This paper evaluates the shear strength demand of reinforced concrete beams, defined as the shear capacity required to avoid shear failure and remain within the flexural failure. Unlike conventional shear design formulations, which evaluate shear and flexural strength independently, the proposed approach explicitly considers the shear capacity associated with the flexural capacity of the cross-section. Eight simply supported reinforced concrete beams with varying reinforcement ratios were tested to failure. Three types of failure were observed from the test: shear failure, shear failure after yielding of longitudinal reinforcement, and flexural failure. The test results indicate that the contribution of shear reinforcement and the flexural capacity of the cross-section are essential components that determine the type of failure of the beams. In addition, 66 experimental data collected from the literature were used in a statistical analysis to evaluate the shear strength demand. Based on statistical analysis, relationships between flexural capacity and shear demand, represented by α , β , and γ , are recommended for assessing shear strength demand in reinforced concrete beams. Based on statistical analysis, a model is recommended for evaluating the shear strength demand of reinforced concrete beams. The model was then applied in a parametric study of four reinforced concrete beam cross-sections with varying dimensions and longitudinal reinforcement ratios. The results indicate that the proposed method generally leads to more conservative shear reinforcement requirements than the minimum provisions of ACI 318–19, by explicitly enforcing capacity margins between shear and flexural demands associated with flexural-controlled failure, rather than increasing safety factors. This conservatism is intended to improve failure-mode control by reducing the likelihood of premature shear failure, while remaining within practical reinforcement limits for conventional beam design.
Said et al. (Thu,) studied this question.