SPREAD OF PLASTICITY - QUASI-PLASTIC-HINGE APPROACH

The paper describes a method of inelastic analysis for steel frames that provides the accuracy of distributed plasticity methods with the computational efficiency of elastic-plastic-hinge methods. It accounts for spread-of-plasticity effects without the need for through-section and lengthwise discretization of a beam-column element. This is accomplished through nonlinear equations for the force-strain relationships of the cross section that are calibrated to data from inelastic analyses and numerical integration of the cross-section model along the element length to obtain inelastic flexibility coefficients for the member. The flexibility coefficients are employed in generating an inelastic stiffness matrix in which geometric nonlinearity is also accounted for. The proposed model has been implemented and tested using several example problems known to be sensitive to spreading-plasticity effects.