Ultimate strength analysis of reinforced concrete sections subject to axial force and biaxial bending Original Research Article

Two algorithms are presented for evaluating the ultimate strength capacity of reinforced concrete (RC) sections of arbitrary shape, either single- or multicell, subjected to axial force and biaxial bending. Both algorithms adopt a secant strategy for the solution of the nonlinear equilibrium equations, thus resulting in a considerable rate of convergence. An original integration formula is proved. It represents the rationale for evaluating the geometric or elastic properties of the section by carrying out the integrations along the relevant boundary. Further, in the usual case of polygonal sections, the boundary integrals can be expressed solely as a function of the position vectors of the vertices of the section. The numerical performances of the two algorithms, concerning both the accuracy of the results and the convergence properties, have been extensively tested for a wide range of RC sections. Finally, in order to show the effectiveness of the proposed approach, the interaction surface of each kind of section has been plotted and the relevant values have been reported in table form.