Equivalent plate method for calculating responses of multi-body floating structure with beam connectors

Abstract

This paper proposed an equivalent plate method to simply analyze multiple floating bodies connected with many beam structures. Proposed method assumes a complicated beam grillage structure as a simple plate by introducing equivalent bending thickness and equivalent distributed mass. With this scheme, we can get a approximate but simpler model to reduce Finite Element Method (FEM) computation. A multi-body floating solar platform with 400 floaters, 200 mooring lines and 100 connector beams were analyzed as a numerical example. Added mass, hydrodynamic damping and wave forces of floating bodies were formulated by Higher Order Boundary Element Method (HOBEM) and the elastic equations of beam or plate were formulated by FEM. By solving the combined equation, body motions, mooring lines tensions and section forces such as shear forces, bending moments and torsion moments in regular & irregular waves were obtained. Responses by wind or current were also investigated. All the results by the equivalent proposed method were compared with the original beam grillage analysis results to check efficiency and accuracy of the proposed method.