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Modal Frequency Identification of Stay Cables with Ambient Vibration Measurements Based on Nontarget Image Processing Techniques

Modal Frequency Identification of Stay Cables with Ambient Vibration Measurements Based on... Conventional sensors, such as the accelerometers and velocimeters, have been generally adopted to conduct the vibration measurements of stay cables for the identification of their dynamic parameters. Even though these contact sensors are able to obtain accurate measurements, the installation of such devices may require substantial efforts. A simple digital videogrammetric technique without using any artificial target is developed in this study to perform the ambient vibration measurements of stay cables for the subsequent identification of cable frequencies. This method significantly simplifies the image processing procedures by exploiting the straight boundary of cable to determine the midpoint of its edge line for serving as a convenient pseudo target. Demonstrated by the on-site measurements for three different cables selected from Chi-Lu Bridge, it is shown that this nontarget technique equipped with a customer grade camcorder and an ordinary tripod placed on the bridge deck can attain the same order of accuracy for cable frequency identification as that of high-resolution velocimeters. Both the vertical and transverse displacements of cable were measured under the ambient vibration amplitudes in the order of 0.5 mm and 0.2 mm, respectively. Based on this study, it is proved that the practical application of a nontarget videogrammetric technique to the cables of long-span cable-stayed bridges is not only feasible but also advantageous in many aspects. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Advances in Structural Engineering SAGE

Modal Frequency Identification of Stay Cables with Ambient Vibration Measurements Based on Nontarget Image Processing Techniques

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Publisher
SAGE
Copyright
© 2012 SAGE Publications
ISSN
1369-4332
eISSN
2048-4011
DOI
10.1260/1369-4332.15.6.929
Publisher site
See Article on Publisher Site

Abstract

Conventional sensors, such as the accelerometers and velocimeters, have been generally adopted to conduct the vibration measurements of stay cables for the identification of their dynamic parameters. Even though these contact sensors are able to obtain accurate measurements, the installation of such devices may require substantial efforts. A simple digital videogrammetric technique without using any artificial target is developed in this study to perform the ambient vibration measurements of stay cables for the subsequent identification of cable frequencies. This method significantly simplifies the image processing procedures by exploiting the straight boundary of cable to determine the midpoint of its edge line for serving as a convenient pseudo target. Demonstrated by the on-site measurements for three different cables selected from Chi-Lu Bridge, it is shown that this nontarget technique equipped with a customer grade camcorder and an ordinary tripod placed on the bridge deck can attain the same order of accuracy for cable frequency identification as that of high-resolution velocimeters. Both the vertical and transverse displacements of cable were measured under the ambient vibration amplitudes in the order of 0.5 mm and 0.2 mm, respectively. Based on this study, it is proved that the practical application of a nontarget videogrammetric technique to the cables of long-span cable-stayed bridges is not only feasible but also advantageous in many aspects.

Journal

Advances in Structural Engineering – SAGE

Published: Jun 1, 2012

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