Residual strength of reinforced concrete columns subjected to blast loading

Failure modes of concrete structures due to blast load vary according to the point of detonation, stand-off distance and TNT charge weight. Usually, columns are the key load-bearing elements in concrete frame structures. They are typically weak, not to long-distance explosive loadings, but to short-distance loadings. The effect of blast loadings occurring within a short distance was examined analytically in this study. Scaled distance (which considers both the stand-off distance and TNT charge weight), various aspect ratios of column sections with the same sectional area and reinforcement ratio, and various arrangements of longitudinal reinforcements with the same sectional area and reinforcement ratio were considered as variables in order to evaluate damage levels and define the relations among these variables with respect to the residual strength of columns after blast. Autodyn was used for the finite-element analysis. It was found that the ratio of residual strength to nominal axial strength of the columns decreased as the contact area of the column to the blast loading became smaller; a denser arrangement of the longitudinal reinforcements using smaller diameter bars showed relatively better residual capacity.