Seismic retrofitting of existing structures vulnerable to earthquakes is a key issue in any earthquake-prone region. Shape memory alloys (SMAs) show mechanical properties that appear well suited for being used in seismic retrofit. The application basically requires a proper knowledge on the technical details. Behavior factor is one of the major parameters in structural design. It is defined as the ratio of the elastic strength demand imposed on the SDOF system to the inelastic strength demand for a given ductility ratio. Base shear, in current design procedures, is calculated as the elastic strength demand divided by the behavior factor. The objective of this study is to determine the behavior factor for Flag-Shaped (FS) hysteretic models, which are used to describe the seismic response of different structural systems, composed of SMAs. To this end, nonlinear time-history analyses have been carried out using 14 earthquake records relevant to 2 different site-conditions. The maximum seismic response of SDOF systems modelled with a FS model has been derived and compared to that of Elastic-Perfectly-Plastic (EPP) systems. In the analyses, the elastic period of the SDOF system has been varied from 0.1 to 0.8 sec with step of 0.1 sec. Three different values of displacement ductility equal to 2, 3 and 4 have been considered. The results show that the behavior factor of FS models can be expressed as a function of the behavior factor of EPP models, by means of a correction factor which basically depends on the energy dissipation capacity of the FS model.
