Comparative study of effective stresses of concrete beams strengthened using carbon-fibre-reinforced polymer and external prestressing tendons

In this study, the load-carrying capacities of reinforced concrete (RC) beams strengthened with carbon-fibre-reinforced polymer (CFRP) and external tendons were compared. The effective stress of the RC beams was estimated by analysing the experimental reinforcing effect and the resulting behaviour of each specimen. It was found that the strengthening effect of CFRP was affected by the initial damage in the RC beams. On the other hand, in external post-tensioning, application of strain induced an initial effective stress in the RC beams. As a result, the effective stress of these RC beams was reduced and their performance was improved. Furthermore, it was found that the strengthening effect of external tendons used to strengthen in-service RC beams can be predicted by a finite element analysis.