Effect of loss of bond on flat-slab building collapses

Between 1997 and 2010, there has been a small, yet unexpected number of flat slab car-park buildings, which collapsed under service loading. In all cases, the collapse was preceded by loss of bond between concrete and flexural reinforcement. All investigations of the causes of these collapses have since been inconclusive, particularly as regards the effect of loss of bond. Yet, loss of bond due to yielding of the flexural reinforcement in tension had already been proposed as the main cause of punching and failure criteria derived on the basis of this proposal were found to produce predictions which correlated closely with experimentally-established values of the punching failure load. The present work is intended to extend the range of application of these criteria to the case of loss of bond due to steel corrosion and test their validity against the available information on the car-park building collapses.