Preliminary design of water breakers’ platings for container ships

This paper focuses on the design of water breakers’ platings for container ships, under impact lateral pressure due to green water loads, that in extreme sea conditions may damage goods, facilities and equipments on the exposed deck. The consequences of such loads may be mitigated through a combination of enhancing sea keeping analysis and structural design, that require direct calculation tools and a long time, as it is preliminary necessary to determine the ship motions relative to waves, then calculate the green water pressure and, finally, analyze the structural response under some acceptable criteria. In the study some formulas, useful to evaluate the maximum impact pressure due to green water loads, corresponding to the most severe sea state condition the ship may encounter during its lifetime, as function of the water height of the wave surface above the main deck at bow, are discussed and adopted. Subsequently, the ultimate strength check of platings is carried out splitting the process into two phases, namely the quasi-static loading step and the dynamic/impact one. Finally, some numerical analyses are carried out, varying the plating thickness and aspect ratio, as well as the initial impact velocity between the plate and the water surface.