Torsional stiffness
Torsional stiffness
(OP)
I'm trying to get an equation which will give the torsional stiffness of beams with the following cross sections: a trapezoid and a parellelogram (the polar moments of these shapes is enough). These will actually be sections in a composite beam with the end sections being triangles to close out the beam so any info calculating torsional stiffness of a composite beam structure would be a great help too!





RE: Torsional stiffness
For a rectangular tube of constant thickness then K is 2*t*t*a**b*b/(a+b) if t is small
In your research you will come across the membrane analogy. This tells you that the result for a rectangle is the upper limit for a parallelogram of the same dimensions and thickness.
Cheers
Greg Locock