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17 May 2005 Development of a new structural monitoring system using optical fiber technology: prototype tests in the laboratory
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Monitoring the movement of existing tunnels when new tunnel construction or other construction activities occur in close proximity is important to the tunnel owners. Existing manual monitoring systems, although considered most reliable, require access to the tunnel outside of passenger traffic hours and thus only provide measurements during a limited time of the day and under non-operational conditions. Remote monitoring systems, enabling 24 hour monitoring, are currently available based on electrolevels and automatic motorised theodolites. However, it is hoped that the proposed optical fibre sensor system will be more versatile and economic to install and operate. The underlying concept is based on a fibreglass rod containing optical fibres, with Fibre Bragg Gratings (FBG) written into them, which is fixed at discrete points to the tunnel lining. The movement of the tunnel induces a deformation of the rod, and hence strains the FBGs positioned at different points along the optical fibres. The FBGs work by reflecting narrow bands of light propagating along the optical fibres, the wavelength of the reflected light being a function of the strain at the position of the grating. This paper will discuss one experimental arrangement designed to explore the challenges of installing the monitoring system and interpreting the results. Results from tests are presented and discussed together with the sensitivity and accuracy achievable with the proposed system. Further, one method of interpreting the strain measurements and hence determining the displacement of the structure will be presented.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Nicole Metje, David N. Chapman, Christopher D. F. Rogers, Pifeng Miao, Stephen N. Kukureka, Phillip Henderson, and Martin Beth "Development of a new structural monitoring system using optical fiber technology: prototype tests in the laboratory", Proc. SPIE 5765, Smart Structures and Materials 2005: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, (17 May 2005);

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