Numerical study on the influence of localized damage effect of explosives on steel plate structure damage under underwater contact explosions

Damage features of RC slabs subjected to air and underwater contact explosions

The blast experimental test is an effective method to observe the failure characteristics of reinforced concrete (RC) slabs to contact explosion. However, the existing explosion experiments on RC slabs are mainly focused on air blast. Corresponding experiments of RC slabs to underwater explosion are limited. In this article, both air and underwater contact explosion experiments are carried out. Ten specimens of concrete slabs including three plain concrete slabs and seven RC slabs are tested. Five specimens are subjected to air contact explosion, and other five specimens are subjected to underwater contact explosion. The influence of the boundary condition, reinforcement, charge shapes, and charge mass on failure modes of concrete slabs is investigated. The damage characteristics and failure modes of concrete slabs subjected to air and underwater contact explosions are compared. The results indicate that underwater contact explosion can cause more damage to the concrete slab than the same amount of explosive in air. Even one electric detonator detonated in the water can cause damage to the RC slab.

Failure modes and effect analysis of concrete gravity dams subjected to underwater contact explosion considering the hydrostatic pressure

Experimental and numerical study on damage behavior of air-backed steel-concrete-steel composite panels subjected to underwater contact explosion

Experimental and numerical study on local damage effect of ultra-early-strength reinforced concrete slabs (URCS) under contact explosion

In order to investigate the local failure modes and damage effects of reinforced concrete (RC) beams under contact explosion, the experimental studies of RC beams with the same size under different TNT charge masses were conducted. In the tests, the typical engineering scale RC prototype beams designed for frame structures were used as research objects. Through four independent explosion tests, the failure modes and damage characteristics of the RC beams were observed at different TNT charge masses, and the influence of different TNT charge masses on the local damage was analyzed. The results show that RC beams undergo four types of local failure modes such as front crater, side breakdown, back collapse and section punching under contact detonations. The depth of crater, thickness of the spallation, surface damaged area, and the deformation of the steel bars exhibited a linear increase with the cubic root of TNT charge masses. Based on the experimental data, the local damage degree could be divided into four grades: slight, moderate, serious and severe, that could be evaluated by the proportional charge criterion. The research results can provide a theoretical basis for designing the anti-blast structures and assessing the damage of components subjected to explosive loading.

Experimental and numerical study of damage characteristics of RC slabs subjected to air and underwater contact explosions

Underwater contact explosion will cause serious damage to the multi-cabin protective structure (MPS) of large ships. In order to improve the protective performance of MPS, an effective way is to set arc-shaped supports behind the main protective wall to reduce the risk of damage. In order to explore the damage mechanism of multi-cabin protective structure with arc-shaped supports under contact explosion, a large-scale cabin model was designed and the underwater contact explosion test was carried out. The experimental data of the multi-cabin protective structure model after the test were obtained, such as model breach size, deformation and impact acceleration. The results show that underwater contact explosions will cause significant damage to the outer structure of the MPS, with main forms of damage including tearing of the outer plate, buckling of internal components, and production of fragments. The calculation method for breach size based on panel energy is in good agreement with the experimental results. Additionally, setting arc-shaped supports behind the main protective wall can significantly reduce the deformation of the main defensive wall and mitigate the risk of tensile failure at the upper and lower joints.

Experimental and numerical investigation of arch concrete slabs subjected to underwater contact explosions with the inner arch side facing air

Study on the impact characteristics of underwater explosion bubble jets induced by plate structure

In this paper, the real-size modeling is established based on the outer plates of an unmanned ship, and 30 different working conditions are set according to different characteristic plates, relative explosion distances, and the TNT equivalents. Subsequently, numerical simulations are used to analyze the damage process and characteristics of underwater contact explosion, and the responses under different parameters were compared. The results indicate that both the relative explosion distances and the TNT equivalent have significant impact on the damage characteristics of the characteristic plate, and the transverse and longitudinal reinforcing ribs on characteristic plate play an important role in resisting underwater contact explosion shock waves. The characteristic plates numbered XC1, XC2, WD1, and WD2 all have strong resistance to underwater contact explosion, with XC1 being the best. These parameters can provide a reference for the structural design of subsequent unmanned ship outer plates in the future.

Blast resistance performance and failure modes of prestressed thin-walled aqueducts subjected to underwater contact explosion

Large naval warships are severely threatened by underwater weapons. Especially, the hull structures will suffer excessive local damage in the case of underwater contact explosion, which brings severe challenges to the combat effectiveness and even vitality of ships. In this paper, the underwater protective structures of large naval warships were taken as the research object. The development history of underwater protective structures in various countries was briefly introduced. The damage loading generated by underwater contact explosion and the damage mechanism of underwater protective structures were analyzed. Based on the specific structures and different damage loading, the corresponding protective measures were summarized. In view of the present research situation, some problems were put forward for the future investigation. This may provide a reference for the design of underwater protective structures so as to improve the anti-explosion ability of large naval warships.

In this paper, comprehensive underwater contact explosion experiments are carried out on flat plates, aiming to substantiate the experimentally observed damage characteristics. Furthermore, the radius size during the bubble pulsation process is validated. Subsequently, a study on the damage characteristics of underwater explosion loads on double-layered cylindrical shells is conducted. The coupling mechanism between underwater explosion loads and elastoplastic structures is explored. The influences of factors such as explosion distance, water depth, and the type of fluid medium between the double-layered shells on the structural damage modes and damage effects are analyzed. The research shows that within a certain range, variations in the explosion distance mainly affect the destructive effects of shock wave loads on the structure, while the large temporal and spatial scales of bubbles make them less affected by the explosion distance. Changes in water depth primarily affect the destructive effects of bubble loads on the structure. As the water depth increases, the pulsation period and radius of the bubble decrease, and the energy dissipation during bubble pulsation also decreases. Consequently, the pulsating pressure generated by the secondary expansion of the bubble and the intensity of the water jet load can be effectively increased. In deep-water environments, the structural deflection is mainly determined by the bubble load. The water layer between the double-layered shells can effectively reduce the damage effects of shock waves and bubble loads on the structure.

Underwater bottom-sitting shell structures face threats from underwater explosion shock waves. To investigate the damage characteristics and dynamic response of bottom-sitting shell structures under underwater explosion shock waves, three-dimensional numerical models of semi-spherical and semi-cylindrical bottom-sitting reinforced concrete (RC) shells under underwater shock waves were established based on the Arbitrary Lagrangian–Eulerian (ALE) algorithm using LS-DYNA software. The influences of the shock wave transmission medium, explosive equivalent, explosive distance, hydrostatic pressure, and reinforcement on the damage characteristics and dynamic response of semi-spherical and semi-cylindrical bottom-sitting RC shell structures were studied. The results indicated that the damage and center vertical deformation of RC shells under underwater shock waves are significantly greater than those under air shock waves. With an increase in explosive equivalent or decrease in explosive distance, the damage and center vertical deformation of RC shells are increased. The damage to the inner surface of RC shells is more severe than the outer surface. The damage and center vertical deformation of RC shells can be reduced by bottom reinforcement and an increase in the diameter of the steel bar. The ‘hoop effect’ caused by hydrostatic pressure restrains the horizontal convex deformation and slightly decreases the macroscopic damage and vertical center deformation of the semi-spherical RC shell with an increase in hydrostatic pressure within the range of 0–2.0092 MPa. The hydrostatic pressure restrains the horizontal convex deformation of the semi-cylindrical RC shell. However, inward concave deformation of the shell center is increased by hydrostatic pressure, inducing an increase in the damage to and center vertical deformation of the semi-cylindrical RC shell. These findings may offer a reference for the construction and design of protective measures for underwater bottom-sitting shell structures.