Effect of carbon-fiber-reinforced polymer laminate configuration on the behavior of strengthened reinforced concrete beams

This paper presents test results of 18 small-scale reinforced concrete specimens of strengthened beams using carbon-fiber-reinforced polymer (CFRP) composites. The specimens were instrumented with strain gauges in a region where cracks in the concrete were preformed to monitor the variation of strains throughout testing. Results indicate that there can be a very large variation in the measured strains in the composites depending, not only on the location of the cracks, but also on the configuration used to bond the composites to the surface of the elements. The interface shear stresses generated at failure of the beams are compared with two existing analytical models. Additionally, the stress level in the composites was determined for all the strengthened specimens from the experimental data. The calculated stress in the composites reached between 20 and 43% of the CFRP rupture stress. The information presented in this paper provides information that can be used to validate or modify current design procedures of strengthened beams using composites.