Seismic vulnerability of historical structures with the discrete element method

Abstract

It is widely recognized that historical structures represent a cultural heritage which should be preserved and transmitted to future generations. In several countries, and particularly, in the Mediterranean area, where a large number of important monuments are exposed to seismic hazard, there is a growing interest for the problem of strengthening such structures in order to reduce their seismic vulnerability, while preserving their original architectural integrity. However the seismic vulnerability assessment of historical block structures is still a challenging task. In this work, after having explored the potentials and limitations of the Discrete Element Method for this type of problem, a new joint model for the quasistatic analysis of block structures is proposed. It accounts for (a) the non coplanarity of the contact surfaces, and (b) friction softening. The new model allowed a more accurate prediction of the inplane failure load and corresponding failure mechanism of opus quadratum walls (walls made of regular squared blocks without mortar). In particular it predicts the development of progressive internal displacements, and the formation of localized sliding band as observed in the experimental models. Such results confirm that even apparently negligible joint imperfections should not be ignored since they may cause significant modifications in the response of a block structure subjected to gravity and lateral loading.