Effect of the flexural and the horizontal shear reinforcements upon the strength of deep reinforced concrete beam

Abstract

A total of fourteen brick aggregate reinforced concrete deep beams have been tested in this study in order to investigate the effect of the flexural and the horizontal shear reinforcements on the strength of such beams. The test beams were single span and simply support8d type. The beams were divided into two series according to "heir span to depth ratio (LID = 1 and 2). The first beam of each series was designed and detailed as per the recommendations of ACI Building Code (ACI 318-89). In the other six beams of each series, the amount of either the flexural or the horizontal web reinforcement or both were increased in relation to those of first beam of the corresponding series. The nominal cross section of the first series of test beams was 6"x21" and that of the second series was 6"x12". The effestive span lengths for two different series of beams were 21" and 24" respectively. The test beams were subjected to uniformly distributed loads. The effects of the variations of different horizontal reinforcements (flexural and web reinforcements) and span to depth ratio on the cracking load, ultimate load, crack pattern, and the mode of failure were investigated. It was observed in the study that the amount of both the flexural and the horizontal web reinforcements influenced to some extentthe diagonal cracking load and the ultimate load capacity of test beams. It was also found that the change in the amount of either the flexural or the horizontal web reinforcement alonecould not bring about a significant change in the load carrying capacity of test beams. Certain modifications are suggested in five of the several available formulas (e.g. ACI 318-89 Singh, Ray and Reddy Ramakrishnan and Ananthanarayana ; Selvam and Kuruvilla ; and Mau and Hsu) in order to compute the ultimate load of deep reinforced brick aggregate concrete beams. It was shown that all of the five formulas with the suggested changes can be used efficiently to estimate the ultimate load capacity of deep beams.