Three-Dimensional Analytical Model and Seismic Response Analysis of Bridges with Rectangular Rocking Columns

Rocking structures show great promise in enhancing seismic resilience by reducing structural damage and minimizing residual displacements under seismic loads. Due to the complexity of rocking dynamics, analytical solutions for rocking structures have primarily relied upon the assumption of idealized planar conditions, which contradicts the fact that ground motion excitations along different directions will inevitably trigger three-dimensional (3D) rocking behaviors. Built upon the model derivation for freestanding rigid rocking blocks, this study develops an advanced 3D analytical model for the complete rocking bridge with rectangular rocking columns. The novelty of the 3D model lies in that it considers the local depth of compression during rocking impact and the distinct boundary condition provided by sliding bearings at end abutments. Bidirectional shaking table tests of a reduced-scale rocking bridge have been conducted to validate the effectiveness of the proposed 3D analytical model. Subsequently, a thorough investigation is carried out against the overturning stability of the bridge when subjected to ground motions represented by asymmetric Ricker wavelets. Response characteristics of the bridges are also examined systematically under a large suite of recorded ground motions. The analyses disclose the increased overturning possibility and amplified deck responses under bidirectional loading. Further, the bearing boundary condition and depth of compression show a great impact on the ranking of ground motion intensity measures that affect the bridge responses. Integrating these effects into the proposed analytical model would change the most efficient IMs from duration-based measures to spectrum-based measures.