Using end buckles to improve debonding resistance in FRP-bonded precracked RC beams

Abstract

The strengthening effect of reinforced concrete (RC) members externally bonded (EB) with fiber reinforced polymer (FRP) laminates is significantly affected by interfacial debonding failure. To improve the connection between FRP sheets and concrete, a novel type of anchor device for FRP sheets called buckle was proposed in this study. This device can effectively lock the end of the sheet using a patented method of wrapping. In addition to conventional external bonding, bolts were installed on the buckles to form hybrid anchored (HA) FRP sheet. To verify the effectiveness of this new method, a precracked RC beam was prepared in comparison with two undamaged beams strengthened with EB or HA FRP sheets. As observed, end buckles can limit the development of cracks regardless of initial cracking. Despite the occurrence of intermediate debonding due to initial cracks, both the ultimate capacity and failure ductility were significantly improved. Owing to the end buckles, the debonding resistance was excellent, and the initial cracking of the beam hardly affected the strengthening effect. In addition, existing formulas were used to calculate the lower limit of the ultimate load of the specimen strengthened with HA FRP, which was still higher than that of the specimen strengthened by EB FRP. Therefore, the results confirmed that the debonding resistance was greatly enhanced due to the locking of the FRP sheet via end buckles, and the proposed method is useful to guarantee the strengthening effect.

Nonlinear bond-slip model for fiber-reinforced polymer laminates externally bonded to thermally damaged concrete

“…Undoubtedly, the use of externally bonded FRP composites to strengthen fire-damaged RC beams and slabs necessitates a comprehensive understanding of the bond-slip behavior at the interface between the FRP laminates and the thermally damaged concrete substrate. Extensive research efforts have been undertaken within the existing literature to explore the bond behavior of FRP-to-concrete bonded joints under normal (undamaged) conditions (e.g., Chajes et al, 1996; Dai et al, 2009; Li et al, 2015; Lorenzis et al, 2001; Mazzotti et al, 2008; Nakaba et al, 2001; Yao et al, 2004; Yuan et al, 2004; Zhou et al, 2023). Furthermore, various bond-slip models have been developed based on experimental results from bonded joint tests to describe the local bond-slip characteristics at the inerface between FRP and concrete (e.g., Dai et al, 2005; Lu et al, 2005a).…”

Dynamic tensile behavior of fiber reinforced materials based on fiber layering modeling

“…As widely accepted, cement-based material is brittle with low ductility and energy-absorbing ability (Li et al, 2023; Mousavi et al, 2019; Wang et al, 2023). Considering of such feature, fiber is often used synchronically to enhance the cracking-resistance/ductility of cementitious materials and improve the load-carrying capacity after crack initiation, which is known as fiber reinforced polymer (FRP) (Nwankwo et al, 2023; Zhou et al, 2023). The merit of FRP is the good resistance against corrosion, which can be functionally used with the marine concrete that usually faces to large amount of chloride ion (Less et al, 2023; Zhu et al, 2023).…”