A simplified calculation method for the time-history curve of stress waves in concrete induced by cylindrical charge explosion

To establish a simplified calculation method for the explosion stress wave time-history curve induced by cylindrical charge explosions in concrete considering the influence of aspect ratio, this paper presents a numerical simulation study on cylindrical charges with varying aspect ratios detonated in concrete. The study is based on an enhanced version of the Kong-Fang concrete constitutive model and the multi-material ALE algorithm, following validation of the model’s reliability against existing experimental data. The analysis focuses on the attenuation law of peak stress, the rise time, and the evolution of the constant impulse action time under different scaled distances. Results reveal that the peak stress follows a power-law decay pattern across various damage zones. With increasing aspect ratio, the attenuation index increases significantly, the attenuation coefficient decreases, and the extent of the cracked zones expands. In the proximity of the explosion, the stress rising time of the explosion stress wave increases linearly with distance, and the rate of this increase becomes more pronounced as the aspect ratio grows. Once the stress wave enters the cracked zone, its waveform is influenced by reflections and scatterings at crack interfaces, leading to a gradual flattening of the waveform and a subsequent stabilization in stress rising time. The equivalent impulse duration increases linearly with distance in the near zone but exhibits a decreasing trend within the fracture zone, reflecting the modulating effect of concrete damage on explosion stress wave propagation. Based on the principle of impulse equivalence, a simplified triangular explosion stress wave model is proposed, suitable for engineering-level anti-explosion analysis. Through segmented regression analysis, practical formulas are derived to estimate the peak stress, stress rising time, and equivalent impulse duration, explicitly incorporating the aspect ratio as a key parameter. These formulas offer a parametric tool for engineering calculations of explosion stress waves generated by internal cylindrical charge explosions in concrete structures.