APPLICATION OF A GENERAL PURPOSE DISTINCT ELEMENT MODEL (DEM) FOR THE SEISMIC VULNERABILITY PREDICTION OF MASONRY AGGREGATES

Masonry aggregates are an important class of existing masonry structures. They can be seen as assemblages of several structural units that are independent of the viewpoint of the intended use but that are structurally connected one each other. Clusters are large and complex structures involving several adjacent structural units with different heights, number of stories, and inter-storey heights, erected in continuity one to each other, making it rather difficult to distinguish the independent units and to identify a global behavior of the whole construction. The authors have provided a novel limit analysis method to discretize a masonry pagoda through infinite resistant hexahedrons in some recent papers. For the vulnerability analysis of aggregates, the paper extends this assumption to a no-tension material. Under such assumptions, considering a generic portion of an aggregate, it is here discretized by means of hexahedron (Hexa8) elements. The material inside each element is supposed infinitely resistant and all the internal plastic dissipation of the mechanical system is assumed to occur exclusively at the interfaces between adjoining elements. Two aggregates located in Arsita, Italy are chosen to benchmark the code. They are “La Vecchia Forestale” and “Church of Santa Vittoria”. This research assumes that the tensile strength of the masonry material decreases gradually from a very high value to 0 (no-tension material), observes the change of the collapse mechanisms of the masonry aggregates, and deduces the associated failure mechanism. The approach shows that when the tensile strength is high, the collapse acceleration is unrealistically large. When the tensile strength of the material is reduced to a small value (close to the no-tension material), the overturning mechanism is most easily seen.