Design Stress-Strain curve of concrete is
- AA perfect straight line up to failure
- BA straight line up to 0.002% strain value and then parabolic up to failure
- CParabolic up to 0.002% strain value and then a straight line up to failureCorrect
- DHyperbolic up to 0.002% strain value and then a straight line up to failure
Solution
Concept
Design Stress-Strain Curve of Concrete
Formula
For strain 0 ≤ ε ≤ 0.002: f = 0.446 · f\_ck · \[2 · (ε / 0.002) - (ε / 0.002)²\] For strain 0.002 ≤ ε ≤ 0.0035: f = 0.446 · f\_ck
Explanation
The design stress-strain curve for concrete increases parabolically from zero up to a strain value of 0.002. Beyond a strain of 0.002, the stress remains constant, forming a horizontal straight line until ultimate failure occurs at a strain of 0.0035.
Shortcut
Remember "P then S" (Parabolic first, then Straight line): × Parabolic shape from zero up to 0.002 strain. × Straight (flat/horizontal) line from 0.002 to ultimate failure at 0.0035 strain.
Common mistake
Many students mistakenly choose Option B because they confuse the sequence, assuming the initial portion is linear/straight before turning parabolic, or they confuse strain values (0.002 vs 0.002%).
Correct answer: C) Parabolic up to 0.002% strain value and then a straight line up to failure