HSS through bolt capacity

[Nate2017]

I am designing a HSS through bolt connection only subject to shear.

AISC eq. 7-15 and spec. J7 give the equation to predict the bearing strength of HSS through bolt holes. Does anyone know if the bearing capacity given by 1.8FyApb or 1.8nFydt refer to only one side of HSS wall? In another words, the total shear force can be resist by one through bolt is twice of that equation predicts because the through bolt is bearing on two side walls.

 

[msquared48]

I assume you are talking about double shear as opposed to single shear?

Mike McCann, PE, SE (WA)

 

[Nate2017]

Thanks Mike.

No I am not referring single shear vs. double shear of bolt. I am talking about the bearing capacity predicted by 1.8FyApb. Does that only refer to bearing capacity of one side of HSS wall?

 

[Lomarandil]

Yes, if both sides are loaded equally, your Apb or t should reflect both walls of the HSS.

 

[Nate2017]

Lomarandil, thank you for the clarification.

 

[SAIL3]

I do not see where both sides could be loaded equally in shear....I would expect that if one looks at the bolt as bm with two supports and cantilevered out to pick up the shear, one would wind up with a differnt reaction at the near face versus the farside face....

 

[Lomarandil]

Agreed Sail, hence my caveat.

I'm thinking about a truss-type connection though. If you had a through bolt passing through an HSS sandwiched between two gusset plates, where the load was applied evenly to the gussets, that would load the sides equally.

 

[Nate2017]

The connection I am designing is a truss type connection. The HSS tube is sandwiched between two plates where bolt goes through all of them. I think it is equally loaded thus "t" should be doubled to reflect both walls.

 

[connectegr]

A structural bolt is not intended to be used as a "through bolt" as you describe. Typically this is used as an erection aid only, with field welds to provide the connection strength.

Structural bolts As described in AISC 360 and RCSC, require a steel fill between head and nut. Not a hollow section. Your condition may result in bending stress within the length of the bolt. Not a good idea.

"Hollo bolts" or "blind bolts" are allowed in AISC. However these are proprietary and specifics are provided by the manufacturer. And these are not continuous "through bolts".

Bearing capacity of the wall thickness is one limit state that should be considered.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[Leftwow]

Recently we had that same issue at my work. We installed a zinc plated pipe that was welded to each side to increase the strength of a wall. We used a 3/4" (even though the true dimension was more) pipe that way the 3/4" bolt could just slide through to the other side, which gives you more steel area to rely on during shear force. It also acts almost as a stiffener as to prevent any bending on the "wall" of the HSS!