N-M-χ interaction for arbitrary cross section under biaxial bending and axial load

A numerical procedure is presented for the study of the failure mechanism of reinforced concrete sections of arbitrary shape in biaxial bending with axial force. The procedure is a fiber model, which allows to compute the moment-curvature diagram and the interaction domains using non-linear constitutive laws, also with softening post-peak branch for concrete. The numerical technique is able to find the position and the orientation of the neutral axis that determines a resultant moment, which acts along a predefined orientation angle. Analytical moment-curvature diagrams and interaction domains are compared with data published in the literature.