A Possible Interpretation of Data acquired from Monitoring Systems

In the last recent years, structural monitoring has acquired an increasing importance in the diagnosis and control of buildings, especially for historical buildings whose preservation is essential to the safeguard of cultural heritage. The aim of this study is to introduce a standardized approach for the analysis of the large amount of 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 connected with the natural forces acting on the building and an unknown one linked to the variation in 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 type of analysis has been applied to the data obtained from the monitoring system of a significant Italian monument: the Asinelli and the Garisenda towers of Bologna.