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

Abstract

This paper introduces a novel and simple model for estimation of the shear contribution of the fiber-reinforced polymer (FRP) strengthening system in the FRP-strengthened beams. The model utilizes the bonding-based approach, which considers the shear resisting mechanism of FRP-strengthened beam via the bond behavior between FRP strengthening system and concrete. Herein, the beams strengthened in shear with near-surface mounting (NSM) rods or laminates and embedded through-section (ETS) bars are examined. By utilizing only mechanical consideration, the shear resistances of the NSM-strengthening or ETS-strengthening laminates or bars in the beams are simply derived when several bond factors (i.e. maximum bond stress and slip at peak bond stress) are known without using any empirical coefficients. The reliability of the proposed model is first validated against the test results available in the open literature. The extensive investigation to complement the model validation is then carried out through comparison of the results produced by the experiments and the proposed approach as well as the existing methods. The analyses demonstrate that the bondingbased approach is greatly effective to predict the shear contribution of the FRP strengthening system in the beam. Two examples for calculation of the shear resisting forces of the ETS-FRP and NSM-FRP bars in the FRP-strengthened beams are provided to depict the use of the model.

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

“…De Lorenzis and Nanni 2001; Nanni et al, 2004; Barros and Dias 2006; Kotynia 2007; Rizzo and De Lorenzis 2007; Rahal and Rumaih 2011; Dias and Barros 2012, 2013, 2017; Jalali et al, 2012; Singh et al, 2012; Wiwatrojanagul et al, 2012; Barros et al, 2016; Mofidi et al, 2016; Kuntal et al, 2017; Al Rjoub et al, 2019; Prabhakaran and Joseph 2019; Abdel-Jaber et al, 2021; Alwash et al, 2021; Saadah et al, 2021) and numerical studies (e.g. 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) have been conducted and presented. These studies have proved the effectiveness of NSM FRP bars/strips in enhancing the shear capacity of RC beams.…”

“…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.…”

“…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. Bui and Sitimannaithum’s (2020) model needs an additional bond joint test to determine the NSM FRP-concrete interfacial bond-slip relationship. Therefore, Chen and Cheng’s (2019) model and Bui and Sitimannaithum’s (2020) model are both unable to be directly used for predictions.…”

“…Bui and Sitimannaithum’s (2020) model needs an additional bond joint test to determine the NSM FRP-concrete interfacial bond-slip relationship. Therefore, Chen and Cheng’s (2019) model and Bui and Sitimannaithum’s (2020) model are both unable to be directly used for predictions. The other 10 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) are all design-oriented and capable of giving predictions on the contribution of NSM FRPs to shear capacity of strengthened beam, with the necessary information of NSM FRP shear strengthened RC beam being provided.…”

Конечно-Элементный Анализ Железобетонных Балок, Упрочненных U-Образными Обмотками Волокнисто-Армированного Углепластика

“…В связи с тем, что мода разрушения и конструкционные характеристики поврежденных балок могут существенно отличаться от расчетных в силу уменьшения площади поперечного сечения как в бетоне, так и в арматуре, а также уменьшения прочности сцепления между бетоном и арматурой [19,20], они особенно чувствительны к сдвиговому деформированию. В [21][22][23][24][25] рассмотрели несколько аналитических подходов, учитывающих внешнее приклеивание ВАПМ, для оценки сопротивления упрочненных железобетонных балок сдвиговому деформированию. Применение U-образных обмоток из ВАПМ -одна из наиболее популярных схем упрочнения в силу таких преимуществ, как сдвиговое упрочнение и анкерное воздействие.…”