c © Imperial College Press EARTHQUAKE PERFORMANCE OF STEEL FRAMES WITH NITINOL BRACES

In this paper, the seismic performance of a three- and a six-storey steel frame equipped with different bracing configurations is assessed. The bracing systems consist of tra-ditional buckling-restrained steel braces and superelastic Nitinol shape-memory alloy (SMA) braces. Background on the behaviour of SMAs is provided and a state-of-the-art review of the applications of such new materials in earthquake engineering is presented. A uniaxial constitutive model for superelastic SMAs is then implemented into the finite element platform OpenSees and nonlinear dynamic analyses are performed. Finally, the seismic performance of the structures under investigation is judged through the evalua-tion of several response quantities, to determine the efficacy of the new bracing system in reducing earthquake-induced vibrations