The shear stress distribution of a beam section is zero at the top, jumps suddenly to a higher value at one junction near the top, and then follows a parabolic curve down to zero at the bottom. Identify the beam section.
Try it first: pick an option, then read the explanation.
Correct answer: A. Angle section
Asked in SSC JE 14/11/2022
Detailed Explanation
Read the diagram from the width profile. A sudden jump in τ happens only where the width changes suddenly (τ ∝ 1/b at a level). A smooth curve means the width changes gradually.
Why “Angle section” Is Correct
One jump near the top, followed by a single parabola to zero at the bottom, matches a section with one wide part at the top and a narrow stem below — the angle section among the options. (A T-section would give the same picture.)
Why the Other Options Are Wrong
- B. Triangular: A triangle has a smooth curve with its peak at mid-height, and no jump.
- C. Circular: A circle gives a smooth curve with its peak (4/3 τavg) at the neutral axis.
- D. I-section: An I-section has two jumps — at the top and the bottom flange–web junctions.
Key Point
Jumps in a shear stress diagram mark sudden changes in width; one jump near the top ⇒ angle (or T).
Key Concepts for Students
- Step ratio at a junction = flange width / web width.
- The web carries most of the shear in flanged sections.
- Symmetric sections give symmetric shear diagrams.
Practice more: this is question 6 in Bending and Shear Stress MCQs – Part 1. Try the whole set and check every answer instantly.