Impact behavior of hybrid-fiber reinforced concrete beams

Abstract

The impact studies on concrete beams are primarily pertaining to the drop hammer impact, and studies involving projectile impacts on reinforced concrete beams are limited. In this research, the response of hybrid fiber reinforced concrete (HFRC) beams under quasi-static loading and the projectile impact was studied. The HFRC was produced using eight concrete mixes having different proportions and combinations of three fiber types (viz. polypropylene, steel, and Kevlar). The HFRC mixes had a total fiber volume fraction of 1.2% and 1.4%. In addition, plain concrete was used as a control. The beams were tested under the impact of hemispherical nose projectile at varying strike velocities. The projectile strike velocity was increased till the perforation of beams. The main flexural reinforcement in beams was provided on the back face. In order to assess the punching resistance of beams, the beams were tested under quasi-static punching load applied using the same projectile employed in impact tests. The use of hybrid fibers improved beams’ quasi-static punching resistance in terms of energy absorption and load–displacement behavior. The hybrid fibers also improved the impact response of beams by reducing damage levels, increasing perforation velocity, and reducing ejected mass. By modifying the earlier proposed model for slabs, the ballistic limit of HFRC beams is also predicted.