Strength analysis of superyacht superstructures with large openings

The superyacht manufacturing industry is currently facing big challenges, mainly related to the present economic crisis. Manufacturers are then competing on the ground of better and more aesthetic external and interior designs. This trend often leads to structural strength related issues, which can compromise the static or dynamic stability of superyacht hull. In several instances, the aforementioned fact is met, as in large openings and docks to recover tenders and the enlargement of windows to allow for better lighting of internal living spaces. So, for what the hull is concerned, large windows replaced small portholes on the yacht sides at mid length, rising non trivial problems about longitudinal strength. The same trend appeared on superstructures sides where traditional windows have been enlarged till to become glass doors extended from deck to deck allowing passengers to enjoy full sea landscapes. Despite the positive effect on the general design performance, this nice innovation implies serious structural problems. In fact in side areas where these doors are fitted the only structural elements are represented by very slender vertical stiffeners. The combined action of bending and compressive loads, together with the fact that superstructures are usually made by aluminium light alloy, can be the cause of buckling phenomena with severe consequences on structure and glass integrity. The same aspect has a negative influence on the bending efficiency of superstructures, meaning by that the level of cooperation of superstructures with hull strength. In this paper the contribution to steel hull strength of light alloy superstructures with large openings is studied by the finite element approach. The contribution of glazing windows to the primary response to global bending moment has been assessed as well.