The section has tension and compression steel reinforcement. 

When the neutral axis depth is at infinity, c = ∞, the section is in uniform compression, all points on the section have 0.003 compressive strain.

1. Draw the strain profile for this neutral axis depth.
2. Determine the unbalanced section axial force T −(Cc +Cs) for this neutral axis depth.

When the neutral axis depth is at zero, c = 0, the section is in uniform tension. Effectively, all points on the section have 0.003 tensile strain.

3. Draw the strain profile for this neutral axis depth.
4. Determine the unbalanced section axial force T −(Cc +Cs) for this neutral axis depth.

When the neutral axis depth is at half the section depth, c = h/2=10 inch. 5. Draw the strain profile for this neutral axis depth.

6. Determine the unbalanced section axial force T −(Cc +Cs) for this neutral axis depth.

 

12 in 2.5 in 2 #9 Gr. 60 20 in f=4000 psi 4 #9 Gr. 60 12.5 2.5 in