Torsional Constant T beams

[aesoton]

Does anyone have the formula for J (Torsional Constant) for a T section beam in cm4?
or C Torsional Modulus?
Thanks
Andrew299

 

[btrueblood]

The torsional moment of inertia is "J", my Roark's gives
a general formula

J = Ix + Iy = I1 + I2

Assuming x & y axes (or axes 1 & 2) are orthogonal.

Hopefully you have the equations for the moments of inertia for a T-section, or can derive them from rectangular equations and the offset axis theorem. I can try and write them out, but they get a little hairy, and defining some of the terms will be difficult without a diagram. I'm using _Roark's Formulas for Stress and Strain_, W. Young, 6th ed., McGraw-Hill, 1989; see page 63.

Ben T

 

[Denial]

See the thread
Thread194-92351
in the "Civil/Environmental Other" forum, where I have just placed a post.

 

[prex]

The statement by btrueblood is incorrect: that formula is far from being true for open thin sections.
andrew299: look in the site below, under Beams -> Cross sections -> I beams -> Cut : by clicking onto 'Formulas' you'll see your formula.
And if you could avoid cross posting...

prex

http://www.xcalcs.com

Online tools for structural design

 

[Lutfi]

I like to direct you to an excellent document published the AISC. It is Design Guide number 9 titled Torsional Analysis of structural steel members. You can buy/view this document on their web site

http://www.aisc.org

If you are a member, you can download it in PDF. The design guide is an excellent source and reading on torsional analysis. It is full of charts for various boundary conditions not to mention torsional constants for various steel shapes ready for use.

Good luck