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Up Topic Welding Industry / Inspection & Qualification / Undercut
- - By SWN1158 (***) Date 09-18-2018 13:10
We have some questionable undercut on a few 3/4 thick base plates on HSS6 x 6 tubes.  D1.1 states that for material less than 1" thick. undercut shall not exceed 1/32 with the following exception: undercut shall not exceed 1/16 for any accumulated length up to 2 in. in any 12".

Since the tube is 6", does this mean the above statement would be a pro rated application, which would limit the 1/16 "undercut shall not exceed 1/16 for any accumulated length up to 1 in. in any 6" ?  

The weld symbol is an all around symbol, but the base plates can't be welded all around in one fatal swoop. The column must be rotated in the shop 3 times to complete the weld, so does this count as four 6 "welds, or one 24" weld, in which the 2 in in any 12" would apply all around (weld length ends up being 24" all around.
Parent - - By jwright650 (*****) Date 09-18-2018 17:24
May want to use Clause 9.25 and the Visual Acceptance Criteria in Table 9.16 (7) The column for Tubular Connections (All Loads) is shaded  and is not applicable. :cool:

As for the length of that weld, I say it's 24". There isn't a rule saying you have to weld it in one 24" swoop or an inch at a time for 24 swoops. Code is silent on the number of starts and stops within a weld regardless of it's length.
Parent - - By SWN1158 (***) Date 09-18-2018 18:19
Thanks John!

So Tubular Connections covers base plates welded to HSS columns, with regard to undercut, and Table 6.1 doesn't? For some reason, I'd always thought 9.16 applied strictly to HSS to HSS

I see that (7) is not applicable, so then, what is applicable? What dictates acceptable / rejectable undercut if Table 9.16 (7) doesn't?

I'm going out to a jobsite after work to discuss with the third party inspector, who insists that the undercut on a few of the base plates are rejectable. From my understanding, his basis for rejection is Table 6.1, which is not applicable if they're nontubular static and cyclic, but again, what criteria in D1.1 is imposed with regard to undercut? It appears that neither of the two tables... 6.1 and 9.16 are applicable, so what is, with regard to undercut?

What am I missing?
Parent - - By jwright650 (*****) Date 09-18-2018 18:44
I usually fall back on Table 6.1 too for Visual Inspections, and like Lawrence says you may want to seek the help of the EOR regarding the loading of the column.

Food for thought
Annex J page 373

Tubular
Tubular connection
Tubular joint
Parent - - By SWN1158 (***) Date 09-18-2018 19:01
Ok. Thanks, but what criteria is used in this case for undercut acceptance?
Parent - - By jwright650 (*****) Date 09-18-2018 19:41
Reading the definitions closer, I'm thinking the "tubular member" that is mentioned here is not the column and then the other "non-tubular member" the baseplate, but the entire column/baseplate is a "member".

Not knowing the loading, I would use the tighter of the tolerances until the loading direction is understood.
Is the 3rd party correct in that there is undercut present?
Parent - - By SWN1158 (***) Date 09-18-2018 19:47
yes, but I'm heading out to see the extent of it.
Parent - - By jwright650 (*****) Date 09-18-2018 20:39
Best wishes,  Scott.
Parent - By SWN1158 (***) Date 09-19-2018 00:59
After my jobsite visit, this guy clearly does not know the code.
Parent - - By Lawrence (*****) Date 09-18-2018 18:11
Hi Scott !

Food for thought:

(B) In primary members, undercut shall be no more than 0.01 in [0.25 mm] deep when
the weld is transverse to tensile stress under any design loading condition. Undercut shall
be no more than 1/32 in [1 mm] deep for all other cases.

While a base plate is typicall in compression... compression may not be the only load that weldment is designed for eh?

You may want to have the engineer define whether the base plate is "primary" and if it is designed for anything other than compression loading, I suspect someplace on that HSS, the weld will be transverse tensile stress.  Which makes the undercut allowance next to nothing.
Parent - By SWN1158 (***) Date 09-18-2018 18:20
Ok. Thank you.
Parent - - By jwright650 (*****) Date 09-18-2018 18:52
I always hated arguing over undercut when a 3rd party was inspecting in my shop so I was always really tough on the guys in regards to undercut. Now I'm on the other side of the fence...ugh, and it doesn't make it any easier to make those tough calls.
Parent - - By 803056 (*****) Date 09-20-2018 10:38
I'm on the road this week and next, so I don't have a copy of 2015 with me, but in a statically loaded structure, which is what most steel frame building are, the undercut allowances are more liberal when compared to the criteria applicable to cyclically loaded structures.

I seem to remember the undercut allowance for cyclically loaded structures to be 0.01-inch when loaded transverse to the undercut. If my recollection is correct, it would hardly seem to apply to this application. Again, if my recollection is correct, the Engineer has to specify when cyclic loading is an issue, i.e., which members are designed for cyclic loading.

The structure has to experience at least 10 000 load cycles where the magnitude of the changing load meets the minimum load requirement before the Engineer has to consider the cyclic provisions of the code. Few structural steel framed building will experience loads that have changing load conditions of the magnitude or number of cycles needed to meet the cyclic requirements. 

Al
Parent - By Lawrence (*****) Date 09-20-2018 12:05 Edited 09-20-2018 20:45
I don't usually cross swords with Al  :)

But the original posting says this is an HSS (hollow structural shape) welded to a base plate.

In my opinion this invokes clause 9 criteria for welding and visual inspection.

Clause 9 table 9.16  could use a little improvement, but I read it in the following way related to undercut:

EVERYTHING visually inspected must be evaluated in accordence with  Table 9.16  7 (B)

Cyclic loading does not play a part in this weldment.  Only the possibility of DESIGN for transverse loading.
- - By welderbrent (*****) Date 09-20-2018 18:46
It is highly unlikely that a member with a base plate is going to classify as 'cyclic'.  Even then, must be so designated by the engineer.

It would be interesting to see such a member under tensile loading AT the weld.  Then to have a weld transverse to that load so that the ultra extreme undercut criteria applied.  Compression is most usually the condition. 

If Table 6.1 is being applied for materials under 1", the response for application is that the entire length of weld can have undercut up to 1/32".  Undercut can be 1/32 to 1/16" for 2 in 12".  Length is not a consideration if it is in excess of 1/16th ", it is just rejectable. 

Since your weld was called out as 'all around', I would call it a 24" weld.  If it had been shown as a fillet on four sides, it would be 4- 5" welds.  The corners do not need to be welded.  That's another story and usually argued.

But, to classify under Clause 9 or Clause 6.  That sounds like your first battlefield.
Parent - - By 803056 (*****) Date 09-22-2018 14:19
I have to concede to Lawrence on this one with the provision the contract references the latest edition of the Farm Code. However, I would refer this to the Engineer for clarification and possible exemption from the requirements of clause 9 if the 2015 edition is referenced by the project specification, drawing, or local building code.

If the loading on the column are in compression, i.e., no moment loads (by design), holding the contractor to the 0.01-inch maximum undercut seems a little over the top.

If one reads the entirety of clause 9 and the commentary it will be noted that the basis of clause 9 is based on research on tubular connections used by the off-shore oil industry. Most people will recognize the types of loads off-shore platforms experience can be severe and the size of the members are large and the thick walls are much thicker than most HSS used in commercial one- and two-story buildings. I would further venture to say few commercial structures built in the US using HSS members are designed or fabricated to the requirements of clause 9.

I would further venture to say the National Building Code has not yet adopted the 2015 edition of the Farm Code. Brent and Lawrence can probably give us an update in regards to which edition of the structural welding code is currently referenced by the building code. That being the case, the visual inspector should be using the code editions cited by the relevant building code or the one referenced by the contract. The inspector should not arbitrarily use the latest edition of the structural welding code.

Best regards - Al
Parent - - By Lawrence (*****) Date 09-22-2018 19:41 Edited 09-22-2018 19:43
Strangely enough the IBC does not directly specify welding standards.   However it does specify AISC 360 which does indeed Specify AWS D1.1 and furthermore it AISC specifies the latest edition (2015)

That being said, not everybody is living under IBC or AISC governance, or they may live under local or state jurisdictions that specifically call out for various vintages of AISC 360...   So as Al suggested, there may be loopholes that are absolutely within both the letter and spirit of the law.

Or you could just make welds without undercut.

Would appreciate Brent's take on this,,,, because he gets out into a more diverse compliance environment than I do.
Attachment: AISC.pdf (148k)
Parent - By 803056 (*****) Date 09-22-2018 21:31
Or make a weld without undercut. I like that.

Al
- - By SWN1158 (***) Date 09-24-2018 12:40 Edited 09-24-2018 15:29
The undercut in all cases is in the base plate, which I would consider to be a secondary member, with the HSS column shaft being the primary member. In no case does the undercut exceed 1/32. Moving forward, our stance will be to allow zero undercut, which will resolve any future debate about undercut. Thank you all for taking time from your busy schedules to help me with this.
Parent - - By bb29510 Date 09-25-2018 04:12
one of the biggest problems with undercut is how are you going to repair it, you cant get enough heat into the metal to create a good fusion, you almost have to start from scratch and take the whole weld out. so since its so hard to repair, if you have a minor undercut, do you call it a failure?
Parent - By SWN1158 (***) Date 09-25-2018 14:52
If it doesn't meet code criteria for undercut, it's rejected. I've seen a lot of undercut repaired with a grinder, but you have to be careful not to remove too much base metal.
Up Topic Welding Industry / Inspection & Qualification / Undercut

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