Abstract
This paper presents a practical framework for urban bridge damage detection and analysis by using three key techniques: terrestrial laser scanning (TLS), ground-based microwave interferometry, and permanent scatterer interferometry synthetic aperture radar (PS-InSAR). The proposed framework was tested on the Beishatan Bridge in Beijing, China. Firstly, a Digital Surface Model (DSM) of the lower surface of the bridge was constructed based on the point cloud generated by using TLS to obtain the potential damage area. Secondly, the dynamic time-series displacement of the potential damage area was acquired by ground-based microwave interferometry, and the Extreme-Point Symmetric Mode Decomposition (ESMD) method was applied to detect damages by the use of signal decomposition and instantaneous frequency calculation. Lastly, the PS-InSAR technique was applied to obtain the surface deformation around Beishatan Bridge by using COSMO-SkyMed images with a ground resolution of 3 m × 3 m, and finally, we analyzed the causes of bridge damage. The experimental results showed that the proposed framework can effectively obtain the potential damage area of the bridge by the DSM from the point cloud by TLS and further judge whether the bridge was damaged by the ESMD method, based on the time-series displacement data. The results also showed that the subway shield construction may be the reason for damage to Beishatan Bridge.
Highlights
As an important component of allowing the movement of vehicles over and around obstructions in cities, urban bridges support the dense flow of traffic and often are a part of a complex surrounding environment, influenced by subway construction crossing
The results demonstrate that the terrestrial laser scanning (TLS) technique is an effective technique to find out the potential damage area of the monitored bridge caused by differential subsidence, whether there are cracks in the bridge surface or not, which is a great advantage compared with the traditional point-wise surveying methods
To determine the safety status of urban bridges, this study proposed a practical framework to detect and analyze the damage of urban bridges by using TLS, ground-based microwave interferometry, and PS-InSAR
Summary
As an important component of allowing the movement of vehicles over and around obstructions in cities, urban bridges support the dense flow of traffic and often are a part of a complex surrounding environment, influenced by subway construction crossing. Typical experimental tests are usually carried out using piezoelectric accelerometers, fiber optic sensors, and strain and inductive gauges, which are quite accurate and reliable [6,7] These gauges need to be fixed in specific positions on the urban bridges on which they are used. The application of CP is restricted due to the requirement of a large number of cameras installation of fixed reflective points, a complicated control network layout, and massive image data processing [2,10] For these reasons, ground-based microwave interferometry is a good alternative technique, as it uses radar working at the Ku-band (12–18 GHz), which facilitates precise measurements. As a linear measurement technique for ground-based microwave interferometry, it is difficult to pinpoint the location of the damage to obtain accurate time-series displacement for urban bridges
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