Three-dimensional modelling of steel/concrete composite connection behaviour in fire

A three-dimensional mathematical model `FEAST' was developed to simulate the response of steel structures in the event of a fire. It has been further developed to model the behaviour of steel/concrete composite connection at elevated temperatures. This paper summarizes the proposed theoretical background of the model which was dedicated for the analysis of the semi-rigid composite connection. The composite connection comprises not only the main beam and the column, but also a reinforced concrete slab supported by cold-formed profiled steel sheeting which in turn is connected to the top flange of the main beam by shear studs. The analytical methods is based on a finite element procedure with special consideration of bolts, shear studs and concrete behaviour. The advantage of using `FEAST' described here is that, by taking into account a realistic non-linear differential temperature profile, it allows automatic interaction between the bolts, shear studs and the reinforcement which are the main components contributed to the moment capacity of the composite connection. The temperature-rotation characteristic of the connections is produced at various applied bending moments. The mathematical model was compared with a series of fire tests carried out recently at the Building Research Establishment, UK. The comparison was found encouraging. Further comparison between the behaviour of composite and non-composite connections is also presented in this paper. As expected, there has been substantial enhancement in the limiting temperature by the composite connection. The tool developed here would therefore be very useful for further study of the behaviour of steel frame with composite action in the course of a fire.