Failure of unrestrained lightly reinforced concrete slabs under fire, Part II: Verification and application

The simplified analytical models developed in the companion paper for the failure assessment of simply supported composite floor slabs without planar restraints are investigated further in this paper. In addition to taking account of membrane action and the material response at elevated temperature, these models allow for the bond developed between the reinforcement and the surrounding concrete. This is an essential requirement for defining a rational performance-based failure criterion for composite floor slabs at elevated temperatures, since the bond along with the characteristics of the reinforcement response govern failure by rupture of the reinforcement across full depth cracks. The kinematic assumptions inherent in the formulation of the complete and simplified variants of the models are first verified against detailed finite element analysis, and comparisons are made against a previously proposed model to identify common features and important benefits. Subsequently, the models are utilised in several examples which demonstrate their applicability, and the treatment of important factors related to boundary conditions and geometric configuration is discussed, highlighting in the process any restrictions on the application of the proposed models.