STAAD.Pro Help

P. To display nodal instabilities

To graphically examine nodes and degrees of freedom on the structure where instability conditions have been reported in the output, use the following procedure.

This feature is only available when instabilities have been detected during the analysis.
Select the Layouts > Instability tool in the View Results group on the Results ribbon tab. The locations of instabilities are highlighted on the structure in large blue circles. The Unstable Joint table provides information on the joint number and the degree of freedom associated with an instability at that joint. An unstable condition is marked with a "1".
You can apply restraints at these joints in unstable directions in an attempt to stabilize the joint.