Experimental Investigation on Aerodynamic‐Seismic Coupled Responses of the IEA 15 MW Monopile Offshore Wind Turbine

ABSTRACT Offshore wind turbines (OWTs) may experience earthquakes during operation; however, their structural dynamic behavior under aerodynamic‐seismic coupling remains insufficiently understood, particularly with rotating blades. This study conducts a 1/70‐scale aerodynamic‐seismic coupled shaking‐table test on the IEA 15 MW monopile‐based OWT, presenting the first‐ever experimental analysis of tower‐top internal force response under joint aerodynamic and seismic loading. Two primary scenarios, earthquake‐only (E‐only) and earthquake‐wind (EW), are compared to elucidate how aerodynamic damping and loading influence the coupled structural response. Structural responses are extracted within the 90 % effective strong‐motion window. Comparisons with code‐recommended load combinations are performed for both acceleration and force responses. For nacelle acceleration, a variability‐informed combination coefficient, defined as the mean value plus one standard deviation, is close to the code value of . Nonetheless, for the tower‐top internal force, the corresponding combination coefficient is near the code value of 1.0, suggesting that the coupled EW response may be reasonably approximated by linear superposition under the tested conditions. Additionally, the definition of the seismic dynamic amplification factor () is adopted and extended. Under E‐only conditions, the acceleration‐based retains its conventional interpretation as a measure of seismic dynamic amplification, being the acceleration ratio of the output to the input. Under EW conditions, a nominal acceleration‐based has to be introduced to quantify the seismic dynamic amplification in the presence of steady aerodynamic loading. The results show that this is consistently lower than its E‐only counterpart , highlighting the attenuation of earthquake‐induced dynamic amplification due to aerodynamic effects and associated EW coupling. All these findings provide new physical insight into the aerodynamic‐seismic coupling behavior applicable to both offshore and onshore wind turbines, as ocean waves and currents are not involved in this study. More importantly, they also provide experimental evidence that supports multi‐hazard analysis and load combinations at the design stage for wind turbines in seismic regions.