Elasto-Plastic Stability Analysis of the Frame Structures Using the Tangent Modulus Approach

This paper presents the procedure for stability analysis of frames in elastic-plastic domain using the concept of the tangent modulus. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. Formulation of the corresponding stiffness matrices is based upon the solution of the equation of bending of the beam according to the second order theory. Numerical analysis was performed using the code ALIN, developed in the C++ programming language

Research on the Nonlinear Stability of the Steel Spatial Arch Truss with 120m Span and 0.2 Rise-Span Ratio

The elasto-plastic stability analysis on the steel spatial arch truss with 120m span and 0.2 rise-span ratio is carried out with the finite element program ANSYS. In the analyses, two conditions which are the geometric and material nonlinear, double nonlinear under different initial geometric defects are considered. The results show that the instability modes of arch trusses are all asymmetric instability of plane, and that the buckling load and plastic development of the four arch trusses with L/500, L/400, L/300 and L/200 initial geometric defects are decreased with the increase of different initial geometric defects, and that the axial stress of all web members is about the same, but the value of which does not exceed 235Mpa.