Effect of the connection mode on the dynamic characteristics of the pile-wheel composite foundation for offshore wind turbines

This study elucidates the horizontal vibration response of the monopile-wheel composite foundation in terms of coupled arrangement. In this paper, the displayed expression of the lateral resistance and resisting moment provided by the rotating wheel and embedded pile are represented by using the linear elastic Winkler foundation model, in which the springs and dashpot coefficients are derived by Biot’s poroelastic theory and plane-strain model. The hydrodynamic force along the foundation shaft is obtained by the radiation wave theory. A connection degree coefficient is defined to describe the change of wheel action. Then, the dynamic governing equations for the vibrating pile based on the Timoshenko beam theory are re-established. Combined with foundation bottom boundary condition, the frequency domain analytical solutions for the horizontal and rocking impedances at the head of the composite foundation are obtained. A comparison with some existing results is carried out to verify the correctness and reasonableness of the proposed model. Finally, systematic studies are conducted to analyze the horizontal vibration characteristics of the innovative foundation under different pile-wheel connection mode. The results from these calculation examples show that the pile-wheel composite foundation with decoupled or coupled arrangement has its own advantages in resisting deformation.