Statistical analysis: a tool for understanding monitoring data

Monitoring data often need deep analysis in order to understand the real behaviour of a structure or a soil mass which may be overshadowed by unknown phenomena or boundary conditions. Temperature is one of the most common parameters which affect field measurements and create problems in data interpretation and use. One of the most powerful tool which can be used to perform these analyses is represented by statistical approach. The analysis starts from the knowledge of the mechanics of the considered phenomena and related physical assumptions in order to separate the contribution of the different components. Statistical techniques allow to identify the different contributions and to reduce the uncertainty of a system. Moreover, by means of a hierarchical multivariate detector (HMD) based on statistical control charts it is possible to analyze the behaviour of complex systems considering all the measuring instruments and their data in order to fix threshold values and to check the tendency of the system to change its status from a safety situation to a warning or alert one. This paper describes the statistical background of the approach with reference to a specific application on a stayed bridge.