Limit Analysis-Based Approach for the Assessment of Local Failures in Masonry Aggregates According to Italian Standards

A fast and reliable procedure for the assessment of masonry building aggregates is presented through a homemade limit analysis-based method. In Italy and many southern European countries, most of the historical city centers are characterized by masonry buildings clustered in aggregates. Their seismic assessment is fundamental for their preservation. Since in such kinds of constructions earthquakes typically trigger local failure mechanisms, the proposed limit analysis-based approach allows their identification and the evaluation of the corresponding collapse acceleration. Infinitely resistant hexahedron elements are used to discretize the structure. Dissipation occurs only at elements’ interfaces, meaning that static and kinematic problems coincide, being one the dual of the other. Since the kinematic approach is more straightforward, it is used to evaluate collapse loads, failure mechanisms, and interface plastic multipliers. In addition, internal actions on interfaces may be retrieved from the static dual problem. The procedure proposed evaluates the spectral acceleration and automatically provides safety checks as required by the Italian building code. The method is benchmarked on portions of real case studies, namely two buildings exhibiting high complexity in Piacenza, Italy.