Design method for piles subjected to cyclic axial loading for control of permanent accumulated settlement

The pile capacity degrades and the permanent settlement of pile accumulates when the pile is subjected to low-amplitude and long-term axial cyclic loading. The degradation of the pile capacity and the permanent accumulated settlement of the pile will greatly influence the service ability of settlement-sensitive superstructures, such as high-speed railway tracks, wind turbines and so on. The general design requirements of piles under cyclic axial loading and the key issues that are of great interest to the designers are introduced. The behaviors of piles under axial cyclic loading are presented and the main factors influencing them are discussed. The definitions of load ratios are given. The criteria for assessing pile response based on the limit cyclic loading ratio are proposed. The idea of a cyclic interaction diagram is developed. The design method and procedure for piles under cyclic axial loading are proposed. Finally, a case is given to verify the proposed design approach.