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Remote Sens. 2018, 10(5), 770; https://doi.org/10.3390/rs10050770

Dynamic Monitoring and Vibration Analysis of Ancient Bridges by Ground-Based Microwave Interferometry and the ESMD Method

1
Key Laboratory for Urban Geomatics of National Administration of Surveying, Mapping and Geoinformation, Beijing Key Laboratory for Architectural Heritage Fine Reconstruction & Health Monitoring, Beijing University of Civil Engineering and Architecture, 1 Zhanlanguan Road, Beijing 100044, China
2
College of Surveying and Geo-informatics, Tongji University, 1239 Siping Road, Shanghai 200092, China
*
Authors to whom correspondence should be addressed.
Received: 21 March 2018 / Revised: 8 May 2018 / Accepted: 14 May 2018 / Published: 16 May 2018
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Abstract

In this paper, we propose to conduct a dynamic monitoring and vibration analysis of ancient bridges by means of ground-based microwave interferometry and the extreme-point symmetric mode decomposition (ESMD) method. Ground-based microwave interferometry, a novel non-contact technology with a high accuracy, is used to acquire dynamic time series displacements with environmental excitation factors and a transient load with a car, respectively. The ESMD method, a new alternative to the Hilbert-Huang transform (HHT), is adopted to conduct the instantaneous vibration analysis of Zhaozhou Bridge. Firstly, a series of intrinsic mode functions (IMFs) are obtained together with an optimal adaptive global mean (AGM) curve by using a mode symmetric about the maxima and minima points. Secondly, the instantaneous frequency of each IMF is obtained by the use of a direct interpolation algorithm, which can reconcile the conflict between the period and the frequency for the traditional time-frequency analysis methods. As a representative case, Zhaozhou Bridge, a well-known Chinese ancient bridge constructed more than 1400 years ago, is studied in detail. Four kinds of dynamic time series displacements—two of them acquired by considering only environmental excitation factors for the mid-span and 1/4-span points and the others obtained with the transient load of a car for the mid-span and 1/4-span points—are selected to pursue a comparison of the decomposed IMFs and the instantaneous frequencies to perform the instantaneous vibration analysis of Zhaozhou Bridge. By comparing the results obtained with HHT for the decomposed IMFs and the instantaneous frequencies, the results show that the proposed method has a powerful ability to evaluate the instantaneous dynamic response of ancient bridges. View Full-Text
Keywords: ground-based microwave interferometry; extreme-point symmetric mode decomposition (ESMD); time-frequency analysis; instantaneous frequency ground-based microwave interferometry; extreme-point symmetric mode decomposition (ESMD); time-frequency analysis; instantaneous frequency
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Liu, X.; Lu, Z.; Yang, W.; Huang, M.; Tong, X. Dynamic Monitoring and Vibration Analysis of Ancient Bridges by Ground-Based Microwave Interferometry and the ESMD Method. Remote Sens. 2018, 10, 770.

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