Shear strengthening of RC beams with NSM FRP. I: Review of strength models

Abstract

Near-surface mounted (NSM) fiber-reinforced polymer (FRP) technique is known as a promising alternative to the externally bonded (EB) FRP technique for strengthening reinforced concrete (RC) members, on account of its many advantages such as high bond efficiency with concrete and good durability. Shear strengthening of RC beams by near-surface mounting the FRP bars/strips into the concrete cover on beam sides is one of the most prevalent applications of NSM FRP. Abundant experimental studies have been conducted to investigate the behaviour of NSM FRP shear strengthened beams, and many strength models for predicting the contribution of NSM FRPs to the shear capacity of the beam have been proposed. The present paper presents a comprehensive review of these strength models, in which all the models collected from the existing literature are first classified into three categories based on their used approach and then summarized and discussed. This paper not only aims to bring a deep understanding of the existing strength models for NSM FRP shear strengthened RC beams, but also provides a background and basis for the assessment of these models by using the newly-generated experimental database in the companion paper.

Shear strengthening of RC beams with NSM FRP. II: Assessment of strength models

“…The comparisons are presented in order of the classification of these models, which is consistent with that in the companion paper (Jedrzejko et al, 2022).…”

“…Beam code was reviewed in the companion paper (Jedrzejko et al, 2022). In the simplified version, a safety factor was considered in the model, resulting in conservative predictions as shown in Fig, 8.…”

“…Table A1 contains the geometrical details, mechanical properties and failure modes of all the specimens. Table A2 summarizes the shear capacities of specimens failed in shear as well as the NSM FRP shear contributions from tests and predictions by the strength models reviewed in the companion paper (Jedrzejko et al, 2022).…”

“…Tables 1-4 summarize the statistical characteristics of the experiment-to-prediction ratios of contributions of NSM FRPs to the shear capacities of strengthened beams for the ten design-oriented strength models (De Lorenzis and Nanni 2001; Parretti and Nanni 2004; Kotynia 2007; Islam 2009; Rizzo and De Lorenzis 2009; Singh et al, 2012; Dias and Barros 2013; Bianco et al, 2014; Perera et al, 2014; Mofidi et al, 2016) reviewed in the companion paper (Jedrzejko et al, 2022). These statistical characteristics include the average, standard deviation (SD), coefficient of variation (CoV), and percentage of exceedance (PoE).…”

“…To develop a reliable design theory of NSM FRP for shear strengthening of RC beams, a strength model that can accurately predict the contribution of NSM FRPs to the shear capacity of strengthened beam is essential. In the first of these two companion papers (Jedrzejko et al, 2022), a total of 12 strength models (De Lorenzis and Nanni 2001; Parretti and Nanni 2004; Kotynia 2007; Islam 2009; Rizzo and De Lorenzis 2009; Singh et al, 2012 Dias and Barros 2013; Bianco et al, 2014; Perera et al, 2014; Mofidi et al, 2016; Chen and Cheng 2019; Bui and Stitmannaithum 2020) for NSM FRP shear strengthened RC beams have been reviewed and classified into three categories based on their used approaches: (1) effective strain/stress-based models (Kotynia 2007; Islam 2009; Singh et al, 2012; Dias and Barros 2013); (2) debonding-based models (De Lorenzis and Nanni 2001; Parretti and Nanni 2004; Rizzo and De Lorenzis 2009; Bianco et al, 2014; Mofidi et al, 2016; Chen and Cheng 2019; Bui and Stitmannaithum 2020); and (3) parametric analysis-based model (Perera et al, 2014). Among these models, Chen and Cheng’s (2019) model is an analysis-oriented model for calculating the shear contribution of NSM FRPs on the premise of a known load of the beam.…”