'HYBRID' FULL MODELS FOR SEISMIC ASSESSMENT OF MASONRY AGGREGATES THROUGH PUSHOVER ANALYSIS

Most of the historical city centres in Southern Europe are made up of masonry buildings clustered in aggregate, which are a result of the urban tissue transformation over time. Recent earthquakes have shown their high vulnerability because buildings were built without any anti-seismic criterion, relying on simple rules of thumbs. Since the seismic behaviour of masonry aggregates cannot be a priori predicted - because of complex geometries, presence of materials having different behaviours and interactions among adjacent buildings - accurate analyses, such as pushover analyses, shall be performed. Masonry aggregates are typically characterized by the presence of different structural typologies, thus pushover analyses are generally performed on partial models, representing significant portions of the whole aggregate. The critical point in this type of analysis is the identification of the minimum length of the portions of the neighbouring walls that actually contribute to the extra-redundancy of the structural system, which cannot be taken into account within partial models. Hence the idea to consider “hybrid” full models, in which the material behaviour is assumed non-linear only for the portion subject of investigation, while it is assumed linear elastic for the context. This contribution shows the results - part of a wider work - obtained by means of pushover analyses performed for the ex-monastery of Santa Maria della Pace in Piacenza, Italy, on full and partial models of the entire aggregate with different material modelling assumptions, and the model that best represents the actual behaviour of masonry aggregates is proposed.