Question

In limit state design of concrete structures, the strain distribution assumed is

• A. Parabolic
• B. Rectangular
• C. Linear
• D. Non-linear

Hint:

A key distinction in Limit State Design:
- STRAIN distribution is LINEAR (because plane sections remain plane).
- STRESS distribution in concrete is NON-LINEAR (rectangular-parabolic).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks about the assumed shape of the strain distribution across the depth of a reinforced concrete section in the Limit State Method of design.

Step 2: Detailed Explanation:
One of the fundamental assumptions in the flexural design of reinforced concrete beams, both in the Working Stress Method and the Limit State Method, is that "plane sections remain plane after bending".
This assumption means that the strain at any point across the depth of the beam is directly proportional to its distance from the neutral axis.
If you plot the strain values versus the depth of the section, this proportional relationship results in a straight line. Therefore, the

strain distribution is assumed to be linear.
It is important not to confuse this with the stress distribution.
-

Strain Distribution: Assumed to be

linear.
-

Stress Distribution: Assumed to be

non-linear (rectangular-parabolic) for concrete in the Limit State Method, and linear in the Working Stress Method.

Step 3: Final Answer:
In the limit state design of concrete structures, the strain distribution is assumed to be linear.