Quasi-static tests and numerical simulations of ductile seismic behavior for scoured bridge pile group foundations considering pile uplift

Scour is the main hazard for coastal bridges. Compared to the fully embedded pile group foundation before scour, the scoured pile group foundation is more prone to the inelastic damage and pile uplift when subjected to earthquakes. However, the seismic behavior of the scoured bridge pile group considering both the ductile and uplift behavior of piles is yet to be documented. This study aims to reveal the ductile seismic behavior of the scoured pile group foundation considering the pile uplift behavior. To this end, quasi-static tests were performed on two reinforced concrete (RC) 3 x 2 pile group foundation specimens embedded in homogeneous sand with and without pile uplift. The lateral loads were separately applied to the cap center of the pile group and the top of the pier to reproduce the pile uplift effect on the foundation. The experimental result of these two specimens was comprehensively compared and discussed. Furthermore, the finite element models for the quasi-static tests were developed and validated. The experimental result indicates that the pile group without uplift shows ductile properties, whereas that with uplift exhibits both ductile and self-centering behavior. The uplift of piles reduces the lateral strength and residual lateral deformation of the ductile foundation. Moreover, the pile group with the pile uplift has a more considerable displacement ductility at the first yielding limit state of belowground piles but a smaller displacement ductility at the peak lateral strength and ultimate residual strength limit states. The findings of this study provide insights into the seismic design/assessment of scoured bridges in coastal regions.