Numerical evaluation on collapse-resistant performance of steel-braced concentric frames

Abstract

Steel-braced concentric frames (SBCFs) are a popular form of structure and has been widely employed in seismic regions owing to their high strength and elastic stiffness; however, the effects of key parameters on the collapse behavior of SBCFs are unclear due to insufficient investigations, which should be further explored in column removal scenarios. To this end, numerical models were employed to explore the key parameters affecting the collapse behavior of SBCFs in this study. The numerical models of steel frames with or without braces were validated based on previous experimental results. According to the refined model, the effects of brace members of various types and with different slenderness ratios on the collapse behavior were illustrated. The results showed that an X brace type with smaller slenderness ratio is the most appropriate for enhancing robustness against progressive collapse. Thereafter, full-scale numerical models were established to investigate the effect of the column removal position, and the results showed that the frame relied purely on flexural action in a side column loss. Moreover, the effect of the position of horizontal brace layers on the collapse behavior was investigated in the middle and side column removal scenarios. To gain deeper insight into the load-resisting mechanisms, the specific contributions to the total resistance of different mechanisms in different stories, bare steel frames and braces, and tensile and compressive braces were separated. Finally, a strategy for the robustness enhancement of high-rise steel frames was empirically proposed, and it was suggested that the provision of a brace layer for approximately every 10 stories would be effective for the anti-collapse design of high-rise buildings.