A simplified method to analyse the strength of double hulled structures in collision (2nd Report)

The strength of ship structures in collision is an important matter in terms of saving life, preventing pollution and from an economic point of view, especially in the case of hazardous cargo carriers, oil tankers and so on.The authors investigated the strength of double hulled structures in collision, which were typical of the side structures of hazardous cargo carriers. In the former paper, the types of collisions were classified into five groups. Two types among those five groups were examined ; one was the type where a stem collided against the ship's side, and the other was where a bulbous bow collided against it.In this paper, another type in which a bulbous bow collided against the bilge part of a ship was examined. Such a type of collision is likely to occur between fully loaded ships, which means that the two ships have the greatest kinetic energy before collision. These three types are considered as the most critical ones among those five groups. Static destruction tests were carried out using simplified and detailed large scale models of a bilge structure representative of those used in double hulled ships, where the bow model was assumed to be rigid.A simplified method to analyse the damage of bilge structures in collision was developed on the basis of the results from the experiments. The basic concept of it is similar to the former paper ; a bilge structure is considered to consist of two main structural members, that is an outer shell which acts as a membrane and a trans web which supports such a membrane.The analysis method was examined by comparing the calculated values with the experimental ones. From these, a good correlation emerged.