Seismic Response of Wind Turbines: Time Domain Simulations Including SSI

Abstract

This thesis presents the time-domain seismic response of a parked wind turbine with a skirted foundation exposed to soil-structure interaction. The wind turbine is discretized using the finite element program ABAQUS/CAE and the response in terms of displacements, accelerations, shear and moments along the tower height is computed using two comparative models.The fully integrated model and the simplified spring model demonstrated to be capableof simulating the seismic behaviour of a wind turbine tower accounting for SSI-effects; even with the relatively simple modeling techniques used. The models are restricted to the linearly elastic range and assume that the foundation is fully bounded to the soil during seismic excitation.The main contribution in this thesis is a parametric study which investigates changes in peak responses along the tower for different foundation geometries. The foundation radius and depth is independently varied and the same seismic excitation is applied to the spring model in all simulations. It is shown that an increase in the flexibility of the foundation gives larger peak responses along the tower for all the geometries considered. The corresponding fixed-base solution is shown to highly underestimate the seismic loads for certain geometries. This observation illustrates the importance of including the effects of soil-structure interaction for tall and slender structures.