The numerical nonlinear problem is reduced to a 1 Degree od freedom system, where given an axial deformation,strain, the formulation iterates over the value for the additional curvature, *p, until equilibrium defined as Eq. (4) is achieved (within a tolerance). Equilibrium is determined for a quarter of the bar, such that it involves an inflexion point (zero moment) and another end within the plastic hinge with moment m, with a relative lateral displacement of (e + w)/2.