LOOKING BELOW THE SURFACE

Structural monitoring is now seen as an integral part of successful programmes for maintaining both new and ageing structures. This paper describes a fibre-optic monitoring system that could lead to improved monitoring of piles. The IMAC Laboratory of LMS-EPFL in Switzerland has developed a non-incremental long-term monitoring system, SOFO, based on low-coherence interferometry, which has already been applied successfully to bridges and other engineering structures. The SOFO sensor system has two single-mode fibres, which are installed in the structure to be monitored. The measurement fibre is contained in a pipe, attached at both ends of the measurement zone and pretensioned in between. The reference fibre is placed loose in the same pipe. All deformations in the structure result in a change in the difference between the lengths of these fibres. A double Michelson interferometer is used to measure this difference. A single reading unit can be used to monitor several fibre pairs in multiple sensors and structures at the desired frequency. Three prefabricated concrete floating piles were tested in preparation for constructing a cut-and-cover tunnel in Switzerland. The behaviour of a heat-exchanger pile, which can heat the surrounding soil, was also tested. Obvious benefits of such structural monitoring were found.

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  • Corporate Authors:

    Palladian Publications Limited

    15 South Street
    Farnham Surrey GU97QU,   United Kingdom 
  • Authors:
    • INAUDI, D
    • Laloui, Lyesse
    • STEINMANN, G
  • Publication Date: 2000-5

Language

  • English

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Filing Info

  • Accession Number: 00796529
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Aug 2 2000 12:00AM