Q.74 As per IS 456:2000, which of the statement regarding longitudinal reinforcement in the RCC column is INCORRECT?
- AMinimum 8 longitudinal bars is to be provided in a column having helical reinforcement within the helical region.Correct
- BMinimum 4 longitudinal bars is to be provided in a rectangular column.
- CMinimum 6 longitudinal bars is to be provided in a circular column.
- DMinimum diameter of longitudinal bars shall not be less than 12 mm.
Solution
Concept
IS 456 requires a column with helical reinforcement to have at least 6 longitudinal bars within the helix, not 8.
Step-by-step solution
1. IS 456 rules for longitudinal bars in columns: rectangular column needs minimum 4 bars. 2. Circular column needs minimum 6 bars. 3. Bar diameter must not be less than 12 mm. 4. A column with helical reinforcement needs at least 6 longitudinal bars within the helix. 5. Option A says 8 bars, which is wrong. So the answer is (A).
Explanation
IS 456 asks for at least 6 longitudinal bars inside the helical reinforcement, so the statement with 8 bars is incorrect. The other statements (4 bars for rectangular, 6 bars for circular, minimum 12 mm diameter) are correct as per IS 456.
Why the other options are wrong
B: Correct statement. Minimum 4 bars in a rectangular column. C: Correct statement. Minimum 6 bars in a circular column. D: Correct statement. Minimum bar diameter is 12 mm.
Shortcut
Remember 4-6-6-12: rectangular 4 bars, circular 6 bars, helical 6 bars, minimum diameter 12 mm.
Common mistake
Thinking helical columns need 8 bars. IS 456 asks for only 6.
Correct answer: A) Minimum 8 longitudinal bars is to be provided in a column having helical reinforcement within the helical region.