Single Pile Behavior Under Repeated Horizontal Loading

Abstract

Over the years, several marine structures with pile foundations have been proposed. Typically, such structures are repeatedly subjected to horizontal loading along numerous directions and at various load levels under the effects of waves or winds. However, the current Japanese design method examines these structures at the maximum load of virgin loading and rarely considers the deformation change of the pile owing to repeated loading. In this study, repeated horizontal loading experiments were conducted on single piles to examine the deformation behavior of such piles with respect to the loading directions and the preceding repeated loading. The maximum load was fixed, the minimum load was varied in each experimental case, and the unloading ratio (= minimum horizontal load/maximum horizontal load) was varied. Consequently, in the positive ratio, the increase in the ground surface displacement corresponded with the increase in the number of cycles. However, in the negative ratio, unexpected changes were observed in the behavior of the piles during monotonic loading. The results of the ground surface displacement and the bending moment distributions in the two-stage loading experiments, with regard to the behavior of piles subjected to preceding repeated loading demonstrated that, the considerable attention should be paid to the behavior of piles at the maximum load level when subjected to repetitive actions at different load levels. In particular, when the preceding load was smaller, the effect of the preceding load was negligible.