Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Design
	Subarea:	American Steel Design
	Original Author:	Bentley Technical Support Group

How is the shear stress calculated in STAAD.Pro for AISC design code? 

The shear stress calculated by STAAD is the maximum shear stress by default which is based on the standard formula VQ/Ib, where

V = Shear force

Q = Moment of area of the part of the cross section that
is above ( or below ) the plane where shear stress is being calculated, about
the neutral axis

I = Moment of Inertia

b= Width of the section at the plane where the stress is
being calculated

So the term Ib/Q is reported as the shear area that corresponds to this shear stress calculation.

If required one can get STAAD to calculate the average shear stress instead of the maximum. There is a SHE design parameter that can be used to influence how STAAD calculates the shear stress. When the parameter is set to 0 ( default ), stress is calculated as mentioned above. However when this parameter is set to 1, average shear stress will be calculated based on the formula V/Ay (or Az ) where Ay or Az are the shear area for the cross section.