Structural Seismic Applications of Shape Memory Alloys: A Review

Shape memory alloys (SMAs) are metallic materials that possess superelastic properties and can undergo large deformations. There are mainly two types of SMAs that are commercially available in the market: NiTi-based alloys and Cu-based alloys, with the first being the most common. SMAs have the ability to return to their pre-deformed state through heating or stress removal due to a phase change in the material. Such service-mechanical properties are commonly known as shape memory effect, superelasticity, and hysteretic damping. SMAs are also known to have high-cycle fatigue resistance, corrosion resistance as well as high strength. Superelastic SMAs undergoing cyclic loading experience austenite–martensite phase transformations in its hysteresis. During the phase change, the elastic properties of the SMA increase. Through building and design, research and use of shape memory alloys have started to become more prevalent, including applications in structures located in seismic regions. The objective of this paper is to provide an overview of the applications of shape memory alloys in seismic-force-resisting elements of buildings and bridges in seismic regions. Several studies suggest that SMA technology significantly enhances the resistance to seismic loads and improves life cycle performance in structures. This makes SMA a promising alternative to conventional reinforcing steel since from the history of past earthquakes, civil infrastructures built across the world have proven to be susceptible to significant damage. Although the cost of SMA is higher compared to conventional construction material, implementing it into the structural design will resist drastic permanent deformations from seismic related activity and could prove to be beneficial considering the life cycle cost of the structure. Considering its superior self-centering property, there are many opportunities to investigate the use of SMA’s in civil structures in seismic regions.