Ultimate strength analysis of a SWATH ship subjected to transverse loads

摘要

When SWATH (Small Waterplane Area Twin Hull) ship hulls are exposed to horizontal extreme wave loads, the transverse ultimate strength is critical due to large stress concentrations in the narrow struts and haunches. In this paper, an experiment has been performed to examine the ultimate strength of a one-eighth scaled SWATH ship model subjected to transverse loads. The experimental results are compared with finite element simulations. The structural model, scaled from an actual SWATH ship, is designed with scaling laws and linear static analyses performed by the MSC.Nastran finite element solver. The procedure to design and manufacture the complex structural model is given. The actual ship and its scaled model are analysed numerically to achieve the consistency of the maximum stress and the stress distribution in their corresponding finite element models. The experimentally obtained force-displacement response and shape of the deformation show good agreement with the simulations performed by the implicit MSC.Marc nonlinear finite element solver. The maximum stresses are mainly concentrated around the hull haunches, and the stress distributions at the ship ultimate collapse are presented. The ultimate strength of the actual SWATH ship is evaluated according to scaling laws, and the ship safety margin is analysed. Moreover, the effects of hydrodynamic wave pressure distributions on the ship ultimate strength are investigated.