建筑英语论文--建筑材料的应用--英汉对照.doc

建筑英语论文--建筑材料的应用--英汉对照.doc

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Theapplicationofconstructionalmaterial

建筑材料的应用

　　Theavailabilityofsuitablestructuralmaterialsisoneoftheprincipallimitationsontheaccomplishmentofanexperiencedstructuralengineer.Earlybuildersdependedalmostexclusivelyonwood,stone,brick,andconcrete.AlthoughironhadbeenusedbyhumansatleastsincethebuildingoftheEgyptianpyramids,useofitasastructuralmaterialwaslimitedbecauseofthedifficultiesofsmeltingitinlargequantities.Withtheindustrialrevolution,however,cameboththeneedforironasastructuralmaterialandthecapabilityofsmeltingitinquantity.

　　JohnSmeaton,anEnglishcivilengineer,wasthefirsttousecastironextensivelyasastructuralmaterialinthemid-eighteenthcentury.After1841,malleableironwasdevelopedasamorereliablematerialandwaswidelyused.Whereasmalleableironwassuperiortocastiron,therewerestilltoomanystructuralfailuresandtherewasaneedforamorereliablematerial.　　Steelwastheanswertothisdemand.TheinventionoftheBessemerconverterin1856andthesubsequentdevelopmentoftheSiemens-Martinopen-hearthprocessformakingsteelmadeitpossibletoproducestructuralsteelatcompetitivepricesandtriggeredthetremendousdevelopmentsandaccomplishmentsintheuseofstructuralsteeloverthenexthundred　　years.

　　Themostseriousdisadvantageofsteelisthatitoxidizeseasilyandmustbeprotectedbypaintorsomeothersuitablecoating.Whensteelisusedinanenclosurewhereafirecould　occur,thesteelmembersmustbeencasedinasuitablefire-resistantenclosuresuchasmasonry,concrete.Normally,steelmemberswillnotfailinabrittlemannerunlessanunfortunatecombinationofmetallurgicalcomposition,lowtemperature,andbi-ortriaxialstressexists.

　　Structuralaluminumisstillnotwidelyusedincivilengineeringstructures,thoughitsuse　issteadilyincreasing.Byaproperselectionofthealuminumalloyanditsheattreatment,a　widevarietyofstrengthcharacteristicsmaybeobtained.Someofthealloysexhibit　stress-straincharacteristicssimilarthoseofstructuralsteel,exceptthatthemodulusofelasticityfortheinitiallinearlyelasticportionisabout10,000,000psi（700,000kgf/cm*cm）oraboutone-thirdthatofsteel.Lightnessandresistancetooxidationare,ofcourse,twoofthemajoradvantagesofaluminum.Becauseitspropertiesareverysensitivetoitsheattreatment,care　mustbeusedwhenrivetingorweldingaluminum.Severaltechniqueshavebeendevelopedforprefabricatingaluminumsubassembliesthatcanbereadilyerectedandboltedtogetherinthe　fieldtoformanumberofbeautifulandwell-designedshellstructures.Thisgeneralprocedure　ofprefabricationandheldassemblybyboltingseemstobethemostpromisingwayofutilizingstructuralaluminum.

　　Reinforcedandprestessesconcretesharewithstructuralmaterial.Naturalcement　concreteshavebeenusedforcenturies.Modernconcreteconstructiondatesfromthemiddleof　thenineteenthcentury,thoughartificialPortlandcementwaspatentedbyAspidin,an　Englishman,about1825.Althoughseveralbuildersandengineersexperimentedwiththeuseofsteel-reinforcedconcreteinthelasthalfofthenineteenthcentury,itsdominantuseasa　buildingmaterialdatesfromtheearlydecadesofthetwentiethcentury.Thelastfiftyyears　haveseentherapidandvigorousdevelopmentofprestressedconcretedesignandconstruction,foundedlargelyonearlyworkbyFreyssinetinFranceandMagnelinBelgium.

　　Plain（unreinforced）concretenotonlyisaheterogeneousmaterialbutalsohasoneveryseriousdefectasastructuralmaterial,namely,itsverylimitedtensilestrength,whichisonlyoftheorderofone-tenthitscompressivestrength.Notonlyistensilefailureinconcreteofa　brittletype,butlikewisecompressionfailureoccursinarelativelybrittlefashionwithoutbeingprecededbytheforewarningoflargedeformations.（Ofcourse,inreinforced-concreteconstruction,ductilebehaviorcanbeobtainedbyproperselectionandarrangementofthereinforcement.）Unlesspropercareisusedintheselectionofaggregatesandinthemixingandplacingofconcrete,frostactioncancauseseriousdamagetoconcretemasonry.Concrete　creepsunderlong-termloadingtoadegreethatmustbeconsideredcarefullyinselectingthedesignstressconditions.Duringthecuringprocessanditsearlylife,concreteshrinksa　significantamount,whichtoadegreecanbecontrolledbyproperlyproportioningthemixandutilizingsuitableconstructiontechniques.

　　Withallthesepotentiallyseriousdisadvantages,engineershavelearnedtodesignand　buildbeautiful,durable,andeconomicalreinforced-concretestructuresforpracticallyallkinds　ofstructuralrequirements.Thishasbeenaccomplishedbycarefulselectionofthedesigndimensionsandthear