Hull-superstructure interaction in optimised passenger ships

Abstract

The paper investigates the interaction between the hull and the superstructure in optimised passenger ships when exposed to bending loads. The coupled beam theory was applied to extend the basic beam theory to take into account the vertical and shear stiffness between various decks. Optimisation of passenger ships with respect to weight and vertical centre of gravity (VCG) is carried out to create a set of Pareto-optimal solutions. The responses of these designs are compared in detail. The investigation shows that vertical and shear coupling between different decks significantly affect the response of the passenger ships and changes load-carrying mechanism of the hull girder. In the weight optimal design, the vertical bending moment is shared equally by the hull and the superstructure, while in the VCG optimal design, the neutral axis approaches bottom plating of the ship, considerably increasing the share of load carried by the superstructure. This means that the global response evaluation needs to include vertical and shear coupling along the length of the ship, and thus, the simplified two-dimensional section models are not adequate for the conceptual design of passenger ship structures.