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HI everyone,
Part of what I do is review shop drawings for a structrual steel fabricator for cost savings in the shop. The current project i'm working on has some skewed shear plate connection . The angle of the skew is minimal (1 1/2 on 12). The connection plate is 3/8" thick, with squared off corners......not cut on an angle. So when the plate is placed on the column surface and skewed, a 1/16" - 1/8" gap is created on one side. If the plate was perpendicular to the column, a 1/4" fillet weld both sides is all that would be required. My question is should the drawings show a 1/4" fillet on both sides allowing the welder to increase the weld size by the gap or should the drawings add the gap to the weld size? My concern is that the welder is going to see a 3/8" weld called out on the drawings and then add 1/16" - 1/8" to the weld size because of the gap.
Thanks
If you have the AISC's Manual of Steel Contruction(14th ed) handy, check out page 10-161 Fig 10-37, and then flip over to pages10-176 and 10-177 for Table 10-14C. This may be of some help to you.
By 803056 
Date 10-01-2013 16:02
Edited 10-02-2013 08:49
When in doubt, add a detail of the actual condition and the required welds, accounting for the presence of a root opening.
A2.4 permits the use of sketches for the condition you noted. You can also look at the last page of clause 3 showing prequalified T-joints.
D1.1:2010 has additional requirements for skewed T-joints where the dihedral angle between the joined members is less than 80 degrees or more than 100 degrees. It looks like the dihedral angle in your case is about 83 degrees, so you have a every day, run of the mill, not out of the ordinary fillet weld. The welders can simply increase the fillet size to accommodate the root opening on the one side.
Al
Adding a little more detail to the answers you have already gotten from Al and John,
As a TPI I see this configuration all the time. From my point of view the structural drawings will show the required weld size as calculated by the engineer. Then, from those the detailer fills in the gaps by giving the fabrication personnel the dimensions they need to fabricate each member. It will show the skew in this case and the welds required for the welder. The detail will show the increased fillet size on one side to compensate for the gap. So instead of two 1/4" welds the detail will show one 1/4" and one 5/16 or 3/8" fillet depending upon the angle and plate thickness.
As the skewed angle increases/decreases you reach a point where the joint requires a PJP instead of a fillet weld. You will also find the detailer compensating for z loss on those joints so requiring so that the fitter, welder, nor inspector has to deal with those calculations. Z-loss will be dealt with on both sides as it is a factor in the PJP as well as on the acute side of the joint. It is all accounted for.
So, your question will depend upon which drawings you are reviewing. The engineer's structural drawings. The fabrication contractor's shop drawings.
The welder is responsible to complete the work as detailed. It is not his responsibility to calculate the weld sizes. Competent detailers will have all this information on the shop drawings from what the engineer has supplied. Fitters, welders, and in house qc rely on this information to complete the members.
This is why Al has said the detailer needs to show an actual detail of the joint. So that everyone knows the angle and subsequent increased weld sizes have been properly accounted for. Otherwise QC and QA are left to wonder and try to figure it out which is best handled by just requesting an RFI to get the engineer's opinion since no one else's matter. It is not our job as TPI's to try to second guess the process. Look at the responsibilities listed for the engineer and detailers in both D1.1 and AISC Code of Standard Practice. Once the Shop Drawings are complete and approved by the engineer and issued to the shop as approved for fabrication they supplement the structural drawings. If either the fabricator or the TPI has a question about the accuracy of the drawings they need to address the question to the engineer.
I hope I stated this clearly enough to make it understood and didn't just muddy the waters.
Have a Great Day, Brent
Hello Brent;
Skewed T-joints are not typically PJP groove welds regardless of the angle between the parts being joined. Even if the obtuse side is cut as shown in Figure 3.11 (C) [AWS D1.1:2010], the resulting weld falls under the heading of a prequalified weld and a prequalified skewed T-joint provided the conditions of figure 3.11 (D1.1:2010) are met. I suppose if the obtuse side is prepared with an angle less than 80 degrees it could be considered to be a PJP, but some would argue that it is still a skewed T-joint. It is just one of those crazy things that can be debated over a hot cup of coffee or a cold beer until the cows come in to roost.
AWS D1,1:2010 cause 2.4.3 uses the term fillet weld for dihedral angles between 80 degrees and 100 degrees. If the dihedral angle is less than 80 degrees or more than 100 degrees, they simply refer to the weld as a welded skewed T-joint. They do not call it a groove weld or a fillet weld. A standard fillet weld symbol is not fitting when the dihedral angle is less than 80 degrees or more than 100 degrees because the Engineer has to specify the effective throat and the detailer has to calculate the new values for the legs making the necessary corrections per Annex B for angles as small as 60 degrees. If the dihedral angle is less than 60 degree the detailer must account for the Z-loss.
AWS A2.4 shows a sketch depicting a skewed T-joint rather than a welding symbol to define the required leg dimensions, etc.
Best regards - Al
Hi Al,
What do you make of the Weld Details in the lower right corners of Table 10-14C on pages 10-176 and 10-177 in ASIC's Manual of Steel Construction 14th edition? For the 45° skewed shear tab with no plate prep(square cut), they have the joint detailed out as a BTC-P4 Modified.(PJP)
Good morning Al, and John,
And besides the differences in the two codes, it should be noted that engineers often will detail them out and put PJP in the tail of the welding symbol thus designating them as such even if they are not truly so according to the AWS references. And, they factor in the Z-loss when doing so such that a 1/2" plate used for a stiffener will be called out with a 1/2" bevel and a 3/8" PJP weld. It also should be stated that this is normally with skewed welds that are positioned at a 60° angle or less so that the bevel angle would be a 30° angle or greater and the gap referred to earlier is greater than 3/16".
Now, it could be they are just looking for the easiest, cheapest, fastest way around this issue for themselves and the fabricator so they don't have to specify a plate with a cut along the faying surface that would let it sit flat which would also take more time from the fabricator and cause all kinds of complaints. Faster in the long run to deal with it as a PJP by leaving the edge of the stiffener at a 90° original edge cut and fill in the gap as a bevel joint PJP.
Another consideration when this is so called out is that welders who are only qualified to fillet welds are not able to weld the PJP's so they must rotate welders around to complete the work.
This is more an observation as to what I see day in and day out in my work than it is a comment as to the code and reference material distinction/classification of the welds in question in this thread.
Have a Great Day, Brent
I should have also stated that this whole issue just confirms Al's insistence on the engineer and/or detailer attaching a detail of the joint as required by D1.1 and A2.4. It works wonders to clarify what you want and/or expect when dealing with questionable territory within the codes.
Have a Great Day, Brent
Not to throw rocks or boulders at engineers, but too many of them are not well versed with AWS D1.1 or AWS A2.4.
There are several differences between the AISC Steel Construction Manual and AWS D1.1. One difference is that the Steel Construction Manual lags D1.1 by one or two editions. Then factor in that an engineer is no different than the rest of us, i.e., they don't do more than they have to to keep up with recent changes in AWS D1.1. Their focus is on the strength of the member and the connection. Few actually engage in detailing the welds for the connections. That duty is delegated or ontracted out to the lowest priced provided, even if it means there are clear mistakes. The common response I get is, "You know what I want. Change it."
I believe most of us will agree that when it comes to drawings and welding symbols, few drawings have all the weld details shown correctly. It is a common inquiry here at the Forum, "What does this symbol mean?"
Al
>There are several differences between the AISC Steel Construction Manual and AWS D1.1. One difference is that the Steel Construction Manual lags D1.1 by one or two editions.
Everytime that I am called by the (sub-contracted)detailer to answer welding symbol questions during the detailing stages of a project, they have the AISC's manual of steel construction in their hand asking about the prequalified weld details shown in there. They have the latest edition in hand thinking that the info contained therein would be the most up to date. With what those manuals cost...it should be kept up to date.
The engineering handbooks (the name will be left unsaid) are worse yet. I looked at a brand new engineering handbook at a bookstore I frequent several months ago. The welding symbols were at least 30 years out-of-date.
Best regards - Al
I wonder if AISC will be more up to date, with D1.1 going to a five year cycle?
Thanks again for all the comments. I love the amount of feedback and banter that takes place. You guys are great!
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