Displacement Monitoring and Health Evaluation of Two Bridges Using Sentinel-1 SAR Images

Abstract

Displacement monitoring of large bridges is an important source of information concerning their health state. In this paper, a procedure based on satellite Persistent Scatterer Interferometry (PSI) data is presented to assess bridge health. The proposed approach periodically assesses the displacements of a bridge in order to detect abnormal displacements at any position of the bridge. To demonstrate its performances, the displacement characteristics of two bridges, the Nanjing-Dashengguan High-speed Railway Bridge (NDHRB, 1272 m long) and the Nanjing-Yangtze River Bridge (NYRB, 1576-m long), are studied. For this purpose, two independent Sentinel-1 SAR datasets were used, covering a two-year period with 75 and 66 images, respectively, providing very similar results. During the observed period, the two bridges underwent no actual displacements: thermal dilation displacements were dominant. For NDHRB, the total thermal dilation parameter from the PSI analysis was computed using the two different datasets; the difference of the two computations was 0.09 mm/°C, which, assuming a temperature variation of 30 °C, corresponds to a discrepancy of 2.7 mm over the total bridge length. From the total thermal dilation parameters, the coefficients of thermal expansion (CTE) were calculated, which were 11.26 × 10−6/°C and 11.19 × 10−6/°C, respectively. These values match the bridge metal properties. For NYRB, the estimated CTE was 10.46 × 10−6/°C, which also matches the bridge metal properties (11.26 × 10−6/°C). Based on a statistical analysis of the PSI topographic errors of NDHRB, pixels on the bridge deck were selected, and displacement models covering the entire NDHRB were established using the two track datasets; the model was validated on the six piers with an absolute mean error of 0.25 mm/°C. Finally, the health state of NDHRB was evaluated with four more images using the estimated models, and no abnormal displacements were found.

Extended D-TomoSAR Displacement Monitoring for Nanjing (China) City Built Structure Using High-Resolution TerraSAR/TanDEM-X and Cosmo SkyMed SAR Data

“…Generally, all the points belonging to the same part of the bridge overlaid on Piers 4 to 10 move with a uniform and stable trend, primarily with velocity values in the range of -2.0 mm/yr to +2.0 mm/yr in the LOS direction of TSX/TDX and CSK SAR data. Consistent with Sentinel-1 results [23], no PSs remained in two SAR datasets using the temporal coherence threshold for the west-side section of Pier 4 based on the reference point overlaid on middle Pier 7, probably due to the different architecture or applied materials, indicating a structural motion heterogeneity compared with the observed bridge section. Small sinking trends in the LOS direction of two datasets, with values approximately of -2 mm/yr were also detected on the top two arches (particularly in the TSX/TDX result).…”

“…The 3-dimensional spatial distribution of PS points overlaid on the architecture is evident, resulting in the observed topology of double-arches ( Figure 7), particularly in the TSX/TDX results. It is clear that high-resolution SAR data are beneficial to monitor infrastructure at pinpoint anomalies in structural motion owing to the enhanced PS detected overlaid on the infrastructure; for instance 16,549 PSs of TSX/TDX in this study versus approximately 900 PSs of Sentinel-1 [23]. Generally, all the points belonging to the same part of the bridge overlaid on Piers 4 to 10 move with a uniform and stable trend, primarily with velocity values in the range of -2.0 mm/yr to +2.0 mm/yr in the LOS direction of TSX/TDX and CSK SAR data.…”

“…Although traditional methods are robust and precise based on limited observations through manual leveling or sets of mounted sensors, however, the collected point-like information has the disadvantage of providing incomplete motion information. Consequently, in recent years, spaceborne MT-InSAR technologies are increasingly being used to monitor structural health (e.g., bridges [21][22][23][24]), in particular owing to the availability of high-resolution SAR datasets.…”

Diagnosing Subsidence Geohazard at Beijing Capital International Airport, from High-Resolution SAR Interferometry

“…Monitoring and controlling the subsidence of runways are of great significant to ensure the safe operation of the whole airport and avoid the potential extensive loss of life and property.During the last three decades, interferometric synthetic aperture radar (InSAR) technology has developed into a powerful tool, providing high-resolution, day-and-night, weather-independent wide-coverage and high-accuracy measurements of the earth surface [6]. It has been widely used in various applications, such as the displacements monitoring of city subsidence [7][8][9][10][11][12], important infrastructures [13][14][15][16] and landslides geohazards [17][18][19][20][21]. Compared to traditional geodetic measuring methods-e.g., leveling and global positioning system (GPS)-InSAR measurements do not need any on-site installation and power supply, thus they will not have any impact on the regular operation of the airport.…”

Editorial for the Special Issue “Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR Tomography”

“…The most original part of this work includes the estimation of the atmospheric phase component using stable areas located in the vicinity of the monitoring area. In reference [13], the observations coming from PSI are used to contribute to the assessment of the health state of two bridges. The use of PSI to study the long-term land deformation patterns in earthquake-prone areas is addressed in reference [14].…”