Effect of Longitudinal Tensile Reinforcement Ratio on Minimum Shear Reinforcement in Reinforced Concrete Beams - II

Abstract

To avoid abrupt shear failure, ACI 318 – 08 specifies the requirements for the minimum amount of shear reinforcement for Reinforced Concrete Beams. The equation given for minimum shear reinforcement is based on previous experimental data from beams of normal and high strength concrete without any consideration for the effects of longitudinal reinforcement. Minimum amount of shear reinforcement corresponds to a value that restrains the growth of inclined cracking and prevents a sudden shear failure. The growth and width of inclined cracks, beside other factors, is also influenced by longitudinal reinforcement. Therefore, with the change in longitudinal reinforcement ratio, requirement of minimum shear reinforcement should also change. The influence of longitudinal tensile reinforcement ratio on minimum shear reinforcement in Reinforced Concrete Beams has been investigated through literature review and laboratory tests. The 6 x specimen beams having cross section 8" x 18" were divided into two groups and investigated for influence of longitudinal tensile reinforcement. The test results indicated that reserve strength (shear strength of beam with minimum shear reinforcement / shear strength of beam without shear reinforcement) of tested beams increased as the longitudinal tensile reinforcement ratio increased. Therefore inclusion of factor in the ACI code for determining minimum shear reinforcement should be considered.