Micro-displacement Measurement of High-Speed Railway Bridge Based on Vector Network Analyzer

The efficient and accurate monitoring means of high-speed railway bridge is vital important to maintain the safe operation of high-speed railway. In this paper, a ground-based SFCW interferometry radar system based on vector network analyzer (VNA) is built. The control computer is connected to the VNA through a LAN port to remotely control the VNA to transmit and receive stepped frequency continuous wave (SFCW) signals through two standard gain horn antennas. The experiment is carried out on a 32m simply supported box girder of the Yancheng-Nantong high-speed railway in Nantong City, China. During the experiment, the high-speed railway inspection vehicle was used as the dynamic load and accelerated step by step from 300km/h to 385km/h. The radar system accurately measured the dynamic deflection of the bridge at different speeds and calculated dynamic factor through signal processing. The results show that the simulation results are consistent with the measured results which proves the accuracy and effectiveness of ground-based SFCW interferometry radar in the application of monitoring high-speed railway bridge.