Warning W22 (lateral torsional buckling)

  • Module code ESA1513
  • Software
    • SCIA Engineer
  • FAQ topic

This FAQ explains what you can do when receiving the warning W22 "The cross-section concerns a section with K < 0.1 or K > 2.5. K has been set to the respective limit. Please review the mechanical properties!". This refers to cantilever factors.

First of all, on following helppage you can find more information on errors, warnings and notes for steel design.

Warning W22 indicates that the K-factor should be in a specific range for applying the ECCS 119/Galea method for determining the C-factors (in the Lateral Torsional Buckling (LTB) check). So here you fall outside of the "scope" for this approach.

More information on this is given on following helppage, under the cantilever section.

First of all, you can check the lateral torsional buckling supports in the System lengths and buckling settings dialog. There you can check if the lateral torsional buckling supports match your situation in reality (e.g. cantilever or not,...).

Another possibility is to change the method for the calculation of the C-values for LTB (C1, C2 and C3) in the steel settings:

We wouldn't recommend the ENV-method since this is an old, conservative method.
With Lopez you are on the safe side, you can read about the differences in our steel manual (from page 63 on). Lopez can be applied as long as you don't have an unsymmetrical cross-section or an eccentric load, but since only C1 is determined, it doesn't have a specific logic for cantilevers.

Another option is to change the cross-section properties in that way that you land again in the scope of this approach.

It could also be an option to calculate lateral torsional buckling with second order. For this a specific module (sensd.07) is needed in your license (and is more applied in Germany), see also https://help.scia.net/22.0/en/#steel/code_checks_inc_fire_resistance/tb_steel_uls/annexes/annex_e_lateral_torsional.htm

Or a final option is to execute a shell analysis (so modelling the element with 2D-elements).

Or you can simply ignore this W22 warning if you don't expect LTB to be the limiting check.