The new steel–concrete composite rigid-frame bridge (SCCRFB) with concrete-filled double skin steel tube (CFDST) piers has been verified showing superior seismic performance, and a promising structural solution for bridge constructions near or above active faults. Previous experimental and numerical studies revealed that the damages of this bridge type under across-fault ground motions mainly concentrate on the two CFDST piers. This paper investigates the effectiveness of damage mitigation measures for the SCCRFB with CFDST piers by using numerical simulations. Three detailed three-dimensional (3D) finite element (FE) bridge models are developed by using the explicit FE code LS-DYNA, in which Model A represents a reference SCCRFB with CFDST piers, and Models B and C employ different stiffeners at the two ends of the CFDST piers aiming to mitigate the damages induced by the effect of across-fault ground movements. Two pairs of across-fault ground motions with thrust and strike-slip mechanisms are considered, and the influence of fling-step is parametrically investigated. Numerical results including structural damages and responses are presented and the damage mechanisms are analyzed. Numerical results indicate that the strengthening measure used in Model C can effectively restrain local buckling of the steel tubes under both types of across-fault ground motions and is a practical option for SCCRFB with CFDST piers to mitigate the potential fault-crossing hazard. This study provides useful references for the seismic design of SCCRFB with CFDST piers crossing active faults.

经过验证的新型钢-混凝土复合刚架桥（SCCRFB）带有混凝土双壁钢管（CFDST）墩，具有出色的抗震性能，为活动断层附近或上方的桥梁施工提供了有希望的结构解决方案。先前的实验和数值研究表明，这种桥型在跨断层地震动下的破坏主要集中在两个CFDST墩上。本文通过数值模拟研究了带有CFDST墩的SCCRFB减震措施的有效性。通过使用显式FE代码LS-DYNA，开发了三个详细的三维（3D）有限元（FE）桥梁模型，其中模型A表示带有CFDST墩的参考SCCRFB，模型B和模型C在CFDST墩的两端采用了不同的加强筋，目的是减轻跨断层地面运动的影响所造成的破坏。考虑具有推力和走滑机制的两对跨断层地震动，并从参数上研究了跳阶的影响。给出了包括结构损伤和响应在内的数值结果，并分析了损伤机理。数值结果表明，C型模型中使用的加固措施可以有效地抑制两种跨断层地震动下钢管的局部屈曲，对于带有CFDST墩的SCCRFB减轻潜在的断层穿越危险是一种实用的选择。该研究为穿越活动断层的CFDST墩的SCCRFB抗震设计提供了有用的参考。