Failure criteria for composite slabs subject to extreme loading conditions

This paper is concerned with the ultimate behaviour of composite steel/concrete floor slabs under extreme loading situations, particularly those that occur during severe building fires. The study focuses on the failure state associated with rupture of the reinforcement in composite slab members which become lightly reinforced in a fire situation due to the early loss of the steel deck. An account of a series of large scale ambient tests, undertaken on full slab members, is presented in the paper. The experimental arrangements are described together with the details of the specimens. Complementary analytical studies, carried out to assess the salient factors influencing the failure of composite slab members are also summarised. The assessments utilise detailed numerical models which adopt novel finite element formulations including geometric and material nonlinearities, as well as simplified analytical models for the prediction of failure deformations and associated load levels. The results of this investigation offer detailed insights into the key factors that govern the ultimate behaviour of composite floor systems under extreme loading conditions, and provide simplified tools which are suitable for implementation in performance based design procedures.