Civil Engineering Association

Progressive Collapse of Multi-Storey Buildings due to Sudden Column Loss –Part II: Application

The companion paper presents the principles of a new design-oriented methodology for progressive
collapse assessment of multi-storey buildings. The proposed procedure, which can be implemented at
various levels of structural idealisation, determines ductility demand and supply in assessing the
potential for progressive collapse initiated by instantaneous loss of a vertical support member. This
paper demonstrates the applicability of the proposed approach by means of a case study, which
considers sudden removal of a ground floor column in a typical steel-framed composite building. In
line with current progressive collapse guidelines for buildings with a relatively simple and repetitive
layout, the two principal scenarios investigated include removal of a peripheral column and a corner
column. The study shows that such structures can be prone to progressive collapse, especially due to
failure of the internal secondary beam support joints to safely transfer the gravity loads to the
surrounding undamaged members if a flexible fin plate joint detail is employed. The provision of
additional reinforcement in the slab over the hogging moment regions can generally have a beneficial
effect on both the dynamic load carrying and deformation capacities. The response can be further
improved if axial restraint provided by the adjacent structure can be relied upon. The study also
highlights the inability of bare-steel beams to survive column removal despite satisfaction of the code
prescribed structural integrity provisions. This demonstrates that tying force requirements alone cannot
always guarantee structural robustness without explicit consideration of ductility demand/supply in the
support joints of the affected members, as determined by their nonlinear dynamic response.