I looked at your model and did not find any problem with it. I am not sure what could be the reason for the difference but will investigate this further and revert back.
In case it helps, we did validate the STAAD.Pro results against the two benchmark problems published by AISC to check for adequacy of the second order analysis that is used in Direct Analysis
communities.bentley.com/.../20435.benchmark-problems
In case it helps, we did validate the STAAD.Pro results against the two benchmark problems published by AISC to check for adequacy of the second order analysis that is used in Direct Analysis
communities.bentley.com/.../20435.benchmark-problems
