Lateral-torsional buckling verified by the compression flange as an equivalent compression member – consistent verification for welded members in cold and hot conditions

Verification of the compression flange as an equivalent compression member represents a clear and easy model for practical application of lateral-torsional buckling. EN 1993-1-1, Para. 6.3.2.4 relies on this simplified model for calculation of members in structural design. For bridge-building, this verification method is adapted with conservative assumptions for the length of the plateau and allowing for buckling curve d for welded sections. A simplified hot calculation of members subjected to lateral-torsional buckling seems in general possible when adequately allowing for temperature-dependent material parameters. At the moment, however, EN 1993-1-2 does not explicitly provide for such a simplified verification. Currently, there exists no consistency as to simplified verification by means of the compression flange as an equivalent compression member and detailed lateral-torsional buckling verification based on the critical moment Mcr as well as to various application areas. Therefore, achieving a consistency in verification is one of the main aims of the project.
Especially regarding welded sections scientific findings are lacking for the residual stresses caused by welding of the sections. The residual stresses can extend up to the amount of the yield strength of steel. It is a fact that in most cases these residual stresses are more critical than is the case with rolled sections. This effect is difficult to quantify, however, due to the lack of scientific findings. Furthermore, it is doubtful if these residual stresses have any relevant influences on the buckling behavior in the case of fire. The second focus of the project is therefore on the influences of residual stresses on the buckling behavior in the case of standard temperatures and in the case of fire.

Universität Stuttgart, Institut für Konstruktion und Entwurf, Prof. Kuhlmann, Fabian Jörg
Ruhr-Universität Bochum, Lehrstuhl für Stahl-, Leicht- und Verbundbau, Prof. Knobloch, Lukas Schaper

• AiF
• DASt
• MPA
• Astron
• Goldbeck

01.04.2017