Dynamic response of offshore wind turbine monopile foundation under wind-wave loads

Physical experiments provide the best representation of foundation behaviour in any environmental conditions offshore, however they are very costly, especially since the on-site conditions vary. Hence it is not a cost-effective approach. On the other hand, numerical modelling is relatively cheaper, but requires long computation time and a high level of expertise to perform a successful numerical calculation. The main objective of this paper is to develop a simple and fast response analysis that requires less computational time and expertise. First, an analytical model is developed to study the dynamic behaviour of the pile by extending the beam on an elastic foundation. Second, the analytical results are verified by using the finite element software Abaqus. Finally, a parametric study is performed with the established numerical calculation model to investigate the modal shapes of the pile model, limit states of the OWT and pile capacity for different loading conditions and aspect ratios. The proposed analytical model demonstrated a degree of error less than 10%, indicating great reliability and practical application. The parametric results indicate that the OWT is more likely to fail by yielding than buckling and the soil resistance at the pile periphery is highly affected by the aspect ratio.