Investigating the P–delta effect on displacement ductility capacity of scoured fixed-head piles in cohesive soil

Abstract

The seismic performance of piles in a river is susceptible to scouring. The removal of soil results in a decrease in lateral strength and an increase in lateral displacement of the piles. Therefore, scoured piles may undergo a pronounced P–Δ effect, which will cause a reduction in the pile’s strength. In this study, we numerically and theoretically investigate the P–Δ effect on the displacement ductility capacity of scoured fixed-head piles in cohesive soil. A long pile embedded in a Winkler-type soil with constant soil stiffness is simulated. The pile section has nonlinear flexural properties, which are assumed to be a bilinear moment–curvature relationship. The results show that the P–Δ effect has a different influence on the displacement ductility capacity depending on ultimate states. When the ultimate state is governed by the pile-head bending failure, considering the P–Δ effect increases the displacement ductility capacity; whereas when the ultimate state is governed by the occurrence of in-ground plastic hinging, the P–Δ effect can reduce the displacement ductility capacity.