Seismic performance of cable zipper-braced frames

Zipper elements of stories transfer unbalanced vertical forces of the lower stories to the upper ones. The tensile forces generated in these elements extremely increase in upper stories. Accordingly, these zipper elements need an impractically large cross-section to be designed. This problem induces some limitations on the use of zipper bracing systems, especially in high-rise buildings. Therefore in this study a novel approach is presented to resolve this problem. The proposed solution is using cables with appropriate pre-stress ratios as zipper elements. Accordingly, the seismic behavior of cable zipper-braced frames with different pre-stress ratios is investigated. For this purpose, nonlinear time history (NLTH) analyses were conducted on several structural models with different numbers of stories. Comparison of the obtained results with those of conventional suspended zipper-braced frames (SZBF) demonstrates the efficiency and viability of the new technique. Moreover it is shown that use of the suggested system with appropriately pre-stressed cables enhances the seismic performance of zipper-braced systems.

► A new bracing system called “cable zipper-braced frame” was proposed.
► In this system high-strength pre-stressed cables were used as zipper elements.
► Appropriately pre-stressed cable zipper elements, improve the performance of SZBFs.