Performance-Based Design of Steel Moment Resisting Frames Using Alternate Path Method (APM) For Progressive Collapse Mitigation

Abstract

Progressive collapse refers to a severe structural failure mechanism in which the local loss of one or more primary load-carrying members triggers a chain reaction of failures, resulting in damage that is disproportionate to the initiating event. Improving the robustness and overall safety of structures against such events has led to the growing use of performance-based design methodologies.

The present study investigates the progressive collapse behaviour of steel moment-resisting frames (SMRFs) through a performance-based design framework by applying the Alternate Path Method (APM). In this approach, the structural system is analytically assessed by removing selected columns to represent accidental or abnormal loading conditions, in accordance with recommended provisions such as GSA (2016) and DoD (2013) guidelines. Both nonlinear static (pushdown) and nonlinear dynamic analyses are performed to evaluate the ability of the frame to redistribute loads, undergo controlled deformation, and develop alternative load paths after sudden member loss.

The structural response is assessed using key performance indicators including displacement demand, ductility requirements, plastic hinge development, axial force redistribution, and residual load-carrying capacity. Through these evaluations, the study aims to provide a clearer understanding of the collapse resistance mechanisms in SMRF systems and to propose practical design.