Section 10.1.6 Concrete Stress-Strain Relationship
The default concrete cross section stress-strain curve is implemented as the Portland Cement Association (PCA) linear/parabolic curve.
Typical Stress vs Strain Curve for concrete
Application can also choose from other available standard stress-strain curves or can input a stress strain curve as a set of stress-strain points. For the user input curves, no negative slopes are permitted (but slopes of zero are permitted).