Behaviour of a T-stub assembly in steel beam-to-column connections at elevated temperatures

This paper develops an analytical model, based on simple beam theory and which incorporates the thermal degradation of the component materials, to investigate the elevated temperature behaviour of a T-stub assembly in a steel beam-to-column connection. Unlike similar analytical models in which the T-stub is attached to an infinitely stiff support mechanism, the physical interaction of the end plate and column flange is considered in the proposal developed in the current paper. The theoretical approach for evaluating the thermo-elastic and plastic behaviour of a flexible bolted T-stub assembly is based on the observation that, depending on the ratio of flexural stiffness of the end plate which acts in series with the column flange to the axial stiffness of the bolts, possible failure modes exist for which the ultimate and yield loads and the associated deflections can be derived from simple beam theory. This analytical model developed in the paper is validated against test results reported elsewhere in the literature, and it is shown that the model proposed in this paper satisfactorily predicts the behaviour of a T-stub assembly exposed to fire. Within the methodology of the component method for joint design, the results indicate that understanding and quantifying the response of a T-stub assembly at elevated temperatures are crucial for the accurate modelling of a steel beam-to-column connection if a rational fire engineering approach is to be implemented in design.