Progressive collapse resisting capacity of moment frames with viscous dampers

In this paper, the effect of viscous dampers on reducing progressive collapse potential of steel moment frames was evaluated by nonlinear dynamic analysis. Parametric studies were conducted first to evaluate the effects of dampers installed in a steel beam-column subassembly with varying natural period and yield strength on the reduction of progressive collapse potential. Then 15-story moment-resisting frames with three different span lengths were designed with and without viscous dampers, and the effect of viscous dampers was investigated by nonlinear dynamic analysis. According to the parametric study, the vertical displacement generally decreased as the damping ratio of the system increased, and the dampers were effective in both the elastic and the elasto-plastic systems. It was also observed that the effect of the damper increased as the natural period of the structure increased and the strength ratio decreased. The analysis results of 15-story analysis model structures showed that the viscous dampers, originally designed to reduce earthquake-induced vibration, were effective in reducing vertical displacement of the structures caused by sudden removal of a first-story column, and the effect was more predominant in the structure with longer span length.