Experimental study on shear strengthening of shear critical RC beams using iron-based shape memory alloy strips

•A low-cost iron-based shape memory alloy (Fe-SMA) strip is fully characterized.•Fe-SMA is used for externally strengthening small-scale shear critical concrete beams.•An increase on the shear strength of the RC beams is demonstrated.•The failure mode changed from shear to flexural due to the external strengthening.•The Compression Chord Capacity Model was able to predict the shear strength. Shape memory alloys (SMAs) have been introduced into structural engineering in recent years. This paper presents research results about developing a new methodology to actively strengthen reinforced concrete (RC) beams by low-cost iron-based SMA strips (Fe-SMA). These strips can transversally prestress, or confine, the cross-section of beams thanks to the shape memory effect of Fe-SMA, without having to apply prestressing force. Activation of strips is carried out by heating them up to 160 °C and then cooling them. An experimental campaign was carried out at two levels: characterization of Fe-SMA strips, and the practical application of the strengthening technique on small-scale beams without internal stirrups. The retrofitted beams with activated strips failed by bending, and the appearance of shear cracks was clearly delayed. Meanwhile, the reference beams failed due to shear.