土木工程畢業(yè)設(shè)計外文文獻(xiàn)翻譯

1、外文文獻(xiàn)翻譯Reinforced ConcreteConcreteandreinforcedconcreteareusedasbuildingmaterialsineverycountry.Inmany,includingtheUnitedStatesandCanada,reinforcedconcreteisadominantstructuralmaterialinengineeredconstruction.Theuniversalnatureofreinforcedconcreteconstruction stems from the wide availability of reinf

2、orcing bars andtheconstituentsofconcrete,gravel,sand,andcement,therelativelysimpleskillsrequiredinconcreteconstruction,andtheeconomyofreinforcedconcretecomparedtootherformsofconstruction.Concreteandreinforcedconcreteareusedinbridges,buildingsofallsortsundergroundstructures,watertanks,television towe

3、rs, offshore oil exploration and production structures,dams, and even in ships.Reinforcedconcretestructuresmaybe cast-in-placeconcrete,constructed in their final location, or they may be precast concreteproduced in a factory and erected at the construction site. Concretestructures may be severe and

4、functional in design, or the shape andlayout andbe whimsicalandartistic.Few otherbuildingmaterialsoff the architect and engineer such versatility and scope.Concreteisstrongincompressionbut weakintension.As aresult,cracksdevelopwheneverloads,orrestrainedshrinkageoftemperature changes, give rise to te

5、nsile stresses in excess of thetensilestrengthoftheconcrete.Inaplainconcretebeam,themoments about the neutral axis due to applied loads are resisted byaninternaltension-compressioncoupleinvolvingtensionintheconcrete.Suchabeam failsverysuddenlyand completelywhenthefirstcrackforms.Inareinforcedconcret

6、ebeam, steelbarsareembedded in the concrete in such a way that the tension forces neededfor moment equilibrium after the concrete cracks can be developed inthe bars.Theconstructionofareinforcedconcretememberinvolvesbuilding a from of mold in the shape of the member being built. The form must be stro

7、ng enough to support both the weight and hydrostatic0/11pressure of the wet concrete, and any forces applied to it by workers,concretebuggies,wind,andsoon.Thereinforcementisplacedinthisformand heldin placeduringtheconcretingoperation. Aftertheconcretehas hardened,the formsareremoved.Astheformsarerem

8、oved, props of shores are installed to support the weight of theconcreteuntilithasreachedsufficientstrengthtosupporttheloads by itself.Thedesignermustproportionaconcretemember foradequatestrengthtoresisttheloadsandadequatestiffnesstopreventexcessive deflections. In beam must be proportioned so that

9、it can beconstructed. For example, the reinforcement must be detailed so thatit can be assembled in the field, and since the concrete is placed intheformafterthereinforcementisinplace,theconcretemustbeable to flow around, between, and past the reinforcement to fill allparts of the form completely.Th

10、echoiceofwhetherastructureshouldbe builtofconcrete,steel,masonry,ortimberdepends on theavailabilityofmaterialsand on a number of value decisions. The choice of structural systemismade bythearchitectofengineerearlyinthedesign,basedonthe following considerations:1. Economy. Frequently, the foremost co

11、nsideration is the overall const of the structure. This is, of course, a function of the costsof the materials and the labor necessary to erect them. Frequently, however, the overall cost is affected as much or more by the overallconstructiontime sincethecontractorand ownermust borroworotherwise all

12、ocate money to carry out the construction and will notreceive a return on this investment until the building is ready foroccupancy.In atypicallargeapartmentofcommercial project,thecost of construction financing will be a significant fraction of thetotal cost. As a result, financial savings due to ra

13、pid constructionmay more than offset increased material costs. For this reason, anymeasures the designer can take to standardize the design and formingwill generally pay off in reduced overall costs.In many cases the long-term economy of the structure may be moreimportantthanthe firstcost.Asaresult,

14、maintenanceanddurability are important consideration.1/112.Suitabilityofmaterialforarchitecturalandstructuralfunction.A reinforced concrete system frequently allows the designertocombinethearchitecturaland structuralfunctions.Concretehasthe advantage that it is placed in a plastic condition and is g

15、iventhe desired shape and texture by means of the forms and the finishingtechniques. This allows such elements ad flat plates or other typesofslabs to serveasload-bearingelementswhileprovidingthefinishedfloorand/orceilingsurfaces.Similarly,reinforcedconcretewallscanprovidearchitecturallyattractivesu

16、rfacesinadditiontohavingtheabilitytoresistgravity,wind,orseismicloads.Finally,thechoiceofsizeofshapeisgovernedbythedesigner and not by the availability of standard manufactured members.3.Fireresistance.Thestructureinabuildingmustwithstandtheeffectsofafireandremainstandingwhilethe buildingisevacuated

17、andthefireisextinguished.Aconcretebuildinginherentlyhasa1-to3-hourfireratingwithoutspecialfireproofingorotherdetails.Structuralsteelor timberbuildingsmust be fireproofed to attain similar fire ratings.4.Lowmaintenance.Concretemembersinherentlyrequirelessmaintenancethandostructuralsteelortimbermember

18、s.Thisisparticularly true if dense, air-entrained concrete has been used forsurfaces exposed to the atmosphere, and if care has been taken in thedesign to provide adequate drainage off and away from the structure.Special precautions must be taken for concrete exposed to salts suchas deicing chemical

19、s.5. Availability of materials.Sand, gravel, cement, and concretemixingfacilitiesareverywidelyavailable,andreinforcingsteelcan be transported to most job sites more easily than can structuralsteel. As a result, reinforced concrete is frequently used in remoteareas.On the other hand, there are a numb

20、er of factors that may causeonetoselectamaterialotherthan reinforcedconcrete.Theseinclude:1.Low tensilestrength.The tensilestrengthconcreteismuchlower thanitscompressivestrength(about1/10),and henceconcrete is subject to cracking. In structural uses this is overcome2/11by using reinforcement to carr

21、y tensile forces and limit crack widthsto within acceptable values. Unlesscareistakenin designandconstruction,however,thesecracksmay beunsightlyormayallowpenetrationofwater.When thisoccurs,waterorchemicals suchasroaddeicingsaltsmaycausedeteriorationorstainingoftheconcrete. Special design details are

22、 required in such cases. In thecase of water-retainingstructures,specialdetailsand/ofprestressing are required to prevent leakage.2.Formsandshoring.Theconstructionofacast-in-placestructure involves three steps not encountered in the construction ofsteel or timber structures. These are ( a ) the cons

23、truction of theforms, ( b ) the removal of these forms, and (c) propping or shoringthe new concrete to support its weight until its strength is adequate.Each of these steps involves labor and / or materials, which are notnecessary with other forms of construction.3.Relativelylowstrengthperunitofweig

24、htforvolume.Thecompressive strength of concrete is roughly 5 to 10% that of steel,while its unit density is roughly 30% that of steel. As a result, aconcrete structure requires a larger volume and a greater weight ofmaterial than does a comparable steel structure. As a result, long-span structures a

25、re often built from steel.4.Time-dependentvolumechanges. Bothconcreteandsteelundergo-approximatelythesame amount ofthermalexpansionandcontraction.Becausethereislessmassofsteeltobe heatedorcooled,andbecausesteelisabetterconcrete,asteelstructureisgenerallyaffectedbytemperaturechangestoagreater extentt

26、hanisaconcretestructure.Ontheotherhand,concreteundergoesfryingshrinkage,which,ifrestrained,may causedeflectionsorcracking.Furthermore,deflectionswilltendtoincreasewithtime,possiblydoubling, due to creep of the concrete under sustained loads.Inalmosteverybranchofcivilengineeringandarchitectureextensi

27、veuseismadeofreinforcedconcreteforstructuresandfoundations.Engineersandarchitectsrequiresbasicknowledgeofreinforcedconcretedesignthroughouttheirprofessionalcareers.Muchofthistextisdirectlyconcernedwiththebehaviorandproportioning of components that make up typical reinforced concrete 3/11structures-b

28、eams,columns,andslabs.Once thebehavioroftheseindividualelementsisunderstood,thedesignerwillhavethebackground to analyze and design a wide range of complex structures,such asfoundations,buildings,andbridges,composedoftheseelements.Sincereinforcedconcreteisanohomogeneousmaterialthatcreeps,shrinks,andc

29、racks,itsstressescannotbeaccuratelypredictedbythetraditionalequationsderivedinacourseinstrengthofmaterialsforhomogeneouselasticmaterials.Much ofreinforcedconcretedesigninthereforeempirical,i.e.,designequationsanddesignmethodsarebasedonexperimentalandtime-proved results instead of being derived exclu

30、sively from theoreticalformulations.Athoroughunderstandingofthebehaviorofreinforcedconcretewill allow the designer to convert an otherwise brittle material intotoughductilestructuralelementsandtherebytakeadvantageofconcrete s desirable characteristics,its high compressive strength,its fire resistanc

31、e, and its durability.Concrete, a stone like material, is made by mixing cement, water,fine aggregate ( often sand ), coarse aggregate, and frequently otheradditives ( that modify properties ) into a workable mixture. In itsunhardenedorplasticstate,concretecanbeplacedinformstoproduce a large variety

32、 of structural elements. Although the hardenedconcretebyitself,i.e.,withoutanyreinforcement,isstrongincompression,itlackstensilestrengthandthereforecracks easily.Because unreinforcedconcreteisbrittle,itcannotundergolargedeformationsunderload andfailssuddenly-withoutwarning.Theaddition fo steel reinf

33、orcement to the concrete reduces the negativeeffects of its two principal inherent weaknesses, its susceptibilityto crackinganditsbrittleness.When thereinforcementisstronglybondedto theconcrete,astrong,stiff,andductileconstructionmaterialisproduced.Thismaterial,calledreinforcedconcrete,isused extens

34、ively to construct foundations, structural frames, storagetakes,shellroofs,highways,walls,dams,canals,andinnumerableother structures and building products. Two other characteristics ofconcretethatarepresentevenwhenconcreteisreinforcedare4/11shrinkage and creep, but the negative effects of these prop

35、erties can be mitigated by careful design.A code is a set technical specifications and standards that control important details of design and construction. The purpose ofcodes it produce structures so that the public will be protected from poor of inadequate and construction.Two types f coeds exist.

36、 One type, called a structural code, isoriginatedand controlledbyspecialistswho areconcernedwiththeproper use of a specific material or who are involved with the safedesign of a particular class of structures.The second type of code, called a building code, is establishedto cover construction in a g

37、iven region, often a city or a state. Theobjectiveofabuildingcodeisalsotoprotectthepublicbyaccounting for the influence of the local environmental conditions onconstruction.Forexample,localauthoritiesmay specifyadditionalprovisionstoaccountforsuchregionalconditionsasearthquake,heavy snow,ortornados.

38、Nationalstructuralcodesgenrallyareincorporated into local building codes.TheAmericanConcreteInstitute( ACI)BuildingCode coveringthedesignofreinforcedconcretebuildings.Itcontainsprovisionscovering all aspects of reinforced concrete manufacture, design, andconstruction.Itincludesspecificationsonqualit

39、yofmaterials,detailsonmixingandplacing concrete,design assumptionsfortheanalysisof continuousstructures,andequationsforproportioningmembers for design forces.Allstructuresmustbeproportionedsotheywillnotfailordeform excessively under any possible condition of service. Thereforeit is important that an

40、 engineer use great care in anticipating allthe probable loads to which a structure will be subjected during itslifetime.Although the design of mostmembers iscontrolledtypicallybydead and live load acting simultaneously, consideration must also begiven to the forces produced by wind, impact, shrinka

41、ge, temperaturechange, creep and support settlements, earthquake, and so forth.The load associated with the weight of the structure itself anditspermanentcomponentsiscalledthedeadload. The deadloadof5/11concrete members, which is substantial, should never be neglected indesigncomputations.Theexactma

42、gnitudeofthedeadloadisnotknown accurately until members have been sized. Since some figure forthe dead load must be used in computations to size the members, itsmagnitudemustbeestimatedatfirst.Afterastructurehas beenanalyzed, the members sized, and architectural details completed, thedead load can b

43、e computed more accurately. If the computed dead loadis approximatelyequaltotheinitialestimateofitsvalue( orslightlyless),thedesigniscomplete,butifasignificantdifferenceexistsbetweenthecomputedandestimatedvaluesofdeadweight, the computations should be revised using an improved value ofdeadload.Anacc

44、urateestimateofdeadloadisparticularlyimportantwhen spansarelong,sayover75ft(22.9m ),becausedead load constitutes a major portion of the design load.Liveloadsassociatedwithbuildingusearespecificitemsofequipmentandoccupantsin acertainareaofabuilding,buildingcodesspecifyvaluesofuniformliveforwhichmembe

45、rs aretobedesigned.Afterthestructurehasbeensizedforverticalload,itischecked for wind in combination with dead and live load as specifiedin the code. Wind loads do not usually control the size of members inbuildinglessthan16 to18stories,butfortallbuildingswindloadsbecome significantandcauselargeforce

46、stodevelopinthestructures.Undertheseconditionseconomy canbeachievedonlybyselectingastructuralsystemthatisabletotransferhorizontalloads into the ground efficiently.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