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1、AUTOMATICDEFLECTIONANDTEMPERATUREMONITORINGOFABALANCEDCANTILEVERCONCRETEBRIDGEbyOlivierBURDET,Ph.D.SwissFederalInstituteofTechnology,Lausanne,SwitzerlandInstituteofReinforcedandPrestressedConcreteSUMMARYThereisaneedforreliablemonitoringsystemstofollowtheevolution

2、ofthebehaviorofstructuresovertime.Deflectionsandrotationsarevaluesthatreflecttheoverallstructurebehavior.Thispaperpresentsaninnovativeapproachtothemeasurementoflong-termdeformationsofbridgesbyuseofinclinometers.Highprecisionelectronicinclinometerscanbeusedtofollo

3、weffectivelylong-termrotationswithoutdisruptionofthetraffic.Inadditiontotheiraccuracy,theseinstrumentshaveproventobesufficientlystableovertimeandreliableforfieldconditions.TheMentuebridgesaretwin565mlongbox-girderpost-tensionedconcretehighwaybridgesunderconstruct

4、ioninSwitzerland.Thebridgesarebuiltbythebalancedcantilevermethodoveradeepvalley.Thepiersare100mhighandthemainspanis150m.Acentralizeddataacquisitionsystemwasinstalledinonebridgeduringitsconstructionin1997.Everyminute,thesystemrecordstherotationandtemperatureatanum

5、berofmeasuringpoints.Thesimultaneousmeasurementofrotationsandconcretetemperatureatseverallocationsgivesaclearideaofthemovementsinducedbythermalconditions.Thesystemwillbeusedincombinationwithahydrostaticlevelingsetuptofollowthelong-termbehaviorofthebridge.Prelimin

6、aryresultsshowthatthesystemperformsreliablyandthattheaccuracyofthesensorsisexcellent.Comparisonoftheevolutionofrotationsandtemperatureindicatethatthestructurerespondstochangesinairtemperatureratherquickly.1.BACKGROUNDAllovertheworld,thenumberofstructuresinservice

7、keepsincreasing.Withthedevelopmentoftrafficandtheincreaseddependenceonreliabletransportation,itisbecomingmoreandmorenecessarytoforeseeandanticipatethedeteriorationofstructures.Inparticular,forstructuresthatarepartofmajortransportationsystems,rehabilitationworksne

8、edtobecarefullyplannedinordertominimizedisruptionsoftraffic.Automaticmonitoringofstructuresisthusrapidlydeveloping.Long-termmonitoringofbridgesisanimportantpar