Seismic response of clay-pile-raft-superstructure systems subjected to far field ground motions

A series of three-dimensional (3D) finite element analyses incorporated with a hyperbolic-hysteretic soil model were performed to investigate the seismic response of pile-raft-superstructure systems constructed on soft clay stratum, focusing on the seismic pile bending moment and superstructural responses. The seismic pile bending moment results suggested that using a lumped mass to represent the superstructure, which has been widely used in many other studies, could only perform well for a relatively low-rise superstructure; on the other hand, the seismic response of superstructure was found to be significantly affected by the soil-structure interaction, and both the detrimental and beneficial effects of dynamic soil -structure interaction were observed. Hence, coupled soil-foundation-superstructure analyses were primarily performed in this study. The influences of peak base acceleration, pile flexural rigidity and the configuration of superstructure on both the pile bending moment and superstructural responses were studied. Furthermore, some correlations were derived to relate the maximum pile bending moment to the influencing factors, which can be used as useful tools for obtaining preliminary and first order estimates of the maximum pile bending moment for pile-raft-superstructure systems constructed on soft clay deposits.