Experimental study of the coupled damage characteristics of a large-scale hull girder subjected to an underwater near-field explosion

This paper presents the design and testing of a 10 m box-shaped hull girder model to investigate the overall response characteristics and damage modes of a warship subjected to an underwater near-field explosion. A 100 g trinitrotoluene (TNT) charge was detonated right below the midspan or quarterspan of the girder. On this basis, the structure strain, shock environment, and displacement of the girder were obtained under varying conditions, including the explosion depths and positions of attack. In the study, the coupling motion and frequency response characteristics between the explosion bubble and the hull girder were analyzed. The basic conditions for the occurrence of a whipping response or sagging damage to the hull girder were proposed. The experimental results showed that the girder and the bubble could easily exhibit a coupled resonance when the frequency of the explosion bubble pulsation is close to the first wet frequency of the girder. Also, a bending deformation or an overall damage is more likely to occur when the underwater explosion (UNDEX) happened directly below the midspan of the girder in comparison to other explosions at different attack positions. It was found that the structural damage is mainly concentrated in the middle of the 1/5 girder length region.