Ductility of composite floor slabs under idealised fire conditions

This paper is concerned with the ductility of composite floor slabs under extreme loading conditions. Although the consideration given to the assessment of ductility is of general relevance to various applications, it is of particular significance to conditions resembling those occurring during severe building fires. The main purpose of the study is to examine the failure of composite floor slabs which become lightly reinforced in a simulated fire situation owing to the early loss of the steel deck. An account of the main results from 15 large-scale tests on simply supported slab specimens is presented. A simplified expression for predicting the ductility of this type of member is proposed, after calibration and validation against the experimental results and more detailed analytical relationships. The experimental results and observations enable a direct assessment of the influence of a number of important parameters, such as the reinforcement type, properties and ratio on the ultimate response. The tests and proposed failure prediction relationships also provide a fundamental insight into the key factors that govern the ductility and failure behaviour of lightly reinforced slabs. With due consideration of the findings and verifications from other complementary experimental and analytical studies under various geometric and temperature conditions, this work suggests a fundamental basis for developing quantified and realistic failure criteria.