SPREAD OF PLASTICITY - QUASI-PLASTIC-HINGE APPROACH

The paper describes a method of inelastic analysis for steel frames th at provides the accuracy of distributed plasticity methods with the co mputational efficiency of elastic-plastic-hinge methods. It accounts f or spread-of-plasticity effects without the need for through-section a nd lengthwise discretization of a beam-column element. This is accompl ished through nonlinear equations for the force-strain relationships o f the cross section that are calibrated to data from inelastic analyse s and numerical integration of the cross-section model along the eleme nt 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 exa mple problems known to be sensitive to spreading-plasticity effects.