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外文翻译--一种对于常规桥远程测量最小垂直方向净空的创新检查方法.doc

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外文翻译--一种对于常规桥远程测量最小垂直方向净空的创新检查方法.doc

英文原文AninnovativemethodforremotemeasurementofminimumverticalunderclearanceinroutinebridgeinspectionB.Riveiroa,D.V.Jaureguib,P.Ariasc,J.Armestoc,R.Jiangda.DepartmentofMaterialsEngineering,AppliedMechanicsandConstruction,SchoolofIndustrialEngineering,UniversityofVigo,C.P.36208,Vigo,Spainb.DepartmentofCivilEngineering,CollegeofEngineering,NewMexicoStateUniversity,LasCruces,NM,USAc.DepartmentofNaturalResourcesandEnvironmentalEngineering,SchoolofMiningEngineering,UniversityofVigo,C.P.36310,Vigo,Spaind.DepartmentofEngineeringTechnologyandSurveyingEngineering,CollegeofEngineering,NewMexicoStateUniversity,LasCruces,NM,USAArticleinfoabstractArticlehistoryAccepted18April2012Availableonline17May2012Thispaperpresentsaninnovativeandlowcostprocedureforthecompleteandaccuratemeasurementofminimumverticalunderclearanceinasafeenvironmentforoperators.Thisproceduredrawsontheprinciplesofterrestrialconvergentphotogrammetrywhichmakespossiblethereconstructionofthebridgecomponentsandsurroundingfeaturesin3Dspace.Usingthemeasured3Dcoordinates,analgorithmwasdevelopedintheMatlabsoftwaretocalculatetheverticalunderclearance.Furthermore,aprocedurebasedon3Dcurvefittingwasdevelopedtoestimatethemathematicalexpressionofthebeamcurve.Theresultingmethodologyissuitableandadvantageousforimplementationinroutinebridgeinspectionbecauseitprovidesamoreextensiveandaccuratemeasurementofverticalunderclearanceundermuchsaferconditions.Inaddition,theestimateofthebeamequationcanbeusednotonlyforclearancemeasurementbutalsoforperiodicmonitoringofthebeamshapeovertime.KeywordsBridgeinspectionCloserangephotogrammetryVerticalunderclearance.1IntroductionItistruethatextensiveknowledgeofthefunctionalandconservationstatesofastructureisneededinordertoproperlyscheduleitsmaintenanceandultimately,ensureitspreservation.Periodicmonitoringofgeometryusuallyplaysakeyroleinthedetectionofstructuralanomalies,andinsomecasessuchasstonearchbridges,canaidinpreventingcollapseduetoproblemswithequilibriumandstability1.Inthecaseofmodernbridgesmainlycomposedofconcreteorsteel,althoughthediagnosisoftheirconditionstateisassessedbasedprimarilyonthephysicalconditionofthestructuralelements,theexternalshapeandgeometryalsoplaysaveryimportantroleintheoverallevaluation.Thepresenceofdeterioration,defects,anddamagese.g.,impactdamagecausedbytruckcollisions,concretespallsordelaminations,fatigueorshearcracks,sectionlossandevidenceofirregularmovementarethemostimportantparametersconsideredduringaroutinebridgeinspection,andmoveadvancedtoolsfortheirdetectionandquantificationneedtobeinvestigated.Bridgeinspectionisakeyfactorinthemaintenanceandpreservationofthecivilinfrastructureofacountry.Manyparametershavetobeperiodicallyevaluatedinordertodeterminethephysicalconditionofthestructure4–5.Inthebridgemanagementprotocoloftransportationagencies,thereusuallyexistsaninitialphasefocusedonroutineinspection,where,bymeansofquickandsimpledocumentation,thefirstdiagnosisofthecurrentstateofthestructureisobtained6–8.Whensomeevidenceofdistressaboutthephysicalconditionorstabilityofthestructureisfoundinthisinitialstepsuchasexcessivebeamsagorsupportsettlement,aspecialinspectionplanshouldbeinitiatedtoperformanindepthevaluationofthebridge.Currently,thereareseveralbasictechniquesavailabletomeasureirregularbridgemovementsuchasplumbbobs,laserlevels,theodolites,andtotalstations.Horizontalandverticalclearancesareimportantgeometricparametersthatmustbemeasuredtoahighlevelofaccuracyduringaroutinebridgeinspection.Theacquisitionofthesedimensionsistraditionallyaccomplishedbymeansofbasiccontacttoolssuchastapemeasuresandrangepolesthatlackmetricaccuracy,andwhichalsorequiretheoperatorstoperformtheclearancemeasurementsunderdangeroustrafficconditions.Fig.1illustratestheuseofarangepoletomeasuretheminimumverticalunderclearancewhichisthedistancefromtheroadwayorrailroadtrackbeneaththebridgetotheundersideofthesuperstructure.Asshowninthefigure,measurementsareusuallytakenatdiscretepointsonthebottomsurfaceofthebeamtosavetimeandalsoduetosafetyconcerns.Furthermore,itisdifficulttokeeptherangepoleperfectlyverticaltoobtainanaccuratemeasurementparticularlyforhigherclearances.Consequently,itispossiblethattheminimumverticalunderclearanceisnotmeasuredaccuratelyatthecorrectlocation.Thereare116itemsofbridgedatausedbytheFHWAtomonitorandmanagetheNationalBridgeInventoryNBIintheUnitedStatesasgivenintheStructureInventoryandAppraisalSIPsheet.Thedataaredividedbetweeninventoryitemsthatpertaintothepermanentconditionsofthebridgeandappraisalitemsthatpertaintotheconditionofthebridgecomponentincomparisontocurrentstandards.IntheSIPsheet,geometricdataareconsideredinventoryitemsunderwhichtheminimumverticalunderclearanceisitem54.Thisparticularitemiscodedwith5digitsthefirstdigitrepresentsthereferencefeaturehighwayorrailroadbeneathstructureandtheremainingfourdigitsrepresenttheminimumverticalunderclearanceinfeetandinches.Underclearanceinformationisusedbypersonnelinvolvedwiththepermittingofoversize/overweightvehiclesandisusedinevaluatingthesufficiencyofabridgetoremaininservicei.e.,sufficiencyrating.Fourseparatefactorsaredeterminedusing19ofthe116itemsreportedintheSIAsheettoarriveatthesufficiencyrating1structuraladequacyandsafety2serviceabilityandfunctionalobsolescence3essentialityforpublicuseand4specialreductions.Horizontalandverticalunderclearancesandthedeckconditionaffectthesecondfactorwhilethesuperstructureandsubstructureconditionsaffectthefirstfactor.Thesufficiencyratingrangesfrom0to100withthelatterpercentagerepresentinganentirelysufficientbridge.Bridgesqualifyforreplacementwhentheratingfallsbelow50andrehabilitationwhentheratingfallsbelow80.Inspiteofthesimplicityandrapidityinusingtraditionalinstruments,thequalityofmetricresultsispoor.Surveyingtechniquesofferbetterqualityresultsintermsofaccuracy,butthesemethodshaveimportantlimitationsforregularuseinrelationtohandlingofequipmentandtheamountofdatacollected.Terrestrialphotogrammetryandlaserscanningaretwogeomatictechniqueswhichhavesignificantlyevolved,beingmoreandmoreusedindiversefieldsincludingarchitecture9,10civilengineering11–14industry15,16andarchaeology17,18.Manyinvestigationsshowthepotentialofthesenewtechnologiesinthefieldofbridgeengineering19.Fromthecapturedprecise3Dgeometryofbridges,forexample,animprovedassessmentofthestructurecanbemade20.Laserscanningisgainingpopularityduetoitssimplicityinusageandspeedofacquisition21.Afewstudiesofdamagedetectioninconcretebridgesusingterrestriallaserscannerdatacanbefoundin22–24.Similartotraditionalsurveyingequipment,laserscanningpresentsimportantlimitationsforroutineinspectionworkincludingcostofequipment,necessityfortrainedoperators,andamountofdatastoredduringthebridgesurvey.Consequently,lowcosttechnologiescapableofcollectingmeaningfulandaccuratemetricdatawithouttheneedforoverlycomplicatedequipmentoperationandextensivedataprocessingareneeded.Closerangephotogrammetryhasseveralstrengthsthatmakeitasuitablemethodformeasuringbridgefeaturesduringaroutineinspectionsuchasitutilizeslowcostequipment,itisrelativelyeasytouse,anditprovideshighmetricprecision.Anextensivereviewoftheapplicationofthistechniqueinbridgeengineeringcanbefoundin19.GonzalezAguileraandGómezLahoz25presentanovelphotogrammetricsystembasedonasingleimageforobtainingtheoverallgeometryofbridgesbymeansofdimensionalanalysis.OtherstudiesrelatedtobridgemonitoringbasedonphotogrammetricmethodsincludedthoseperformedbyChangandJi26andHangetal.27.Beforenewtechnologiesareincludedintheprotocolsformetricdocumentation,theymustfirstbevalidated.Inthiscontext,methodologiesofsurveyingneedtobeadaptedtoovercometheexistingdifficultiesinroutinebridgeinspection.Thispaperpresentsaninnovativeandlowcostprocedureforthecompleteandaccuratemeasurementofminimumverticalunderclearanceinasafeenvironmentforoperators.Thisproceduredrawsontheprinciplesofterrestrialconvergentphotogrammetrywhichmakespossiblethereconstructionofthebridgecomponentsandsurroundingfeaturesin3Dspace.Usingthemeasured3Dcoordinates,analgorithmwasdevelopedintheMatlabsoftwaretocalculatetheverticalunderclearance.Furthermore,aprocedurebasedon3Dcurvefittingwasdevelopedtoestimatethemathematicalexpressionofthebeamcurve.Theresultingmethodologyissuitableandadvantageousforimplementationinroutinebridgeinspectionbecauseitprovidesamoreextensiveandaccuratemeasurementofverticalunderclearanceundermuchsaferconditions.Inaddition,theestimateofthebeamequationcanbeusednotonlyforclearancemeasurementbutalsoforperiodicmonitoringofthebeamshapeovertime.2Theoreticalbackgrounds2.1PhotogrammetricprocessCloserangephotogrammetryisanondestructivegeomatictechniquewhichallowsthe3Dshapeofobjectstobereconstructedfromphotographicimages.Theconversionfrom2Dinformationofimagesto3Dmodelsisachievedbymeansofthephotogrammetricprocess.Twomainstepscontributetothisprocessinnerorientationandexternalorientation.Theinnerorientationreconstructstheinternalgeometryoftheimagingsystem,whichdefinestheperspectivesystem,bymeansofthecameracalibrationprocess.Themetricparametersobtainedfromthecameracalibrationincludethe3Dpositionoftheperspectivecentreintheimagespacefocallengthandprincipalpointonthesensor,sensordimensions,andlensdistortions.Thelensdistortionsaresourcesoferrorsduringtheimagerecordingandmustbecompensatedfortoobtainthemostaccuratereconstructionofthe3Dmodel.Thesymmetricradialdistortionsignificantlyinfluencesthephotogrammetricreconstructionasshownin28,29.Therearetwocommonformulationsforradialdistortionbalancedandunbalancedmodels.Althoughthesemodelscanbemathematicallyequivalent,thebalancedmodelresultsinsmallerapparentdistortionssoiscommonlyusedbycameraandlensmanufacturers30–32.Theexternalorientationlocatestherelativepositionofeachcamerausedinthe3Dreconstructionprocessatthetimeimagesweretaken.Hence,ifthepositionofonecameraisknown,therelativeexternalorientationisdoneusingthepositionsX,Y,Zandorientationsω,φ,κoftheothercameras.Foragivenpointinanobjectspace,thecoplanarityconditionrequiresthatthepointspositionintwooverlappedimagesandthecamerasperspectivecentrearesituatedinthesameplane.AsshownbyKraussin33,therelativeorientationofimagesisachievedwhentheimagecoordinatesofFig.1.Fig.1.MeasurementofminimumverticalunderclearanceduringaroutinebridgeinspectionMeasurementofminimumverticalunderclearanceduringaroutinebridge.Inspectionfivepointsareknown.Theexternalorientationiscompletedwhenthemodelisscaledandplacedin

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