Settlement analysis of wind turbines

In this paper, the soil-foundation-structure interaction processes due to wind loading of a wind turbine founded on a circular raft are modelled by means of the FE method. The cyclic/dynamic response of the soil-foundation system is assumed to be fully described by a set of uncoupled viscous dampers and a nonlinear, inelastic macroelementwhich links the external loads and moment acting on the foundation with its displacements and rotation. The constitutive equations of the macroelement is formulated within the framework of the theory of strain hardening elastoplasticity.To account for cyclic loading effects, it is assumed that irreversible displacement increments may occur even for loading paths contained within a conveniently defined state boundary surface.The corresponding flow rule and hardening law can be formulated by means of a suitable mapping rule, establishing a correspondence between the current loading state and a uniquely defined image state on the state boundary surface. By means of the macroelement approach, it is possible to couple in a simple and efficient way the dynamic behaviour of the structure to the foundation movements. Settlement and rotation of the structure can then be predicted for any convenient number of cycles.