Best CJP weld choice for 5/8" wall HSS baseplate weld?

[engjg]

Best CJP weld choice for 5/8" wall HSS baseplate weld?

 

[jayrod12]

Let's start with an obvious question. Does it really need to be a CJP weld? What loads, dimensions, etc. are we dealing with.

 

[engjg]

Strike the 5/8" wall. Lets say HSS5x5x1/2 with a 150 kip tension load (lrfd) baseplate probably 1.25" A36. Heavy fillet would work but this is critical weld and I expect will see corrosion over lifetime. I want it to be reliable.

 

[dauwerda]

I would start with clause 9 of AWS D1.1.
Keep in mind that most fabrication shops will not have anyone qualified to complete a CJP weld without backing.

 

[KootK]

Maybe partial penetration with some fillet weld reinforcing if you feel that's necessary.

 

[engjg]

Thanks all.

dauwerda - I don't have a current copy of AWS D1.1, only referencing excerpts in AISC 360-16, is there something I should be aware in clause 9?

KootK - The reinforcing fillet is just to reduce stress concentrations right? and doesn't count toward PJP capacity? Whats that combined callout look like?

 

[dhengr]

Engjg:
Of course, we like all welds to be reliable, in my office. Do CJP welds corrode differently than fillet welds in your area? Any weld which is good for 7.5 k/”, (150k)/(4 x 5”), should work. A 7/16th or ½” fillet should probably work, but those are three or four pass welds. You could grind or nibble a .25” x 45 groove around the outside of the end of the 5x5 tube and then add a .25” fillet reinforcement. That should give you about a 3/8th in. throat, and a length somewhat greater than 20”.

 

[engjg]

"Of course, we like all welds to be reliable, in my office. Do CJP welds corrode differently than fillet welds in your area?" good point... I think I will stay with a multi pass fillet, it will be in the shop. I guess I was questioning if there is any disadvantage of a heavy fillet in this case apart from requiring multiple passes?

 

[hokie66]

If I want to develop the whole capacity of the tube, I require backing bars and a complete penetration weld. Someone said welders are rare who can achieve complete penetration without backing bars, so why attempt that type weld?

 

[dauwerda]

I agree hokie66. in re-reading my previous post I see that I was pretty unclear. I was trying to caution against specifying a full pen weld without backing but failed to mention the preferred way would be to use backing.

engjg, I mentioned clause 9 because it is written specifically for tube members. In typical situations when backing bar is left in place it must also be fillet welded to the base metal to prevent stress risers. With an HSS5x5 I am guessing that there is no access to the inside of the tube to complete this weld. Luckily, clause 9 address this and says it is acceptable to leave the backer in place without this weld and it is still a pre-qualified weld joint.

I agree with others that a partial penetration weld with fillet overlay may be a better option. The one caveat to this would be if your connection will be subject to fatigue issues, as it has been shown that full pen welds have a much better fatigue life than partial pen or fillet welds.

Fillet overlays are also useful to help reduce through-thickness stress on the base plate which can lead to lamellar tearing.

 

[Ron]

Single bevel with 1/8" land and backing bars. Will this be a shop weld or field weld?
Specify NDT (ultrasonic)

 

[JLNJ]

CJP with backer, but your tube will have a much higher yield strength than your A36 base plate.

150 kips direct tension on such a small member? I imagine your base plate and/or anchor rods will by far be your weak link(s).

 

[CANPRO]

A CJP is not an ideal detail for high tension perpendicular to a thick plate - you run the risk lamellar tearing.

I’d probably opt for a partial pen weld with a reinforcing fillet.

Is this a column or a some sort of hanger? What does the baseplate look like? Is it tension only?

 

[hokie66]

CANPRO,

I doubt lamellar tearing is ever an issue in a 1.25" plate. In thick plates, yes.

 

[BUGGAR]

Another way just because:
I'm working with a pole fabricator for a utility contractor and he is having 1 inch thick base plates with holes cut in them to fit the poles (automated plasma cutting or something). The poles (round HSS) fit into the holes with a fillet weld top and bottom all around. The holes are cut accurate enough that no further fitting is required.
The utility likes these because they are open at the bottom and don't collect water. These are those baseplates with the drain notches cut in the corners.

 

[Ron]

Buggar...insertion allows moment transfer without all of that capacity going through the weld....good way to do it but a bit more difficult with rectangular sections.