Ship and Ice Collision Modeling and Strength Evaluation of LNG Ship Structure

A collision model has been developed for nonlinear dynamic finite element analysis on an LNG ship and a crushable ice using commercial code DYTRAN. In this modeling, a global LNG ship model has been employed as a deformable body which follows the elastic-plastic constitutive model, and an ice floe has been modeled as a crushable body including material failure. The deformation and failure of the ship structure and the ice as well as the contact force at the contact area between the ship and the ice have been determined from collision simulations. For most ship-ice interaction scenarios, the ice load applied to the ship can be considered as a quasi-static load. The loading capacity of LNG ship hull structure has been investigated applying static ice loads to a local model, which is a whole compartment of a cargo tank in the ship structure including five components such as the side shell plating, longitudinal stiffeners, stringers, web frames, and inner hull. For each ship and ice interaction scenario, loading cases at five varying locations in the local model have been investigated. Numerical results show that different loading location cases cause the structure failure at different components. FE results also indicate that large plastic deformation and buckling failure modes are found in different components of the hull structure. Finally, acceptance criteria and the complete procedure have been developed for the strength evaluation of hull structure in LNG carriers under ice loads.