Shear Behaviour of Ordinary Strength RC Slender Beams

Abstract

Shear reinforcement in Reinforced concrete beams depends upon various parameters such as longitudinal steel ratio, aggregate type, strength of concrete, size of beam and types of loading. These factors are not fully incorporated in ACI code provision for design of minimum shear reinforcement. Zarari studied these factors on shear behavior of R.C beams analytically but experimentally have not been validated. To validate these factor, experimental work was undertaken on the shear behavior of ordinary strength reinforced concrete slender beams with moderate longitudinal reinforcement. Based on the experimental work, Modification to Zarari’s equation is proposed on shear behavior of R.C beams. The experimental program consisted of testing of eight simply supported R.C slender beams subjected to two concentrated loads with span to depth (a/d) ratio of 2.5.Test specimen were divided into four groups based on amount and spacing of minimum shear reinforcement in RC beams. Two specimens were prepared without shear reinforcement, two specimens were based on ACI code provisions, two specimens were prepared according to Zarari’s (2003) equations, and two with modified equations presented in this study. Ultimate shear strengths obtained in this experimental program are compared to the analytical shear strengths calculated according to ACI code, Zarari equation and the Modified Zarari equation. Test results shows that, the proposed equation and Zarari equation gives better prediction of shear capacity of RC beams than ACI. Based on the test data, it was also found that minimum shear reinforcement should be such that it allows development of nominal flexural capacity in RC beams; accordingly a new expression for calculating minimum shear reinforcement is also proposed which incorporates all contributing factors.