Longitudinal Strength of the Fore Body of Ships Suffering from Slamming

A series of model tests have been conducted to study the mechanism of failure and to evaluate the ultimate longitudinal strength of the fore body of ships by applying forces simulating impact load due to slamming. Three types of structural models of the fore bodies were tested; they were designed to be similar to a 50,000DWT bulk carrier, a 120,000DWT ore carrier and a 1,400TEU container ship, respectively. In these cases, their side shells were observed to yield first due to shear stresses. Then the plastic region spread throughout the side shells, resulting in a progressive rise of the longitudinal normal stresses in the deck plating, which might eventually cause buckling of the plating. This paper also presents an analytical method to realize the collapse mechanism and to evaluate the ultimate strength of the fore body of hulls subjected not only to bending moments but also to shear forces. By comparing the calculations with experiments, it is confirmed that the present method gives satisfactory estimates for the collapse load and simulates the collapse mechanism. The yielding throughout the side shell plays a key role in the total collapse mechanism because it causes loss of hull's shear rigidity and a rapid rise of deck stresses as well.