A Structural Capacity Evaluation for Corrugated Membrane Structure of LNG Cargo Containment System

Corrugated membrane structure is adopted as 1^st barrier of membrane type LNG cargo containment system of LNG carrier to reduce thermal stress caused by cryogenic temperature of LNG. The corrugated structure, however, can lead to buckling and large deformation followed by plastic strain at a local area of the 1^st barrier under sloshing load. Therefore in order to evaluate structural capacity of the corrugated membrane, structural response against various environmental loading such as hull deformation, sloshing load as well as thermal loading should be investigated. In this study, failure criteria for corrugated membrane is proposed based on rupture strain of the material considering the objective of the 1^st barrier of LNG cargo containment system with respect to functionality. And the structural responses of corrugated membrane, for each environmental loading, are carefully evaluated. To evaluate structural response under sloshing load and thermal loading, a series of finite element analysis is carried out and plastic strains for each loadings condition are estimated. In addition, to investigate the effect of plastic strain developed during metal forming process for corrugated membrane on structural response, plastic strain on corrugated membrane developed by metal forming is measured through real manufacturing process. By comparing accumulated plastic strain due to thermal, sloshing load as well as material forming to material rupture strain obtained from material tensile test, structural capacity of the corrugated membrane structure of LNG cargo containment system is evaluated.