Wave Induced Response of Shallow Draft Interconnected Pontoons

Abstract This paper presents the wave induced responses of shallow draft interconnected pontoons as investigated by the EU-funded project BAMBOO. The project aims to tackle the barriers for the implementation of a sustainable, large-scale offshore solar farm of 1km2/150 MW, that will act as a blueprint for the rollout of offshore solar projects in Europe. Special focus is attributed to the influence of wave frequent horizontal motions and axial interconnector loads on such installations. It is shown that the horizontal motions and axial connector loads are mainly related to the array length to wavelength aspect ratio. For stiff connectors, the axial connector loads RAOs vary between zero and a value that is twice the cross-sectional weight. The axial loading pattern for lower axial stiffness values is similar to the stiff solution, whereas dynamic amplification occurs in way of axial vibration modes. An analytical solution is derived for the axial natural frequencies and loading patterns. It is shown that in head waves the horizontal motions are in good agreement with results from diffraction theory and model tests. It is also concluded that expanding an array by adding more pontoons will significantly reduce the wave frequent horizontal motions, which leads to lower variations in mooring line tensions.