Testing of concrete elements with internal shape memory alloy spirals

In recent years, an innovative concrete confinement technique using shape memory alloys (SMAs) has emerged. The new technique utilises active confinement, which is proven to be more effective than traditional passive confinement in improving the strength and ductility of concrete. However, most of the previous research on this technique has focused on retrofit/repair applications of circular concrete elements by applying external SMA spirals or ties. This paper presents an experimental study on implementing this new confinement technique using SMA spirals as internal transverse reinforcement in newly constructed square columns. In this study, short, square, concrete columns are designed and constructed with internal longitudinal steel rebars and internal transverse reinforcement. One of the concrete columns is designed with internal SMA transverse spirals, while two other columns are constructed using traditional transverse steel reinforcement for comparison. Experimental results demonstrate that, compared to the traditional steel transverse reinforcement, SMA spirals effectively delay the longitudinal rebar buckling and significantly reduce strength degradation.