Impact of padeye depth of suction caisson anchors and clump weights on floating offshore wind turbines

Little analytical study has been conducted to elucidate the interactions among the suction caisson anchors, mooring chains, and the platforms of floating offshore wind turbines (FOWTs). In this paper, an analytical approach will be developed to clarify the effect of the padeye depth of suction caisson anchors in sands and the mooring clump weight on the response of the comprehensive system of the FOWT. First, to predict the tensile behavior of suction caisson anchors in sand, the equations relevant to the vertical and lateral yield resistances, the bearing capacity, and pullout were presented. Second, considering the characteristics of the moorings dependent on the horizontal load applied to FOWTs and the clump weight, an analytical approach was proposed regarding the relationships among the mooring chain configuration, the caisson padeye depth, the tensile load induced at the caisson padeye, the magnitude and location of the clump weight, and the horizontal load at the spar fairlead. Last, the relationships among the displacement, the tensile capacity, and pullout of the suction caisson anchor in sand subjected to the inclined tensile loads induced at the caisson padeye were revealed when the designed horizontal load is exerted on the spar fairlead.