Title:
Performance of Reinforced Concrete T-Girders Strengthened in Shear with Carbon Fiber-Reinforced Polymer Fabric
Author(s):
Omar Chaallal, Mohsen Shahawy, and Munzer Hassan
Publication:
Structural Journal
Volume:
99
Issue:
3
Appears on pages(s):
335-343
Keywords:
ductility; reinforced concrete; shear; strain; strength.
DOI:
10.14359/11917
Date:
5/1/2002
Abstract:
This paper presents results of an experimental investigation on the performance of 20 ft long reinforced concrete (RC) T-girders strengthened in shear using epoxy-bonded bidirectional carbon fiber-reinforced polymer (CFRP) fabric. The main objective of the study was to evaluate and gain insight into the effectiveness of shear strengthening of large-scale girders with externally bonded CFRP under a low shear span condition. The study considered four series of tests corresponding to the following four stirrup spacings: 5.5, 8, 16, and 24 in. Each series of girders included control specimens with no CFRP wrap and specimens retrofitted in shear with one, two, and three layers of CFRP wrap. Results showed that for unwrapped specimens, the values for nominal shear predicted by ACI underestimated, by 40 to 80%, the shear resistance of beams developing arch action, such as those considered in this study. For wrapped specimens, the maximum shear force as well as the midspan deflection generally increased with the number of CFRP layers. The optimum number of layers to achieve the maximum gain in shear resistance was found to depend on the internal shear steel reinforcement provided. The effective CFRP strain used to calculate the contribution of the CFRP to the shear capacity was correlated to the total shear reinforcement ratio consisting of steel stirrups and CFRP wrap. Retrofitting RC girders in shear with CFRP wrap also increased the ductility. The experimental evidence indicates that an optimum combination of CFRP layers and steel stirrups exists for a maximum increase in ductility.