Experimental study on dynamic buckling of submerged grid-stiffened cylindrical shells under intermediate-velocity impact

Dynamic buckling prediction of submerged structures under impact loads is a challenging problem for both theoretical and numerical approaches, and the experimental data is very limited. In the present paper, dynamic buckling of grid-stiffened cylindrical shells submerged in a large opening pond at a depth of 5 m and subjected to radial intermediate-velocity impact was experimentally investigated. In order to increase load durations under the condition of fixed peak pressure, explosive depth and standoff distance, airbags composed of O2 and C2H2 were used and exploded underwater to generate impact load. Amplitudes and durations of shock waves and pulsating bubbles were characterized by using pressure transducers. Measurements of hoop and axial strains reveal that global buckling of skin and stiffeners of the grid-stiffened cylindrical shell occurred under bubble pulsation loads, which features mutation and separation of strains and a sudden change in the vibration period of the stiffened shell with a small increment of impulse. 6 half waves and 1 half wave are observed along the circumferential and axial directions of the shell, respectively. Larger bubble pulse impulse, greater deformation and vibration of the shell under larger impact are the main reasons for global dynamic buckling of the grid-stiffened cylindrical shell.