MODELING AND ANALYSIS OF MASONRY BUILDING AGGREGATES SUBJECT TO VARIOUS DEGREES OF INTERCONNECTION

Most of Italian historical centers are characterized by the presence of interconnected unreinforced masonry (URM) structures, commonly referred as aggregate buildings, which have shown significant seismic vulnerability over time. These structures are generally composed of units with varying geometries and materials, which have been subjected to structural changes over the course of their lifespan. The uncertain degree of connection between the units makes modeling their seismic response challenging in the absence of specific guidelines. Traditional seismic modeling of URM aggregates often oversimplifies the matter by considering units as either separated or rigidly connected, which does not accurately reflect the real complexity of their dynamic behavior. Addressing this gap, the present study intends to understand the "aggregate effect" on individual unit response under varying degrees of interconnection. Using advanced 3D Finite Element numerical simulations, an URM aggregate building consisting of three similar three-story units was analyzed using the homogenized masonry modeling approach. The units were studied under three boundary conditions within the aggregate: isolated, fully connected and semi-connected by a degrading mortar interface simulating four different degrees of connection. The study focused on studying these models using non-linear static analyses followed by a quantitative seismic assessment according to the N2 method. The analyses were carried out using STKO, a framework for OpenSees which, in addition to providing an interface, allows the use of advanced built-in materials and elements.