Question

As per IS:456, in limit state method of design, the maximum compressive strain in axial compression is taken as

• A. 0.02
• B. 0.002
• C. 0.035
• D. 0.0035

Hint:

Remember the two key ultimate strain values for concrete from IS 456:
- Bending (Flexure): $\epsilon_{cu,max} = \textbf{0.0035}$.
- Axial Compression: $\epsilon_{c,max} = \textbf{0.002}$.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the maximum permissible compressive strain in a concrete member subjected to pure axial compression, according to the Limit State Method in IS 456.

Step 2: Detailed Explanation:
IS 456:2000 specifies different values for the ultimate compressive strain in concrete depending on the loading condition:

• Flexure (Bending): For a member subjected to bending (like a beam), the maximum compressive strain in the concrete at the extreme compression fiber is taken as

0.0035. This allows for stress redistribution and is associated with the failure of the section in bending.

• Axial Compression: For a member subjected to pure axial compression (like a column), the maximum compressive strain is taken as

0.002. This is a more conservative value because failure in pure compression is more brittle, and this strain corresponds to the point of peak stress in the idealized stress-strain curve.

• Combined Axial Compression and Bending: When a member is subjected to both, the maximum strain varies between 0.002 and 0.0035 depending on the eccentricity of the load.


Since the question specifies "axial compression," the correct value is 0.002.

Step 3: Final Answer:
The maximum compressive strain in axial compression is taken as 0.002.