Flexural Behavior of RC Beams Strengthened by CFRP Sheets in the Beams with low and high Reinforcement Ratios

Externally Bonded Reinforcement (EBR) is known as a conventional method for flexural strengthening of concrete beams with Fiber Reinforced Polymer (FRP) composites. The present study has been conducted to investigate the flexural behavior of RC beams strengthened by CFRP sheets. Eight beam specimens strengthened by EBR method having the cross sectional dimensions of 250*300 mm and length of 2200 mm with two different reinforcement ratios (low and high) were evaluated under four point bending test. The compressive strength of four specimens was 25 MPa and other four specimens were made using high strength concrete with the compressive strength of 55 MPa. Additionally, the tensile reinforcement arrangement varied in different specimens with two bar sizes. In order to strengthen the specimens, two CFRP layers with dimensions of 160*1700 were used. Based on the results of the present study, in the case of low reinforcement ratio while maintaining the total reinforcement ratio constant, by decreasing the bar size and increasing the number of bars, the load carrying capacity of the specimen increases. In contrast, in the case of high reinforcement ratio, this results in the decrease of load carrying capacity. Finally, utilizing the smaller bar size in the tensile region of the specimens with low reinforcement ratio results in a more uniform distribution of cracks in the beam.