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In this study, shear-critical reinforced concrete (RC) beams were strengthened by combining the prestressing and near-surface mounted (NSM) rods approaches. The potential danger of failure in such RC beams is a substantial concern as it is considered a potential threat. This study addresses its careful mitigation through experimental identification and numerical analysis to enhance the safety and sustainability of buildings by reducing the probability of failure risk for these RC beams. Nine of the ten RC beams that were tested had strengthened, and one had not. Internal prestressing (IP) within the beam body, external prestressing NSM (PNSM), internal embedment (IE) inside the beam with or without prestressing, and NSM are the strengthening technologies that were employed. The range of the extra shear reinforcement ratios (μs) was 0.87% to 1.60%. We investigated how strengthened beams behaved structurally in terms of the cracking load, ultimate load, load–deflection response, ultimate deflection, and stiffness. The insertion of five pairs of PNSM rods (μs = 1.45%) and five pairs of IP rods (μs = 1.6%), respectively, increased the beams' shear capacity by 57.8% and 70.4%. Shear capacity increased by 23.2% when three pairs of IE rods (μs = 1.02%) were installed. The prestressing location had an impact on shear capacity, with the interior case surpassing the external one. Compared to the control, the stiffness of the strengthened beams rose by 20%, 82%, and 84.4% when three, four, or five pairs of internal prestressing rods were added. A formula is proposed to calculate the shear capacity of all beams strengthened using various methods. [ABSTRACT FROM AUTHOR]