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Up Topic American Welding Society Services / Technical Standards & Publications / Shelf Bar
- - By 803056 (*****) Date 01-29-2010 21:57
Has anyone heard of a shelf bar. It is used when welding horizontal grooves using FCAW-S.

I've seen them used for at least twenty years in the field for column splices.

I just learn that they are addressed in the 2010 revision of D1.1. They are prequalified.

I've always accepted them under the premise that if the engineer allows it, they are golden. No better and no worst than a backing bar.

For static structure, they are left in place unless the engineer wants them removed.

Best regards - Al
Parent - By Duke (***) Date 01-30-2010 01:32
sissy bar
Parent - By ssbn727 (*****) Date 01-30-2010 03:02
Do you mean "Training Wheels?" :) :) :)

Respectfully,
Henry
Parent - - By ctacker (****) Date 01-30-2010 05:04
can we look forward to the 2010 edition in toward the end of 2011?
Parent - - By ross (***) Date 01-30-2010 11:48
April. It will then go on a five-year revision cycle instead of two years.

Ross
Parent - By welderbrent (*****) Date 01-31-2010 02:42
Boy do I like that news Ross.  I didn't personally feel as though it needed such regular revision.  It seems pretty perfected and not needing such regular attention to revisions except for making inspectors and fabricators buy new copies so much more frequently. 

Any minor changes, or even larger issues, should be able to be addressed through the errata system in the Journal and on line. 

Just my two tin pennies worth.

Have a Great Day,  Brent
Parent - - By kipman (***) Date 01-31-2010 01:51
Yeah, I've heard of them.  Duke and Henry are right; they are used to help a welder who doesn't have the skill to cap a butt joint in the horizontal position.  This is one of the reasons my company writes its own structural steel spec.  It is based on D1.1, but we try and fill in what we think are the holes.  For example, the next rev of our spec will contain a statement that shelf bars are not allowed (we never had to address it before).
Regards,
Mankenberg
Parent - - By 803056 (*****) Date 01-31-2010 05:37 Edited 01-31-2010 19:48
It sounds like there are missed opportunities to take advantage of large diameter flux coded electrodes to increase deposition rates.

The welder usually has to utilize FCAW electrode diameters less than 1/16 inch to permit welding when out of position. The use of the shelf bar allows the welder to use larger diameter flux cored electrodes at higher amperages and higher deposition rates. The shelf bar is used for situations typically found when welding butt joints between upper and lower column flanges. It is not unusual for the lower column flange to be thicker than the upper column flange. The shelf is naturally occuring and full advantage is taken of that condition, it is a no brainer. Upper stories of high rise structures or those limited to four or five stories typically have the same thickness flanges for both the upper and lower flanges. It is those situations where the shelf bar makes sense.

Columns are typically subjected to both gravity loads (compression) as well as some minor wind loads (shear), but it is the static gravity loads that usually govern the size of the column and the thickness of the flanges. The shelf bar is nothing more than a backing bar or extension tab to make it easier for the welder to deposit a sound weld without undercuting the flange along the top toe. The column is encased in concrete or fireproofing, so there isn't much to see after the building is completed. The shelf bar has the same influence as the backing bar, i.e., it introduces a mechanical notch, but when the load is static in nature it has no detrimental affect. The same can't be said if the loads are cyclic in nature.

Economy or ego? Economy is the governing factor that should determine whether or not a shelf bar is used. The welder's ego isn't going to put money in the bank or food on the table. If ego ruled the construction world we would still be using SMAW and all welds would be made without backing because it is the macho thing to do. I remember how many welders resisted FCAW because SMAW looked so much better. That line of thought has pretty much gone the way of the GEICO caveman.

Money talks and BS walks, you do it the hard way, someone will do it the easy way and walk away with your lunch. ;)

Best regards - Al
Parent - - By ssbn727 (*****) Date 01-31-2010 16:05
I've got some good Cuban recipes in the OTB&G for you to try for "Lunch" Al!!! :) :) :)

Seriously though, I would think that if one was to use larger diameter wires in order to increase the deposition rates with self shielded FCAW on columns, the use of a shelf bar would more than likely be advantageous in that respect as well as helping the welder to start a decent cover pass as long as the use of these are not to be incorporated at locations where there would be enough seismic activity whereby these columns would no longer be subjected to only static loads exclusively... If potential seismic conditions are present within the are of construction, then a different system would need to be used instead. ;)

Btw, the Cuban Sandwich is an easy one to make, and the "Ropa Vieja" ("Old Clothes!") is really good Al!!! :) :) :)

Respectfully,
Henry
Parent - By 803056 (*****) Date 01-31-2010 19:53
You are correct; the shelf bar is only applicable when static loads prevail. It isn't intended for situations were there are load reversals, impact loading, or where there are dynamic ranges, i.e., constantly changing loads where fatigue is an issue. However, when those conditions exist, the backing bar (as well as the shelf bar) would be required to be removed and ground or some additional conditions are imposed.

Best regards - Al
Parent - - By kipman (***) Date 02-01-2010 13:57
Al,
I appreciate your viewpoint.  I've heard the economic argument also.  It doesn't make complete sense to me, though - you've got to overcome the cost of material (shelf bars), the time to cut them, get them to the workplace, and tack them in place.  You've also got to be willing to live with the limitations on inspectability.  I suppose on a large project the case could be made that it is worthwhile to do all that.
My perspective is skewed by the fact that we have nothing that is considered static.  Most of what we do is seismic service, and all of it is subject to wind and wave fatigue loading in a corrosive environment.  It has nothing to do with ego - there is no place for either shelf bars or welders who can't cap a horizontal butt joint.
Regards,
Mankenberg
Parent - - By trapdoor (**) Date 02-01-2010 14:48
I agree with Al as far as a shelf bar and economy, and I don't think it gives much of a crutch to a welder who wouldn’t be able to weld a decent horizontal butt weld that requires more than one pass for the cap anyways.

My only question is if one were to weld out a shelf bar of 1/4" would you have to grind the weld of the excess 1/8" of reinforcement? Or is that going to be addressed in the new edition of the code as well?
Parent - - By 803056 (*****) Date 02-01-2010 15:52
The use of the shelf bar isn't for everyone. As noted by Kip, it wouldn't be applicable for his environment.

As for the face reinforcement, the 1/8 inch maximum face reinforcement applies to butt joints. However, while the shelf bar is used with butt joints, it will not have to meet the 1/8 inch reinforcement limitations based on what I was told.

Best regards - Al
Parent - By trapdoor (**) Date 02-01-2010 21:26
Being allowed to have more than 1/8" reinforcement makes sense with a shelf bar, otherwise I don't know if it would be worth it.
Parent - - By pipewelder_1999 (****) Date 02-04-2010 03:33
Here is some information that is old that can add a little to the topic.

http://files.aws.org/technical/interps/d1-85-018.pdf
Parent - By 803056 (*****) Date 02-04-2010 05:56
So, in reality, they are nothing new.

Good work.

Al
Parent - By waccobird (****) Date 02-04-2010 10:46
pipewelder_1999
Thanks for the link
Marshall
Up Topic American Welding Society Services / Technical Standards & Publications / Shelf Bar

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