Hello everyone,
I have a question regarding the Steel Design add-on and the calculation of Mcr.
I am working with a 2D rigid frame and using the default Eigenvalue Method for the evaluation of Mcr. What I am trying to understand is how the amplifier αcr is actually determined.
The value of αcr used for Mcr does not match any of the critical load factors from my regular stability analysis of the full frame.
To investigate this further, I also created a separate model containing only the specific member and tried to reproduce the same moment distribution, but I still could not obtain the same αcr value.
I understand that the value is related to the relevant LTB mode, but I would like to understand more precisely:
- How is αcr determined internally in the Steel Design add-on?
- Is it based on a separate member-level eigenvalue analysis rather than the global frame stability analysis?
- Which assumptions are included, for example regarding effective boundary conditions, moment distribution, load application, or warping/torsional restraints?
Any clarification would be greatly appreciated.
Kind regards,
Jannick