Residual axial capacity of circular reinforced concrete columns subjected to contact explosions

Abstract

The threat of terrorist bombing attacks on critical infrastructure has attracted a lot of attentions over the past decades. Contact explosion with a small explosive charge mass can cause severe damage to RC columns. Since columns are the primary load-bearing components in structures, the failure of critical columns can initiate collapse of the entire structure and result in devastating consequences associate with significant casualties and economic losses. To prevent catastrophic structural collapse, the most critical requirement of blast-damaged columns would be the residual capacity to withstand axial load. In this study, the residual axial load-carrying capacity of RC columns damaged by contact explosions was numerically investigated. A high-fidelity physics-based numerical model of RC columns under contact explosions was developed using the non-linear dynamic analysis program LS-DYNA with Arbitrary-Lagrangian–Eulerian (ALE) and Fluid-Structure Interaction (FSI) algorithms. The numerical model was comprehensively validated with existing experimental results in literature. An extensive parametric study was carried out to determine the effect of critical design parameters, including explosive charge mass, column diameter, longitudinal reinforcement ratio, and transverse reinforcement ratio on the residual axial load-carrying capacity of RC columns after contact explosions. The damage degree of the blast-damaged columns was quantitatively analyzed with a damage criterion based on the residual axial load-carrying capacity. Based on the parametric analysis results, an empirical formula was developed through multivariable regression analysis method for prediction of the damage degree and residual axial load-carrying capacity of blast-damaged RC columns under contact explosions. The proposed empirical formula can be utilized in preliminary design of RC columns against contact explosions and failure risk assessment of RC columns after contact explosions.