Experimental Study of the Influence of Adhesive Properties and Bond Length on the Bond Behaviour of NSM FRP Bars in Concrete

Abstract

The near-surface mounted (NSM) fibre reinforced polymer (FRP) technique is a relatively recent system for strengthening concrete structures. Bond is a key factor in its behaviour, and is affected by many factors whose influence can only be tested through experimental studies. In this study, the modified pull-out test was used to study the effect of epoxy properties and bond length on the behaviour of NSM FRP bars. Three epoxy types, two FRP materials (carbon and glass) and four bond lengths (6db, 12db, 24db and 30db) are used. The load capacity, slips at the loaded end and free end and average bond stress are all analysed. The test results indicate that the role of epoxy properties appear to be a key factor in bond performance in the NSM FRP strengthening technique, and that their effect varies depending on bond length and FRP properties.

Crack Width and Load-Carrying Capacity of RC Elements Strengthened with FRP

“…One of the most advantageous material types for strengthening is fibre-reinforced polymers (FRP) due to their corrosion resistance and high strength to low weight ratio [1][2][3][4][5]. Anticorrosion properties are particularly relevant in aggressive environments, for example, bridge structures [6].…”

Characterization and Simulation of the Bond Response of NSM FRP Reinforcement in Concrete

“…The bond mechanisms generated in the NSM FRP technique can lead to several types of failure modes, which are mainly influenced by the bonded length, FRP surface and shape, groove configuration, materials mechanical properties and adhesive properties [22,23]. In general, the failure modes can be grouped into three main categories: failure at the FRP-adhesive interface, failure at the epoxy-concrete interface, and adhesive cover splitting [1].…”

“…Moreover, in NSM strengthening systems, it has been observed the activation of a friction component for relatively large slips as an extension of the softening branch [1,14,[17][18][19]. The presence of a friction branch has been also reported in the bond behavior of other strengthening materials as fiber reinforced cementitious matrix composites (FRCM) [20,21].The bond mechanisms generated in the NSM FRP technique can lead to several types of failure modes, which are mainly influenced by the bonded length, FRP surface and shape, groove configuration, materials mechanical properties and adhesive properties [22,23]. In general, the failure modes can be grouped into three main categories: failure at the FRP-adhesive interface, failure at the epoxy-concrete interface, and adhesive cover splitting [1].The global bond stress-slip performance of an NSM FRP strip bonded to a concrete block is the result of the local bond-slip behavior at every point along the bonded length, which can be considered the constitutive model characterizing the bond behavior of the NSM FRP element.…”

Predicting Crack Spacing of Reinforced Concrete Tension Members Using Strain Compliance Approach With Debonding

“…In general, experimentally obtained bond behaviour of reinforcement can vary with the dimensions of specimen, detailing of reinforcement, and the testing configuration (Balázs, 1993;Torres, Sharaky, Barris, & Baena, 2016;Carvalho, Miranda, Fernandes, & Alves, 2018). There is no universally applicable bond-slip law to ensure favourable results of crack analysis for a broad range of geometrical, materials and loading characteristics of RC elements (Rehm, 1961) but only applicable to limited range of RC elements (Jakubovskis, Kaklauskas, Gribniak, Weber, & Juknys, 2014).…”