Ship-cargo Interaction for Vessels Carrying Large Wind Turbine Monopiles

Abstract

The increasing demand for decarbonisation to achieve the green transition leads to a higher required capacity for all types of renewable energy farms, including offshore wind. Due to the large required spacing between turbines to maximise their efficiency, their individual size is constantly increasing. A direct consequence for heavy lift and transport ships is that a decreasing number of monopiles can be transported in the cargo hold due to space restrictions. In fact, in many cases monopiles do not fit in the cargo hold at all and are attached to the main deck instead. When lashed on the deck, the monopiles span across most of the length of the ship, and their bending stiffness is significant, as they are designed to withstand harsh ocean conditions. This raises the concern that, depending on the lashing method, the monopiles can have significant effects on the dynamic behaviour of the ship’s hull. In this investigation, the ship’s hull and the monopiles are modelled as a coupled system with appropriate boundary conditions, and the effects of the number of monopiles and lashing method on the vertical bending responses of the vessel are quantified.