Numerical study of seismic performance of steel-concrete composite rigid-frame bridge with precast segmental CFDST piers crossing fault-rupture zones

Although seismic performance of bridges crossing fault-rupture zones has been studied in recent two decades, there is still no effective solution to mitigate the hazard of fault-crossing effect. Recently, a new type of posttensioned precast segmental (PTPS) concrete-filled double skin steel tube (CFDST), known as PTPS-CFDST column, has been proposed and verified to exhibit excellent performance with respect to seismic resilience. Moreover, PTPS-CFDST columns can accommodate torsional deformation through joint slip and are thus considered as a promising structural solution for bridges crossing fault-rupture zones. This study aims to investigate the performance of a steel-concrete composite rigid-frame bridge (SCCRFB) with PTPS-CFDST piers subjected to across-fault ground motions through numerical simulations. Two detailed three-dimensional (3D) finite element (FE) bridge models are developed using the explicit FE code LS-DYNA. In particular, Bridge 1 uses the new PTPS-CFDST pier, while Bridge 2 serves as a reference model with monolithic CFDST piers. Two types of across-fault ground motions with strike- and dip-slip mechanisms are used as seismic inputs, and the influence of fling-step is parametrically investigated. Structural responses, including the global seismic responses, seismic damages, energy absorption, and local joint slip and opening, are systematically discussed. The numerical results indicate that, compared to the monolithic CFDST piers, PTPS-CFDST piers exhibit advantages in terms of seismic resilience, with lower damage and outstanding self-centering performance, which facilitates post-earthquake recovery after experiencing across-fault ground motions. This study provides valuable references for the seismic design of bridges with PTPS-CFDST piers crossing fault-rupture zones.