Pounding Response And Simplified Design Method Of Isolated Continuous Girder Bridge With Pounding-Unseating-Prevention Device

Cable restrainers,dampers and rubber bumpers were widely used to prevent the pounding and unseating of the bridge decks under strong earthquake motions,and it was proven that restrainer devices can significantly reduce the seismic response of the structure,but it cannot prevent collision and limit displacement of the girder at the same time.Therefore,an pounding-unseating-prevention device composed of rubber bemper and steel retainer was proposed in this paper,and the analytical model of the rubber bumper was investigated.Furthermore,pounding response and simplified design methods of the RC isolated continuous girder bridge with pounding-unseating-prevention device were studied.The main contents of this paper are described as follows:(1)Research on mechanical properties and constitutive models of rubber bumper under impact loads.According to the static compression and impact test results,the influence of the size,material type,load form on the force-deformation relationship of the rubber bumper was studied.The stress distribution and energy changes of the rubber bumper under impact force were obtained by finite element analysis.According to the impact test results of rubber bumper,the nonlinear-viscoelastic impact model proposed by Polycarpou was modified.It is shown that the modified constitutive model is more consistent with the test results than the original one.(2)Unilateral impact response of isolated continuous girder bridge with pounding-unseating-prevention device.Based on equivalent linearization process of non-linear components of bridges such as piers and isolation bearings,a simplified analysis model of isolated continuous girder bridge that only considers the effect of the anti-collision device at the transition pier was proposed,and the natural vibration periods and seismic response of the analytical model were compared with the results of Open Sees FE model to verify its effectiveness.The simplified analysis model was numerically modeled in MATLAB,and the effects of natural vibration period of the structure,ductility of pier,lateral stiffness of the isolation bearings,stiffness and gap width of the pounding-unseating-prevention device on the unilateral impact response of the bridge were studied.It is shown that the natural vibration period,the lateral stiffness of the bearings,and the stiffness of the pounding-unseating-prevention device have a greater influence on the unilateral impact response of the structure.(3)Simplified design precedures of isolated continuous girder bridge equipped with pounding-unseating-prevention device.Based on the concept of impact force response spectrum,an simplified iterative design method for isolated continuous girder bridge equipped with pounding-unseating-prevention device was proposed in this paper in which the influence of vibration characteristics,ground motion characteristics and site conditions were considered by the impact force response spectrum.A simplified impact model of rubber bumper was developed in Open Sees.Then,non-linear time history analysis of the bridge FE model was carried out.By comparing the relative displacement and maximum pounding force of the bridge with and without pounding-unseating-prevention device,the effectiveness of the device and applicability of the simplified design method were verified.It is shown that the seismic response of the structure can be effectively reduced,pounding and unseating can be avoided,when the pounding-unseating-prevention devices were designed by the proposed method and arranged symmetrically at both ends of the deck.