Experimental Investigation of the Flexural Strengthening of Fixed-Supported RC Beams
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RESEARCH PAPER
Experimental Investigation of the Flexural Strengthening of FixedSupported RC Beams Yaser Alhamdan1 • Tamer Dirikgil1 Received: 1 December 2019 / Revised: 25 May 2020 / Accepted: 2 June 2020 Ó Iran University of Science and Technology 2020
Abstract The performances of seven full-scale, fixed-supported reinforced concrete (RC) beams were investigated with the fourpoint bending test in this study. One of the RC beams was a reference beam (Ref) and six were strengthened beams. The strengthening of the RC beams was performed with near surface mounted (NSM), external bonded reinforcement (EBR), friction hybrid bonding (FHB), and hybrid techniques. Steel bars, CFRP bars, CFRP sheets, and mechanical fastener systems were used in the strengthening processes, according to the requirements of the applied techniques. The experimental results were evaluated for the effects of strengthening techniques and materials on the load–deflection response, ultimate load-carrying capacity, ductility, dissipated energy, failure modes, strain, and crack pattern. Strengthening applications using the NSM technique, with conventional steel, increased the load-carrying capacity of the RC beams by 22–24.9% while increasing their total energy dissipation by 40.7–68.9%. The load-carrying capacity was increased by 3.7–11.9% in RC beams strengthened by CFRP sheet and CFRP bar. However, except for the FHB technique, CFRPapplied RC beams could not perform the inelastic behavior. The FHB strengthening technique increased the load-carrying capacity and total energy dissipation of the beam by 11.6% and 21.2%, respectively. The results showed that NSM-Steel, NSM-Steel/90, and FHB-CFRP techniques quite improved the performance of the RC beams for both the elastic and plastic regions, while both of EBR-CFRP and Hybrid-CFRP techniques improved the elastic behavior of the RC beams to a great degree. Keywords Fixed-supported RC beam NSM strengthening EBR strengthening Friction hybrid bond Hybrid technique List of Symbols a Concentrated load distance from the face of the support or shear span Af Cross-section area of FRP sheet As Tension rebar area at the cross section As,min Minimum reinforcement area at the cross section Asp Cross-section area of the plate bw Beam width dimension c Neutral axis depth CE Environmental reduction factor CFRP Carbon fiber reinforced polymer d Effective depth of the beam db Diameter of the strengthening bar & Tamer Dirikgil [email protected] Yaser Alhamdan [email protected] 1
Department of Civil Engineering, Erciyes University, 38280 Talas, Kayseri, Turkey
df dp EBR Ec Ef Es Esp f c’ ffe ffu ffu* FHB fs fsp fy fyp h km ln M
Effective depth of FRP reinforcement Effective depth of steel plate External Bonded Reinforcement Elasticity modulus of concrete Modulus of elasticity of FRP laminates Elasticity modulus of steel rebar Elasticity modulus of steel plate Characteristic compressive strength of concrete Effective stress on FRP Ultimate tensile
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