Structural Health Monitoring in Construction Using Frequency Selective Surface Sensor
Structural Health Monitoring; Frequency Selective Surface; Relative Humidity Sensor
Due to the development of civil construction, there is a greater need for methods to indicate failures and damages of various kinds that may compromise the functionality of buildings. Within this aspect, the concept of Structural Health Monitoring (SHM) is used to define the use of technologies in order to establish assessments that enable the diagnosis of the conditions of a structure. There are technologies available for this purpose, such as optical, resistive and mechanical wave based sensors, however, they present difficulties regarding complexity and cost. Thus, the main objective of this work is to present a preliminary study of the use of Frequency Selective Surface (FSS) in the development of a transmission coefficient - based relative humidity sensor system, applied to concrete structures. Thus enabling a measurement in free space (noninvasive) and with less complexity than current methods. For this, it is necessary to understand the behavior of the electrical permittivity of the medium and the relationship between this and the resonant frequency of the FSS. Therefore, the electrical allowances of various materials used in civil construction were analyzed. Next, two distinct FSSs were designed and their frequency responses measured for various relative humidity levels of commercial concrete blocks. The results are in good agreement with the behavior discussed in the literature regarding central frequency displacement, and it is verified that it is possible to determine a direct correlation between the frequency variation and the relative humidity level for the chosen study object.