Open Thin-Walled Sections

When the median wall line is closed, the section is said to be an open section. Open sections in torsion, where the wall is thin, have shear stress as:

$$\tau =G\theta c=\frac{3T}{L{c}^2}$$

where:

• $T$ is torque
• $\tau$ is shear stress
• $c$ is wall thickness
• $G$ is modulus of rigidity
• $L$ is length of median line
• $\theta$ is angular twist per unit length