Failure of Lightly Reinforced Concrete Floor Slabs with Planar Edge Restraints under Fire

Abstract

This paper presents an analytical model for the failure of lightly reinforced concrete slabs under elevated temperature, considering simply supported boundary conditions with planar edge restraints. This model is typically applicable to the failure assessment of composite floor slabs under fire, where the steel deck is assumed to lose strength relatively quickly, leaving a lightly reinforced concrete slab, as supported by experimental evidence. The proposed model accounts for membrane action, which arises at large slab deformations, and important it presents a rational failure criterion based on the rupture of the steel reinforcement. In this respect, this is the first analytical slab model to consider the influence of bond between steel and concrete on reinforcement rupture, while also dealing with elevated temperatures, including the potentially negative effects of thermal curvature. Based on principles of mechanics, detailed analytical forms of the model are first presented and verified for each of the ambient and elevated temperatures cases. In each case, a simplified form of the analytical model, which is more suitable for practical design-oriented application, is also proposed and verified. The successful verification of the proposed analytical models, demonstrated against the results of appropriate nonlinear finite-element analysis, paves the way for their application in the design of composite floor slabs with planar edge restraints under fire.