Weld symbol 5

[WARose]

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?

 

[msquared48]

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

Mike McCann, PE, SE (WA)

 

[48v]

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.

 

[WARose]

Thanks guys!

 

[KootK]

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.

 

[BUGGAR]

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.

 

[KootK]

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.

 

[Lion06]

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.

 

[48v]

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.

 

[JAE]

See the attached image - this is from AISC's Hollow Structural Sections Connection Manual.
They reference AISC Specification Table J2.2 for the size of the effective throat.



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[WARose]

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.

 

[KootK]

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.

 

[msquared48]

http://www.metalwebnews.com/howto/weld-symbols/weld-symbols.pdf

Mike McCann, PE, SE (WA)

 

[48v]

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.

 

[nutte]

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?

 

[Lion06]

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.

 

[WARose]

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?

 

[JAE]

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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[msquared48]

https://www.google.com/search?q=Sta...v&sa=X&ei=1zb_VJSfIdivoQToj4HQAg&ved=0CC0QsAQ

Mike McCann, PE, SE (WA)

 

[darthsoilsguy2]

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.