Abstract：Aiming at the issue of ice-induced vibration for offshore monopile wind turbines (OWTs) located in ice-infested waters, the dynamic responses of the NREL 5MW monopile OWT under the combined actions of ice and wind loads were studied in this work. The aerodynamic loading was computed using the MATLAB code developed based on the Blade Element Momentum (BEM) principle, considering the Prandtl’s tip loss factor and the Glauert correction. Based on the Määttänen self-excited model, APDL was employed to develop an ice-induced vibration analysis program. By using the ice data of one ice zone in the Bohai Sea, the dynamic responses of the OWT were calculated under different wind and ice load attack angles. The time and frequency domain analysis of the tower top and base displacements were carried out, the vibration characteristics were analyzed and the ice load frequency lock-in (FLI) scenarios were identified. Based on the simulation, the maximum vibration amplitude of the tower top and base displacement, the maximum overturning moment of the foundation as well as von Mises stress of the structure were provided. The results show that the dynamic responses of the tower and the substructure of the OWT are different under low and high ice velocities, but they are harmonic vibrations in the medium ice velocity. The frequency of the ice load was locked in the first modal of the structure under normal and extreme ice thicknesses. The ice velocity causing FLI ranges from 0.01m/s to 0.06m/s and from 0.03m/s to 0.09m/s under the normal ice condition and the extreme ice condition, respectively. The dynamic responses of the wind turbine were significant when the FLI happened. The maximum vibration amplitudes of the tower top under normal and extreme conditions were 1.42m and 1.45m, the maximum von Mises stress were 146MPa and 183MPa, and the overturning moments were 243MN and 358MN, respectively.The present study provides a reference for the design and optimization of the 5MW OWT structure installed in similar ice-infested waters.
