A MODIFIED STIFFNESS METHOD FOR PLASTIC ANALYSIS OF STEEL FRAMES

A simple and practical model is proposed for analysis of the second-or der inelastic behaviour of rigid frames. The method is based on a phen omenological model for representing the degradation in the stiffness o f beam-column members due to distributed yielding. It is found that th e conventional simple plastic hinge method tends to overestimate the l imit load of rigid frames when the axial loads of columns are large, i n the sequential loading condition. The load-deflection response predi cted by the proposed method is smooth and close to that obtained by mo re refined inelastic analysis methods and experimental results.