Vibration monitoring of a small concrete bridge using wavelet transforms on GPS data

Small concrete bridges are important roadway infrastructures in Brazil, where they serve as crucial links in the transportation network. Monitoring and maintenance of these bridges are essential for prolonging their lifetimes. The original work presented in this paper is based on the use of global positioning system (GPS) as a trustworthy tool for characterizing the dynamic behavior of small concrete bridges under normal operating conditions. The proposed inspection procedure includes the analysis of only two GPS signals with a method named the phase residual method, which is based on phase interferometry. Analytical methods, namely, the fast Fourier transform, continuous wavelet transform, and Chebyshev, are effective signal processing techniques for visualizing variations in system frequencies. The object of the study was the bridge over the Jaguari River, which is located in Brazil. The description of the dynamic behavior of the middle span of the concrete bridge was obtained by analyzing data obtained at a sampling frequency of 100 Hz collected for only 1 min. The results provided a clear picture of the energy distribution in the time–frequency plane during forced vibration: (1) the maximum deformation of the main span was pronounced at 3.5–8 mm; (2) the vibration frequency ranged between 4 and 8 Hz; and (3) the values obtained coincided with the values indicated by regular the monitoring sensors, such as accelerometers and transducers of displacements. The advantages of the use of GPS and the contribution to the geotechnical short- or long-term monitoring of road bridges are the use of a reference outside the structure, use under inclement weather conditions, and lack of disruption of traffic.