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

Abstract

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.

Lightweight Structural Concepts in Bearing Quasi-Static Ice Hull Interaction Loads

“…The interaction schematic and the loading curve in Figure 1b show a large peak corresponding to the flexural failure of ice while the smaller high-pressure peaks correspond to spalling, fracturing and extrusion of material [26]. The ice flexural failure mechanism can be assumed as quasi-static based on FSICR recommendations for direct calculations and previous literature studies [27,28].…”

“…flexural failure mechanism can be assumed as quasi-static based on FSICR recommendations for direct calculations and previous literature studies [27,28]. In isolation, the quasi-static assumption may not completely represent ice-hull interactions, but by also considering dynamic loading (planned for future work), we may capture the ice loading reasonably.…”

Shared-Energy Prediction Model for Ship-Ice Interactions

“…Both a positive and a negative of FEA models is that more details are required to model the interaction [22], thus also producing a more detailed response. If a very specific interaction is being modelled, and the details of the interaction are known, this can be a more accurate approach, since fewer simplifying assumptions are required to model the interaction [27]. FEA models are often used to model the coupling effect of two interacting bodies, with either ice or structural interactions, since both responses and effects of the interaction can be modelled simultaneously [28,29,30,31].…”

Efficient response modelling for performance characterisation and risk assessment of ship-iceberg collisions

“…Although several geometries have been considered in the literature (e.g. [38,[50][51][52]), there is a need for more research into their categories and probabilistic characterisation. The probabilistic characteristics of all the input random variables considered for the ship-iceberg collision study are presented in Table 3.…”