The maximum bending stress in an I-beam occurs at the:
Try it first: pick an option, then read the explanation.
Correct answer: B. outermost fibre
Asked in SSC JE 01/03/2017 (Evening)
Detailed Explanation
Bending stress varies linearly with distance from the neutral axis, whatever the shape of the section.
Why “outermost fibre” Is Correct
The largest y is at the top or bottom edge of the flanges, so the maximum bending stress is at the outermost fibre. (Shear stress, in contrast, is largest at the neutral axis.)
Why the Other Options Are Wrong
- A. neutral axis: Bending stress is zero at the neutral axis.
- C. junction of web and flange: At the web–flange junction y is smaller than at the outer edge.
- D. section where shear stress is maximum: Shear stress is maximum at the N.A., where bending stress is zero.
Key Point
Bending stress: zero at the N.A., maximum at the extreme fibres.
Key Concepts for Students
- I-beams put most material where σ is large.
- Shear is carried mostly by the web.
- Combined stresses are checked at the web–flange junction.
Practice more: this is question 44 in Bending and Shear Stress MCQs – Part 3. Try the whole set and check every answer instantly.