingba

2、rsandtheconstituentsofconcrete,gravel,sand,andcement,therelativelysimpleskillsrequiredinconcreteconstruction,andtheeconomyofreinforcedconcretecomparedtootherformsofconstruction.Concreteandreinforcedconcreteareusedinbridges,buildingsofallsortsundergroundstructures,watertanks,televisiontowers,offshore

3、oilexplorationandproductionstructures,dams,andeveninships.Reinforcedconcretestructuresmaybecast-in-placeconcrete,constructedintheirfinallocation,ortheymaybeprecastconcreteproducedinafactoryanderectedattheconstructionsite.Concretestructuresmaybesevereandfunctionalindesign,ortheshapeandlayoutandbewhim

4、sicalandartistic.Fewotherbuildingmaterialsoffthearchitectandengineersuchversatilityandscope.Concreteisstrongincompressionbutweakintension.Asaresult,cracksdevelopwheneverloads,orrestrainedshrinkageoftemperaturechanges,giverisetotensilestressesinexcessofthetensilestrengthoftheconcrete.Inaplainconcrete

5、beam,themomentsabouttheneutralaxisduetoappliedloadsareresistedbyaninternaltension-compressioncoupleinvolvingtensionintheconcrete.Suchabeamfailsverysuddenlyandcompletelywhenthefirstcrackforms.Inareinforcedconcretebeam,steelbarsareembeddedintheconcreteinsuchawaythatthetensionforcesneededformomentequil

6、ibriumaftertheconcretecrackscanbedevelopedinthebars.Theconstructionofareinforcedconcretememberinvolvesbuildingafromofmoldintheshapeofthememberbeingbuilt.Theformmustbestrongenoughtosupportboththeweightandhydrostaticpressureofthewetconcrete,andanyforcesappliedtoitbyworkers,concretebuggies,wind,andsoon

7、.Thereinforcementisplacedinthisformandheldinplaceduringtheconcretingoperation.Aftertheconcretehashardened,theformsareremoved.Astheformsareremoved,propsofshoresareinstalledtosupporttheweightoftheconcreteuntilithasreachedsufficientstrengthtosupporttheloadsbyitself.Thedesignermustproportionaconcretemem

8、berforadequatestrengthtoresisttheloadsandadequatestiffnesstopreventexcessivedeflections.Inbeammustbeproportionedsothatitcanbeconstructed.Forexample,thereinforcementmustbedetailedsothatitcanbeassembledinthefield,andsincetheconcreteisplacedintheformafterthereinforcementisinplace,theconcretemustbeablet

9、oflowaround,between,andpastthereinforcementtofillallpartsoftheformcompletely.Thechoiceofwhetherastructureshouldbebuiltofconcrete,steel,masonry,ortimberdependsontheavailabilityofmaterialsandonanumberofvaluedecisions.Thechoiceofstructuralsystemismadebythearchitectofengineerearlyinthedesign,basedonthef

10、ollowingconsiderations:Economy.Frequently,theforemostconsiderationistheoverallconstofthestructure.Thisis,ofcourse,afunctionofthecostsofthematerialsandthelabornecessarytoerectthem.Frequently,however,theoverallcostisaffectedasmuchormorebytheoverallconstructiontimesincethecontractorandownermustborrowor

11、otherwiseallocatemoneytocarryouttheconstructionandwillnotreceiveareturnonthisinvestmentuntilthebuildingisreadyforoccupancy.Inatypicallargeapartmentofcommercialproject,thecostofconstructionfinancingwillbeasignificantfractionofthetotalcost.Asaresult,financialsavingsduetorapidconstructionmaymorethanoff

12、setincreasedmaterialcosts.Forthisreason,anymeasuresthedesignercantaketostandardizethedesignandformingwillgenerallypayoffinreducedoverallcosts.Inmanycasesthelong-termeconomyofthestructuremaybemoreimportantthanthefirstcost.Asaresult,maintenanceanddurabilityareimportantconsideration.Suitabilityofmateri

13、alforarchitecturalandstructuralfunction.Areinforcedconcretesystemfrequentlyallowsthedesignertocombinethearchitecturalandstructuralfunctions.Concretehastheadvantagethatitisplacedinaplasticconditionandisgiventhedesiredshapeandtexturebymeansoftheformsandthefinishingtechniques.Thisallowssuchelementsadfl

14、atplatesorothertypesofslabstoserveasload-bearingelementswhileprovidingthefinishedfloorand/orceilingsurfaces.Similarly,reinforcedconcretewallscanprovidearchitecturallyattractivesurfacesinadditiontohavingtheabilitytoresistgravity,wind,orseismicloads.Finally,thechoiceofsizeofshapeisgovernedbythedesigne

15、randnotbytheavailabilityofstandardmanufacturedmembers.Fireresistance.Thestructureinabuildingmustwithstandtheeffectsofafireandremainstandingwhilethebuildingisevacuatedandthefireisextinguished.Aconcretebuildinginherentlyhasa1-to3-hourfireratingwithoutspecialfireproofingorotherdetails.Structuralsteelor

16、timberbuildingsmustbefireproofedtoattainsimilarfireratings.Lowmaintenance.Concretemembersinherentlyrequirelessmaintenancethandostructuralsteelortimbermembers.Thisisparticularlytrueifdense,air-entrainedconcretehasbeenusedforsurfacesexposedtotheatmosphere,andifcarehasbeentakeninthedesigntoprovideadequ

17、atedrainageoffandawayfromthestructure.Specialprecautionsmustbetakenforconcreteexposedtosaltssuchasdeicingchemicals.Availabilityofmaterials.Sand,gravel,cement,andconcretemixingfacilitiesareverywidelyavailable,andreinforcingsteelcanbetransportedtomostjobsitesmoreeasilythancanstructuralsteel.Asaresult,

18、reinforcedconcreteisfrequentlyusedinremoteareas.Ontheotherhand,thereareanumberoffactorsthatmaycauseonetoselectamaterialotherthanreinforcedconcrete.Theseinclude:Lowtensilestrength.Thetensilestrengthconcreteismuchlowerthanitscompressivestrength(about1/10),andhenceconcreteissubjecttocracking.Instructur

19、alusesthisisovercomebyusingreinforcementtocarrytensileforcesandlimitcrackwidthstowithinacceptablevalues.Unlesscareistakenindesignandconstruction,however,thesecracksmaybeunsightlyormayallowpenetrationofwater.Whenthisoccurs,waterorchemicalssuchasroaddeicingsaltsmaycausedeteriorationorstainingoftheconc

20、rete.Specialdesigndetailsarerequiredinsuchcases.Inthecaseofwater-retainingstructures,specialdetailsand/ofprestressingarerequiredtopreventleakage.Formsandshoring.Theconstructionofacast-in-placestructureinvolvesthreestepsnotencounteredintheconstructionofsteelortimberstructures.Theseare(a)theconstructi

21、onoftheforms,(b)theremovaloftheseforms,and(c)proppingorshoringthenewconcretetosupportitsweightuntilitsstrengthisadequate.Eachofthesestepsinvolveslaborand/ormaterials,whicharenotnecessarywithotherformsofconstruction.Relativelylowstrengthperunitofweightforvolume.Thecompressivestrengthofconcreteisrough

22、ly5to10%thatofsteel,whileitsunitdensityisroughly30%thatofsteel.Asaresult,aconcretestructurerequiresalargervolumeandagreaterweightofmaterialthandoesacomparablesteelstructure.Asaresult,long-spanstructuresareoftenbuiltfromsteel.Time-dependentvolumechanges.Bothconcreteandsteelundergo-approximatelythesam

23、eamountofthermalexpansionandcontraction.Becausethereislessmassofsteeltobeheatedorcooled,engineeringandarchitectureconcreteforstructuresandandbecausesteelisabetterconcrete,asteelstructureisgenerallyaffectedbytemperaturechangestoagreaterextentthanisaconcretestructure.Ontheotherhand,concreteundergoesfr

24、yingshrinkage,which,ifrestrained,maycausedeflectionsorcracking.Furthermore,deflectionswilltendtoincreasewithtime,possiblydoubling,duetocreepoftheconcreteundersustainedloads.requiresbasicknowledgeofInalmosteverybranchofcivilextensiveuseismadeofreinforcedfoundations.Engineersandarchitectsreinforcedcon

25、cretedesignthroughouttheirprofessionalcareers.Muchofthistextisdirectlyconcernedwiththebehaviorandproportioningofcomponentsthatmakeuptypicalreinforcedconcretestructures-beams,columns,andslabs.Oncethebehavioroftheseindividualelementsisunderstood,thedesignerwillhavethebackgroundtoanalyzeanddesignawider

26、angeofcomplexstructures,suchasfoundations,buildings,andbridges,composedoftheseelements.Sincereinforcedconcreteisanohomogeneousmaterialthatcreeps,shrinks,andcracks,itsstressescannotbeaccuratelypredictedbythetraditionalequationsderivedinacourseinstrengthofmaterialsforhomogeneouselasticmaterials.Muchof

27、reinforcedconcretedesigninthereforeempirical,i.e.,designequationsanddesignmethodsarebasedonexperimentalandtime-provedresultsinsteadofbeingderivedexclusivelyfromtheoreticalformulations.Athoroughunderstandingofthebehaviorofreinforcedconcretewillallowthedesignertoconvertanotherwisebrittlematerialintoto

28、ughductilestructuralelementsandtherebytakeadvantageofconcretesdesirablecharacteristics,itshighcompressivestrength,itsfireresistance,anditsdurability.Concrete,astonelikematerial,ismadebymixingcement,water,fineaggregate(oftensand),coarseaggregate,andfrequentlyotheradditives(thatmodifyproperties)intoaw

29、orkablemixture.Initsunhardenedorplasticstate,concretecanbeplacedinformstoproducealargevarietyofstructuralelements.Althoughthehardenedconcretebyitself,i.e.,withoutanyreinforcement,isstrongincompression,itlackstensilestrengthandthereforecrackseasily.Becauseunreinforcedconcreteisbrittle,itcannotundergo

30、largedeformationsunderloadandfailssuddenly-withoutwarning.Theadditionfosteelreinforcementtotheconcretereducesthenegativeeffectsofitstwoprincipalinherentweaknesses,itssusceptibilitytocrackinganditsbrittleness.Whenthereinforcementisstronglybondedtotheconcrete,astrong,stiff,andductileconstructionmateri

31、alisproduced.Thismaterial,calledreinforcedconcrete,isusedextensivelytoconstructfoundations,structuralframes,storagetakes,shellroofs,highways,walls,dams,canals,andinnumerableotherstructuresandbuildingproducts.Twoothercharacteristicsofconcretethatarepresentevenwhenconcreteisreinforcedareshrinkageandcr

32、eep,butthenegativeeffectsofthesepropertiescanbemitigatedbycarefuldesign.Acodeisasettechnicalspecificationsandstandardsthatcontrolimportantdetailsofdesignandconstruction.Thepurposeofcodesitproducestructuressothatthepublicwillbeprotectedfrompoorofinadequateandconstruction.Twotypesfcoedsexist.Onetype,c

33、alledastructuralcode,isoriginatedandcontrolledbyspecialistswhoareconcernedwiththeproperuseofaspecificmaterialorwhoareinvolvedwiththesafedesignofaparticularclassofstructures.Thesecondtypeofcode,calledabuildingcode,isestablishedtocoverconstructioninagivenregion,oftenacityorastate.Theobjectiveofabuildi

34、ngcodeisalsotoprotectthepublicbyaccountingfortheinfluenceofthelocalenvironmentalconditionsonconstruction.Forexample,localauthoritiesmayspecifyadditionalprovisionstoaccountforsuchregionalconditionsasearthquake,heavysnow,ortornados.Nationalstructuralcodesgenrallyareincorporatedintolocalbuildingcodes.T

35、heAmericanConcreteInstitute(ACI)BuildingCodecoveringthedesignofreinforcedconcretebuildings.Itcontainsprovisionscoveringallaspectsofreinforcedconcretemanufacture,design,andconstruction.Itincludesspecificationsonqualityofmaterials,detailsonmixingandplacingconcrete,designassumptionsfortheanalysisofcont

36、inuousstructures,andequationsforproportioningmembersfordesignforces.Allstructuresmustbeproportionedsotheywillnotfailordeformexcessivelyunderanypossibleconditionofservice.Thereforeitisimportantthatanengineerusegreatcareinanticipatingalltheprobableloadstowhichastructurewillbesubjectedduringitslifetime

37、.Althoughthedesignofmostmembersiscontrolledtypicallybydeadandliveloadactingsimultaneously,considerationmustalsobegiventotheforcesproducedbywind,impact,shrinkage,temperaturechange,creepandsupportsettlements,earthquake,andsoforth.Theloadassociatedwiththeweightofthestructureitselfanditspermanentcompone

38、ntsiscalledthedeadload.Thedeadloadofconcretemembers,whichissubstantial,shouldneverbeneglectedindesigncomputations.Theexactmagnitudeofthedeadloadisnotknownaccuratelyuntilmembershavebeensized.Sincesomefigureforthedeadloadmustbeusedincomputationstosizethemembers,itsmagnitudemustbeestimatedatfirst.After

39、astructurehasbeenanalyzed,thememberssized,andarchitecturaldetailscompleted,thedeadloadcanbecomputedmoreaccurately.Ifthecomputeddeadloadisapproximatelyequaltotheinitialestimateofitsvalue(orslightlyless),thedesigniscomplete,butifasignificantdifferenceexistsbetweenthecomputedandestimatedvaluesofdeadwei

40、ght,thecomputationsshouldberevisedusinganimprovedvalueofdeadload.Anaccurateestimateofdeadloadisparticularlyimportantwhenspansarelong,sayover75ft(22.9m),becausedeadloadconstitutesamajorportionofthedesignload.Liveloadsassociatedwithbuildingusearespecificitemsofequipmentandoccupantsinacertainareaofabui

41、lding,buildingcodesspecifyvaluesofuniformliveforwhichmembersaretobedesigned.Afterthestructurehasbeensizedforverticalload,itischeckedforwindincombinationwithdeadandliveloadasspecifiedinthecode.Windloadsdonotusuallycontrolthesizeofmembersinbuildinglessthan16to18stories,butfortallbuildingswindloadsbeco

42、mesignificantandcauselargeforcestodevelopinthestructures.Undertheseconditionseconomycanbeachievedonlybyselectingastructuralsystemthatisabletotransferhorizontalloadsintothegroundefficiently.鋼筋混凝土在每一個(gè)國(guó)家，混凝土及鋼筋混凝土都被用來(lái)作為建筑材料。很多地區(qū)，包括美國(guó)和加拿大，鋼筋混凝土在工程建設(shè)中是主要的結(jié)構(gòu)材料。鋼筋混凝土建筑的普遍性源于鋼筋的廣泛供應(yīng)和混凝土的組成成分，礫石，沙子，水泥等，混凝土施工

43、所需的技能相對(duì)簡(jiǎn)單，與其他形式的建設(shè)相比，鋼筋混凝土更加經(jīng)濟(jì)。混凝土及鋼筋混凝土用于橋梁、各種地下結(jié)構(gòu)建筑、水池、電視塔、海洋石油勘探建筑、工業(yè)建筑、大壩，甚至用于造船業(yè)。鋼筋混凝土結(jié)構(gòu)可能是現(xiàn)澆混凝土結(jié)構(gòu)，在其最后位置建造，或者他們可能是在一家工廠生產(chǎn)混凝土預(yù)制件，再在施工現(xiàn)場(chǎng)安裝?；炷两Y(jié)構(gòu)在設(shè)計(jì)上可能是普通的和多功能的，或形狀和布局是奇想和藝術(shù)的。其他很少幾種建材能夠提供建筑和結(jié)構(gòu)如此的通用性和廣泛適用性?；炷劣休^強(qiáng)的抗壓力但抗拉力很弱。因此，混凝土，每當(dāng)承受荷載時(shí)，或約束收縮或溫度變化，引起拉應(yīng)力，在超過(guò)抗拉強(qiáng)度時(shí)，裂縫開(kāi)始發(fā)展。在素混凝土梁中，中和軸的彎矩是由在混凝土內(nèi)部拉壓力偶來(lái)

44、抵抗作用荷載之后的值。這種梁當(dāng)出現(xiàn)第一道裂縫時(shí)就突然完全地?cái)嗔蚜?。在鋼筋混凝土梁中，鋼筋是那樣埋置于混凝土中，以至于?dāng)混凝土開(kāi)裂后彎矩平衡所需的拉力由綱筋中產(chǎn)生。鋼筋混凝土構(gòu)件的建造包括以被建構(gòu)件的形狀支摸板。模型必須足夠強(qiáng)大，以至于能夠支承自重和濕混凝土的靜水壓力，工人施加的任何力量都適用于它，具體的手推車，風(fēng)壓力，等等。在混凝土的運(yùn)作過(guò)程中，鋼筋將被放置在摸板中。在混凝土硬化后，棋板都將被移走。當(dāng)棋板被移走時(shí)，支撐將被安裝來(lái)承受混凝土的重量直到它達(dá)到足夠的強(qiáng)度來(lái)承受自重。設(shè)計(jì)師必須使混凝土構(gòu)件有足夠的強(qiáng)度來(lái)抵抗荷、載和足夠的剛度來(lái)防止過(guò)度的撓度變形。除此之外，梁必須設(shè)計(jì)合理以便它能夠被建造

45、。例如，鋼筋必須按構(gòu)造設(shè)計(jì)，以便能在現(xiàn)場(chǎng)裝配。由于當(dāng)鋼筋放入摸板后才澆筑混凝土，因此混凝土必須能夠流過(guò)鋼筋及摸板并完全充滿摸板的每個(gè)角落。被建成的結(jié)構(gòu)材料的選擇是混凝土，還是鋼材、砌體，或木材，取決于是否有材料和一些價(jià)值決策。結(jié)構(gòu)體系的選擇是由建筑師或工程師早在設(shè)計(jì)的基礎(chǔ)上決定的，考慮到下列因素：經(jīng)濟(jì)。常常首要考慮的是結(jié)構(gòu)的總造價(jià)。當(dāng)然，這是隨著材料的成本和安裝構(gòu)件的必需勞動(dòng)力改變的。然而，總投資常常更受總工期的影響，因?yàn)槌邪毯蜆I(yè)主必須借款或貸款以便完成建設(shè)，在建筑物竣工前他們從此項(xiàng)投資中將得不到任何回報(bào)。在一個(gè)典型的大型公寓或商業(yè)項(xiàng)目中，建筑成本的融資將是總費(fèi)用的一個(gè)重要部分。因此，金融儲(chǔ)

46、蓄，由于快速施工可能多于抵消增加材料成本?；谶@個(gè)原因，設(shè)計(jì)師可以采取任何措施規(guī)范設(shè)計(jì)來(lái)減輕削減的成本。在許多情況下，長(zhǎng)期的經(jīng)濟(jì)結(jié)構(gòu)可能比第一成本更重要。因此，維修和耐久性是重要的考慮因素。用于建筑與結(jié)構(gòu)功能適宜的材料。鋼筋混凝土體系經(jīng)常讓設(shè)計(jì)師將建筑與結(jié)構(gòu)的功能相結(jié)合?；炷帘环胖迷谒苄詶l件下借助于棋板和表面加工來(lái)造出想要的形狀和結(jié)構(gòu)，這是它具有的優(yōu)勢(shì)。在提供成品樓或天花板表面時(shí)，這使得平板或其他形式的板作為受力構(gòu)件。同樣，鋼筋混凝土墻壁能提供有吸引力的建筑表面，還有能力抵御重力、風(fēng)力，或地震荷載。最后，大小和形狀的選擇是由設(shè)計(jì)師而不是由提供構(gòu)件的標(biāo)準(zhǔn)決定的。1. 耐火性。建筑結(jié)構(gòu)必須經(jīng)受得

47、住火災(zāi)的襲擊，并且當(dāng)人員疏散及大火撲滅之時(shí)建筑物仍然保持不倒。鋼筋混凝土建筑特殊的防火材料及其他構(gòu)造措施情況下，自身具有1-3個(gè)小時(shí)的耐火極限。鋼結(jié)構(gòu)或木結(jié)構(gòu)必須采取防火措施才能達(dá)到類似的耐火極限。低維護(hù)?；炷翗?gòu)件本身比結(jié)構(gòu)鋼或木材構(gòu)件需要更少的維修。如果致密，尤其如此，加氣混凝土已經(jīng)被用于暴露于大氣中的表面，如果在設(shè)計(jì)中已經(jīng)采取謹(jǐn)慎措施，以提供足夠的排水和遠(yuǎn)離的結(jié)構(gòu)。必須采取的特別預(yù)防措施是讓混凝土接觸到鹽，如除冰化學(xué)品。5.材料的供應(yīng)。砂、碎石、水泥和混凝土攪拌設(shè)備是被非常廣泛使用的，以及鋼筋比結(jié)構(gòu)鋼更容易運(yùn)到多數(shù)工地。因此，鋼筋混凝土在偏遠(yuǎn)地區(qū)經(jīng)常使用。另一方面，有一些因素可能會(huì)導(dǎo)致選

48、擇鋼筋混凝土以外的材料。這些措施包括：1.低抗拉強(qiáng)度?；炷恋目估瓘?qiáng)度是遠(yuǎn)低于其抗壓強(qiáng)度（約1/10）,因此，混凝土易經(jīng)受裂縫。在結(jié)構(gòu)用途時(shí)，用鋼筋承受拉力，并限制裂縫寬度在允許的范圍內(nèi)來(lái)克服。不過(guò)，在設(shè)計(jì)和施工中如果不采取措施，這些裂縫可能有礙觀瞻，或可允許水的浸入。發(fā)生這種情況時(shí)，水或化學(xué)物質(zhì)如道路除冰鹽可能會(huì)導(dǎo)致混凝土的惡化或污染。這種情況下，需要特別設(shè)計(jì)的措施。在水支擋結(jié)構(gòu)這種情況下，需要特別的措施和/或預(yù)應(yīng)力，以防止泄漏。2.支摸。建造一個(gè)現(xiàn)澆結(jié)構(gòu)包括三個(gè)步驟，在鋼或木結(jié)構(gòu)的施工中是遇不到的。這些都是（a）支摸（b）拆摸（c）安裝支撐，直至其達(dá)到足夠的強(qiáng)度以支承其重量。上述每個(gè)步驟，

49、涉及勞動(dòng)力和/或材料，在其他結(jié)構(gòu)形式中，這是沒(méi)有必要的。.每單位重量或量的相對(duì)低強(qiáng)度。該混凝土抗壓強(qiáng)度大約是鋼材抗壓強(qiáng)度5至10%,，而其單位密度大約是鋼材密度的30%。因此，一個(gè)混凝土結(jié)構(gòu)，與鋼結(jié)構(gòu)相比，需要較大的體積和較大重量的材料。因此，大跨度結(jié)構(gòu)，往往建成鋼結(jié)構(gòu)。3 .時(shí)間依賴的量的變化?；炷僚c鋼進(jìn)行大約同樣數(shù)量的熱膨脹和收縮時(shí)，有比較少量的鋼材加熱或冷卻，因?yàn)殇撆c混凝土相比是一個(gè)較好的導(dǎo)體，鋼結(jié)構(gòu)比混凝土結(jié)構(gòu)在更大程度上更易受溫度變化。另一方面，混凝土經(jīng)歷了十縮，如果被抑制，可能會(huì)導(dǎo)致變形或開(kāi)裂。此外，變形隨著時(shí)間的推移將趨于增加，由于混凝土在持續(xù)的負(fù)荷下的徐變，可能會(huì)增加一倍。幾乎在土木工程和建筑的每一個(gè)分支中，鋼筋混凝土在結(jié)構(gòu)和基礎(chǔ)領(lǐng)域內(nèi)都得到了廣泛的使用。因此，工程師及建筑師在其整個(gè)職業(yè)生涯中需要鋼筋混凝土設(shè)計(jì)的基本知識(shí)。文章的大部分是直