Vision-based system identification technique for building structures using a motion capture system

Hester

2017

Front. Built Environ.

Optics-based tracking of civil structures is not new, due to historical application in surveying, but automated applications capable of tracking at rates that capture dynamic effects are now a hot research topic in structural health monitoring. Recent innovations show promise of true non-contacting monitoring capability avoiding the need for physically attached sensor arrays. The paper reviews recent experience using the Imetrum Dynamic Monitoring Station (DMS) commercial optics-based tracking system on Humber Bridge and Tamar Bridge, aiming to show both the potential and limitations. In particular, the paper focuses on the challenges to field application of such a system resulting from camera instability, nature of the target (artificial or structural feature), and illumination. The paper ends with evaluation of a non-proprietary system using a consumer-grade camera for cable vibration monitoring to emphasize the potential for lower cost systems where if performance specifications can be relaxed.

mentioning

confidence: 99%

Vision-Based Bridge Deformation Monitoring

Hester

2017

Front. Built Environ.

“…[10,[13][14][15][16] Previous studies have indicated the significant potential of vision-based systems for structural condition evaluation, especially for system identification. [17][18][19] Other applications based on the camera measured displacement include finite element model calibration, [20] damage detection, [21] and bridge weigh-in-motion where another camera is used for the traffic monitoring. [22] However, vision-based systems still face several field challenges, such as the requirement for stable camera mounting, [11] measurement error caused by lighting changes, [23] and atmospheric effects affecting light refraction-particularly for long-range measurements.…”

Section: Review Of Vision-based Approachesmentioning

confidence: 99%

“…In most examples, an artificial target or a set of targets with salient features and some known dimensions [13,19,24] were attached to a structure for the convenience of stable target tracking and, more importantly, for providing point or line correspondences to determine the projection transformation relating the image coordinate system and the structural coordinate system. Recent non-contact field applications [17,[25][26][27] have eliminated the dependency on artificial targets by using a scaling factor for camera projection transformation.…”

Section: Non-contact Sensingmentioning

confidence: 99%

“…The feature of distributed sensing has been used in laboratory structures [17,19,29,30] for multistorey displacement measurement and system identification, as well as for cable vibration monitoring [31][32][33][34] aimed at the estimation of modal frequencies or cable tensions, but applications in bridge deformation measurement are limited, with only a few examples. [27,35] …”

Section: Distributed Sensingmentioning

confidence: 99%

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A non-contact vision-based system for multipoint displacement monitoring in a cable-stayed footbridge

Struct Control Health Monit

Kong

2018

164

106

SummaryVision-based monitoring receives increased attention for measuring displacements of civil infrastructure such as towers and bridges. Currently, most field applications rely on artificial targets for video processing convenience, leading to high installation effort and focus on only single-point displacement measurement, for example, at mid-span of a bridge. This study proposes a low-cost and non-contact vision-based system for multipoint displacement measurement based on a consumer-grade camera for video acquisition and a custom-developed package for video processing. The system has been validated on a cablestayed footbridge for deck deformation and cable vibration measurement under pedestrian loading. The analysis results indicate that the system provides valuable information about bridge deformation of the order of a few centimetres induced, in this application, by pedestrian passing. The measured data enable accurate estimation of modal frequencies of either the bridge deck or the bridge cables and could be used to investigate variations of modal frequencies under varying pedestrian loads. KEYWORDSbridge displacement, cable vibration, cable-stayed bridge, pedestrian loads, vision-based system | INTRODUCTIONStructural health monitoring is aimed at providing valuable information about structural performance and characterisation of structural defects to the asset owners, especially for those civil infrastructures beyond the design life. Vibrationbased modal tests are a common way for structural condition and serviceability assessment, providing a direct view about the structural stiffness, mass properties, and their distributions. [1] As well as for validating designs of civil structures, modal parameters extracted from vibration data obtained in short-term or long-term measurements are widely believed to have potential for identifying changes in structural condition or "damage." [2] The sensitivity of these parameters to damage depends on the nature of the damage, for example, local deterioration of material, for example, due to corrosion, may not be detectable against background effects of environmental variability, whereas boundary conditions are known to have a relatively strong effect, for example, fixity of bridge supports.[3]This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

“…Vision-based systems offer significant potential for structural condition assessment, in particular for system identification [15][16][17]. In addition, deformation information has been used for finite element model calibration [18], damage detection [19] and contribution to bridge weigh-in-motion system with camera assistance for traffic monitoring [20].…”

Section: Introductionmentioning

confidence: 99%

Review of machine-vision based methodologies for displacement measurement in civil structures

J Civil Struct Health Monit

2017

232

125

Vision-based systems are promising tools for displacement measurement in civil structures, possessing advantages over traditional displacement sensors in instrumentation cost, installation efforts and measurement capacity in terms of frequency range and spatial resolution. Approximately one hundred papers to date have appeared on this subject, investigating topics like system development and improvement, the viability on field applications and the potential for structural condition assessment. The main contribution of this paper is to present a literature review of vision-based displacement measurement, from the perspectives of methodologies and applications. Video-processing procedures in this paper are summarised as a three-component framework: camera calibration, target tracking and structural displacement calculation. Methods for each component are presented in principle, with discussions about the relative advantages and limitations. Applications in the two most active fields, bridge deformation and cable vibration measurement, are examined followed by a summary of field challenges observed in monitoring tests. Important gaps requiring further investigation are presented, e.g. robust tracking methods, non-contact sensing and measurement accuracy evaluation in field conditions.