Q.45 Based on the slenderness ratio, a steel column is found to be an intermediate column. The failure of such a column is visible as:
- Aonly buckling
- BThe steel column will not fail but remain unstable.
- Ca mixed mode of buckling and crushingCorrect
- Donly crushing
Solution
Concept
An intermediate column fails by a mix of crushing (yielding) and buckling.
Formula
λ = Le / rmin
Step-by-step solution
1. Find the slenderness ratio λ = Le / rmin. 2. Small λ (short column): failure is by crushing (direct stress reaches yield). 3. Large λ (long column): failure is by elastic buckling (Euler). 4. Medium λ (intermediate column): failure is partly crushing and partly buckling (inelastic buckling). 5. So the answer is (C) mixed mode of buckling and crushing.
Explanation
Short columns fail by crushing and long columns fail by buckling. An intermediate column is in between, so it fails by a combination of both modes. Formulas like Rankine-Gordon and IS 800 column curves are used for this range.
Why the other options are wrong
A: Only buckling happens in long (slender) columns. B: Every column fails when the load is high enough. Instability itself is a failure. D: Only crushing happens in short columns.
Shortcut
Short = crushing, Long = buckling, Intermediate = both.
Common mistake
Thinking an intermediate column fails only by buckling because it is not short.
Correct answer: C) a mixed mode of buckling and crushing