D1.8 Welder Quals.

Date 07-29-2013 20:29

Hello Farmin,

Yes, the removal of the backing bar as well as the backwelding is done in the overhead position to simulate both the WPS and conditions that will be required for field completion of these joints.

The option to leave the backing is because in the shop they have the ability to roll the beam and they are not using the weld access hole to weld through. According to Clause 5.1.1 of D1.8 all three conditions must be met in order to be REQUIRED to do the supplemental testing. Many welders in shops need not be Qualified to D1.8 because not all three conditions exist. Many of the CJP's on these projects are not Demand Critical and/or are not through a weld access hole. Not to mention that it really limits the application when they are also for the attachment of the bottom flange only.

Not all of these must have the backing bar removed and get welded from the other side. But, when they do, that is how the test must be done even though the shop has the ability to roll the part and do the weld down flat. Most of the shops I have been inspecting at just put both backing bars on the inside of the stub and weld from the outside. No removal required and all welding is downhand.

Have a Great Day, Brent

By farmin72 (*)

Date 07-29-2013 23:23

Thanks Brent for that information. I think misread the part about the 3 criteria for needing the supplemental qualifications. I had my welders who would be doing those joints qualify for that anyway just in case. For some reason I was thinking it was anyone of those items but I was obviously wrong. In your post you said they would put backer bars on and weld down hand. What would be the benefit in doing that? Less heat or am I way off?

By welderbrent (*****)

Date 07-30-2013 03:37

Most of the time the joint in question will be a single bevel groove weld with backing. Instead of welding through the weld access hole, which would then require the welders to be qualified per the supplement, you put the backing bar under the joint from the access hole side of the joint (requires the web to be ground down really smooth thru the center so the backing bar fits good and snug and flat). Then, you weld one side from the downhand/flat position, roll the member, and weld the other side from the downhand/flat position. Neither is welded throught the access hole so even if it is a Demand Critical weld and one is the bottom flange it does not fall into the all three category. Also makes it easier to UT after welding as both can be done from the outside of the flange with the backing bar on the inside.

Single bevel groove welds without backing are prohibited, unless welded from both sides which brings us back to the weld access hole and the supplemental qualification.

2.17 Prohibited Joints and Welds
2.17.1 One-Sided Groove Welds. Groove welds, made
from one side only without backing or made with backing,
other than steel, that has not been qualified in conformance
with Section 4 shall be prohibited except that
these prohibitions for groove welds made from one side
shall not apply to the following:
(1) Secondary or nonstress carrying members.
(2) Comer joints parallel to the direction of calculated
stress between components of built-up members

Have a Great Day, Brent

By farmin72 (*)

Date 07-30-2013 12:56

Thanks again Brent, i think i have a lot to learn about D1.8. I had our welders do the option A with backing and no removal of it so they pretty much can't backgouge on the actual job in the shop since they didn't backgouge on the test is what im thinking, unless one of the variables of section 5 in d1.8 are removed from the equation is basically how i am understanding it now, correct? Im just going to try to eliminate at least one of those variables when i can so they don't have to use the supplemental qualification. I do however have another question. Is there a good answer on when a backing bar if used has to be removed or can remain in place? I have not been able to locate and answer on it but i am sure with your wealth of knowledge you would have an answer.

By welderbrent (*****)

Date 07-30-2013 20:47

Look at your D1.8. Clause 1.2.1 (5) and for that matter (7). Backing bars and runoff tabs are to be noted by the engineer if they are to be removed.

Then, (6) states that if the backing bars that are left in place need a fillet weld the engineer is to note those locations.

It is not left to the shop, in house inspectors, nor TPI. It is totally above our paygrade. Not that we can't RFI a change that will more than likely be accepted if there is good reason to remove instead of leaving a backing bar.

Now, one main shop I do TPI work in specifies in their QC procedures that runoff tabs are removed. That is their standard practice. Always acceptable, though not always required by code/engineer. Backing bars are left in place unless removed to repair a root pass discontinuity discovered by UT. On heavier continuity plates it is easier to go in from the backing bar side than to take everything out from the weld face side.

This is also the normal case with D1.1, not just D1.8.

Check out one other thing: Not all CJP welds done on a SFRS system to D1.8 are Demand Critical welds. Thus, in the case of your three conditions for requiring the supplemental test you are already out of the category.

Demand Critical, Seismic, Cyclic are NOT synonyms/synonymous. Separate also is the Protected Zone. A close examination of D1.8 and AISC Seismic Design Manual 348 is critical to understanding what is going on and why.

Have a Great Day, Brent