Behavior of Zipper Braced Frame (ZBF) compared with other Concentrically Braced Frame (CBF)

Abstract

In this study the Behavior of Zipper Braced Frame (ZBF) is investigated and compared with Concentrically Braced Frame (CBF). In order to ensure the systems behavior in a stable manner, different concentrically braced configuration has been studied. The frame has the same geometry as the conventional Chevron braced frame except a vertical structural element, the Zipper column, is added at the beam mid-span point from the second to the top story of the frame. To evaluate this new system Opensees software are used to model different two dimensional frames with Zipper brace. These frames are analyzed under pushover and cyclic conditions and their ductility, drift and internal forces of the members are compared with each other. Analyses show the formation of plastic hinges in higher stories, and the participation of all braces in dissipation of seismic forces. The analyses verify the reduction of mid-point deflections of beams in the braced system as well as improvement of ductility and response modification factor in comparison to the other concentric braces.