Seismic Response of Eccentrically Braced Frames

This study deals with eccentrically braced frames with a view: (1)To define situations in which end moments in the bracing members dominate over axial forces and vice versa; and (2)to study their seismic response with different member proportions. It is concluded that in eccentrically braced frames, end moments dominate over axial forces for bracing members of slenderness ratio of the order of 50 or less, end moments and axial forces are equally important between 50 to 120, and buckling dominates for slenderness ratio more than 120. There is a need to develop a hysteresis model that would account for axial as well as flexural inelasticity in steel members. It is also noted that strong-girder/weak-column combination produces significant flexural inelastic activity in the columns whereas with weak girders the inelastic activity can be confined to girders alone or distributed among girders and bracing members.