A substructure method for seismic responses of offshore wind turbine considering nonlinear pile-soil dynamic interaction

The increasing number of wind turbines in areas of active seismicity has attracted scientific interest to evaluate the seismic responses of offshore wind turbine (OWT). The pile-soil dynamic interaction can have significant influence on the seismic responses of OWT. This research aims at investigating the seismic responses of a 5 MW OWT considering nonlinear pile-soil dynamic interaction. The pile is assumed to be rest on the rigid bedrock. The soil nonlinearity is accounted for approximately using an inhomogeneous boundary zone around the pile and a homogeneous zone outside the boundary zone. For simplification purpose, the dynamic analysis of the OWT is divided into two stages. In the first stage, the dynamic resistance factor of soil layer with radially inhomogeneous boundary zone is obtained by using transfer matrix method. In the second stage, a substructure model for dynamic responses of OWT including structure-pile-soil interaction is proposed. A three-dimensional (3D) finite element model (FEM) in Abaqus is used to verify the proposed method. Numerical results show that the proposed model agrees well with the 3D FEM. Finally, the effects of pile-soil interaction on the seismic responses of a 5 MW OWT are investigated.