Slenderness ratio distribution and load-shortening behaviors of stiffened panels

Abstract This paper evaluates the distributions of three slenderness ratios of the plates, the stiffeners, and the stiffened panels, and presents a comparison of the load-shortening behaviors of the stiffened panels. The slenderness ratios, which represent the geometry and material properties of the stiffened panels, are obtained from deck and bottom platings of the midship area of 163 vessels, including 59 tankers, 46 bulkers, 28 product carriers, 15 container carriers, and 12 miscellaneous ships. Under the assumption that each slenderness ratio closely follows a normal distribution, average and upper/lower bound slenderness ratios are derived based on mean and mean plus/minus two times standard deviations. In order to compare the load-shortening capacities of the stiffened panels from simplified formulas of common structural rule (CSR) with those derived from a nonlinear FEA, a new parameter of relative average strain energy is introduced. It is concluded that the CSR formulas may be developed based on the very small initial imperfections of weld-induced initial deflection and residual stress.