Self-Prestressing Using Iron-Based Shape Memory Alloy for Flexural Strengthening of Reinforced Concrete Beams

The behavior of reinforced concrete beams strengthened with nearsurface-mounted (NSM) iron-based shape memory alloy (Fe-SMA) bars was studied. Because there were no jacking tools used to apply the prestressing force, this technique was called self-prestressing. The prestrained Fe-SMA bar was anchored inside a precut groove at the tension side of the RC beam (2000 x 305 x 150 mm [78.7 x 12.0 x 5.9 in.]). The bar was then activated through heating above 300 degrees C (572 degrees F), causing a prestressing force in the bar. The beam was then tested under four-point bending setup to failure. The results revealed a significant increase in the yielding and ultimate load capacities. Unlike the prestressed FRP strengthening techniques, the ductility of the beam was significantly improved due to the yielding nature of the Fe-SMA material.