Evaluation of the Maximum Strain for Different Steel-FRCM Systems in RC Beams Strengthened in Flexure

Abstract

The strengthening of existing reinforced concrete (RC) structures by means of steel-fabric reinforced cementitious matrix (Steel-FRCM) systems has been universally recognized in the academic literature as an effective method. Several types of steel fibres can be found in the marketplace, and they are classified according to mass per unit area and tensile strength. In the flexural strengthening design of RC beams, a fundamental parameter is the effective tensile strain level in the Steel-FRCM system attained at failure. Some authors and guidelines suggest evaluating this strain value using the results of bond tests. As is well highlighted in many works, the debonding strain in Steel-FRCM composites applied on concrete beams is usually higher than that from single-lap shear tests. At this point, it can be easily obtained by applying an appropriate amplification coefficient. This study experimentally investigates the difference in the debonding strain between Steel-FRCM composites bonded to concrete blocks in single-lap shear tests (end strain) versus the debonding strain in concrete beams (intermediate strain). The results were used to critically discuss the variability of the amplification coefficient, significantly affected by the mechanical and geometrical properties of the steel fibres. Moreover, a simple predictive formula to evaluate the intermediate strain debonding was used, and the results were compared with the experimental evidence. Finally, a large database of direct shear and flexural tests was used to confirm the experimental and theoretical data obtained herein.

Flexural behaviour of RC one-way slabs reinforced using PAN based carbon textile grid

“…Ebead et al (2019) observed that RC beams strengthened using one or two layers of PBO fabric failed to fabric slippage whereas, failed due to delamination of layers when three layers of strengthening were adopted. This similar phenomenon was also observed by Elsanadedy et al (2013); Bencardino and Nisticò (2022). Besides Elsanadedy et al (2013) also compared the ductility response of FRP and TRM (basalt-based textile) strengthened RC beams wherein the ductility of TRM strengthened beam was found to be superior to the FRP strengthened beam.…”

“…In international literature, there are a substantial amount of research articles on the strengthening effect of TRM in reinforced concrete (RC) beams (Loreto et al, 2015;Qaidi et al, 2022a;Bencardino and Nisticò, 2022). Loreto et al (2015) evaluated the performance of RC beams strengthened using Fabric reinforced cementitious matrix (FRCM) in shear zone in the form of U-wraps.…”

“…The experimental and analytical results indicated that increase in the shear capacity of the FRCM strengthened beam was not proportionally to the number of placed fabric layers and FRCM failure modes were found to be dependent on the amount of external reinforcement. Similarly, Bencardino and Nisticò (2022) also investigated the behaviour of different Steel-FRCM beams in direct shear and flexure. Two different unidirectional steel fibres were used namely, stainless steel and galvanized high strength steel.…”

“…Besides Elsanadedy et al (2013) also compared the ductility response of FRP and TRM (basalt-based textile) strengthened RC beams wherein the ductility of TRM strengthened beam was found to be superior to the FRP strengthened beam. Therefore, strengthening of RC beams using different types of textile reinforcement systems has shown a potential enhancement in flexural capacity accompanied by a reduction in deflection magnitude as well as crack width (Bencardino and Nisticò, 2022).…”

The Influence of Ply Stacking Sequence on Mechanical Properties of Carbon/Epoxy Composite Laminates

“…Thus, industries such as automotive, aerospace, architecture and marine are continuously exploring the potential of this material [6,7]. In civil engineering, fibre-reinforced polymer composites (FRPs) are used in reinforcing bars, sandwich panels and structural retrofitting [8,9]. However, due to the organic nature of the matrix, FRPs are impermeable to vapour, they are flammable and their application on a wet surface at low temperatures is not readily achievable.…”