Aluminum Design 2

[Whoopdedo_LSU]

I'm designing aluminum tubes and am wondering about checking lateral torsional buckling. Steel doesn't require you to check this for tube shapes but ADM (2015) doesn't state you can neglect it. I don't think this will ever be the controlling failure mode but the equations don't work out that way. Anyone have any thoughts?

 

[BigInch]

You don't check that because it is a tube, not because the tube is made from a particular material. Tubes have the same radius of gyration in all directions, therefore you can only check axial buckling.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[KootK]

What are the width and height of the tubes? I'd have thought that LTB would be a none issue as well unless the cross section aspect ratio is relatively high (>2).

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Whoopdedo_LSU]

I have a 2x2x1/4 tube 60" long cantilever. Using welded properties per ADM 2015 with yield and buckling constants

 

[Whoopdedo_LSU]

BigInch- Per ADM, all sections have to be checked and you cant cherry pick them out based on AISC design specs. We all know this will not control for a square tube but the check still needs to be documented.

 

[KootK]

In my opinion, an engineer can opt not to check anything that their professional judgement tells them will be abundantly adequate. ADM's not the boss of how SE's get their SE on. Alternately, if you'll design more than five of these, spreadsheet it and have you computer do the BS checks.

I hardly ever check steel beam shear. Heck, my old boss would do entire truck stop restroom buildings "by inspection".

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Also, in your case Ix = Iy. That makes lateral torsional buckling a physical impossibility. A bit like checking to see if some water might decide to flow uphill.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Whoopdedo_LSU]

Agreed. I just have to add language as to why I'm not checking it. This is being reviewed by an outside source and trying to make everything as clear as possible so I don't have to revise later on.

Thanks for the input.

 

[Ron]

Agree with KootK.....engineering judgment is always to be employed! Whoopdedo also brings up a legal issue....as an engineer, you must CONSIDER it, even if you think it is not relevant. Just document that you considered it and determined it to be non-relevant.....that keeps you out of the "negligence" realm of state law.

 

[BigInch]

KootK Thanks! I couldn't have said it better myself.

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[KootK]

You're welcome BigInch. As a former holder of several TN-1 visa, I dig your signature.

As far as documenting your calcs goes, mine would say this: Ix = Iy Therefore LTB ok. If the reviewer doesn't get it, they've no business doing the review.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BigInch]

I've done my share of visa apps. I've worked long term (at least one year) in 8 countries and lived in still a few more.

Technology is stealing American jobs. Stop H1-Bs for robots.