Retro-fitting of external unbonded reinforcement as a mean of strengthening concrete beams deficient in flexural strength has been investigated in a short programme of experimental and analytical research to evaluate the potential of the technique. External unbonded reinforcement offers significant advantages in ease of installation over alternative strengthening techniques for simply supported beams. This paper reports results from a series of tests to examine the influence of three parameters, namely loading arrangement, effective depth of external reinforcement, and geometric ratio of bonded reinforcement, on structural behaviour of beams strengthened using the technique. Beams strengthened with external unbonded reinforcement showed improved serviceability behaviour. The study showed that increases in flexural capacity of up to 85% could be attained by retro-fitting of external reinforcement, albeit with some reduction in ductility. The paper quantifies the changes in performance attributable to external unbonded reinforcement, and the influence of the parameters studied on those changes. © 1997 Elsevier Science Ltd.
- External reinforcement