Shear Strength of Externally U-Bonded Carbon Fiber-Reinforced Polymer High-Strength Reinforced Concrete

Abstract

In this paper, we investigate the contribution of Fiber-Reinforced Polymer (FRP) to the load-carrying capacity of shear-strengthened Reinforced Concrete (RC) beams. Specifically, the investigation is focused on the FRP’s contribution in the presence and absence of shear stirrups. To this end, two sets of full-scale RC beam specimens were tested to failure in a simply supported setup. Set 1 consisted of specimens without shear stirrups whereas Set 2 included steel stirrups spaced at 170 mm. One and two layers of FRP discrete strips were bonded to the beams in a U-jacketing configuration. To investigate the contribution of FRP and its interaction with the stirrups, two different locations were considered when bonding the FRP strips: between the stirrups (referred to as Off-beams) and at the same level of the stirrups (referred to as On). Results of the experimental program showed that strengthening the beams with two layers of FRP does not necessarily translate to improved capacity. Furthermore, the location of FRP strips with respect to the location of shear stirrups has an influence on the beam’s overall behavior, especially its displacement ductility. This is an important parameter to consider to avoid premature failure of RC members. Test results were then used to assess the performance and accuracy of the predictions of ACI PRC-440.2-17 and fib-TG9.3. Both design codes were found to be conservative with an average prediction-to-test ratio of 0.7.

Shear performance of reinforced concrete beams strengthened in shear using NSM bars and reinforced HSC layers

“…Furthermore, the strengthened timber beams with CFRP composites increased their shear capacity by 32.9% and 68.6% for one and two layers, respectively. 17 Conversely, GFRP strips improved timber beams' shear capacity, stiffness, and ductility by 41%, 62.05%, and 3.5%, respectively. 25 One of the most significant difficulties associated with using EB-FRP was the early debonding of the bonded sheet, which prevented the full use of the EB-FRP capability.…”

“…Moreover, the total efficiency of BFRP sheets in improving shear capacity was 20% larger than GFRP sheets. Furthermore, the strengthened timber beams with CFRP composites increased their shear capacity by 32.9% and 68.6% for one and two layers, respectively 17 . Conversely, GFRP strips improved timber beams' shear capacity, stiffness, and ductility by 41%, 62.05%, and 3.5%, respectively 25 …”

“…The FRP was extensively investigated as a fast‐developing strengthening approach for defective structures in the form of EB‐FRP sheets 13,16–24 . The shear retrofitting of the deep beams with GFRP layers could delay the initiation of the shear cracks while the shear capacity enhanced as the GFRP layer increased 18 .…”

“…The FRP was extensively investigated as a fastdeveloping strengthening approach for defective structures in the form of EB-FRP sheets. 13,[16][17][18][19][20][21][22][23][24] The shear retrofitting of the deep beams with GFRP layers could delay the initiation of the shear cracks while the shear capacity enhanced as the GFRP layer increased. 18 The anchorage technique prevented the GFRP sheet from debonding and improved the shear capacity of the shear-upgraded beams.…”

A Review on Bond Performance of FRP-Concrete System at Various Environmental Conditions

“…Different types of FRP are utilized in the strengthening [6][7][8] and variety of FRP installation techniques [9] are exist and the two most popular FRP strengthening systems are externally bonded (ES) and near-surface mounted (NSM) strengthening techniques. ES is the more utilized method due to its practicality to strengthen different shapes and sizes of concrete structures [10][11][12][13]. Epoxy-based adhesive (EBA) is the commonly used bonding agent in ES technique.…”