article · Results in Engineering
Reinforced concrete structures can face significant structural vulnerabilities when reinforcing bars have insufficient overlap within critical negative moment zones. To address this issue, experimental testing was conducted on eleven cantilever beams subjected to flexure until failure. Three distinct strengthening approaches were assessed across varying anchorage lengths: externally bonded stainless-steel plates, near-surface mounted deformed steel bars bonded with engineering cementitious composites, and external pre-stressing. The near-surface mounted technique produced the greatest performance enhancement, followed by the external pre-stressing method. Most beams failed in flexure, though partial debonding affected externally strengthened specimens. A finite element model successfully replicated the experimental results with deviations under 4.4 per cent, showing that adding steel anchors reduces plate debonding. An analytical method was also formulated to determine ultimate load capacity.
Defects such as inadequate steel bar overlap can severely compromise the load-bearing safety of concrete infrastructure. Identifying effective retrofitting methods allows engineers to repair and upgrade defective cantilever beams safely, avoiding costly structural demolition while ensuring buildings and civil structures remain resilient under varying operational loads.
This work demonstrates applied and tested repair methods relevant to structural engineering consultants, civil contractors, and infrastructure maintenance bodies. The experimental findings, numerical model, and analytical calculation method offer practical guidance for structural remediation projects. Because validation remains at the experimental beam-testing stage, real-world deployment would require translation into formal building codes and commercial site-repair guidelines.
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Structural systems often undergo changes due to variations in the usage, the loading conditions, or the presence of defects in their elements. The problem can be exacerbated when there is insufficient overlap between reinforcing bars in critical moment zones. This article investigates the behavior of reinforced concrete cantilever beams exhibiting insufficient overlap between bars that used as main reinforcing steel bars in the negative moment zone. Various strengthening techniques were employed in order to improve these defected cantilever beams. Eleven beams underwent flexural testing until reaching failure. The experimental parameters encompassed the strengthening scenarios and the bonded length. Three strategies were used: the application of stainless-steel plates (SSPs) as externally bonded reinforcement, near surface mounted (NSM) reinforcement in which additional deformed steel bars were bonded utilizing engineering cementitious composites, and externally pre-stressing technique. The anchorage length was examined at 40, 50, and 60 times the internal bar diameter. It was noted that the most substantial improvement achieved with the NSM method, followed by the externally pre-stressing method. It is worth mentioning that most of the beams failed in a flexural manner, with partial debonding occurring in beams strengthened using external strengthening. Moreover, this article includes the development of a numerical model employing the finite element method to replicate the response observed from the experimentally tested beams. The accuracy of the model was confirmed through the comparison of its outcomes with the experimental data, demonstrating an acceptable level of accuracy with deviations of less than 4.4 %. This successful numerical investigation was also used to conduct a parametric study. From this study it is evident that the effect of debonding on SSPs can be reduced by adding steel anchors at the ends of these plates. Finally, an analytical method was proposed to calculate the ultimate load capacity of strengthened reinforced concrete beams. • Investigating performance of cantilever RC beams with insufficient overlap between reinforcing bars in negative moment zone. • Employing various strengthening techniques to enhance performance of cantilever beams. • Achieving the most substantial improvement with near surface mounted method. • Developing a numerical model utilizing finite element method. • Successful verifying numerical model and conducting a parametric study.
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DOI: 10.1016/j.rineng.2024.102869
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