Seismic uplift behavior and energy dissipation mechanism of scoured bridge pile-group foundations: Quasi-static test and numerical analysis

Abstract

Seismic-induced pile uplift is likely to happen in coastal bridges with scoured pile-group foundations. This study investigates the seismic performance of scoured pile-group foundations with pile uplift behavior. To this end, a quasi-static test was conducted on a reinforced concrete specimen comprising a rigid single-column pier and a 2 × 2 pile-group foundation partially embedded in homogeneous sand. Cyclic lateral loading was imposed near the top of pier to produce sufficient bending moments on the foundation for achieving the pile uplift behavior. After that, a finite element (FE) model for the quasi-static test is developed and validated using the experimental data. An in-depth comparative study is conducted on two FE models with and without pile uplift. Results show that bridge models with pile uplift show apparent self-centering behavior, while those without pile uplift do not. Pile uplift prevents the yielding of pile head sections and meanwhile delays the yielding of underground ones. Besides, bridges with or without pile uplift have quite close total energy dissipation capacity, but the contribution of soil-pile frictional interaction is greatly increased (from 24% to 76%) while the contribution of structural damage is significantly decreased (from 40% to 2%) due to pile uplift.