Steel panels, stiffened with ribs of different lay-out patterns, are very common in mobile structures, such as ships, spacecrafts, etc., The stiffener lay-out should be consistent with the nature of forces to be resisted. In this paper, different types of stiffened panels are analysed for their response to impact force, with the objective of assessing their relative merits. The aim is to arrive at an optimal lay-out of the stiffeners for a given panel mass. To achieve this objective, the response of an equivalent solid (unstiffened) plate is compared with the responses of stiffened panels. The types of stiffened panels considered are Orthogonally-Stiffened Panel (OSP), Rhombic-Stiffened Panel (RSP) and Diagonally-stiffened panels (DSP) of three different types. Their impact responses are predicted by transient dynamic analyses, using the finite element software, 'OSTA'. Some of these results are verified by carrying out free-fall impact experiments. The correlation is observed to be good. The studies on the relative merits of the different types of panels lead to the conclusion that the DSP Type-II is the most efficient panel for maximum impact resistance.
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