Reinforced concrete beams: definition of the critical neutral axis Statement: The critical neutral axis of an RCC beam is located at the centre of gravity of the given section.

Introduction / Context:
In reinforced concrete (RCC), the position of the neutral axis depends on the transformed section under bending, not merely the geometric centroid. The critical neutral axis separates tension and compression zones and is key to determining whether a section is under-reinforced, balanced, or over-reinforced.

Given Data / Assumptions:

• Transformed section method or limit-state stress block.
• Concrete carries compression; steel primarily carries tension.
• Plane sections remain plane; bond is adequate.

Concept / Approach:
The neutral axis is obtained from force equilibrium: compressive resultant in concrete equals tensile force in steel (plus compression steel, if any). Its position therefore depends on material properties (modular ratio m or design stress block) and reinforcement area and placement, not on the centroid of the gross concrete section.

Step-by-Step Solution:
Transform steel area to equivalent concrete area using m = Es / Ec (working stress) or use code stress block (limit state).Compute compressive stress block and tensile force in steel.Set compression = tension and solve for neutral axis depth x.Critical neutral axis corresponds to the balanced failure condition (simultaneous concrete crushing and steel yielding), not the geometric centroid.

Verification / Alternative check:
Code tables provide limiting neutral axis depth (e.g., x_u,lim / d depends on steel grade), confirming dependence on material behavior and reinforcement, not on geometric centroid alone.

Why Other Options Are Wrong:
Statements limiting to section type or m = 1 are irrelevant; the NA is controlled by equilibrium and compatibility with material laws.

Common Pitfalls:
Using gross-section centroid for RCC bending; ignoring compression reinforcement and tension steel position in NA computation.

Final Answer:
False