Experimental and numerical investigation of reinforced concrete slabs under blast loading

The civilian buildings and the military structures have been unexpectedly exposed to the risk of terrorist attacks, particularly in the form of vehicle bombing and other portable detonation devices and explosives. For example, the recent incident happened in Sri Lanka wherein more than 250 people were killed and about 500 people had been injured. The high mobility of these potential threats is also a major challenge to the structural safety of any building. The chances of a full-fledged war with any country albeit low cannot be neglected. During such attacks, the bunkers and protective shelters in the field areas are highly vulnerable to the blast by high explosive rounds of Mortar, Rocket Launchers and Artillery shells with proximity fuzes which generate a rapid release of energy in the form of shock waves. The release of high energy and the developed shock waves are associated with significant structural and collateral damage. Considering the vulnerability when the structures are subjected to such intense loadings, an experimental and numerical study has been carried out to investigate the damage resistance of reinforced concrete (RC) slabs against blast loading. The target slabs (1000 mm x 1000 mm x 100 mm) have been subjected to blast developed by three different weights of explosive equivalent to the quantity of explosive commonly used by terrorists and military in mortars, high explosive shells of rocket launcher and artillery shells with proximity fuzes. The explosive has been detonated from two different standoff distances corresponding to the scaled distance 0.079-0.527 m/kg(1/3). The different failure modes and levels of blast-induced damage enabled better understanding of the performance of RC slabs when subjected to a similar impact/shock by mortars and rocket launchers. The one-way bending of the slab becomes more dominant with an increase in the explosive charge. On the other hand, the localized failure of the slab transformed into a globalized deformation with the increase in the standoff distance. The finite element simulations performed in ABAQUS/Explicit reproduced the damage, formation of the crater and spalling/scabbing of concrete. The blast pressure increased with an increase in the amount of TNT while reduced with the increase in the standoff distance.