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Proceedings Paper

Bridge monitoring by interferometric deformation sensors
Author(s): Daniele Inaudi; Samuel Vurpillot; Nicoletta Casanova
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Paper Abstract

In many concrete bridges, the deformations are the most relevant parameter to be monitored in both short and long- terms. Strain monitoring gives only local information about the material behavior and too many such sensors would therefore be necessary to gain a complete understanding of the bridge behavior. We have found that fiber optic deformation sensors, with measurement bases of the order of one to a few meters, can give useful information both during the first days after concrete pouring and in the long term. In a first phase it is possible to monitor the thermal expansion due to the exothermic setting reaction and successively the thermal and drying shrinkages. Thanks to the long sensor basis, the detection of a crack traverse to the measurement region becomes probable and the evolution of cracks can therefore be followed with a reduced number of sensors. In the long-term it is possible to measure the geometric deformations and therefore the creeping of the bridge under static loads, especially under its own weight. In the past two years, our laboratory has installed hundreds of fiber optic deformation sensors in more than five concrete, composite steel-concrete, refurbished and enlarged bridges (road, highway and railway bridges). The measuring technique relies on low-coherence interferometry and offers a resolution down to a few microns even for long-term measurements. This contribution briefly discusses the measurement technique and then focuses on the development of a reliable sensor for direct concrete embedding and on the experimental results obtained on these bridges.

Paper Details

Date Published: 24 September 1996
PDF: 12 pages
Proc. SPIE 2895, Fiber Optic Sensors V, (24 September 1996); doi: 10.1117/12.252146
Show Author Affiliations
Daniele Inaudi, Swiss Federal Institute of Technology and Smartec SA (Switzerland)
Samuel Vurpillot, Swiss Federal Institute of Technology (Switzerland)
Nicoletta Casanova, Istituto di Meccanica dei Materiali SA (Switzerland)

Published in SPIE Proceedings Vol. 2895:
Fiber Optic Sensors V
Kim D. Bennett; Byoung Yoon Kim; Yanbiao Liao, Editor(s)

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