ELASTIC-PLASTIC BIFURCATION ANALYSIS OF COLUMN WEBS IN MOMENT CONNECTIONS OF STEEL STRUCTURES

A treatment of the problem of elastic-plastic bifurcation of concentrically stiffened steel plates is presented. Finite element formulations are prepared employing both the initial stress and the modified Newton-Raphson techniques for the establishment of the elasto-plastic stress-distribution in plates under arbitrary planar loading and displacement boundary conditions. A tangent modulus theory for plastic buckling has been employed in conjunction with flow and deformation theories of plasticity. The Power Method for eigenvalue analysis has permitted accurate and economical predictions of the plastic buckling load and mode. An effective computer code has been developed for the estimation of the elastic-plastic buckling load of general, concentrically stiffened plates and their resulting buckled shapes. Several comparisons with other analytical solutions and experimental results are presented to ensure the appropriateness and practicality of the developed formulation and associated computer programs.; The formulations have been applied to obtain the column web capacity in symmetrical and non-symmetrical moment beam-to-column flange connections. A special type of beam-to-column web connection has been considered where the plastic stability of the flange plates, transmitting the minor axis beam flange force to the column flanges only, has been reviewed. A study on the inelastic interactive buckling of W-shape steel beams is also presented based on the concept of discontinuous yielding.; In the absence of a generalized theory for plastic buckling of plates, it becomes important to note the surprising consistency of the deformation theory for plastic buckling when employed in an incremental form to establish the planar non-proportional elasto-plastic stress distribution.