Maximum Shear Strength of Reinforced Concrete Beams

Current codes limit the maximum shear strength in reinforced concrete beams to prevent possible sudden shear failure due to over-reinforcement. The ACI 318-19 limit is criticized to be over-conservative, especially for high-strength concrete beams. Based on the force-transfer mechanism of the beams, this paper investigates this issue by deriving a model to determine the shear strength of rectangular beams with a shear span-depth ratio exceeding 2. According to the proposed model, it is found that there are two influential parameters of the maximum shear strength for beams--that is, concrete strength and longitudinal tension reinforcement. Considering the softening phenomenon of reinforced concrete, the use of [square root of (term)][f.sub.c] in the ACI 318-19 limiting equation seems appropriate for high-strength concrete beams. However, the ACI 318-19 limit on the maximum shear strength of beams seems conservative for beams with a larger amount of longitudinal tension reinforcement. Keywords: force-transfer mechanism; maximum shear strength; shear failure mode; softened concrete strength.