Abstract:  In order to study the fire behavior of large space steel structures, the buckling of steel components would be taken into consideration. In this paper, a constitutive model with buckling property of steel component is established for  finite element analysis of large space structures at high temperature. By studying the bending deformation of axially loaded steel components at various temperatures, the nominal axial stiffness of the steel components with buckling property is
theoretically derived. Influence of slenderness ratio, initial imperfection, and critical load on the nominal axial stiffness is discussed. Using the energy balance method, the nominal axial stiffness is replaced by the equivalent stiffness. Then a bilinear stress-strain constitutive model of steel materials for steel components with buckling property is established. The model is verified by the numerical calculation.