Dual Frequency Real Aperture Radar Monitoring of a Railway Bridge

Different studies demonstrated that the monitoring of the vibrational characteristics of bridges can be fostered using real aperture radar interferometers. Commercial systems operating at Ku band have been made available to the users since the last two decades. Analyzing the phase of the radar signal, which is related to the displacement of the phase center of each radar range cell, the radar bin, a description of the vibrating mode of civil structures as bridges, towers, and tall buildings can be achieved. Displacement time series of different parts of the monitored structure can be processed to retrieve the frequency and amplitude of the vibrational modes to evaluate the dynamic behavior of the structure. Systems operating at higher frequencies and using advanced radar techniques have been recently proposed. Here we report the use of two different radar systems, working at Ku and K band respectively, to compare their performance, when used to monitor a railway bridge located in Spain. The radar acquisitions were realized by positioning the radar systems at different locations, to detect multiple vibrational modes. The results show a quite good agreement with accelerometer acquisitions, demonstrating the suitability of radar interferometers to measure bridge vibrations.