| With the rapid development of transportation infrastructure in the southwestern mountainous areas of China in recent years,the application of the curve bridges with uneual height piers in traffic networks has become more and more widespread.Irregular curved bridges are more susceptible to the earthquake damage than the regular straight-line bridges.However,existing seismic design specifications of China have no specific provisions for the selection of bearing types and arrangement forms for curved bridges.Due to the influence of ground motion uncertainty,how to select the most unfavorable seismic wave input direction in seismic analysis of curved bridges remains to be studied.Therefore,a multi-span concrete continuous curved girder bridge with unequal height pier in Sichuan area are taken as an example.Based on the OpenSEE program,the bridge finite element analysis model is established,and the following research contents are carried out:(1)Seven sets of ground motions were selected according to the site type of case-study bridge.A series of nonlinear time history analysi was applied to investigate the influence of bridge bearing arrangement and bearing types on the seismic performance of the bridge.The results show that,the tangential relative deformation of each bearing is related to the lateral stiffness of the columns and abutment due to the bending-torsional coupling effect and the directional effect of the seismic wave.The tangential deformation of the bearing on the low piers are bigger than that on the the high piers.The maximum radial deformation of the bearing is not only sensitive to the bearing arrangement,but also closely related to the direction of the input seismic wave and the irregularity of the bridges.The low piers should adopt the plate type elasteric bearing or the sliding bearing.Meanwhile,the anti-seismic retainer(shear key)is used to limit the excessive lateral displacement of the main girder in the transverse direction.The lead rubber bearing or the fixed bearing should be used at the high pier.The lead rubber bearing should be used at the abutment.The direction of the tangential deformation for the curve bridge does not point to the oppsite abutment,so that the tangential deformation of the supper structure in the active direction of the abutment will be much larger than that of the traditional straight bridge,which easily lead to the girder falling failure at the abutment.Therefore,it should be taken seriously in the future seismic design of cruve bridges.(2)According to the optimal bearing arrangement,this paper qualitatively analyzed the influence of the input angle of the seismic wave on the seismic response of the curve bridges with unequal-height piers,by changing the input angle of the seismic wave(0-360 degrees).Then,100 seismic waves were slected to consider the influence of ground motion uncertainty,the seismic fragility curves of the columns and bearings for the curve bridges with unequal piers were established based on the probability reliability theory.The results show that,the ground motion input angles are different for different bridge component with the maxumin seismic response.The ground motion input angles have significant influences on seismic fragilities of the bridge piers and bearings.Each component seismic fragility analysis has the different most disadvantageous input angle.Therefore,the influence of the seismic wave input angle on the seismic resistance of the curved bridge should be considered in future seismic analysis of the curved bridges with different pier heights. |
