Minimum web reinforcement in deep beams

An experimental study was performed to examine current code requirements for minimum web reinforcement of reinforced concrete deep beams. Twelve full-scale tests were conducted in which the shear span-depth ratio (a/d) was 1.2, 1.85, or 2.5. At each a/d, the quantity of web reinforcement was the primary variable. Web reinforcement ranged from 0 to 0.3% in the vertical and horizontal directions. The compressive strength of concrete of the test specimens ranged from 3200 to 5000 psi (22 to 34 MPa). Diagonal cracking loads, diagonal crack widths, and failure shears were recorded for each test. The results indicated that a larger quantity of web reinforcement was needed to adequately restrain the width of diagonal cracks than to provide adequate deep beam shear capacity. Based on the strength and serviceability results, a minimum web reinforcement of 0.3% in each orthogonal direction was recommended for deep beams.