MINIMUM SHEAR REINFORCEMENT FOR OPTIMUM DUCTILITY OF REINFORCED CONCRETE BEAMS

G. Appa Rao

Abstract: Failures in reinforced concrete (RC) structures under transverse shear forces are proved to be catastrophic with the presence of web reinforcement. The minimum web reinforcement recommended by several codes of practice has been intended to maintain adequate strength and deflection ductility after the formation of diagonal cracking and to contain widening of the diagonal cracking. However, the expressions for estimating the minimum shear reinforcement in the codes of practice are based on the experimental data base observed on testing of small size beams made of normal strength concrete (NSC). Such code provisions need to be reinvestigated on large size beams made of high strength concrete (HSC). Further, there has been lack of consensus on the quantity of minimum shear reinforcement to be provided by different codes of practice, as they differ significantly in respect of HSC members. In this paper, many factors influencing the minimum shear reinforcement required in RC beams have been studied. An expression has been proposed incorporating a wide range of parameters. A comparison of the minimum shear reinforcement predicted by the proposed expression has been made with the codes of practice. The influence of shear reinforcement on the ductility of RC beams of varying sizes has been investigated. The optimum shear reinforcement index has been found to be somewhere between 0.45 and 0.5. Ductility of RC beams increases with increasing the shear reinforcement index. Small size beams exhibited significant ductility for the given shear reinforcement index.

Keywords: Minimum shear reinforcement, reserve strength, ductility, RC beams, HSC

DOI: https://doi.org/10.15623/ijret.2013.0210003