Bridgeseismicisolationstrategyisbasedonthereductionofshearforcestransmittedfromthesuperstructuretothepiersbytwomeans:shiftingnaturalperiodandearthquakeinputenergyreductionbydissipationconcentratedinprotectiondevices.Inthispaper,astochasticanalysisofasimpleisolatedbridgemodelfordifferentbridgeanddeviceparametersisconductedtoassesstheefficiencyofthisseismicprotectionstrategy.Toachievethisaim,asimplenonlinearsofteningconstitutivelawisadoptedtomodelawiderangeofisolationdevices,characterizedbyonlythreeessentialmechanicalparameters.Asaconsequenceoftherandomnatureofseismicmotion,aprobabilisticanalysisiscarriedoutandthetimemodulatedKanai-Tajimistochasticprocessisadoptedtorepresenttheseismicaction.TheresponsecovarianceinthestatespaceisobtainedbysolvingtheLyapunovequationforastochasticlinearizedsystem.Afterasensitivityanalysis,thefailureprobabilityreferredtoextremedisplacementandthemeanvalueofdissipatedenergyareassessedbyusingtheintroducedstochasticindicesofseismicbridgeprotectionefficiency.Aparametricanalysisforprotectivedeviceswithdifferentmechanicalparametersisdevelopedforaproperselectionofparametersofisolationdevicesunderdifferentsituations.
