Numerical Investigation of Damage to Typical Plate Structures Induced by Sequential Underwater Explosions

Abstract As a critical structural component in marine engineering, the air-backed stiffened plate frame plays a vital role in large-scale offshore installations. Underwater explosions can cause severe damage to nearby structures. This paper investigates the cumulative damage characteristics of the air-backed stiffened plate frame under underwater explosion loads. Compared to a single explosion, secondary explosions induce more complex structural damage due to material hardening after initial loading and substantial changes in load distribution on deformed surfaces. The arbitrary Lagrangian-Eulerian method is adopted to simulate the entire dynamic response of the air-backed stiffened plate frames subjected to sequential secondary underwater explosions. Additionally, the damage characteristics of plate frame structures with varying materials, plate thicknesses, and stiffener configurations under sequential secondary underwater explosion loading are further examined. Results indicate that, under the same charge weight and standoff distance, sequential secondary explosions markedly exacerbate localized structural damage, with extreme cases exhibiting notable differences in damage models. In contrast, a single explosion leads to more pronounced overall structural damage, characterized by larger deformation amplitudes of the plate structure and greater energy absorption. The influence of the primary shock factor on the damage enhancement effect of structures under secondary blast loading is substantial. A smaller primary shock factor leads to larger damage amplification in subsequent explosions. Stiffened plate structures with varying material types, plate thicknesses, and stiffener configurations exhibit consistent patterns.