Feasibility study of a steel-UHPFRC hybrid tower for offshore wind turbines

A steel-ultra high performance fibre reinforced composites (steel-UHPFRC) hybrid tubular tower structure (>= 100m) is proposed and its feasibility to support an offshore wind turbine (OWT) with a 10 MW rotor is investigated in this paper. The hybrid tower combines a reinforced UHPFRC tube at the bottom and a steel tube at the top. Two numerical models are established to calculate the ultimate and fatigue loads for the hybrid tower and a standard steel tube tower as a reference. A simplified method is proposed to estimate the ultimate strength of the reinforced UHPFRC tube section, while a method based on the S-N curves is used to check its fatigue strength. It is found that the hybrid tower can satisfy design requirements and has a much longer fatigue life compared to the reference steel tower. Furthermore, the total material cost of the hybrid tower is found to be only 58% of that of the reference steel tower, while the masses of these two towers are kept close.