Question

A column whose slenderness ratio is greater than 120 is known as

• A. Short column
• B. Medium column
• C. Long column
• D. Composite column

Hint:

Remember the failure modes based on slenderness ratio ($\lambda$):
- Low $\lambda$ $\rightarrow$ Short Column $\rightarrow$ Fails by Crushing.
- High $\lambda$ $\rightarrow$ Long Column $\rightarrow$ Fails by Buckling.
- Intermediate $\lambda$ $\rightarrow$ Intermediate Column $\rightarrow$ Fails by Crushing + Buckling.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the classification of a column based on a given slenderness ratio.

Step 2: Detailed Explanation:
Columns are compression members that are classified based on their length, cross-sectional dimensions, and end conditions, which are all combined into a single parameter called the

slenderness ratio ($\lambda$). The slenderness ratio determines the column's mode of failure.
\[ \lambda = \frac{L_{eff}}{k_{min}} \] where $L_{eff}$ is the effective length and $k_{min}$ is the minimum radius of gyration.
The classifications are generally:

• Short Columns: Have a small slenderness ratio. They fail by crushing (yielding of the material) at a stress close to the material's compressive strength. Their strength is independent of their length.

• Long Columns (or Slender Columns): Have a large slenderness ratio. They fail by elastic

buckling, a sudden lateral deflection, at a stress that can be much lower than the material's yield strength. Their failure load is highly dependent on their length and stiffness. The Euler column formula applies to these.

• Intermediate Columns: Fall between short and long columns. They fail by a combination of crushing and buckling (inelastic buckling).


The specific numerical values for these ranges depend on the material and the design code. For steel, a common rule of thumb (though it varies) might place the transition to long columns somewhere between a slenderness ratio of 80 and 120. A value

greater than 120 is definitively in the range of a

long column, where buckling is the primary failure mode.

Step 3: Final Answer:
A column whose slenderness ratio is greater than 120 is known as a long column.