Thermoelastic restrained buckling of composite beams Available to Purchase

A model is developed for the thermoelastic restrained distortional buckling (RDB) of a steel joist in a composite beam in a steel-framed building that may take place during a compartment fire. The overall or member buckling mode must necessarily involve cross-sectional distortion, since the rigid concrete slab in the composite beam prevents the top flange of the steel joist from freely translating, rotating and twisting as would occur in conventional flexural-torsional buckling. The solution is based on a stiffness approach, with the buckling deformations being represented by a Fourier series and the Ritz method being invoked to determine an eigensolution for the critical temperature. High levels of axial restraint provided by cooler frame members can produce significant thermally induced pre-buckling compression, which can lead to early thermoelastic buckling. This significant axial force can lead to potential failure of the connections at the ends of the member, and premature buckling is advantageous as it can relieve the development of this large compressive action. The numerical solution is used to investigate the influence of the parameters affecting RDB of a composite beam in a fire.