PSI - Issue 78

Rawand Alnsour et al. / Procedia Structural Integrity 78 (2026) 1261–1268

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increase in self-weight, which can be problematic under cyclic loading if the new layer is not properly bonded. Additionally, the enlargement of the section may pose geometric limitations, and the process demands skilled labor for adequate surface preparation (Hong & Lim, 2023; Raval & Dave, 2013; Shabani Attar et al., 2020) Fig. 3 (a) and (b) (Ojaim, 2021) shows the concrete jacket was cast using Self-Compacting Concrete (SCC) following the installation of stirrups for strengthening of the RC beam in shear.

Fig. 3. (a); (b) Details of the concrete jacketing of the RC beam (Ojaim, 2021). (a) (b)

2.3 Externally Bonded (EB) Fiber-Reinforced Polymer (FRP) FRP composites are widely used for retrofitting and strengthening RC beams due to their lightweight properties and corrosion resistance. When externally bonded in forms like U-jackets, side bonding, or full wraps, FRPs significantly enhance shear strength, increase load capacity, and delay crack initiation. Common FRP types include Carbon Fiber Reinforced Polymer (CFRP), Glass Fiber Reinforced Polymer (GFRP), Basalt Fiber Reinforced Polymer (BFRP), and Aramid Fiber Reinforced Polymer (AFRP). However, their effectiveness is often limited by debonding at the concrete interface, leading to premature and brittle failures. To counter this, anchorage systems like mechanical anchors are used to improve bonding. Despite their benefits, FRP systems face challenges in confined spaces and are sensitive to high temperatures, with performance heavily reliant on proper installation and fiber orientation (Abdel-jaber et al., 2025; Kotynia et al., 2021; Lee et al., 2017; Mhanna et al., 2019). Fig. 4 (a) and (b) (Salama et al., 2019) illustrates the performance RC beam externally strengthened on one side in shear using CFRP sheets, with the debonding failure mode observed.

(b)

(a)

Fig. 4. (a); (b) Failure mode of RC beams strengthened with externally bonded CFRP sheets (Salama et al., 2019).

2.4 Near-Surface Mounted (NSM) FRP Technique NSM technique strengthens reinforced concrete by embedding FRP bars, strips, or ropes into grooves filled with epoxy or cement adhesives. Developed to overcome debonding issues of externally bonded FRP, it provides better bond performance and enhanced shear capacity. NSM also offers improved fire resistance, though it requires skilled labor and may face space limitations in congested areas (Abdul Samad et al., 2017; Askar et al., 2022; Ganesh & Murthy, 2019b; Rizzo & De Lorenzis, 2009). This method is demonstrated in Fig. 5 (a) and (b) (Jedrzejko et al., 2023), which displays the failure mode of a T-RC beam strengthened in shear using NSM CFRP strips accompanied by concrete cover separation.