Flexural behavior of concrete beams reinforced by CFRP bars

Flexural test results of three concrete beams reinforced with carbon fiber-reinforced polymer (CFRP) bars together with a steel-reinforced beam which is served as a reference are presented and discussed. All beams were tested under third-point loading, and each of them was 3 meters long with a 200 × 300 millimeters cross section. Test results have showed the load-deflection curve of a CFRP-reinforced concrete beam under loading normally exhibits two stages, namely elastic and cracked-elastic stages. While the load-deflection curve of a steel-reinforced concrete beam exhibits three stages, namely elastic, cracked-elastic and plastic stages. The transition from the first to the second stage is caused by the development of cracks at the bottom of the beam. As of cracking pattern, cracks in the pure bending zone and its immediate vicinity appeared in quick succession in CFRP-reinforced beams, and on formation, they immediately penetrated deep towards the compression side of the beam. In addition, three kinds of deformability models for FRP concrete beams, which were suggested by different investigators in recent years, are used to evaluate the deformability of the test beams. Of the three CFRP concrete beams, the beam which positioning the longitudinal tensile CFRP bars into 2 layers and placing circular heliced stirrups in compression zone gives the largest deformability capacity.