Seismic performance of a reinforced concrete building retrofitted with self-centering shape memory alloy braces

In recent years, a new generation of seismic lateral force resisting systems has been proposed that sustains little or no damage under severe earthquakes thus reducing the repair time and cost. This has stimulated the development of many types of self-centering (SC) earthquake-resistant systems even based on innovative materials. Among them, shape memory alloy (SMA) dampers have been proposed that use superelastic nitinol wires to dissipate energy and self-center the structure. Many studies have been dedicated to SMA-brace devices applied to steel moment frames. Only a few studies have employed these devices for the seismic retrofit of existing reinforced concrete buildings. Moreover, their applicability has been experimentally and numerically tested only on small scale brace-components, while applications to real RC buildings are still lacking. Finally, there is a general lack of reliable design procedures. This paper presents a study that investigates the seismic performance of a reinforced concrete building retrofitted with self-centering (SC) shape memory alloy (SMA) braces. A design procedure is applied that satisfies displacement-based performance criteria and allocates the damped braces over the height according to an optimal damper distribution rule. Finally, nonlinear response-history analyses are carried out to evaluate the effectiveness of both the self-centering retrofit solution and the design procedure. The results show the excellent recentering behavior of the SC-SMA braces together with their not negligible energy dissipation capacity.