Fig. 3
From: Strength Calculation of Short Concrete-filled Steel Tube Columns
The family of concrete deformation diagrams with a step-by-step increase of axial deformations: a the coordinates of diagram vertices, b to the determination of stresses with relative deformation increase; 1—uniaxial compression, 2, 3—volumetric compression at intermediate stages of deformation, 4—volumetric compression in the limiting state.