Seismic performance of continuous bridges under mainshock-aftershock-like sequences with rotatable bonded laminated rubber bearings accommodating support rotation

Abstract

Continuous bridges are often equipped with bonded laminated rubber bearings (B-LRBs) to accommodate the thermal movements of bridge superstructure. In addition to the shear and compression stresses typically experienced by B-LRBs, support rotations can introduce pure bending stresses, which pose a significant threat to the behavior of bearings. This study proposes a rotatable B-LRB configuration aimed at mitigating the adverse effects of support rotations. The longitudinal seismic responses of a two-span continuous bridge, equipped with conventional and rotatable B-LRBs, were analyzed and compared under mainshock-only and mainshock-aftershock earthquake scenarios. The results highlight the substantial impact of support rotations on bearing forces, with rotation-induced bending moments accounting for 40%–80 % of the total bending moment in conventional B-LRBs. This effect significantly increases the risk of bearing failure, which, however, can be effectively eliminated with the rotatable B-LRBs. The effectiveness of the rotatable bearings is particularly evident during mainshock-aftershock sequences. Premature failure of conventional B-LRBs during mainshocks exacerbates bridge damage in the subsequent aftershocks, leading to catastrophic consequences such as span unseating, which contradicts the seismic design strategy of ductile bridge piers. In contrast, the rotatable B-LRBs can prevent the failures associated with the bearings, contributing to a more predictable bridge seismic response.