Stress concentration factor on lifting lug

[Spoonful]

Dear All,

When designing lifting lug, (made from a square plate with a hole cut in the middle). Do you apply stress concentration factor at the inside edge of the pin hole? Or do you only compare average normal stress across the remaining cross sectional area, F/A to 0.6 *Fy (AISC ASD part 5 D1)?

If yes, how to calculate the SCF? Roark's table 17.1 case 7a? see it as a rectangular shape subject to axial tension with hole in the middle? But in fact, it is only half the case, as only one edge with be axial tension, which is welded to the structure. and load in the other direction, is from the bearing stress in the pin hole. But eventually, at pin hole transverse plane, it is still axial tensile stress. So case 7a can be applied here?

If no, any explanation?

I am only talking about the normal stress here and the pin hole transverses plane, not any other aspects.

Thanks in advance

 

[JStephen]

I use the pin/hole analysis from ASME BTH. This is based on an average-bearing-stress approach, and also includes checks for tear-out, etc.

 

[Spoonful]

Hi JStephen,
I am aware of ASME BTH, but I don't recall it use SCF on stress at edge of pin hole.

Question is should SCF be used here?

 

[JStephen]

It doesn't apply a SCF, just uses average stress over bearing area.

 

[Spoonful]

Any idea, why not?

 

[JStephen]

Bearing design for bolt holes is based on similar ideas, you can get some local yielding at the bolt-hole interface without failure of the connection.