HSS Beam Shear Connection to HSS Round Column - Question 1

[SPruitt]

I am a delegated connection design engineer working on some connections on a wind screen on the top of a building with some high shear loads. My current issue is designing a shear connection for an HSS6x6x1/4 beam to an HSS18.000x0.500 column. The highest given shear load is 76 kips (unfactored) with 15 kips axial load. I've looked at several different ways to connect these members and feel like a built up tee connection on the HSS6x6x1/4 connected to a shear tab on the HSS round column is my best option. My concern is the eccentricity of the connection and it's affects on the tee connection and end plate on the HSS6x6. Since the only examples I've found of this connection is for axial load, I want to make sure I check all the parameters for shear as well. I have checked the welds and plate. I am just concerned with bending of the plate connected to the HSS6x6 beam. Any insights would be appreciated.

 

[IceNine]

76 kips seems like an incredibly high reaction for a 6x6x1/4 wind beam.
Have you verified this load with the EOR?

 

[KootK]

We've discussed method for checking the plate bending here in the past, mostly in context of torsion. 76 kip is lot of load to move through that kind of connection however. I'd be inclined to rotate the connection as shown below. Yes, it will suck a bit have to fabricate a plate with a radius cut in it.

 

[DaveAtkins]

First of all, I recommend checking with the Engineer of Record about that beam. 76 kips is a very large shear load for a 6 X 6 tube - in fact, the tube fails in shear.

But to answer your question, I think your connection detail makes sense. The single plate shear connection to the HSS 18 can be checked using the AISC manual. The tee welded to the end of the HSS 6 X 6 must be designed for shear, as well as bending, using an eccentricity equal to the distance from the weld line to the centerline of bolts. AISC Manual Section F11 covers design of rectangular bars, which is what the stem of the tee will be.

DaveAtkins

 

[dik]

Concept's good... maybe more than 1 bolt? Like maybe 6 or more?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[DaveAtkins]

Really, KootK??? 76 kips shear through plates in weak axis bending?

DaveAtkins

 

[KootK]

Really, KootK??? 76 kips shear through plates in weak axis bending?

My understanding is that the 76kips is lateral wind shear given that it's a wind screen. Perhaps OP can clarify. So far, the only sketch posted in this thread is mine.

 

[SPruitt]

The shear is confirmed to be vertical, but I have not questioned the loads as this particular EOR is troublesome and has pushed everything off to me. I questioned the loads on some rod bracing saying the rod size was under-designed and their comment in return was that the design was to be by the delegated design engineer. At this point, I will provide a connection and point out that the beam is under designed. I also have the same issue with a W10x49 beam with 95 kips of uplift, but I believe I have come up with a fix for that.

 

[SPruitt]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1667414125/tips/Built_Up_Tee_Sketch_rtv3zm.pdf[/url]

 

[KootK]

The shear is confirmed to be vertical

Huh, so much for intuitive guessing. So what creates this massive, vertical shear demand? Block wall stacked on top of the girt? Eccentric brace connection away from this one?

 

[KootK]

I am just concerned with bending of the plate connected to the HSS6x6 beam. Any insights would be appreciated.

If geometry permits, a simple way to deal with this might be to extend the plate that forms the stem of your tee such that it overlaps the flange elements of the HSS6x6. That way it becomes sort of a concentrated load delivery mechanism at the plate intersections rather than one that involves plate bending.

In the extreme, you could even replace your tee with a cruciform shape that gets slotted into the HSS6x6

 

[IceNine]

So what creates this massive, vertical shear demand? Block wall stacked on top of the girt? Eccentric brace connection away from this one?

It's difficult for me to imagine any loading scenario that results in a 76 kip end reaction where the HSS6x6x1/4 works in bending, shear, or deflection.

 

[SPruitt]

Here is the layout of the steel. I think I might need to contact the EOR again to verify the direction of the loads.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1667417388/tips/Crown_Steel_Layout_rqa7ol.pdf[/url]

 

[KootK]

Thanks. I would have interpreted that 76k as an axial load. A tie back for the big screen or some sort.

 

[IceNine]

Agree with KootK. Makes much more sense as an axial load.

 

[DaveAtkins]

Agree with KootK and IceNine. This is some sort of massive screen structure. No way there is 76 kips of vertical shear.

DaveAtkins

 

[hokie66]

This is a fine example of why connection design should be done by the design engineer, not left to a remote person who doesn't know the full picture.

 

[dik]

Thanks Hokie... I've been designing connections for a metal fabricator for the last 3 years... I often don't have a full deck... So far, so good...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[SPruitt]

Hokie66 - although it is my job to provide delegated design, a lot of problems on projects could be resolved if the EOR were to do their own connection designs in the first place. Doesn't hurt my feelings at all. I'm good with sticking to simple shear connections designed per fabricator specs. When you have specialized loading, that 100% should be done by the EOR (IMO).

Just as an update, the EOR who sent the first RFI response on the loading no longer works with the company and the new engineer on the project confirmed the loads are axial so that eliminates some problems. Now on to reinforce the 18" dia col so that I don't have to use thru plates.