Assessment of Damage and Residual Load Capacity of the Normal and Retrofitted RC Columns against the Impact Loading

In the current study, the effect of the extreme lateral loading on the square and circular Reinforced Concrete (RC) columns with and without retrofitting was investigated. 3D finite element modeling of the columns and impact loading condition was performed using the ABAQUS/Explicit software. The data of a real scale blast test carried out in our previous study were used to verify the modeling accuracy. The effect of secondary moments due to axial load, different geometrical characteristics of the steel jacket, compressive strength of the concrete, and the longitudinal reinforcement on the explosive capacity of the column and its residual axial strength were studied. Results showed that the circular columns perform better under the sudden lateral pressure than equivalent square ones. Also, steel jacketing increased the explosive capacity of the column, which was more effective in the circular columns than the square ones. The results also indicated that steel jacketing with less buckling capacity had the least improvements on the column capacity. It was found that the effects of the initial axial force in the column were significant on its behavior under explosive loading condition, which should be taken into account in any modeling approaches. In general, the P-δ phenomenon had less effect on the circular columns than the square ones. Also, the use of a high-strength concrete and a higher percentage of longitudinal reinforcement further influenced the retrofitted columns than unretrofited (normal) ones, which was more evident in the circular columns in comparison with square columns.