Equivalent shell element for ship structural design

This paper presents an equivalent shell element for assessing the ship global and local static and vibration response in early design phases. The element provides a computationally economic tool for global analysis and the same mesh can be used in primary, secondary and tertiary level. The stiffened panel is considered as a three layer laminate element, where the first layer represents the plate, the second layer represents the stiffener web and the third layer represents the stiffener flange. The layers are described as 2D iso- and orthotropic materials, where elasticity matrices are found by applying the rule of mixtures. The element includes the in-plane, membrane-bending coupling, bending and additionally also shear stiffness, which follows the Reissner-Mindlin plate theory for anisotropic homogenous shells. The local plate bending response between the stiffeners is considered as well. The developed shell formulation has been implemented in commercial FE software FEMAP with NX Nastran and demonstrated through two case studies. Results are validated against 3D fine mesh quasi-static and vibration analyses and very good agreement is observed.