Behavior of reinforced concrete T-beams strengthened in shear with carbon fiber-reinforced polymer - An experimental study

This paper presents results of a wide and extensive experimental investigation on reinforced concrete (RC) T-beams retrofitted in shear with externally bonded carbon fiber-reinforced polymer (CFRP). In total, 22 tests were performed on 4520 nun-long T-beams. The parameters investigated were as follows: 1) the CFRP ratio (that is, the number of CFRP layers); 2) the internal shear steel reinforcement ratio (that is, spacing); and 3) the shear length to the beam's depth ratio, a/d (that is, deep beam effect). The main objective of the study was to analyze the behavior of RC T-beams strengthened in shear with externally applied CFRP by varying the aforementioned parameters. The results showed that the contribution of the CFRP to the shear resistance is not in proportion to the CFRP thickness (that is, the stiffness) provided, and depends on whether the strengthened beam is reinforced in shear with internal transverse steel reinforcement. Results also confirmed the influence of the ratio a/d on the behavior of RC beams retrofitted in shear with external fiber-reinforced polymer (FRP). Finally, comparison of the shear resistance values predicted by ACI 440.2R-02, CSA S806-02, and fib TG9.3 guidelines, with the test results clearly indicated that the guidelines fail to capture important aspects, such as the presence of the transverse steel and the ratio a/d on the one hand, and overestimates the shear resistance for high FRP thickness (and hence high FRP stiffness), on the other.