Performance based assessment of shape memory alloy braces combined with buckling restrained braces in frames subjected to near field earthquakes

Shape memory alloy (SMA) is a relatively new material used in structural engineering. In this paper, responses of braced frames with buckling restrained braces (BRBs) and short-segment SMA braces are investigated. Frame, a six-story structure, is designed according to valid prescriptive codes and then the appropriate nonlinear model is created. Three approaches are examined: The first one is using only BRB in all the stories (BRBF system). The second is using only short -segment SMA braces in all the stories (SMA system). The third approach is combining the BRB and short-segment SMA braces in all stories (COMBINED system). Nonlinear time history analysis (NLTHA) is performed subjected to near field (NF) and far field (FF) record sets at maximum considered earthquake (MCE) and design base earthquake (DBE) levels, and responses of the considered systems are investigated and compared. Results show that none of the three systems is recommended in NF site construction because they exceed the allowable limit state. While, subjected to FF records COMBINED system is a good idea as its responses like maximum inter-story drift ratio, residual drift and brace ductility demand are in an allowable range.