Why is the second shear configuration treated as single shear instead of double shear?

[princejan7]

Homework Statement

http://postimg.org/image/me4or4j7p/
http://postimg.org/image/tvdw6c8qt/


Using the views "a-a" and "b-b", can someone explain if these are single or double shear?

I''d have thought they were both double shear, but the solution to the second one treats it as single shear?

 

[PhanthomJay]

yes the first one is in double shear, but the second is single shear. In the first, the shear load from the bar is resisted by 2 shear planes in the bolt, one plane on each side of the bar. The bolt is supported at its end by the clevis attachment vang plate. Classic double shear.

In the second, you are applying equal and oppposite forces to the pin, with no end supports ...single shear(the shear plane is in between the 2 loads).