The objective of this study is to propose an analysis method of ultimate hull girder strength under combined bending and torsion. The hull girder is modelled by a series of thin-walled beam elements and the average stress-average strain relationship of plate and stiffened panel elements under axial loads considering the effect of shear stress is implemented in the beam elements. First, a torsional moment is applied to the beam model for a whole model within the elastic range. Then, the ultimate bending strength of cross-sections is calculated applying Smith's method to beam elements considering the warping and shear stresses. The proposed simplified method is applied to the progressive collapse tests of scale models under combined loads. On the other hand, nonlinear explicit finite element method (FEM) is adopted for the analysis of the test models. The effectiveness of the simplified method is discussed comparing with the results of experiments and FEM analysis.

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Kazuya Tatsumi (巽和也), a) Shinnosuke Noguchi (野口真之介), Akira Tatsumi (辰巳朗), Reiko Kuriyama (栗山怜子), and Kazuyoshi Nakabe (中部主敬)

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In Part 1 study, a time-domain collapse analysis method of ship hull girder was developed and named FE-Smith method. Hull girder was treated as elastoplastic beam model and Smith’s method was used for collapse analysis of cross sections. A concept of average stress-average plastic strain relationship was introduced so that nonlinear collapse behavior of members can be treated as pseudo strain-hardening/softening behavior. Fluid-structure interaction effects were considered. Uniform cross-section beam was assumed as a most fundamental study. In this Part 2, a container ship is taken as subject model. Not only FE-Smith analysis but also non-linear FE analyses using shell model for collapse parts are performed for comparison purpose. Two types of average stress-average strain curves are considered for FE-Smith analysis, i.e. obtained by Gordo-Soares formulae and by shell FEM. Applicability of FE-Smith method is examined comparing with more precise but time-consuming methods. Some parametric studies are also performed. Wave response will be reported in the next papers.