Numerical modelling of the structural fire behaviour of composite buildings

This paper describes numerical models constructed to simulate the response of composite steel/concrete building floors under fire conditions. In parti cular, this study deals with two of the fire tests recently undertaken on a full-scale multi-storey building at Cardington, UK. The analysis is carrie d out using a structural analysis program which accounts for both geometric and material nonlinearities, and which includes temperature-dependent cons titutive models for steel and concrete materials. The approaches used to re present the various structural details are discussed, and the procedure emp loyed for incorporating the experimentally measured temperature profiles an d histories is outlined. For the two tests considered in this investigation , the numerical results are in general agreement with the experimental data , particularly in terms of the magnitude of vertical deformations induced i n the floors at elevated temperatures. Close examination of the numerical a nd experimental findings provides an insight into the complex interactions that occur in the structure at elevated temperatures. Most significantly, t he influence of the restraint to thermal expansion of the heated floor area , which is provided by the surrounding parts of the structure, is shown to be of paramount importance. The increasing confidence that can be placed in numerical models as well as the improved understanding of the structural f ire response may be used in developing more realistic and cost-effective de sign methods which are based on the actual structural response rather than that of isolated members. (C) 2000 Elsevier Science Ltd. All rights reserve d.