Autodesk Inventor

[#1]

Anybody knows the equation for finding out "Torsinal Rigidity Modulus" for pipes.

I am craeting a personnel library for pipes. In the Family  Table editor there is a column named  Torsional Rigidity Modulus. I am trying to give an expression for this but i dont know the equation for the same.

 Hopes Somebody can help me for this equation .....

[#2]

Try here:  http://www.roymech.co.uk/Useful_Tables/Torsion/Torsion.html

[#3]

Thanks Blair...

I got another one also, hopes thats much helpful : https://engineering.purdue.edu/~ahvarma/CE%20579/References/AISC_Torsion_Guide.pdf