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Wireless Sensor Networks for Bridge Monitoring

Wireless Sensor Networks for Bridge Monitoring. Overview. Monitoring Opportunities Wireless Sensor Networks (WSNs) Field Installations CUED Humber Bridge. A Variety of Problems. Steel Bridges corrosion, strain, displacement, bridge bashing Masonry Arch Bridges

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Wireless Sensor Networks for Bridge Monitoring

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  1. Wireless Sensor Networksfor Bridge Monitoring

  2. Overview • Monitoring Opportunities • Wireless Sensor Networks (WSNs) • Field Installations • CUED • Humber Bridge

  3. A Variety of Problems • Steel Bridges • corrosion, strain, displacement, bridge bashing • Masonry Arch Bridges • water ingress, material loss, displacement • Reinforced Concrete Bridges • corrosion, strains, cracking

  4. Steel Bridges • The Humber Bridge • One network has already been installed to measure the corrosion environment • Future networks could include vibration and acoustic emission monitoring

  5. RC Bridges – Monitoring Opportunities • Half Joints • 450 bridges • Difficult to inspect • Hinge Joints • 100 bridges • Prestressed reinforcement condition

  6. RC Bridges – Monitoring Techniques • Strains • Electrical resistance or MEMS vibrating wire gauges • Corrosion • Acoustic Emissions (AE), but are there others? • Inclination • Abutments & bearings • Displacements • Across joints & cracks, bearings

  7. Masonry Arch Bridges • Monitoring possibilities • Digital imaging to measure displacements & loss of material • Sensors to measure water ingress into the joints • MEMS to measure pressure at the joints

  8. Other Issues • Bridge bashing • Terrorist threats • Fire • Weather • Snow or ice on the running surface

  9. WSNs • Networks composed of Sensors, Motes and Gateways • Motes take signal from sensor (typically analogue), process it and transmit it • Gateways collect data from Motes and transmit it to the outside world (ADSL, GPRS, WiFi etc.)

  10. Current WSNs • Currently have a Crossbow network up and running in the Engineering Department • System measures Temperature, Light, Sound, Acceleration and Magnetic Fields • Data is acquired wirelessly from Motes in multiple rooms

  11. Data Visualization • A web interface to interrogate the Engineering Network • Allows user to interrogate the data for multiple motes, sensors and date ranges • Ultimately also have alerts and tie-in to analysis software

  12. Humber Bridge WSN Deployments

  13. Anchorage Deployment- Success! (eventually) • Network consists of 11 MICAzs (10 with MTS400 sensor boards) and a Stargate gateway • The Stargate is connected to the Cambridge server via ADSL • Data can be accessed in near real-time via a webpage

  14. Anchorage Deployment - Monitoring Results • Data shows good correlation with expected results • System has already picked up an anomaly in operation (dehumidifier testing) • Future developments may include tabulating maximum values and email alerts if thresholds are crossed

  15. Anchorage Deployment – Problems • Initial network formation problems due to wrong monitoring software & lengthy route update times • Radio transmission problems due to: • Antenna quality • Spacing between wall and antenna • Fading • Solution: external antennas with higher gain (5 dBm)

  16. RC Bridge Monitoring • Monitor inclination of bearings using inclinometers • Monitor crack movement using LPDTs • Determine if there is long-term movement • Key Challenges: determining thresholds and actions • Potential for expansion of the network

  17. Truly Remote Monitoring • Proof of concept for completely remote system • Data will be transmitted using GPRS (mobile phone) technology • The gateway will be powered by a solar panel attached to the bridge

  18. Acceleration Response of Hangers • Vibration response may indicate damage • We need to be able to determine damping ratio with time • Issues exist in terms of high data rate (power) and aerodynamic behaviour • Fortunately we can minimize power use by ‘windowing’ the data • Using MEMS sensors we can minimize the profile of the mote

  19. RH / Corrosion / Moisture Sensing of Main Cables • A number of potential techniques: • Acoustic Emission (AE), RH or electrical resistance • AE is commonly used but requires high data rate processing & high power • We are working with Holroyd / Corus and colleagues from Imperial to develop a potential system • Are the other techniques viable?

  20. Can we cram it all in? • Advantages of this project include staged deployment, projects of interest to everyone, various levels of complexity • However implementing everything may be beyond the temporal and financial means of the project • Priorities?

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