Second‐Order Inelastic Analysis Methods for Steel‐Frame Design

Abstract

Two simplified methods for second‐order inelastic analysis of steel frames, termed the modified plastic‐hinge and the beam‐column strength approaches, are presented. These analysis models are comparable to elastic‐plastic‐hinge analysis in efficiency, and yet, they alleviate the problems associated with overprediction of stiffness and strength by the usual elastic‐plastic‐hinge analysis methods. The modified plastic‐hinge method is based on simple modifications to the elastic‐plastic‐hinge model, which account for the degradation in stiffness as the cross‐section strength is approached at critical locations along the member length. The beam‐column strength method is similar to the modified plastic‐hinge approach, except that in this model, equations for the strength of the overall member are employed rather than expressions for the cross‐section strength. The performance of these analysis models is contrasted with results from elastie‐plastic‐hinge and refined plastic‐zone analysis solutions as well as results from experimental tests. Recommendations are provided with regard to the acceptability of simplified analysis models for use in predicting inelastic load‐deflection behavior and maximum strength.