An experimental and numerical study of the effect of thickness and length of CFRP on performance of repaired reinforced concrete beams

Experimental and numerical analyses are performed to predict the loading carrying capacity of reinforced concrete beams strengthened with carbon fibre reinforced plastics (CFRP) composites. The effect of CFRP thickness and length on the failure load and ductility is studied and curves of initial cracking load, ultimate load, stiffness, ductility and fibre stresses are presented. The results of tests and simulations show a good agreement and indicate that, in contrast with a control beam, initial cracking loads of strengthened beams increase slightly, whilst stiffness and ductility increase more and the ultimate loads increase considerably. Stresses in the carbon fibre decrease with the increase of fibre sheet thickness. Cracking patterns of strengthened beams are improved. Crack propagation varies with the change of fibre length and results in the variation of failure mode of beams. Variation of the length of CFRP sheet is the main reason of variation of the stress of interface. Therefore, debonding failure, unless adequately considered in the design process, may significantly decrease the effectiveness of the strengthening.