Effect of seismic resistance capacity of moment frames on progressive collapse response of concentrically braced dual systems

Abstract

In this study, the effect of seismic force resistance capacity of moment-resisting frames on progressive collapse response of dual systems was discussed to find the most appropriate and cost-effective way to distribute seismic forces to moment frames and braced frames of dual systems. In this way, it is possible to make a proper design that simultaneously leads to a robust structure under both progressive collapse loads and seismic loads. Thus, the progressive collapse resistance of concentrically braced dual systems with three different seismic force resistance shares of the steel moment frames, namely 25, 50 and 75% was investigated. Two different bracing types, including X and inverted V braces, were considered in different seismic hazard sites. The nonlinear static alternate path method recommended in the Unified Facilities Criteria guideline is used to assess the progressive collapse performance of model structures. These studies showed that an increase in the seismic force resistance share of moment frames in dual systems resulted in a more robust structure against progressive collapse when the moment frame subjected to column loss. However, this was reduced when a braced column was removed. Using greater seismic force resistance share for moment frames led to an increase in cross-section of structural elements of moment frames, and it led to higher progressive collapse resistance of moment frames. As a result, an increase in the seismic force resistance of the moment-resisting frame up to 50% is recommended as a proper and economic seismic force distribution for dual systems that are prone to progressive collapse in moment frame column loss scenarios.