10. A Study on the Collapse of ship Structure in Collision with Bridge Piers :

This paper discusses the collision between somewhat small ships and bridge piers through static failure tests of ship structure models. First, there were presented the results of static tests on the fracture of simplified models of a ship side and a ship bow, which were performed for the purpose of examining the extent of fracture developed in a ship hull in collision with a bridge pier and estimating the amount of a collision force. The models simulate the structures of somewhat small ships, ranging from 500 to 4,000 tons in gross tonnage. The most probable or severe cases in ship side and bow collisions were taken up here. It was assumed in the bow collision that a ship would strike in a right angle encounter with the flat plane of a bridge pier. The test results show that the buckling of hull plate is dominant in the strength of the bow of a ship. In the sideways collision, the side of a ship was assumed to hit the corner parts of a bridge pier. The load-deformation characteristics of the side of a ship show a distinct difference between the structural systems, i.e. transversely-framed side structures and longitudinally-framed ones. In the both cases, the collision forces calculated by a simple theoretical expression are graphically represented for a range of gross tonnage of ships. Secondly, we study the effectiveness of some buffer equipments attached to the circumference of a bridge pier, on the basis of the tests on buffer models crushed by the bow or side models. Force-deformation curves were compared between these types of buffer models. The composite-type of buffer model, in general, was found to do well from the viewpoint of the energy absorption efficiency. As a numerical example, the amount of energy absorption during an actual collision was estimated for this type of buffer.