Dynamic Response of a 15 MW Jacket-Supported Offshore Wind Turbine Excited by Different Loadings

This study investigates the dynamic behavior of a jacket-supported offshore wind turbine (JOWT) by developing its substructure and controller tailored for the IEA 15 MW reference wind turbine. A fully coupled numerical model integrating the turbine, jacket, and pile is established to analyze the natural frequencies and dynamic responses of the system under wind–wave–current loading and seismic excitations. Validation studies confirm that the proposed 15 MW JOWT configuration complies with international standards regarding natural frequency constraints, bearing capacity requirements, and serviceability limit state criteria. Notably, the fixed-base assumption leads to overestimations of natural frequencies by 32.4% and 13.9% in the fore-aft third- and fourth-order modes, respectively, highlighting the necessity of soil–structure interaction (SSI) modeling. During both operational and extreme wind–wave conditions, structural responses are governed by first-mode vibrations, with the pile-head axial forces constituting the primary resistance against jacket overturning moments. In contrast, seismic excitations conversely trigger significantly higher-mode activation in the support structure, where SSI effects substantially influence response magnitudes. Comparative analysis demonstrates that neglecting SSI underestimates peak seismic responses under the BCR (Bonds Corner Record of 1979 Imperial Valley Earthquake) ground motion by 29% (nacelle acceleration), 21% (yaw-bearing bending moment), 42% (yaw-bearing shear force), and 17% (tower-base bending moment).