Seismic assessment of masonry aggregates: A NURBS-based limit analysis computational tool

Masonry structures represent one of the most common worldwide structural typologies for buildings. To date, many historical towns and villages in Italy are built from aggregates of masonry buildings, in which each architectural unit interacts with others forming a complex structural system. Local failure mechanisms are particularly important for the assessment of the safety level of masonry buildings and, especially, of aggregates: recent seismic events have provided evidence that masonry buildings are particularly vulnerable to out-of-plane actions, triggering a wide number of local collapse mechanisms. For this reason, this contribution proposes a new fast computational tool for the automated seismic assessment of local failure mechanisms in masonry aggregates through limit analysis. The proposed tool is based on the NURBS geometric description of the aggregate, which is the common output of many free form modelers. This peculiarity makes the tool easily interfaced with CAD design environments and requires no advanced computational skills to the user. The historical center of Arsita (Italy), a beautiful example of masonry aggregate, which was hit by the 2009 L'Aquila earthquake, is analyzed as a case study and the results are used to validate the proposed tool.