Strength prediction of a bottle-shaped strut for evaluating the shear capacity of reinforced concrete deep beam

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For the analysis and design of reinforced concrete (RC) deep beams, the strut-and-tie model is typically employed to simulate the flow of stresses. A bottle-shaped strut develops between the loading point and support, in which compressive stress spreads laterally and induces tensile strain in the transverse direction, which reduces the compressive strength of the strut significantly. Web reinforcements are provided in deep RC beams to prevent splitting of the diagonal strut due to the presence of these transverse strains. In this article, a simplified design procedure based on the strut-and-tie model (STM) is proposed for the evaluation of the shear capacity of deep beams with web reinforcement. The suggested model is based on modified compression field theory and considers the impact of shear reinforcement ratio, transverse tensile strain, post-cracking strength of concrete, and the actual dispersion of compressive stress based on strut geometry (aspect ratio) for strength prediction of bottle-shaped struts. The experimental results of RC panels and deep RC beams reported in the literature are used to validate the results of the suggested model. The findings demonstrate that the proposed STM evaluates the shear capacity of deep RC beams more precisely than capacities estimated by ACI 318-19, AASHTO LRDF, and Eurocode 2 (EC2). In addition, a comprehensive parametric study has been carried out to investigate the effect of various design parameters on the shear capacity of deep RC beams.