Comparison of Suspended Zipper Braced Frame and Chevron Braced Frame

Chevron bracing system is prone to buckling of the first story compression brace while the tension one is still at its linear stage of axial behavior. This phenomenon produces an unbalanced vertical force imposed to the top beam leading to concentration of story drifts in one story. Zipper is a vertical member that isadded to brace to beam connections in all stories except the 1st one resulting in contribution of the bracing elements at upper stories to lateral force resistance of the structure. Also, this system leads to moreeconomical section for the 1st story compression brace member and uniform distribution of drifts over the height of the structure. Brittle response is considered as one of the main problems of this system, to avoid which the last story members are strengthened. In this study, this system, referred to as Suspended Zipper Braced Frame, is compared with Chevron bracing system in terms of ductility, economic considerations & drift ratios. For this purpose, three 3-9 and 20 story frames are analyzed using the nonlinear static analysis approach in ABAQUS6.6. The results indicate more ductility and uniform story drifts of the suspended zipper braced frames in comparison with chevron ones in three models and less steel weight for 3 and 9 story frames