A real-time hybrid testing strategy for offshore wind turbines under wind–wave–earthquake loads using a frequency-decoupled wind load simulator

The expansion of offshore wind turbines into deep-sea environments necessitates rigorous testing under combined wind, wave, and earthquake loads. Real-Time Hybrid Testing(RTHT) offers an effective approach for evaluating these multi-hazard interactions. To address the Froude-Reynolds scaling conflict inherent in conventional physical modeling, this study proposes a novel Wind Load Simulator (WLS) system that decouples aerodynamic loading through a ​physical-frequency decoupling design: A Fluctuating Wind Load Simulator (FWLS) employing an electromagnetic shaker with improved three-variable control (ITVC) for high-frequency components, and An Average Wind Load Simulator (AWLS) utilizing a gravity-driven mass-pulley system for static loads. A dual-loop control with supplemental damping compensation to address broadband signal reproduction challenges and mitigate negative damping effects caused by high-frequency noise and actuator delays. A comprehensive evaluation of a 1/10-scale model under wind-only, wind-wave, and multi-hazard conditions demonstrates that the proposed Wind Load Simulator (WLS) achieves a force-tracking root mean square (RMSE) between 37.0% and 45.40% (0–20 Hz), with a first-mode relative error (RE) of 4.06% to 4.71%. These results substantiate the WLS's efficacy in reasonably replicating structural dynamic responses. The control framework also exhibits consistent stability and robustness across diverse scenarios, validating its suitability for RTHT in complex environments.