STRENGTH ASSESSMENT ON SUPPORT SYSTEM OF LNG INDEPENDENT TYPE B TANK UNDER SLOSHING LOADS

摘要

A Liquefied Natural Gas (LNG) tank usually contains cryogenic cargo with free liquid surface and requires high level of safety. In this study, a two-step procedure has been developed for strength evaluation of support structures in LNG carriers with independent type B tank, which is partly loaded and under sloshing impact. First, an integral model containing a rigid tank and connectors is used to investigate the displacement and force response of supports in time domain. Then, several local models are used for the fine mesh stress analyses of support structures. The nodal displacements of connectors are extracted from integral model and applied to the local model as boundary conditions. The finite element method has been implemented in both steps. The arbitrary Lagrangian-Eulerian technique is applied for kinematical descriptions of the fluid domain in the direct sloshing analysis of type B tank in first step. The present numerical results are compared with previous experimental values, results of other numerical method and analytical solutions, which validates the reliability and accuracy of this method. It is noted that the proposed procedure can be utilized for strength analysis of other types of LNG tanks and helps to optimize their structural design straightforwardly.