Nonlinear cyclic behavior of laterally loaded pile in cohesive soil

Abstract

Pile foundations may be subjected to lateral dynamic loads due to different hazards, such as impact of ships on bridge piers or jetties during berthing, wave and wind actions on offshore structures, and seismic wave motion on different buildings. The beam on nonlinear Winkler foundation (BNWF) approach is widely employed for predicting the response of piles under lateral loading because of its simplicity and practical accuracy. p–y curves are employed to represent the nonlinear soil reactions within the framework of the BNWF approach. However, they are empirically obtained from limited full-scale field tests and are not unique, accounting only for the pile width and not its mechanical properties. On the other hand, the strain wedge (SW) method allows the assessment of three-dimensional (3-D) soil–pile interaction of laterally loaded piles by incorporating soil continuity and pile properties as well as soil properties. In this study, the nonlinear p–y curves generated by the SW model are implemented as the backbone curve of developed BNWF model to effectively account for different response features of the pile–soil system. These features include the soil and pile nonlinear behavior, cyclic degradation of soil stiffness and strength, formation of soil–pile gap, and radiation damping. Two case studies of cyclic lateral load tests for single piles are investigated to examine the effects of soil degradation and gap formation on the response of laterally loaded piles embedded in cohesive soil. The developed model is shown to be capable of representing different soil–pile interaction features observed in experiments. The predictions of the developed BNWF model are in good agreement with experimental results. Finally, a comprehensive parametric study is performed to compare the predictions of the SWM-based model of the pile response under cyclic loading with that obtained from the conventional p–y curve–based model for different pile cross-section configurations, mechanical properties (strength and stiffness), and soil strength–stiffness.