Welding Edge Distance on Base Plates / Coumns - HSS to BP 3

[JackRob]

Hi all,

I have a 5x5 HSS column which the 5.5" wide x 9" Long base plate. This is due to design constraints.

So on 3 sides of the column, I have 1/4" of edge distance from column wall to base-plate edge. In order to get a 1/4" fillet around the column, AISC requires 1/4" of shelf dimension next to the 1/4" fillet weld, so a 6" wide base plate would work. They cannot adjust plate width.

The loads aren't particularly high, but I do need a weld on 4 sides. Has anyone come across this issue before, or have a creative welding solution?

Thanks!

 

[dauwerda]

Use a PJP weld instead of a fillet weld.

 

[JLNJ]

Or a 3/16" fillet, depending on the base plate thickness.

Or don't weld it at all on those sides.

 

[Agent666]

One sided fillet welds are a fairly terrible detail, reason being the root of the weld is a great crack initiator. Protect the root I was always taught!

 

[dold]

PJP as dauwerda says. I dont know why everyone at my office poo-poos PJPs or CJPs for a couple, one-off baseplate or miscellaneous connections. Good grief, hit the tube with a grinder for 10 seconds and weld it to the plate. PJP, done. That literally takes, what, 10 seconds longer than a fillet weld. Unless this baseplate with 2 anchors is experiencing tremendous uplift I've never understood the consternation about PJP. CJP, sure, backerplates and all that are a pain. But deal with it. You gotta have your 5.5" baseplate, you gotta have a proper weld. You can even butt weld it on the flush side if you have like 1000 of these things and the PJP is absolutely not acceptable. Nobody is stopping you from even welding it only on the two longer legs of the plate. Not ideal... sure. But depending on the application you can be flexible with something like this. We use flush baseplates on lightly loaded HSS all the time. Detailers have never had a problem giving us a PJP on the front and back. I.e., 4x4 tube and a PL 1/2x4x10 baseplate. Tack the plate to the tube, zip the edges and weld it. Done.

Someone please correct me if I'm wrong.

 

[dhengr]

JackRob:
There should be no problem with PJP welds as long as they are done properly. Their primary drawback is that they require a bit more prep. work as compared to a simple fillet weld. Their root needs the same protection as the fillet root does, that is a weak spot of both welds, as mentioned by Agent666. The CJP weld in a detail like this is no simple matter either, given the need for back-up bars, at very difficult corners and corner prep., and lack of access to the back of the welds. I thought that AWS req’rd. an 1/8” beyond the toe of a weld to the edge of a pl., so as not the burn off the corner of the pl. and allow a full weld leg. What is the rationale for a full 1/4” of pl. surface? Of course, the size of the PJP depends on the wall thickness of the col. tube, less an 1/8” land, plus a reinforcing fillet, but that will gain you some amount of weld size.

 

[JackRob]

Thanks for the feedback everyone.

I always get designers that want to keep the base-plate narrow for "look" and I always get welders that don't want to do the PJP or CJP welds (I hear the same as you dold).

I agree that the PJP and CJP is the best solution, but only if done properly as mentioned by dhengr. Though on certain smaller projects where budgets are tight, I also prefer fillet welds in these situations, mostly because I can't always trust the welder to do the CJP or PJP properly.

With regards to the code, I am actually not sure on the reasoning for the additional 1/4" shelf, I can make some assumptions but I am going to do a little research on that. It comes from "AISC specification section J2.2b" and "Figure 8-11 in the 14th edition Steel Construction Manual'.

 

[dhengr]

JackRob:
You are not responsible for the welders not knowing how to do their job correctly, or when they do a poor job. They shouldn’t be doing the work if they can’t follow plans and don’t know the various codes, etc. You didn’t hire them, the owner or his G.C. did, and as usual for the lowest dollars, and with little regard for quality workmanship and knowledge of their job. It’s min. dollars per ton of steel deal, and all else must then be o.k. You didn’t insist on that min. width base pl., without any regard for how it could possibly be fabed., they did, so tell em to quit bitchen when that weld is a little more expensive to comply with their wishes and still make it work. Today, it seems that many of our clients should do their own structural engineering, that way they can waste their own time cleaning up the messes they have dictated for dumb reasons. And, any extra costs or inconveniences caused by their stupidity falls back on the party who caused the problem.

My understanding of the min. 1/8” edge dist. beyond the toe of the weld was…, is that you can’t weld right up to the pl. edge without melting the edge and having it slough off, in which case you probably end up with a weld leg which is actually an 1/8” smaller than you intended. In which case, that leg size could be approaching the throat you actually expected to get. I don’t know of an actual stress reason for that reqr’mt., it’s just a practical welding need.

 

[Ron]

@dhengr....well said! Agree completely.

 

[dhengr]

Ron:
Thanks. And, congrats on being a 20-year member of E-Tips. That’s a lot of good advice dispensed, and hopefully some smarter engineers for having received it.

 

[Deadblow]

I must be missing something. It appears to me that Figure 8-11 contradicts section J2.2b of the AISC 14th edition. Section J2.2b.(b) would lead me to believe the distance between the edge of the base metal and toe of the weld is permitted to be less than 1/16" provided the weld size is clearly verifiable. That statement seems to agree with the images shown on Table 8-2 for prequalified fillet welds. But that is not in agreement with Figure 8-11. Could someone clarify for me?

EIT

 

[Hokie93]

AISC 360-10 (and 360-16) J2.2b refer to fillet welds made along the thickness of an element. In this case, the OP is referring to welds made along the face of an HSS. So Figure 8-11 does not contradict the Specification.