Experimental Study on the Influence of Environmental Variables on the Dynamic Monitoring of Full-Scale Structures

As the field of Structural Health Monitoring (SHM) continues to advance, the influence of environmental variables on the dynamic response of structures has become increasingly significant. Understanding the impact of environmental factors, particularly temperature, on the dynamic behaviour of civil structures is crucial in Vibration-Based Structural Health Monitoring (VB-SHM). In fact, in most cases the structural diagnostic features are influenced by external environment which causes fluctuations that can be confused with the appearance of damage, or in the worst case, hide it. Therefore, accurate diagnostic techniques are essential to distinguish between normal environmental variations and changes due to structural damage, thereby reducing the occurrence of false positives and false negatives, which can result in significant waste of time and resources. Environmental factors can affect both the mass and the stiffness of the system; precipitations such as snow or rain could be seen as a mass addition to the system, which could last for days, until the liquid stored in the cavities or porosities of the materials dries completely. While variations in temperature could affect stiffness, for example due to the effect of freezing which tends to stiffen the body. Predicting the effect that these factors have on the structure is a key aspect and it is not trivial. The existing literature identifies various relationships between environmental variables and the dynamic behaviour of structures, with these relationships often varying according to the type of structure. These trends can certainly depend on the structural scheme and the material, but also on a series of other aspects. This paper shows some relationships experimentally found on very simple systems characterized by different materials, in order to better understand these findings respect to data from real structures to identify analogies. The study highlights the importance of accounting for environmental variations to improve the accuracy and effectiveness of SHM in preserving structural integrity.