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Title |
Vibration Serviceability Evaluation of Footbridges Using Non-Contact Measurement Based on Eulerian Video Magnification
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Authors |
나상일(Sangil Na) ; 최웅규(Woonggyu Choi) ; 김승우(Seungwoo Kim) ; 박승희(Seunghee Park) |
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DOI |
https://doi.org/10.11112/jksmi.2025.29.5.124 |
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Keywords |
보도교 진동 평가; 오일러 비디오 증폭; 광학 흐름; 가속도; 고유진동수 Footbridge vibration evaluation; Eulerian video magnification; Optical flow; Acceleration; Natural frequency |
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Abstract |
Recent lightweight footbridges can experience excessive vibrations even under pedestrian loads. Conventional vibration measurements primarily rely on accelerometers, which require direct attachment to the structure. This approach is cumbersome, and multi-point measurements increase wiring complexity and costs. This study proposes a practical and efficient non-contact method for evaluating footbridge vibration serviceability using smartphone video and computer vision techniques. The recorded video was processed using Eulerian Video Magnification based on the avoidance frequency range suggested in domestic design guidelines, enabling visualization of subtle motions. The Lucas Kanade Pyramid Optical Flow algorithm was then applied to estimate time-series displacements, which were converted to real world units using the handrail as a reference length. Welch Power Spectrum Density analysis was performed to obtain the maximum vertical acceleration and natural frequency, and the damping ratio was calculated using logarithmic linear regression. Experiments on a 72 m single span footbridge clearly showed that the proposed method achieved an average error rate below 2.05% for maximum vertical acceleration and natural frequency compared to reference accelerometer data, with similar damping ratios.
The natural frequency of approximately 1.875 Hz matched the sensor measurements, confirming that the proposed non-contact video-based method accurately captures the essential dynamic behavior of footbridges.
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