Repair and strengthening of shear-deficient reinforced concrete beams using Carbon Fiber Reinforced Polymer

Abstract

This paper presents the results of an experimental investigation on the behavior of Reinforced Concrete (RC) beams repaired and strengthened using Externally Bonded Carbon Fiber Reinforced Polymer (EB-CFRP). The experimental program involved 19 static tests on 16 simply supported rectangular RC beams in which seven were tested without CFRP and 12 were wrapped with one or two layers of CFRP. Out of the 12 beams, six were first tested to failure, repaired with epoxy, then wrapped with CFRP sheets before the second and final test. The remaining six were wrapped with CFRP, while virgin, before testing. Among the objectives of this study was the analysis of the effectiveness of EB-CFRP as a strengthening method for shear strengthening of damaged RC beams and the identification of interaction between conventional shear reinforcement and the EB-CFRP strips. Analysis of test results suggests that the EB-CFRP strengthening of damaged beams repaired using epoxy injection not only helps the beams to recover but also significantly increase their shear capacity. Moreover, one layer of CFRP discrete strips improved the overall capacity of the shear-deficient beams by more than 60% and an additional layer further increased the shear capacity by another 30%. The results also confirmed that an interaction exists between steel stirrups and EB-CFRP strips when carrying the applied load. For instance, test results demonstrated that the contribution of CFRP in shear strength is affected by the quantity of steel stirrups. Finally, when compared to test results, the ACI and fib formula provided reasonable estimation of the additional shear strength contributed by the EB-CFRP discrete strips, except for the beams with moderate ratio of steel stirrups. However, Chen et al. model better estimated the EB-CFRP contribution to the shear capacity of RC beams with moderate ratio of steel stirrups.