Dynamic Behavior of Rocking Bridges Considering Deck Flexibility under Pulse-Type Ground Motions

The rocking bridge system, with its excellent self-centering ability and minimal post-earthquake damage, has become an effective alternative to bridges designed with ductile seismic philosophy. However, the rocking bridge system involves complex dynamic behaviors, such as impact, uplifting, and nonlinear boundary conditions, which limits the suitability of present theoretical models derived from rigid frames or isolated piers. In this paper, an improved analytical model that incorporates the flexibility of the deck and nonlinear boundaries is proposed to predict the dynamic behavior of the rocking bridge system. A thorough investigation of the response spectra and fragility of rocking bridge systems under various design parameters and pulse-type excitations is conducted based on the proposed model. Results indicate that the rocking bridge system may experience a failure sequence of abutment-bearing-pier during earthquakes. Specifically, the constraint effects of the bearing and foundation can either exacerbate or mitigate the dynamic responses of bridges, influenced by the dimensionless excitation frequency (i.e., ωp/p) and pulse type (i.e., symmetric versus antisymmetric). Abutment-backfill constraints and narrower expansion joints are conducive to reducing the probability of pier damage. Conversely, neglecting the flexibility of the deck during the rocking process may lead to significant underestimation of the dynamic response and seismic damage of rocking bridges.