Abstract
This paper presents the results from Analytical models of a special inverted-V-braced steel frame with zipper struts. Zipper elements are vertical elements added at the intersections of the braces above the first floor and designed to carry upward the unbalanced loads resulting from buckling of the braces. In this study, this system, referred to as Suspended Zipper Braced Frame, is compared with Chevron bracing system in terms of ductility and drift ratios. For this purpose, three zipper-braced models were designed on the basis of the proposed design procedure to carry the same masses as the 4-, 8-, 12-story buildings are analyzed using nonlinear dynamic analysis in Seismostruct. IDA analyses of the models were performed to estimate the overstrength, inelastic strength and deformation capacities for the entire structures, and assess the sequence of yielding and buckling in the members. The analyses indicate that the design procedure produces safe designs, with the design becoming more conservative as the number of stories increases. The distribution of interstory drifts demonstrates the efficiency of the zipper struts in achieving uniform damage over the height of the structure, and generally satisfies allowable interstory drift ratio limits.