Assessment of Residual Ultimate Hull Girder Strength of Damaged Ships

Abstract

The risk of ship collision and grounding has increased significantly in recent years as a result of the growing size and number of ships at sea. The potentially costly consequences of collision and grounding in the form of fatalities, property, and cargo, as well as environmental pollution in the form of oil spills, etc., are the main motivations for research on collision and grounding. From a structural evaluation standpoint, there is a great deal of uncertainty related to the residual strength of damaged ships considering various influential parameters, such as damage size, geometry and location, internal structural arrangement, material property, loading case, and sea weather. Therefore, it is important to clarify the residual hull girder strength of damaged ships by collision or grounding in order to ensure their safety. The present study undertook a deliberate finite element analysis to investigate the residual ultimate strength of damaged ship hull, where two damage models were assumed and compared. One model simulated actual damage resulting from an accident in the form of hole with adjacent plastic deformation, while the other applied simplified damage, considering unavailable measurement of the damage by removing the damaged part from the original ship hull. The comparison showed that the assessment of residual ultimate strength of a damaged ship based on the simplified damage model could produce a sufficiently accurate result and stay slightly safer, provided that a reasonable criterion of simplification was defined first. The studies showed that it is possible to accurately estimate the residual ultimate strength of a damaged ship without detailed measurement of the damage, and consequently facilitate decision-making regarding the ship salvage under emergency.