Numerical simulation in torsional strength of container ships with large hatch openings

Abstract

In numerical simulation pertaining to torsional strength of large container ships, various problems encountered in the initial stages of designing ships with large hatch openings are discussed.An actual ship of 38, 000 gross tonnage (container capacity : 1, 800 of 20' container) is adopted as the type ship, and the loading condition is based on the method proposed by Wilde.In the analysis, ships are treated as beam shells with variable cross-section, and a coupling effect between torsion and horizontal bending is also taken into account.As a result of this simulation, the following conclusions were obtained.(1) It was found that the most severe condition possibly occurs not in the middle part of ship but in the part about L/4 (L : ship length) apart from the bow.So the effect of variable cross-section should not be neglected in the analysis.(2) The effect of the double hull structure of ship side is considerably large to increase the torsional strength of container ships.(3) The application of the high tensile steel to the upper deck part gives little effect on the increase of torsional deformation in spite of the decrease of the plate thickness of that part.(4) In arranging the cross decks between hatch openings, provision of a large member in the middle part between the midship and the bow is very effective for the torsional strength.(5) The tier type structure is preferable to the knuckle type in various respect. In particular this type will assure a greater strength in the section toward the bow.