moment connection details

[jay156]

Sorry if this has been asked already. What details do you guys use for moment connections? Specifically for beam to beam connections. I've been using the standard one from the AISC 9 manual like in Detail 1 of the attached sketch. For beams to columns, I really like welding end plates to the beams and bolting them. So I was thinking, would it maybe be better to use something like Detail 2 for beam to beam connections? I would think it would be easier to erect, at least for new construction, because all the welding can be done in the shop. Can you think of a reason it wouldn't be any good?

Also, share any other clever details you like to use.

Thanks

 

[structSU10]

So you are putting a moment connection into a beam with no moment connection on the other side? It seem the torsion in the other beam would limit greatly the effectiveness of the moment connection. What you show could probably work, its just the beam you are framing into would twist like crazy.

 

[delagina]

i usually weld it.
yes, like poster above, you need another beam on the other side to counter torsion.

 

[jay156]

Am I wrong in thinking that if you size the beam you're framing into large enough to withstand the torsion, you wouldn't need another beam on the other side?

 

[structSU10]

Well you certainly could size it for torsion, but with a WF, depending on the span, it will rotate a lot. The rotation can effectively negate the fixity created.

If you have structural software try modeling a fixed-fixed beam framing into to cross beams. You will find that even when you make the cross beams large, you generate almost no fixity at the connection due to the torsional flexibility of the cross beams.

 

[JoshPlumSE]

Wide flanges are so weak in torsion that I'm not sure you'll have much success without framing a member on the other side. Also, anytime you are imparting a significant torsional load into a wide flange, you should consider the effects of torsional warping. These can produce extremely large weak axis bending stresses in the girder.

All in all, I'd say it's a lot easier (and cheaper) to add a member on the other side which resists the moment.

 

[jay156]

One time I analyzed a train unloading platform that had a single beam moment framed into another with nothing on the other side. The loads were small, but so was the beam, so I had them weld on a cover plate from flange to flange, effectively turning half of it into a rectangular tube section. In that case there was just no way they could frame a beam in on the other side because there was nothing there to support it.