Analytical and Experimental Evaluation of Progressive Collapse Resistance of a Flat-Slab Posttensioned Parking Garage

Despite the popularity of posttensioned (PT) floors for parking garages and the likelihood of a column loss, due to blast or vehicle impact, there is a lack of research on the progressive collapse potential of this structural system subsequent to initial damage. In this paper, progressive collapse resistance of an actual posttensioned parking garage is evaluated experimentally and analytically. An interior column was removed by explosion and the structure resisted progressive collapse with a permanent maximum vertical displacement of about 61 mm (2.4 in.). Analytical models of the garage are developed using computer software and nonlinear dynamic analyses are performed. The interaction between the tendon and the slab is modeled explicitly. The analytical results show that despite the fact that the slab around the removed column had no bottom reinforcement and the tendons were placed close to the top of the slab, pushing the slab down, the compressive membrane forces developed in the slab helped increase the flexural strength of the slab sections. The gravity load redistribution is discussed and characterized. (C) 2015 American Society of Civil Engineers.