The present study explores analytically the concept of rocking isolation in bridges considering for the first time the influence of the abutment-backfill system. The dynamic response of rocking bridges with free-standing piers of same height and same section is examined assuming negligible deformation for the substructure and the superstructure. New relationships for the prediction of the bridge rocking motion are derived, including the equation of motion and the restitution coefficient at each impact at the rocking interfaces. The bridge structure is found to be susceptible to a failure mode related to the failure of the abutment-backfill system, which can occur prior to the well-known overturning of the rocking piers. Thus, a new failure spectrum is proposed called Failure Minimum Acceleration Spectrum (FMAS) which extends the overturning spectrum put forward in previous studies and it differs in principle from the latter. Parametric analyses are conducted with respect to the stiffness of the backfill, highlighting the importance of stiff profiles in rocking response of bridges. The comparison with the dynamic response of bridges modelled as rocking frames without abutments reveals that seat-type abutments and their backfill have a generally beneficial effect on the seismic performance of rocking pier bridges, but also that the simple frame model cannot capture all salient features of the rocking bridge response, as it misses potential failure modes, overestimating the rocking bridge’s safety when these modes are critical.

中文翻译：

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考虑桥台回填贡献的摇摆桥的动力学和抗震性能

本研究首次考虑了桥台-回填系统的影响，分析了桥梁摇摆隔离的概念。假设下部结构和上部结构的变形可忽略不计，研究了具有相同高度和相同截面的独立桥墩的摇摆桥的动力响应。推导出用于预测桥梁摇摆运动的新关系，包括摇摆界面处每次撞击时的运动方程和恢复系数。发现桥梁结构容易受到与桥台回填系统故障相关的故障模式的影响，这可能发生在众所周知的摇摆桥墩倾覆之前。因此，提出了一种新的失效谱，称为失效最小加速度谱（FMAS），它扩展了先前研究提出的倾覆谱，与后者在原理上有所不同。参数分析是针对回填土的刚度进行的，突出了刚度轮廓在桥梁摇摆响应中的重要性。与模拟为无桥台摇摆框架的桥梁的动力响应的比较表明，座式桥台及其回填对摇摆桥的抗震性能具有普遍有益的影响，但简单的框架模型无法捕捉到所有显着特征。摇桥响应，因为它错过了潜在的故障模式，当这些模式很关键时，会高估摇桥的安全性。