What is the value of slope on the inside face of the flange for all the standard I-sections and channels sections of steel?
- A16%
- B16 2/3%Correct
- C9%
- D12%
Solution
Concept
Standard rolled I-beams and channels have tapered flanges. The inside face of the flange has a standard slope of 16 2/3% (2 in 12).
Formula
Slope = 2/12 × 100 = 16 2/3%
Step-by-step solution
1. Standard I-sections and channels are rolled with tapered flanges. 2. The standard taper of the inside flange face is 2 in 12, that is 1 in 6. 3. In percent: (1/6) × 100 = 16.67% = 16 2/3%. 4. So the answer is option B.
Explanation
Standard I-sections and channels do not have parallel flanges. The inner face of the flange is tapered. The standard slope of this taper is 1 in 6, which is 16 2/3%.
Why the other options are wrong
A: 16% is only close to the value, not the exact standard value. C: 9% is too small and is not a standard flange taper. D: 12% is not the standard taper. Students may confuse it with the '2 in 12' ratio.
Shortcut
Remember '2 in 12' = 1 in 6 = 16 2/3%.
Common mistake
Writing 16% instead of the exact 16 2/3%, or confusing the slope with the flange angle (for example 98° or 96°) given in IS 808 tables.
Correct answer: B) 16 2/3%