Performance of RC beams strengthened with self-prestressed Fe-SMA bars exposed to freeze-thaw cycles and sustained load

Abstract

Iron-Based Shape Memory Alloys (Fe-SMA) have been recently used by researchers as a strengthening material for Reinforced Concrete (RC) beams. This material is relatively inexpensive compared to the traditional Nickel Titanium SMA (NiTi-SMA), which makes it feasible for large-scale structural engineering applications. The Fe-SMA is mainly characterized by the Shape Memory Effect (SME) phenomenon, which allows the material to recover the induced deformations through heating. When the pre-strained Fe-SMA bar/strip is anchored on the tension side of an RC beam using the Near-Surface Mounted (NSM) strengthening technique and is then heated to the activation temperature, a tension force (prestressing force) develops in the material, which results in enhancing the flexural capacity of the RC beam at service and ultimate load conditions. This paper investigates the long-term performance of RC beams strengthened with NSM Fe-SMA bars and exposed to severe freeze–thaw cycles and sustained loading. The results revealed that the strengthened beam was superior in flexural performance compared to the un-strengthened beam, and there was minimal degradation compared to other beams tested at room temperature.