CFRP sheets for flexural strengthening of RC beams

Based on the use of carbon fibre reinforced polymer (CFRP) and the technique of externally bonded reinforcement strengthening arrangement to flexural strengthen of reinforced concrete (RC) beams. A total of 7 RC beams with different cross section depth, the longitudinal reinforcement ratio, the pre-crack width and the concrete cover thickness were constructed and tested under four-point bending load. The objectives of this study are to examine the flexural strengthening capacities of retrofitted RC beams, and to investigate how different layers of CFRP sheets affect the RC beams strengthened. Externally bonded CFRP flexural strengthening was found very effective in upgrading the flexural strength of RC beams. The strength gain caused by the CFRP sheets was in the range of 41-125%. The stiffness of the beams strengthened is improved more obviously on beam with more longitudinal reinforcement ratio, and that the stiffness is not significantly influenced by the concrete cover thickness. A theoretical calculation on estimating the flexural carrying capacities of the beams tested is presented and compared with the experimental results.