Ship Grounding over 'Rock' and 'Shoal'

摘要

The present paper focuses on the characteristics of bottom damage inrnrelation to different types of underwater obstructions, with emphasis onrnthe different deformation/failure modes for simplified analysis ofrninternal mechanics. The shape and size of the seabed obstruction is ofrncrucial importance with respect to the bottom damage. Most studies torndate are concerned with "rock" type, sharp obstruction. Very few arernrelated to grounding over blunt obstructions with large contact surfacernsuch as "shoal". The governing mechanics involved in ship groundingrnare described and compared for sharp rock and blunt shoal typernobstructions. When "rock" type obstruction is considered, plate tearingrnis a dominating failure mode. By contrast, denting rather than tearing isrnmore likely for bottom plating during grounding over blunt typernobstruction. A simple method for assessing the strength of the shiprnbottom structure grounding over obstructions with large contact surfacernis proposed. The primary deformation modes for the major bottomrnstructural members are: sliding deformation of longitudinal girders,rndenting and crushing of transverse members, indentation of bottomrnplating. By assembling these modes, the total resistance and energyrndissipation for a ship bottom can be obtained. The effect of friction isrnincluded as a factor to the resistance from plasticity. Comparisonsrnbetween simple methods for grounding over "rock" and "shoal" arernconducted. Coupled with the analysis of external dynamics, the methodrnmay be used whenever fast estimates for ship grounding is needed, e.g.rnin conjunction with crisis handling during emergency situations.