Question

Can you compare the main assumptions as differences and common sides between the elastic limit state and ultimate limit states?

Answer 1

Differences:-

● Elastic Limit state

1. The stresses in the reinforcement are taken from the stress-strain curve for the for various type of steel.   
2.   The maximum strain in concrete at the outermost compression fibre is taken as 0.0035 in bending.   
3. The variation in stress-strain distribution in concrete is assumed to be parabolic.

● Ultimate limit state:-

1. Stress in reinforcement varies linearly with strain up to the specified yield strength and it implies that the strain hardening of steel is ignored.
2. Maximum strain in concrete is develop at 0.003 strain in the extreme compression fiber.
3. Variation of Compressive stress distribution of concrete can be represented by the corresponding stress-strain relationship of concrete.

Common side:-

1. The tensile strength of the concrete is ignored.   
2. Plane section remain plane befote and after the bending. so that the stress is directly propotional to the strain.

Thank you.