using acoustic sensors to monitor structural cable...
TRANSCRIPT
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Using Acoustic Sensors to Monitor Structural Cable Performance
Michael S. Higgins, P.E.Pure Technologies410-309-7050
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What is a Structural Cable?
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Cable Performance History
• Suspension Bridges over 120 years
• Post tensioning tendons and stay cables more recent
• Performance has been excellent
• How do we inspect/assess a cable?
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Challenges of Assessing a Cable
• Main structural elements are hidden
• Corrosion or fatigue problems can be localized
• Corrosion or fatigue will not necessarily produce visual evidence
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How to Assess a Cable?Conventional inspections rely on visual inspections
Grouted Stay Cable
Suspension Bridge Cable
Post Tensioning Tendon
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Limitation of visual inspections
Inspecting a 20-foot length of cable with wedging at 8 points exposes less than 0.1% of the wire for a typical suspension bridge (4,000 foot main cable with 15,000 wires).
(Robert Nickerson (1998), “Safety Appraisal of Suspension Bride Main Cables”, National Cooperative Highway Research Program, Transportation Research Board, Contractor’s Report fro a Workshop in Newark, NJ)
Unexposed
ExposedHow Much of the Cable is Inspected?
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Extrapolation?
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Limitation of Visual InspectionsAcoustic Health Monitoring for Cables
• Electronically monitor acoustic events being transmitted through a structure
• Identify acoustic event associated corrosion/fatigue problem
• Proven to reliably detect wire failures in cables and tendons
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Limitation of Visual InspectionsCables & Acoustic Monitoring
• Wire failures generate significant energy release
• A few sensors can monitor entire length of cables
• Wire failures can be distinguished from ambient noise
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How Does Acoustic Monitoring Work?
WWW Data Center
ReportDAQWire Break
Bridge
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Limitation of Visual InspectionsFiltering Ambient Noise
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Limitation of Visual InspectionsFiltering Ambient Noise
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Limitation of Visual InspectionsQuincy Bayview Bridge
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Limitation of Visual InspectionsSensors on the Quincy Bayview
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Limitation of Visual InspectionsSensors on the Quincy Bayview
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Limitation of Visual InspectionsCabling on the Quincy Bayview
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Limitation of Visual InspectionsData Acquisition System on the Quincy Bayview
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Limitation of Visual InspectionsNear Real Time Availability of Data
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Limitation of Visual InspectionsNear Real Time Availability of Data
Insert screen capture
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Limitation of Visual InspectionsNear Real Time Availability of Data
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Challenges of Continuous Monitoring
• Software problems (e.g. viruses)
• Power outages
• Operating system freezes
• Power outages
• Lightening strikes
• Durability
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Other Operating Acoustic Monitoring Systems
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Other Operating Acoustic Monitoring Systems
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Suspension Bridge Monitoring Systems
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Suspension Bridge Monitoring Systems
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Post-Tensioned Bridges
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Who is Pure Technologies?Combining Video and Other Sensors
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Who is Pure Technologies?Combining Video and Other Sensors
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Limitation of Visual InspectionsComplete Structural Monitoring
Wacker Drive, Chicago, IL• Acoustic• Extensometers• Strain Gages• Tiltmeters• Thermocouples• Humidity• Load Cells
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Limitation of Visual InspectionsReasons for Structural Health Monitoring Systems
1. Problematic Structure
2. Proactive inspection/assessment