Stress distribution of a box girder with hatch openings

Longitudinal bending moments induce not only longitudinal stresses in the ship hull girder but also transverse stresses in the hull section, for a bulk carrier in particular Oil tankers have been known to have relative vertical deflections between the side shell plating and the longitudinal bulkhead plating, which cause bending stresses in the transverse webs. For the bulk carriers, the longitudinal bending moments yield the nonuniform longitudinal stresses in the upper deck part because of the hatch openings and its particular loading. If a ship has no cross decks between hatches, the upper deck part will be bent outward under hogging moments or inward under sagging moments. The cross deck plating prevents for the upper deck from being bent, but causes the transverse stresses in the upper deck part connected to the cross decks In this paper, qualitative studies are performed to verify that the upper deck is bent outward or inward horizontally by using "stress function" applied to a deck plate, a side plate and a bottom plate of a box girder. And stress calculations are made by FEM for various bending moments in the connecting area between the upper deck plate and the cross deck plate. The transverse stresses are found to be higher than the longitudinal stresses at the hatch corners depending on the ballast loading condition.