NONLINEAR ANALYSIS OF THIN-WALLED FRAMES AND MEMBERS WITH ARBITRARY OPEN CROSS SECTIONS.

An incremental equilibrium equation for a beam-cloumn with arbitrary open cross sections is derived in a stiffness matrix form by using a moving element coordinate system and an incremental variational principle. A segmentation method for the cross section is used to analyze the development of plastic zones in the cross section and the effect of initial residual stresses arbitrarily distributed in the cross section. Yielding of the material is judged as a bi-axial stress problem under normal and shear stresses by using the flow theory of plasticity associated with von Mises yield criterion. Validity and efficiency of the present method are shown by illustrative examples.