A study on comparison of the flexural and flexural-bond behaviour of RC beam using CFRP rod with different surface shape

Abstract

Carbon fibre reinforce polymer (CFRP) exhibits diverse surface shapes and a wide range of tensile strengths compared to those of rebars. CFRP rods in beams require a larger cross section compared to that of RC beams to meet the required anchorage length using the current design standard. The goal of this paper was to compare the flexural and flexural-bond behaviours of CFRP beams with those of RC beams. Four-point flexural tests were performed to examine the flexural and flexural-bond behaviours of CFRP rods with thread-wrapped and sand-coated surfaces, each with distinct characteristics. Additionally, the shear span-to-depth ratio differed between 2.5 and 3.5. The results indicated pseudo-plastic behaviour in the load-deflection curves of the CFRP beams. This behaviour was attributed to the slip due to the reduced bond strength between the concrete and reinforcement, leading to the final failure. Particularly, based on the surface type of the CFRP rods, a cross-sectional design with the maximum load exceeding the design load was realized, even when the CFRP beam failed to satisfy the required anchorage length. These findings suggest that current anchorage length equations may be overly conservative, indicating the need for appropriate adjustments to the design approach.