So, here is a question I have wrestled with for a considerable time...

I would bet that most everyone has heard this same phrase, 'All fillet welds are Pre-Qualified'.  Really?  So, why don't we take a close look at the wording from D1.1 ?  But, first, another aspect of this to make sure we are all on the same page.  Lets describe a SPECIFIC FILLET WELD .  We are going to look at a T-joint for a stiffener plate 3/8" thick 4" tall by 18" long.  The weld symbol depicts a 5/16" fillet weld both sides on all three sides.  So, a 90° angle of the stiffener plate to the web of the wide flange beam with fillet welds to the top and bottom flange and the web.  Just for the sake of argument, let's call this A992 Wide Flange with a stiffener of A-36 flatbar.  And we are dealing with D1.1 and an acceptable process. 

Next, we need a WPS.  Is this a Pre-Qualified Joint?  Pre-Qualified Joint and Weld Combination?  I ask the second because the answer to the first would be 'YES'.  I base that upon Prequalified Details TC-U4a, B-U5b, TC-U5b, and others.  The Joint is Prequalified if that is the only part of the question.   But, I am not after a PJP nor a CJP Joint.  I want to know about a T-Joint with ?SIMPLE? fillet welds.  So where to start?  Please follow my train of thought...

1) Clause 2.2.5.1 starts us out with the requirements for Shop Drawings for various Fillet Welds and Skewed T-Joints.  Plain fillet welds are between 80° to 100°.  Skewed fillet welds are less than 80° and greater than 100°. 

2) Clause 2.3.3 takes us to the next step with more defining of skewed fillet welds and tells us they are indeed prequalified and informs us there are details in Figure 3.11. No where in this Section and it's sub-sections nor in Figure 3.11 do we find anything about fillets in angles between 80° and 100°. 

*What some may be able to learn from these sections is that we as inspectors do not normally need bother about Z-loss and other calculations.  This points out clearly that the engineer in the Contract Documents calls out the Effective throat from which the Fabricators and Erectors detailers are to calculate the skewed angle, welding process, Z-loss and call out a fillet weld leg size for the welders and inspectors to comply to.  Without cutting and macro-etching you have no accurate way to make sure the welder accomplished the effective throat requirement.  That is why welders need to be properly qualified and all perameters strictly adhered to so that we can be reasonably assured the acceptable weld has been made. 

3) Clause 2.8 Takes us through more requirements to do with fillet welds.  ALL have to do with fillets in lap joints as do the applicable Figures 2.1, 2.4, 2.5, 2.6, 2.7, and 2.8.

4) Now lets go to the previously mentioned (from another thread) Clause 3.9  Fillet Weld Requirements.
Here we find several factors:
  a. Minimum sizes are found at Table 5.8, but nothing about the T-joint with a fillet weld being prequalified;
  b. 3.9.1 Details for Nontubular where it sends us to Figures 2.1 & 2.4.  Well, those are for lap joints. And the text of 3.9.1 says that this is the "limitations for prequalified fillet welds."  NO T-JOINTS MENTIONED!;
  c. The next sub-clause, 3.9.2 is for Tubular and does not apply to our question;
  d. Sub-clause 3.9.3 goes into the Skewed T-Joints and is not what we are dealing with except to add that it takes us to Figure 3.11 which along with Figures 3.5 thru 3.10 only confirms the pre-qualification of skewed joints and their applicable fillet welds in tubular and non-tubular applications with angles and bevels that apply; and
  e. Table 3.7 gives us sizes for Single Pass Fillet Welds and a Table titled Prequalified WPS Requirements. But, those requirements can be applicable to the fillets in skewed joints with obtuse or acute angle fillets per previously mentioned Figures.

SO, what have I missed?  Where does one single Clause or Sub-clause put a T-joint fillet weld into the Pre-Qualified classification?  I see it totally excluded from any applicable prequalified detail.  The extent of details, text, and tables describing applicable variables for being prequalified being what they are, how can this joint be prequalified when it is nowhere listed, detailed, or described?

Thus, are fabricators supposed to get a PQR on a T-Joint welded with a fillet weld in order to write a WPS that will be applicable to the work described at the beginning of this thread? 

If not, show me where the code states they are prequalified. 

Finally, I have tried thru the years to include this joint in many of the clauses and sub-clauses already mentioned but in reality, it can't happen.  It is very clear that this precise configuration has been left out.  Now, if someone can show me where I have missed something, GREAT!  But, I have been coming across more and more inspectors raising the same question and wondering where it is justified to call this SIMPLE T-Joint with fillet weld a prequalified combination. 

What say ye gentlemen?? 

Have a Great Day,  Brent

Gentlemen;

Attached is my understanding of skewed joints and the weld joining the intersecting members;

Fillet Welds - Base on AWS D1.1:2010

Starting with a clean slate, no preconceived notions about the status of prequalification other than to determine if a fillet weld is prequalified.

Starting Point
Clause 3.9 - Table 5.8 for minimum acceptable fillet weld sizes based on base metal thickness
Subordinate Clause 3.9.1 Details (Nontubular) – See Figures 2.1 and 2.4 for the limitations for prequalified fillet welds.
  Figure 2.1 – lap joint and max, fillet size
  Figure 2.4 – lap joint and min lap length / double fillet to prevent rotation

Subordinate Clause 3.9.2 Details (Tubular) – not at issue, so skip

Subordinate Clause 3.9.3 Skewed T-joint – conformance with figure 3.11
Figure 3.11 depicts several skewed T-joints with different dihedral angles. Notice the dihedral angle of figure (A): 60 degree min. 
We have the following: The figure allows any acute dihedral angle larger than 60 degrees – up to a maximum of 90 degrees at which point the dihedral angle is obtuse, i.e., more than 90 degrees.
Continuing with same figure; the obtuse dihedral angle must be less than 135 degrees, which includes everything down to and including 90 degrees. Anything less than 90 degrees takes you back to my previous paragraph.   

Conclusion:
All the conditions and requirements of a prequalified fillet weld is contained in clause 3.9 including the subordinate clauses with a reference to Figure 3.11. Any nontubular connection where the butting and nonbutting members intersect at any angle is considered to be a skewed T-joint per clauses 3.9.3 and 2.4.3. When the dihedral angle is more than 80 degrees, but less than 100 degrees the joint is simple called a T-joint by most people and it can be joined by a prequalified fillet weld(s) without any additional considerations regarding the detailing/sizing of the weld. That is to say, the weld is simply specified by the leg dimension.

The weld joining the intersecting members are still prequalified when the acute dihedral angle is between 30 degrees and  80 degrees, however, the weld must comply with additional requirements regarding the detailing and dimensions of the weld. Likewise, the weld on the obtuse side is prequalified provided the details comply with the details of Figure 3.11.

Clause 2.4.3 provides the designer with the information needed to properly detail the weld (sizes) joining the intersecting members of skewed T-joints (includes T-joints). This clause references Figure 3.11 for prequalified fillet welds, which includes details A, B, C, and D.

The weld joining two skewed intersecting members is prequalified if the conditions of clause 3.9 and Figure 3.11 are met. The detailing of said joint must be in accordance with clause 2.4.3.

If here is  problem, the problem usually lies with the detailing of the joint by the detailer. Per D1.1, the fillet weld is only prequalified for skewed angles of 80 min degrees to 100 degrees max. Other than that, the prequalified weld is no longer a fillet weld, but is simply a weld in a skewed joint. If you read clauses 2.4.3.2 and 2.4.3.3 and 2.4.3.5 carefully, you will note the term fillet weld is not used.

Best regards – Al

Skewed T-joints have changed slightly with the release of each new edition during the last decade.

The 2002 edition include a number of changes in the requirements for skewed T-joints. The code defined a skewed T-joint in clause 2.3.3.1 as any T-joint in which the angle between joined parts is greater than 100 degrees or less than 80 degrees.

In the next clause, 2.3.3.2, the code has requirements for acute angles between 60 and 80 degrees that states the design drawing must specify the required effective throat while the shop drawing must specify the required leg dimension. This was new, something different from past practice.

Interestingly, nether clause called the welds "fillet welds".

Clause 2.3..3.3 adds the Z-loss for skews between 30 and 60 degrees. Skews where the angle is less than 30 degrees were not permitted to transfer applied forces.    

In short, the requirements for the design of skewed joints was very similar to what they are today.

The Figure 3.11 was as it is in the current edition. The labeling looks the same as in the current edition. Figure 3.11 (A) indicates the acute angle must be 60 degrees or larger, the obtuse angle 135 degrees or smaller. As such, it includes the 90 degree T-joint just as it does in the current edition.

Figure 3.11 (B) is the same as it is currently and it still includes the 90 degree T-joint.

Figure 3.11 (C) shows the obtuse side of the joint where the obtuse angle is greater than 100 degrees prepared so the welded portion of the joint has an included angle of 60 to 90 degrees, as it still does.

Figure 3.11 (D) shows the acute side of the joint larger than or equal to 30 degrees, but less than 60 degrees and where the acute angle is welded with the Z-loss indicated.

Clause 3.9 includes fillet welds other than reinforcing fillet welds used in conjunction with groove welds, but subordinate clause 3.9 does not include a reference to "fillet welds."

Back to the 2010 edition of AWS D1.1:

Had D1.1 used the heading 3.9.3 T-joints, there may be less confusion. In my mind the skewed T-joint is nothing other than a class of T-joint that has additional requirements imposed. I believe much of the confusion stems from some individuals insisting on calling a welded skewed T-joint a "fillet weld." I refrain from calling the weld on the acute side of a skewed T-joint a "fillet weld" when the acute angle is less than 80 degrees. Likewise I refrain from calling the weld on the obtuse side of the joint a "fillet weld" when the obtuse angle is greater than 100 degrees.  It is consistent with the terminology of recent and current editions of D1.1.

It may be easier to understand what welds are prequalified if people would simple eliminate the word fillet weld from their vocabulary when speaking of skewed T-joints when the dihedral angle between the adjacent members is less than 80 degrees or more than 100 degrees. The current edition of D1.1 does not use the word "fillet" when addressing dihedral angles of less than 80 degrees or more than 100 degrees. They are simply welded skewed T-joints. They are not fillet welds and they are not groove welds, they are something unto themselves.

So, is a skewed T-joint prequalified? My response is yes, if the requirements of clause 3.9.3 and Figure 3.11 (A), (B), (C), and (D) are met. If the dihedral angle is between 80 and 100 degrees the joint is a "T-joint, if not, it isn't a T-joint, but it is a skewed T-joint.

In closing, is the skewed T-joint a subcategory of a T-joint or is the T-joint a special subclass of a Skewed T-joint? I submit the T-joint is a subclass of the skewed T-joint.

Back to the original discussion: "How many fairies can dance on the point of the needle?"

Best regards - Al