Seismic Analysis of Wind Turbines

An analytical model of an operating wind turbine to obtain the seismic response due to three base accelerations is presented. The model considers the flexibility of the blades in the flapping direction and the flexibility of the tower in bending and twisting. Blade aerodynamics and gyroscopic moments are included. A Vestas-V82 turbine is selected to demonstrate the methodology. The results show that only the first two tower modes in each direction (fore-aft and lateral) are mostly excited. It is found that the lateral motion of the wind turbine is more susceptible to experiencing large displacements since the aerodynamic effects are negligible in this direction. The stresses due to combined operational and seismic loads and due to extreme wind loads are less than the allowable stresses. The stresses calculated at the tower top section due to combined operational and seismic loads are larger than those due to extreme wind loads.