The gross section of the web of a beam is defined as:
Try it first: pick an option, then read the explanation.
Correct answer: A. depth of the beam multiplied by its web thickness
Asked in SSC JE 23/01/2018 (Evening)
Detailed Explanation
In an I-beam, the flanges carry most of the bending moment and the web carries most of the shear force. Shear design uses the area of the web.
Why “depth of the beam multiplied by its web thickness” Is Correct
The gross area of the web is taken as the overall depth of the beam × web thickness. It is used to work out the average shear stress (V ÷ d·tw) and the shear capacity of steel beams.
Why the Other Options Are Wrong
- B. width of the flange multiplied by its web thickness: Flange width has nothing to do with the web area.
- C. sum of the flange width and depth of the beam multiplied by the web thickness: Adding the flange width is wrong.
- D. None of these: Option (a) is the correct definition.
Key Point
Web area A_w = d × t_w; carries the shear.
Key Concepts for Students
- Average shear stress in the web ≈ V/(d·t_w).
- Flanges resist bending (flange force ≈ M/lever arm).
- Thin deep webs may need stiffeners against buckling.
Practice more: this is question 8 in Beams and Trusses MCQs – Part 1. Try the whole set and check every answer instantly.