Hinge-Spring-Friction Device optimized for the protection of wind turbines from combined wind-earthquake loads

The growing global demand for sustainable energy has accelerated wind power development, with increasingly tall turbines. However, installing these structures in seismic areas raises new engineering challenges related to structural safety under complex dynamic loads. This study introduces an innovative passive control system, the Hinge-Spring-Friction Device (HSFD), designed to mitigate wind- and earthquake-induced stresses in horizontal axis wind turbines (HAWTs). Positioned at the tower base, the HSFD consists of multiple devices connected in parallel and was designed using a nonlinear multi-objective optimization methodology, with the reduction of base moment and top displacement as performance indicators. The NREL 5-MW turbine, widely used in literature, was adopted as a case study and modeled in a FEM environment in Simulink®. Numerical analyses considered realistic combined actions, consisting of ordinary wind loads and seismic inputs consistent with the NTC2018 spectrum. Two approaches were investigated: (i) an uncoupled method, where responses to wind and seismic actions are superimposed linearly, and (ii) a coupled method, where both hazards act simultaneously. The uncoupled rule provided the most favorable outcomes for multi-risk scenarios. Preliminary results show that the HSFD reduces the maximum base moment by up to 52% compared to the uncontrolled configuration and accelerates the dissipation of post-seismic vibrations, suggesting benefits for the fatigue life of the structure. The study offers an innovative contribution to seismic engineering applied to renewable energy, providing a practical and replicable solution that can be easily integrated into the design process of modern wind turbines.