近断层地震动下摇摆-自复位桥墩地震反应分析

为讨论摇摆-自复位（Rocking Self-Centering，RSC）桥墩在近断层地震动下的地震反应，基于OpenSees数值分析平台建立了RSC桥墩抗震分析模型。同时建立了普通钢筋混凝土（Reinforced Concrete，RC）桥墩，配置竖向无粘结预应力筋（Unbonded Prestressed Reinforced Concrete，PRC）桥墩的抗震分析模型作为对比。对各模型输入近断层地震动记录，进行增量动力分析。以墩顶最大位移角、残余位移角、预应力筋最大应力为考察目标，对比分析了不同墩高（剪跨比分别为2、4和6）、不同桥墩类型（RSC、RC和PRC桥墩）时各桥墩的地震反应。结果表明：随着耗能钢筋配筋率增加，RSC桥墩墩顶最大位移角和预应力筋最大应力均减小；RSC和PRC桥墩均可有效减少桥墩震后残余位移角。耗能钢筋配筋率与PRC桥墩纵筋配筋率接近的RSC桥墩，两者的最大墩顶位移角、残余位移角和预应力筋应力水平均接近。无论是RSC桥墩还是PRC桥墩，当剪跨比大于等于6.0时，易发生预应力筋失效。为避免预应力筋失效引起RSC桥墩产生过大的墩顶残余变形，RSC桥墩中耗能钢筋配筋率不宜低于0.75%。

SEISMIC RESPONSE ANALYSIS OF THE ROCKING SELF-CENTERING BRIDGE PIERS UNDER THE NEAR-FAULT GROUND MOTIONS

To study the seismic response of the rocking self-centering (RSC) bridge piers under near-fault ground motions, a series of numerical analysis models for the piers were built based on the OpenSees. Also, the seismic analysis models for the reinforced concrete (RC) and unbonded prestressed reinforced concrete (PRC) piers were built for comparison with the behavior of the RSC piers. Incremental dynamic analysis (IDA) was conducted for all the piers under the near-fault ground motions. The peak drift ratio, the residual drift ratio and the maximum prestressing stress of all the piers were obtained and compared with each other, and the piers were designed with different heights (aspect ratio=2.0, 4.0 and 6.0), different types (RSC, RC and PRC piers). It is found that the peak drift ratio and the maximum prestressing stress of the RSC piers will be reduced with the increment of the mild reinforcement ratio. Compared with the RC piers, both the PRC and RSC piers have smaller residual drift ratio. The RSC piers, which have the similar mild reinforcement ratio as the longitudinal bar ratio of PRC piers, have almost the same peak drift, residual drift and the maximum prestressing stress compared with the PRC piers. Prestressing tendon failure damage would occur for both the RSC and PRC piers with an aspect ratio equal to or larger than 6.0. To avoid larger residual drift ratio of the RSC piers as a result of prestressing tendon failure, the mild reinforcement ratio of the RSC piers should not be less than 0.75%.