Numerical study of an ice-offshore wind turbine structure interaction with the pile-soil interaction under stochastic wind loads

Abstract

In order to better understand the ice-induced collision/vibration mechanism of offshore wind turbines (OWTs) with ice-breaking cones, the Tsai-Wu yield criterion of ice for bending failure is coupled to the nonlinear collision simulation tool ANSYS/LS-DYNA in this paper, and a numerical approach is adopted to predict dynamic ice force. Through comparisons of ice force between simulations and physical tests, the accuracy of dynamic ice force simulated by the proposed approach is verified. Meanwhile, to consider the pile-soil interaction (PSI) effect, the Euler-Bernoulli Beam theory and the Timoshenko Beam theory are used, respectively, and the dynamic characteristics of the OWT are compared and analyzed. The discrepancies between the calculation results of the two methods and the influence of PSI on OWTs under combined wind-ice conditions are discovered. Further, the fully coupled interaction model between ice and flexible OWT with PSI under wind and ice loadings is established. Based on the full three-dimensional (3D) interaction model, the influence of the ice velocities, ice thicknesses, and cone angles on the dynamic ice force and structural response is investigated. The area damage rate and fatigue damage rate of the monopile foundation are proposed to further carry out damage and fatigue analyses under wind and ice loads. Higher fatigue damage is associated with smaller area damage rate. In addition, the ice thickness has a more significant effect on OWT damage and fatigue compared with the ice velocity.