HSS Beam to WF Column End Plate Moment Connection 2

[RFreund]

The steel fabricator would like to use an end plate moment connection for connecting an HSS to a WF column. Not sure how I feel about it. I suppose I can try to follow the DG4, but only having exterior bolts "feels odd".

 

[KootK]

1) I'm okay with the exterior bolts so long as the members work.

2) Often my beef with proposed, alternate steel connections is the connection stiffness. And, that, because it's rare that stiffness is evaluated explicitly. In this respect I don't love how fare the bolts are from the section on the HSS20. I suppose there are angles welded to the HSS that alleviate this somewhat. But, then, who the heck knows how to design that. If the detailing could tolerate it, I'd pull the angles back to allow the flange bolts to be nearer the flanges.

 

[DrZoidberWoop]

This is a pretty common connection. Some things to consider:

1) Localized HSS wall strength against "flange force" from moment and axial. See AISC design guide 24 or a CIDECT guide for HSS wall strength in compression/tension.
2) Design the HSS weld to accommodate shear, axial, and moment loads. Conservatively, disregard the vertical welds for transferring flange force from HSS wall to bolt, in the calcs.
3) Identify your worst case bolt, with regard to combined shear and axial (axial load + flange force). Slip critical bolts can be avoided if a pair of STD holes are used or SSLT holes are used in the end plate (and there is no load parallel to slot).
4) Use AISC eqn 9-17 to size the end plate to handle prying action from the bolt with the maximum axial load.
5) Check the support for prying, bearing, and other standard checks. Reinforce as req'd.


Edit to add: Draw both ends of the HSS to determine if the member can be swung in. If not, spec erection gaps at each end and tell the fabricator to provide finger shims.

 

[RFreund]

Solid feedback. Thanks to both of you!

Quick question - when you say to draw both ends to determine if it can be swung in - do you mean if there is a column on both ends that requires this detail, then it likely cannot be swung in and in that case, provide shims?

Thanks again!

 

[dik]

I'm not sure why you would want to do that? Can you explain a bit?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[DrZoidberWoop]

I think the picture explains it better than I could with words. I attached the .pdf if this image is fuzzy.

 

[DrZoidberWoop]

Dik. The flange force needs to be transferred to the bolt from the HSS. The most direct load path will be from the bolt to the top & btm HSS faces. There are obviously grounds to evaluate the 4 sided weld group to handle combined loads, but the behavior from prying action leads me to believe the flange force will go predominantly to the weld joints on the top & btm, rather than disperse. Vertical or horizontal shear loads would likely apply more evenly to the weld group.

Edit: to make it clear, the HSS will still be welded all around, but I think it wise to consider a concentrated effect at the top & btm.

 

[bones206]

I used this detail on a project last year, and the erector had a heck of a time getting the beam installed. There were no overhead obstructions and the beams could be swung in, but apparently the thickness of the paint was enough to make it a tough process to wedge the beams in there. Got strong feedback to always spec a gap and shims to make the erector's life easier.

 

[DrZoidberWoop]

Agreed. In-house detailers used to check this type of stuff for us. These days, I have to send a mean email to the team in the Philippines, or wherever, and give them shit about being glorified BIM modelers and hope they make updates in a timely manner.

 

[dik]

Thanks for the weld info; I generally use both horiz and vert and I've often used shims for tight connections. Often it's a matter of sticking a beam into an existing space. I don't design welds 'to the limit'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

It helps if you remove the bolts first...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[DrZoidberWoop]

True haha. Lazy drafter!