铅芯橡胶支座隔震铁路简支梁桥双向地震响应分析

采用铅芯橡胶支座,选取具有不同固有周期的4座铁路简支梁桥桥墩,建立空间有限元模型。以7组典型地震波作为激励,进行铅芯橡胶支座隔震铁路简支梁桥的双向地震响应分析。采用时程分析法计算考虑和不考虑铅芯橡胶支座恢复力耦合作用的隔震桥墩系统的地震响应。分析结果表明:双向地震动作用下考虑耦合作用的铅芯橡胶支座的位移—恢复力曲线与单向地震作用下不考虑双向恢复力的耦合作用时的位移—恢复力曲线在形状上存在较大差别,铅芯橡胶支座的滞回耗能也不相同;不同地震激励下铅芯橡胶支座恢复力的耦合作用对铅芯橡胶支座峰值位移的影响程度不同;随着桥墩一阶固有周期的增加,铅芯橡胶支座恢复力的耦合作用对一阶振型方向的支座峰值位移的影响程度逐渐增大;梁体的峰值地震响应的规范计算值大都高于实际值,故按照规范值进行铁路简支梁桥的隔震设计偏于安全。

Analysis of the Bidirectional Seismic Responses for Seismically Isolated Railway Simple Supported Beam Bridge by Lead Rubber Bearing

Based on the lead rubber bearing and four piers with different natural periods of railway simple supported beam bridge,the three dimensional FEA models are established.The bidirectional seismic responses analyses of railway simple supported beam bridges isolated by lead rubber bearings are carried out under the excitations of seven pairs of earthquake waves.Using the method of time-history analysis,the seismic responses of isolated bridge pier systems with and without the coupled effect of the restoring forces of the lead rubber bearings are calculated and compared.The analyses results show that the displacement-restoring force hysteretic curves and the hysteretic energy dissipation of the lead rubber bearing under bidirectional ground motions considering the coupled effects are different from those of under unidirectional motions not considering the coupled effects.The coupled effects of the restoring forces on the peak displacements of the lead rubber bearing are different under the excitations of different earthquake waves.The coupled effect on the peak displacement of the lead rubber bearing in the direction of the first mode increases with the increasing of the first natural period of the bridge pier.The peak seismic responses of beams computed based on design codes are almost larger than those of the actual values.The seismic isolation design for the railway simple supported beam bridge according to the results calculated by design codes intends safety.