SHEAR STRESS and CHECK CODE

Given the axial area and the shear force from the FEA analysis, the code check will typically divide the shear force by a stress shear area such that the result is the peak shear stress on the cross-section.  For some cross-sections in some design codes in STAAD the peak shear stress = VQ / IT (so IT / QA is the shear stress area form factor).

When VQ / IT is not used, then cross section based factors are used: 
shear area = 2/3 Area for rectangles.
Shear area = depth * web thickness in Y and the combined areas of the flanges in Z for I-beams.
Etc.

Many of these formulas are embedded in the design codes and the value of stress shear area that we calculate is simply for printing purposes and not necessarily the value used in the code.

The international design codes are generally written by an independent expert in that code.  The focus is on following the code and not on a standard definition of stress shear area.

In general, you would have to ask what values we use in a particular clause of the code that involves shear.