Strength of a Container Ship in Extreme Waves Obtained by Nonlinear Hydroelastoplasticity Dynamic Analysis and Finite Element Modeling

Extreme waves have caused a lot of ship accidents and casualties. In this paper, a two-dimensional (2D) hydroelastoplasticity method is proposed to study the nonlinear dynamic responses of a container ship in extreme waves. On the one hand, the traditional ultimate strength evaluation is mainly performed using a quasi-static assumption without considering the dynamic wave effect. On the other hand, the dynamic response of a ship induced by a wave is studied based on hydroelasticity theory, which means the ship structural response to large waves is linear. Therefore, a 2D hydroelastoplasticity method that accounts for the coupling between the time-domain wave and ship beam for nonlinear vertical bending moment (VBM) is proposed. In addition, a nonlinear dynamic finite element method (FEM) is also applied for the nonlinear VBM of ship beam. The computational results of the FEM, including the nonlinear VBM and deformational angle, are compared with the results of the 2D hydroelastoplasticity and hydroelasticity. A number of numerical extreme wave models are selected for computations of hydroelasticity-plasticity, hydroelasticity, and FEM. A difference is observed between the nonlinear VBM calculated by FEM and linear VBM calculated by hydroelasticity, and conclusions are drawn.