محمدرضا خيمه

One of the most popular lateral load resistant systems is the concentric bracing frame. Despite the unique advantages of the system, it has irregular and unstable hysteresis rings because of differences in compression and tensile strength. Hence, many research has been done to upgrade these braces to achieve an ideal elastoplast behavior and a symmetric hysteresis curve. Which has resulted in the construction of Buckling-restrained braced . Buckling-restrained braced, although having a much better seismic performance than ordinary bracing, have a roughly similar behavior to conventional braces to produce large nonlinear displacements due to their low stiffness and consequently prone to soft story. Recently, a strongback system, a combination of zip systems and an elastic truss system, has been introduced. Strongback system actually involves two types of features is resistant system in which a conventional braced frame with a mast combined. This system prevents or delay the behavior of the soft story by controlling the distribution of floor grabs and the nonlinear demand of the structure. In this research, the seismic performance of the Strongback system has been evaluated in comparison with the Buckling-restrained braced and since existing research is limited to the behavior of this type of system under the main earthquake, in this research, the performance of Seismicity of this system under seismic sequence is also examined to provide a better understanding of the effectiveness of this system to increase the stability of Buckling-restrained braced frame. For this purpose, in this research, three structures of 4, 8 and 12 floors of two Strongback and Buckling-restrained braced systems have been designed and developed under nonlinear static analysis , nonlinear time history analysis and Incremental dynamic analysis. In this study, for comparing two systems of seismic parameters such as behavior coefficient, coefficient of formability and over strength coefficient, structural responses including maximum relative displacement and residual relative displacement and fracture curves at different levels of performance Used. The results of this study show that the Strongback system has a uniform distribution of displacement at the height of the structure, which prevents the formation of soft story. Also, with the increase in the survival rate of the seismic, the effect of the seismic sequence phenomenon on both systems has increased. an‎d this effect has increased with increasing number of story. The results indicate that the Strongback system has better seismic performance for short and medium structures.