A Review on Strengthening of Reinforced Concrete using Rectangular Beams, Tee Beams, and Rectangular and T- Beams with Web Opening

Abstract

In this study focuses on the review of strengthening structurally deficient reinforced concrete (RC) T-beams using externally bonded glass fiber reinforced polymer (GFRP) sheets. Rehabilitation of RC structures is essential due to aging, corrosion, construction defects, increased service demands, and seismic vulnerabilities. Among various beam configurations, T-beams are widely used in buildings and bridges, with shear failure being particularly catastrophic due to its sudden nature. Externally bonded FRP has emerged as a promising strengthening solution due to its high strength-to-weight ratio, corrosion resistance, and ease of installation. This research involved testing eleven full-scale RC T-beams under symmetrical four-point static loading to assess shear performance and failure modes. Key variables included the presence of steel stirrups, shear span-to-depth ratios, and the quantity of GFRP used. The results demonstrated a notable improvement in shear capacity with GFRP application. However, failure typically began with debonding of the FRP sheets, followed by brittle shear collapse. To address this issue and ensure full utilization of FRP strength, an innovative anchorage technique using GFRP plates was introduced, effectively preventing premature debonding. This method offers a more efficient, cost-effective alternative to traditional strengthening approaches and highlights the potential of FRP composites in structural rehabilitation.

Introduction

The civil engineering industry is adopting innovative materials and technologies to meet the demands of advanced infrastructure. As existing structures age and new standards rise, retrofitting becomes a cost-effective solution to enhance durability and safety against earthquakes and environmental forces, avoiding expensive full replacements.

The literature review focuses on rehabilitation strategies for reinforced concrete (RC) structures, highlighting fiber reinforced polymers (FRP) as a promising strengthening material. Studies are grouped into strengthening of RC rectangular beams, T-beams, and beams with web openings.

For RC rectangular beams, research shows that methods like integrating carbon-fiber-reinforced polymer (CFRP) bars, epoxy-bonded FRP sheets, and steel elements significantly improve load capacity, stiffness, and shear strength, though debonding remains a challenge.

For RC T-beams, CFRP composites, especially near surface mounted (NSM) laminates, enhance flexural and shear strength effectively. Innovative approaches such as FRP ropes and mechanically anchored dry carbon fiber sheets improve torsional and shear capacity, reducing typical failures like premature debonding.

For beams with web openings, which weaken shear capacity, studies suggest that pre-stressed shape memory alloy (Fe-SMA) bars and fiber reinforced concrete improve strength and control cracking. The impact of openings depends on size and position relative to load paths, with specific design guidelines developed for various opening shapes.

Conclusion

The following critical observations are made from the review of existing literature in the area of reinforced concrete (RC) beams strengthened with epoxy-bonded FRP 1) Most of the research efforts have been made to study the flexural and shear behaviour of RC rectangular beams strengthened with fiber reinforced polymer (FRP) composites. 2) Despite the growing number of field applications, there is limited number of reports on shear behaviour of strengthened RC T-beams using externally bonded FRP composites 3) A limited works have been reported on strengthening of RC T-beams with web openings. 4) There is a gain in shear capacity of RC beams when strengthened with FRP composites, peeling of FRP sheets from main concrete has been reported due to improper anchorage. 5) The study on anchorage system used for the prevention of debonding of FRP and concrete on shear behavior of RC beams is limited. 6) Many researchers are of the opinion that the previous design provisions do not have comprehensive understanding of the shear behavior.

References

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Copyright © 2025 Chandan Kumar , Ankita Singhai, Rahul Kumar Satbhaiya . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.