High-Strength Concrete Deep Beams With Effective Span and Shear Span Variations

Abstract

Nineteen reinforced concrete deep beams with compressive strengths in the range of 41 MPa ≤ f' c ≤ 59 MPa (6000 psi ≤ f' c ≤ 8600 psi) were tested under two-point top loading. All the beams were singly reinforced with main steel percentage p = 1.23 percent and with nominal percentage of shear reinforcement ρ v = 0.48 percent. The beams were tested for seven shear span-depth ratios a/d, ranging from 0.27 to 2. 70, and four effective span-depth ratios l e /d, ranging from 2.15 to 5.38. Test results indicate that l e /d has little influence on the magnitude of the failure load. But for beams with a/d ≥ 1.00, the flexural failure mode becomes dominant with increasing l e /d. The test results are compared with predictions based on the current ACI Building Code. The comparisons reported in this paper will provide an added assurance to designers that the deep-beam provisions in the ACI code, though essentially based on concrete strengths of less than 41 MPa (6000 psi) will insure safe designs for higher strength deep beams. However, the ACI code tends to be rather conservative, as shown by comparison to the Deep-Beam Design Guide issued by the Construction Industry Research and Information Association, London. Nevertheless, the ACI code has the important advantage of being easy to use.