Beam to HSS Column Connection via WT 1

[ChiEngr]

Hello,

I am working on a WF beam to HSS column connection that I am hoping to achieve through a WT element. My question is with regards to whether it is reasonable to assume this connection to be "pinned." The connection is subject to axial force, vertical shear force, and horizontal (out-of-plane) shear force. I am planning on welding the WT all around to the workable flat of the HSS column. However, I am wondering if I am hindering the rotational ductility of the connection by doing so. I don't think it does, given that I can idealize the flange of the WT as an extension of the HSS wall, with the stem being a "shear tab".

I would greatly appreciate any thoughts you all might have on this condition. Thank you!

 

[dik]

For bolts on the ST stem, I calculate the bolt forces using the eccentricity of the fastener group, and use that for design of the connection.

 

[KootK]

I take your point regarding the similarity of the WT flange to the HSS wall. Still, I'd be inclined to leave of some of the welding at the top to mimic what we do with double angle connections to improve rotational ductility there.

 

[ChiEngr]

Thanks, KootK. This is actually what I am planning on doing barring the calcs working out.

 

[271828]

The 16th ed. AISC Manual has a new part -- Part 12 -- on "Simple Connections for Combined Forces." It talks about some of the issues.

I'm leery of the approach you're proposing because:

1. If you leave the welds off the top of the tee flange, then your connection seems a lot like Figure 12-2(a), which is one of the examples of what not to do.
2. If you weld across the top of the flange, then you'll need to do something else to ensure ductility. You could try to treat the stem like a shear tab and satisfy the max thickness from Table 10-9 or tmax from Eq. 10-6.
3. I assume you're thinking of a WT, not a tee built up from two plates. Tee stems are usually thin. You mentioned lateral loads. When I've designed single plates with lateral shears, I've often had to bump those up quite a bit, such as PL1/2, Grade 50, even for modest lateral shears. If you have to make the stem thick, then that screws up the ductility check mentioned in #2.

From my vantage point through a keyhole (LOL), I'm curious why you wouldn't use a shear tab. That would be the typical choice. There is at least one example of one of these with combined loads in the Companion to the AISC Steel Manual, Volume 1; it doesn't have lateral shear, though.

 

[271828]

One more thing. There are some tee examples in the Companion Volume 1.

K.1
II.A-30
II.A-31

They demonstrate rotational ductility checks from Part 9. They also show the bolt eccentric shear check methodology.