Match the following lists:
| List-I (Member) | List-II (Maximum effective slenderness ratio) |
|---|---|
| A.A member carrying compressive loads resulting from dead and imposed load | 1.400 |
| B.A member subjected to compression forces resulting only from combination with wind/earthquake actions, provided the deformation of such members does not adversely affect the stress in any part of the structure | 2.180 |
| C.Compression flange of a beam against lateral torsional buckling | 3.250 |
| D.Members always under tension (other than pre-tensioned members) | 4.300 |
Select the correct answer using the code given below (A-B-C-D):
- A2 - 3 - 4 - 1Correct
- B3 - 2 - 1 - 4
- C1 - 4 - 3 - 2
- D4 - 1 - 2 - 3
Solution
Concept
IS 800:2007 gives upper limits of slenderness ratio (KL/r) for different members.
Formula
λ = KL/r
Step-by-step solution
1. Compression member with dead and imposed load: λmax = 180, so P-2. 2. Member in compression only due to wind/earthquake combination: λmax = 250, so Q-3. 3. Compression flange of beam against lateral torsional buckling: λmax = 300, so R-4. 4. Member always in tension (not pre-tensioned): λmax = 400, so S-1. 5. Code: 2-3-4-1, so option A.
Explanation
IS 800:2007 limits the slenderness ratio so members do not become too flexible. Main compression members get the lowest limit (180). Members that are always in tension can be very slender (400).
Why the other options are wrong
B, C and D all give wrong limits. For example, they give 400 to compression members or 180 to tension members, which does not match IS 800.
Shortcut
Order of limits: main compression 180 < wind/EQ compression 250 < beam flange 300 < always tension 400.
Common mistake
Mixing up the wind/EQ compression limit (250) with the beam compression flange limit (300).
Correct answer: A) 2 - 3 - 4 - 1