Experimental Study on Shear Strengthening of Reinforced Concrete Box Beam by CFRP
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RESEARCH PAPER
Experimental Study on Shear Strengthening of Reinforced Concrete Box Beam by CFRP Shengqiang Ma1 · Norazura Muhamad Bunnori2 · Kok Keong Choong3 Received: 11 January 2019 / Accepted: 17 April 2020 © Shiraz University 2020
Abstract Numerous theoretical and experimental studies have been conducted on fiber-reinforced polymer (FRP) shear strengthening rectangular and T-section beams; however, few researches focused on box beam, which is widely used in bridge superstructures. This paper presented experimental study on shear strengthening reinforced concrete (RC) box beam by carbon-fiberreinforced polymer (CFRP) with four common strengthening patterns. The CFRP strengthening schemes, failure modes, deflection, and effective strain in fibers were investigated and recorded. As for CFRP shear contribution, it showed best performance with a 52.7% increase for the specimen with a continuous U-jacket sheet. Besides, all the strengthened RC box beams exhibited the debonding of CFRP strips or sheets in the ultimate state. It was found that the maximum strains in fiber recorded from strengthened specimen were approximately 3000με accounting for 17% of the ultimate strain of CFRP sheet. The model in fib Bulletin 90 was used to predict CFRP shear contribution in the strengthened specimen, but it overestimated the values compared with experimental results because of higher effective strain calculated by model. A coefficient of 1.31 was therefore proposed for the equation of effective strain in the model, and the calculated CFRP shear strength by fib Bulletin 90 combined with modified effective strain was in good agreement with the experimental values. Keywords Box beam · Reinforced concrete · Shear strengthening · Carbon-fiber-reinforced polymer (CFRP) · Effective strain
1 Introduction In the past two decades, by immersing continuous fibers in resin matrix bonding fibers, fiber-reinforced polymer (FRP) composites have gradually replaced steel plates for use in retrofitting reinforced concrete (RC) members (AbdelJaber et al. 2003). Methods for strengthening beams with * Shengqiang Ma [email protected]; msq‑[email protected] Norazura Muhamad Bunnori [email protected] Kok Keong Choong [email protected] 1
School of Architectural and Civil Engineering, XinJiang University, Xinjiang 830000, China
2
Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
3
School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia
FRP materials have been broadly accepted and employed worldwide. FRP materials provide an ideal combination of mechanical and physical characteristics, such as high tensile strength, lightweight, high fatigue strength, non-corrosion, easy formability, and remarkable long-term durability. Furthermore, easy installation of FRP system benefits from the properties of formability and being lightweight. As an outstanding choice for external reinforcement, FRP materials can provide corrosion immunity and are com
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