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A Novel Approach for 3D-Structural Identification through Video Recording: Magnified Tracking

1
Institute of Structural Engineering, Department of Civil, Environmental and Geomatic Engineering, ETH Zürich, 8093 Zurich, Switzerland
2
Institute of Environmental Engineering, Department of Civil, Environmental and Geomatic Engineering, ETH Zürich, 8093 Zurich, Switzerland
*
Author to whom correspondence should be addressed.
This paper is an extended version of Harmanci, Y.E.; Gulan, U.; Holzner, M.; Chatzi, E. A Comparative Study on 2D and 3D Tracking of Vibration via Motion Magnified High-speed Videos. In Proceedings of the 7th World Conference on Structural Control and Monitoring, Qingdao, China, 22–25 July 2018.
Sensors 2019, 19(5), 1229; https://doi.org/10.3390/s19051229
Received: 12 February 2019 / Revised: 5 March 2019 / Accepted: 5 March 2019 / Published: 11 March 2019
(This article belongs to the Section Sensor Networks)
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Abstract

Advancements in optical imaging devices and computer vision algorithms allow the exploration of novel diagnostic techniques for use within engineering systems. A recent field of application lies in the adoption of such devices for non-contact vibrational response recordings of structures, allowing high spatial density measurements without the burden of heavy cabling associated with conventional technologies. This, however, is not a straightforward task due to the typically low-amplitude displacement response of structures under ambient operational conditions. A novel framework, namely Magnified Tracking (MT), is proposed herein to overcome this limitation through the synergistic use of two computer vision techniques. The recently proposed phase-based motion magnification (PBMM) framework, for amplifying motion in a video within a defined frequency band, is coupled with motion tracking by means of particle tracking velocimetry (PTV). An experimental campaign was conducted to validate a proof-of-concept, where the dynamic response of a shear frame was measured both by conventional sensors as well as a video camera setup, and cross-compared to prove the feasibility of the proposed non-contact approach. The methodology was explored both in 2D and 3D configurations, with PTV revealing a powerful tool for the measurement of perceptible motion. When MT is utilized for tracking “imperceptible” structural responses (i.e., below PTV sensitivity), via the use of PBMM around the resonant frequencies of the structure, the amplified motion reveals the operational deflection shapes, which are otherwise intractable. The modal results extracted from the magnified videos, using PTV, demonstrate MT to be a viable non-contact alternative for 3D modal identification with the benefit of a spatially dense measurement grid. View Full-Text
Keywords: vibration-based measurement; SHM; structural identification; motion magnification; particle tracking velocimetry vibration-based measurement; SHM; structural identification; motion magnification; particle tracking velocimetry
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Harmanci, Y.E.; Gülan, U.; Holzner, M.; Chatzi, E. A Novel Approach for 3D-Structural Identification through Video Recording: Magnified Tracking. Sensors 2019, 19, 1229.

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