地震空间变化性对高墩铁路桥碰撞响应的影响

为了研究不同地震动参数对高墩铁路桥碰撞的影响，以一座典型高墩铁路桥为例，基于OpenSees平台采用弹塑性动力时程分析方法对其在一致激励及多点激励下的碰撞响应进行了理论分析.首先，采用Hertz-damp模型充分考虑了结构在碰撞过程中的能量耗散和刚度变化；其次，依据中国桥梁抗震规范并基于"谱兼容"的方法选取了符合不同场地条件的天然地震记录；最后，在此基础上完成了考虑行波效应和场地效应的高墩桥碰撞响应对比分析.研究结果表明:地震动的空间变化性不但会对桥梁结构的内力产生显著影响，还会增大结构的振幅或加剧相邻结构之间的不同步振动，从而显著增大碰撞发生的概率和碰撞力的大小，在桥梁的抗震设计中应考虑其对桥梁结构碰撞产生的影响，否则会错误的估计结构的响应；行波效应会改变地震动的相位角，对梁-梁处的碰撞影响更为显著，特别是视波速较小时，而场地效应会增大地震动的幅值，对梁-桥台处的碰撞影响更为显著，在进行防撞减撞设计时不但要考虑地震动的空间效应，还应充分考虑导致结构不同部位发生碰撞的主要因素，以便采取合适的减撞措施和设计方法. 

Effect of Ground Motion Spatial Variations on Pounding Response of High-Pier Railway Bridge

The authors present a theoretical analysis for a typical HPRB under synchronous and asynchronous excitations, using nonlinear dynamic analysis based on OpenSees, to investigate the effect of ground motion spatial variations (GMSVs) on the pounding response of high-pier railway bridges (HPRBs). The Hertz-damp model was adopted to simulate energy dissipation and the change in stiffness during pounding. In accordance with the Chinese seismic code of bridges, actual ground motion records were selected for each site condition by using the spectrum match method, and then, a comparative analysis was conducted considering both the wave-path and local site effects. The results show that GMSVs not only increases the seismic responses of the bridge structure but also increases the amplitude and non-synchronous vibration of adjacent structures, which will result in more pounding. Therefore, special attention should be paid on the effect of GMSVs on the seismic design of high-pier bridges. Otherwise, the responses of the bridge structure will be incorrectly estimated. Moreover, the wave-path effect may become more evident for beam-beam pounding by changing the phase angle of ground motions, especially, for a lower apparent velocity, while the local site effect may become more evident for beam-abutment pounding by increasing the amplitude of ground motions. It is suggested that both GMSVs and the leading cause of pounding at different locations should be considered for adopting an appropriate seismic design method and measures to mitigate or prevent pounding.