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practice.Forexample,becausebridges,aswellasmostcivilengineering
structures,arelargeinsize,andhavequitelownaturalfrequenciesandvibration
levels,atlowamplitudes,thedynamicresponsesofbridgestructureare
substantiallyaffectedbythenonstructuralcomponents,unforeseen
environmentalconditions,andchangesinthesecomponentscaneasilytobe
confusedwithstructuraldamage.Allthesegivethedamageassessmentof
complexstructuressuchasbridgesastillchallengingtaskforbridgeengineers.
Thispaperfirstlypresentsthedefinitionofstructuralhealthmonitoringsystem
anditscomponents.Then,thefocusofthediscussionisplacedonthefollowing
sections:
①thelaboratoryandfieldtestingresearchonthedamage
assessment;
②analyticaldevelopmentsofdamagedetectionmethods,including
(a)signatureanalysisandpatternrecognitionapproaches,(b)modelupdating
andsystemidentificationapproaches,(c)neuralnetworksapproaches;
and③sensorsandtheiroptimumplacements.Thepredominanceand
shortcomingsofeachmethodarecomparedandanalyzed.Recentexamplesof
implementationofstructuralhealthmonitoringanddamageidentificationare
summarizedinthispaper.Thekeyproblemofbridgehealthmonitoringis
damageautomaticdetectionanddiagnosis,anditisthemostdifficultproblem.
Lastly,researchanddevelopmentneedsareaddressed.
1Introduction
Duetoawidevarietyofunforeseenconditionsandcircumstance,itwill
neverbepossibleorpracticaltodesignandbuildastructurethathasazero
percentprobabilityoffailure.Structuralaging,environmentalconditions,and
reuseareexamplesofcircumstancesthatcouldaffectthereliabilityandthelife
专业资料word
ofastructure.Thereareneedsofperiodicinspectionstodetectdeterioration
resultingfromnormaloperationandenvironmentalattackorinspections
followingextremeevents,suchasstrong-motionearthquakesorhurricanes.To
quantifythesesystemperformancemeasuresrequiressomemeanstomonitor
andevaluatetheintegrityofcivilstructureswhileinservice.SincetheAloha
Boeing737accidentthatoccurredonApril28,1988,suchinteresthasfostered
researchintheareasofstructuralhealthmonitoringandnon-destructive
damagedetectioninrecentyears.
AccordingtoHousner,etal.(1997),structuralhealthmonitoringisdefined
as“theuseofin-situ,non-destructivesensingandanalysisofstructural
characteristics,includingthestructuralresponse,fordetectingchangesthat
mayindicatedamageordegradation”[1].Thisdefinitionalsoidentifiesthe
weakness.WhileresearchershaveattemptedtheintegrationofNDEwith
healthmonitoring,thefocushasbeenondatacollection,notevaluation.What
isneededisanefficientmethodtocollectdatafromastructurein-serviceand
processthedatatoevaluatekeyperformancemeasures,suchasserviceability,
reliability,anddurability.So,thedefinitionbyHousner,etal.(1997)shouldbe
modifiedandthestructuralhealthmonitoringmaybedefinedas“theuse
ofin-situ,nondestructivesensingandanalysisofstructuralcharacteristics,
includingthestructuralresponse,forthepurposeofidentifyingifdamagehas
occurred,determiningthelocationofdamage,estimatingtheseverityof
damageandevaluatingtheconsequencesofdamageonthestructures”(Fig.1).
Ingeneral,astructuralhealthmonitoringsystemhasthepotentialtoprovide
bothdamagedetectionandconditionassessmentofastructure.
Assessingthestructuralconditionwithoutremovingtheindividualstructural
componentsisknownasnondestructiveevaluation(NDE)ornondestructive
inspection.NDEtechniquesincludethoseinvolvingacoustics,dye
penetrating,eddycurrent,emissionspectroscopy,fiber-opticsensors,
fiber-scope,hardnesstesting,isotope,leaktesting,optics,magneticparticles,
magneticperturbation,X-ray,noisemeasurements,patternrecognition,
pulse-echo,ra-diography,andvisualinspection,etc.Mostofthesetechniques
havebeenusedsuccessfullytodetectlocationofcertain
elements,cracksorwelddefects,corrosion/erosion,andsoon.The
FederalHighwayAdministration(FHWA,USA)wassponsoringalargeprogramof
researchanddevelopmentinnewtechnologiesforthenondestructive
evaluationofhighwaybridges.Oneofthetwomainobjectivesoftheprogram
istodevelopnewtoolsandtechniquestosolvespecificproblems.Theotheris
todeveloptechnologiesforthequantitativeassessmentoftheconditionof