WHAT ARE THE VARIOUS ASSUMPTIONS MADE IN THE THEORY OF LIMIT STATE METHOD OF COLLAPSE AND IN CASE OF REINFORCED CONCRETE MEMBER?
1. Plain sections that are plain before bending remains plain
after bending.
2. Maximum strain in concrete at the outermost fibre is taken
as 0.0035 in bending
3. The relationship between the compressive stress distributions
in concrete may be assumed to be rectangular-parabolic in design.
4. The tensile strength of the concrete is ignored.
5. The stresses in the reinforcement are derived from
representative stress strain curve for the type of steel used.
6. The maximum strain in tension reinforcement in the section
at the failure shall not be less then.
\[e_{s} ≥ { {f_{y} \over 1.5 E_{s}} + 0.002 }.\]
\[e_{s} = ~strain~ in ~steel. \]
\[f_{y} = ~characteristics ~ strength~ of~ steel ~reinforcement. \]
\[E_{s} = ~modulus ~of~ elasticity ~of~ steel. \]
7. Partial safety
factor for,
Steel =
1.15
Concrete =
1.5
8. According
to the assumptions the stress strain diagram will be explained bellow, for
simple understanding I have made the illustration of the stress strain diagram.
9. Maximum stress
in concrete = 0.45 fck
Maximum stress
in steel = 0.87 fy
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