土木工程毕业设计中英文翻译.docx

土木工程毕业设计中英文翻译.docx

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土木工程毕业设计中英文翻译

土木工程毕业设计中英文翻译

附录:

中英文翻译

英文部分:

LOADS

Loadsthatactonstructuresareusuallyclassifiedasdeadloadsorliveloads.Deadloadsarefixedinlocationandconstantinmagnitudethroughoutthelifeofthestructure.Usuallytheself-weightofastructureisthemostimportantpartofthestructureandtheunitweightofthematerial.Concretedensity

2variesfromabout90to120pcf（14to19）forlightweightconcrete,andisabout145pcf（23KN/m

2）fornormalconcrete.Incalculatingthedeadloadofstructuralconcrete,usuallya5pcf（1KN/m

2）incrementisincludedwiththeweightoftheconcretetoaccountforthepresenceoftheKN/m

reinforcement.

Liveloadsareloadssuchasoccupancy,snow,wind,ortrafficloads,orseismicforces.Theymaybeeitherfullyorpartiallyinplace,ornotpresentatall.Theymayalsochangeinlocation.

Althoughtitistheresponsibilityoftheengineertocalculatedeadloads,liveloadsareusuallyspecifiedbylocal,regional,ornationalcodesandspecifications.TypicalsourcesarethepublicationsoftheAmericanNationalStandardsInstitute,theAmericanAssociationofStateHighwayandTransportationOfficialsand,forwindloads,therecommendationsoftheASCETaskCommitteeonWindForces.

Specifiedlivetheloadsusuallyincludesomeallowanceforoverload,andmayincludemeasuressuchaspostingofmaximumloadswillnotbeexceeded.Itisofternimportanttodistinguishbetweenthespecifiedload,andwhatistermedthecharacteristicload,thatis,theloadthatactuallyisineffectundernormalconditionsofservice,whichmaybesignificantlyless.Inestimatingthelong-termdeflectionofastructure,forexample,itisthecharacteristicloadthatisimportant,notthespecifiedload.

Thesumofthecalculateddeadloadandthespecifiedliveloadiscalledtheserviceload,becausethisisthemaximumloadwhichmayreasonablybeexpectedtoactduringtheserviceresistingisamultipleoftheserviceload.

Strength

Thestrengthofastructuredependsonthestrengthofthematerialsfromwhichitismade.Minimummaterialstrengthsarespecifiedincertainstandardizedways.Thepropertiesofconcreteanditscomponents,themethodsofmixing,placing,andcuringtoobtaintherequiredquality,andthemethodsfortesting,arespecifiedbytheAmericanConcreteInsititue（ACI）.Includedbyrefrenceinthesamedocument

arestandardsoftheAmericanSocietyforTestingMaterials（ASTM）pertainingtoreinforcingandprestressingsteelsandconcrete.

Strengthalsodependsonthecarewithwhichthestructureisbuilt.Membersizesmaydifferfromspecifieddimensions,reinforcementmaybeoutofposition,orpoorplacementofconcretemayresultinvoids.Animportantpartofthejoboftheergineeristoprovidepropersupervisionofconstruction.Slightingofthisresponsibilityhashaddisastrousconsequencesinmorethanoneinstance.

StructuralSafety

Safetyrequiresthatthestrengthofastructurebeadequateforallloadsthatmayconceivablyactonit.Ifstrengthcouldbepredictedaccuratelyandifloadswereknownwithequalcertainty,thensafelycouldbeassuredbyprovidingstrengthjustbarelyinexcessoftherequirementsoftheloads.Buttherearemanysourcesofuncertaintyintheestimationofloadsaswellasinanalysis,design,andconstruction.Theseuncertaintiesrequireasafetymargin.

Inrecentyearsengineershavecometorealizethatthematterofstructuralsafetyisprobabilisticinnature,andthesafetyprovisionsofmanycurrentspecificationsreflectthisview.

Separateconsiderationisgiventoloadsandstrength.Loadfactors,largerthanunity,areappliedtothecalculateddeadloadsandestimatedorspecifiedserviceliveloads,toobtainfactordeloadsthatthemembermustjustbecapableofsustainingatincipientfailure.Loadfactorspertainingtodifferenttypesofloadsvary,dependingonthedegreeofuncertaintyassociatedwithloadsofvarioustypes,andwiththelikelihoodofsimultaneousoccurrenceofdifferentloads.

Earlyinthedevelopmentofprestressedconcrete,thegoalofprestressingwasthecompleteeliminationofconcreteternsilestressatserviceloads.Theconceptwasthatofanentirelynew,homogeneousmaterialthatwoukdremainuncrackedandrespondelasticallyuptothemaximumanticipatedloading.Thiskindofdesign,wherethelimitingtensilestressing,whileanalternativeapproach,inwhichacertainamountoftensileamountoftensilestressispermittedintheconcreteatfullserviceload,iscalledpartialprestressing.

Therearecasesinwhichitisnecessarytoavoidallriskofcrackingandinwhichfullprestressingisrequired.Suchcasesincludetanksorreserviouswhereleaksmustbeavoided,submergedstructuresorthosesubjecttoahighlycorrosiveenvionmentwheremaximumprotectionofreinforcementmustbeinsured,andstructuressubjecttohighfrequencyrepetitionofload