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RE: SDC D Ordinary Moment frame connection using HSS sections

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I don’t have the latest version of AWS D1.1, but section 5.10 of the 2004 AWS D1.1 only talks about removal of backing plates for cyclically loaded structures and it states explicitly that backing plates need not be removed for statically loaded structures.  While wind/seismic forces may be cyclic in the truest sense of the word, I’ve always taken the definition of cyclically loaded structures to mean bridges, cranes, machinery supports, etc.  Anyone else have any insight on the definition of a “cyclically loaded structure”?

 

From: Gordon Goodell [mailto:GordonGoodell(--nospam--at)harmonydesigninc.com]
Sent: Thursday, August 14, 2008 4:47 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: SDC D Ordinary Moment frame connection using HSS sections

 

Mark,

 

AWS D1.1, provision 5.10 requires removal of backing on welds that are transverse to the direction of stress, but not for welds that are parallel.  Maybe at 45º half of the backing should be removed.  Just kidding.  It is a stress concentrator and inhibits ductile behaviour, and you would not want to leave the backing in a SMF, but maybe OK for an OMF with low force levels.  But D1.1 applies to OMF.  SMFs are governed by the seismic supplement, D1.8, which is more restrictive.

 

regards,

Gordon

 

From: Mark D. Baker [mailto:shake4bake(--nospam--at)verizon.net]
Sent: Thursday, August 14, 2008 1:40 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: SDC D Ordinary Moment frame connection using HSS sections

 

Gordon,

 

Hmmm, in the case of the V, rounding the point of V would aid in reducing stress concentration effects.

 

In the case of tension force at 45 to weld I also am interested in others comments. Could one convince himself that the tension force is resolved as simply as a couple in the plane of top and bottom of beam within column thereby staying out of weld? I guess I’d have to slow down and sketch a stress diagram through the joint to really think this through.

 

To further display my ignorance…..where is it written that backing must be removed when force is at 45 to weld?

 

MDB

 


From: Gordon Goodell [mailto:GordonGoodell(--nospam--at)harmonydesigninc.com]
Sent: Thursday, August 14, 2008 11:18 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: SDC D Ordinary Moment frame connection using HSS sections

 

Mark,

 

If I’m understanding you correctly, cyclical tension force would be at a 45º angle to the weld, so the backing would have to be removed, which could not be accomplished.  Also, there would be a significant stress increase at the point of the V.

 

This is a really good question.  I’d be interested to know how others deal with it.

 

regards,

Gordon Goodell

 

 

 

Mark D. Baker wrote:

 

“In the situation where column meets beam and the column does not continue past beam, cut ends of column and beam at 45, backing can be installed for this joint.

 

Where column does run past beam, cut notch in column in a V shape (female end) and cut end of beam in a V shape (male end) to insert into the column notch. This joint also will be able to receive backing plates.

 

You are correct that when trying to join the beam to the column face, full pen welds are nearly impossible.”