A Seismic Assessment Approach for Historical Masonry Aggregates

The seismic assessment of historical masonry aggregates is particularly challenging as their present configuration typically reflects a complex construction history involving geometrical irregularities, heterogeneous structural systems, and mechanical interaction among adjacent buildings. In this context, an accurate reconstruction of the three-dimensional geometry of the aggregate is a fundamental step, since differences in height, wall configuration, floor levels, openings, and structural continuity may directly influence the global dynamic behavior. This study investigates the San Filippo Neri historical masonry aggregate through an integrated geometrical and structural modelling strategy. The geometry of the aggregate is reconstructed from the available architectural and survey documentation, including plans, sections, elevations, and photographic information, with particular attention to wall thickness variations, openings, horizontal structures, roofs, and masonry vaults. The reconstructed geometry then serves as the basis for a three-dimensional finite element model of the entire aggregate. Global modal analysis is then performed to identify the portions of the block which exhibit a distinguishable dynamic behavior. Two selected portions are subsequently analyzed independently, and their modal properties are compared with those obtained from the full aggregate model. Good agreement is found in terms of dominant vibration periods and mode shapes, supporting their interpretation as approximately independent structural units. A representative regular building located within one of these portions, Palazzo Jenca, is then modeled through the equivalent-frame approach and subjected to nonlinear static analysis. The N2 pushover procedure is used to derive a structure-specific behavior factor, which is subsequently employed in the linear dynamic assessment of the complete aggregate. The results highlight the close relationship between geometrical configuration and dynamic interaction within historical building aggregates. They further show that geometrical reconstruction and global modal behavior can jointly provide a mechanically informed basis for defining structural units in seismic assessment.