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.

The failure risk of defected reinforced concrete (RC) beams is considered a potential threat. This risk is experimentally identified, numerically analyzed, and thoroughly diminished to enhance structural safety and sustainability to mitigate the potential for structural collapse during construction. This research investigates the efficacy of an external post-tensioning mechanism in enhancing the behavior of defected RC beams lacking shear reinforcement, employing both experimental and numerical approaches. Fourteen RC beams were tested to evaluate the impact of posttensioning force levels and the inclination angle of post-tensioning bars. The study found that regardless of force magnitude or angle, post-tensioning improved the failure characteristics of the non-stirrup beam. The failure mode transitioned from brittle to ductile, resulting in a more advantageous distribution of cracks. Reinforced beams exhibited increased cracking and ultimate loads, with the enhancement more pronounced at higher post-tensioning force levels. Inclined post-tensioning at angles of 75°, 60°, and 45° demonstrated substantial enhancement in cracking and ultimate loads, as well as elastic stiffness. The findings highlighted the superiority of inclined post-tensioning configurations, especially at 60°, for reinforced beams. Moreover, the study revealed a significant increase in absorbed energy with the proposed strengthening system. Additionally, finite element modelling (FEM) was used to replicate the tested beams. FEM accurately predicted the crack development, ultimate capacity, and deformation, aligning well with experimental observations.