As per IS 800:2007, what is the effective length of prismatic compression member for the restrained (both in translation and rotation) boundary conditions at both the ends ? (Take L as actual length of the member)
- A2 L
- B0·65 LCorrect
- C0·8 L
- D1·2 L
Solution
Concept
Effective length factors (IS 800 Table 11)
Step-by-step solution
1. Both ends fixed (restrained against translation and rotation): K = 0.65 (design value; theoretical 0.5). 2. Effective length = 0.65 L.
Explanation
IS 800 adopts 0.65 L for the fully restrained case, which is a little higher than the theoretical 0.5 L to allow for imperfect fixity. Other values: 0.80 L (fixed–pinned), 1.2 L (one end translation free but rotation restrained), 2.0 L (fixed–free).
Why the other options are wrong
2 L is for the cantilever case, 0.8 L is for one end fixed and the other pinned, and 1.2 L is for translation free at one end with rotation restrained at both.
Shortcut
0.65, 0.8, 1.0, 1.2, 1.5, 2.0 are the IS 800 factors.
Common mistake
Using 0.5 L.
Correct answer: B) 0·65 L