Assessment of dynamic substructuring of a wind turbine foundation applicable for aeroelastic simulations

Dynamic vibration response of a wind turbine structure is examined. Emphasis is put on the dynamic interaction between the foundation and the subsoil, since stiffness and energy dissipation of the substructure affect the dynamic response of the wind turbine. Based on a standard lumped-parameter model fitted to the frequency response of the ground, a surface foundation is implemented into the aeroelastic code FLEX5. In case of a horizontal stratum overlaying a homogeneous half-space and within the low frequency range, analyses show that a standard lumped-parametermodel provides an accurate prediction of the frequency dependent foundation stiffness—even for an embedded foundation with strong coupling between rocking and horizontal sliding. In this regard, the generalized stiffness matrix of the substructure is found to be in a reasonable agreement with the corresponding values based on a Guyan reduction scheme. In addition, experimental findings based on traditional and operational modal techniques on a Vestas V112-3.3 MW wind turbine installed on drained soil clearly indicate that the energy dissipation of the lowest eigenmode is described accurately in the aeroelastic simulation.