The present paper discusses the results of the identification procedure applied to the building of the Municipality of Castellaneta, a town in the province of Taranto (Puglia, Italy). The case study has been chosen for its structural complexity; indeed, the building has been built in two successive phases, block A built between 1955 and 1957, and block B, for completion, presumably built between the years 1960 and 1961.

Block A constitutes the main building and represents the original nucleus. The structure was subsequently subject to structural interventions, that are the replacing of some load-bearing walls with steel beams. The building constituting block B, joined to the original body of the building, has a structure in load-bearing masonry, while the floors, more recently built, are also in brick-concrete, but with pre-cast prestressed joists.

The dynamic response of the building was assessed through the OMA (Operational Modal Analysis) identification technique which allows you to determine the properties of the structure in real operating conditions, without the need to interrupt the activities inside the structure itself. The structural excitement, therefore, is due only to the environmental condition. A 3D model was defined in SAP2000; the results obtained from the finite element model were subsequently compared with those obtained from the experimental model. After a model updating, a good correlation has been obtained between the FE model dynamic behavior and the experimental identified one