Offshore wind energy has become one of the fastest growing sustainable energies. The bearing performances of foundation structures of offshore wind turbines (OWTs) are closely associated with structural security. In this paper, taking into account the coupling effects of wind, wave and current on the OWTs, the three-dimensional non-linear finite element analysis coupled with the BP neutral network model are applied on prediction of the static bearing performances of OWT monopile foundations. Meanwhile, the normal operating condition and the braked condition of OWT structures are considered in the coupled model. The non-linear finite element analyses coupled with the probabilistic statistical methodology can provide reference for the online monitoring of the structural safety state of the OWT, and can be potentially applied to subsequent analyses including the failure risk analysis, economic evaluation, and structural optimization.
Offshore wind energy development has been the focus of marine engineers and scientists during the past decades. The proportion of offshore wind energy in the total renewable energy is also growing rapidly after the years of development. Offshore wind is expected to grow from 6GW in 2019 to nearly 80GW in 2024, bringing its market share in global new installations from 10% in 2019 to 20% by 2024 (GWEC, 2019). However, compared to the onshore wind energy development, the cost of offshore wind energy development is much higher. It is mainly due to the large cost of the foundation structure, which may account for 20%~30% of the total cost of an offshore wind turbine (OWT) (Yang et al., 2018). Monopiles are currently the most widely used foundation types for offshore wind turbines (OWTs), due to its advantages of small self-weight, simple manufacturing and mature installation technology (Alamo et al, 2018). The monopile is embedded in subsea soil to resist the moment load resulted from the wind, current and wave. As the demand for wind energy increases rapidly in recent years, the OWTs are moving to deeper waters, which means thicker and longer monopiles are needed to withstand greater environmental loads. Because of the high investment and large cost along with foundation structure, it is necessary to do some researches on the bearing capacities of OWT monopile foundations.
