Limit state design technology for a membrane type liquid natural gas cargo containment system under sloshing impacts

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Limit state design technology for a membrane type liquid natural gas cargo containment system under sloshing impacts

Paik, Jeom Kee

The aim of the present paper is to develop limit state design technology for cargo containment system structures of membrane type LNG (liquid natural gas) carriers, with the focus on sloshing impacts. The mechanical properties of plywood material making up the NO96 type LNG cargo containment insulation box structures are obtained from tensile coupon testing undertaken in the present study. The ultimate strength characteristics of the LNG cargo insulation box structure under quasi-static pressure action are investigated using ANSYS computer code. The dynamic failure behavior of the insulation box structure under sloshing impacts is examined using LS-DYNA3D computer code. Some important parameters, such as peak pressure and pressure duration time, which affect dynamic failure behavior, are varied in the S-DYNA3D computations. The limit state design criteria for the insulation box structures under sloshing impacts are developed. Results of the tests carried out are illustrated diagrammatically in various pictures. Problem areas to be resolved are discussed.The design procedure for the insulation box structures under dynamic pressure arising from sloshing should include the following major tasks: 1. Design value characterization of parameters of influence for dynamic pressure actions including peak pressure and duration time. 2. Cakculation of action effects. 3. Calculation of load carrying capacity. 4. Determination of safety factors.