Influence of longitudinal and transverse gaps of C-shaped steel restrainers on the seismic performance of friction-pendulum-isolated railway bridges under oblique seismic excitation

To prevent excessive displacement of friction pendulum bearings (FPBs) under earthquake action and the associated increase in unseating risk, this study considered a simply supported high-speed railway bridge with 50 m hollow piers. A full-bridge finite element model with FPBs equipped with C-shaped steel restraining members was established to investigate the effects of longitudinal and transverse gap variations under different seismic incidence angles on girder acceleration, bearing displacement, pier-top displacement, and pier-bottom bending moment. The results show that as the incidence angle, the longitudinal bridge response gradually decreases, while the transverse bridge response gradually increases. In addition, within the scope of the working conditions considered in this paper, the displacement of the longitudinal support does not reach changes longitudinal gap, and the the longitudinal gap has limited influence on the structural response. In contrast, the smaller the transverse gap is, the more easily the transverse bearing displacement reaches the gap. When the transverse gap is smaller, the transverse C-shaped steel participates in resisting force, making the limiting effect on the transverse displacement of the bearing more obvious, but at the same time, the acceleration of the main girder increases. The research results can provide a reference for parameter design and engineering applications of C-shaped steel FPBs.