During an explosion, a building’s stability is directly impacted by reinforced concrete (RC) columns. However, there is currently no theoretical analysis model that can precisely predict damage to RC columns after close-in/contact explosions. In the present study, the local damage response of RC columns under a rectangular charge was experimentally and numerically investigated, and a theoretical analysis model for predicting local damage after a contact explosion was developed. The experimental results verify the effects of concrete strength, standoff distance, transverse reinforcement spacing, and axial load on damage to RC columns. When the standoff is 100 mm, increasing the axial load can effectively reduce the damage to the center of the column surface. Numerical simulations were carried out to study the effect of different parameters on concrete damage, showing that the damage span of reinforced concrete increases with increased stirrup distance; however, when the stirrup distance decreases to 70 mm, the distance between the stirrups and the explosives is too close to limit the damage. The prediction model innovatively considers the attenuation of steel cross-section transmission and the characteristics of rectangular charges. Compared with traditional semi-empirical calculation models, it can accurately calculate local damage caused by contact explosions on reinforced concrete columns.

Existing models for predicting blast loads predominantly rely on idealized charge geometries like spheres or cylinders. However, blast load distributions from rectangular blocks, especially under close-in detonation conditions, are still not well predicted. This work develops and validates two-dimensional and three-dimensional numerical models using the finite element code LS-DYNA against experimental data. These models systematically investigate close-in blast load distributions from cylindrical and rectangular charges under center, single-end, and double-end initiation modes. The analysis details the effects of charge geometry, scaled distance, and azimuthal angle on the peak overpressure. Moreover, empirical fitting formulas for the bridge wave angle range and the deflection angle of peak pressure are derived from the numerical simulation results. Based on detonation theory, the differences in loading attributable to initiation points in contact explosions are analyzed, and an angular prediction model accounting for bridge wave formation is proposed. Furthermore, by calibrating three-dimensional simulations with accurate two-dimensional results using a ratio-based method, an empirical formula for predicting peak overpressure in close-in explosions is developed. This formula is applicable to cuboid charge geometries, initiation modes, and azimuthal angles. The study provides a theoretical foundation and a practical computational approach for accurately assessing the damage effects of non-standard explosive geometries.