Dynamic responses of hybrid offshore renewable energy harvest system supported by a hybrid foundation

Abstract A hybrid offshore renewable energy harvest system (HOREHS) integrates multiple offshore renewable energy harvesting devices into a shared platform, offering a promising solution to enhance energy sustainability. Selecting a foundation with high performance and understanding system response are essential for ensuring the stable operation of the HOREHS. This paper examines a HOREHS supported by a hybrid foundation consisting of a steel plate and a monopile. The Walney wind farm was selected to conduct a comparative numerical investigation. FE models of HOREHS supported by monopile and hybrid foundation were established. The responses of the upper structure and the soil-foundation interactions under dynamic loading were analysed and compared. The results show that (1) The hybrid foundation significantly reduces the deflection at different levels and changes the trend of deflection variation with increasing cycles compared with monopile; (2) The presence of the steel plate alters the distribution of both the peak and residual lateral soil reaction forces and increases the shallow soil stress near the pile; (3) The presence of the steel plate reduces peak shear forces, shifts their maximum positions upward, and decreases the peak bending moment; (4) Cyclic loading alters the system natural frequency and damping ratio, and the presence of the steel plate modifies their evolution trends with increasing loading cycles. The results provide exploratory, mechanism-oriented insights under the investigated modelling assumptions, advancing engineers’ understanding of the underlying mechanisms.