Peak response of hawts to wind and seismic actions

The spread of the wind energy industry has brought to the construction of wind farms also in areas prone to high seismic activity. This, combined with the increase in size and mass of turbines has made the seismic-resistant design of support structures a key issue. This study presents the results of the application of a probabilistic approach to the assessment of a 5-MW, land-based HAWT support structure, subjected to the combined actions of wind and earthquake. A decoupling approach was used, consisting of the aerodynamic analysis of the rotor blades model and subsequent dynamic FEM analyses of the supporting structure including aerodynamic damping. The aerodynamic forces acting on the rotor were evaluated through the FAST aerodynamic simulator. Alongwind and crosswind aerodynamic damping was evaluated using an available closed-form approach. The wind action was applied at the top of the tower FEM model in terms of a set of thrust time histories corresponding to different working conditions: parked (3 m/s), cut-in (3 m/s), rated (11.4 m/s) and cut-out (25 m/s). Seismic actions were applied as acceleration boundary condition at the tower base, using a set of artificial accelerograms, whose mean response spectrum is consistent with the EC8 elastic spectrum for soil type C. Finally, the multi-hazard peak response parameters were obtained from Monte Carlo simulations of the tower subjected to different wind and seismic loads scenario.