Shear strengthening of slender reinforced concrete T-shaped beams using iron-based shape memory alloy strips

Abstract

[eng] Recent research works have shown the feasibility of using iron-based shape memory alloys (Fe-SMAs) in structural rehabilitation projects, especially for flexural strengthening. As for the shear strengthening of reinforced concrete (RC) beams with SMAs, most previous works have used small-scale members. This paper presents an experimental campaign involving eight tests run with real-scale RC beams. The total length of the beams was 5800 mm, and their T-shape cross-section was 550 mm deep. External strengthening was done using Fe-SMA strips with a U-configuration. Strips were characterized before being used for the strengthening application. The key results are herein presented. All the beams failed in shear. Tests showed an increase of around 30% in the shear strength of the retrofitted beams versus the reference beams, and flexural capacity was practically reached. For service loads, active strengthening was useful for delaying the appearance of cracks and reducing their widths. However, the U-configuration used for the strips implied having to anchor them to the web, which probably weakened the flange-web connection and impeded the correct transfer of the tensile stresses between the longitudinal tensile reinforcement and the compression flange, which resulted in less ductile behavior than expected.