As per the code, the effective length of a column fixed at both ends is (L = Length of column)
- A0.50 L
- B0.65 LCorrect
- C0.85 L
- DL
Solution
Concept
Effective length of column fixed both ends
Formula
NONE
Step-by-step solution
1. The theoretical effective length of a compression member fully restrained against rotation and translation at both ends is 0.50 L. 2. Practical end conditions cannot provide perfect rotational restraint. 3. As per IS 800, the recommended design effective length for a column fixed at both ends is 0.65 L. Answer: B
Explanation
The theoretical effective length for a column fixed at both ends is 0.50 L, but design codes recommend a value of 0.65 L to account for practical end restraint conditions and imperfect rigidity in actual structures. This safety margin accounts for slight rotations or displacements at the supports. Therefore, 0.65 L is used in standard compression member design calculations.
Why the other options are wrong
A) 0.50 L is the theoretical effective length, whereas codes specify 0.65 L for practical design. C) 0.85 L is the effective length for a column fixed at one end and hinged at the other. D) L is the effective length for a column hinged at both ends.
Shortcut
Recommended design effective length for both ends fixed is 0.65 L (theoretical is 0.50 L).
Common mistake
Choosing the theoretical effective length value (0.50 L) instead of the recommended design value (0.65 L) specified by the code.
Correct answer: B) 0.65 L