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RE: Moment Frames with Slip Critical Shear Connection[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Moment Frames with Slip Critical Shear Connection
- From: "Jordan Truesdell, PE" <seaint(--nospam--at)truesdellengineering.com>
- Date: Mon, 26 Jul 2004 10:45:36 -0400
You're forgetting the "luck" which allows contractors to make such arguments. Every bolted connection will have a friction force. Most will act as slip-critical depending on the exact torque & interface conditions. The question is: will your joint fail if it undergoes translation in the plane of the interface with no bolt shear resisting force?
Codes and standards practices are just documents written by people so that those without engineering knowledge can have some handle on the situation, and should not be a substitute for actual engineering. There's an old saying that rivets should never be used in tension and bolts should never be used in shear. There's a good reason for that in applications where you're taking the material to its limits. Bolts act ONLY in friction until metal-hits-metal, and friction is far too variable to count on for life safety. Think of a 4 bolt shear connection (2 per angle). Just looking at the tolerances in steel erection will show you that the odds are good you'll only have one bolt shank actually in contact with both the angle and the parent member on each side. That bolt or the parent material must begin to fail before the second bolt carries load across its shank.
Answer the question in the first paragraph, and you'll be most of the way to your answer.
(Don't even get me started on earthquake analysis. Factor this...factor that...apply the special frame fudge factor on Tuesdays. Random vibration analysis is not black magic, it's just "too hard" for most people to understand. Heaven forbid we should have to be be knowledgeable in difficult disciplines.)
At 09:25 AM 7/26/2004 -0500, you wrote:
Can anyone show me bodies to support this theory? I mean that quipped question with honest intentions as it is usually the response I get to the opinion I gave earlier. Yet I ve not seen it and I am yet to have anyone show me a case when asked. With all of the old A307 and more current HS bearing joints used in this case, surely we d have seen something by now if the theory were of real concern.
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