Comparative Analysis of Seismic Behavior of V-Braced Frames and Suspended Zipper-Braced Frames

Inverted chevron-braced frames (IVBF), notwithstanding their high strength and rigidity, do not exhibit great ductile behavior and proper energy dissipation. To achieve a desirable seismic performance, a new configuration by adding vertical elements to chevron-braced frames is proposed in 1988, so-called zipper-braced frames (ZBF). In these frames, zipper columns connecting the intersection points of the braces above the first story, transfer the vertical unbalanced force due to the buckling of first story compression brace to upper stories and mobilize them to resist this force. This paper presents an analysis of elasto-plastic behavior of suspended ZBF using two design methods, strength based and capacity based, and a pushover analyses of models to determine inelastic strength and advantages of ZBF in comparison with IVBF. Using capacity design, ZBF showed a higher ductility and better energy dissipation with buckling of more braces and lower contingency to collapse due to form soft-story mechanism, whereas they exhibit almost the same behavior as IVBF using strength design.