Question

The section in which concrete is not fully stressed to its maximum permissible value while stress in steel reaches its maximum value is called ____

• A. Under reinforced section
• B. Critical section
• C. Over reinforced section
• D. Balanced section

Hint:

Types of RCC sections: \[ \boxed{ \begin{aligned} \text{Under-reinforced} &\rightarrow \text{Steel yields first}\\ \text{Balanced} &\rightarrow \text{Steel and concrete reach limit together}\\ \text{Over-reinforced} &\rightarrow \text{Concrete crushes first} \end{aligned} } \]

Answer 1

The Correct Option is A

Step 1: picture the strain state at failure for the three named sections.
A section can fail because concrete crushes first, because steel yields first, or because both reach their limiting strain together, and each of these is given its own name.
Step 2: match the given condition to one of these.
Here the steel reaches its maximum permissible stress while the concrete is still below its maximum permissible stress, meaning the steel is the weaker, governing element and there is less steel than what would exactly balance the concrete capacity.
Step 3: name this condition.
A section with less steel than the balanced amount, where steel governs failure while concrete still has reserve capacity, is by definition an under reinforced section.
\[ \boxed{\text{Under reinforced section (option A)}} \]