Assessment of the peak response of a 5MW HAWT under combined wind and seismic induced loads

Background and Objective: The rapid growth of the wind energy industry has brought the construction of large-scale wind turbines with the aim of increasing their performance and profits to areas characterized by high seismic hazard. Previous research demonstrated the seismic vulnerability of large-scale wind turbines when seismic and wind actions are considered simultaneously in the demand model. In this study, the response of the supporting structure of a land-based horizontal axis wind turbine under the combined effects induced by wind and earthquake is presented. Method: Using a decoupled approach, numerical simulations of the wind and seismic loads effects are performed separately using a specific model for the aerodynamic damping and then joined. Both simulations are done using free open-source software that are FAST simulating the aerodynamic response of the rotor and OpenSees simulating the dynamic behaviour of the tower. The fitted generalized extreme value distributions of the multi-hazard peak response in terms of base moment and shear, total drift, and top rotation are calculated for different seismic and wind load intensities by means of Monte Carlo simulations. The analyses are referred to the specific case study of a land-based wind generator. Results and Conclusion: The maximum demand is associated with the operational rated scenario and for high values of the peak ground acceleration, only the parked condition leads to larger values of the response if compared to others. The analyses showed that it is essential to consider the combined seismic and wind actions in the demand model to derive a complete multi-risk analysis of the land-based structures.