Vulnerability of Disproportionate Collapse in Older Flat Plate Buildings Subjected to Sudden Removal of a Bearing Column

A macro model is proposed for disproportionate collapse analysis of reinforced concrete flat-plate structures. The macro model consists of connector beam elements for the slab near columns and shell elements for the slab outside critical sections. The macro model simulates the complex behavior associated with flexure, shear, torsion, punching failure, and failure propagation. The model is first validated by test results of slab-column connections subjected to different loading conditions and then applied to the collapse analysis of an older flat-plate building. By nonlinear dynamic and static analyses, the impact of dynamic loading on slab local force and deformation demands is examined. The analyses reveal that older flat plate buildings are highly venerable to disproportionate collapse when a support column is suddenly removed. Additionally, both the dynamic increase factor for vertical displacement at the lost column and that for slab rotation at the critical neighboring slab-column connection are greater than 2.