that's exactly it, because if you have axial force on the bend, it can't be 0, instead, the sum of axial forces caused by tension must equal the axial force applied on the section, i was misunderstunding with pure bending on concrete structures where that equation is valid because N is 0 in that...
The problem is the following, i have a rectangle as a cross section of steel, which is bended and compressed.. i want to use the equilibrium equations to make sure its static, but since the compressive force and the traction force aren't equal, the equilibrium equations make no sense
here's a...