Effect of Confinement on Flexure Behavior of Reinforced Concrete Beams Using Conventional Steel Stirrups

Abstract

Failure of reinforced concrete beams is either governed by reinforcing steel or compression concrete depending on relative resistance provided by these two materials to the applied bending moments. Failure initiated by compression concrete is brittle in nature and is not allowed by codes of practice. It is, however, recognized from applications to columns that confinement of concrete improves both ductility and strength of concrete members. Applicability of this concept of confinement to the reinforced concrete beams has been studied in this research program. Eight reinforced concrete beams were tested in this study. The specimens included four under reinforced and four over reinforced beams. In both types of beams, the stirrup spacing was less than required by normal shear design. The spacing was reduced in flexural span only. Two of the under reinforced beams and two of the over reinforced beams had stirrup spacing equal to 2.5 in and remaining four beams, two under reinforced and two over reinforced, had stirrup spacing of 3.5 in. It was concluded from experimental testing that beams with less stirrup spacing had better ductility, especially in case of over reinforced beams. However, effect on strength is negligible.