HSS bolting edge distance 1

[Althalus]

I need help finding if this variable is specified anywhere.

I am looking at an HSS connection that isn't addressed in AISC DG 24. It is an HSS-to-HSS moment connection that is bolted via cheek plates.

Most of the connection calcs are no different than a standard bolted connection. But I've found one variable that isn't addressed anywhere.

Example HSS4x4x3/8

Workable flat = 2-5/16"​

3/4" bolt; 13/16" dia hole​

For shear load in the depth of the beam (not the length of the beam) we only have 3/4" from the edge of the hole to the edge of the flat.​

Question: Is the edge distance (for section J3.1) (lc in Eq J3-6c,d) only to the edge of the workable flat? Or somewhere in the radius? Or all the way out to the full 4" depth?

Where is that specified?​

 

[dhengr]

Althalus:
That/your edge distance, for this situation, probably isn’t specified anyplace, at least not that I know of. But, let’s think a little bit about what edge distance really means. Mostly it refers to a free/raw edge of a plate or member, rolled edges and flame cut or sheared edges req’r. some special differentiation, due to how they are made. And, it pertains to a shear/ bending tension/splitting failure at the free edge when the bolt force is perpendicular to that edge (bolt bearing area near and toward the edge), it just blows that edge out. Or, there could be a tensile splitting failure, at the stress concentration area and in the min. net area of the pl. due to a tension stress field moving through that min. net area, or due to shear/reaction force parallel to the edge. Aren’t those the two primary things we are concerned about when we consider a min. edge dist? And, the edge dist. must be sufficient to prevent these types of failures. The edge dist. is still defined from the center of a std. sized hole to the pl. edge, right? So, you have more edge dist. than the .75” you calced. already. Then, you certainly don’t have a free/raw edge, you have a nicely shaped, rolled or formed edge, and the perpendicular tube wall helps protect that edge whatever/wherever it is. Certainly, that tube wall confines and absorbs/shares some of the high tensile and shear stresses which might lead to rupture of the imaginary edge, and the fab process tends not to produce stress raisers on/at the edge. The rest is engineering judgement and how I feel at the moment. I’d lay that radius, wall thk. and bolt hole out and see what it looks like.

 

[phamENG]

Althalus - I always get nervous when I see HSS to HSS 'bolted' connections. I'm not familiar with the term cheek plates - it brings to mind a pair of shear tabs on the sides of the supporting member. Might work as a moment connection if it's a beam to beam, not a beam to column.

Either way, if loaded in shear I hope you aren't using through bolts, which aren't considered bolted connections in that arrangement - they'd be pins.

 

[Althalus]

...it pertains to a shear/ bending tension/splitting failure at the free edge...

That was what I was missing. I had thought it was more of a direct shear force. But it makes so much more sense that it is the tension fiber of a bending load.

Now the answer is obvious. It simply doesn't apply to my situation.

Thanks