Calculation buckling ratio for lattice tower members

When the national code EC-EN is selected, the buckling configurations given in the following paragraphs can be selected. These systems are only used in case of L-sections (Formcode 4).

The following properties are defined:

i_yy	radius of gyration around yy axis
i_zz	radius of gyration around zz axis
i_vv	radius of gyration around vv axis

When the option 'Bracing members are sufficiently supported' is activated in the buckling data, the effective slenderness is reduced as follows:

for vv-axis :
for yy-axis :
for zz-axis :

Reference is made to EN 1993-1-1 Annex BB Article BB.1.2 and formula (BB.1).