Question

According to the basic considerations of Working Stress method for reinforced concrete design, the stress-strain relationship of steel and concrete under working loads is taken as:
1. Quadratic
2. Parabolic
3. Linear
4. Logarithmic

Answer 1

Correct Answer - Option 3 : Linear

Explanation:

According to IS 456:2000 ANNEX B, Clause B - 1.3

Assumptions made in the working stress method of design are:

1. At any cross-section, plane section before bending remains plane after bending i.e the strains are proportional to the distance from the Neutral axis and is linear.

2. All tensile stresses are taken up by reinforcement and none by concrete, i.e concrete area on the tension side is to be neglected. except as otherwise specifically permitted.

3. The stress-strain relationship for steel and concrete under working load is a straight line, i.e concrete is assumed to be elastic.

4. The value of modular ratio is 280/3σ_cbc , where σ_cbc - is the permissible stress due to bending in concrete in N/mm2

5. Bond between the steel and the concrete is perfect.