Directly Welded Flange Moment Connections

[port125]

I am doing the connection design for several Directly welded flange FR Moment connections, when I break the resisted moment into the tension and compression components I find that the beams flanges are not adequate to handle the forces.

Does anyone know if we can use the beam web connection to resist the remaining moment? Also are there any good references that illustrate a similar problem?

A similar connection is solved out on the AISC 13 reference CD, however they never run a check on the beam flange.

 

[JAE]

I would think then that you'd have to upsize your beam to accommodate the connection needs.

You are taking a uniform stress pattern on the whole section and...as the stresses approach the end connection....requiring the stress to flow totally into the flanges and out through the weld.

 

[WillisV]

I believe your question regards the fact that the full moment capacity of the beam can't really be developed by just the flanges - this is an acceptable condition and is addressed here: thread507-225286

 

[JAE]

WillisV - I read the link - it pertains of course.

But I note that in the latest AISC 13th Edition it is altered - now if we read the commentary for Spec section B3.6, there is a bit of discussion on the issue of the connection going ductile prior to the beam itself - and the difference between FR and PR connections appears to kick in.

I didn't read it real close - but do you think this is relevent to port125's question?

Also, I would think it very relevent whether the moment is due to wind or due to seismic.

 

[WillisV]

JAE - I looked and I don't think that discussion is really relevent in this instance. I think his question was limited to basically the classic flange welded (aka pre-northridge) moment connection developing the full moment of the beam despite the apparent lack of that capability in just the flanges.

I agree seismic loading is relevant, but I think the main point is if its not designed as an R=3 system, this connection would not be allowed (without dog-boning or some other means of fuse induction).