Performance of piled raft foundations subjected to dynamic loading

Abstract

A series of shaking table tests were conducted on piled raft foundations on sand by using a geotechnical centrifuge. The results were compared with those obtained from the static horizontal loading tests of the same models which have been reported by Horikoshi et al. (2003). Effects of the rigidity at pile head connection on the dynamic behavior were examined. Also shown are the results of the dynamic loading test of a free-standing pile group with the same number of piles to examine the contribution of the load transferred through the raft base. Principal findings from the present study are: 1) The horizontal load-displacement relationships and the bending moment distributions agree well between the dynamic models and the static models. The proportion of the horizontal load carried by each component is highly dependent on the horizontal displacement of the piled raft system; 2) The horizontal stiffness of the piled raft with the hinged pile head connection was smaller than that of the piled raft with the rigid pile head connection; 3) The proportion of the vertical load carried by the piles remains largely unchanged during dynamic loading, while the proportion of horizontal load carried by the piles increases as the horizontal displacement increases; 4) The inclination of the piled raft during shaking is much smaller than that of the pile group due to the contribution of the soil resistance just beneath the raft.