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RE: Full Pen Weld at Channel

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Dave,
I had the advantage of working in a steel shop with a very good fabricator of stairs (old guy who knew what he was doing).  He was very meticulous.  What I did with my weld call out was mimic the weld he routinely provided.  After I became an engineer, I then put his weld into a symbol with a prequalified PJP weld augmented by notes.  I then bounced my weld call out to inspectors and welding engineers like Bob Shaw and then back to some good shops for their input.
 
As a former welder, welding inspector, and now a half fast structural engineer, the weld I call out is about the best I could come up with the help of people who really knew their stuff (welders, inspectors, code guys). 
 
I don't mean to criticize, but I do not understand how you call the weld that you suggest is a square butt weld but then call out a single bevel?  It is either a square butt or a bevel weld.  Any square butt weld has a very small thickness limitation.  The thickness will be 3/4" (MC 12x10.6;  k=3/4") and a maximum allowed for any prequalified CJP square butt SMAW is only 1/4".  A 60 degree single bevel will require a lot of weld deposit material, a lot of grinding or a bevel cut, and will probably limit the welder to a SAW process.  I don't know of any 60 degree prep that you can use a SMAW, GMAW, or FCAW (which are the most common shop processes).  Not that many shops can do a SAW by hand.  Backgouging is another process that is difficult especially as you approach the fillet.  Again, I do not intend to criticize.  If it works for you that is fine.  You may want to get some feedback from the inspectors for their interpretation. 
 
You are correct in that the weld you indicate is not a CJP.  It will be a PJP.  CJPs often trigger difficult NDT.  The NDT is especially difficult if radiographic or UT is required.  Frankly, I do not know of an easy NDT for this particular kind of weld.  That is another reason that I prefer to require visual inspection.  The inspector will observe the set up and the process to assure that the engineer gets the effective weld indicated.  Another challenge is that the flange thickness varies.  That is why I indicate the E to be the material thickness minus 1/8". 
 
I prefer not to show the angle, root opening, or process.  I leave that up to the shop and only show the effective thickness that I know that the shop can provide.  That makes it easy on the welders, the inspectors, and most of all ...me. 

Regards,
Harold Sprague

From: jatech(--nospam--at)telus.net [mailto:jatech(--nospam--at)telus.net]
Sent: Monday, October 13, 2008 3:52 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: RE: Full Pen Weld at Channel

 

For the last 45 years I have called for a square butt weld on both sides of the web and a 60 degree single bevel with zero gap and zero root face along with a backgouge symbol for both flanges. I know it's not a CP weld so I don't call it out as one.
 
These stringers are also called "cranked" in some areas.
 
 

Dave Lowen
jatech(--nospam--at)telus.net
Alberta 780.470.5187
California 510.550.7514

 
 
On Oct 13, 2008, spraguehope(--nospam--at)hotmail.com wrote:

This is a common issue.  This is also known as a broke back stair stringer.  Be careful so that you get what you intend.  If you truly need a full pen weld, then specify what you need.  If you get a true full pen weld, you will then have run off tabs and you will have a weld access hole through the web.  It will not be pretty.
 
Now the architect will hate that hole and point out that no other broke back stringer in existance will have a weld access hole, and he will be correct. 
 
You as the engineer have a dillema.  Swimming upstream in the world of convention or engineering something that will satisfy most everyone. 
 
I have had this conversation with a lot of welding and fabricating gurus and resoved to the following:
Show a PJP weld symbol with E in the spot indicating the effective weld thickness.  In the tail of the weld symbol indicate:

PJP  E=MTL THICKNESS - 1/8"
WELD ACCESS HOLE NOT REQUIRED
NDT NOT REQUIRED
VISUAL INSPECTION REQUIRED
 
Show the same weld symbol for the web weld.  Calculate if this is sufficient for the weld you need. 

You can have it ground flush if required. 
 
The above weld will have a prepared beveled surface.  It will be close to a CJP, but not quite.  It will look like all of the other welds out there on stair stringers, but you will have some idea of what you have.  The vast majority of these welds existing in the field are just butt welds that are not prequalified and you have no idea of the thickness of the effective weld. 
 
Go to any project where there is a broke back stringer and you will not find a weld access hole even if the weld was specified as a CJP.  It makes you wonder what weld was provided.  At least with the notes that I now use, I am getting a definable weld and it is inspected. 

Regards,
Harold Sprague



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