Structural Response of Cargo Containment Systems in LNG Carriers under Ice Loads

Abstract

Ship-ice interaction scenarios have been investigated for possible operation routes in Arctic areas and six scenarios were selected to study the structural response of Cargo Containment Systems (CCS) in both membrane and spherical types of LNG ships. For selected ship-ice interaction scenarios, ice loads and loading areas in the hull structure were determined based on the energy theory. For membrane-type LNG carriers, CCS is made of very different materials such as plywood, foam and mastic. A local FE model including the partial hull structure with one panel of individual CCS has been developed for analysis purposes. For Moss-type LNG carriers, the tank system consists of a spherical tank and a cylindrical supporting skirt structure. A local FE model including the partial hull structure with the skirt structure has also been developed for structural analysis. One critical loading location, where the ice load is applied to cause the maximum deflection of inner hull, is determined in the side shell for investigating the deformation behavior of CCS for all selected scenarios. Linear buckling analysis was performed to investigate the stability of hull structure. Nonlinear static FE analyses were conducted to obtain stress and displacement in membrane-type CCS and skirt structure, respectively. Critical locations where the maximum stresses occur in CCS were identified in both membrane and Moss types of LNG carriers. The strength of LNG carriers under the design ice load was evaluated based on FE results and assessment criteria. Finally, structural analysis procedures have been developed for assessing the strength of cargo containment systems in ice class LNG carriers.