Seismic Response of Masonry Aggregate Buildings by Explicit Modelling Different Interconnection Degrees

Unreinforced aggregate masonry buildings constitute a significant portion of Mediterranean heritage and are characterized by construction processes that evolved alongside urban development. This evolution often resulted in the expansion and transformation of original structures into large buildings composed of multiple units with heterogeneous characteristics in materials, geometry, and boundary conditions. Moreover, phased construction processes introduced uncertainty regarding the degree of inter-unit connection. These variations critically influence their structural behavior during earthquakes, increasing their vulnerability. The assessment of these structures presents two primary challenges derived from the large scale of the problem: achieving accurate behavior representation through modeling assumptions and optimizing analysis speed without compromising accuracy. This study aims to present modelling strategies based on the OpenSees framework, oriented to balance these challenges. The main guidelines focus on material properties definition, and the modeling of interactions between units, slab deformability, and lintel behavior. The strategies are based on the use of 2D shell elements and the homogenized material approach, applied to an elementary aggregate building designed to study the “aggregate effect.” Validation of these strategies and studies on different boundary conditions using static and dynamic non-linear analyses will be discussed, focusing on model performance.