Numerical studies of a steel beam in a frame sub-assembly at elevated temperatures

The analysis of structural members in a compartment in a steel framed building subjected to fire attack is often difficult owing to the combined complexity of the material degradation and of the actions induced by thermal strains. Although such analyses can be carried out using advanced finite element packages such as ABAQUS and ANSYS, they do not permit an ‘overall feeling’ of the underlying structural mechanics to be fully articulated or understood. It is important that the response of structures under fire conditions, and the parameters that influence this response, are fully understood so that safe and economical performancebased fire designs can be achieved, and that codified treatments can be prescribed. This paper presents numerical studies of a steel beam subjected to fire attack in a steel framed compartment. The analysis is based on an analytical procedure that allows for a solution for the actions and deformations to be stated in closed form prior to the attainment of first yield of the steel at elevated temperature. It is found that the response of members under fire attack is governed by the slenderness ratio of the member subjected to elevated temperature the restraint afforded by the adjacent, cooler elements in the building frame and the applied thermal regimes.