Afram Keivani - Professor of Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran.
Mehdi Azizi - MSc of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran.
Farhad Alizadeh Afshar - MSc of Civil Engineering, Azarshahr Branch, Islamic Azad University, Azarshahr, Iran.

The unexpected failure of steel structures during past strong seismic excitation led to full fill adequate strength for modern structures in seismic areas. Concentrically braced frame (CBF) structures provide high stiffness and moderate ductility, while they are prone to damage concentrated within a single floor. To overcome this drawback, researchers have proposed to add a vertical member to the CBF system, labeled a zipper column , with the aim to involve the buckling and/or yielding of several braces. Thus, the zipper column members are designed to transfer the unbalanced forces caused by buckling of braces in chevron configuration along the building height. By employing the zipper braced frame system (ZBF), the damage is more uniformly distributed over the height. Also as a consequence, the results showed that zipper struts can improve the seismic performance of CBF system

Concentrically braced frame, Inverted V-braced frame, Zipper column, Seismic behavior