简介:Dynamiccharacisticsoflargestructures,suchastallbuildings,long_spansuspension,cable_stayedbridgesandtallchimneys,includingrelativedisplacementsandvibratingfrequencies,arekeytoassesstheirdriftandstressconditions,Thesestr_ucturesaredifficulttomeasuredirectly,especiallyundertheconditionofearthquakesorstrongwind/typhoon.Ingeneral,accelerometersarethemostcommoninstrumentsusedtomonitortheresponseofstructuralsystems,butdisplacementmeasuringrequiresprocessingbydoubleintegration.Theintegrationprocesscannotbeautomatedbecauseofthefollowingrequirementsofsignalprocessing:(a)choiceoffiltersandbaselinecorrection(theconstantsofintegration),and(b)substantialjudgmentswhenanomaliesexistintherecords.Consequently,thisprocesscanleadtoerrorsinthecalculationofvelocitiesanddisplacements,someasurementswithaccelerometercannotbeusedtodiscoverdisplacementsatthecentimeterlevelinreal_timeornearreal_time.Othertraditionalmethods,likelasercollimatorandtotalstation,canbealsoappliedtomeasuredisplacementsatveryhighprecision,butcannotworkproperlyduringearthquakesorstrongwinds/typhoons,andinmostcasesdonotworkinreal_timeornearreal_time.Untilrecently,therearenoefficientorfeasiblemethodstomeasuredisplacementsduringanearthquakeorseverewind.Therefore,thereisagreatneedfordevelopinganewmethodortechniquetomonitorthedynamiccharacteristicsoflargestructurespreciselyinreal_timeornearreal_timeunderbadconditions. Fortunately,recentadvancesinGlobalPositioningSystem(GPS)technologyenableabove_mentionedlong_periodchangesofstructurestobereliablymonitored.GPSreceiverswithacapabilityofresolvingmotionatthecentimeterorsub_centimeterlevelandsamplingfrequency10Hzoreven20Hzarenowavailablefromseveralmanufacturers.Thatprovidesagreatopportunitytomonitorlong_periodchangesofstructuresreliably,andwillbeveryusefulfors
简介:Thispaperusesmulti-quadricequationsinterpolationtoes-tablishawidelycoveredandvaluablespeedfieldmodelofChina,withwhichthehorizontalcrustalmovementpatternsareobtained.Thepresent-dayverticalcrustalmovementvelocityim-ageofChinaisalsoexpressedbyGPSobservations,fromwhichwecanknowtheverticalcrustalmovementpatterns.
简介:Aseriesofadvantagesofsingledifference(SD)andundifferenced(ZD)modelsaregivenascomparedwitythedoubledifferenceezistinSDandZDmodels.Thereparameterizationmethodisprovidedtoresolvethisrankdefectproblembyestimatingsomecombinationsoftheunknownsratherthantheunknownsthemselves.TherepatameterizationofSDandZDfunctionalmodelsisdiscussedindetailwiththeirstochasticmodels.Thetheoreticalcomformationoftheequivalenceofundifferencedanddifferencedmodelsisdescribedinastraightforwardway.TherelationshipbetweenSDandZDresidualsisgivenandverifiedforsomespecialpurposes,e.g.researchonthestochasticalpropertiesofGPSobservations.