毕业设计论文-外文文献翻译-桥梁专业-翻译

PAGEPAGE24附录一英文翻译原文AUTOMATICDEFLECTIONANDTEMPERATUREMONITORINGOFABALANCEDCANTILEVERCONCRETEBRIDGEbyOlivierBURDET,Ph.D.SwissFederalInstituteofTechnology,Lausanne,SwitzerlandInstituteofReinforcedandPrestressedConcreteSUMMARYThereisaneedforreliablemonitoringsystemstofollowtheevolutionofthebehaviorofstructuresovertime.Deflectionsandrotationsarevaluesthatreflecttheoverallstructurebehavior.Thispaperpresentsaninnovativeapproachtothemeasurementoflong-termdeformationsofbridgesbyuseofinclinometers.Highprecisionelectronicinclinometerscanbeusedtofolloweffectivelylong-termrotationswithoutdisruptionofthetraffic.Inadditiontotheiraccuracy,theseinstrumentshaveproventobesufficientlystableovertimeandreliableforfieldconditions.TheMentuebridgesaretwin565mlongbox-girderpost-tensionedconcretehighwaybridgesunderconstructioninSwitzerland.Thebridgesarebuiltbythebalancedcantilevermethodoveradeepvalley.Thepiersare100mhighandthemainspanis150m.Acentralizeddataacquisitionsystemwasinstalledinonebridgeduringitsconstructionin1997.Everyminute,thesystemrecordstherotationandtemperatureatanumberofmeasuringpoints.Thesimultaneousmeasurementofrotationsandconcretetemperatureatseverallocationsgivesaclearideaofthemovementsinducedbythermalconditions.Thesystemwillbeusedincombinationwithahydrostaticlevelingsetuptofollowthelong-termbehaviorofthebridge.Preliminaryresultsshowthatthesystemperformsreliablyandthattheaccuracyofthesensorsisexcellent.Comparisonoftheevolutionofrotationsandtemperatureindicatethatthestructurerespondstochangesinairtemperatureratherquickly.BACKGROUNDAllovertheworld,thenumberofstructuresinservicekeepsincreasing.Withthedevelopmentoftrafficandtheincreaseddependenceonreliabletransportation,itisbecomingmoreandmorenecessarytoforeseeandanticipatethedeteriorationofstructures.Inparticular,forstructuresthatarepartofmajortransportationsystems,rehabilitationworksneedtobecarefullyplannedinordertominimizedisruptionsoftraffic.Automaticmonitoringofstructuresisthusrapidlydeveloping.Long-termmonitoringofbridgesisanimportantpartofthisoverallefforttoattempttominimizeboththeimpactandthecostofmaintenanceandrehabilitationworkofmajorstructures.Byknowingtherateofdeteriorationofagivenstructure,theengineerisabletoanticipateandadequatelydefinethetimingofrequiredinterventions.Conversely,interventionscanbedelayeduntiltheconditionofthestructurerequiresthem,withoutreducingtheoverallsafetyofthestructure.Thepaperpresentsaninnovativeapproachtothemeasurementoflong-termbridgedeformations.Theuseofhighprecisioninclinometerspermitsaneffective,accurateandunobtrusivefollowingofthelong-termrotations.Themeasurementscanbeperformedundertrafficconditions.Simultaneousmeasurementofthetemperatureatseverallocationsgivesaclearideaofthemovementsinducedbythermalconditionsandthoseinducedbycreepandshrinkage.ThesystempresentedisoperationalsinceAugust1997intheMentuebridge,currentlyunderconstructioninSwitzerland.Thestructurehasamainspanof150mandpiers100mhigh.2.LONG-TERMMONITORINGOFBRIDGESAspartofitsresearchandserviceactivitieswithintheSwissFederalInstituteofTechnologyinLausanne(EPFL),IBAP-ReinforcedandPrestressedConcretehasbeeninvolvedinthemonitoringoflong-timedeformationsofbridgesandotherstructuresforovertwenty-fiveyears[1,2,3,4].Inthepast,IBAPhasdevelopedasystemforthemeasurementoflong-termdeformationsusinghydrostaticleveling[5,6].ThissystemhasbeeninsuccessfulserviceintenbridgesinSwitzerlandforapproximatelytenyears[5,7].Thesystemisrobust,reliableandsufficientlyaccurate,butitrequireshumaninterventionforeachmeasurement,andisnotwellsuitedforautomaticdataacquisition.Oneadditionaldisadvantageofthissystemisthatitisonlyeasilyapplicabletoboxgirderbridgeswithanaccessiblebox.Occasionalcontinuousmeasurementsoverperiodsof24hourshaveshownthattheamplitudeofdailymovementsissignificant,usuallyamountingtoseveralmillimetersoveracoupleofhours.Thisisexemplifiedinfigure1,wheremeasurementsofthetwinLutrivebridges,takenoveraperiodofseveralyearsbeforeandaftertheywerestrengthenedbypost-tensioning,areshownalongwithmeasurementsperformedoveraperiodof24hours.Thescatterobservedinthedataisprimarilycausedbythermaleffectsonthebridges.Inthecaseofthesebox-girderbridgesbuiltbythebalancedcantilevermethod,withamainspanof143.5m,theamplitudeofdeformationsonasunnydayisofthesameorderofmagnitudethanthelongtermdeformationoverseveralyears.Instantaneousmeasurements,asthosemadebyhydrostaticleveling,arenotnecessarilyrepresentativeofthemeanpositionofthebridge.Thisoccursbecausethepositionofthebridgeatthetimeofthemeasurementisinfluencedbythetemperaturehistoryoverthepastseveralhoursanddays.Evenifeverycarewastakentoperformthemeasurementsearlyinthemorningandatthesameperiodeveryyear,ittookarelativelylongtimebeforeitwasrealizedthattheretrofitperformedontheLutrivebridgesin1988byadditionalpost-tensioning[3,7,11]hadnothadthesameeffectonbothofthem.Figure1:Long-termdeflectionsoftheLutrivebridges,comparedtodeflectionsmeasuredina24-hourperiodAutomaticdataacquisition,allowingfrequentmeasurementstobeperformedatanacceptablecost,isthushighlydesirable.Astudyofpossiblesolutionsincludinglaser-basedleveling,fiberopticssensorsandGPS-positioningwasperformed,withtheconclusionthat,providedthattheirlong-termstabilitycanbedemonstrated,currenttypesofelectronicinclinometersaresuitableforautomaticmeasurementsofrotationsinexistingbridges[8].3.MENTUEBRIDGESTheMentuebridgesaretwinbox-girderbridgesthatwillcarrythefutureA1motorwayfromLausannetoBern.Eachbridge,similarindesign,hasanoveralllengthofapproximately565m,andawidthof13.46m,designedtocarrytwolanesoftrafficandanemergencylane.Thebridgescrossadeepvalleywithsteepsides(fig.2).Thebalancedcantileverdesignresultsfromabridgecompetition.The100mhighconcretepierswerebuiltusingclimbingformwork,afterwhichtheconstructionofthebalancedcantileverstarted(fig.3).4.INCLINOMETERSStartingin1995,IBAPinitiatedaresearchprojectwiththegoalofinvestigatingthefeasibilityofameasurementsystemusinginclinometers.Preliminaryresultsindicatedthatinclinometersofferseveraladvantagesfortheautomaticmonitoringofstructures.Table1summarizesthemainpropertiesoftheinclinometersselectedforthisstudy.Oneinterestingpropertyofmeasuringastructure’srotations,isthat,foragivenratioofmaximumdeflectiontospanlength,themaximumrotationisessentiallyindependentfromitsstaticsystem[8].Sincemaximalallowablevaluesofabout1/1,000forlong-termdeflectionsunderpermanentloadsaregenerallyacceptedvaluesworldwide,developmentsmadeforbox-girderbridgeswithlongspans,asisthecaseforthisresearch,areapplicabletootherbridges,forinstancebridgeswithshorterspansandothertypesofcross-sections.Thisissignificantbecauseoftheneedtomonitorsmallerspanswhichconstitutethemajorityofallbridges.TheselectedinclinometersareoftypeWylerZerotronic±1°[9].Theiraccuracyis1microradian(μrad),whichcorrespondstoarotationofonemillimeterperkilometer,averysmallvalue.Foranintermediatespanofacontinuousbeamwithaconstantdepth,amid-spandeflectionof1/20,000wouldinduceamaximumrotationofabout150μrad,or0.15milliradians(mrad).Onepotentialproblemwithelectronicinstrumentsisthattheirmeasurementsmaydriftovertime.Toquantifyandcontrolthisproblem,amechanicaldevicewasdesignedallowingtheinclinometerstobepreciselyrotatedof180°inanhorizontalplane(fig.4).Thedriftofeachinclinometercanbeverysimplyobtainedbycomparingthevaluesobtainedintheinitialandrotatedpositionwithpreviouslyobtainedvalues.Sofar,ithasbeenobservedthatthetypeofinclinometerusedinthisprojectisnotverysensitivetodrifting.5.INSTRUMENTATIONOFTHEMENTUEBRIDGESBecauseanumberofbridgesbuiltbythebalancedcantilevermethodhaveshownanunsatisfactorybehaviorinservice[2,7,10],itwasdecidedtocarefullymonitortheevolutionofthedeformationsoftheMentuebridges.Thesebridgesweredesignedtakingintoconsiderationrecentrecommendationsforthechoiceoftheamountofposttensioning[7,10,13].Monitoringstartingduringtheconstructionin1997andwillbepursuedafterthebridgesareopenedtotrafficin2001.Deflectionmonitoringincludestopographiclevelingbythehighwayauthorities,anhydrostaticlevelingsystemovertheentirelengthofbothbridgesandanetworkofinclinometersinthemainspanoftheNorthbridge.Datacollectioniscoordinatedbytheengineerofrecord,tofacilitatecomparisonofmeasuredvalues.Theinformationgainedfromtheseobservationswillbeusedtofurtherenhancethedesigncriteriaforthattypeofbridge,especiallywithregardtotheamountofpost-tensioning[7,10,11,12,13].Theautomaticmonitoringsystemisdrivenbyadataacquisitionprogramthatgathersandstoresthedata.Thissystemisabletocontrolvarioustypesofsensorssimultaneously,atthepresenttimeinclinometersandthermalsensors.Thecomputerprogramdrivingalltheinstrumentationoffersaflexibleframework,allowingthelateradditionofnewsensorsordataacquisitionsystems.TheuseofthedevelopmentenvironmentLabView[14]allowedtoleveragethelargeuserbaseinthefieldoflaboratoryinstrumentationanddataanalysis.Thedataacquisitionsystemrunsonarathermodestcomputer,withanIntel486/66Mhzprocessor,16MBofmemoryanda500MBharddisk,runningWindowsNT.Allsensordataaregatheredonceperminuteandstoredincompressedformontheharddisk.Thesystemislocatedinthebox-girderontopofpier3(fig.5).Itcanwithstandsevereweatherconditionsandwillrestartitselfautomaticallyafterapoweroutage,whichhappenedfrequentlyduringconstruction.6.SENSORSFigure5(a)showsthelocationoftheinclinometersinthemainspanoftheNorthbridge.Thesensorsareplacedattheaxisofthesupports(①and⑤),at1/4and3/4(③and④)ofthespanandat1/8ofthespanfor②.Inthecrosssection,thesensorsarelocatedontheNorthweb,ataheightcorrespondingtothecenterofgravityofthesection(fig.5a).ThesensorsareallconnectedbyasingleRS-485cabletothecentraldataacquisitionsystemlocatedinthevicinityofinclinometer①.Monitoringofthebridgestartedalreadyduringitsconstruction.Inclinometers①,②and③wereinstalledbeforethespanwascompleted.Theresultingmeasurementweredifficulttointerpret,however,becauseofthewidevariationsofanglesinducedbythevariousstagesofthisparticularThedeflectedshapewillbedeterminedbyintegratingthemeasuredrotationsalongthelengthofthebridge(fig.5b).Althoughthisintegrationisinprinciplestraightforward,ithasbeenshown[8,16]thatthetypeofloadingandpossiblemeasurementerrorsneedtobecarefullytakenintoaccount.Thermalsensorswereembeddedinconcretesothattemperatureeffectscouldbetakenintoaccountfortheadjustmentofthegeometryoftheformworkforsubsequentcasts.Figure6showsthelayoutofthermalsensorsinthemainspan.Themeasurementsectionsarelocatedatthesamesectionsthantheinclinometers(fig.5).Allsensorswereplacedintheformworkbeforeconcretingandwereoperationalassoonastheformworkwasremoved,whichwasrequiredfortheneedsoftheconstruction.Ineachsection,sevenoftheninethermalsensor(indicatedinsolidblackinfig.6)arenowautomaticallymeasuredbythecentraldataacquisitionsystem.7.RESULTSFigure7showstheresultsofinclinometrymeasurementsperformedfromtheendofSeptembertothethirdweekofNovember1997.Allinclinometersperformedwellduringthatperiod.Occasionalinterruptionsofmeasurement,asobservedforexampleinearlyOctoberareduetointerruptionofpowertothesystemduringconstructionoperations.Theoverallsymmetryofresultsfrominclinometersseemtoindicatethattheinstrumentsdriftisnotsignificantforthattimeperiod.Themaximumamplitudeofbridgedeflectionduringtheobservedperiod,estimatedonthebasisoftheinclinometersresults,isaround40mm.Moreaccuratevalueswillbecomputedwhenthemethodofdeterminationofdeflectionswillhavebeenfurthercalibratedwithothermeasurements.Severalperiodsofincrease,respectivelydecrease,ofdeflectionsoverseveraldayscanbeobservedinthegraph.Thisfurtherillustratestheneedforcontinuousdeformationmonitoringtoaccountforsucheffects.Termsofconstruction,andincludedthefollowingoperations:thefinalconcretepoursinthatspan,horizontaljackingofthebridgetocompensatesomepiereccentricities,aswellasthestressingofthecontinuitypost-tensioning,andthede-tensioningoftheguycables(fig.3).Asaconsequence,theinterpretationofthesemeasurementsisquitedifficult.Itisexpectedthatfurthermeasurements,madeafterthecompletionofthebridge,willbesimplertointerpret.Figure8showsadetailofthemeasurementsmadeinNovember,whilefigure.9showstemperaturemeasurementsatthetopandbottomofthesectionatmid-spanmadeduringthatsameperiod.Itisclearthatthemeasureddeflectionscorrespondtochangesinthetemperature.Thetemperatureatthebottomofthesectionfollowscloselyvariationsoftheairtemperature(measuredintheshadenearthenorthwebofthegirder).Ontheotherhand,thetemperatureatthetopofthecrosssectionislesssubjecttorapidvariations.Thismaybeduetothehighelevationofthebridgeaboveground,andalsotothefactthat,duringthemeasuringperiod,therewaslittledirectsunshineonthedeck.Thetemperaturegradientbetweentopandbottomofthecrosssectionhasadirectrelationshipwithshort-termvariations.Itdoesnot,however,appeartoberelatedtothegeneraltendencytodecreaseinrotationsobservedinfig.8.8.FUTUREDEVELOPMENTSFuturedevelopmentswillincludealgorithmstoreconstructdeflectionsfrommeasuredrotations.Toenhancetheaccuracyofthereconstructionofdeflections,a3Dfiniteelementmodeloftheentirestructureisinpreparation[15].Thismodelwillbeusedtoidentifytheinfluenceonrotationsofvariousphenomena,suchascreepofthepiersandgirder,differentialsettlements,horizontalandverticaltemperaturegradientsortrafficloads.MuchworkwillbedevotedtotheinterpretationofthedatagatheredintheMentuebridge.Thefinalpartoftheresearchprojectworkwillfocusontwoaspects:understandingtheverycomplexbehaviorofthestructure,anddeterminingthemostimportantparameters,toallowasimpleandeffectivemonitoringofthebridgesdeflections.Finally,theresearchreportwillproposeguidelinesfordeterminationofdeflectionsfrommeasuredrotationsandpracticalrecommendationsfortheimplementationofmeasurementsystemsusinginclinometers.Itisexpectedthatwithinthecomingyearnewsiteswillbeequippedwithinclinometers.Experiencesmadebyusinginclinometerstomeasuredeflectionsduringloadingtests[16,17]haveshownthatthemethodisveryflexibleandcompetitivewithotherhigh-techmethods.Asanextensiontothecurrentresearchproject,aninnovativesystemforthemeasurementofbridgejointmovementisbeingdeveloped.Thissystemintegrateseasilywiththeexistingmonitoringsystem,becauseitalsousesinclinometers,althoughfromaslightlydifferenttype.9.CONCLUSIONSAninnovativemeasurementsystemfordeformationsofstructuresusinghighprecisioninclinometershasbeendeveloped.Thissystemcombinesahighaccuracywitharelativelysimpleimplementation.Preliminaryresultsareveryencouragingandindicatethattheuseofinclinometerstomonitorbridgedeformationsisafeasibleandoffersadvantages.Thesystemisreliable,doesnotobstructconstructionworkortrafficandisveryeasilyinstalled.Simultaneoustemperaturemeasurementshaveconfirmedtheimportanceoftemperaturevariationsonthebehaviorofstructuralconcretebridges.10.REFERENCES[1]ANDREYD.,Maintenancedesouvragesd’art:méthodologiedesurveillance,PhDDissertationNr679,EPFL,Lausanne,Switzerland,1987.[2]BURDETO.,LoadTestingandMonitoringofSwissBridges,CEBInformationBulletinNr219,SafetyandPerformanceConcepts,Lausanne,Switzerland,1993.[3]BURDETO.,Critèrespourlechoixdelaquantitédeprécontraintedécoulantdel.observationdepontsexistants,CUST-COS96,Clermont-Ferrand,France,1996.[4]HASSANM.,BURDETO.,FAVRER.,CombinationofUltrasonicMeasurementsandLoadTestsinBridgeEvaluation,5thInternationalConferenceonStructuralFaultsandRepair,Edinburgh,Scotland,UK,1993.[5]FAVRER.,CHARIFH.,MARKEYI.,Observationàlongtermedeladéformationdesponts,MandatdeRecherchedel’OFR86/88,FinalReport,EPFL,Lausanne,Switzerland,1990.[6]FAVRER.,MARKEYI.,Long-termMonitoringofBridgeDeformation,NATOResearchWorkshop,BridgeEvaluation,RepairandRehabilitation,NATOASIseriesE:vol.187,pp.85-100,Baltimore,USA,1990.[7]FAVRER.,BURDETO.etal.,Enseignementstirésd’essaisdechargeetd’observationsàlongtermepourl’évaluationdespontsetlechoixdelaprécontrainte,OFRReport,83/90,Zürich,Switzerland,1995.[8]DAVERIOR.,Mesuresdesdéformationsdespontsparunsystèmed’inclinométrie,RapportdemaîtriseEPFL-IBAP,Lausanne,Switzerland,1995.[9]WYLERAG.,TechnicalspecificationsforZerotronicInclinometers,Winterthur,Switzerland,1996.[10]FAVRER.,MARKEYI.,GeneralizationoftheLoadBalancingMethod,12thFIPCongress,PrestressedConcreteinSwitzerland,pp.32-37,Washington,USA,1994.[11]FAVRER.,BURDETO.,CHARIFH.,Critèrespourlechoixd’uneprécontrainte:applicationaucasd’unrenforcement,"ColloqueInternationalGestiondesOuvragesd’Art:QuelleStratégiepourMainteniretAdapterlePatrimoine,pp.197-208,Paris,France,1994.[12]FAVRER.,BURDETO.,WahleinergeeignetenVorspannung,Beton-undStahlbetonbau,Beton-undStahlbetonbau,92/3,67,Germany,1997.[13]FAVRER.,BURDETO.,Choixd’unequantitéappropriéedeprécontrainte,SIAD0129,Zürich,Switzerland,1996.[14]NATIONALINSTRUMENTS,LabViewUser.sManual,Austin,USA,1996.[15]BOUBERGUIGA.,ROSSIERS.,FAVRER.etal,Calculnonlinéairedubétonarméetprécontraint,RevueFrançaisduGénieCivil,vol.1n°3,Hermes,Paris,France,1997.[16]FESTE.,Systèmedemesureparinclinométrie:développementd’unalgorithmedecalculdesflèches,MémoiredemaîtrisedeDEA,Lausanne/Paris,Switzerland/France,1997.[17]PERREGAUXN.etal.,VerticalDisplacementofBridgesusingtheSOFOSystem:aFiberOpticMonitoringMethodforStructures,12thASCEEngineeringMechanicsConference,SanDiego,USA,tobepublished,1998.译文平衡悬臂施工混凝土桥挠度和温度的自动监测

作者OlivierBURDET博士

瑞士联邦理工学院，洛桑，瑞士

钢筋和预应力混凝土研究所

概要：我们想要跟踪结构行为随时间的演化，需要一种可靠的监测系统。挠度和旋转两个参数反映了结构的整体行为。本文提出了一种测量桥梁长期变形的创新方法，即，使用倾角仪。高精密电子倾角仪可以有效地追踪桥梁的长期旋转而不需要中断交通。除了准确，这些仪器已被证明随着时间的推移是足够稳定，野外条下也非常可靠。

Mentue桥，长565m，双箱双室梁，后张法预应力混凝土公路桥梁，修建于瑞士。该桥由平衡悬臂法修建于一条深谷之上。墩高100m，主跨为150m。一个集中的数据采集系统于1997年修建该桥时安装在一梁上。每一分钟，系统记录了很多测量点的旋转量和温度值。在多个地点同时测量出的旋转量和混凝土温度给出了热条件引起的变动的初步结果表明该系统运行可靠，并且传感器的准确性非常优秀。

对旋转和温度的演变比较表明，结构对气温变化的反应相当快。

1.背景

遍布世界，服役结构的数量在不断增加。随着交通的发展，我们日益依赖于可靠的交通运输，越来越有必要去预见和预测结构的恶化。特别是，对于主要运输系统的那部分结构，修复工程需要认真规划，以尽量减少交通中断。结构自动监测仪器从而迅速发展。

长期桥梁监测是这一全面努力的重要组成部分，以尝试减少对主要结构的影响和维修工程的费用。通过了解某一特定结构的恶化速度，工程师能够预见并充分界定所要求的处理措施的时机。相反，不降低结构的整体安全性，处理可以推迟到结构需要相应措施的时候。

本文提出了一种检测桥梁长期变形的创新方法。高精度倾角仪的使用允许我们可以对长期旋转进行有效、准确和无障碍跟踪。该测量设备可以在正常交通状况下运行。同一时间测量的、多个地点的温度给出了一个由热、蠕变和收缩导致的变形的清晰概念。提出该系统的可行性是1997年8月开始运营的修建于瑞士的Mentue桥。该桥主跨150m，墩高100m。

2.桥梁的长期监测

作为其研究和瑞士联邦理工学院（洛桑联邦理工学院）服务活动的一部分，该桥梁和其他结构涉及到的钢筋混凝土和预应力混凝土长期变形的监测已超过二十五年[1，2，3，4]。在过去，IBAP已经制定了一个长期变形测量的水准测量系统[5，6]。该系统已成功的服务于瑞士的十座桥梁约十年[5,7]。该系统强大，可靠和足够准确，但它要求每次测量要人为操作，并没有很好地适合于数据自动采集。该系统另外的一个缺点是，它只是较容易适用于可接触到的箱形梁桥。

偶尔超过24小时的连续测量表明，它日常变形幅度很大，通常一两个小时内几个毫米。这体现在图1中，那里的双箱双室梁Lutrive桥在他们被后张之前和尔后超过数年的测量显示了24小时内的测量结果。观察到的数据散射主要是由桥梁的热效应造成的。用平衡悬臂法建造、1435m主跨的箱形梁，在一个阳光明媚的日子变形幅度是与过去数年的长期变形属于同一量级瞬时测量，如水准测量得出的结果，不一定代表了该桥的平均位置。这是因为在桥梁测量时的位置是受过去几个小时、几天气温的温度历史影响。即使周全的考虑影响监测测量结果的因素并且在每年的同一时期进行测量，也需要相对较长的时间，我们才能弄清楚Lutrive桥在1988年进行改造时额外桥梁后张[3,7,11]有没有产生与两者相同的影响。

图1：Lutrive桥的长期挠度，与24小时内挠度自动采集的数据，使得我们可以在一个可接受的成本上进行方便地测量，因此非常可取。一个可能的解决方案研究，进行了包括基于激光水准，光纤传感器和GPS定位，得出的结论是，只要可以确保它们的长期稳定性，当前类型的电子倾角仪，都适合于自动测量现有桥梁的旋转量[8]。3.MENTUE道桥Mentue桥是单箱双室箱梁桥，将衔接从洛桑到伯尔尼的未来A1高速公路。每片梁设计类似，拥有约565m的,整体长度和13.46m的宽度，设计承载两行车线和一个应急车道。桥梁跨越一两侧有陡峭山坡的深谷（图2）。平衡悬臂桥梁施工设计是与另一桥梁方案比选的结果。100m高的混凝土桥墩用爬模施工方法完成后，平衡悬臂施工启动（图3）4.倾角仪从1995年开始，IBAP发起了一个研究项目，目的是调查利用倾角仪的测量系统的可行性。初步结果表明，倾角仪为结构提供自动监测提供了些许优点。表1总结了本研究选择的倾角仪的主要特性。

衡量结构转动的有趣属性是，对于一个给定的最大挠度跨度比，最大旋转基本上是独立于它的静态系统[8]。由于在永久荷载下，最大允许值约1/1000的长期挠度已经被全世界普遍接受，就像这项研究中大跨度箱梁桥取得发展，同样适用于其他桥梁，例如跨度较短桥梁和其他类型跨度区域。这是很重要的，因为需要检测那些小跨度梁，他们构成所有桥梁的大部分结构。

表1倾角仪的主要特性特性描述绝对的测量相对于最初的位置，这种测量是绝对的。以防这种仪器的失败，其他仪器提供的信息仍然是可以利用的。数据采集系统可容易联接倾角仪是电子仪器，它所产生的电子信号可以被标准的数据采集系统很容易获得。这项工程所使用的倾角仪包括一种工业网状界面（RS485），其可以大大减少缆索的数量。检测原理可以适用于各种桥梁本质上，转动的幅度是与静定结构或桥梁跨越的区域相互独立的。因为仪器的可靠性，倾角仪可以被安置在可以伸手触及的地方，因此可以适应所有类型的跨越区域。高精度倾角仪的高精度使得极小变形的测量成为可能，比如那些只发生在几分钟之内的的变形。安装和操作简单倾角仪是非常精巧的仪器，安装只须很小的空间。我们挑选的倾角仪包括温度自动补偿。传感器可以很容易安置并且能重复利用。成本尽管相对很高，与同类检测系统相比，倾角仪很具有竞争力，并且安装费相当低。选定的倾角仪类型：伟伦Zerotronic±1°[9]。其准确度为1microradian（μrad），相当于一毫米每公里，是一个非常小的旋转值。对于一个通常高度连续梁的中跨，1/20000的跨中挠度，将导致最大约150μrad的旋转，或0.15毫弧度（mrad）。

电子仪器潜在的一个问题是他们的测量结果可能随时间漂移。为量化和控制这个问题，设计了一种机械装置，允许倾角为180°旋转正是在一水平面上（图4）。每个倾角仪的漂移可以通过比较获得的初始值和旋转位置与以前获得值简单地获得。到目前为止，我们观察到工程中使用的那种倾角仪的类型对漂流不是很敏感。5.曼图桥的测试设备一些采用平衡悬臂施工的桥梁，在实际使用中的状态并不理想/r