Experimental and numerical assessment of ultimate strength of a transversally loaded thin-walled deck structure

Many studies have been conducted to determine the ultimate strength of axially loaded ship structures at different levels of complexity, considering grillages, stiffened panels, transverse ring frames as well as complete hull blocks, aimed at assessing progressive collapse analysis of the whole hull girder, both analytically and numerically. However, little research has been conducted on the effects that transversal loads can have on relatively thin shell plating, particularly sensitive to buckling phenomena even for rather low loading thresholds. Moreover, the more and more frequent use of higher and higher strength steels makes ship structures slender and, consequently, likely to be even more sensitive to buckling phenomena. In the framework of a research project funded by Fincantieri R&D Department, a full-scale experimental test is performed on a structure simulating a deck portion characterized by a relatively thin plating, such as to induce an early local elastic buckling with a wide post-buckling range, before the ultimate load is reached. Nonlinear finite element analysis is carried out to design the experiment, considering both the nominal and the actual geometry of the structure as obtained by laser scanning the plating and by 3D reconstruction of the stiffeners. The effect of initial plating imperfection and of welding residual stresses on the numerical models has been considered as well, verifying their impact both, on the load end-shortening curve and on the ultimate strength of the panel.