Effect of close-in successive explosions on the blast behaviors of reinforced concrete beams: An experimental study

The blast performance of reinforced concrete (RC) structures subjected to successive explosions remains an unresolved issue. This study experimentally investigated the blast behaviors (failure modes and dynamic responses) of RC beams under successive explosions of two 0.5 kg TNT. Furthermore, the cumulative effect of two 0.5 kg TNT explosions was studied by comparing the successive explosion-induced blast behaviors of beams with the single 1 kg TNT explosion-induced blast behaviors of beams both at the same standoff distance and at the same scaled distance. In addition, based on the support reaction force and the relation between reaction force and mid-span displacement, the true dynamic load carrying capacity was defined, and the residual load carrying capacity, residual stiffness and absorbed energy were used to assess the damage degree of RC beams caused by successive explosions. Results indicate that beams under successive explosions experienced a transformation of failure mode from local failure in brittle mode to a local and bending failure in ductile mode. And compared to the effect of a single 1 kg TNT explosion on the damage to beams, the cumulative effect of two 0.5 kg TNT successive explosions on the damage to RC beams is more significant at the same scaled distance, especially at smaller scaled distances. Furthermore, the effect of the first explosions on the residual load carrying capacity has an effect on the subsequent displacement responses of the damaged beams.