Experimental investigation of seismic responses in monopile-supported wind turbines considering operational history using integrated wind tunnel and shaking table testing

Monopile-supported wind turbines (MWTs) are subjected to wind loads, along with 1P and 3P loads during long-term operation, which can alter the surrounding soil properties and the dynamic characteristics of the structure. These changes affect the seismic response of the system when an earthquake occurs. To quantitatively assess the influence, a 1:100 scale model of a 5 MW MWT was tested using an integrated wind-seismic testing platform that combines wind tunnel and shaking table capabilities. The lateral cyclic loading process was simulated using a mass-gear balance system to reproduce different operational histories. The experimental design captures seismic responses under varying conditions, including the number of cycles and amplitude of lateral cyclic loads during long-term operation, as well as the operational state of the turbine and the seismic intensity during the earthquake. Results indicate that operational history has a significant impact on seismic performance, leading to reduced nacelle displacement and tower rotation angles, but increased nacelle acceleration, tower bending moments, and amplification of the whiplash effect. These findings indicate that wind turbines become more vulnerable to seismic damage after prolonged operation, highlighting the need to account for operational history in seismic safety assessments and providing valuable experimental data for future improvements.