Abstract: In order to investigate the damage criteria of reinforced concrete (RC) beams under blast loading, the experimental study of two different dimensions of RC beams under different blast distances and charge masses is carried out. Two common RC beams designed for tall buildings and frame structures are taken as the research objects. The damage mode and characteristics of RC beams are got through 11 independent blast experiments. The results show that, when RC beams are subjected to close-in blast loading, the damage level increases with the increase in explosive mass at the same blast distance, the damage mode of RC beams changes from a few fall-off of concrete on the two sides of upper side and a few ruptures on the rear face to the compressed flexural damage of reverse triangle cone-shaped concrete on the upper side and triangle cone-shaped crack and a fall-off of concrete on the rear face, and finally the triangle cone-shaped damage areas on both upper side and rear face are perforated to result in a crushed and punched damage of concrete in the middle area. The damage area increases with the increase in explosive mass. Under close-in blast loading (blast distance= 0.5 m for example), the damage criteria of the RC beams used in the experiment are: the beam suffers from minor damage for scaled burst distance Z>0.4 m/kg^1/3; it suffers from moderate damage for scaled burst distance 0.3 m/kg^1/31/3; it suffers from high damage for scaled burst distance 0.28 m/kg^1/31/3; it suffers from serious damage for scaled burst distance Z<0.28 m/kg^1/3. It is also found that the damage of RC beam not only depends on the scaled burst distance under close-in blast loading, but also depends on the burst distance. At the same scaled burst distance, the more the burst distance is, the damage of RC beam is more serious. The results can be useful for engineering application and damage assessments.

Key words: ordnance science and technology, explosion load, reinforced concrete beam, damage mode, damage criterion