Torsion Constant - Stiffeners

[IreneAdler]

Hi! From what I know torsion constant value is highest when the section is a closed shape. But what if the section is not enough to accommodate applied loads? Could we put stiffeners to increase the shape's torsional stiffness ? Just like in the picture (plan view of an aluminum tube-green). Could we consider the snap on cover (high-lighted in red) to be like a solid part of the section? Or will the steel channel (yellow) help with the torsion constant?

Thank you in advance for your ideas.

 

[Ron]

Yes. This is commonly done in storefront/curtain wall systems to reinforce the extruded tube. Do not include the snap cap....it offers nothing.

I would also suggest that when you reinforce aluminum extrusions with steel sections, that you isolate the two by a heavy paint coating on the steel to mitigate potential corrosion issues of the dissimilar materials being in contact.

 

[Leftwow]

I would not assume that a stiffener plate would help the torsional deflection. It would only reduce the deflection of the beam at the stiffener plate thickness.

 

[KootK]

Neither the cap nor the channel possesses a longitudinal shear connection to the aluminum tube. As such, neither improves the aluminum tube's torsional properties through composite torsional behavior. The channel will possess some meaningful torsional stiffness in it's own right and that will add to the torsional stiffness of the aluminum tube in a non-composite fashion.



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.