MINIMUM SHEAR REINFORCEMENT FOR OPTIMUM DUCTILITY OF REINFORCED CONCRETE BEAMS

Abstract

Failures in reinforced concrete (RC) structures und er transverse shear forces are proved to be catastr ophic with the presence of web reinforcement. The minimum web reinforcement recomm ended by several codes of practice has been intende d to maintain adequate strength and deflection ductility after the formati on of diagonal cracking and to contain widening of the diagonal cracking. However, the expressions for estimating the minimum shear re inforcement in the codes of practice are based on t he experimental data base observed on testing of small size beams made of nor mal strength concrete (NSC). Such code provisions n eed to be reinvestigated on large size beams made of high strength concrete (HS C). Further, there has been lack of consensus on th e 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 express ion has been proposed incorporating a wide range of parameters. A compari son of the minimum shear reinforcement predicted by the proposed expression has been made with the codes of practice. The influ ence 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 i ndex. Small size beams exhibited significant ductil ity for the given shear reinforcement index.