Cw for an unsymmetrical I-shape

[14159]

Does anyone have a solution or reference to a solution for Cw for an unsymmetrical I-shaped structural steel beam?

I spent 2 hours yesterday looking through my advanced mech of materials, cold-formed steel design, structural steel design, AISC Manuals, AISC Torsion DG9, internet, etc, and every single source cowardly only presents doubly-symmetrical beams.

Any help would be greatly appreciated.
DBD

 

[haynewp]

Cw=((tf*h^2)/12)*(b1^3*b2^3/(b1^3+b2^3))

It is in the appendix of Salmon and Johnson, flanges have the same thickness (tf).

 

[14159]

Thank you very much!

One of my buddies has my S&J -- I need to go get it!

DBD

 

[14159]

I need an equation for the case of different flange thicknesses.

Anybody have one of these?

DBD

 

[WillisV]

My 2 cents - unless the flange thicknesses are extremely different I cannot imaging your design being cut so close that you cannot just conservatively use the smaller thickness in the equation from S&J posted previously.

BUT...if you reeeeeally need it the following paper on torsional constants from the Canadian Steel Institute has it on page 10 along with some other useful information and examples:

http://www.cisc-icca.ca/files/technical/techdocs/updates/torsionprop.pdf

 

[14159]

Thanks WillisV! That is exactly what I need.

For my application, I have to have the exact formula.

DBD