| In order to meet the requirements of economic development,China will carry out a large number of high-speed railway construction in the western region,part of the bridge will pass through or close to the high intensity near fault area.Therefore,improving the seismic isolation performance of railway Bridges under the action of near-fault earthquakes is of great significance to reduce the damage of bridge structures.DVA bearing is a new type of seismic isolation bearing,which is mainly composed of hyperboloid friction pendulum bearing and viscous damper.The bearing adopts the principle of dynamic vibration absorption,and applies the typical dynamic resonance system to simply supported beam bridge.In this paper,based on the actual 32 m span railway simply supported beam bridge engineering project,shaking table scale model test is carried out to study the damping and isolation performance of DVA bearing under the action of near-fault earthquake.The main research contents are as follows:(1)According to the seismic fortification requirements of the prototype bridge,5 seismic waves of common occurrence(0.14g)and design(0.4g)were selected as the ground motion input of the shaking table test.According to the experimental phenomenon and measured data,the peak displacement of the pedestal and pier top is less than 30 mm under the action of a 9-degree designed earthquake.The addition of vertical ground motion leads to the phenomenon of girder jumping,but there is no adverse earthquake damage such as girder falling.The pier works in plastic state under the designed earthquake action,and the DVA bearing has better protection effect on the pier under the vertical earthquake action.(2)The OpenSEES universal finite element software is used to establish a full-bridge scale model,and the finite element calculation results are compared with the measured data of shaking table test,and the causes of test errors are analyzed.By comparing the theoretical natural vibration period of the full bridge scale model with that of the full scale model,it is found that the errors of the first ten natural vibration periods are all about 10%,which verifies the correctness of the scale model.(3)By establishing the full-scale finite element model of the bridge and comparing the seismic isolation effect of DVA bearing and ordinary friction pendulum bearing,it is found that the seismic isolation performance of DVA bearing is better than that of ordinary friction pendulum bearing in many aspects.Under the action of rare earthquake,the advantage of DVA bearing is more obvious,and the control effect of DVA bearing on bridge structure is more stable than that of ordinary friction pendulum bearing.(4)The key parameters of DVA bearing are analyzed.By comparing the seismic responses of bridge key structures under different bearing parameters,the optimum bearing parameters are determined.It is found that for the specific bridge studied in this paper,the optimal equivalent radius of support is 4.5m,the optimal value range of friction coefficient is 0.04～0.06,the optimal value range of viscous damper damping coefficient is 1000～1100kN·s/m,and the optimal value of damping index is 0.6. |
