Parametric study on modification factor of steel moment resisting frame associated with Gate bracing system

Nowadays, the use of braced frames in steel buildings is one of the popular methods as a resistant system against earthquake forces. In recent years, a form of bracing that is called "Gate Bracing System," for providing enough space for opening trough architecture viewpoint, has been issued and using from Dual moment frame or resistant frame by this kind of brace can be useful. In contrast, the Codes have not recognized this system formally yet and have not been done detailed research on this system performance and seismic responses, based on non-linear analyses. One of the essential structures seismic responses against the earthquake forces is the modification factor; R is explanatory of the ability of the structural system to dissipate earthquake energy and creation of non-linear deformation without collapse of the structure. At first, in this study, calculation of the overstrength factor has been done. Then the ductility factor and modification factor of moment resisting frame whit Gate Bracing System are calculated. To do it, non-linear static analysis, have been used, and studies have been done on frames with 4, 8,12, and 15 stories and contain three kinds of bracing mood by the use of "sap2000" software; however, for an estimate of sections of frames is used from Etabs version 9.7.1. Afterward, the seismic performance of this system was studied under two seismic loading patterns, p mode and uniform, by use of results of 12 frames with 4, 8, 12, and 15. Finally, the value of behavior factor, equal to 6.75 for design in the ultimate limit state method and equal to 9 for allowable stress design methods have been suggested. Also, in this study, it has been shown that with an increase in the height of structures, the structure modification is decreased.

کلیدواژه ها:

Gate Bracing System ، Non-linear Static Analysis ، Modification Factor