Abstract: The growing increase in length of super and megayachts has driven structural designers to adopt longitudinal layouts as a main point in the structural scantlings. By the way, the optimization of weights, strength, deformations and dynamic behaviour has to be evaluated separately for each new unit because of the particular and unique characteristics of each vessel. For this evaluation, especially for what the dynamic behaviour of ribbed plates is concerned, the use of numerical software based on the Finite Element Method is widely used since the early design stages in order to highlight benefits and weaknesses of a particular structural design. In this paper, two different structural layouts of megayacht decks have been studied and tested by using a FE software: the first one has been created with longitudinal and transversal stiffeners with the same cross section. In the second layout, transversal stiffeners are smaller in dimension but with lower span. The comparison has been carried out making reference to maximum strengths, deformations and dynamic behaviour. This work, starting from an initial lay out obtained by a CS rule approach, made it possible to converge to an optimal structural configuration, at least for what the starting geometries are concerned.
