Notional-Load Plastic-Hinge Method for Frame Design

The present paper discusses the use of second-order inelastic analysis for designing steel-frame structures. In particular, the elastic-plastic hinge method is discussed and its accuracy is examined. The elastic plastic-hinge analysis does not always represent accurately the inelastic behavior of a member, since it does not account for distributed plasticity and initial residual-stress effects. One way to account for these effects in the analysis is to apply a set of notional lateral loads that are computed based on the gravity loads acting on the stories of the frame. The performance of this analysis approach is compared with the results from conventional elastic plastic-hinge and refined plastic-zone solutions. The goal is to illustrate the acceptability of the notional-load plastic-hinge method for use in predicting the maximum strengths of steel frames and their members. Finally, the design implication of this approach is explained, and its extension for the analysis and design of multistory and multibay frames is discussed.