Design of Zipper Column in Inverted V Braced Steel Frames

摘要

Inverted V (or chevron) braced steel frames have been seen as being prone to soft story response once the compression brace buckles under earthquake loading. To salvage chevron braced frames, the concept of the zipper column was proposed many years ago such that the zipper column can redistribute the inelastic demand over the height of the building. However, it appears that a rational design method for the zipper column has not been established yet. In this paper, a simple static design was first presented, and then a dynamic design method which can consider the effects of the brace slenderness and higher modes was proposed by combining the refined physical theory braced model and the modal pushover analysis. Inelastic dynamic analysis showed that both the static and dynamic design methods proposed in this study result in significantly improved seismic performance as compared to the case without zipper column. The simple static design method proposed to invoke at least two-story buckling mechanism equally worked well in this limited case study.