Bottom structural response prediction for ship-powered grounding over rock-type seabed obstructions

Abstract

This paper presents a simplified analytical method for predicting the resistance of ship bottom structures when a ship runs aground over rock-type seabed obstructions. During the powered grounding scenario, the structural damage caused by sharp seabed obstructions may lead to earlier penetration and serious consequences, such as compartment flooding, oil leakage and environmental pollution. Therefore, it is of great importance to rapidly and accurately analyse the response of a ship's bottom structure during powered grounding scenarios. A new simplified kinematically admissible analytical model is built to capture the dominant failure modes of the bottom transverse floor, which include plastic bending and membrane stretching, and the analytical expression of the resistance of the bottom floor is derived from a plastic mechanism analysis. The failure mechanisms of the bottom plating are also analyzed to provide insight into the main deformation mechanisms with reasonable predictive accuracy. The analytical prediction method is verified by numerical simulation using the code LS-DYNA. The simulation cases cover a wide range of indentations and semi-apex angles of the cone-shaped rocks. The results agree well, proving that the proposed analytical method can be used to predict the ship bottom structure crashworthiness during the structural design phase.