Evaluation of collapse-resistance of special truss moment frames as per FEMAp695 approach

Special Truss Moment Resisting Frame (STMF) is one of the lateral force-resisting systems in which the input seismic energy is allowed to dissipate at the predefined special regions of the steel truss members. Past studies have shown that STMFs designed based on the prescriptive force-based design method recommended by the current codes as well as the performance-based plastic design (PBPD) method have shown to achieve the desired performance levels in terms of the target drift and yield mechanisms under Design-basis earthquake (DBE) hazard level. However, there is a need to evaluate their collapse-resistance potential of such systems under the extreme earthquake loading conditions. In this study, the collapse performance of a mid-rise nine-story STMFs designed based on the current code (ASCE) procedure as well as PBPD method has been investigated in accordance with the FEMAp695 recommendations. The collapse margin ratio computed for both ASCE and PBPD STMFs using the nonlinear incremental dynamic analyses under the amplified levels of seismic hazards has been compared with the recommended values. Finally, a progressive collapse analysis has been conducted for the PBPD STMF to investigate its load redistribution potential under a column-removal scenario.