Experimental Study of Dynamic Progressive Collapse in Flat-Plate Buildings Subjected to an Interior Column Removal

AbstractThe experimental results of dynamically removing an interior column in a single-story, 2-bay-by-2-bay reinforced concrete flat-plate substructure are presented. The test specimen represented pre-1971 designed flat-plate buildings. The specimen was loaded with dead weight at a load level equal to 78% of the unfactored design load and the support under the interior column suddenly removed by means of a collapsing jack. The test specimen experienced punching failures at four neighboring slab-column connections, but did not fully collapse due to postpunching capacity. Because the gravity load acting on the slab was only slightly greater than a typical service load in a flat-plate building, an older flat-plate building may be at risk for progressive punching failures under a sudden column removal scenario. The measured axial force in two adjacent columns at punching failure was 36% less than the punching load in an isolated column test due to the effects of unbalanced moment, in-plane restraint, and dynamic loading. However, the slab rotation at punching was consistent with predicted rotation capacity and previous test data. The measured lateral expansion of the specimen indicated the presence of compressive membrane forces in the slab at the time of punching failure. The experimental results validated a macro model developed for simulating the behavior of plate-plate structures.