Flexural behavior of reinforced concrete beams externally strengthened with ECC and FRP grid reinforcement

Abstract

To prevent premature delamination of FRP sheets in strengthened concrete structures, this study explores a novel method of laying a composite layer of fiber reinforced polymer (FRP) grid reinforced with engineering cementitious composite (ECC), designated as FGRE, and applied at the soffit of reinforced concrete (RC) beams to improve its flexural performance. Experimental studies were conducted on RC beams with different strengthening configurations to validate the effectiveness of the proposed strengthening method. In addition, analysis on the working mechanism and a parametric analysis were performed for the composite strengthened beam using nonlinear finite element modeling. The experimental results showed that FGRE composite layers can significantly improve the bearing capacity of RC beams. Compared with the control RC beam, the FGRE composite strengthening technique significantly increased the cracking load, yield load, and ultimate load of the beam specimens up to 28, 11, and 12 %, respectively. The ECC grout layer maintained a good bonding performance with the concrete substrate until beam failure. The flexural capacity of RC beams with the proposed FGRE strengthening systems is determined by the thickness of the ECC layer. In addition, the effect of strengthening on the flexural capacity was more significant when the yield and tensile strength of the steel reinforcement were lower. Moreover, the prediction deviation from the experimental data of the FE models and analytical models for the ultimate load-bearing capacity were less than 2 and 7 %, respectively. It can be concluded that the proposed FGRE system is a viable solution to enhance the flexural capacity of RC beams.