Investigation on pile group foundations for offshore wind turbines

Pile group foundations with elevated piles will be one of the most popular foundation types for large offshore wind turbines in the next few decades in China. Design of wind turbine foundations is of great importance for offshore wind farms, with the following several key issues involved: ① analysis of mechanical behaviors and deformation mechanisms of foundations under complicated combined loading; ② determination approach of foundation stiffness; ③ dynamic response analysis of foundations subjected to vessel collisions. A unified static and dynamic analysis model for elevated pile group foundations for offshore wind turbines is presented to address these issues mentioned above. Comparison between the calculated results and the test ones show that the present model can give good prediction on both small and large lateral deflection of piles, as well as the deformation of pile group foundations subjected to multi-axis complex loads. By introducing reasonable damping coefficients, the proposed model is also effective for vibration analysis of pile group foundations subjected to dynamic loads such as vessel impact loads.