Geometrische Ersatzimperfektionen für das Biegedrillknicken von Trägern aus Walzprofilen - Grundsätzliches

Equivalent geometric imperfections for the lateral torsional buckling of rolled profile beams - Fundamentals.

The sufficient bearing capacity of beams susceptible to lateral torsional buckling can be verified using the equivalent imperfections method. The method is explained in detail and differences to exact calculation procedures are shown. Since equivalent geometric imperfections v0 have to be applied for this method, exact values v0 are determined for selected basis systems depending on the danger to the stability and the cross sectional shape. Analyses of the effect on the bearing capacity lead to the result that with v0 = L/150 realistic design results can be achieved for medium non-dimensional slenderness ratios. For large non-dimensional slenderness ratios smaller equivalent geometric imperfections are sufficient. Comparative calculations with the values according to DIN 18800-2 and DIN EN 1993-1-1 (EC 3) show that the standard values are too small, as a consequence, the bearing capacities are in certain areas clearly on the unsafe side.