SHEAR BEHAVIOR OF HIGH STRENGTH REINFORCED CONCRETE DEEP BEAMS WITH WEB OPENINGS

Abstract

This study investigates the shear behavior of reinforcedhigh-strength concrete deep beams with and without web openings. Tests were conducted on four reinforced high-strength concrete deep beams with different shapes of web openings. The specimens were designed as simply supported beams subjected to concentrated loads on the top face and supported on the bottom face. The center of opening was positioned in accordance with that of the shear span area to completely interrupt the natural load path joining the edges of load and support plates. It was obvious that the simple load path changed to a more complex one and the ultimate shear capacity was reduced compared to that of the solid web specimen. The experimental capacities of the test specimens were compared with the strengths calculated using the strut-and-tie model provisions of Appendix A of the ACI 318-11 Code, which provides a convenient way of approximating load paths and force effects.It was found that the provisions of Appendix A of the ACI 318-11 Code provide slightly conservative estimates of strength for deep beams with web openings. The shear design procedures contained in the ECP 203-2007 Code and the ACI 318-11 Code were evaluated. These design procedures yielded slightly conservative predictions of the shear strength of the solid web deep beam. A database containing 51 deep beam shear tests was also collected from previous literature, in order to evaluate the adequacy of Appendix A of the ACI 318-11 Code provisions for deep beams, and to study the influence of important factors such as shear span to effective depth ratio and concrete compressive strength, on the ratio of strut-and-tie model estimation over the experimental capacity. It was obvious that the increase in such factors lead to an increase in the ratio of calculated-to-experimental shear strength.