Skirt bolts calculation - shear stress

Hi everybody,
with the check of a skirt basering bolts shear stress made by pvelite I found that the shear force is divided by two [shear stress = shear force/(2*Bolt area*Number of Bolts) ].
Is there anybody can suggest me the reason?
My idea is that there is the contribute of the friction (0.5).

Thanks.

Hello LPFBM

PV Elite is actually correct. If you remember your studies in strength of materials you will see that the shear force cannot exist at right angles (radially) to the rim of bolt. The shear stress travels around the circumference of the cross-section of the bolt. Just check this out in any strength of materials book. It is because of the shear stress distribution that you see 2*bolt area.