A. To specify buckling analysis

To instruct the program to perform a buckling analysis on the structure, use the following procedure.

This analysis type is used to calculate the buckling factor for a load case. This is the load case multiplier at which global buckling of the structure would occur for that load case.

Either:

select the Analysis page

or
on the Analysis and Design ribbon tab, select the Analysis Commands tool in the Analysis Data group

The Analysis/Print Commands dialog opens.
Select the Perform Buckling Analysis tab.
Select the method for the buckling analysis:

Iterative method

or
Eigen method - available for STAAD.Pro Advanced only
(Optional) If the iterative method is used, type the maximum Number of Iterations to use in the analysis. It not specified (i.e., left as zero), 20 iterations are used as the default value. 15 is recommended.
Note: MAXSTEPS input is ignored when using the eigen method.
Select the Print Option you want to use.
Click Add. The perform buckling analysis command is added to the input file.