Numerical modelling of lateral-torsional buckling of steel I-beams under fire conditions - Comparison with Eurocode 3

A geometrically and materially non-linear finite element program, i.e., a general model, has been used to determine the lateral-torsional resistance of steel I-beams under fire conditions, according to the same material properties of Eurocode 3, Part 1-2. Two yield strengths, one cross section, one type of load and four different time exposures to the ISO 834 standard fire have been considered. The numerical results have been compared to the results of the simple model presented in Eurocode 3, Part 1-2. When compared with the general model, this simple model leads to a safety level that depends on the slenderness of the beam, being unsafe for intermediate non-dimensional slenderness. A new proposal has been made for a simple model that ensures a conservative result when compared to the general model.