Impact of the fabrication process on the lateral-torsional buckling of welded I-section beams

The buckling behaviour of a steel member is greatly dependent on the residual stress distribution, which is affected by the fabrication process. Indeed, residual stresses in welded steel members are significantly influenced by possible flame-cuts at the flange tips commonly used in practice. However, the Eurocode 3 rules do not account for the beneficial effects of the flame-cuts. Experimental data on commonly used slender members are limited, and therefore to gain further insight an experimental test campaign involving eight slender welded members is carried out. The influence of the flange dimensions and fabrication process was investigated. A new residual stress model is proposed for welded I-sections made of flame-cut flanges integrating results from the literature. Moreover, the actual buckling behaviour of welded members made of flame-cut flanges and/or with a cross section that is not uniform and doubly symmetric is studied. A literature overview of past experimental works highlights the lack of results on common mono-symmetric and/or tapered members, especially for welded members made of flame-cut flanges. An experimental study was thus conducted including lateral-torsional buckling tests on four beams: two uniforms and two tapered. Both types of beams comprised a doubly symmetric and a mono-symmetric I-section. The benefits resulting from tapering and/or increasing the compression flange thickness of an I-section beam are highlighted. The experimental results validate the use of a finite element model for studying the impact of the flange fabrication process on the lateral-torsional buckling resistance. Flame-cuts present at both flange ends increase the ultimate resistance.

Automated summary

The buckling behaviour of steel members is influenced by residual stress distribution, which is affected by the fabrication process. This study investigates the impact of flame-cuts on residual stresses and proposes a new model for welded I-sections with flame-cut flanges. Experimental results validate the finite element model for evaluating the effect of flange fabrication process on lateral-torsional buckling resistance.