Plug weld or fillet weld in holes

By swsweld (****)

Date 06-22-2009 04:01

I'm inquiring as the contractor that will be performing the welds if the engineer approves the modification. I understand that the EOR bears the brunt of responsibility for this decision but I want to cover my bases as the welding contractor.
This is on a multi story cold formed metal building, no large beams of columns as with traditional multi story buildings. The only structural members are 4" H columns that go from floor to floor. The EOR is calculating the option for us (sub contractor) to make a fillet weld inside the bolt holes on the splice plate to the column web above each floor. The columns were pre drilled at the top but not at the bottom so the field drilling is very difficult. They will be bolted below the floor and welded above the floor. I will try to post pics for clarification. The holes are 13/16" dia. and the thickness of the splice plates vary from 1/2" to 3/4". I think that it will be difficult to make sound fillets in holes that small. Access and visibility will be an issue. D1.1 plug weld qual test is on 3/4" holes so I know it is legal. Groove weld qualification covers plug and slot welds. AISC (I don't know if this building is under this code, sorry) states fillet welds in holes or slots are permitted to be used to transmit shear in lap joints or to prevent buckling...16.1-97,98
The dia. of the holes to be plugged shall not be less than the thickness of the part containing it plus 5/16".... So I think we would be legal for the 1/2"thk plug weld but not the 5/8"thk splice plates. I would prefer the plug weld but they are looking at a fillet weld inside the holes. I'm not confident in this building construction method as this is the first one that I have been on. (They have gone to this style for speed of completion) We get hurricane force winds and I don't want the building to fall because of a design or quality issue or anything else for that matter. I know that they will not specify NDE other than visual from a TPI.
I guess my question is would you prefer a fillet weld in the bolt holes or a plug weld in this case. Also, sometimes it looks good on paper but can't achieve the desired results in the field. I am proposing to weld a few to gage the quality of our welds before agreeing to do the remainder of the building. The ONLY other structural member holding the building together is metal studs (like for sheet rock) shot down to the floor, and lots of screws.

By swnorris (****)

Date 06-22-2009 19:39

Fairly thick splice plates considering the columns are 4" H columns. Assuming they're W4 x 13, the flange is only 3/8" thick and the web is only 1/4" thick. Some pictures would probably answer half a dozen questions I have.

By swsweld (****)

Date 06-23-2009 01:21 Edited 06-23-2009 01:46

Today the EOR approved the fillet welds in the bolt holes. I was wrong on the max. thickness of the splice plates. The bottom two floors are 1/2" thk plates the top two floors are 3/8" thk plates. I tried to upload pics late last night but gave up. I will try again tonight. I welded one column today and feel pretty good with the fusion at the root. But because the holes are so small (13/16") slag removal is brutal. Too small for wire brush (cup) on a die grinder, burr bit or rock may work but, again, limited access in many locations. Needle gun might work as well but haven't tried it yet.

The supt. confirmed my concerns that in this type of building the red iron (4" H columns) ARE the structure. So it is crucial that this is done right. I still think plug welding would be stronger and slag removal may be easier. Could be wrong on that one. It's been 20 years since I made plug welds ...that mattered. I may try plug welds on one column tomorrow to determine the better method. I think the EOR will approve both methods if the calculations are good. There is a lot of engineering that comes with this type building to compensate for the lack of large steel beams and columns. Even so, I'm still leery of this type building. But what do I know?

By swnorris (****)

Date 06-23-2009 10:44

Tim,

If drilling isn't possible, I'd trust burnt holes in the column web and then bolted rather than plugged holes. Even with burnt holes, it seems that the connection would be stronger with bolts in the holes rather than weld metal in the holes. That would also be faster than welding. Has it been considered? I was going to suggest welding the splice plate to the column, but it looks like you'd be unable to get the proper angle.

By swsweld (****)

Date 06-23-2009 18:22 Edited 06-23-2009 18:29

Thanks for the suggestion Scott. I have not suggested burnt holes but I did ask about welding the top of the plate for extra strength. I don't think it would be a stress riser in that location??? It is a stress riser for me to only fillet weld the holes. Some are very difficult to weld, some aren't. I told the supt. to relay that to the EOR because he possibly hasn't factored the degree of difficulty into the minimum weld detail. Per AISC I am not sure if it if legitimate to replace the bolts with fillets?? I guess it is if the EOR says it is though. The top pic is a little deceiving as it looks like plenty of room for a vertical fillet but there is not enough room for the weld. As you can see from the exterior of the building there will be a large area for wind shear. Perhaps I'm over reacting but this type building seems weak and it has NO structural steel except what is in the picture. We were called in to repair a MESS left by another company and because we faired pretty well they want us to weld the holes because drilling is taking so long and bad angles result in possible wrist/hand injuries. On the plus side, the contractors current on site management all seem competent and professional.I don't know the full timeline on this project but the original contractor was kicked off the project; look at these pics and you will see why.

By swsweld (****)

Date 06-23-2009 18:36

This is looking down on the embed plate; the flat, vertical and horizontal on both sides are to get 1/4" fillet. Many are impossible to see without a mirror or "at least a good try at it". Not a great design to incorporate very difficult welds IMO. Here is my repair. Certainly not a thing of beauty but better that the original.

By swnorris (****)

Date 06-23-2009 18:46

I'm no engineer, but I seriously doubt that weld metal in bolt holes will replace bolt values, especially for the stresses that these columns are going to be subjected to. I have never heard of this as a method of correction. I would definitely stress the degree of difficulty to the EOR. If the EOR approved plug welds, keep a copy of the documented approval, which should be signed by the EOR. Also, document your concerns, referencing specific D1.1 plug weld limitations and specific AISC design criteria, and make sure you've addressed your concerns with regard to the difficulty in acheiving the required welds. If you can, email it to the supt. and/or the EOR, and ask for a delivery confirmation. This documentation will be critical down the road, should a failure occur.

By swsweld (****)

Date 06-23-2009 19:42

Thanks Scott, I appreciate and respect your input. I'm not trying to be a drama queen, uh king, here but this doesn't sit well with me. My gut feeling says this is not sufficient but the EOR has done calculations stating otherwise (he does math with horseshoe looking figures). I will follow your advice on the email and confirmation. I will email the PM as I have more than verbally expressed my concerns with the site guys. Nice looking weld, huh?

By 803056

Date 06-24-2009 13:20

They look like typical welds found on many PEMB from my vantage point. I'm surprised anyone rejected them.

I hope you know I'm being sarcastic. It's good to know someone is out there keeping the best interest of the public in mind.

You are right in questioning the solutions of the EOR. He is not on the job site and would be wise to ask for the welder's input. What often looks good on paper is difficult at best to achieve on the job site.

You could offer your suggestions as alternates to his based on "ease of welding". The EOR is primarily interested in obtaining sufficient strength to transmit the loads from the column to the foundation by whatever routes are available. Your interest is in providing him with welds that can be easily made while accommodating those loads.

I tend to agree with you that in consideration of the welding position, plug welds made by depositing metal using a weave technique from the bottom of the hole toward the top of the hole would be easier that trying to deposit a fillet weld on the inside corner progressing from the bottom upward.

To validate your approach and to demonstrate to the EOR that you've "done your homework", I suggest you weld a couple of mock-ups and section them to demonstrate you get the same or better results using your technique. The EOR should be satisfied if you can demonstrate you are obtaining complete fusion to the root of the joint and the weld size is as large as required by the design.

As for burning the bolt holes, I would advise against it. The design is most likely based on the bolts being in bearing, i.e., the body of the bolts are in direct contact with the ID of the bolt holes. This is difficult enough with drilled holes and nearly impossible with torch cut holes. There is no access to remove any dross, and there will be some, from between the splice plate and the column web. The dross will keep the splice plate from bearing directly against the column web.

Any solutions would have to be reviewed and approved by the EOR in writing and accompanied by a sketch. You can easily provide him with a sketch of your proposed "fix" and he would simply stamp it as "approved for construction" or "approved for fabrication". I doubt he would object to your proposal especially if it is backed up with sectioned samples.

Best regards - Al

By swsweld (****)

Date 06-29-2009 03:05

I emailed the PM that contracted us to repair the whole bottom floor as he is my highest contact with the company and gave a very respectful and detailed account of my concerns along with yours and Scotts suggestions and much to my dismay; no response. I have been on a different job for a few days but hope to see the PM one day this week in person as he frequents the job every week or two. I hope the PM has conversed with the EOR on this matter because the PM is also responsible for the end product.

Concerning the welds, I use that word loosly, after spending most of my career in the nuclear industry is still amazes me what sometimes passes in commercial buildings.