I want to check the Von Mises stress for the steel members in my model. Can I do that ?

In STAAD.Pro Von Mises stress is not reported for beams elements. However there are a couple of steel design codes in STAAD.Pro that calculates the Von Mises stress and can check it against the allowable values specified in the code. These are the Japanese code (AIJ ) and Norwegian code ( NS 3472 ). Please ensure that for the Japanese code you enter the MISES parameter and set it to 1 for the von Mises stress to be reported in the analysis output file ( reported as fm ). Similarly for the NS3472 code, please ensure that you set the BEAM parameter to 1 to get the Von Mises stress reported in the analysis output file ( reported as Svm ). These are explained in the example below

PARAMETER 1

CODE JAPANESE 2005

MISES 1 MEMB …

CHECK CODE MEMB …

PARAMETER 1

CODE NS3472

BEAM 1 MEMB …

CHECK CODE MEMB …

To view the analysis output file, go to File > View > STAAD Analysis Output.

You would need to have licenses for these codes to be able to get these output. If license is not available, you need to calculate these stresses manually based on the axial, bending and the shear stress reported by STAAD.Pro but that would certainly involve some amount to effort.

It may also be worth noting that Von Mises stress is reported by STAAD.Pro for plates and can be checked from the postprocessing mode Plate Center Stress table  > Principal and Von Mis tab