土木工程畢業(yè)設(shè)計外文文獻翻譯

1、外文文獻翻譯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國家，混凝土及鋼筋混凝土都被用來作為建筑材料。很多地區(qū)，包括美國和加拿大，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、所需的技能相對簡單，與其他形式的建設(shè)相比，鋼筋混凝土更加經(jīng)濟。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)場安裝?；炷两Y(jié)構(gòu)在設(shè)計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^強的抗壓力但抗拉力很弱。因此，混凝土，每當承受荷載時，或約束收縮或溫度變化，引起拉應(yīng)力，在超過抗拉強度時，裂縫開始發(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

44、抵抗作用荷載之后的值。這種梁當出現(xiàn)第一道裂縫時就突然完全地斷裂了。在鋼筋混凝土梁中，鋼筋是那樣埋置于混凝土中，以至于當混凝土開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。在混凝土的運作過程中，鋼筋將被放置在摸板中。在混凝土硬化后，棋板都將被移走。當棋板被移走時，支撐將被安裝來承受混凝土的重量直到它達到足夠的強度來承受自重。設(shè)計師必須使混凝土構(gòu)件有足夠的強度來抵抗荷、載和足夠的剛度來防止過度的撓度變形。除此之外，梁必須設(shè)計合理以便它能夠被建造

45、。例如，鋼筋必須按構(gòu)造設(shè)計，以便能在現(xiàn)場裝配。由于當鋼筋放入摸板后才澆筑混凝土，因此混凝土必須能夠流過鋼筋及摸板并完全充滿摸板的每個角落。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)計的基礎(chǔ)上決定的，考慮到下列因素：經(jīng)濟。常常首要考慮的是結(jié)構(gòu)的總造價。當然，這是隨著材料的成本和安裝構(gòu)件的必需勞動力改變的。然而，總投資常常更受總工期的影響，因為承包商和業(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投資中將得不到任何回報。在一個典型的大型公寓或商業(yè)項目中，建筑成本的融資將是總費用的一個重要部分。因此，金融儲

46、蓄，由于快速施工可能多于抵消增加材料成本?；谶@個原因，設(shè)計師可以采取任何措施規(guī)范設(shè)計來減輕削減的成本。在許多情況下，長期的經(jīng)濟結(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造出想要的形狀和結(jié)構(gòu)，這是它具有的優(yōu)勢。在提供成品樓或天花板表面時，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)計師而不是由提供構(gòu)件的標準決定的。1. 耐火性。建筑結(jié)構(gòu)必須經(jīng)受得

47、住火災(zāi)的襲擊，并且當人員疏散及大火撲滅之時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個小時的耐火極限。鋼結(jié)構(gòu)或木結(jié)構(gòu)必須采取防火措施才能達到類似的耐火極限。低維護。混凝土構(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)計中已經(jīng)采取謹慎措施，以提供足夠的排水和遠離的結(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)鋼更容易運到多數(shù)工地。因此，鋼筋混凝土在偏遠地區(qū)經(jīng)常使用。另一方面，有一些因素可能會導(dǎo)致選

48、擇鋼筋混凝土以外的材料。這些措施包括：1.低抗拉強度?；炷恋目估瓘姸仁沁h低于其抗壓強度（約1/10）,因此，混凝土易經(jīng)受裂縫。在結(jié)構(gòu)用途時，用鋼筋承受拉力，并限制裂縫寬度在允許的范圍內(nèi)來克服。不過，在設(shè)計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，水或化學(xué)物質(zhì)如道路除冰鹽可能會導(dǎo)致混凝土的惡化或污染。這種情況下，需要特別設(shè)計的措施。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。建造一個現(xiàn)澆結(jié)構(gòu)包括三個步驟，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，直至其達到足夠的強度以支承其重量。上述每個步驟，

49、涉及勞動力和/或材料，在其他結(jié)構(gòu)形式中，這是沒有必要的。.每單位重量或量的相對低強度。該混凝土抗壓強度大約是鋼材抗壓強度5至10%,，而其單位密度大約是鋼材密度的30%。因此，一個混凝土結(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 .時間依賴的量的變化?；炷僚c鋼進行大約同樣數(shù)量的熱膨脹和收縮時，有比較少量的鋼材加熱或冷卻，因為鋼與混凝土相比是一個較好的導(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，可能會導(dǎo)致變形或開裂。此外，變形隨著時間的推移將趨于增加，由于混凝土在持續(xù)的負荷下的徐變，可能會增加一倍。幾乎在土木工程和建筑的每一個分支中，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職業(yè)生涯中需要鋼筋混凝土設(shè)計的基本知識。文章的大部分是直