Simulation of Concrete Beams Strengthened by Embedded Through-section Steel and GFRP Bars with Newly Developed Bond Model

Abstract

This paper presents an experimental and numerical investigation on concrete members strengthened by embedded through-section (ETS) steel and glass fiber-reinforced polymer (GFRP) bars attached preferably with mechanical anchorage at the tension ends. The pullout tests to analyze the bond performance between ETS bars and concrete under various influences such as anchorage presence, embedment length, ETS bar diameter, ETS-material types, and anchorage length are carried out. An analytical method for deriving the local bond stress-slip relationship of GFRP barsconcrete interfaces is developed. The overall responses of the pullout test specimens in terms of pullout force-slip curves, failure modes and strain profiles along the embedment length are discussed. Based on a careful interpretation, the analytical results demonstrated the effectiveness of the local bond stress-slip model developed in this study. Additionally, the finite element (FE) simulation of the beams intervened with ETS bars, which were tested in a previous study by the authors, incorporating with the proposed interfacial model is conducted. Comparison between the results achieved from the FE modelling and the experiment implies that the FE method was an accurately applicable tool to assess the behaviors of the beams strengthened in shear by ETS bars.

Prediction of Shear Contribution for the FRP Strengthening Systems in RC Beams: A Simple Bonding-based Approach

“…(7). As reported in Bui et al (2020c)'s study, when the embedment lengths of ETS bars are shorter than 180 mm, it affects the bond strength. In this study, the average bond lengths derived by Eq.…”

“…6(d), the slip at the anchored end was assumed to be zero as a boundary condition. Actually, it is explained by Bui et al (2020aBui et al ( , 2020c, the anchored end at x = 0 (mm) was strongly constrained by the anchoring nuts [as demonstrated in Fig. 6(d)].…”

“…The mechanical anchorage system could compensate for the bonding deficiency. Currently, there are a number of studies investigating the bond behavior of the ETS or NSM retrofitting system to concrete through pullout tests and bending tests (Nakaba et al 2001;Lorenzis and Nanni 2002;Teng et al 2006;Soliman et al 2011;Coelho et al 2015;Godat et al 2012;Caro et al 2017;Bui et al 2020aBui et al , 2020c. Those researches assessed the bond stress-slip relationship, modes of failure and bond strength under various effects such as the bonded length, concrete strength, FRP size and property.…”

“…Additionally, they employed the linear and bilinear constitutive laws for defining the bond response of EB FRP sheets to concrete, which was a crucial part of their proposed shear strength model. However, the linear and bilinear relationships have not gained the reasonable reliability for expressing the interfacial mechanism between ETS/NSM FRP and concrete (Lorenzis and Nanni 2002;Bui et al 2020c). Owing to the adoption of many variables and procedures, the model of Kamiharako et al (2001) has not widely been used in the open literature.…”

Effects of the bond properties of ETS‐GFRP bar to concrete on the shear behavior of ETS‐GFRP‐strengthened RC beams

“…The key efficiency of the ETS strengthening was to enhance the member performance in capacity and ductility compared with the other strengthening methods, as evidenced by Chaallal et al 3 Embedding the FRP composites at the width center and through section increased the confinement action and mitigates the premature debonding of ETS‐FRP bars to concrete 24,28 . The numerical research by means of finite element method (FEM) on the behavior of the ETS‐strengthened beams was conducted by Godat et al, 29 Breveglieri et al, 27 and Bui et al 30,31 These authors proved the reliability of the FE models by comparing and verifying with experimental results.…”