土木工程类外文文献翻译钢筋混凝土可编辑.docx

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