Shear behavior of large-scale T-shaped RC beams strengthened with iron-based shape memory alloy (FeSMA) prestressing

Prestressing generated by iron-based shape memory alloys (FeSMA) has been proven to be effective in increasing the flexural and shear capacity of reinforced concrete (RC) beams. However, studies on the shear strengthening of RC beams using externally mounted FeSMA are still limited. Particularly, the experimental data on large-scale T-shaped beams have been lacking. This paper compares the behavior of large-scale shear critical T-beams strengthened with externally mounted FeSMA strips with that of traditional RC T-beams. The influence of the spacing and number of layers in the external FeSMA strips, and the presence and spacing of internal stirrups were investigated. The crack patterns, failure modes, shear force versus deflection curves, and strains in the external FeSMA strips and internal stirrups were analyzed and discussed. The shear capacity of T-beams strengthened with FeSMA strips was analytically calculated using the strain measurements in the FeSMA and internal steel stirrups. The results demonstrated that both the peak shear force and deflection at peak shear force of the beams strengthened with FeSMA increased compared to the control RC beam. Specifically, a 32% to 55% increase in the peak shear force, and a 30% to 62% increase in the deflection at the peak shear force were attained for beams strengthened with FeSMA. One of the control RC beams was repaired after failure, and it was found that 90% of the peak shear force could be recovered through application of external FeSMA reinforcement. The results presented in this paper confirmed the effectiveness of using FeSMA strips for strengthening or repair of shear critical RC beams.