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第1页共9页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第1页共9页Structures2008:CrossingBorders©2008ASCENewInnovativeFeaturesofMaine’sFirstCableStayBridgeAuthor:ChristopherJ.Burgess,P.E.,S.E.,FIGG,Denver,CO,cburgess@figgbridge.comThesteelsuspensionWaldo-HancockBridgecarriedU.S.Route1travelersoverthePenobscotRiver,nearthetownofBucksport,Mainefor74years.Thisvitallyimportanttransportationlinkprovidedsafepassageforcarloadsoftouriststhroughtheyears,inadditiontosignificantcommercialtrafficrelatedtoregionalpaper-making,granite-quarrying,boatbuilding,manufacturedhousingproductionandahostoffreightitems,suchasdeliveryofhomeheatingoil.In2002,ascheduledrenovationbeganandinthesummerof2003,themainsuspensioncableswereunwrappedtoprepareforavisualinspectionoftheindividualwiresinthe37cablesineachmaincable.Deteriorationofthemaincableonthesouthsideofthebridgewasmuchmoreadvancedthanexpected,leadingthebridgeowner,MaineDepartmentofTransportation,tosimultaneouslyundertakeastrengtheningprojectontheWaldo-HancockBridgeandthedesignofthePenobscotNarrowsBridge&Observatoryonaparallelalignmenttotheexistingbridge.FIGURE1THEWALDO-HANCOCKBRIDGEANDNEWPENOBSCOTNARROWSBRIDGE&OBSERVATORYSIDE-BY-SIDEOVERTHEPENOBSCOTRIVER,LINKINGWALDOANDHANCOCKCOUNTIESINMAINE.THENEWBRIDGEOPENEDTOTRAFFICONDECEMBER30,2006,JUST42MONTHSAFTERTHEEMERGENCYREPLACMENTNEEDWASIDENTIFIED.第2页共9页第1页共9页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第2页共9页Inordertospeedtheprocess,Maineundertookthereplacementinaninnovativeowner-facilitateddesignbuildprocessandgroundwasbrokeninDecemberof2003forthenewcable-stayedbridge,afirstforMaine.Akeyelementinthedesignofthenewcast-in-placeconcretesegmentalbridgeistheconsiderableattentionandeffortinvestedtoprovideadurableandeasytomaintainstructurewithaplannedservicelifeexceeding100years.Thebridgeisthefirsttoutilizeauniquecombinationoffeaturesdesignedspecificallytoprotectthebridgeandonlythesecondtobenefitfromapioneeringcradlesystem,developedandpatentedbythebridge’sdesigner.AninnovativenitrogengasprotectionandmonitoringsystemprovidesanFIGURE2ADJACENTCRADLESPOSITIONEDINTHEUPPERPYLONALONGWITHFORMWORK,ASTHEJUMPFORMSAREBEINGPREPAREDTOMOVEUPANDCASTTHENEXTSECTION.THECRADLESAREFABRICATED,DELIVEREDTOTHESITE,POSITIONEDANDSURVEYEDINPOSITIONINTHEFRAMEWORK,THENLIFTEDINTOPLACEANDTHEENTIREASSEMBLYSURVEYEDFORCORRECTPOSITIONINGPRIORTOCASTING.FIGURE1THEWALDO-HANCOCKBRIDGEANDNEWPENOBSCOTNARROWSBRIDGE&OBSERVATORYSIDE-BY-SIDEOVERTHEPENOBSCOTRIVER,LINKINGWALDOANDHANCOCKCOUNTIESINMAINE.THENEWBRIDGEOPENEDTOTRAFFICONDECEMBER30,2006,JUST42MONTHSAFTERTHEEMERGENCYREPLACMENTNEEDWASIDENTIFIED.第3页共9页第2页共9页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第3页共9页enclosedenvironmentofpressurizedinertgasaroundeachcablestay.Themaincomponentsofthesystemarethegas,HDPEsheathing,reservoirtanks,anchorage-sealingcapsandmonitoringhardware.Nitrogengaswasselectedduetoitsnon-corrosivepropertiesandeaseofavailability.Anenvironmentofpressurizedpurenitrogenessentiallyeliminatesoxygen,chloridesandmoisture,allpotentiallycorrosiveelements.Aprimarygoalwastocost-effectivelycreateagas-tightsealedsystemthatcompletelyenclosesthestays.Afterinstallationofthestays,theywerepurgedofmoistureandnitrogengasinjectedtopurgetheexistingairfromtheclosedenvironment.Thenitrogenwasthenpressurizedtotwopoundspersquareinc...