任全福英语翻译

Itissaidthatnecessityisthemotherofallinvention.Ifthatisthecase,thentheneedforstriking,elegantcable-stayedbridgesthatcanspangreaterlengthsandbemoreeasilymaintainedoverthecourseoflongerliveshasyieldedasignificantnewinventionthatmaywellbenefitbridgedesignerstheworldover.Drivenbyadesiretopushthedesignofsingle-planecable-stayedbridgesbeyondtheircurrentlimits—bothinspanlengthandinaestheticappeal—whilestilldeliveringaneconomicsolutionthatiseasytoconstructandmaintain,FIGG,anengineeringfirmbasedinTallahassee,Florida,hascreatedanovelsystemforroutingstaycablesfromoneendofabridgedeck,throughthebridge’spylon,andthendowntotheotherendofthedeckinawaythatprecludesthepossibilityofcable-to-cableinteractions.Theinnovationhasbeenemployedontwonewbridges—theVeterans’GlassCitySkywayBridge,whichcarriesInterstate280acrosstheMaumeeRiverinToledo,Ohio(see“OhioDOTEndorsesDesignforMaumeeRiverCrossing,”CivilEngineering,September2000,page12),andthePenobscotNarrowsBridgeandObservatory,whichcarriesU.S.Route1overthePenobscotRiverinsoutheastern(“downeast”)Mainenearthecoastline(see“ObservatorytoCapMaineCrossing,”CivilEngineering,April2004,pages15–17).Thecradleoffersbenefitsbothduringconstructionandoverthelifeofthebridges.Mostimportantofall,itpermitstheuseofthelargestnumberofstrandswithinasinglestaycableintheworld:156,anincreaseofmorethan70percentoverthesecond-highestnumberknowntohavebeenusedintheUnitedStates.Italsomakesitpossibletoincreasethedistancebetweenstaycablesbyapproximately50percentwhenusedwithprecastdeltaframestofacilitateasingleplaneofstaycables,resultinginaestheticallysuperiordesigns.Thisisaccomplishedbyhavingallthestrandsparallelastheytravelfromtheanchorsatthedecklevelthroughthecradleinthepylonandbacktothedeck.Individualsleevepipeslocatedwithinthecradlesystemenableeachstrandtoactindependentlyofadjacentstrands.Thisalsopermitsthecablestobemuchlargerandtobespacedfartherapart,whichtranslatesintolongerspans.Furthermore,thecradlesystemlowersinitialcostsbyreducingtheamountofmaterialsandlaborneededbecausenoanchoragesinthepylonarerequired.Thissimplifiesconstructionoperationsbyallowingallofthecable-stressingoperationstobeperformedatthebridgedecklevelratherthanwithinthe(oftenrestricted)confinesofthepylon,highabovethebridgedeck.Thesystemalsoincludesremovable“reference”strandsineachstaycablethatprovideasimple,reliablemethodforverifyingtheconditionofthestaycablesinthefuture.Becausethecradlesystemdoesnotrequirestrandstobegrouted,theycanbeindividuallyremoved,inspected,andreplaced,evenwhenthereistrafficonthebridge.Bridgeownerscanthussafelyandaccuratelyassesstheconditionsofthestaycablesatanytimeoverthecourseofthebridge’slife.InthecaseoftheMainebridge,newstrandmaterialscanbetestedside-by-sidewithtraditionalmaterialsinanactualsetting,asopposedtoaprocessofcomputersimulation.Whatismore,thecradlesystemmakespossibletheuseofawidervarietyofpylondesigns—somewithmuchsmallerandmoreelegantcross-sectionalshapes—thatcanbeconstructedmoreeconomically.Engineerscanthusdesignpylonsthatarefarmoreunusualandaestheticallypleasingthanhasbeenthecaseinthepast.Thecradledesignworkswiththenaturalflowofforcesbecausetheforcestransmittedthroughthecradlenaturallycompressthepyloninanefficientmanner,thestressesbeingappliedradiallyalongthecurveofthecradle(seetheillustrationsonpage41).Intraditionalsystems,anchorageswithinthepylonrequiredlargetensiontiestoresistthehighsplittingforcesthatwouldbegenerated.Usingthecradlesystemeliminatesthisrequirementandfurtherenhancestheeleganceofthepylonshapes.Thedevelopmentofthisnewtechniquebeganinearly2000.TheOhioDepartmentofTransportation(ODOT)andtheToledoMetropolitanAreaCouncilofGovernmentshadformedwhatwascalledtheMaumeeRiverCrossingTaskForceDesignCommitteetoassessandcommunicatethecommunities’perspectiveonthedevelopingdesign.Thetaskforcechoseglassasthethemeforthenewcable-stayedbridge.Meetingsinvolvingadiversecrosssectionofthecommunityhadmadethepublic’sviewsclear:thebridgewastofeatureglassinaveryvisibleandstrikingwayinrecognitionofToledo’sindustrialheritageasaleaderintheglassindustry.Manyfamiliesintheareahadworkedinthelocalglassindustryforgenerations,anditwasimportanttothemthatthecrossingbeasymbolofthe“GlassCity,”asToledohascometobeknown.Thepublicwasalsooftheopinionthatthebridgedesignshouldchampionaproductthathadbeenoftheutmostimportancetothearea’seconomy.Thetaskforcefurtherdeterminedthatresidentswantedthebridgedesigntobelight,simple,andelegant.FIGGledtwocommunityworkshops,ordesigncharettes,duringwhichthepublicwaspresentedwithavarietyofaestheticoptions.Communityvotingshowedaclearpreferenceforasingle-pylondesign.Theconsensuswasthatbycreatingasingletallpylon—403ft(123m)—usingglassonthetop196ft(60m)andonallfoursides,thenewbridgewouldbevisuallystunning.Inkeepingwiththisdirective,thetopofthepylontakesonaprismaticshape,itspanelsoftreatedglassreflectingsunlightduringthedayonallfoursides.Behindtheglassarelight-emittingdiodes(LEDS)thatenablethepylontostandasabeaconatnight.(Theledfixturesarecontrolledremotelyandcapableofliterallymillionsofcolorcombinations.Infact,variouscolorschemeshavebeenpreprogrammed,someschemesmarkingmajorholidaysandothersexhibitingteamcolorsforstatewidesportingevents.)有人说需求是一切发明的母亲。如果真的是这样，那么引人注目的，优雅的斜拉桥能够横跨更大的距离和使得桥梁在更长的使用寿命中的维护变得更简单将是一项可以让全球桥梁设计者都受益的重要的新发明。在推动单面斜拉桥超越现有极限（在跨度和美观两方面）的需求的驱使下，同时用一种在建造和维护过程中都经济的解决方法，FIGG，一家位于Florida首府Tallahassee的工程公司，发明了一个新颖的体系。该体系的斜拉索的传力路径是将力从桥面板的一端通过桥塔传下至桥面板的另一端。这种方法就可以排除斜拉索间互相作用的可能性。这种创新的方法被应用在两座新桥上。一座是老兵玻璃城航线大桥，这座大桥连接着280洲际公路横跨流经Toledo,Ohio的Maumee河；另一座是Penobscot纽约湾海峡大桥和天文台，这座大桥连接着美国1号公路横跨位于靠近海岸线的Maine洲东南面的Penobscot河。这个支架为桥梁的建造过程和其使用寿命中都带来了好处。最重要的是，它使得一根拉索中绳的股数达到了世界范围内的最大值：156。这个值比美国境内用过的第二多的股数多了70％。也使得当它用于预制的三角形框架（可使得单面斜拉索更方便）的斜拉索的距离增加大约50％成为了可能。这样就可以实现美学上的非凡设计。这是通过在绳股从桥面板水平面的支座穿过桥塔中的支架然后返回到桥面板过程中使得所有的绳股平行来实现的。位于支架系统内的独立套管使得每股绳都能不受相邻绳股的影响而单独作用。这也使拉索可以做得比以前大得多并且拉索间的距离也可以更大，也就是说桥梁可以横跨更大的距离。而且，由于桥塔内不需要支座所以材料的用量和人力的使用都减少了，从而支架系统降低了桥梁的初始成本。由于拉索的张拉操作都在桥面板上进行而不是在高高的桥塔上那么局限的范围内进行所以施工操作也变得简化了。这个体系还包括在每个斜拉索中都有可移动的参考绳股，这样为将来检验拉索的使用情况提供了一个简单可靠的方法。因为支架系统不要求用水泥浆添塞绳股，所以即使是在桥上有车辆和行人的情况下它们可以被单独地移除，检查和替换。这样一来桥梁的业主在桥梁的使用寿命期间随时都可以安全地，准确地对拉索的