Ductility characteristics of concrete frames reinforced with superelastic shape memory alloys

Self-centering structural systems are getting attention due to their ability of reducing damage and repair expenses due to earthquakes. A portion of recent research initiatives on self-centering is focused on utilizing superelastic shape memory alloys (SMAs) as reinforcement in concrete frames. SMAs have large strain capacity, energy dissipation ability and self-centering behavior. However, they also have various disadvantages that have to be addressed when studying their applicability as reinforcement in concrete frames. This paper evaluates the seismic performance characteristics of SMA reinforced concrete (RC) frames by performing a series of static pushover and dynamic earthquake analyses on typical framed structures. The performance parameters considered include the initial lateral stiffness, the energy dissipation capacity, the ductility ratios and the residual deformations both at the cross-section level and at the structure level. The results of this study show that SMA RC systems are characterized with excellent recentering behavior and poor levels of ductility ratio and energy dissipation ability. They exhibit higher levels of flexibility and fundamental periods in comparison with steel-reinforced systems. For specific level of ductility ratio, the base-shear demands on SMA RC systems are expected to be much higher than those on steel RC systems.