NONLINEAR SEISMIC ANALYSIS OF SUBGRADE PILES WITH SOIL DURING STRONG GROUND MOTIONS

摘要

During strong ground motions in the Hyogoken Nanbu earthquake (1995), the substantial soil deformation and the big inertial forces from superstructure are considered to have concern with bridge piles damage. Piles and surrounding soil are supposed to have experienced nonlinear, with possible contribution of axial force fluctuation in the pile behavior. In the present study, we investigate the effects of RC pile nonlinear behavior in view of the bending moment-axial force relationship on the response of a pile-supported bridge system. The analysis is conducted by the two-dimensional nonlinear time domain FEM-BEM hybrid technique. The RC pile nonlinearity is represented by the one component model for the pile idealization and by the modified Q-hyst model for the hysteretic rule. The modification of Q-hyst model takes into account the relationship between bending moment-curvature depending on axial force. The nonlinear soil behavior is characterized by the modified Hardin-Drnevich hyperbolic model and by the Mohr stress circle criterion. The study of a typical Hanshin Highway bridge indicates that the soil behavior is practically insensitive to RC piles behavior and the presence of piles changes the soil behavior especially at interface zone across soil layers. Furthermore, the presence of axial force affects the pile nonlinear behavior and the heavy damage in the Hanshin disaster may possibly be due to tension force and bending moment interaction.