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Load carrying capacity is of importance in the evaluation of the stability of submarine pressure shell structure. During the buckling process of cylindrical shell under hydrostatic pressure, the total potential energy of ring-stiffened cylindrical shell can be divided into constant component, linear component and square nonlinear component. Based on the derivations of buckling loads of smooth cylindrical shell and ring-stiffened cylindrical shell, the reduced stiffness method (RSM) is applied to assess the role of different stiffness reductions in the evaluation of stable load carrying capacity of cylindrical shell. This study shows: (1) the circumferential membrane stiffness is influence the stability of cylindrical shell largest; (2) the ring ribs have a significant effect on the overall stability of ring-stiffened cylindrical shells under hydrostatic pressure; (3) the circumferential buckling wave number of ring-stiffened cylindrical shell may not depend on the membrane stiffness reduction of shell, but it increases with the bending stiffness reduction of ring ribs. [ABSTRACT FROM AUTHOR]

The aim of this paper is to quantitatively evaluate the extent of collapse of a bulk carrier when the ship is subjected to extreme wave loads. A hydro-elastoplasticity theory, which was proposed by the present authors and takes into account the interaction between the large elasto-plastic deformation and the wave load evaluation, is applied to the ship’s structure with the assumption that a plastic hinge is formed in the midship region when the hull girder collapses in extreme wave conditions. The dynamic response of the hinge can be expressed by the relationship between the vertical bending moment and the curvature, which are obtained using nonlinear Finite Element Analysis (FEA). A comparative correct moment–curvature curve and a reasonable load evaluation are necessary for prediction of the severity of the collapse for the actual ship. A bulk carrier hull model with one frame space is constructed and analysed using an arc-length control method (Riks method). The geometric nonlinearity resulting from large deformations and the material nonlinearity are taken into account. The presence of an initial imperfection is considered using the consistent imperfection mode method in the FEA. A prediction of the extent of collapse for a bulk carrier subjected to an extreme wave load is carried out using the hydro-elastoplasticity approach. This analysis clarifies the extent to which the hull girder may collapse in extreme wave conditions at an exceedance probability of 1/1000 in several short-term sea states. [ABSTRACT FROM AUTHOR]