Flexural Capacity of unique section

[AnimusVox]

Hello everyone,

I'm trying to determine the flexural capacity of the following sections, and I'm not sure how to approach them. I'll attach their cross sectional properties and dimensions, here's some information about them:

-They would all span 10'-0"
-Plates are made of A36, Pipe Fy=35 ksi (I just assumed Fy for the whole section to be 35 ksi to simplify matters)
-All elements (flange, web, pipe) are compact

I'm trying to determine Lp, Lr, Mp, and Mr to find the flexural capacity from LTB. I'm not asking anyone to crunch numbers, just for a method of approach. None of my coworkers can really make heads or tails of it, I'm an intern this summer so any insight would be greatly appreciated!

edit*: When I preview this post the image doesn't appear when I try to open it. In case the link is broken, here's a description of the cross section: It's a Tee-shape (made from two bars) and the bottom of the web is welded to a pipe, bending occurs about the strong axis.

 

[Lomarandil]

No luck on the attachment, unfortunately.

I agree with calling it all 35ksi. You probably don't want to design anything close enough to the limit that 35ksi vs 36ksi matters.

I'd consider it similar enough to an I-shaped member that AISC section F4 (and by extension, F2) would apply. So L_p isn't tough, just requires r_y, which you should be able to figure by mechanics. I don't know how beefy your section is, if you're lucky this results in L_p close to 10' so that you don't have to worry about L_r.

If you do need L_r, I'd use r_ts based on the compression flange + 1/6 web (see the user note), and J conservatively based on the summation of the individual parts.

I'm drawing a blank on "c" though... anyone able to shed some light on that?

 

[AnimusVox]

I managed through it -

I used AutoCAD and RISA section to obtain the section properties, and I used chapter F9 to obtain the limit due to lateral-torsional buckling. To try and accurately model it, however; I used all the section properties of the composite section, used the overall 'd' of the section and assumed the bottom of the 'T' to be compact and not fail locally (since it's a tube). Thanks for the response though