Bending of a Rectangular Hollow Section

This is not clear. Does "RHS" equal "rolled hollow shape"? They can be bent about the minor axis.

A diagram would help.

Rectangular hollow section. RHS.

Bazzer

Bending steel shapes is not a big deal.

Do you simply need some of these rings made? A steel fabricator will have proper equipment and skilled workers to accomplish this, they do it every day.

Have you ever tried to pick up an 8"x4" Hollow square section, let alone one with a wall thickness like this,(which I find quite over the top), I can't see any way you'd bend it in a full circle without heating it, If it were me, I'd fabricate it from flat sheet.

Bazzer

Agree, at over 900 pounds these rings are much too large to manhandle.

My comment in #2, "A steel fabricator will have proper equipment and skilled workers to accomplish this, they do it every day." is still valid. If heat is indicated they will take care of it as a matter of course.

I'm not saying that it can't be rolled, but that at 3m dia the compression to the inside dia, and the tension on the outside dia will cause so much trauma as to damage the integrity of the structure, also if you imagine the side wall at 8" high, the top will be stretched whilst the bottom will be compressed, as I've said fabrication is the way to go.

This said I would like to know the outcome of the project.

Bazzer.

It is unfortunate that our young friend Ken is not usually a fountain of information regarding his projects. I would also like to hear more about it, but I am doubting that we will learn more.

For all we know, the tube is to be final shaped with the the 4" faces making the inside/outside of the ring... that wouldn't surprise me too much; Ken has some unique requests here at CR4.

http://www.atlastube.com/images/stories/pdf/Compression_Members/CIDECT%202V-2_01%20Final.pdf

These rings... are they like hoops around a barrel, the barrel staves made of wood or steel, and this assembly will make your three meter dia column?

Are these bends to 1.5 M radius? If so, I'd think that the bend would be possible, given the right bending machine. (It requires an impressively large machine to bend 4" x 8" tube with .400 wall.) And no, at that radius-to-tube-section-ratio, I would not expect strength to be adversely affected. But depending of safety concerns, you'd want to test a section after forming.

The fabricator might want to fill the inside of the rectangular tube with a eutectic alloy or maybe packed sand to support the inside diameter wall against buckling. But your OD to thickness ratio is pretty small, so maybe OK.

Hi Youngken - this is OldKen (sorry, couldn't resist)

Since you are forming this section the "easy way", as we call it here in USA, and the wall thickness is over 3/8" (.375), I expect you will find a tube forming shop that could easily do that. Due to the size of the tube, the shop will be of the larger size with dies to support the 8" to prevent it from collapsing, should that be a concern to him.

Worse-case scenario, if pressure required to push the tube is greater than the metal can withstand - you may wind up having it induction formed. Again, this will be done at a specialized shop that is all set up for it.

Ken Hollingsworth

Pascagoula

As far as I know, RHS can be classified as Hot Rolled & Cold Form.

Any difference for them for the bending process and strength deterioation after bending?

Just re-read your post above, and I find nowhere that you tell us what grade of metal, or to what specification the tube is produced. Not knowing what your column is used for, you should really have this project engineered. The engineer will give you the grade of tubing, and type of metal. For instance, if your column is susceptible to a damp environment, you may be required to use Stainless Steel.

As for the terminology, I think you are confusing two different things. Hot Rolled is typically used as a term to describe the method of producing the metal at the mill. Cold Rolled is another refinement that tightens tolerances on dimensions, and has it's own grading system. I do not think you will find the tubing in Cold Rolled. Cold forming is yet another term which indicates that the tubing was formed without heat.

As far as deterioration of properties (tensile & yield), this will depend on the grade you start with, and how they have to roll it. If heat has to be applied to make it more pliable, then you should expect to have it Stress Relieved, if not re-heat treated, depending on the grade you start with. As I said - you really need to have this engineered. I am not an engineer, but have worked over 40 years in a fabshop environment, and have fought all of these battles. For instance, the engineer may determine that, since your column is in a wet environment, and should be made of Stainless Steel (he will tell you the grade to use), and since that section of Tubing isn't produced in Stainless Steel, you may wind up using Channels formed and welded toe > toe.

Will this two piece set be welded after installation to form a circle? PWHT (post weld heat treat) could be required to reduce any stresses induced with the welding.

Get an engineer and save yourself a bundle of money and heartaches. Then take his specs and dwgs to a good Fab Shop who will know all of this, and where to have the specialized work jobbed out. So, how tall is this column, and how many of these tubes will you have to come up with?

Ken Hollingsworth

Pascagoula