Design Oriented Approach for Progressive Collapse Assessment of Steel Framed Buildings

This paper introduces a relatively simple yet accurate methodology to evaluate the efficacy of steel framed buildings against progressive collapse initiated by sudden local column failure. The proposed procedure can be implemented at various levels of structural idealisation, considering either the full damaged structure or critical substructures. In either case, the procedure accounts for the dynamic effects of column failure, where three main assessment stages are proposed. The first stage involves determination of the nonlinear static response of the structure/substructure under gravity loading using either simplified or detailed modelling techniques. The second stage employs a newly developed simplified dynamic approach, where the maximum dynamic response is estimated from the nonlinear static response using an energy equivalence criterion. The final stage assesses the vulnerability to progressive collapse by comparing the ductility demand in the connections, corresponding to the maximum dynamic response, to the ductility supply, considering the deformation capacity of individual connection components. The applicability of the proposed approach is demonstrated through a case study, which considers sudden removal of a peripheral column in a typical steel framed composite building. This study shows that such structures can be prone to progressive collapse. Several remedial measures are investigated, including the benefits of additional slab reinforcement over the connections.