In Limit state design, the limiting value of depth of neutral axis for M20 and Fe250 is
- A0.53 dCorrect
- B0.48 d
- C0.45 d
- D0.43 d
Solution
Concept
Limiting neutral axis depth for Fe250
Formula
xu,max = 0.53d
Step-by-step solution
1. According to IS 456-2000, limiting depth of neutral axis xu,max/d depends solely on the yield strength of steel. 2. For Fe250 grade steel, the maximum depth of neutral axis xu,max is equal to 0.53 d. 3. Concrete grade M20 does not alter this strain-based limiting neutral axis depth ratio. Answer: A
Explanation
In limit state design as per IS 456-2000, the limiting depth of the neutral axis depends solely on the yield strength of the steel reinforcement. For mild steel with Fe 250, the limiting depth is calculated as 0.53 times the effective depth d. Higher grade steels like Fe 415 and Fe 500 have lower limiting values of 0.48d and 0.46d respectively.
Why the other options are wrong
B) 0.48 d is the limiting neutral axis depth for Fe415 grade steel. C) 0.45 d is not a standard limiting neutral axis depth per IS 456-2000. D) 0.46 d is the limiting neutral axis depth for Fe500 grade steel.
Shortcut
Neutral axis depth limit: Fe250 = 0.53d, Fe415 = 0.48d, Fe500 = 0.46d.
Common mistake
Confusing the limiting neutral axis depth factor for Fe250 (0.53d) with Fe415 (0.48d).
Correct answer: A) 0.53 d