This paper presents experimental and theoretical research aimed at deepening the understanding of the lateral response of monopiles in sand subjected to cyclic loading. A series of 1-g model tests were performed for varying cyclic load and magnitude ratios, as well as for different pile stiffnesses. The broadly phenomenological behaviors of the monopile including accumulated displacement, cyclic secant stiffness, bending moment and reloading responses were captured. The results reveal the effects of cyclic load ratio, amplitude ratio and pile stiffness on the development of accumulated displacement and secant stiffness, and point out the action mechanism that the cyclic bending moment of rigid piles tends to increase while that of flexible piles tends to decrease. The elastic threshold of the reloading curve gradually increases with cycling, and increases with the increment of cyclic magnitude ratio. Crucially, a generalized model capable of describing the hysteretic characteristics of loading curves of monopiles was established, and the computational formulas for predicting the peak accumulated and residual displacements were derived. The reasonableness of the proposed method was verified under different loading parameters and pile-soil systems, which could be used for the preliminary design of offshore monopiles.
