Experimental study of influencing pile to cap connections on the rocking behaviors of piled foundations

Rocking foundations offer potential benefits, such as energy dissipation and reduced superstructure ductility demand during severe earthquake loadings. However, it can result in residual deformations at the soil-foundation interface, and uncertainties regarding its performance still remain, particularly for pile-supported structures. For the foundation of structures like tall bridges supported by pile groups, the system's behavior during rocking motions can be influenced by various factors, such as static vertical safety factor, pile-to-cap connection, and pile length. The present study explores influences of pile-to-cap connections on the rocking behavior of the system for different pile group lengths and static safety factors. A physical single-degree-of-freedom (SDOF) structural model with a novel semi-fixed pile-to-cap connection was developed for this study. Results indicate that unrestricted rocking on unattached connections lead to significantly lower residual settlements than those for fixed connections. Also, semi-fixed connections reduce settlements for long pile groups, with a slight decrease in resistance moment capacity. Moreover, unattached connections demonstrate a superior energy dissipation ratio of the system compared to that for fixed ones, in long pile groups with low bearing safety factors. The current study would expand our insight into the performance of different pile-to-cap connections under various conditions during rocking motions.