ABSTRACT
The implementation of infrastructure structural health monitoring for bridges is crucial in thoroughly evaluating their condition and maintaining their structural robustness. Recently, novel technologies have been introduced for both static and dynamic evaluation, opening up exceptional opportunities in the fields of risk management and structural assessment. Notably, microwave radar sensors have been effectively utilized for the continuous surveillance of dynamic and static displacements in bridges via aerial deformation measurement techniques. However, a primary challenge for microwave interferometry arises from its inherent linear measurement nature, making it challenging to precisely locate damage and derive accurate displacement time-series for bridges. Furthermore, it is worth noting that vertical displacements typically hold more significance than horizontal displacements in the dynamic monitoring of bridges. Regrettably, microwave radar interferometry can yield only the line-of-sight (LOS) displacement of a monitored bridge. In this study, our primary objective is the remote surveillance of dynamic displacement responses in bridges using a polarimetric radar system. To achieve this, we employ various methodologies to surmount the inherent limitations of this technique. Further, we discuss the results obtained from our monitoring of a long-span metallic railway bridge and a reinforced concrete Shinkansen bridge. The ultimate goal of this research is to generate more comprehensive and precise data for bridge health monitoring through the use of a polarimetric sensor. As part of our approach, we conducted a polarimetric analysis to detect reflections from the deck of the bridges. Furthermore, details relating to the polarization orientation angle and the local incidence angle were processed under the acquisition geometry to compute the radar look angle. As a result, we were able to easily convert the bridge deformation fields in the vertical direction using the slant range distances. The maximum transient vertical deformation corresponding to the LOS deformation was also transformed while a train traversed the bridge
