chicopee-
What exactly is the purpose of your comment?
It is arrogant and not the least bit helpful. True as it may be, it seems the only purpose is to make yourself look informed at the expense of the OP.
And torsion, in general, is NOT an easy problem. In tubular sections, it is fairly straightforward, but for almost any other shape it is quite involved.
Structural engineers have the added burden of taking many other factors into account. Is the section torsionally restrained? Is it compact? Is there additional loading perpendicular to the cross section? In both directions?
You mechanical's may be able to design a circular shaft to transfer torque and forget about it. We don't have that luxury.