Effectiveness of Fan Anchors in Preventing Debonding in FRP-Strengthened Steel Members

Abstract

Fibre Reinforced Polymers (FRPs) are extensively employed to strengthen existing structures because of their several advantages over other strengthening techniques. On the other hand, the premature debonding of FRP reduces its effectiveness in strengthening steel structures. Anchoring FRP composites is an effective solution to delay or even prevent their debonding. Very limited anchorage methods, however, have been introduced for FRP-strengthened steel structures and the need for an effective anchorage system remains. Fan anchor has been validated as one of the remedies against debonding failure in FRP-strengthened concrete structures. Considering the advantages that fan anchors offer, the use of fan anchors for FRP-strengthened steel structures is proposed and evaluated in this paper. Since FRP-steel joints have a different bond-slip law than FRP-concrete joints and the strengthened steel members are prone to buckling-debonding interactions, this study focuses on the efficiency of fan anchors in delaying FRP debonding by assuming that an adequate mechanical connection between the dowel and the steel substrate is provided. Three experimental studies involving shear, flexural and buckling strengthening of steel components were simulated through finite element modelling, and fan anchors were added to the models after validation. The effect of fan anchors on strength, failure mode and FRP's strain distribution of the models was examined. The study showed that the fan anchor was successfully able to delay debonding mode, which increased the strength and ductility and exploited a higher strain capacity of FRP plates.

Experimental and Numerical Investigation of the Behavior of Steel Beams Strengthened by Bolted Hybrid FRP Composites

“…Researchers continuously investigate solutions to overcome the brittle interfacial debonding by exploring the chemical properties of the adhesives and by studying the effects of the bond length, adhesive thickness, and curing time on the performance of the bonded FRP-steel system [7][8][9]. Various confinement methods were adopted to delay debonding of the FRP from the steel beams [10][11][12][13]. Moreover, numerous research studies have investigated the behavior of steel beams strengthened by hybrid bonded-anchored techniques, where end anchors were introduced at the ends of the bonded FRP composites to prevent end debonding.…”

On the Numerical Modelling of Steel Beams Strengthened by Purely Fastened FRP Sheets

“…Numerous research was conducted on bonded FRP-steel joints to assess the effects of the bond length, adhesive thickness and chemical composition on the bond behavior of the bonded system [5,6]. Several end-anchorage techniques were used companioned with the bonding process in attempts to delay the de-bonding failure [7][8][9][10]. Despite the effectiveness of the bonding technique in improving the load capacity of the rehabilitated steel beams, de-bonding of the adhesive generally controls the failure of the bonded system and risks its ductility [2,3].…”

Performance of FRP-Steel Joints and FRP-Steel Beams Fastened by FRP Anchors

“…Several investigations were conducted to analyze the behavior of the bonded FRP-steel joints and beams considering various types and layouts of FRP composites, epoxy adhesives, bond length and bond thickness [1], [3], [4]. Recently, researchers are proposing various end-anchoring techniques to avoid/delay the de-bonding failure that governs the behavior of the bonded technique [5][6][7][8][9][10]. Additionally, the bonded FRP composites were combined with shape-memory-alloys (SMA) in an attempt to enhance the performance of bonded FRP-steel elements [11,12].…”