orsional constant t beams

huangyhg

torsional constant t beams
does anyone have the formula for j (torsional constant) for a t section beam in cm4?
or c torsional modulus?
thanks
andrew299
check out our whitepaper library.
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
see the thread
the statement by btruebloodfff"> is incorrect: that formula is far from being true for open thin sections.
andrew299fff">: 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
i like to direct you to an excellent document published the aisc. it is design guide number 9 titled torsional analysis of structural steel   
good luck