Ultimate Shear Strength of Fibrous Reinforced Concrete Deep Beam With ‎Various Sizes of Square Web Openings Under Shear-Control Loading ‎

Abstract

In practice, in high-rise buildings, especially in reinforced concrete deep beams bearing high axial loads, openings may be located in the zone of maximum shear force and zero bending moment (shear control), and this may be a serious problem if the shear strength of these beams is not predicted. Therefore, this study aimed to investigate the ultimate shear strength in this case (shear control) experimentally and compare the results with analytical equations to make it easier for those working in this field to use these equations when needed. In this research, the experimental deep beam specimens were divided into two groups. The first group consists of three reinforced concrete deep beams as normal concrete beams; the first is solid, and the second and third have square openings of 200 mm and 300 mm, respectively. The second group has the same arrangement as the first group, with the addition of 0.75% steel fibers to the concrete mix as fibrous concrete deep beams. The experimental results indicated that the presence of square openings with sharp corners leads to a reduction in the ultimate shear strength of the beams due to the interruption of the load transfer path. Steel fibers improved the performance of the beams, increased the cracking load, and delayed the failure load. The Kong and Sharp equation was used for reinforced concrete deep beams (solid and with opening), the ratio of experimental to analytical ultimate shear strength for the fibrous reinforced concrete deep beams was 0.998 for the solid beam, 1.162 and 1.585 for beams with 200 mm and 300 mm square openings, respectively. For the normal reinforced concrete deep beams, the ratios were 0.871 for the solid beam, 1.167 and 1.245 for beams with 200 mm and 300 mm square openings, respectively. In general, the analytical results were close agreement with the experimental results. Therefore, these equations can be reliably used to predict the ultimate shear strength of normal and fibrous reinforced concrete deep beams with openings located in the region of maximum shear forces and zero bending moments (shear control).