FMCW Radar for Noncontact Bridge Structure Displacement Estimation

The displacement on the bridge structure is an essential parameter in identifying the bridge structure’s health. The noncontact measurement method is preferable in practice, and the radar system is potentially employed for developing displacement measurement technology. Frequency-modulated continuous wave (FMCW) radar has a feature for detecting the target location. However, estimating the small displacement in the bridge structure requires extensive bandwidth to reach the proper resolution. The problem of obtaining the required resolution, and adopting the decrease in accuracy due to several possible radar placements during measurement are addressed in this article. The concept of bridge displacement measurement using a modified FMCW radar system is proposed. Phase information extraction is employed to reach the displacement detection resolution, and the radar elevation detection based on an inclinometer is equipped in the proposed radar system. The simulation and laboratory experiments were conducted by implementing the proposed radar system for detecting the displacement in the bridge model. The experiment results confirm that the proposed FMCW radar was able to estimate the bridge displacement and overcome the decreasing accuracy due to the radar elevation. The multipoint detection technique is also developed in the proposed radar and is capable to capture the displacement profile over the bridge span. The proposed FMCW system is then recommended as a radar system in developing a noncontact method for bridge displacement measurement and monitoring.