Abstract
In recent years, container ships and lumber carriers with two row hatches have been constructed. In these ships, their effective deck areas are so small that some structural problems in their strength have often arised. Torsional strength of these ships are also insufficient, the concerning studies have been carried out by many authors.^<3),4),5)> The effectiveness of center decks in longitudinal bending and the strength of a hold having a center pillar between center deck and inner bottom at the midspan of hold are more important in design of ships. In this paper, they were studied and following result were obtained. A theoretical calculation method of effectiveness of center deck in longitudinal bending was indicated and normal stress distribution in deck model with two row hatches (the deck with one hatch opening in both ends, the other deck without hatch opening) was carried out by the photoelastic test under the unifom tensile load. Comparisons between observations and theories resulted in good agreement. In practical ships, the effectiveness of the center deck of the ship with two hatch openings in No. 1 hold is increased in 2% compared with it of the ship with one hatch opening. The caluclations of one hold strength were carried out on the various severe load conditions and the influnces of the center pillar on strength became apparent. In the transverse members at the midspan of the hold, the bending moment in bilge corner is large and it is decreased in about 10 per cent by center pillar. The bending moment distribution in center deck due to deck load is changed considerably by the bending moment due to reaction from the center pillar.
