Structural observation of long-span suspension bridges for safety assessment: implementation of an optical displacement measurement system

Martins, L. Lages; Rebordão, J.; Ribeiro, A.

doi:10.1088/1742-6596/588/1/012004

Cited by 11 publications

(25 citation statements)

References 5 publications

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“…Vibrations decayed to less than 0.3 mm within 2 s and showed a modal frequency of approximately 4.5 Hz. The displacement measurement shown in Figure 7a includes data during several stationary periods (i.e., the time intervals of [0,12], [17,24], [31,38], and [46,55] s). The data samples collected during these periods were used to evaluate the measurement accuracy of the vision-based system.…”

Section: Measurement and Analysis Resultsmentioning

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%

“…• Full projection matrix is the general form of transformation metric between the 2D image plane and the 3D structural coordinate system with no assumption, with example applications in Oh et al, [19] Martins et al, [24] Park et al, [41] and Kim et al [42] The calibration process usually comprises two steps, (a) offline calibration in the laboratory to determine camera intrinsic parameters [43] and (b) site calibration to estimate the camera extrinsic matrix (i.e., camera position and orientation relative to the structural coordinate system) based on at least four sets of point correspondences. The full projection matrix is the multiplication of the camera intrinsic matrix and camera extrinsic matrix.…”

Section: Two-step Camera Calibrationmentioning

confidence: 99%

“…2D = two-dimensional some known geometric information in the structure that is commonly acquired with the assistance of some artificial targets, for example, planar targets [42,44] and a 3D calibration object. [24] Because the offline camera calibration step in the full projection matrix method could consider lens distortion that is common in consumer-grade cameras, the full projection matrix method is used in the video processing package.…”

Section: Two-step Camera Calibrationmentioning

confidence: 99%

“…The bridge provides cyclist and pedestrian access to Sandy Park Stadium (south side of bridge), the home ground of Exeter Chiefs [17,24], [31,38], and [46,55] s), STD = standard deviation.…”

Section: Bridge Descriptionmentioning

confidence: 99%

See 4 more Smart Citations

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

Brownjohn

Kong

2018

Struct Control Health Monit

164

106

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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.

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Section: Measurement and Analysis Resultsmentioning

confidence: 99%

Section: Non-contact Sensingmentioning

confidence: 99%

Section: Two-step Camera Calibrationmentioning

confidence: 99%

Section: Two-step Camera Calibrationmentioning

confidence: 99%

Section: Bridge Descriptionmentioning

confidence: 99%

See 3 more Smart Citations

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

Brownjohn

Kong

2018

Struct Control Health Monit

164

106

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

Brownjohn

2017

J Civil Struct Health Monit

232

125

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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.

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Dynamic Deformation Measurement by the Sampling Moiré Method from Video Recording and its Application to Bridge Engineering

Tsuda

Chang

et al. 2020

Exp Tech

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Measuring accurate dynamic deformation distribution for large-scale structures inexpensively and efficiently is a crucial challenge of structural health monitoring. In this study, a simple technique for measuring the deflection and vibration frequency from a captured video, based on the sampling Moiré method is developed. The striking advantage over conventional measurement using sensors and other imaging techniques are that the developed technique allows accurate measurement of two-dimensional deformations at multiple locations as well as the natural frequency of the target structure. Joint Photographic Experts Group (JPEG)-formatted images encoded from the recorded video with Motion-JPEG (MJPEG) format reduced the file size significantly without degrading the measurement accuracy and applied to deformation measurement. The effectiveness of the developed technique was confirmed through a field experiment of an old bridge in Taiwan. The field experiment demonstrated that both deflection and natural frequency of the bridge were successfully measured with higher 0.1 mm displacement accuracy and 0.05 Hz frequecy comparable to a conventional microwave radar displacement sensor from 20 m distance.

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Structural observation of long-span suspension bridges for safety assessment: implementation of an optical displacement measurement system

Cited by 11 publications

References 5 publications

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

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

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

Dynamic Deformation Measurement by the Sampling Moiré Method from Video Recording and its Application to Bridge Engineering

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