Accuracy of Composite Section Nonlinear Solutions

A general nonlinear theory is presented for the strength analysis of composite sections subjected to combined uniaxial bending moment and compressive or tensile normal force. Sections are composed of three materials having arbitrary stress-strain curves and cross-sections of any geometrical form symmetrical with respect to the vertical centroidal axis. A typical numerical example consisting of a steel wide-flange section and longitudinal reinforcing bars encased in concrete is studied for various applied normal forces, different percentages of reinforcing bars and two types of concrete stress-strain curves corresponding to ultimate strains of 0.003 and 0.004, respectively. The study is carried out to determine the influence of the following on composite section ultimate bending capacity: reinforcing bars own resistance to bending, concrete tensile strength, concrete displaced by wide-flange section and reinforcing bars, type of concrete stress-strain curve, and wide-flange section residual stresses.