Considerations on dimensioning of garage decks

This work deals with the optimization of ro-ro/pax deck structures, focusing on the primary supporting beams in absence of pillars, as these decks have to be free, as far as possible, in order to facilitate the ship loading and unloading. Some typical ro-ro/pax grillage type decks have been analyzed, aiming at a numerical comparison between the primary supporting beam stress values obtained by the following techniques: Shade orthotropic plate bending theory, grillage analysis, finite-element method. As a result, it has been assessed the relative accuracy of such analysis techniques in deck transverse and girder dimensioning. Considering the necessity to minimize the deck structural weight and the web height, especially to improve the ship stability, it has been investigated the influence of each grillage parameter on deck framing behaviour, particularly in relation to the structural weight. These results have been achieved by a dedicated program, developed in MATLAB, that , thanks to nested iterative cycles, optimizes grillage parameters, the minimum structural weight being the objective. Finally, some general guidelines to obtain easily a grillage dimensioning quite close to the optimized one are suggested.