LIBERATORE, DOMENICO1; ADDESSI, DANIELA2

1) Professor, “Sapienza” University of Rome, Dept. of Structural and Geotechnical Engineering, domenico.liberatore@uniroma1.it

2) Assistant Professor, “Sapienza” University of Rome, Dept. of Structural and Geotechnical Engineering, daniela.addessi@uniroma1.it

An equivalent frame model is proposed for the assessment of in-plane mechanisms of masonry walls. It consists of a 2-node force-based finite element (FE) with lumped plastic hinges. This FE formulation enables one to satisfactorily describe the static nonlinear response of masonry under loading conditions simulating seismic actions, within the framework of pushover analysis. The FE beam formulated on the basis of Timoshenko’s theory, consists of a central linear elastic element, two flexural hinges arranged in series at the ends and a shear link, whose behaviour is characterized by an elastic-perfectly plastic constitutive law. The hinge state is determined by means of a predictor-corrector method, where the predictor calculates the stress field of the element using the tangent flexibility matrix and the corrector consists of a return algorithm based on the Haar-Kármán principle, leading both to good convergence properties and to optimal characteristics of the solution.

Keywords: Masonry macroelement, Lumped plasticity, Haar-Kármán principle