Question

Determine the secondary shear stress acting on the bolt 3 and its direction. The bolts are equidistant having separated by 60mm and the margin to the left and right is 25mm.Also P=5kN acts at a distance of 200mm from the channel.

(a) 6100N vertically up

(b) 4500N vertically down

(c) 6100N vertically up

(d) 4500N vertically down

I encountered this question at a technical round.

This technical question is from the Eccentric Loaded Bolted Joints unit in lesson Threaded Joints of Machine Design

Answer 1

The suitable answer is (c) 6100N vertically up

Break it down: Moment about CG=3000 x (75+30+200). On bolt 3 secondary shear force will be M x r₁/ (r₁²+r₂²) and will act in a direction perpendicular the line joining CG and bolt 3. As moment is CW about CG, o bolts its effect will be ACW.