Flexural behavior of GFRP-RC beams confined with CFRP in compression zone

Abstract

In this study, the CFRP sheets and CFRP stirrups are employed to confine the compression zone in GFRP-reinforced concrete (GFRP-RC) beams to improve the ductility of the beams. Four-point bending tests are conducted on four CFRP sheets and six CFRP stirrups confined GFRP-RC beams. The cracking bending moment, crack width, mid-span deflection, bearing capacity, and ductility of all the beams are analyzed. Results show that the effect of the confinement in the compression zone on the cracking bending moment and crack width under service load can be ignored. The cracking bending moment can be accurately estimated using ACI 440.11–22, while the GB50608–2020 standard provides an accurate prediction for the crack width under service load. The GFRP-RC beams confined with CFRP stirrups exhibit mid-span deflections reaching up to 95 mm prior to failure. In addition, the CFRP stirrups confinement is more effective compared to CFRP sheets confinement due to the poor bond performance between the CFRP sheet and concrete. Furthermore, an accurate equation for the calculation of bearing capacities of GFRP-RC beams confined with CFRP sheets and stirrups has been proposed. It has also been demonstrated by this study that significant improvements in the ductility of GFRP-RC beams can be achieved by confining the compression zone. Deformation ductility factors of all the beams are analyzed to support this conclusion.