Abstract
Inelastic behaviors of a hollow circular section and a H-shaped section under constant axial force are investigated in terms of the transformations of the yield surfaces presented by the parameters P/P_y, M_x/M_px and M_y/M_py, where P_y, M_px and M_py are the yield axial force and the plastic moments about the principal axes under the monotonic uniaxial loading respectively. Characteristics of the subsequent yield surfaces for three values of constant axial thrust are discussed. The preloading paths adopted here are three types of that for each section, and the influence of cyclic loading of the bending moments are examined also.
