LARGE DISPLACEMENT ELASTOPLASTIC ANALYSIS OF SEMIRIGID STEEL FRAMES

A mathematical programming approach for the large displacement analysis of elastoplastic plane frames with flexible, partial-strength beam-to-column connections is proposed. The incremental formulation is developed within the framework of a discrete model, piecewise linear yield surfaces and large displacement theory. It is based on the fundamental relations of equilibrium, compatibility and constitutive laws, all expressed in incremental form. The irreversible plasticity laws are used in a stepwise holonomic format. A feature of the final mathematical programming problem, known as a non-linear complementarity problem, is that the governing relations exhibit symmetry as a result of the use of fictitious quantities and non-linear residuals. The iterative predictor-corrector computational scheme adopted has the ability of tracing historically a sequence of plastic hinge activations and/or unloadings well beyond any critical point. Numerical examples are presented to illustrate and validate the accuracy of the approach