Aluminum LTB

[CardsFan1]

I have an aluminum extrusion that is a Tee section with the stem on top and the stem is actually a screw chase.
I am struggling with how to calculate the lateral torsional buckling of the section.
Does anyone have a good suggestion or a reference that does not involve solving a double integral?
It has been a few years since college for me, so my calculus is a little rusty.

 

[jjl317]

Are you using the Aluminum Association ADM? If so, while the don't seem to have an example for a T, they do have one for channel (which I think would address the same buckling issues). ADM 2010, Part VII example 23

 

[CardsFan1]

Yes i am using ADM 2015. I agree that EX 23 applies, but they state that the section has continuous lateral bracing and therefore do not check LTB.
Ex 24 states "LTB must also be checked..."

 

[straub46]

I'm looking at the 2010 ADM, but doesn't F2.1 give an LTB equation for Fb based off section properties, with F2.2.2 applying for r_ye for a singly-symmetric T?

Go Bucks!

 

[jjl317]

Example 28 includes a check for LTB on an open shape

 

[CardsFan1]

I have been studying section F2.1. I am not sure if I can take a tee stem and consider that as ".. if both flanges were the same as the compression flange with the same overall depth." We will work through this and see how it looks. We are also comparing the formulation with that for LTB of tees from the AISC utilizing the appropriate E mod.

Thank you for all of the suggestions. I will let you know what we come up with.

 

[straub46]

There's a note after EQ F.2-8 that gives df for a tee. That should let you calculate j and then the rest of the terms you need to get Me.

Go Bucks!

 

[CardsFan1]

straub46, thanks for bringing to my attention. I read "singly symmetric I shapes.." and moved on to another section.