PROGRESSIVE COLLAPSE OF STEEL-FRAMED BUILDINGS: INFLUENCE OF MODELLING APPROACH

Abstract

This paper compares the influence of several modelling approaches for progressive collapse assessment of steel-framed buildings, considering sudden column loss as a design scenario. A typical steel moment frame structure is modelled at various levels of structural idealization, including assembled beam models, grillage models and frame models with the reinforced concrete slab. Both peripheral and corner column loss scenarios are investigated, where the maximum dynamic response of the above floors is regarded as a key factor defining the structural robustness. Both nonlinear dynamic finite element analysis and a novel simplified dynamic assessment method are employed, where it is confirmed that the simplified approach has good accuracy considering various structural idealizations. The influence of the level of structural idealisation is investigated, where it is shown that grillage models using a simplified assembly procedure predict the response of a frame idealisation under sudden column loss quite well. On the other hand, the incorporation of the reinforced concrete floor slab can significantly affect the structural response to sudden column loss beyond the predictions of grillage models due to 2D slab effects. It is recommended that progressive collapse assessment of multi-storey buildings under sudden column loss is performed using the simplified dynamic assessment procedure, and that grillage models can be used as a conservative representation in the absence of detailed slab models.