Shape Memory Alloy (SMA) connection in the Precast Concrete Shear Wall

One of the most common lateral force-resisting systems in mid-rise and high-rise buildings is reinforced concrete shear walls. In addition to resisting earthquake and wind loads, shear walls also support gravitational loads. Under strong earthquake shaking, these shear walls are designed for life safety, where the building can endure heavy damage. Past earthquakes have shown that buildings designed for this criterion underwent severe damage, particularly in mid-rise and high-rise reinforced concrete structures. The post-earthquake repair and retrofit of these buildings are expensive or uneconomical. Therefore, shear walls should be designed to minimise damage to these structural elements, resulting in low or no permanent deformation in the buildings. One alternative is to use superelastic Shape Memory Alloy (SMA) bars at the critical locations (plastic hinge regions) of the shear walls instead of typical steel reinforcing.

SMA is an innovative material that has a superelastic property. This material can return to its initial shape and position after removing the loading on the structure. The SMA demonstrates superelasticity behaviour when it is in the austenite state. In addition to the superelasticity property, SMA has a very low or negligible residual strain after unloading. Moreover, SMA can dissipate substantial energy during repeated load cycles. Therefore, SMA material has significant potential for civil engineering applications to make structures seismic-resistant in earthquake-prone areas.