Prestressed concrete structures, designed to enhance the compressive strength of concrete through internal pretension, are increasingly susceptible to serviceability issues caused by rising live loads, material degradation, and environmental impacts. Strengthening or retrofitting offers a practical and cost-effective alternative to full replacement. This study investigated the flexural strengthening of prestressed concrete T-beams in the negative moment region using near-surface mounted (NSM) carbon-fiber-reinforced polymer (CFRP) rods. Validation against experimental results from the literature demonstrated high accuracy, with an average numerical-to-experimental ultimate load ratio of 0.97 for reinforced concrete T-beams strengthened with NSM-CFRP rods, a negligible difference of 0.49% for prestressed concrete I-beams, and a minimal error of 1.30% for prestressed concrete slabs strengthened with CFRP laminates. Parametric studies examined the effects of CFRP rod embedment depths and initial prestressing levels. In certain cases, achieving the minimum embedment depth is not feasible due to design or construction constraints. The results showed that fully embedded CFRP rods increased the ultimate load by up to 14.02% for low prestressing levels and 16.36% for high levels, while half-embedded rods provided comparable improvements of 11.20% and 15.76%, respectively. These findings confirm the effectiveness of NSM-CFRP systems and highlight the potential of partial embedment as a practical solution in design-constrained scenarios.

This work examines the performance of reinforced concrete (RC) beams strengthened using bonded steel wire rope (SWR) at various prestressing levels. The strengthening approach has, however, been applied to the flexural strengthening of RC T-beams in the negative moment region, in order to determine its advantages. For this purpose, four RC T-beams were fabricated and tested under monotonic four-point bending: one control beam (S00), one beam strengthened with non-prestressed SWR (S20), and two beams strengthened with SWR (prestressed at 10% and 20% of their ultimate tensile strength: S21 and S22). The results indicate that the strengthened beams exhibit higher load-carrying capacities. Specifically, the cracking load, yield load, and ultimate load of S20, S21, and S22 increase by 10%–30%, 30%–50%, and 50%–90%, respectively, compared to S00. Additionally, there is an improvement in stiffness and energy absorption capacity. However, these strategies may have a dual effect on the specimens, resulting in a reduction in their ductility index. Finally, the tested beams were replicated using a three-dimensional finite element model, which has proved effective in predicting the behavior of such structures and, therefore, was found to be appropriate for use in future studies.

This study experimentally and numerically investigated the effectiveness of fiber-core steel wire ropes (FC-SWRs) in enhancing the flexural performance of reinforced concrete (RC) T-beams using a bonding technique. The investigation focused on deflection, flexural load-carrying capacity, and failure modes, along with key behaviors such as ductility, stiffness, energy absorption, and steel strain response. Two beams were tested under four-point bending until failure—one serving as the control specimen and the other strengthened with bonded FC-SWRs to improve its flexural behavior. Additionally, an analytical study was conducted using a computer program based on the Modified Compression Field Theory (MCFT), and the results were compared with experimental findings. The validation of the analytical model enabled further parametric investigations, examining the influence of the FC-SWR diameter, modulus of elasticity, and steel reinforcement ratio on flexural performance.

This study investigated a strengthening strategy for reinforced concrete (RC) T-beams in the negative-moment region using polymer cement mortar (PCM) systems. Monotonic loading tests were conducted on beams retrofitted with PCM, incorporating steel reinforcements of either 13 mm or 16 mm in diameter. The flexural performance of the strengthened specimens was assessed under three-point bending, with a focus on load–deflection behavior, crack patterns, and failure modes. Key structural parameters governing the structural response were analyzed. The findings indicated that incorporating PCM markedly improved the flexural capacity of RC T-beams, with increases in the ultimate load of 55% and 99% for the two reinforcement configurations. Although the beam strengthened with 16 mm steel bars exhibited reduced ductility, its energy absorption was 29% higher compared to its 13 mm counterpart. A three-dimensional nonlinear finite element model was also developed in ABAQUS 6.14, and its predictions closely matched the experimental observations.