This study investigated the structural behaviour of compact cold-formed steel lipped channel beams subject to inelastic local buckling and yielding, and lateral-torsional buckling effects under simulated fire conditions and associated section and member moment capacities. Firstly, an experimental study based on tensile coupon tests was undertaken to obtain the mechanical properties of elastic modulus and yield strength and the stress-strain relationship of cold-formed steels at uniform ambient and elevated temperatures up to 700oC. Predictive equations were developed for yield strength, elastic modulus reduction factors while a modification was proposed for the stress-strain model at elevated temperatures.
Thereafter, suitable finite element models were developed to simulate the behaviour of compact cold-formed steel lipped channel beams subject to local buckling and yielding, and lateral-torsional buckling effects. An extensive finite element based parametric studies of section and member moment capacities of lipped channel beams at ambient and uniform elevated temperatures were then performed. Based on the FEA results suitable recommendations were made in relation to the accuracy and suitability of current design rules for section moment capacity at ambient and fire conditions. New design rules were proposed to accurately predict the lateral-torsional buckling capacities at ambient temperature. Furthermore, the results showed that lateral-torsional buckling capacities are dependent on the ratio of yield strength and elasticity modulus reduction factors and the level of non-linearity in the stress-strain curves at elevated temperatures. A new design rule that uses a non-linearity factor, which is defined as the ratio of the limit of proportionality to the yield stress at a given temperature, was developed for cold-formed steel beams subject to lateral-torsional buckling at elevated temperatures.