Theoretical and Statistical Analysis of Ship Grounding Accidents

Abstract

Today, the ship kinetic energy and structural crushing resistance is not taken into account in any regulation concerned with the damaged state of a conventional ship (damage stability, oil outflow, etc.). However, the past few years of experience with high-speed craft (HSC) have clearly demonstrated that impact damage is indeed related to the kinetic energy and the strength of the ship. The present paper discusses various aspects related to rational design against grounding accidents. A relatively simple theory is reviewed for comparing the expected grounding damage of different ships, taking into account the structure, the displacement and the sailing velocity. It is shown that based on simple requirements of similitude, it is possible to scale certain types of grounding bottom damage. Then 130 grounding accidents are investigated. Attempts are first made at identifying the governing grounding scenarios and deriving a formula for the relation between the volume of deformed structure and the energy absorption (like the Minorsky formula). Moreover, the damage statistics is used to illustrate that the damage length divided by ship length is a function of the ship size. This observation is not in agreement with current regulations where bottom damage is proportional to ship length. The scaling theory is then used to explain that large ships experience longer relative damages than small ships. Major conclusions of the study are that the quality of future damage records should be improved, that various requirements and rules involving bottom damage may need to be revised, and that a method has been proposed for ranking ships according to their crashworthiness in grounding accidents. [S0892-7219(00)00103-5]