Study of the Fairlead Connections of a Prestressed Concrete Spar Platform Supporting a 10 MW Floating Offshore Wind Turbine

This study aimed to design the fairlead steel–concrete connections and investigated the structural service life due to concrete fatigue of a prestressed concrete spar supporting a 10 MW floating offshore wind turbine. The numerical study using finite element code COM3 was performed to investigate the nonlinear behavior of the concrete structure induced by coupled dynamic motions of the wind turbine under operation. Tower base forces and mooring tensions were applied to the finite element model investigating stress–strain localization. Two types of fairlead connections were designed for the proposed prestressed concrete spar and implemented in the finite element model that installed tower connections and applied prestressing forces obtained from the previous study. Finally, the fatigue life estimation due to concrete fatigue was investigated under the model code restriction compared to the simulation analysis. The analytical results showed that the designed fairlead connections could withstand large tensile forces transfer from mooring lines to the spar concrete. In both types, the fatigue life of concrete under tension was longer than the restriction; however, for the concrete under compression, the Plate-Plate model showed a possibility of fatigue failure. The study highlights the need to improve the fatigue design of the fairlead steel–concrete connections in the next design phase.