Experimental and numerical investigation of rectangular reinforced concrete columns under contact explosion effects

The response of reinforced concrete (RC) members subjected to contact explosion effects is more severe than the response to non-contact explosions due to local material failure. The shock-wave reflection within the RC member causes severe local material damage. The resulting loss of concrete cross-section reduces the axial load and bending capacity of the RC member. It is hypothesized that the concrete loss from the sides can be prevented by increasing the aspect ratio of the cross-section. In a low aspect ratio RC column, the reflection is from three faces whereas in RC slabs and high aspect ratio columns the shock-wave reflection from the back-face only is significant. This study experimentally investigates the response of rectangular RC columns with varying widths of the cross-section, subjected to contact explosion effects. A range of aspect ratios was investigated to preclude the side face damage for a given depth of rectangular RC column. High fidelity numerical models were developed to predict the blast-response and the residual axial capacity of the blast-damaged rectangular columns. The numerical models were validated, and the results show a good correlation with the experimental results. Using a rectangular RC column aspect ratio with a width that precludes the side face spall significantly improves the residual axial capacity of the blast-damaged columns. Furthermore, parametric analyses were performed to numerically investigate the influence of the width on the residual axial load carrying capacity of rectangular RC columns subjected to contact explosion effects of breach-charge mass required for the provided depth. An increase in the width of the column improved the damage resistance even though the rectangular column was breached around the point of detonation. Hence, increasing the width of the rectangular RC columns can be effectively used to mitigate contact explosion effects.