Applications of shape memory alloys in structural engineering

Shape memory alloy (SMA) is a type of alloy that is able to recover its original shape by either the application of high temperature (known as shape memory effect) or through removal of the applied stress (known as superelasticity). These effects would result in several unique characteristics, such as Young's modulus-temperature relations, superelastic effects, shape memory effects, large damping capacity, and re-centering capabilities. These characteristics would lead to a high ductility of structural members and a large energy dissipation capacity without leaving significant permanent deformations. Hence, SMAs were beneficial in the seismic resistance of structures by implementing the material in dampers, braces, connectors, isolators, etc. Over the past few decades, different innovative devices and systems, mainly implementing NiTi-and Cu-based alloys, were developed and tested to dissipate the earthquake energy and reduce the seismic forces acting on structures. SMAs were integrated within these systems in different configurations, such as single wires, stranded wires, strips, ribbons, tubing, and rebars. The objective of this paper is to provide a state-of-the-art review of the unique properties of SMA as a smart material and their applications in the field of structural engineering, and in particular, earthquake engineering. The paper discusses the advantages and drawbacks of the material, as well as the different studies that investigated the effectiveness of SMA for new construction and retrofit of existing structures.