The stress distribution diagram at the base of a circular chimney is a rectangle (uniform compressive stress over the whole base). From this it may be concluded that:
Try it first: pick an option, then read the explanation.
Correct answer: C. the chimney is subjected to direct compressive stress only
Asked in SSC JE 10/10/2023 (10 am–12 pm)
Detailed Explanation
The self-weight W of a chimney gives a direct compressive stress W/A that is the same at every point of the base. Wind produces a bending moment, whose stress varies linearly — compression on the leeward side, tension on the windward side.
Why “the chimney is subjected to direct compressive stress only” Is Correct
A rectangle has the same ordinate everywhere, so there is no linear (bending) component. The chimney carries direct compressive stress only — for example when there is no wind.
Why the Other Options Are Wrong
- A. the chimney is subjected to bending stress only: Bending alone gives two equal and opposite triangles (tension and compression).
- B. the chimney is subjected to both bending and direct compressive stress: Direct plus bending gives a trapezium, not a rectangle.
- D. the chimney is subjected to wind pressure only: Wind pressure causes bending, which would make the diagram non-uniform.
Key Point
Rectangular base-stress diagram ⇒ pure direct (axial) stress, no bending.
Key Concepts for Students
- Wind on a chimney: σ = W/A ± M/Z at the base.
- For no tension in a hollow circular base, e ≤ (D² + d²)/(8D).
- Bending stress alone is zero at the neutral axis and maximum at the edges.
Practice more: this is question 5 in Bending and Shear Stress MCQs – Part 1. Try the whole set and check every answer instantly.