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Weld symbol
5

Weld symbol

Weld symbol

(OP)

I've got 2 HSS sections (of the same size) I'm piggybacking on top of each other. I'm connection them by welding them along their lengths where they meet. What you would essentially need are 2 flare welds.......but I'm not sure I've seen a symbol like that before. Any ideas?

RE: Weld symbol

Yes. Opposing flare welds, and I would also show them ground flush if appropriate.

Mike McCann, PE, SE (WA)


RE: Weld symbol

That you're looking for is called a flare vee weld. The symbol looks like a flare bevel, except instead of a straight line on the left side, there's a mirror image of the flare shape from the right.


RE: Weld symbol

(OP)
Thanks guys!

RE: Weld symbol

If you're doing something seriously structural with these welds, I'd recommend calling out the effective throat: (X). Flare bevel welds are notorious for not having enough throat.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Weld symbol

I always wondered when you specify the minimum throat, how do you assure you are getting that penetration? You can't tell with a visual.

RE: Weld symbol

Great question Buggar. Hopefully someone knows the answer. I'm a little gun shy with flare bevel because of some forensic work that a did where a bunch failed. We cross sectioned some as well as some newly fabbed test specimens. All had substantial void behinds the weld throat.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Weld symbol

We have a General Note that requires the effective throat of all flare bevel welds to be 5/8 times the thickness of the HSS wall.

RE: Weld symbol

Assuming you're governed by US codes:

Flare bevel and flare vee welds are PJP welds. If you look in AISC 360 table J2.2, they show the effective weld sized for flare bevel and flare vee welds as a function of process, position, and radius. This information is also in AWS D1.1 Table 2.1. Depending on those variables, the weld size (formerly known as effective throat) ranges from 5/8R to 5/16R. The rule of thumb I was taught, although I can't cite a source, is that the outside radius of A500 tube is typically 2 times wall thickness. So, to KootK's point, the code expects a substantial void behind the weld - you just can't reliably penetrate into the acute angle at the root of the joint. It's on the engineer to design for that throat.

As for how the contractor establishes that throat, they have two options. they can use a prequalified joint (B-P11, B-P11-GF, or B-P11-S) and use the somewhat conservative weld sizes specified (5/8R, 3/4R, and 1/2R respectively) or they could qualify a procedure, which would require them to macroetch sample welds to establish the weld size.

RE: Weld symbol

(OP)

Quote:

If you're doing something seriously structural with these welds, I'd recommend calling out the effective throat: (X). Flare bevel welds are notorious for not having enough throat.

Good point. I usually handle (with flare welds) that by putting a convex on top of the weld symbol (I also typically do that with full pen welds). That typically rounds it out enough to where it makes up for any void in the corner.


RE: Weld symbol

My information is a few years old and is Canadian. Is effective throat not a thing any more? From a design perspective, should one assume the worst case position, process, and HSS bend radius?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Weld symbol

KootK, AWS renamed 'effective throat' as 'weld size.' I have no idea if CWB did the same. As far as I know, only the name changed, not the concept.

As for assuming the worst, it might be better to specify the weld size you require, and make it the contractor's problem to use an appropriate process and position. Especially if it isn't a field weld, they should be able to do the weld in a process or position that gets you better than the worst case.

RE: Weld symbol

Msquared, page 6 of the link you provided says the following:

"If the penetration of the weld is to be greater than the depth of the groove, the depth of the effective throat is given in parentheses after the depth of the V."

I've never seen the penetration depth (effective throat) be more than the groove depth. I have always seen it the exact opposite, like you have a 1/2" groove depth, but because of the weld process or position, you only have 3/8" effective throat. So the weld size would be 1/2(3/8).

Has anybody else seen an effective throat larger than the groove depth?

RE: Weld symbol

Does anyone actually specify the type of weld on your drawings? I was taught to never specify the type of weld (unless there is a specific and good reason to do so) unless it's a flare bevel or fillet. If you need a PJP, just call out PJP and the effective throat you want and let the fabricator choose what his shop is set up for. Same with CJP - just a weld leader with CJP in the tail.

The shop drawings should show all of this information so you can verify it makes sense with welding types and procedures, but not on my CDs.

RE: Weld symbol

(OP)
How would you specify a minimum throat thickness? just have it as a [fraction] next to the weld symbol? Or should it be specified as a minimum depth in the general notes?

RE: Weld symbol

Effective throat is always shown as a size in parentheses to the left of the weld symbol.

Lion06 - we show welds types on our drawings when we specify particular connections - in our view it is part of the EOR design requirements per AISC Code of Standard Practice to show all required information (when we design the connections) (see commentary on 3.1.2 of the Code of Standard Practice).

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RE: Weld symbol

There are only 2 ways AWS allows a weld to be Full-Penetration (CJP) in their prequalified welds (and i think in general). 1. Use a backing bar. 2. Weld it from 1 side, gouge out the root from the other side to clean competent metal, Weld the other side..... Everything else is PJP.

As far as measuring penetration, Ultrasonic Testing is the best NDT approach (unless you have the time/money and suitable geometry for Radiographic Testing) An NDT person who knows their codes will look to the design engineer and the contractor to agree to a procedure for identifying acceptable welds by Ultrasonic Testing because AWSD1.1 doesn't explicitly cover PJPs. There is always Magnetic Particle Testing, but that is really for finding undetected surface and near-surface problems and won't let you figure out penetration like UT does.

RE: Weld symbol

JAE - The way I read that is that we, as the EOR, are designing the connection by showing plate sizes, effective throat for welds, etc.. and by not showing a specific type of PJP or CJP we are communicating to the fabricator by note (a) under 3.1.2 that there are no restrictions on the type of PJP or CJP.

We're not relying on the fabricator to do any connection design or determine the required throat thickness, only to select a PJP or CJP of their preference with no restrictions.

RE: Weld symbol

Lion06, As per D1.1 2.2.5.3 either way is acceptable. At a minimum, the contract documents are required to show PJP or CJP. Anything further is up to you to specify or leave up to the contractor, including weld size (code minimums will apply if you don't specify) and groove type.

RE: Weld symbol

To Nutte’s question, page 6.... Yes I could be confident of getting a .5" effective throat out of that 3/8" v-bevel. It has to do with the welding process and methods that the fab’er. uses to make the weld. One of those processes is sub-arc welding (SAW). Some weld processes penetrate much deeper than others, and the older codes would allow you an extra 1/8 or 3/16" of throat in recognition of this deeper penetration. I used this extra throat often in design, and sectioned plenty of them to know it can be true. I never really pushed my weld stresses to much, unless doing so would save me a weld pass or two. You also wanted good fit-up so you didn’t leave what is almost a crack starter at the base of the root pass, at the land. And, you certainly don’t want tensile stresses across that weld at the root.

That flare bevel is notoriously a difficult weld to do and often an inferior weld. The base of that root often looks like really bad chicken sh.t, with poor penetration into each wall, and no sound bridge btwn. them. The welder is trying to do both, and ends up doing neither very well. We often did that weld in two steps: we used a finer wire or rod for the first pass (or first couple passes), and a quicker freezing process so that you could build that bridge, and get deeper in the groove; then you could switch to a regular welding process to fill the groove. Fit-up btwn. the two HSS’s is another problem as pertains to the groove depth and width, thus the first couple passes can be fairly finicky. Another thing we used to do with a weld like that, and you probably won’t find this in the codes; we would press a small dia. soft wire down into the groove, almost as a backer bar, to start to build that bridge. Then the two step process may not be needed. We had welders who could melt the top 2/3's of that wire into the weld puddle, and leave the back of the wire generally a nice smooth backer. I don’t know the last couple eds. of the codes very well, but 48v’s “5/8R, 3/4R, and 1/2R respectively,” sound about right, depending upon the exact make-up of the joint. JAE’s sketch shows about the same thing as a function of welding positioning and penetration potential. And, I think they take account of the fact that I might not know the welders or the shop doing the welding, and as we are more and more want to do, they codify everything.

RE: Weld symbol

Dhengr, when I look at the AWS tables for prequalified PJP welds, all of them show the effective throat E to be either S or S-1/8" (where S is the groove depth). None of them show E to be greater than S. I'm not saying there isn't some penetration into the base metal below the groove depth. I'm talking about groove depth and effective throat call-outs on the weld symbol.

RE: Weld symbol

Nutte, no prequalified welds have a weld size greater than the depth of preparation, but you could qualify a procedure that did provided you can prove the veld size with the macroetch.

RE: Weld symbol

Nutte:
I don’t doubt what you are saying, I see that same thing in my older Eds. of AWS. I don’t know about the last few Eds. of AWS and AISC well enough to comment on the rationale for all of their changes in design stresses, tabulations and prequalified welds, etc., since I was last doing weld design every day. Most weld processes would limit you to a throat of ‘S’ or less, the groove depth or less. That was std. when I was practicing on a regular basis also. But, it was also common to some industries and codes to allow the use of the actual throat for design, once you proved you consistently achieved that grater throat. So, in practice we could to take advantage of the improved penetration of some weld processes, on some types of joints, and your ref. to Mike’s page 6 would have been one of those, as I remember it. Of course, this was contingent upon good quality welding, good fit-up, attention to detail, etc. I would not allow tension across that weld, at the root.

Finding this was like pulling teeth. I found some discussion on this actual throat vs. effective throat (or theoretical throat) issue, in several older AWS Welding Handbooks, and some Lincoln literature and Handbooks, but was not finding it in AISC or AWS manuals or codes. And then, finally a lead from some Lincoln lit.... in the AISC manuals:
7th Ed., sec. 1.14.7, Effective Areas of Weld Metal, can add .11" to throat size for SAW
8th Ed., sec. 1.14.6.2, do.abv.
9th Ed., ASD, sec. J2.2.a, do.abv.
1st Ed., LRFD, sec. J2.2.a, do.abv.
Don’t know after these Eds. what happened in AISC, and can’t find it in AWS
And, I think AISC was being safe/conservative with the +.11" added throat. I allowed this same design criteria on a groove weld (PJP) as long as I wasn’t dealing with tension across the weld, in which case I would not use the PJP weld. Someone above mentioned a convex top on the weld to increase the throat, but that is not allowed to be considered, at least I never did. I figured my throat to the theoretical surface of the weld and still always wanted the convex finish. Many times, to pick up throat size, I would detail a 1/8 or 3/16" bevel on the web pl. on a built-up girder, and the like. We could nibble or grind these bevels almost as fast as one of the guys could walk down the edge of the pl., that is, fairly min. extra prep. work to pick up that extra 1/8 or 3/16" (plus my .11 to 3/16") for root area penetration. I doubt that most Structural Engineers on bldgs. would go to this trouble, but for the most part we were always doing the design, piece detailing and the fab’ing., and I would actually ask for specific welders for some details, because I knew what they could or would do.

If I were designing today, either bldgs. or bridges, with the job to be let out to anyone who owned a welding machine, and offered a low bid, I’d probably use S - 1/8" too. I suspect the current codes account for a very competitive fab. market, not knowing who’s going to be welding it, fast and min. cost fab’ing., the fact that some grooves are tough to access with some processes, thus inferior root, etc., and this might be left to the fab’er. to determine. However they’ve screwed around with design stresses and the phi, phy, and pho-phum factors, the way welds work and the general engineering concepts involved in weld design really haven’t changed, just because they’ve changed the codes. A new name for an old concept is always a good way to add confusion to the whole process.

48V.... if you are going to use “velds” you have to use ‘machrovetching’ also. smile

RE: Weld symbol

Dhengr, thank you for the feedback. That note you reference, in AISC section J2.2a, was last in the 3rd edition LRFD manual. It is not in the 13th or 14th edition manuals. But, it is for fillet welds, not groove welds. In the current manual, they say that an increase above the diagrammatic effective throat of a fillet weld can be used if consistent penetration can be demonstrated. So it appears it is still allowed for fillet welds, but they're making you hunt for the amount of the increase.

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