Tee Sections, flexion in minor axis

[DomDunk]

Goodnight,

I am implementing the verification by axial and flexion of tee sections, to use the DG31 (cellular beams). I have the following question: does the AISC not consider the flexion in minor axis of the tee sections? How can you calculate the resistant moment My? Can you assimilate the tee section to an asymmetric I beam and use the section F6?

 

[RickyTickyTavi]

I dont think F6 would be good here. I would use section F11 and treat it like strong axis plate bending: If the load was applied to the flange of the WT.

If the load was applied to the web, youre going to have all sorts of torsional effects on the section.

 

[DomDunk]

Thank you,

Yes, everything depends on the point of application of the force with respect to the shear center.

I'm going to look for literature in case someone talks about it. I warn you if I find something, to close the post.

 

[DCBII]

It's conservative to use section F11, and it's probably not far off from reality, since the stem placed at the weak-axis centroid likely does very little to stabilize the compression zone against translation and lateral-torsional buckling.

I've seen a popular commercial software package use the plastic moment for this, which I think is dangerous.

 

[DomDunk]

Autodesk Robot considers the plastic moment for very slender elements too ... I implemented the F11 section.

Thank you very much

 

[Agent666]

With tees you need to evaluate which axis is major and minor, then design accordingly. Sometimes they are swapped depending on the relative second moment of areas being the opposite way round than you might think. If the Iy about the flange is less than the Ix which places the Web stem in comp/tension then there is no flexural torsional buckling in the minor axis direction. If the opposite way round then for bending about the flange you need to consider flexural torsional buckling, like you would for any beam, usual equations apply. Warping constant is zero for tees.

 

[Agent666]

One other thing, if you are subject to FTB with the Web in comp/tension then use the provisions in your code for mono symmetric sections when considering lateral torsional buckling.