The Effects of Height and Length of Link Beam on Response Modification Factors of Eccentrically Braced Steel Frames

Response modification factor is one of the seismic design parameters to know the nonlinear performance of building structures during strong earthquakes. As such, relying on this factor, many seismic design codes lead to reduce the structural loads. The current paper tries to evaluate the response modification factors of conventional eccentric braced frames (EBFs). Since, the response modification factor depends on ductility and overstrength, the static nonlinear analysis has been performed on building models including type three length of link beam, with 3, 5, 7 and 10 stories and with different brace configurations (open chevron invert V and open diagonal bracing), Further, the linear dynamic and incremental nonlinear dynamic analysis was performed on building models under San Fernando, Cape Mendocino and Northridge strong ground motions for modification of the nonlinear static analysis results. The results indicated that the response modification factors for open diagonal eccentric braced frames were higher than the open chevron eccentric braced one. It was also found that the length of link beam and the height of buildings have had greater effect on the response modification factors.