Part 'B' - Bolted Joint Design

Given Data:

N = No. of bolts = 4

W = Weight of bracket and pulley = 175 lb.

P = Load on each side of rope on pulley = 6000 lb.

n = 2

 

Analysis:

The bolts' selection has to be based upon a stress analysis of the shear stresses and tensile stresses (due to bending) acting on the bolts

  1. From table (8-4), select an SAE grade of bolts to be used and note the tensile and yield strengths of the bolts and the material. Also, you may select a bolt size from the range given for the bolt grade you have selected and obtain the corresponding shear and tensile area values from table (8-2)
  2. Calculate the shear stress acting on each bolt

    3. where:

    V = Total shear load acting upon the bolts due to the loads and the weight

    N = No. of bolts

    As = Area of shear of the bolts - table (8-2)

    Sy = Minimum yield strength of the bolt - table (8-4)

     

  3. Calculate the tensile stress due to bending in the upper 2 bolts, as there are no tensile stresses in the lower bolts

Tensile force on each upper bolt due to bending is given by:

where:

S Ma is the summation of bending moments about point 'O' on the upper bolts

y is the distance between point 'O' and the upper bolts

Therefore, the tensile stress on each bolt is:

where:

At is the tensile area of the bolt - table (8-2)

St is the minimum tensile strength of the bolt - table (8-4)