Fatigue Strength Assessment of Semi-Submersible Floating Wind Turbine Foundation under Turbulent Wind

Under the complex marine environment load and the role of the upper wind turbine load, deep sea floating wind turbine support structure would suffer fatigue damage, which often endangers the safety of the wind turbine system. This paper chose the "5 MW baseline" wind turbine model which published by the US National Renewable Energy Laboratory (NREL) as the design basis. The paper uses the OC4-DeepC wind semi-submersible offshore wind turbine model for the verification of offshore floating wind turbines. According to the characteristics of stress and the distribution of stress, the paper selects seven key parts which are prone to fatigue damage are screened, respectively established local finite element models and carried out grid encryption. Based on the SESAM hydrodynamic analysis software and FAST wind motor dynamic load calculation procedure, the fatigue damage of the target node under the action of wind turbine load is studied. The results show that the structural fatigue damage occurs mainly at the horizontal connection of the upper part of the neutral column and the diagonal connection of the lower part of the neutral column. The fatigue damage degree of the crown and the saddle point is relatively large at the connecting rod position