# Torsion Constant for Rectangle Cross-section

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

### Torsion Constant for Rectangle Cross-section formula

$$\large{ J = a\;b^3 \left[ \frac{1}{3} - 0.21 \; \frac{b}{a} \; \left(1- \frac{b^4}{12\;a^4} \right) \right] }$$

Where:

$$\large{ J }$$  (Greek symbol alpha) = torsion constant

$$\large{ a }$$ = length of long edge of an rectangle

$$\large{ b }$$ = length of short edge of an rectangle