Question

The standard shear flow formula \[ q=\frac{VQ}{I} \] is not applicable to thick-walled sections. The primary reason is

• A. Thick sections do not experience shear forces
• B. The moment of inertia (\(I\)) cannot be calculated for thick sections
• C. The shear stress is no longer uniform across the thickness of the section
• D. Thick sections are always perfectly rigid and do not deform under shear

Hint:

The formula \[ \boxed{ q=\frac{VQ}{I} } \] is valid only for \[ \boxed{\text{thin-walled sections}} \] where the shear stress is assumed to be approximately uniform across the wall thickness.

Answer 1

The Correct Option is C

Step 1: Recall the shear flow relation. The shear flow expression \[ \boxed{ q=\frac{VQ}{I} } \] is derived for thin-walled sections. It assumes that the shear stress is nearly uniform through the wall thickness.

Step 2: Identify why it fails for thick sections. In thick-walled members, the shear stress varies significantly across the thickness. Therefore, the thin-wall assumption is no longer valid. Hence, \[ \boxed{ \text{The shear stress is no longer uniform across the thickness of the section.} } \] Thus, \[ \boxed{(C)} \] is the correct answer.