A phase-field approach for modeling plastic hinges in Euler–Bernoulli beams

The present paper deals with the structural analysis of framed structures made up of elasto-plastic material. The approach is formulated in the framework of the lumped plasticity models where the inelastic effects appear and evolve at specific sections where the ultimate states are attained. The proposed approach aims to regularize the sharp interface between the sound part of the beam and the section where inelastic strain develops. The goal is achieved by using the phase field model which in this formulation defines a smooth transition between the elastic and the plastic parts of the beam over a length , called in the literature hinge length. A key advantage of this approach is its capacity to model beams with intraelement multiple hinges. From the computational point of view, unlike traditional nonlinear finite element analysis (NFEM) of framed structures, where hinges are typically located at the ends of the elements, the proposed strategy effectively captures collapse mechanisms with plastic hinges distributed along the beam axis. This is accomplished without prior knowledge of the hinge positions or the need for a remeshing procedure.