Welding between a thick solid rod to tubular hollow section

[LJ_]

Hello!
say you have a 6 in solid Section can you have it be welded to a 6 in tubular section With 0.25 in thickness. And Do you think if we have this 6 ft beam that is half solid rod and half tubular section, there is compatibility in deformations? I am having real trouble with this connection.


Edit: typo

 

[GregLocock]

Unfeas in a construction environment, as the solid bar will act as a heat sink and you'll have no control over the weld quality. Not that I believe a 6" diameter rod in that field either. What's your actual problem?

Cheers

Greg Locock


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[sdz]

I have a similar, but not as extreme problem welding a 20mm dia bar to a 1.6mm wall SHS for a ladder. AS4100 says 20mm thick requires a minimum 6mm fillet but I'm concerned trying to do that in a single pass would burn through the SHS.

 

[1503-44]

You must preheat to try and control heat sink effects. And carefully control its cooling to prevent weld cracks.

You can't really make a valid weld thicker than the thinnest wall being joined. Greater thickness is useless anyway.

Expect stress concentrations at such types of joints.

 

[LJ_]

Hello @GregLocock

That’s the actual problem. These rods were specified as part of a truss by an engineering firm and then some changes were required by the construction side and the drawings came to me. So I analyzed the structure and recommended against them and not to use them. Because I didn’t see why they needed them and also the welding issues and deformation in the boundary.

Is there any design guide or code where welding to elements this thick is warned ? I tried looking into the AISC design guide 21 but didn’t find anything.

 

[rb1957]

what sort of truss uses 6" dia solid bar ?

Could you shrink fit a tube over the solid bar ?

another day in paradise, or is paradise one day closer ?

 

[r13]

How about making a sucked socket connection by machining the end of the solid rod down to 5-1/2", then mate weld the two parts.

 

[1503-44]

Why not internally bore the end of the rod, such that it leaves a lip of the same width as the tube wall where they will be joined. Basically then you have to weld just a normal pipe joint which you can do with a full penetration "V" weld all around. To reduce stress concentrations in the solid rod's side of the bore, taper bore that to get a smoother wall thickness transition, which will be far more favorable in avoiding stress concentrations.

 

[LJ_]

This is interesting. However, this is a truss and while this could work for an horizontal element it also receives vertical and diagonal elements. I am inclined to the boring of a transition thickness. I think it would be expensive right.

 

[rb1957]

yes, machine the OD down (for the tube) and bore the bar (to leave a nice 1/2" flange and transition into the bar.

another day in paradise, or is paradise one day closer ?

 

[LJ_]

I don’t know what loads have to do with this? This is a theoretical problem concerning feasibility during construction. But the question is clear, sorry you can’t see it.

 

[BAretired]

Maybe you should stick to your guns and tell them the 6" dia. rod has to go.

BA

 

[LJ_]

Yes I already did that. Because it wasn’t needed in any way. I was just wondering if It could actually be feasible.

 

[GregLocock]

with tapped holes on the small centreline



Cheers

Greg Locock


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