Buckling Eigenvalues of a Shell Model

The following compression beam is fixed at one end and subjected to load according to Euler case 1.
The profile and system dimensions are illustrated below.
The beam is made of construction steel St 37. The load is applied at the center of mass.

According to Peterson, the ideal buckling load is P_Ki = 56.4 kN.

For the system detailed above, the FEM calculation delivers the following results for the
first 4 buckling eigenmodes. Influences such as shear strain and warping are taken into account.

Buckling eigenmode 1, load factor = 54.14 (torsional buckling)

Buckling eigenmode 2, load factor = 190.52 (buckling around the z axis of the section)

Buckling eigenmode 3, load factor = 345.88 (buckling around the y axis of the section)

Buckling eigenmode 4, load factor = 422.61 (buckling around the z axis of the second eigenmode)