橋は年数が経つと少しずつ劣化していきます。その安全性を保つためには、橋がどのように「たわむか（変位するか）」を知ることが重要です。
本研究では、橋に触れることなく、マーカレスで、地上に置いた小型レーダで橋のわずかな動きを高精度に測定する技術を開発しました。札幌市豊平橋を対象にした実験により、1ミリ未満の精度でたわみを計測できることを確認しています。
この技術は、低コストで持ち運びも可能なため、将来的には橋の安全点検をより効率的に行うための新しい方法として期待されています。
Yuta Izumi, Fathin Nurzaman, Sartika, Masato Komuro, Tomoki Kawarai “Dynamic Displacement Monitoring of Bridges using Dual Monostatic Ground-Based MIMO Radar Interferometry,” in IEEE Access, Early Access, Feb. 2026.
https://ieeexplore.ieee.org/document/11408134
Abstract
As bridges deteriorate over time, the need for effective bridge structural health monitoring (SHM) becomes increasingly critical. Dynamic displacement serves as a key indicator for identifying potential structural issues. This study presents a non-contact, marker-less, cost-effective, portable, and image-domain dynamic displacement estimation methodology using ground-based multiple-input multiple-output (GB-MIMO) radar interferometry for bridge SHM. A dual monostatic GB-MIMO radar configuration, combined with a practical photogrammetry-based geocoding approach was introduced to enable two-dimensional (2D) displacement vector estimation. The proposed framework was validated through controlled outdoor experiment as well as field deployment on a three-span steel box girder bridge, utilizing two off-the-shelf W-band MIMO radar units. Radar measurements captured vertical deflection responses induced by moving vehicle loads, with negligible horizontal displacement. Validation against a laser displacement meter (LDM) confirmed sub-millimeter displacement accuracy. Additionally, the extracted natural frequencies showed strong agreement with finite element method (FEM) based numerical analysis, demonstrating the system’s capability for accurate dynamic characterization of bridge structures.