Studying the seismic behavior of gate braced frames by incremental dynamic analysis (IDA)

This paper critically evaluates overstrength, ductility and response modification factors of steel frames with gate bracing. Gate bracing system is a kind of concentric bracing systems. It is similar to chevron (inverted V) bracing except that its diagonal members are not straight. The members of different slopes are joined together at a point to provide enough space for openings. In order to achieve the purpose of this research, several buildings of different stories are considered on soil type II. Static pushover analysis, linear dynamic analysis and nonlinear incremental dynamic analysis are performed by OpenSees software concerning 10 records of past earthquakes. Also, ductility factor, overstrength factor and response modification factor have been calculated for gate bracing system. The values of 3.5 and 5 are suggested for response modification factor in ultimate limit state and allowable stress methods, respectively. The fragility curves were plotted for the first time for such kind of braces. It should be mentioned that these curves play significant roles in evaluating seismic damage of buildings. (C) 2014 Elsevier Ltd. All rights reserved.