Shear strength of reinforced high-strength concrete beams with shear span-to-depth ratios between 1.5 and 2.5

Thirty high-strength concrete beams were tested under concentrated loads at midspan to determine their diagonal cracking strength and nominal shear st rength. The test variables were the compressive strength of concrete, the s hear span-to-depth ratio, and the vertical shear reinforcement ratio. The e ffects of each test variable were studied separately. Test results were com pared with strengths predicted using ACI 318-95. It was found that for beam s with shear span-to-depth ratios between 1.5 and 2.5, ACI Eq. (11-30) gene rally underestimates the shear strength contributed by the vertical shear r einforcement. New equations are presented for a more accurate prediction of the diagonal cracking strength and the nominal shear strength of reinforce d concrete deep beams.