Traffic Monitoring Using FBG Sensors

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Traffic Monitoring Using FBG Sensors
Hands-On Sensor Course April 22, 2004 Marley
Kunzler Blue Road Research 376 NE 219th
Avenue Gresham, OR 97030 [phone]
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Outline

• 1. Functionality of the Dynamic FBG System
• 2. Background on Project
• 3. Results from Testing
• 4. Summary Future Work

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Functionality of the Dynamic FBG System
Light is launched through the core of a fiber
optical strand to the grating
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Functionality of the Dynamic FBG System
As the fiber undergoes tension compression, the
grating spacing changes
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Functionality of the Dynamic FBG System
The gratings reflection is spectrally demodulated
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1998 - Horsetail Falls CFRP Strengthening
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FBG Traffic Sensor Advantages
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Overview Leading up to First Freeway Install

• In July, 1999 Oregon Dept. of Transportation
  contracted Blue Road Research to develop a
  traffic sensor (based on fiber optic sensor
  technology) which is more durable, reliable and
  cost\installation effective than traditional
  sensing methods.
• The primary focus of the contract a sensor for
  vehicle classification and counting, (flexibility
  for other traffic sensing applications).
• After preliminary testing on a concrete and
  asphalt testpad, sensors were installed in the
  Interstate 84 freeway East of Portland, Oregon on
  August 1, 2001.

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Blue Road Research Goals

• Create and Demonstrate a Fiber Optic Traffic
  Sensing System
• Count and Classify Traffic Using Fiber Optic
  System
• Test Ruggedness of Sensors for Freeway Use
• Determine Optimal Installation Procedures
• Develop an Enhanced Traffic Sensor Product Line

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Final Layout (Top-View)
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Final Layout (Sensors Area)
Junction Box
Fiber Backbone Line
Bicycle path
On Ramp
207th Overpass
Sensors are approx. 7 feet apart in left wheel
lane.
n
l
k
m
j
Sensor 5 (diagonal) monitors temperature.
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Grooving 205th Avenue to Enable Fiber Optic
Installation Remote Monitoring
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Trenching the Fiber Optic Cableto the Freeway
Site
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Cutting Grooves for Sensor Placement in the
Freeway Lanes
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Installation of the Traffic SensorsInto Portland
Cement Concrete
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Filling the Sensor Grooves with Bituminous Hot
Melt (375 F)
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Roadside Junction Box at Ground Level
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Installation of the Traffic System Network
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Data Collected from Semi Trailer
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Data Collected from Semi Trailer
Relative Amplitude vs. Time
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Car Profile
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Conclusions Future Work

• Costs prohibitive for traffic classifier, but not
  Weigh-in-Motion (WIM)
• Development under NSF of up to 12 channel
  self-tuning readout system suitable for freeway
• Pursuing funding for WIM research

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Modal Analysis of Bridges Using Fiber Bragg
Grating Sensors

• Background
• Long gage length fiber Bragg grating sensors
• Modal Analysis
• Full scale field test, 2002
• Current work
• Blue Road Research multiplexed FBG system
• Laboratory Experiments
• Fairview Model Bridge
• Broadway Bridge work
• Summary

Session 6, Page 64
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Acknowledgements

• National Science Foundation
• STTR Grant No. DMI-0131967

• Caltrans
• Support of full scale field test

• Oregon DOT
• Continuing support of civil structures research

ODOT

• Multnomah County Bridge Section
• Support of upcoming bridge system deployment

Session 6, Page 65
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Long Gage Length Fiber Bragg Grating Sensors
Packaging
Aluminum bulkheads for anchor points
Rugged housing

• One meter gage length

Session 6, Page 66
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Modal Analysis (1 Degree of Freedom)
Session 6, Page 67
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Modal Analysis (1 Degree of Freedom)
Tongue, Benson H. Principles of Vibration. Oxford
University Press Oxford. 1996. 101.
Session 6, Page 68
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Modal Analysis (multi-DoF)
Session 6, Page 69
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Modal Analysis (multi-DoF)
Session 6, Page 70
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Experimental Validation of the Approach 2002
Carbon Splice Test

• 30 composite wrapped concrete beam with splice
  at midspan
• Test performed by UCSD, FHWA, CALTRANS
• Blue Road Research and UCSD
• Placed optical sensors on the beam
• Performed dynamic tests

Session 6, Page 71
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Carbon Splice Test I-5 Gilman Bridge
Session 6, Page 72
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Carbon Splice Test Mode Shapes
Session 6, Page 73
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Carbon Splice Test Modal Vectors
Session 6, Page 74
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Conclusions from Splice Test

• Strong agreement between accelerometer and FOS
  data
• Validates use of Long Gage FOS in system
  identification
• Clear changes in modal characteristics with
  damage
• Suggests that this method will work for detecting
  structural damage in bridges

Session 6, Page 75
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Current Work

• Algorithm refinement by UCSD
• Enable location and quantification of damage
  through system identification
• Hardware development for sensor data acquisition
• Acquire data from eight sensors simultaneously
  with sub-microstrain resolution
• Full scale deployment on the Broadway Bridge in
  Portland, Oregon
• in planning with Multnomah County Bridge Section

Session 6, Page 76
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Laboratory Tests Instrumented I-Beam

Session 6, Page 77
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Laboratory Tests Parked and Sweeping Etalon
Parked
Sweeping

Session 6, Page 78
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Laboratory Tests Parked Etalon

Session 6, Page 79
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Field Tests BRR Fairview Bridge

• Environmental Effects
• Temperature
• Wind
• Performance
• Modal Analysis with controlled damage
• Quasi-static loading

• 20x4 steel truss
• Concrete and composite deck
• Sensors installed in concrete
• Sensors planned for installation on structure and
  in composite section

Session 6, Page 80
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Blue Road Research Health Monitoring and Seismic
Damage Assessment System
Session 6, Page 81
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Cable Routing from Readout Unit to Sensors
Session 6, Page 82