Lessons from a Full Scale Fire Test

This paper draws together some important lessons from a compartment fire test conducted by BRE in the full-scale eight storey steel building at Cardington. The experiment is briefly described, and the main structural observations are highlighted. A numerical structural model of the fire compartment, using the nonlinear analysis program ADAPTIC, is then discussed. The numerical analysis employs a grillage to model the composite floor slab, and uses a onedimensional element to model the supporting steel beams and columns. Detailed consideration of the numerical model illustrates the importance of accounting for thermal expansion effects, and leads to the identification of a load carrying mechanism at full temperature in which both the floor slab and the composite beam play an important role. A sensitivity study is then carried out in which characteristic sizes of various components and strengths of the different steel and concrete materials are varied, and the influence of such variations on the floor system response is investigated. This not only highlights the relative importance of various components in resisting the floor loading, but also sheds considerable light on the extent of plasticity developed within the various materials over the structure. Finally, several implications of the present experimental and numerical findings towards an improved design procedure, which accounts for the interaction between the floor slab and the composite beam at elevated temperature, are discussed. Reader in Computational Structural Mechanics, Dept. of Civil & Env. Eng'g, Imperial College, London. Director of Centre for Structural Engineering, Building Research Establishment, Garston, Watford. 2