The vulnerability assessment of existing masonry buildings is a largely investigated research topic with some aspects still to be faced. In historic towns, masonry buildings are aggregated and together confined, and their final appearance is derived from interventions and additions during their lives in different times and with different masonry textures or different construction materials. Demolitions and reconstructions of some parts were frequent, with the difficulty of now understanding the effectiveness of the mutual constraints. The seismic assessment of a case study of a 175-year-old building complex in Udine (Italy) provides an opportunity to use the results of ambient vibration tests to face the problem of modelling aggregate buildings for their seismic assessment. The “Padiglione Lodi” building complex was built in 1847 and extended and renovated several times afterwards. It was built mostly using URM with limited use of reinforced concrete. It consists of a main building and three wings (western, central and eastern). The inspections, experimental survey and analysis of the available documentation are used to suitably calibrate a Finite Element Model of the whole complex. Moreover, this allows the singling out of the central wing, as the unit needs more careful investigation. Non-destructive dynamic testing is then applied to the central wing in order to further validate the model and improve the knowledge of the interaction of the unit with the rest of the building. General remarks on the effective application of non-destructive dynamic analysis in conjunction with other methods to the seismic assessment of large URM building complexes are drawn.
