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Estimation of full-field dynamic strains from digital video measurements of output‐only beam structures by video motion processing and modal superposition

Yang, Yongchao and Jung, Hwee‐Kwon and Dorn, Charles and Park, Gyuhae and Farrar, Charles and Mascareñas, David (2019) Estimation of full-field dynamic strains from digital video measurements of output‐only beam structures by video motion processing and modal superposition. Structural Control and Health Monitoring, 26 (10). Art. No. e2408. ISSN 1545-2255. https://resolver.caltech.edu/CaltechAUTHORS:20191010-092202891

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Abstract

Strain is an essential quantity to characterize local structural behaviors and directly correlates with structural damage initiation and development that is within local regions. Strain measurement at high spatial resolution (density) locations is thus required to characterize local structural behaviors and detect potential local damage. Traditional contact‐type strain gauges are mostly discrete point‐wise sensors that can only be placed in a limited number of positions. Distributed optical fiber sensing techniques can measure strains at spatially dense measurement points, but their instrumentation is a time‐ and labor‐intensive process associated with the issue of the fragility of fibers. Noncontact optical measurement techniques, such as a family of interferometry techniques using laser beams (e.g., laser Doppler vibrometers), can provide vibration measurement at high density spatial points without the need to install sensors on the structure. However, these measurement devices are active sensing methods that are relatively expensive and vulnerable to ambient motion. Photogrammetry is an alternative noncontact optical measurement method using (passive) white‐light imaging of digital video cameras that are relatively low‐cost, agile, and provides simultaneous measurements at high spatial density locations where every pixel becomes a measurement point. Among others, digital image correlation can achieve full‐field deformation measurements and subsequently estimate the full‐field strains. However, it is computationally extensive. This study develops a new efficient approach to estimate the full‐field (as many measurement points as the pixel number of the video frame on the structure) dynamic strains at high‐spatial (pixel)‐resolution/density location points from the digital video measurement of output‐only vibrating structures. The developed approach is based on phase‐based video motion estimation and modal superposition of structural dynamic response. Furthermore, the method is augmented by a high‐fidelity finite element model, which is updated with the full‐field experimental modal parameters “blindly” identified from the video measurement of the output‐only structure. Laboratory experiments are conducted to validate the method on a bench‐scale cantilever beam structure. Results demonstrate that the full‐field dynamic strain estimated by the developed approach from the video measurement of the output‐only vibrating beam match very well those directly measured by the strain gauges (at discrete measurement points). Some factors associated with the effectiveness of the method are experimentally studied and discussed.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/stc.2408DOIArticle
ORCID:
AuthorORCID
Yang, Yongchao0000-0003-1776-3306
Dorn, Charles0000-0001-6516-2586
Additional Information:© 2019 John Wiley & Sons, Ltd. Issue Online: 13 September 2019; Version of Record online: 16 July 2019; Manuscript accepted: 02 June 2019; Manuscript revised: 03 January 2019; Manuscript received: 01 July 2018. This work was supported by the Los Alamos National Laboratory Lab Directed Research and Development (LDRD) program in the form of a Director's Funded Postdoctoral Fellowship (grant 20150708PRD2) for Yongchao Yang. Hwee‐Kwon Jung and Gyuhae Park would like to acknowledge the partial support of National Research Foundation funded by the Ministry of Education, Science and Technology 2011‐0030065 and 2015R1D1A1A01059092. The work was completed when Yongchao Yang was with Los Alamos National Laboratory.
Group:GALCIT
Funders:
Funding AgencyGrant Number
Los Alamos National Laboratory20150708PRD2
Ministry of Education, Science and Technology (Korea)2011-0030065
Ministry of Education, Science and Technology (Korea)2015R1D1A1A01059092
National Research Foundation of KoreaUNSPECIFIED
Subject Keywords:dynamic strain; full‐field measurement; model updating; operational modal analysis; photogrammetry; video processing
Issue or Number:10
Record Number:CaltechAUTHORS:20191010-092202891
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20191010-092202891
Official Citation:Yang, Y, Jung, H‐K, Dorn, C, Park, G, Farrar, C, Mascareñas, D. Estimation of full‐field dynamic strains from digital video measurements of output‐only beam structures by video motion processing and modal superposition. Struct Control Health Monit. 2019; 26:e2408. https://doi.org/10.1002/stc.2408
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99208
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Oct 2019 17:11
Last Modified:10 Oct 2019 17:11

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