Notation:

Fc: Concrete compressive strength

Fy: Reinforcement yield strength

Es: Reinforcement young's modulas

Units choice

Metric:

Moment in kN.m

Axial Load in kN

Fc in MPa

Fy in MPa

Es in MPa

Dimensions in mm

Areas in $mm^2$

Imperial:

Moment in kip.ft

Axial Load in kip

Fc in PSI

Fy in PSI

Es in PSI

Dimensions in in

Areas in $in^2$

Methods:

Control Points:

In this method, the main points are calculated then intermediate points between them are determined. 

Assumptions for this method: This App considers ACI assumptions as follows

1.  Reduction Factor

2. Concrete Strain limit (${\epsilon }_c=0.003\epsilon \_c=0.003$ )

3. Stress block parameters 

${\propto }_1=0.85\propto \_1=0.85$

Interaction Diagram main points 

Slices (Thorendelt):