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外文翻译.docx
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外文翻译
重庆科技学院学生毕业设计(论文)
外文译文
学院建筑工程学院
专业班级土木工程2012级3班
学生姓名张乐
学号2012442844
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RecentResearchandDesignDevelopmentsinSteelandCompositeSteel-concreteStructuresinUSA
Thepaperwillconcludewithalooktowardthefutureofstructuralsteelresearch.
1.Researchonsteelbridges
TheAmericanAssociationofStateTransportationandHighwayOfficials(AASTHO)istheauthoritythatpromulgatesdesignstandardsforbridgesintheUS.In1994ithasissuedanewdesignspecificationwhichisaLimitStatesDesignstandardthatisbasedontheprinciplesofreliabilitytheory.Agreatdealofworkwentintothedevelopmentofthiscodeinthepastdecade,especiallyoncalibrationandontheprobabilisticevaluationofthepreviousspecification.Thecodeisnowbeingimplementedinthedesignoffice,togetherwiththeintroductionoftheSystemeInternationaleunits.Manyquestionsremainopenaboutthenewmethodofdesign,andtherearemanynewprojectsthatdealwiththereliabilitystudiesofthebridgeasasystem.Onesuchcurrentprojectisastudytodevelopprobabilisticmodels,loadfactors,andrationalload-combinationrulesforthecombinedeffectsoflive-loadandwind;live-loadandearthquake;live-load,windandshipcollision;andshipcollision,wind,andscour.Therearealsomanyfieldmeasurementsofbridgebehavior,usingmoderntoolsofinspectionandmonitoringsuchasacousticemissiontechniquesandothermeansofnon-destructiveevaluation.Suchfieldworknecessitatesparallelstudiesinthelaboratory,andtheevolutionofevermoresophisticatedhigh-technologydatatransmissionmethods.
Americahasanagingsteelbridgepopulationandmanyproblemsarisefromfatigueandcorrosion.Fatiguestudiesonfull-scalecomponentsoftheWilliamsburgBridgeinNewYorkhaverecentlybeencompletedatLehighUniversity.AprobabilisticAASTHObridgeevaluationregulationhasbeenineffectsince1989,anditisemployedtoassessthefutureusefullifeofstructuresusingrationalmethodsthatincludefieldobservationandmeasurementtogetherwithprobabilisticanalysis.Suchanactivityalsofostersadditionalresearchbecausemanyissuesarestillunresolved.Onesuchareaisthestudyoftheshakedownofshearconnectorsincompositebridges.ThisworkhasbeenrecentlycompletedattheUniversityofMissouri.
Inadditiontofatigueandcorrosion,themajordangertobridgesisthepossibilityofearthquakeinduceddamage.Thisalsohasspawnedmanyresearchprojectsontherepairandretrofitofsteelsuperstructuresandthesupportingconcretepiers.Manybridgesinthecountryarebeingstrengthenedforearthquakeresistance.Oneareathatisreceivingmuchresearchattentionisthestrengtheningofconcretepiersby"jacketing"thembysheetsofhigh-performancereinforcedplastic.
Thepreviouslydescribedresearchdealsmainlywiththebehaviorofexistingstructuresandthedesignofnewbridges.However,thereisalsoavigorousactivityonnovelbridgesystems.Thisresearchiscenteredontheapplicationofhigh-performancesteelsforthedesignofinnovativeplateandbox-girderbridges,suchascorrugatedwebs,combinationsofopenandclosedshapes,andlongerspansfortrussbridges.Itshouldbementionedherethat,inadditiontoworkonsteelbridges,thereisalsoveryactiveresearchgoingoninthestudyofthebehaviorofprestressedconcretegirdersmadefromveryhighstrengthconcrete.Theperformanceanddesignofsmallerbridgesusingpultrudedhigh-performanceplasticcompositemembersisalsobeingstudiedextensivelyatpresent.Newcontinuousbridgesystemswithsteelconcretecompositesegmentsinboththepositivemomentandthenegativemomentregionsarebeingconsidered.Severalresearchershavedevelopedstrongcapabilitiestomodelthethree-dimensionalnon-linearbehaviorofindividualplategirders,andmanystudiesarebeingperformedonthebucklingandpost-bucklingcharacteristicsofsuchstructures.Companionexperimentalstudiesarealsomade,especiallyonmembersbuiltfromhigh-performancesteels.Afull-scalebridgeofsuchsteelhasbeendesigned,andwillsoonbeconstructedandthentestedundertrafficloading.Researcheffortsarealsounderwayonthestudyofthefatigueoflargeexpansionjointelementsandonthefatigueofhighwaysignstructures.
Thefinalsubjecttobementionedistheresurgenceofstudiesofcompositesteelconcretehorizontallycurvedsteelgirderbridges.AjustcompletedprojectattheUniversityofMinnesotamonitoredthestressesandthedeflectionsinaskewedandcurvedbridgeduringallphasesofconstruction,startingfromthefabricationyardtothecompletedbridge.~Excellentcorrelationwasfoundtoexistbetweenthemeasuredstressesanddeformationsandthecalculatedvalues.Thestressesanddeflectionsduringconstructionwerefoundtoberelativelysmall,thatis,theconstructionprocessdidnotcauseseveretraumatothesystem.Thebridgehasnowbeentestedunderserviceloading,usingfullyloadedgraveltrucks,fortwoyears,anditwillcontinuetobestudiedforfurtheryearstomeasurechangesinperformanceunderserviceovertime.AmajortestingprojectisbeingconductedattheFederalHighwayAdministrationlaboratoryinWashington,DC,whereahalf-scalecurvedcompositegirderbridgeiscurrentlybeingtestedtodetermineitslimitstates.Thetest-bridgewasdesignedtoactasitsowntest-frame,wherevariousportionscanbereplacedaftertesting.Multipleflexuretests,sheartests,andtestsundercombinedbendingandshear,arethusperformedwithrealisticend-conditionsandrestraints.Theexperimentsarealsomodeledbyfiniteelementanalysistocheckconformancebetweenrealityandprediction.Finallydesignstandardswillbeevolvedfromtheknowledgegained.ThislastprojectisthelargestbridgeresearchprojectintheUSAatthepresenttime.
Fromthediscussionaboveitcanbeseenthateventhoughthereisnolargeexpansionofthenation'shighwayandrailroadsystem,thereisextensiveworkgoingoninbridgeresearch.Themajorchallengefacingboththeresearcherandthetransportationengineeristhemaintenanceofahealthybutagingsystem,seeingtoitsgradualreplacementwhilekeepingitsafeandserviceable.
2.Researchonsteelmembersandframes
Therearemanyresearchstudiesonthestrengthandbehaviorofsteelbuildingstructures.Themostimportantofthesehavetodowiththebehavioranddesignofsteelstructuresundersevereseismicevents.Thistopicwillbediscussedlaterinthispaper.Themostsignificanttrendsofthenon-seismicresearcharethefollowing:
"Advanced"methodsofstructuralanalysisanddesignareactivelystudiedatmanyUniversities,notablyatCornell,Purdue,Stanford,andGeorgiaTechUniversities.Suchanalysismethodsaremeanttodeterminetheload-deformationbehaviorofframesuptoandbeyondfailure,includinginelasticbehavior,forceredistribution,plastichingeformation,second-ordereffectsandframeinstability.Whenthesemethodsarefullyoperational,thestructurewillnothavetoundergoamembercheck,becausethefiniteelementanalysisoftheframeautomaticallyperformsthisjob.Inadditiontotheresearchonthebestapproachestodothisadvancedanalysis,therearealsomanystudiesonsimplificationsthatcanbeeasilyutilizedinthedesignofficewhilestillmaintainingtheadvantagesofamorecomplexanalysis.Theadvancedanalysismethodiswelldevelopedforin-planebehavior,butmuchworkisyettobedoneonthecaseswherebi-axialbendingorlateraltorsionalbucklingmustbeconsidered.Somesuccesseshavebeenachieved,buttheresearchisfarfromcomplete.
Anotheraspectoftheframebehaviorworkisthestudyoftheframeswithsemirigidjoints.TheAmericanInstituteofSteelConstruction(AISC)haspublisheddesignmethodsforofficeuse.Currentresearchisconcentratingonthebehaviorofsuchstructuresunderseismicloading.Itappearsthatitispossibletousesuchframesinsomeseismicsituations,thatis,framesunderabout8to10storiesinheightundermoderateearthquakeloads.Thefutureofstructureswithsemi-rigidframeslooksverypromising,mainlybecauseoftheeffortsofresearcherssuchasLeonatGeorgiaTechUniversity,andmanyothers.
Researchonmemberbehaviorisconcernedwithstudyingthebucklingandpostbucklingbehaviorofcompactangleandwide-flangebeammembersbyadvancedcommercialfiniteelementprograms.Suchresearchisgoingbacktoexaminetheassumptionsmadeinthe1950sand1960swhentheplasticdesigncompactnessandbracingrequirementswerefirstformulatedonasemi-empiricalbasis.Thenon-linearfiniteelementcomputationspermitthe"re-testing"oftheoldexperimentsandtheperformingofnewcomputerexperimentstostudynewtypesofmembersandnewtypesofsteels.WhiteofGeorgiaTechisoneofthepioneersinthiswork.SomecurrentresearchattheUSmilitaryAcademyandattheUniversityofMinnesotabyEarlsisdiscussedlaterinthisreport.Thesignificanceofthistypeofresearchisthatthephenomenaofextremeyieldinganddistortioncanbeefficientlyexaminedinparameterstudiesperformedonthecomputer.Thecomputerresultscanbeverifiedwitholdexperiments,orasmallnumberofnewexperiments.Thesestudiesshowagoodprospectfornewinsightsintooldproblemsthatheretoforewereneverfullysolved.
3.Researchoncold-formedsteelstructures
Nexttoseismicwork,themostactivepartofresearchintheUSisoncold-formedsteelstructures.Thereasonforthisisthatthesupportingindustryisexpanding,especial
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