Calculation of the collision resistance of ships and its assessment for classification purposes

Abstract

Within the framework of a research programme ‘Tanker Safety’ Germanischer Lloyd has developed a program system for the evaluation of the absorbed plastic deformation energy in a ship-ship collision. The ultimate load capacities of the ship structures in the areas affected by the collision are evaluated stepwise. The total collision energy absorbed by plastic deformations of the ship structures is evaluated on the basis of the minima of the ultimate load capacities and the corresponding penetration depths. By means of the collision energy absorbed, the collision speed necessary to cause damage can be determined. It is now possible to classify ships with regard to their resistance against collisions and to assign relevant class notations. The resistance of a ship against collision impacts is expressed by the class notation COLL with index numbers 1/2/3, etc. The index numbers indicate that — as compared with a non-strengthened single hull reference ship — a critical situation is likely to occur only if the deformation energy absorbed in the collision exceeds that of the non-strengthened reference ship by more than 100%/200%/300%, etc. A ‘critical situation’ is defined by, for example, rupture of cargo tanks with subsequent spillage of cargo or water ingress into dry cargo holds.