## 2 Background  
### Structural Health Monitoring  
The report LA-13975-MS published by Los Alamos National Laboratory suggests three prime guidelines to describe a methodology for SHM: structural condition examination, experimental setup and SHM system characteristics, and feature extraction [10]. The structural condition examination is necessary to identify the causes of the structural monitoring inquiry. Then, it is possible to determine the relevant structural parameters for testing and the ambient and operational surroundings of the civil structure. The experimental setup and SHM system characteristics include the measurements provided; testing methods; and sensor quantity, arrangement, and features. Moreover, data acquisition, storage, and transmission systems are essential components selected according to sampling frequency, data size, and environmental conditions. Finally, the feature extraction is carried out through the information already recorded in order to perform data processing, and consequently, compute system identification and damage detection algorithms regarding the structural parameters at issue. Vibration-based SHM comprehends system identification as one of the most relevant approaches for smart infrastructure. In order to perform a system identification approach, digital signal processing techniques play an essential part in information from sensors. Thus, the more accurate and efficient the signal processing techniques in the system identification process, the more reliable the structural health condition assessment of the civil structure. The success of vibration-based SHM strategies relies on embracing digital signal processing and structural health condition assessments to preserve civil engineering structures from natural and man-made hazards and improve community resilience [11; 12]. Historically, aerospace, civil, and mechanical engineering have been considered the most progressive work fields regarding SHM [1]. SHM strategies require a critical component to reach highly-accurate outcomes: technological devices with specific hardware and software characteristics for studying the response of the structure and its operational ambiance. The SHM framework enables thorough tracking of the response of a structure over its lifetime, recording permanently or periodically information about structural properties from monitoring systems [3]. In this regard, SHM systems comprise assemblies of particular elements; each SHM system component includes specific features and accomplishes particular tasks. However, there is a group of conventional but significant characteristics required for every monitoring system: power consumption, programming assignments, signal acquisition and conditioning capabilities, data storage and processing capabilities, a communication protocol, and numerical computing techniques, among others. The deterioration detection of civil structures by SHM strategies empowers the decision-making of further structural interventions on time. Regarding traditional SHM implementations, the Bill Emerson Memorial Bridge, located in Missouri, United States, is a 1210-m cable-stayed structure and carries a wired SHM monitoring system (placed in 2005) made up of 84 seismic accelerometers for evaluating the performance and checking design parameters, and additionally, providing information for future design evaluation [13]. In addition, the Tsing Ma Bridge is a 2132-m suspension bridge located in Hong Kong, China, holding an SHM system (installed in 1997) accompanied by a high-density arrangement of 110 dynamic strain wired gauges for the evaluation of internal forces at bridge cross-sections and bearings [14]. Seeking to reshape SHM strategies in a more attractive, affordable, and efficient way, WSNs have been used for SHM development due to their minor costs, rapid experimental setups, and more accurate computational techniques.