8. Reference Quantities and Values for a Possible Interpretation of the Data Acquired from Monitoring System of Historical Buildings

Preserving historic buildings is essential in the safeguard of the cultural heritage of any country. The need to carry out structural analyses by means of non-destructive methods has made structural monitoring ever more widespread in the diagnosis and control of historic buildings. The aim of this study is to introduce a standardized approach for the analysis of the data acquired from a monitoring system of historic buildings. This approach is based on the definition of specific reference quantities (extrapolated from the recorded time series) able to characterize the main features of the structural response and the preliminary identification of the order of magnitudes of these quantities. It is assumed that the recorded time series can be decomposed into two components: a periodical one depending on with the natural forces acting on the building and an unknown one related to the variation of the state of the structure. Exploiting the properties of periodic functions, one may identify these reference quantities, which are based on the year and the day variability and allow to monitor the evolution of the phenomena under observation. These reference quantities may be collected in a database and may become fundamental for comparing the response of similar buildings. This approach has been applied to the data obtained from the monitoring systems of two important Italian monuments: the Cathedral of Modena and the “Two Towers” of Bologna.