A Laboratory Study on the Flexural and Shear Behavior of RC Beams Retrofitted with Steel Fiber-Reinforced Self-compactin
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RESEARCH PAPER
A Laboratory Study on the Flexural and Shear Behavior of RC Beams Retrofitted with Steel Fiber‑Reinforced Self‑compacting Concrete Jacket Iraj Rahmani1 · Ahmad Maleki1 · Mohammad Ali Lotfollahi‑Yaghin2 Received: 25 February 2020 / Accepted: 11 November 2020 © Shiraz University 2020
Abstract In this research, the behavior of RC beams retrofitted with steel fiber-reinforced self-compacting concrete jacket (SFRSCC-J) is investigated. For this purpose, by constructing 25 different beams, flexural load-carrying capacity of beams retrofitted with different concrete jackets is examined. The variables studied are the type of concrete (conventional and self-compacting), the strength grade of concrete (C40, C50, and C60), and the presence or absence of reinforcement bar and steel fiber in the jacket. The beams were subjected to three-point flexural loading, and the response was evaluated in terms of load–displacement diagrams. The results show that by adding SFRSCC-J to the perimeter of the beams, their bearing capacity can be increased up to about 7.4 times to reach the yield load, and about 5.1 times to reach the ultimate load. Moreover, the combination of steel fibers (SFs) and steel rebar reduced the cracks more, and at the final moment, the cracks extended to the neutral axis of the cross-section. In the retrofitted beams with the combination of rebar and SFs, the bonding between the reinforcement and the concrete increased and the reinforcement bars slipped less into the specimen. Thus, with a better distribution of stress, besides the concentration of the cracks in the middle of the span, the diagonal cracks decreased, and as the load increased, crack lengths increased less. Keywords Steel fiber · Retrofitting · Concrete jacket · Self-compacting concrete · Flexural toughness · Crack distribution
1 Introduction In the past two decades, great emphasis has been put on the repair and retrofitting of structures around the world given the erosion of infrastructure and the need for strengthening structures to meet stringent design requirements. Moreover, the seismic improvement of the structures, especially in earthquake-prone areas, has become so significant (Ilki et al. 2004; Tahsiri et al. 2015; Osman et al. 2016; Negro * Ahmad Maleki [email protected] Iraj Rahmani [email protected] Mohammad Ali Lotfollahi‑Yaghin [email protected] 1
Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
2
and Mola 2017; Seifi et al. 2017). Therefore, strengthening buildings using reliable, easy, fast, and economical methods is very important. Strengthening of buildings is done to increase either structural strength or structural ductility. In the first method, the strength of the structure is improved by adding shear walls or steel braces. In the second method, the rapid failure of the main members is prevented by using new techniques (Chalioris et al. 2014; Dubey and Kumar 2016; Panjehpour et
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