Vulnerability Analysis And Aseismic Control Of Curved Bridge Subjected To Near-fault Ground Motions

Bridge is the key point in traffic network,and the importance of seismic capacity of bridge is self-evident.Curve beam bridge has strong crossing ability,so its widely used in highway and urban interchange in the west of China.Besides,there are many seismic faults distributed in the west of China,and the near-fault ground motion is a great threat to the safety performance of these curved bridges.Compared with far-field ground motion,near-fault ground motion show some different characteristics.At present,there are few researches on the seismic performance of curved bridge under near-fault ground motion.Moreover,the seismic response spectrum and fortification standard in seismic code of China are only for far-field ground motion.Vulnerability analysis of bridge can assess the seismic performance of the bridge in detail,this paper will analyze and compare the vulnerability of curved bridge under near-fault ground motion and far-field ground motion.After exploring the difference and reason,this paper will give some measures to reduce the damage of curved bridge under near-fault ground motion The main contents of this paper are as follows:(1)First,the finite element model of the curved bridge is established,then the damage indexes of the bearing and the pier are specified.Finally,the limit values of different degrees of damage are determined.According to the recommendations of literature and specifications,10 near-fault ground motion records and 10 far-field ground motion records are selected.(2)This paper analyze the vulnerability curves of the bearing,pier and whole bridge under near-fault ground motion and far-field ground motion.Besides,the differences between the two are compared.Then,investigate the causes of near-fault earthquakes exacerbating the damage of bridge from the response spectrum characteristics,spectrum characteristics and energy characteristics of seismic waves.More,change the excitation direction of near-fault seismic wave and obtain the vulnerability cloud map of bearing,pier and whole bridge under different excitation direction.Finally,analyze the influence of excitation direction on vulnerability,and obtain the most unfavorable direction of curved bridge.(3)Based on the characteristics of near-fault ground motion,this paper give some suggestions for shock-absorbing fortification of curved bridges.The shock-absorber is essentially a kind of soft steel damper,which can enhance the seismic performance of curved bridge under near-fault ground motion by arranging the shock-absorber around the bearing.Finally,evaluate and optimize the layout scheme of the shock-absorber based on the analysis results of vulnerability.