Abstract
Ground-Based synthetic aperture radar (GBSAR) is a novel technique for monitoring surface deformation and structural vibrations due to its unique advantages: GBSAR can continually and simultaneously observe a large range of landscapes with a high spatiotemporal resolution. Using GBSAR under the fixed azimuth scanning mode to monitor vibrations is a promising way to monitor a bridge's structural health. Several GBSAR-based bridge vibration experiments have been conducted and verified; however, observation precision tests using high-rate global positioning system (GPS) data are rare, especially for the GAMMA portable radar interferometer II (GPRI-II). In addition, it is complicated to split high-frequency signals into valuable information and undesired noise. Considering these limitations, an on-site experiment using the GPRI-II and high-rate GPS receivers was conducted to evaluate the utility of the GPRI-II. Moreover, a denoising method based on the least-squares adjustment and a triangular chain is proposed under the assumption that the atmospheric phase delay can be eliminated between minuscule time intervals. In addition, an external comparative experiment between the GPRI-II and GPS receivers and an internal comparative experiment was performed to evaluate the effectiveness and reliability, respectively, of the proposed method. The results show that the GPRI-II observation accuracy for permanent scatterers reaches 5-6 millimeters. For the effectiveness of the proposed method, the precision improvement for distributed scatterers is more significant than that for permanent scatterers, and both the internal precision and the external precision have more conspicuous relationships with the deviation of the amplitude than with the coherence.
Highlights
B RIDGES, as vital components of any national infrastructure, play important roles in cities worldwide by supporting people’s lives and countries’ economies
Unlike the mean filtering approach, the proposed method leads to a result, which is similar to the global positioning system (GPS) time series and preserves the high-frequency signal
The differences were counted in three bins for both antennas on the two bridges, and the corresponding probability distribution diagrams are displayed in Figs. 13 and 14, in which the range is limited to between −50 and 50 mm
Summary
B RIDGES, as vital components of any national infrastructure, play important roles in cities worldwide by supporting people’s lives and countries’ economies. Noncontact equipment includes laser Doppler vibrometers (LDVs) [6], robotic total stations (RTSs) [7], ground-based synthetic aperture radar (GBSAR) [8], and high-speed cameras [9], and all of the installation (unlike that of contact equipment) is not complicated or dangerous because the sensors are located far from the structure These noncontact devices are applied in different situations and have their own advantages and disadvantages. ZHU et al.: MONITORING BRIDGE VIBRATIONS BASED ON GBSAR AND VALIDATION BY HIGH-RATE GPS MEASUREMENTS of dams [19], slopes [20]–[22], glaciers [23], [24], and structures [8], [25] according to its unique characteristics, namely, a high spatiotemporal resolution, the ability to acquire observations in real time, and high measuring accuracy. We analyze and discuss the results and draw our conclusions in Sections IV and V, respectively
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