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.
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Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM