Research On The Parameter Sensitivity Of Seismic Response Of Isolated Bridge

Bridge seismic isolation technology has become one of the most effective seismic design methods by extending the natural vibration period of the structure,avoiding the range of seismic energy concentration,and increasing the damping of the structure to dissipate seismic energy.The U S AASHTO Guide Specification For Seismic Isolation Design mentioned the characteristic correction factor of the isolation system,which mod-ified the mechanical parameters of the isolation bearing affected by temperature,aging,wear,pollution,etc.,to cover the seismic response of the bridge.Based on the theory of correction coefficient of bearing characteristics,this paper studies the sensitivity of me-chanical parameters of damping and isolation bearing.The main work is as follows:（1）The bearing characteristic correction coefficient mentioned in the American AASHTO specification is explained,and the influence of factors such as temperature,aging and disturbance on the rubber bearing,and the influence of factors such as temper-ature,aging,wear and pollution on the sliding bearing are respectively explained.The specific values of the correction coefficients of each influencing factor are introduced,as well as the correction process of the characteristic strength and post-yield stiffness of the bearing,and the adjustment coefficients and limit analysis methods are introduced.（2）Taking the Duodi Interchange Bridge of Lalin Expressway in Xizang Province as the engineering background,the seismic response analysis of the isolated continuous girder bridge is carried out.The influence of temperature correction coefficient,aging correction coefficient and disturbance correction coefficient on the isolation bridge with different pier height is considered respectively by selecting appropriate lead-core rubber bearing and high damping rubber bearing.Then the temperature,aging,disturbance and other factors are considered comprehensively,and the adjustment coefficient is adopted for correction,and the calculation and analysis are made.The results show that low tem-perature and aging of support can significantly increase the seismic response of the iso-lated bridge.When the pier height is low,the displacement of pier top,bending moment of pier bottom and shear force increase obviously.Among them,pier top displacement is most affected by temperature,aging,disturbance and other factors,followed by pier low bending moment and pier low shear force.The influence of temperature,aging and other factors on Bridges with high damping rubber bearing and Bridges with lead rubber bear-ing are also different.Therefore,in the seismic design should take into account the change of mechanical parameters of the support,reasonable selection of damping and isolation support,reasonable design of pier height,to reduce the temperature,support aging and other factors on the impact of isolation bridge.（3）The parameter sensitivities of pre-yield stiffness K₁,post-yield stiffness K₂ and yield displacement d_y of high damping rubber bearing were studied.Assume that the pre-yield stiffness and post-yield stiffness increase in the same proportion and increase in different proportions,and calculate the seismic response.It is concluded that when K₁and K₂ increase in the same proportion,the displacement of bridge pier top,shear force and bending moment of bridge pier bottom increase linearly.The influence of the change of K₂ on the seismic response of the bridge is related to the increase of K₁.Considering the reduction of the bearing yield displacement d_y,the ratio of post-yield stiffness to pre-yield stiffness r is introduced.When the ratio r is relatively large,the change of yield displacement has little influence on the seismic response of the bridge,while when r is relatively small,the change of yield displacement has great influence on the seismic re-sponse of the bridge.