An Investigation on Bracing Configuration Effects on Behavior of Concentrically Braced Steel Frames

3 Abstract: Concentric bracing systems, because of their effectiveness in reducing seismic response, have been in practice for many years. Depending on concept, seismic design codes provide various response modification factors (R) for different types of lateral load bearing systems but configuration of these systems are often ignored in the proposed values. This study aims at considering the effect of different bracing configuration on the relative values of R. Six five-story three-bay braced frames with three different patterns and one-third scale have been made and experimentally evaluated. On the grounds of experimental results, 27 models were created and analyzed using Finite Element Analysis. The main variables of this study were the location of bracing, bay width and height of story. Results show that configuration of bracing system can affect the R values. Based on analyses and experiments, best results obtained when adjacent bays are braced. Furthermore a relation is presented to predict relative R value depending on bay to width ratio in each category.