Note: Stresses induced by the load do not exceed the elastic limits of the corresponding material.
First the vertical shear 'V' at n-n is determined from the free body diagram shown below
The moment of area Q at point A, for a horizontal cut is given as
Thickness 't' is defined by the width of the 'cut' which in this case is 100 mm. Hence, the average shear stress at point A is
Notice this is the vertical component of shear stress at point A.
The moment of area Q at point B, for a horizontal cut is given as
Point B is at the intersection of the web and the flange. The width of the cut is 20 mm, making the shear stress
The shear stress at a point is mostly dependent on the thickness of the member at that point. Usually, in thinner members more shear stress will be present as demonstrated by this example.
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