Compression capacity of Bundled round tube Column and its connections 2

[vhengr]

Any one has literature or information on design of structural members made out of group of pipes?... i.e. bundled pipe column and beams.
How they behave under compression or bending?
How will be the connection look like between two different bundled beam and column?
Anyone has any idea or experience pls share your thoughts.

Case is; I want to replace bigger dia pipe column & beams by bundled-Column made from small dia pipes.



Cheers! -VH

 

[JStephen]

Sounds like an odd endeavor to me. The kind where you use $1,000 worth of analysis to save $500 worth of materials.

If the small tubes are welded or otherwise attached to each other for their full length, you could design them like a single member, using the radius of gyration of the whole group. Beware of weld distortion if you go this route.
If they're not attached to each other for their full length, then you design each one like it was a separate column.
If they are clamped or banded at intervals, you'd be somewhere in between those two extremes, but there may not be information available to properly design them without being overly conservative.
At the ends, if you can mill the whole assembly or weld each tube as it's being built up, you can get a reasonable compressive connection. Otherwise, it seems you'd always have a few tubes carrying the load and some others not doing anything.
You put holes in a flat plate to fillet-weld the inside of each tube to the plate...which may or may not be doable, depending on the plate thickness and the tube size.
Consider any coating or corrosion issues as well.

 

[CANPRO]

I’m having a hard time picturing a scenario where this would make sense or be economical. What are your reasons for wanting to do this?

 

[KootK]

These are just some ideas and should not to be considered a complete treatment.

 

[vhengr]

Thanks JStephen3 & KootK for your valued comments!

My fabricator having a good stock of 40NB Pipe Material; which make us to think of utilizing those material somewhere else for a relatively unimportant Temporary Hoarding type Structure. Horizontal loads mainly wind are supported by the structure as a whole.

So planning to replace bigger dia pipe column (say Dia 300 mm) by bundle of (approx 16-24 Nos ) small Pipe dia 40 mm.
Worry is how to make them behave like a single member and how to weld them together on a base plate.
Providing bolted splice joint on a member is another intriguing task which requires some more R&D work.

Your advice, comments or suggestions shall be appreciated and welcomed!

Cheers! -VH

 

[structSU10]

It might be better to make space trusses out of those members to serve the intended purpose.

 

[vhengr]

structSU10: Yes, initial plan was like that. But fabricator find it more comfortable doing with bundled option.

Cheers! -VH

 

[MotorCity]

How will it be loaded? If you are placing a load on top of the pipes (axially), it will probably sustain a higher load than if you load it via shear tab welded to one of the pipe walls.

If the wall thickness is on the thin side, this arrangement may not work considering the welds between the pipes.

 

[KootK]

Worry is how to make them behave like a single member and how to weld them together on a base plate.

Make them behave like a single member by stitch welding them together as we've been discussing. For the base plate, weld what you've got access to weld and leave it at that.

dia pipe column (say Dia 300 mm) by bundle of (approx 16-24 Nos ) small Pipe dia 40 mm.

I think that you should simply abandon this idea altogether. 16 pipes 1.5" in diameter as a single member? You'd have to build it up from the inside out. Your client wants what they want, I guess, but I struggle to imagine how this could possibly be a practical solution.