Effect of scour on the structural response of an offshore wind turbine supported on tripod foundation

Abstract

A simplified scour model for tripod foundation taking into account both local scour and global scour is proposed in this paper. The model is incorporated into a three-dimensional (3D) finite element model for analysis of a full-scale offshore wind turbine founded on a tripod structure using realistic structural properties. Applicability of the 3D finite element model is validated using full-scale load test data. Four different scour conditions under two wave situations are examined for the ultimate limit state (ULS), serviceability limit state (SLS) and fatigue limit state (FLS). The results show that scour has a minor effect on the natural frequency of the tripod-supported wind turbine but can significantly increase the maximum cross-sectional von Mises stress of piles under the ULS and increase the deflection of piles within nearly 20 m below the original seabed under the SLS. As for the fatigue life of the tripod structure, it can also be reduced by the effect of scour. These findings provide insights which are useful for development of safe and economic design of offshore wind turbines supported by tripod foundations.