Radar-based multipoint displacement measurements of a 1200-m-long suspension bridge.

Structural displacement monitoring remains a challenging problem, especially for long-span bridges. A ground-based microwave interferometric radar system was developed and used to obtain multipoint displacement measurements of a suspension bridge with a main span of 1200 m. First, a microwave interferometric radar system with the merits of low price, straightforward usage, and good stability and robustness was developed. The phase was obtained by performing fast Fourier transform (FFT) of the in-phase/quadrature signals and calculating the displacement according to the phase interference. Second, the radar system was used in field tests of a long-span suspension bridge, including static, ambient vibration, and moving load tests. Multipoint displacements of the bridge girder, tower, and cables were obtained, and simultaneous measurements of the multipoint displacement influence lines of the bridge girder were performed. A method that uses three reference points to measure the bridge girder displacement was proposed. Good agreements between the results from the developed radar system and those from traditional sensors, including connecting pipes and total stations, demonstrated the excellent performance of the proposed method for remote multipoint displacement measurements of long-span bridges. [ABSTRACT FROM AUTHOR]