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Sensor for large smart composite footbridge

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IDIL Fibres Optiques has collaborated with IFSTTAR in order to integrate optical fiber sensors (FBGs) into concrete within the framework of civil engineering applications.

IDIL has developped 176 Fiber Bragg Gratings (FBGs) sensors photo-imprinted on 24 connectorized optical fibers.

Those optical fibers were designed to withstand alkaline metal while resins with a special reticulation process were used. Consequently, the manufactured cable is flexible enough to be packaged in strand and to follow the geometry of the structure that must be monitored.

This particulat shape enables to ensure a continuous and efficient fixation into concrete. Otherwise, this specific coating which consists of a semi-stiff cable allows a perfect information transfer from the concrete as far as the optical fiber without any change in the deformation field.

  • Fiber Bragg Gratings sensors
  • Flexible cable to follow the geometry of the structure
  • Optical Time Domain Reflectrometry (OTDR)
  • Optical Frequency Domain Reflectrometry (OFDR)
  • Brillouin or Raman frequency interval measurements
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  • Civil engineering
  • Aerospace engineering
  • Offshore environment
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DECID2 PROJECT
Period2008-2012
Research Institute CollaborationFrench Institute of Science and Technology for Transport, Development and
Networks (IFSTTAR)
ObjectiveDemonstartors made out of smart composites with double-capacity of
structural health monitoring in-situ by both optical fiber sensors and ultrasonic
patchs
Footbridge dimensions20 m long x 7 m large
CompositionPultruded composites: glass fiber/vinylester and carbon/epoxy
IDIL ObjectivesIntegration of fiber optic sensors embedded in a beam of the footbridge by
pultrusion
Sensors typesStrain, temperature, vibration
Number of sensors176 FBG sensors
CompositionGlass fiber, epoxy resin
Optical fiberSingle mode 1.5 µm SMF 28 (G 652 standard)
Number of fibers6 fibers per beam (24 fibers in total)
Length10 cm ≤ L ≤ 50 m
Outer diameter80 µm fiber
Connector typeFC/APC
Number of connectors48 connectors
Metallic jacket diameter4.6 mm. The length must be specified.
Number fo beams4 beams
Transfer coefficient>0,9
Thermal expansion coefficient2.2 10-6 °C
Strength resistance480 MPa
Elastic elongation3%

The DECID2 project involved the construction of a Platform of large dimensions made entirely of smart composites. Two demonstrators were manufactured and installed.

The target is to experiment and model their performances under mechanical and environmental aging.

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