Behaviour and resistance of cold-formed steel beams with lipped channel sections under fire conditions

Abstract

Purpose

Steel beams composed of cold-formed sections are common in buildings because of their lightness and ability to support large spans. However, the instability phenomena associated to these members are not completely understood in fire situation. Thus, the purpose of this study is to analyse the behaviour of beams composed of cold-formed lipped channel sections at elevated temperatures.

Design/methodology/approach

A numerical analysis is made, applying the finite element program SAFIR, on the behaviour of simply supported cold formed steel beams at elevated temperatures. A parametric study, considering several cross-sections with different slenderness’s values, steel grades and bending diagrams, is presented. The obtained numerical results are compared with the design bending resistances determined from Eurocode 3 Part 1-2 and its French National Annex (FN Annex).

Findings

The current design expressions revealed to be too conservative when compared with the obtained numerical results. It was possible to observe that the FN Annex is less conservative than the Annex E, the first having a better agreement with the numerical results.

Originality/value

Following the previous comparisons, new fire design formulae are tested. This new methodology, which introduces minimum changes in the existing formulae, provides safety and accuracy at the same time when compared to the numerical results, considering the occurrence of local, distortional and lateral torsional buckling phenomena in these members at elevated temperatures.

Citation

Arrais, F., Lopes, N. and Vila Real, P. (2016), "Behaviour and resistance of cold-formed steel beams with lipped channel sections under fire conditions", Journal of Structural Fire Engineering, Vol. 7 No. 4, pp. 365-387. https://doi.org/10.1108/JSFE-12-2016-025