Seismic Analyses of Rocking Bridges Considering Vehicle‐Bridge Interaction

ABSTRACT Rocking piers have attracted increasing attention due to their promise to simultaneously reduce structural damage and residual displacement of the bridge during seismic shaking. However, the literature lacks a thorough investigation of the system rocking behavior when taking into account the vertical vibration of the deck and the presence of vehicles on the bridge. This study derives an advanced analytical model to fill this research gap. A vehicle model represented by a mass‐spring‐damping system is adopted to derive the dynamics equilibrium of the vehicle‐bridge system (VRB). The derivation is followed by coupling the system's rocking motion through the examination of rocking kinematics, initiation criterion, and energy dissipations during impacts. The analytical model investigates the rocking spectra and overturning stability of the VRB system under different vehicle masses, speeds, and vertical frequencies. It evaluates bridge responses under (1) Ricker wavelets representing pulse‐type excitations and (2) recorded spectrally equivalent long‐ and short‐duration ground motions. Results indicate that the pulse effects on the rocking response depend on its excitation frequency and type (i.e., symmetric vs. antisymmetric). Long‐duration seismic effect can significantly amplify or reduce the seismic responses of both piers and vehicles, although it has a minor effect on these responses on average. Conversely, heavier vehicles can mitigate the rigid‐body‐like displacement of the deck, while increasing its elastic deformation. In turn, bridge rocking also affects vehicle responses in vertical and driving directions, which will impair driving comfort and safety, and increase the potential risk of vehicle collision.