Numerical model upgrading of ancient bell towers monitored with a wired sensors network

In this work, the opportunities provided by dynamic identification techniques for non-destructive evaluation of heritage structures are discussed with a focus on different bell towers, located in the Ferrara Province (Italy). All of them were stricken by a long seismic sequence (Emilia Romagna, North-East of Italy, May-June 2012 seismic sequence) and they are investigated in detail to have an insight into their dynamic behaviour. Furthermore, the experimental investigations and the operational modal analysis results are presented and they are useful for defining the Finite Element (FE) models of the towers within a continuum approach. The monitoring system consists of several sensors properly connected. The positioning of the instrumentation has been conditioned by many operative problems due to the limited accessibility of the structures, both related to the main access and to reaching the top. However, it has been possible to identify with a certain confidence the first three frequencies of the towers and their corresponding mode shapes. The results carried out after the FE updating procedure may be considered very good. The material data values estimated in this way will constitute an important reference for the evaluation of the state of the building.