Dynamic response of offshore wind turbine supported by suction bucket in clay considering scour

The suction bucket foundation offers cost-effective and simple construction method for offshore wind turbines (OWTs). However, marine environment involves complex loading schemes, where suction bucket-supported OWTs would be subjected to wind, waves, currents, and earthquake loading, and may be subject to scour caused by prolonged wave and current actions. Currently, there is a paucity of research on how scour influences the dynamic response of suction bucket-supported OWTs. This study systematically investigates the influence of scour on the dynamic responses of suction bucket-supported OWTs under seismic, wind, and wave loads through comprehensive three-dimensional numerical analysis. Research findings demonstrate that scouring can decrease the natural frequency of suction bucket-supported OWTs by up to approximately 1% and the lateral ultimate bearing capacity by up to approximately 10%. Scouring amplifies the dynamic response of OWTs under windwave loads, with the wind speed exerting a more pronounced influence compared to the wave height. Scouring weakens the bucket-soil kinematic interaction and increases energy dissipation, which reduces the seismic response of the wind turbine structure. Seismic loads predominantly influence tower vibrations compared to wind-wave loads. In scenarios where earthquakes coincide with wind waves, wind-wave loads can mitigate the acceleration induced by seismic forces to some extent. There exists a nonlinear coupling relationship between wind and wave loads, as well as earthquake loads, making it advisable to employ a fully coupled method for OWTs response calculations.