Assumption: Top flange is in compression and bottom flange is in tension.
PNA: The plastic neutral axis is defined as the axis that divides the cross section such that the compression force from the compression area is equal to the tension force from the tension area. Its’ location is denoted by, yp.
b: Width of the flange
tf1: Thickness of top flange
tf2: Thickness of bottom flange
tw: Thickness of web
d: Total depth of section
Tc: Compression force
Tf: Tension force
Yield Strength of steel = 350 MPa