Single tab moment connection

[JStructsteel]

Anyone have qualms about about a moment frame utilizing a single plate design at the connection? I have designed one for a canopy on a building, so not a massive load. All checks, just wondered if I am missing a better way

 

[271828]

Can you post a figure of one of these?

 

[JStructsteel]

Attached is a section

 

[BAretired]

A better way? Hard to think of anything simpler than a shear tab. It wouldn't work for a serious moment, but it does have some moment resistance.

BA

 

[ProgrammingPE]

That connection is going to be pretty flexible since you are transferring the moment into the middle of the side of an HSS column. Can you use a continuous beam over the column instead? You could also connect the top flanges using a plate and then make the seat angles not optional so that the seats transfer the bottom flange force out to the outside edges of the HSS column.

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[nac521]

Add a cap plate and do all bolted connections - no field welds - cheapest imo

 

[Aesur]

Am I missing something here, why not bolt the beam to the shear plate and weld the top and bottom flanges to the column, less welds = cheaper?

 

[GC_Hopi]

Here is one option. Run the W16 continuous over the HSS if necessary provide a splice plate on the W16 a few feet away from the HSS. Provide a cap plate on the HSS and full height stiffener at the W16 to brace it for LTB, this gives you a moment connection.

 

[HouseBoy]

Seems like the stiffness of the shear tab might be greater than the stiffness of the column but... I don't know which has the greater moment capacity.

Also, W16 seems like a decent size beam too so... I wonder what the "all checks" covers.

Shear tab should provide reasonable stability. Recent posts here have discussed beam stability for beams continuous over columns.

 

[ProgrammingPE]

Aesur, welding the beam flanges directly to the column gives you almost no flexibility for the beam length. You're usually better off having plates shop welded to the column and then attaching the beam to them. Bolting to those plates then means no field welding.

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[271828]

I would only use that if the moment is trivial and if the scenario can tolerate large rotations. In other words, if it doesn't matter if this is a moment connection or not. If this needs to be a moment connection, then use another type of connection.

You can check the HSS wall strength using the 15th ed. Manual Figure 9-5(b). Even if it's strong enough, the end of the beam will rotate a lot relative to the column. It won't have a curve like the Manual Figure 12-1 curve A, B, or C.

 

[JStructsteel]

I have some dimensional constraints, at one end, the beam connects to a column in a wall. Other end is a corner, beam framing in 90 degrees.

I did no check the face of the column, any good references

W16 is beam controlled by deflection limits, also to have a narrow profile.

 

[phamENG]

14th edition has Chapter K in the spec. I understand it went through a big change in the 15th...sounds like 271828 has some guidance for you if you've moved on to that one.

I wouldn't call it a fully restrained moment connection either. It's not a "pin" since you're welding everything (need bolt plowing at ultimate to call it a pin, so no bolts means there's a nominal fixity at ultimate). That puts you somewhere in the partially restrained moment connection zone, or a 'flexible moment connection'.

Doable, but I agree that I wouldn't do it for anything beyond basic stability for small structures or very small wind loads, paying close attention to deflections and deformations within the connection.

 

[JStructsteel]

Thanks,
Yes, small loads, and deflection still ok.

 

[Agent666]

I'd avoid, purely on the basis that your shear tab truely has almost zero minor axis restraint. So a cantilever with nominally pinned connection in major axis and no meaningful minor axis restraint, and you want it to act like a portal in plane... No thanks, no matter how low the loads might be all I see is problems.

What's wrong with a cap plate and moment end plate connection to the bottom flange with beam being continuous over top?

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