Framing Strategies for Enhanced Robustness in Steel Buildings

This paper describes the use of stiff-story framing to increase robustness in steel buildings subjected to column loss. Two case study buildings were designed; building A features a perimeter moment frame structure, while building B utilizes chevron-braced frames. The lateral-force-resisting systems (LFRSs) and stiff stories of these two prototype buildings were then modified to create different configurations in order to study which configurations were more robust. A linear static alternate path analysis was performed for each of the configurations, and the effectiveness in resisting column loss was determined. Based on the results from the analyses, two indices that quantify vulnerability and framing efficiency were developed that can be used by designers to evaluate framing alternatives. Cost and aesthetic considerations were explored as well. Evaluation of alternative configurations shows that tying the stiff story into the LFRS and supporting all exterior columns with the stiff-story framing will increase system robustness.