In this paper, a series of nonlinear FEM analyses are firstly performed on stiffened panels varying number/type/size of stiffeners as well as slenderness ratio and aspect ratio of local panels. Two length and width of local panel are kept the same in one series. The calculated ultimate strength is compared with those by existing methods. On the basis of comparison, appropriate method is recommended to evaluate ultimate strength of stiffened panels subjected to longitudinal thrust.
A ship hull girder is subjected to longitudinal bending owing to distributed self-weight, buoyancy forces as well as wave forces and inertia forces, which produces thrust load acting on deck or bottom plating. Longitudinal stiffeners are provided on deck and bottom plating to prevent buckling between longitudinal girders and floors/transverse frames/bulkheads. Buckling/plastic collapse of deck or bottom plating as a stiffened panel results in overall collapse of a ship hull girder. Because of this, many research works have been performed up to now to clarify buckling/plastic collapse behaviour and strength of stiffened panels subjected to various loads. Among many research works, Harada (2004) and Harada et al. (2004, 2005a, 2005b) proposed formulas to evaluate ultimate strength of stiffened panels subjected to longitudinal thrust. In Harada's formulas, a continuous stiffened panel is replaced by a stiffener with attached plating. This model is fundamentally for continuous stiffened panel with many stiffeners, which may corresponds to deck plating of VLCC. However, number of stiffeners depends on types of ships. For example, two stiffeners are provided on bottom and inner bottom plating between longitudinal girders in case of Handy-size bulk carriers. In the present paper, a series of nonlinear FEM analyses are firstly performed on stiffened panels varying types and sizes of stiffeners as well as slenderness ratio and aspect ratio of local panels.
