For design calculations, the modulus of elasticity of steel (Es) is generally assumed as Choose the most appropriate standard value and unit.

Introduction:
The elastic modulus of reinforcing steel is a fundamental property used in deflection, crack width, and composite action checks. Designers typically adopt a standard value suitable for most carbon steel rebars.

Given Data / Assumptions:

• Carbon steel reinforcement used in normal temperature ranges.
• Linear elastic behavior assumed up to yield for serviceability checks.

Concept / Approach:

For structural design, Es is taken as approximately 200,000 N/mm², which is equivalently 200 kN/mm². This value aligns with material test data and code recommendations.

Step-by-Step Solution:

Verification / Alternative check:

Material certificates for Fe415/Fe500 typically report Es near 200 GPa, confirming the chosen value.

Why Other Options Are Wrong:

225, 250, 275, and 150 kN/mm² do not reflect the standard modulus used in design and would misstate stiffness.

Common Pitfalls:

Confusing yield strength (e.g., 500 MPa) with modulus; mixing units of GPa, N/mm², and kN/mm².

Final Answer:

200 kN/mm²