Definition of a short reinforced concrete column: A column may be treated as a short column if its slenderness ratio (effective length / least lateral dimension) is less than which threshold?

Introduction / Context:
Column classification into short or slender governs the design approach. Short columns primarily fail by material crushing when overloaded, while slender columns are dominated by instability (buckling) and require second-order effects to be considered.

Given Data / Assumptions:

• Slenderness ratio defined as effective length divided by least lateral dimension.
• Ordinary building column with braced conditions.
• Code-aligned threshold used for classification.

Concept / Approach:
If the slenderness ratio is below a small threshold, deflection magnification and secondary moments are minimal and crushing governs. A commonly used boundary for reinforced concrete is 12, below which columns are treated as short for design purposes.

Step-by-Step Solution:
Compute effective length Le based on end restraints and bracing.Obtain least lateral dimension b of the column.Evaluate slenderness ratio SR = Le / b; if SR < 12, treat as short column.

Verification / Alternative check:
Comparing with typical limits—higher limits indicate growing slenderness and buckling sensitivity—confirms that 12 is a conservative boundary for many reinforced concrete design guides.

Why Other Options Are Wrong:

• 18, 24, 30, 40: these values permit too much slenderness; second-order effects can no longer be neglected safely.

Common Pitfalls:
Using unsupported length instead of effective length, neglecting sway sensitivity, or using the larger lateral dimension rather than the least.

Final Answer:
12.