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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 Networksfor Bridge Monitoring


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Overview

  • Monitoring Opportunities

  • Wireless Sensor Networks (WSNs)

  • Field Installations

    • CUED

    • Humber Bridge


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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


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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


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RC Bridges – Monitoring Opportunities

  • Half Joints

    • 450 bridges

    • Difficult to inspect

  • Hinge Joints

    • 100 bridges

  • Prestressed reinforcement condition


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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


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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


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Other Issues

  • Bridge bashing

  • Terrorist threats

  • Fire

  • Weather

    • Snow or ice on the running surface


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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.)


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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


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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


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Humber Bridge WSN Deployments


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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


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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


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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)


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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


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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


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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


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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?


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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?