problem 1-5, James M. Gere's mechanics of materials text book

in the given example : enter image description here

for a, b and c he used the full 12k value of P to get the bearing and shear values. my logic was to analyse the forces when getting the shear on the pin G.

my instructure said we were using the max values of P, but that wasn't a satisfactory answer for me.

also : in a, the value for the bearing area is chosen to be 2dt where d is the diamter as shown. why isnt the bearing area as shown here? (hopefully that's a clear enough aiding diagram )

enter image description here

  • $\begingroup$ "analyse the forces when getting the shear" You should elaborate on what you mean by that. $\endgroup$
    – agentp
    Commented Nov 27, 2017 at 16:47
  • $\begingroup$ I mean : shouldn’t a shear stress value be obtained from the parallel competent of the force only , not its full value . $\endgroup$
    – sarah
    Commented Nov 27, 2017 at 18:39
  • $\begingroup$ parallel to what? The base? Why? What if the strut was vertical, would you expect zero shear in the pin? $\endgroup$
    – agentp
    Commented Nov 27, 2017 at 18:51
  • $\begingroup$ In b) the shear stress in the pin G , in the answer it used the force 12k as is, my reasoning is that it should be analyzed parallel to the cross section of the pin $\endgroup$
    – sarah
    Commented Nov 27, 2017 at 19:04

1 Answer 1


Force is normal to plane in which cross section area is d*t on both sides thus 2dt. It is full force because steel strut caries only axial force and full force is transmitted to the pin and force is normal to this cross section plane. This is similar to calculation of stress in cylindrical vessel where the area used to calculate stress is the cross section of the vessel.


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