Second-Order Plastic Hinge Analysis

Abstract

During the past 20 years, numerous analytical models have been developed for second-order inelastic analysis of steel frames. In general, these models may be categorized into two main types: (1) plastic zone and (2) plastic hinge. The plastic-zone model follows explicitly the gradual spread of yielding throughout the volume of the structure. Plastification in the members is modeled by discretization of members into several beam-column elements and subdivision of the cross sections into many “fibers” [8.1–8.3]. The effects of residual stresses, geometric imperfections, and material strain hardening can all be accounted for in a plastic-zone analysis model. Because of the refined discretization of the members and their cross sections, the plastic-zone analysis can accurately predict the inelastic response of the structure, and it is generally considered an “exact” method of analysis. However, this type of analysis is too computationally intensive for general design use, and because of its complexity and cost, it has not yet found application in ordinary practice. Even if such analysis methods should become generally available and reliable, a more efficient procedure to assess the structural performance and failure modes of a system would be useful. Plastic-hinge-based methods of analysis hold the promise to fulfill these requirements.