毕业论文之建筑

附录一、英文原文BuildingAbstract:Therearealotofbuildinghistoryandhistoricalbuildings,andthedevelopmentofsuchasbuildingmaterialsandsoon.Tillnowwehaveabettertechnologyandscienceaboutbuilding.Keywords:modernbuildingsandstructuralmaterials,buildingtypesanddesign,componentsofabuilding.ModernBuildingsandStructuralMaterialsManygreatbuildingsbuiltinearlieragesarestillinexistenceandinuse.AmongthemarethePantheonandColosseuminRome,HagiaSophiainIstanbul;theGothicchurchesofFranceandEngland,andtheRenaissancecathedrals,withtheirgreatdomes,liketheDuomoinFlorenceandSt.Peter’sinRome.Theyaremassivestructureswiththickstonewallsthatcounteractthethrustofthegreatweight.Thrustisthepressureexertedbyeachpartofastructureonitsotherparts.Thesegreatbuildingswerenottheproductsofknowledgeofmathematicsandphysics.Theywereconstructedinsteadofthebasisofexperienceandobservation,oftenastheresultoftrialanderror.Oneofthereasonstheyhavesurvivedisbecauseofthegreatstrengththatwasbuiltintothem-strengthgreaterthannecessaryinmostcases.Buttheengineersofearliertimesalsohadtheirfailure.InRome,forexample,mostofthepeoplelivedininsula,greattenementblocksthatwereoftentenstorieshigh.Manyofthemwerepoorlyconstructedandsometimescollapsedwithconsiderablelossoflife.Today,however,theengineerhastheadvantagenotonlyofempiricalinformation,butalsoofscientificdatathatpermithimtomakecarefulcalculationsinadvance.Whenamodernengineerplansastructure,hetakesintoaccountthetotalweightofallitscomponentmaterials.Thisisknownasthedeadload,whichistheweightofthestructureitself.Hemustalsoconsidertheliveload,theweightofallthepeople,cars,furniture,machines,andsoonthatthestructurewillsupportwhenitisinuse.Instructuressuchasbridgesthatwillhandlefastautomobiletraffic,hemustconsidertheimpact,theforceatwhichtheliveloadwillbeexertedonthestructure.Hemustalsodeterminethesafetyfactor,thatis,anadditionalcapabilitytomakethestructurestrongerthanthecombinationofthethreeotherfactors.Themodernengineermustalsounderstandthedifferentstresstowhichthematerialsinastructurearesubject.Theseincludetheoppositeforcesofcompressionandtension,Incompressionthematerialispressedorpushedtogether;intensionthematerialispulledapartorstretched,likearubberband.Inadditiontotensionandcompression,anotherforceisatwork,namelyshear,whichwedefinedasthetendencyofamaterialtofracturealongthelinesofstress.Theshearmightoccurinaverticalplane,butitalsomightrunalongthehorizontalaxisofthebeam,theneutralplane,wherethereisneithertensionnorcompression.Altogether,threeforcescanactonastructure:vertical-thosethatactupordown;horizontal-thosethatactsideways;andthosethatactuponitwitharotatingorturningmotion.Forcesthatactatanangleareacombinationofhorizontalandverticalforces.Sincethestructuresdesignedbycivilengineersareintendedtobestationaryorstable,theseforcesmustbekeptinbalance.Theverticalforces,forexample,mustbeequaltoeachother.Ifabeamsupportsaloadabove,thebeamitselfmusthavesufficientstrengthtocounterbalancethatweight.Thehorizontalforcesmustalsoequaleachothersothatthereisnottoomuchthrusteithertotherightortotheleft.Andforcesthatmightpullthestructurearoundmustbecounteredwithforcesthatpullintheoppositedirection.Oneofthemostspectacularengineeringfailuresofmoderntimes,thecollapseoftheTacomaNarrowsBridgein1904,wastheresultofnotconsideringthelastofthesefactorscarefullyenough.Whenstronggustsofwind,uptosix-fivekilometersanhour,struckthebridgeandalsoalateralmotionthatcausedtheroadwaytofall.Fortunately,engineerslearnfrommistakes,soitisnowcommonpracticetotestscalemodelsofbridgesinwindrunnelsforaerodynamicresistance.Theprincipalconstructionmaterialsofearliertimeswerewoodandmasonrybrick,stone,ortile,andsimilarmaterials.TheGreeksandRomanssometimesusedironrodsorclampstostrengthentheirbuildings.ThecolumnsoftheParthenoninAthens,forexample,haveholesdrilledinthemforironbarsthathavenowrustedaway.TheRomansalsousedanaturecementcalledpozzolana,madefromvolcanicash,thatbecomeashardasstoneunderwater.Bothsteelandcement,thetwomostimportantconstructionmaterialsofmoderntimes,wereintroducedinthenineteenthcentury.Steel,basicallyanalloyofironandasmallamountofcarbon,hadbeenmadeuptothattimebyalaboriousprocessthatrestrictedittosuchspecialusesasswordblades.AftertheinventionoftheBessemerprocessin1856,steelwasavailableinlargequantitiesatlowprices.Theenormousadvantageofsteelisitstensilestrength;thatis,itdoesnotloseitsstrengthwhenitisunderacalculateddegreeoftension,aforcewhich,aswehaveseen,tendstopullapartmanymaterials.Newalloyshavefurtherincreasedthestrengthofsteelandeliminatedsomeofitsproblems,suchasfatigue,whichisatendencyforittoweakenasaresultofcontinualchangesinstress.Moderncement,calledPortlandcement,wasinventedin1824.Itisamixtureoflimestoneandclay,whichisheatedandthengroundintoapowder.Itismixedatorneartheconstructionsitewithsand,aggregate(smallstones,crushedrocks,orgravel),andwatertomakeconcrete.differentstrengthandweight.Concreteisveryversatile;itcanbepoured,orevensprayedintoallkindsofshapes.Andwhereassteelhasgreattensilestrength,concretehasgreatstrengthundercompression.Thus,thetwosubstances