Bolt in Tension on Face of HSS 1

[RFreund]

Is there a suggested way or maybe a reference for finding the allowable tension force that may be applied to the face of a rectangular HSS via a bolt?

The situation is a beam to column moment connection between the two HSS members. The beam has an end plate which has welded threaded studs and the connection is made with a T-C couple between threaded studs. The nuts are accessed via the top of the column. The loads are pretty small.

Thanks!

EIT
www.HowToEngineer.com

 

[TehMightyEngineer]

I don't believe chapter K of the AISC specification addresses this and I'm not aware of anything else that does. You could probably idealize the bolts as a connecting plate but not sure how you could take into account the net section loss for the bolts. I'd try to revise the connection to match the typical connections rather than use bolts like you have.

Maine EIT, Civil/Structural.

 

[EngineeringEric]

Construction wise, is that even possible? And why do it?
- I would stick with chapter K connections and those outlined in the AISC Design guide for HSS. In my experience HSS is sometimes more sensitive than other sections and has less capacity in reserve when these types of assumptions are made.

 

[WillisV]

AISC 2010 J3.12 - rational analysis required - per Commentary suggested to use a yield line analysis.

 

[TehMightyEngineer]

Would that be allowed if he was still under the 2009 IBC?

Maine EIT, Civil/Structural.

 

[WillisV]

Rational analysis is always allowed - encouraged even

 

[TehMightyEngineer]

Okay, wasn't sure if it would be considered un-conservative as it's not part of chapter K but that makes sense.

Maine EIT, Civil/Structural.

 

[RFreund]

Jeez guys where's the engineering spirit? What do you think Mr. Tomasetti said when they approached him and asked "Thornton, we want you to engineer the worlds tallest building." Well he certainly didn't say, "Guys I think we should cut a few hundred feet off of it and keep it within in the range of typical structures."

I jest, but I would keep it typical if I could and we may need to in the end but lets see what we can come up with first.

Thanks Willis, this was the approach I had started.

Thanks again!


EIT

http://www.HowToEngineer.com

 

[RFreund]

Well I should have looked there first but AISC Design Guide 24 has examples for threaded studs and bolts.... not sure how I missed that....

EIT

http://www.HowToEngineer.com

 

[TehMightyEngineer]

Good to know.

Maine EIT, Civil/Structural.

 

[SAIL3]

If it is a moment conn then I would assume it was considered fixed. I would expect quite abit of rotation or local deflection on the face of the col. Using yield-line analysis in this case may inherently contribute to this especially being so close to the open end of the col. The following are a some concepts.
1. Use a large flat plate washer on inside face of col that would span from corner radius to corner radius.
In fact I would supply two in case one is dropped inside. If I can get the load from the face into the
sidewall on a HSS member, I am usually home free.
2. Extend the bolts all the way thru the other face of col.
3. Try Hollo-Bolts as they may have some given values for tension.

The major red flag for me in this conn is the proximity to the open end of the col...instinct tells me to put a cap pl on the col.

 

[racookpe1978]

The sketch shows a net upwards moment?

 

[RFreund]

Sail - good points, thank you.

Racookpe - moment would actually be either direction



EIT

http://www.HowToEngineer.com

 

[WillisV]

For future reference AISC DG24 has an example of this type of connection in Example 3.2 - illustrates bolt pullout / yield line check of HSS wall etc. It does assume that it is not at the top of a column though.

 

[racookpe1978]

OK. See the figure linked above.

So, you have two HSS sections, with a flat plate welded on the end of the horizontal member.
Fine.
That flat plate is intended to be bolted to the side of a vertical HSS member with two (or four????) round threaded things. The vertical HSS member does not have a cover plate. We will assume that this is either indoors, stainless, or Paint will cover everything magically later. 8<)

Now, how do propose attaching the threaded rods to the vertical plate on the end of the horizontal HSS member? You do not show through holes and an internal bolt head, so I assume you will call for a fillet weld on the threaded rod to the vertical plate, right? If so, how much space are you making room for that fillet in the holes on the vertical plate? Will these "oversize" holes in the vertical plate affect your assumptions for shear resistance?

Once the threaded rods are welded to the vertical plate, they cannot be moved of course. How do you propose lifting or rigging the horizontal member into lace and sliding it into the holes in the vertical HSS member? Will you be able to move the horizontal member in the right direction to get clearance?

Once assembled, how are you going to put on the nuts and washers on the ends of the threaded rod? How can you torque those nuts inside the vertical HSS member with what tooling to what torque?

 

[RFreund]

@Rac -

That is a good question regarding being able to "bend back" the columns enough to get clearance for the threaded headed studs to fit into the holes. We will have to see how feasible this is.
As for nuts and washers - the columns will need to be large enough to fit the wrench in from the top of the column.

Again loads are small as it is an open single story structure. Most size will most likely be controlled by deflection as opposed to strength.

thanks again for the comments.

EIT

http://www.HowToEngineer.com

 

[trainguy]

RFreund,

I would explore the following:

Add a welded cap plate to the column that extends over the beam as well and gets bolted to it.

The advantage is that this gives a real load path for your moment into the column webs.

At the bottom, I'd use a seat angle shop welded to the beam and bolted to the column.

Maybe not 100% continuous but almost.

tg

 

[charliealphabravo]

I think that very little moment can be transferred across the connection shown and that the resistance will not be realized until the rotation is excessive. A more efficient connection would involve a knife plate through the HSS column and a cap plate for the column.