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rickylee

Mechanical
Aug 16, 2002
38
I am having a difference in interpretation with a consultant. Please let me know what you think. This is my side:

AISC Manual of steel construction, 9th Edition.

Section D3: 0.45Fy applies in determining the hole diameter and plate thickness related to bearing load at the pin hole & (J8) 0.90 Fy applies in determining the pin diameter.

Rick
 
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I'm not quite sure of the question, but can it be that the 0.4Fy is based on the yielding of the part supporting the pin and the 0.9Fy is based on the pin shearing.

Dik
 
I think I disagree with you rickylee. It depends on the connection requirments, but the plate must be checked for both yielding with section D3 and by bearing with section J8. Typically I will size the pin for shear and bending, then size the plate for yielding and bearing. If the plate thickness is controlled significantly by the bearing then I may increase the diameter of the pin to compensate. A side note is that with the same yield strength materials, if the pin or plate satisfies the bearing requirement then obviously the other part will also.
 
Aggman:

Are you interpreting D3 to apply to the design of the pin connected member with a hole, but not actually to the bearing stress of the hole......and J8 applies to the design of the pin and hole?

This is the same opinion as the consultant.

If that's true D3 really throws me off because it says:
"The allowable stress on the net area of the pin hole for a connected member is 0.45Fy". It speaks of the HOLE!?

Rick
 
"Are you interpreting D3 to apply to the design of the pin connected member with a hole, but not actually to the bearing stress of the hole......and J8 applies to the design of the pin and hole?"

Yes, I interprete D3 to apply to the design of the pin connected member with the hole. You have to consider it as two seperate checks. One check is to insure that the connected plate has enough meat around the hole to keep from tearing out. Another check is to insure that the plate and pin are large enough so that you will not get deformation around the hole. The difference in allowable stresses has to do with the mode of failure. For bearing you can use 0.9*Fy. This is because if the plate has some bearing deformation the connection will not necessarly fail. If the plate fractures around the hole then the connection will fail. This could be a shear tearout parrallel the the resultant force or a fracture tearout normal to the force.
 
The research that led to Article D3 was published as ASCE Transaction Paper 2023, in 1939, by Bruce G. Johnston. The research paper devotes much concern to "dishing" (or buckling) of the connected plates. Dishing can occur if the plates are too thin. The AISC provisions of D3.2 are written to prevent dishing. (Note: the end of paragraph 2 should read "more than 0.8 times the diameter of the pin hole.")

If you follow the provisions of D3.2, the bearing stress limit of 0.9Fy never governs the thickness of the plate. In fact, algebraic manipulation of D3.2 gives an "apparent" bearing limit of 0.72Fy.
 
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