Design imperfections for steel beam lateral torsional buckling

To perform geometrically and materially nonlinear analyses including imperfec-tions for steel beam lateral torsional buckling, the size and shape of the geometric imperfec-tion can be obtained from EN 1993-1-1. The shape is prescribed as an initial bow along the weak axis of the section, excluding torsion of the cross-section. The shape of the imperfection can alternatively be taken equal to the lateral torsional buckling mode, including torsion. Sev-eral tables and formulas exist to determine the size of the imperfection. Different imperfection approaches were applied in finite element simulations to evaluate the lateral torsional nonlin-ear buckling resistances and to compare them to the results obtained with design rules