Analysis of localization in frame members with plastic hinges

摘要

This paper proposes a general criterion of localization for frame members. A frame member is assumed to be the assemblage of an elastic beam-column and two plastic hinges at the ends of the member. Each plastic hinge presents plastic softening behavior under bending and axial forces. In this case, localization refers to the concentration of plastic rotation within a plastic hinge while the other one unloads. The localization criterion is obtained front the analysis of the problem that defines the plastic multipliers of the hinges as a function of the member displacements rate. Then, a simple uniqueness condition is derived for this problem. If the uniqueness condition is not verified, bifurcated solutions with localization are possible, hence the localization criterion. This criterion is applied in three particular cases for which analytical solutions are obtained and discussed. Finally the numerical implications of the localization criterion are discussed. (C) 2004 Elsevier Ltd. All rights reserved.