Ultimate strength of composite ships’ hull girders in the presence of composite superstructures

• Application of an extended formulation of the Coupled Beam Theory (CBT).
• Solution of the equilibrium equations by using nonlinear finite element method.
• Modelling the behaviour of composite panels by using progressive failure method.
• Modelling both hull and superstructure of the ship using beam elements.
• Modelling connections between beam elements using spring box elements.

An extended formulation of the Coupled Beam Theory (CBT) developed by the authors is employed in order to calculate the ultimate strength of composite ships taking into account of the effect of the superstructure. A nonlinear finite element method is applied for solving the equilibrium equations. Behaviour of the stiffened composite panels in tension and compression is modelled by using progressive failure method. Both hull and superstructure of the ship are modelled using beam elements. Connection between beam elements representing hull and superstructure is made using specially developed spring box elements. Accuracy of the extended method is demonstrated using an available experimental result and also the results of finite element analysis. Also, a set of composite ships having different lengths of superstructure is generated and analysed. Efficiency of the composite superstructure in contribution to the ultimate bending strength of the composite ships is finally evaluated.