using acoustic sensors to monitor structural cable...
TRANSCRIPT
Using Acoustic Sensors to Monitor Structural Cable Performance
Michael S. Higgins, P.E.Pure Technologies410-309-7050
What is a Structural Cable?
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?
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
How to Assess a Cable?Conventional inspections rely on visual inspections
Grouted Stay Cable
Suspension Bridge Cable
Post Tensioning Tendon
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?
Extrapolation?
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
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
How Does Acoustic Monitoring Work?
WWW Data Center
ReportDAQWire Break
Bridge
Limitation of Visual InspectionsFiltering Ambient Noise
Limitation of Visual InspectionsFiltering Ambient Noise
Limitation of Visual InspectionsQuincy Bayview Bridge
Limitation of Visual InspectionsSensors on the Quincy Bayview
Limitation of Visual InspectionsSensors on the Quincy Bayview
Limitation of Visual InspectionsCabling on the Quincy Bayview
Limitation of Visual InspectionsData Acquisition System on the Quincy Bayview
Limitation of Visual InspectionsNear Real Time Availability of Data
Limitation of Visual InspectionsNear Real Time Availability of Data
Insert screen capture
Limitation of Visual InspectionsNear Real Time Availability of Data
Challenges of Continuous Monitoring
• Software problems (e.g. viruses)
• Power outages
• Operating system freezes
• Power outages
• Lightening strikes
• Durability
Other Operating Acoustic Monitoring Systems
Other Operating Acoustic Monitoring Systems
Suspension Bridge Monitoring Systems
Suspension Bridge Monitoring Systems
Post-Tensioned Bridges
Who is Pure Technologies?Combining Video and Other Sensors
Who is Pure Technologies?Combining Video and Other Sensors
Limitation of Visual InspectionsComplete Structural Monitoring
Wacker Drive, Chicago, IL• Acoustic• Extensometers• Strain Gages• Tiltmeters• Thermocouples• Humidity• Load Cells
Limitation of Visual InspectionsReasons for Structural Health Monitoring Systems
1. Problematic Structure
2. Proactive inspection/assessment