近场地震作用下铁路减震桥梁地震响应研究

Seismic Response of Isolated Railway Bridge Subjected to Near-fault Ground Motion

为分析近场地震作用下的铁路减震桥梁顺桥向地震响应特性,用远场地震叠加三角函数型速度脉冲的方法模拟近场地震波,根据结构的弹塑性地震响应计算结果研究速度脉冲的波形、出现位置、脉冲时间对结构地震破坏的影响。结果表明:近场地震作用下铁路减震桥梁的减震效果降低,且支座的地震位移显著增大;速度脉冲波形、脉冲波发生时刻以及脉冲持续时间对桥梁地震响应有较大的影响;结构地震响应的最大值与地震波的SI值有较强的相关性,但与PGV/PGA值的相关性不明显;考虑限位装置地震碰撞效应以后,虽然支座地震位移得到了控制,但带来墩底剪力显著增大的问题;缓冲措施可以减小因碰撞引起的墩底剪力。

In order to analyze the longitudinal seismic behavior of isolated railway bridges subjected to near-fault ground motions, the near-fault ground motions were simulated by superimposing the trigonometric functions velocity pulses on the far-field seismic. The influence of waveform, occurrence and duration of velocity pulses on seismic responses of structure was studied according to the elastic-plastic seismic responses of struc tures. The results show as follows： The damping effect decreases while the bearing displacement increases significantly for isolated railway bridges subjected to near-fault ground motions; there is great influence of waveform,occurrence and duration of velocity pulses on seismic responses of bridges; the maximum seismic response is closely related to the value of SI,however,its relativity with the value of PGV/PGA is not obvious; taking into account the action of restrainer, the displacement of bearing decreases while the shearing stresses at the pier bottom increase remarkably;the shearing stresses at the pier bottom can be reduced by installation of buffer devices.