Question

Which section is good from ductility point of view?

• A. Under reinforced section
• B. Balanced section
• C. Over reinforced section
• D. Section with special steel

Hint:

Failure modes of RC sections: \[ \boxed{ \begin{aligned} \text{Under reinforced} &\rightarrow \text{Ductile (Preferred)}\\ \text{Balanced} &\rightarrow \text{Simultaneous failure}\\ \text{Over reinforced} &\rightarrow \text{Brittle (Not preferred)} \end{aligned} } \]

Answer 1

The Correct Option is A

Step 1: Three possible failure states.
A reinforced concrete beam section can be under reinforced, balanced, or over reinforced, depending on whether the steel or the concrete reaches its limiting strain first.
Step 2: What happens in each case.
In an over reinforced section the concrete crushes suddenly while the steel is still well below its yield strain, so failure is sudden and brittle. In a balanced section both reach their limits almost together, which is still a fairly abrupt failure. In an under reinforced section the steel yields first, stretching a lot before the concrete finally crushes.
Step 3: Connecting this to ductility.
This steel yielding shows up as visible cracking and noticeable deflection well before collapse, giving people time to notice distress. That gradual, warning-rich behaviour is exactly what ductility means in structural design.
\[ \boxed{\text{Under reinforced section}} \]