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Dynamic Responses of Spar-type Floating Offshore Wind Turbine Under Combined Wind, Wave, Current and Earthquake Actions
Piguang Wang, Hao Feng, Ruisheng Ma, Mi Zhao and Xiuli Du

Floating offshore wind turbines (FOWTs) operate in multi-hazard marine environments, contending with winds, waves, strong currents, and earthquakes, which affect their structural integrity,energy conversion efficiency, and long-term stability. To study the dynamic responses of FOWTs subjected to environmental loads, a finite element model of OC3-Hywind Spar-type floating foundation and NREL 5MW wind turbine is established in this paper. Firstly, the dynamic responses of the FOWT under earthquakes with different incident angles are calculated. Subsequently, the dynamic responses of the FOWT subjected to winds and regular waves are analyzed. Finally, the dynamic responses of the FOWT considering the combination effect of different loads are presented. The results show that The directionality of loads is a non-ignorable variable in the performance assessment of FOWT. For waves and earthquakes, the most critical incident angle of FOWT is 90°. The combined wind, wave, current and earthquake actions should be carefully considered in the design of FOWT. In addition, it is also found the mooring system possesses an “isolating” effect, which could reduce the earthquake energy transferred upward.

Keywords: floating offshore wind turbine, spar-type foundation, earthquake, multi-hazard, dynamic response