ANALYTICAL METHOD TO DETERMINE ELASTO-PLASTIC MOMENT-CURVATURE RELATIONSHIP OF BENDING SECTION

On the assumption of a plane section and an ideal elasto-plastic model of steel, parameters such as the height coefficient of a pure bending compression zone and a plastic zone are constructed. The relationship between internal force and strain is analyzed on rectangle and I-shape steel sections. The corresponding strain change area is obtained. Only by using the tension and pressure edge strains as the independent variables, the analytical expressions are established, including all parameters, variables and the analytical moment-axial force expression at the ultimate condition of elasticity, unilateral and bilateral plasticity. Axial force-moment-–curvature curves with fixed axial force and with fixed curvature, and moment-axial force interaction curves are set up by an inverse method. These curves illustrate the relationship and whole change process of axial forces, moments and curvatures.