A simple model for the lateral–torsional buckling of steel I-beams under fire conditions: numerical and experimental validation

When a beam is bent about its greatest flexural resistance axis it may twist and move laterally, before it reaches its strength limit. Although this problem of lateral-torsional buckling of steel beams at room temperature is well known, the same problem at elevated temperature is not. This paper summarises the results obtained in the scope of a research project entitled “lateral buckling of steel I-beams under fire conditions”, where a set of 120 experimental and numerical tests were performed on IPE 100 beams, submittted to temperatures varying from 20 °C to 600 °C, to validate a new proposal for the buckling resistance moment of a laterally unrestrained beam under tire conditions The numerical and experimental results for the lateral-torsional buckling of steel I-beams have been compared to those from the simple model presented in Eurocode 3, Part 1-2. This Eurocode simple model promotes safety levels that depend mainly on the non-dimensional slenderness of the beams. The analytical results provided by flue Eurocode 3, for a certain range of the slenderness, would now appear to be unsafe when compared with the numerical and experimental results. It will be shown that the new proposal is safer than the Eurocode 3 formulas.

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