土木工程类外文文献翻译钢筋混凝土可编辑.docx
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土木工程类外文文献翻译钢筋混凝土可编辑.docx
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土木工程类外文文献翻译钢筋混凝土可编辑
土木工程类外文文献翻译---钢筋混凝土
外文文献翻译
院系_________________________
班级_________________________
姓名_________________________
指导教师_________________________
2012年2月20日
2外文翻译
21ReinforcedConcrete
PlainconcreteisformedfromahardenedmixtureofcementwaterfineaggregatecoarseaggregatecrushedstoneorgravelairandoftenotheradmixturesTheplasticmixisplacedandconsolidatedintheformworkthencuredtofacilitatetheaccelerationofthechemicalhydrationreactionlfthecementwatermixresultinginhardenedconcreteThefinishedproducthashighcompressivestrengthandlowresistancetotensionsuchthatitstensilestrengthisapproximatelyonetenthlfitscompressivestrengthConsequentlytensileandshearreinforcementinthetensileregionsofsectionshastobeprovidedtocompensatefortheweaktensionregionsinthereinforcedconcreteelement
ItisthisdeviationinthecompositionofareinforcesconcretesectionfromthehomogeneityofstandardwoodorsteelsectionsthatrequiresamodifiedapproachtothebasicprinciplesofstructuraldesignThetwocomponentsoftheheterogeneousreinforcedconcretesectionaretobesoarrangedandproportionedthatoptimaluseismadeofthematerialsinvolvedThisispossiblebecauseconcretecaneasilybegivenanydesiredshapebyplacingandcompactingthewetmixtureoftheconstituentingredientsareproperlyproportionedthefinishedproductbecomesstrongdurableandincombinationwiththereinforcingbarsadaptableforuseasmainmembersofanystructuralsystem
ThetechniquesnecessaryforplacingconcretedependonthetypeofmembertobecastthatiswhetheritisacolumnabeanawallaslabafoundationamasscolumnsoranextensionofpreviouslyplacedandhardenedconcreteForbeamscolumnsandwallstheformsshouldbewelloiledaftercleaningthemandthereinforcementshouldbeclearedofrustandotherharmfulmaterialsInfoundationstheearthshouldbecompactedandthoroughlymoistenedtoabout6inindepthtoavoidabsorptionofthemoisturepresentinthewetconcreteConcreteshouldalwaysbeplacedinhorizontallayerswhicharecompactedbymeansofhighfrequencypower-drivenvibratorsofeithertheimmersionorexternaltypeasthecaserequiresunlessitisplacedbypumpingItmustbekeptinmindhoweverthatovervibrationcanbeharmfulsinceitcouldcausesegregationoftheaggregateandbleedingoftheconcrete
Hydrationofthecementtakesplaceinthepresenceofmoistureattemperaturesabove50°FItisnecessarytomaintainsuchaconditioninorderthatthechemicalhydrationreactioncantakeplaceIfdryingistoorapidsurfacecrackingtakesplaceThiswouldresultinreductionofconcretestrengthduetocrackingaswellasthefailuretoattainfullchemicalhydration
ItisclearthatalargenumberofparametershavetobedealtwithinproportioningareinforcedconcreteelementsuchasgeometricalwidthdepthareaofreinforcementsteelstrainconcretestrainsteelstressandsoonConsequentlytrialandadjustmentisnecessaryinthechoiceofconcretesectionswithassumptionsbasedonconditionsatsiteavailabilityoftheconstituentmaterialsparticulardemandsoftheownersarchitecturalandheadroomrequirementstheapplicablecodesandenvironmentalreinforcedconcreteisoftenasite-constructedcompositeincontrasttothestandardmill-fabricatedbeamandcolumnsectionsinsteelstructures
AtrialsectionhastobechosenforeachcriticallocationinastructuralsystemThetrialsectionhastobeanalyzedtodetermineifitsnominalresistingstrengthisadequatetocarrytheappliedfactoredloadSincemorethanonetrialisoftennecessarytoarriveattherequiredsectionthefirstdesigninputstepgeneratesintoaseriesoftrial-and-adjustmentanalyses
Thetrial-and–adjustmentproceduresforthechoiceofaconcretesectionleadtotheconvergenceofanalysisanddesignHenceeverydesignisananalysisonceatrialsectionischosenTheavailabilityofhandbookschartsandpersonalcomputersandprogramssupportsthisapproachasamoreefficientcompactandspeedyinstructionalmethodcomparedwiththetraditionalapproachoftreatingtheanalysisofreinforcedconcreteseparatelyfrompuredesign
22Earthwork
BecauseearthmovingmethodsandcostschangemorequicklythanthoseinanyotherbranchofcivilengineeringthisisafieldwheretherearerealopportunitiesfortheenthusiastIn1935mostofthemethodsnowinuseforcarryingandexcavatingearthwithrubber-tyredequipmentdidnotexistMostearthwasmovedbynarrowrailtracknowrelativelyrareandthemainmethodsofexcavationwithfaceshovelbackacterordraglineorgrabthoughtheyarestillwidelyusedareonlyafewofthemanycurrentmethodsTokeephisknowledgeofearthmovingequipmentuptodateanengineermustthereforespendtinestudyingmodernmachinesGenerallytheonlyreliableup-to-dateinformationonexcavatorsloadersandtransportisobtainablefromthemakers
EarthworksorearthmovingmeanscuttingintogroundwhereitssurfaceistoohighcutsanddumpingtheearthinotherplaceswherethesurfaceistoolowfillsToreduceearthworkcoststhevolumeofthefillsshouldbeequaltothevolumeofthecutsandwhereverpossiblethecutsshouldbeplacedneartofillsofequalvolumesoastoreducetransportanddoublehandlingofthefillThisworkofearthworkdesignfallsontheengineerwholaysouttheroadsinceitisthelayoutoftheearthworkmorethananythingelsewhichdecidesitscheapnessFromtheavailablemapsahdlevelstheengineeringmusttrytoreachasmanydecisionsaspossibleinthedrawingofficebydrawingcrosssectionsoftheearthworkOnthesitewhenfurtherinformationbecomesavailablehecanmakechangesinjissectionsandlayoutbutthedrawinglfficeworkwillnothavebeenlostItwillhavehelpedhimtoreachthebestsolutionintheshortesttime
ThecheapestwayofmovingearthistotakeitdirectlyoutofthecutanddropitasfillwiththesamemachineThisisnotalwayspossiblebutwhenitcanbedoneitisidealbeingbothquickandcheapDraglinesbulldozersandfaceshovelsandothisThelargestradiusisobtainedwiththedraglineandthelargesttonnageofearthismovedbythebulldozerthoughonlyovershortdistancesThedisadvantagesofthedraglinearethatitmustdigbelowitselfitcannotdigwithforceintocompactedmaterialitcannotdigonsteepslopwsanditsdumpinganddiggingarenotaccurate
FaceshovelsarebetweenbulldozersanddraglineshavingalargerradiusofactionthanbulldozersbutlessthandraglinesTheyareanletodigintoaverticalclifffaceinawaywhichwouldbedangeroustorabulldozeroperatorandimpossibleforadraglineEachpieceofequipmentshouldbeleveloftheirtracksandfordeepdigsincompactmaterialabackacterismostusefulbutitsdumpingradiusisconsiderablylessthanthatofthesameescavatorfittedwithafaceshovel
Rubber-tyredbowlscrapersareindispensableforfairlyleveldiggingwherethedistanceoftransportistoomuchtoradraglineorfaceshovelTheycandigthematerialdeeplybutonlybelowthemselvestoafairlyflatsurfacecarryithundredsofmetersifneedbethendropitandlevelitroughlyduringthedumpingForharddiggingitisoftenfoundeconomicaltokeepapushertractorwheeledortrackedonthediggingsitetopusheachscraperasitreturnstodigAssoonasthescraperisfullthepushertractorreturnstothebeginningofthedigtoheoptohelpthenestscraper
Bowlscrapersareoftenextremelypowerfulmachinesmanymakersbuildscrapersof8cubicmetersstruckcapacitywhichcarry10m3heapedThelargestself-propelledscrapersareof19m3struckcapacity25m3heapedandtheyaredrivenbyatractorengineof430horse-powers
Dumpersareprobablythecommonestrubber-tyredtransportsincetheycanalsoconvenientlybeusedforcarryingconcreteorotherbuildingmaterialsDumpershavetheearthcontaineroverthefrontaxleonlargerubber-tyredwheelsandthecontainertipsforwardsonmosttypesthoughinarticulateddumpersthedirectionoftipcanbewidelyvariedThesmallestdumpershaveacapacityofabout05m3andthelargeststandardtypesareofabout45m3Specialtypesincludetheself-loadingdumperofupto4m3andthearticulatedtypeofabout05m3ThedistinctionbetweendumpersanddumptrucksmustberemembereddumperstipforwardsandthedriversitsbehindtheloadDumptrucksareheavystrengthenedtippinglorriesthedrivertravelsinfrontlftheloadandtheloadisdumpedbehindhimsotheyaresometimescalledrear-dumptrucks
23SafetyofStructures
TheprincipalscopeofspecificationsistoprovidegeneralprinciplesandcomputationalmethodsinordertoverifysafetyofstructuresThesafetyfactorwhichaccordingtomoderntrendsisindependentofthenatureandcombinationofthematerialsusedcanusuallybedefinedastheratiobetweentheconditionsThisratioisalsoproportionaltotheinverseoftheprobabilityriskoffailureofthestructure
FailurehastobeconsiderednotonlyasoverallcollapseofthestructurebutalsoasunserviceabilityoraccordingtoamorepreciseCommondefinitionAsthereachingofalimitstatewhichcausestheconstructionnottoaccomplishthetaskitwasdesignedforTherearetwocategoriesoflimitstate
1Ultimatelimitsatewhichcorrespondstothehighestvalueoftheload-bearingcapacityExamplesincludelocalbucklingorglobalinstabilityofthestructurefailureofsomesectionsandsubsequenttransformationofthestructureintoamechanismfailurebyfatigueelasticorplasticdeformationorcreepthatcauseasubstantialchangeofthegeometryofthestructureandsensitivityofth
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