Numerical simulation of dynamic response for pile groups of bridges in liquefiable soils

Abstract: Based on the u-pformulas and the Biot's dynamic coupled theory for saturated sand to consider the dynamic interaction of fluid and soil skeleton deformation, a three-dimensional (3D) numerical modelling of shaking table tests on dynamic soil-pile-bridge structure interaction in liquefiable soils is established using the Nishi model for sand and the Mohr-Coulomb model for clay. The pile and pier are simulated by 3D beam elements based on the Mindlin-Reissner theory. The clay and cap are divided with 20-node brick elements and the sand layer domains are discretized with solid-fluid fully coupled (u-p) 20-8 node brick elements. 3D line elements are used to simulate the soil-pile interaction and 3D contact elements are adopted to characterize the soil-cap interaction. Rayleigh damping is introduced into the dynamic soil-pile-bridge structure systems to consider the damping effects. Consistent boundary is employed to simulate artificial boundary of shaking table tests. The nonlinear system equations are solved by means of the backward Euler integration method under the gravity. Subsequently the Wison- successive integral method is chosen to solve the dynamic response of the system during seismic excitation. The experimental results are used to verify the validity and effectiveness of numerical modelling, which shows that the numerical procedure can simulate the fundamental aspects of dynamic soil-pile-structure interaction well.