Existing Double Angle Connection Welded on top and bottom
Existing Double Angle Connection Welded on top and bottom
(OP)
I have been asked to analyze a double angle connection that has been welded on the top, side and bottom. How do I do this? AISC examples only recommend welding on the side and a partial portion at the top to the supporting member. Please provide guidance. This is supposed to be a simple shear connection. Thanks






RE: Existing Double Angle Connection Welded on top and bottom
Dik
RE: Existing Double Angle Connection Welded on top and bottom
If it's pure shear, then use the Instantaneous center of rotation method same as any other connection.
Now, I suspect that this connection may have some axial load as well. That being the reason for adding the weld along the bottom. In that case, the instantaneous center of rotation method gets if not impossible to solve, then close to it. Therefore, you would revert back to an elastic solution method for the connection.
RE: Existing Double Angle Connection Welded on top and bottom
RE: Existing Double Angle Connection Welded on top and bottom
The worse thing you have to worry about is the "rotational ductilty" check. Meaning that the connection may be more rigid for rotation than a shear connection would normally be assumed to be. What are the implications of this? Maybe imparting some moment into the girder or column supporting your beam.
RE: Existing Double Angle Connection Welded on top and bottom
For what it's worth, the Canadian steel manual still shows welds on all three sides for this connection based on some research done at the University of British Columbia some time ago. The connection gets designed and constructed that way here often and, to my knowledge, problems do not result.
Practically, I'd expect unanticipated end moments in the beam to be of little significance. You have them until the upper weld gives way and then I'd expect the moments to redistribute without incident. And, based on past performance, typical beams seem to be designed stiff enough to prevent even the weld damage from occurring.
I do realize that nothing that I've shared here necessarily gets you street legal in terms of US code acceptance. Hopefully some it will help to inform your judgement on the issue should it come to that.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Existing Double Angle Connection Welded on top and bottom
Dik
RE: Existing Double Angle Connection Welded on top and bottom
The rotational ductility concerns have always bothered me. I feel that research in our field is, of necessity, mostly reactive. Stuff goes wrong and we figure out how to deal with it. Unless there are a bunch of related connection failures in the field that I'm unaware of, the rotational ductility business seems proactive to me. The answer to problems that have not yet organically manifested themselves.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.