简介:Localizednatureofdamageinstructuresrequireslocalmeasurementsforstructuralhealthmonitoring.Thelocalmeasurementmeanstomeasurethelocal,usuallyhighermodesofthevibrationinastructure.Threefundamentalissuesaboutthelocalmeasurementforstructuralhealthmonitoringincluding(1)thenecessityofmakinglocalmeasurement,(2)thedifficultyofmakinglocalmeasurementand(3)howtomakelocalmeasurementareaddressedinthispaper.Theresultsfromboththeanalysisandthetestsshowthatthelocalmeasurementcansuccessfullymonitorthestructuralhealthstatusaslongasthelocalmodesareexcited.Unfortunately,theresultsalsoillustratethatitisdifficulttoexcitelocalmodesinastructure.Therefore,inordertocarrystructuralhealthmonitoringintoeffect,wemust(1)ensurethatthelocalmodesareexcited,and(2)deployenoughsensorsinastructuresothatthelocalmodescanbemonitored.
简介:ThispapermakesaprobeintotheapplicationoftheKalmanfilteringmethodtothedataprocessingofacross-faultmeasurements.Onthebasisofstatisticalregression,themathematicandstochasticmodelsoffiltrationareestablishedbycombiningtheregressionmethodwithKalmanfiltering.Inthefilteringcomputation,notonlytherandomnessoffaultmovementsbutalsothetime-dependentvariationofenvironmentaleffectshavebeentakenintoconsideration.Byuseoftheadaptivefilteringmethod,anestimationofthedynamicnoisevariancematrixisobtainedthroughiteration.Modelsforonemeasuringline(levelinglineorbaseline),twomeasuringlines(bothlevelinglinesorbothbaselines)andfourmeasuringlines(twolevelinglinesandtwobaselines)arederivedandestablishedsystematically.Bymeansofthesemodels,thedataofacross-faultmeasurementscanbeprocesseddynamicallyinreal-timetoprovidethefilteredvaluesofheightdifferencebetweenbenchmarksorbaselinelengthatdifferenttimein
简介:TwomethodsformeasuringtheattenuationQvalue,frequency-amplituderatiomethodandwaveforminversionmethod,wereanalyzed.Thesizeandshapeofmostrocksamplesinthelaboratorycanhardlyfulfilltherigorousrequirementsoftheabovemethods.AnewtestmethodofusingthewaveenergytocalculatetheQvaluewasproposed.Theprinciple,calculationformulaeandsomepointsforattentionwereexpounded;therelationshipbetweenQ_PandQ_Ewasdiscussed;andmanysamplesweremeasuredbythismethod.Theresultwascomparedwiththosebyothermethods,anditwasconsideredthattheQvaluebythismethodliesbetweenQ_PandQ_E·
简介:Platestructuresareemployedasimportantstructuralcomponentsinmanyengineeringapplications.Hence,assessingthestructuralconditionsofin-serviceplatestructuresiscriticaltomonitoringglobalstructuralhealth.Modalcurvature-baseddamagedetectiontechniqueshaverecentlygarneredconsiderableattentionfromtheresearchcommunity,andhavebecomeapromisingvibration-basedstructuralhealthmonitoringsolution.However,computingerrorsarisewhencalculatingmodalcurvaturesfromlateralmodeshapes,whichresultfromunavoidablemeasurementerrorsinthemodeshapesasidentifiedfromlateralvibrationsignals;thismakescurvature-basedalgorithmsthatusealateralmeasurementonlytheoreticallyfeasible,butpracticallyinfeasible.Therefore,inthisstudy,long-gaugefiberBragggratingstrainsensorsareemployedtoobtainamodalcurvaturewithoutanumericaldifferentiationprocedureinordertocircumventthecomputingerrors.Severaldamageindicesbasedonmodalcurvaturesthatweredevelopedtolocatebeamdamageareemployed.Bothnumericalandexperimentalstudiesareperformedtovalidatetheproposedapproach.However,althoughpreviousstudieshavereportedrelativesuccesswiththeapplicationofthesedamageindicesonasimplebeam,onlyonedamageindexdemonstratedthecapabilitytolocatedamagewhenthestiffnessofthelocalregionchangednearthesensor.
简介:Porepresureindepboreholes:ItsmeasurementandrelationwithseismicactivitiesJIANLIGAO(高建理)SHIZONGSUN(孙世宗)JIANMINDING(丁健民)GU...