Which of the following is TRUE regarding stress-strain curve of concrete?
1
A straight line up to the failure.
2
Hyperbolic up to 0.002 strain value and then a straight line up to failure.
3
Parabolic up to 0.002 strain value and then a straight line up to failure.
4
Straight line up to 0.002 strain value and then parabolic up to failure.