Biege- und Biegedrillknicknachweise nach Eurocode 3 anhand von Berechnungen nach Theorie 2. Ordnung

Flexural and lateral torsional buckling checks of steel frames according to Eurocode 3 using 2nd order analysis.

Sections of rolled profiles or similar welded profiles have due to their strong axis an in-plane-resistance that should be exploited by preventing out-of-plane stability failure about the weak axis. DIN EN 1993-1-1 [2] gives rules for out-of-plane stability checks (lateral flexural or lateral torsional buckling) that can be performed according to one of the following methods: the method using 2nd order analysis for which equivalent geometric imperfection are defined and that is considered as a generic method, and the method with member checks using flexural or lateral torsional buckling curves, that have been determined for frequent cases (object-oriented method).
This contribution treats out-of-plane stability checks using 2nd order analysis with equivalent geometric imperfections, that have been defined in DIN EN 1993-1-1 [2] as elastic buckling modes. To determine these functions computer-assistance is required, that gives not only the modal displacements, but also the modal bending moments for the relevant flanges of the profiles.
The use of out-of-plane modal bending moments makes the assessments clear and simple. They lead to the assessment of the in-plane utilisation rates, which are enhanced by a factor f due to the out-of-plane bending moments. Worked examples from practical applications illustrate the surprising simplicity of use.