Masoud Mahdavi - Ph.D. Student, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran
Abbas Babaafjaei - M.Sc. Student, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran
SeyyedReza Hosseini - M.Sc. Student, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran
Bamdad Aghababaei Mornani - M.Sc. Student, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran
Mohsen Tavakoli - M.Sc. Student, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

The passive control of the structure with bracing system is one of the new methods of structural engineering. Indicators such as the span length and the story height have important effects on the steel structure performance during an earthquake. Determining the relationship between various geometric indicators and the seismic performance of structure leads to better design and reduction of damages during an earthquake. In the current research, a ۵-story steel frame with Gate brace was designed with Sap۲۰۰۰ software. The K index was defined as the ratio of the span length to the story height. Three different values of K equal to ۱, ۲ and ۳ were defined in the modelling of the structure. The structures were analyzed by the modal time history analysis method under the accelerometers of Kobe (near-fault) and El Centro (far-fault). The results showed that in the near-fault area, Modal damping energy and base shear force have a direct relationship with the K index. The mentioned ۲ seismic parameters, in the far-fault area, do not have a clear relationship with the K index. Also, parameters such as acceleration, roof displacement, brace axial force, story displacement, column shear force and the support reaction force do not have a clear relationship with the K index in the near-fault and far-fault areas.

Gate Brace, NEAR-FAULT, Far-fault, Modal Time History Analysis, seismic parameters