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Infrastructure Technology Institute

I-65 JFK Bridge over Ohio River (anchor Bolts)

The ITI Research Engineering Group from Left to Right: Daniel Marro, David Kosnik, Mathew Kotowsky, and Daniel Hogan

Infrastructure Safety and State of Good Repair Through Structural Health Monitoring

The John F. Kennedy Memorial Bridge carries seven lanes of Interstate 65 over the Ohio River at Louisville, Kentucky. The ends of the continuous cantilever span are secured by uplift bearings. Since 2007, Northwestern University ITI’s advanced computer-controlled sensing systems for real-time measurement of critical engineering quantities have provided important insight for detection and repair of corrosion-related failures of uplift bearing components, helping keep this bridge of both regional and national importance in good repair and safe for the 120,000 vehicles that cross it daily.

What is Structural Health Monitoring?

Structural health monitoring (SHM) of transportation infrastructure is the deployment of advanced sensors and data acquisition equipment on in-service transportation facilities - bridges, tunnels, roads, ferries, and railroads, to name a few - to measure critical engineering quantities in real time. SHM supplements the national bridge inspection program by providing performance data between inspections, measuring quantities that are invisible to the eye, such as strain, and reporting results from components that are obscured or difficult to reach.

SHM of the I-65 JFK Bridge Uplift Bearings

Sensors on uplift bearing components measure strain, movement, and temperature at key locations on both the original bearing assembly and retrofi­ts. A computer-controlled data logger on the bridge records data and transmits it back to the lab.

Detecting A Component Failure From 400 Miles Away

On the evening of September 29, 2008, the structural health monitoring system measured a large, sudden shift in strain measurements on an uplift bearing anchor rod, suggesting that the rod had fractured. Northwestern ITI researchers in the Chicago-area lab reviewed the data and promptly alerted the bridge owner. Upon inspection, the rod was found to be completely severed. Without monitoring, no one could have known about the fracture until the next routine inspection - even then, the fracture would have been nearly invisible, as the paint remained intact.

Reporting Data Over The Internet For Timely Management Decisions

  • Data are automatically transmitted to the lab and displayed on a password-protected Web site.
  • Accessible only to bridge owner and researchers
  • Automatically updated with latest data
  • Connected to relational database containing all sensor readings since beginning of project
  • Easy comparison of current readings to historical trends helps engineers identify anomalies

Technology Transfer

The goal of this research is to develop SHM systems that can be deployed readily by state DOTs and other transportation infrastructure owners.

Not every bridge needs SHM - but SHM can provide substantial benefits for management of aging, complex, non-redundant/fracture critical, or difficult-to-repair bridges.

Northwestern ITI’s SHM technology - a product of University Transportation Center research - is already in use for management of in-service transportation infrastructure in several states. Northwestern ITI has deployed continuous remote SHM systems like the JFK Bridge system on in-service roads and bridges with the Kentucky Transportation Cabinet, Chicago Transit Authority, Wisconsin DOT, California DOT (Caltrans), Ohio DOT, Indiana DOT, and Florida DOT.