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Bridges, Tunnels and Steampipes Without Control
Following the tragic collapse of the I-35W bridge in Minneapolis, state and federal officials have been busy sending out inspectors to take another look at the bridges spanning the roads and rivers in their territories. Despite a century or so of advances in strain gauges, portable metal fatigue detection systems and an increasing ability to network all these instruments together, the main way to see if your infrastructure is creaky to the point of collapse is still to send someone to go take a look. Why is that?
I wrote a column about the lack of gauges and such following a partial ceiling collapse at our Big Dig tunnel here in Boston. That tunnel is, of course, much newer than the forty-year-old I-35W bridge, but despite lots of surveillance and billions of dollars in funding, the flaws that led to the tunnel ceiling collapse went undetected until, and again tragically, a big chunk of the ceiling fell on a passenger car causing one fatality.
The Big Dig column ran in July of 2006 and said in part, “The opening of the Microsoft Worldwide Partner Conference in Boston on July 11 was delayed as attendees were caught in a traffic jam due to a Big Dig crisis. The crisis was tragic (resulting in one death), as some huge chunks of concrete crashed from the ceiling to the roadway in one of the access tunnels. Despite spending $14.5 billion on the project, there is apparently no warning system that can detect when abnormal stress in the tunnels reaches the breaking point.”
“Why is it that tech vendors continue to focus on the financial and digital systems of businesses while missing the opportunity to tie in the physical systems (including electrical, heating and cooling) on which companies depend? By happenstance, the fallen concrete and Partner Conference delay illustrated how not just Microsoft, but lots of vendors, are missing the next big thing in technology. “
After I wrote that column, it was pointed out to me that one reason vendors did not invest in these systems is that there is no money to made in selling these systems. You can potentially make a lot more of a return if you are a company selling a new social dating site, a new video site to upload funny home movies or the latest eco plan to turn weeds into gas than you can selling systems that can detect when a bridge is about to fall or a steam pipe that has reached the bursting point.
The technologies to do this type of monitoring are not some far off future development. Materials Technologies Inc in Los Angeles offers one such system.
In a press release, the Materials Tech president offered the following assessment, “A recent AP article stated that the May 2006 evaluation of the I-35 bridge recommended monitoring of ‘fatigue cracking’ on the bridge’s girders. This type of tragedy can be prevented. The visual inspection techniques that are the industry standard for evaluating fatigue and cracks are simply not adequate. Our EFS and Fatigue Fuse technologies are relatively inexpensive and efficient ways to monitor growing crack issues in real-time.”
The company also offered this sobering bullet list of infrastructure information: -Visual Inspection is the most used inspection method, and according to the Federal Highway Association, about 90% of fatigue cracks are missed during visual inspections
-A bridge failure (closure/ collapse) occurs once a week on average in the US – causing highway congestion, which ultimately affects economic productivity -Average age of a bridge is > 50 years old – most bridges in the US are designed for a 50-year life
– 26% of U.S. bridges are not designed to handle current traffic levels or need major repairs; among the 11 Northeastern states, 39% of bridges are structurally deficient or functionally obsolete (The Road Information Program®, TRIP, 2005)
A second approach to bridge monitoring was offered by an academic paper from the Northwestern University Technology Infrastructure Institute. In that paper Time Domain Reflectometry Monitoring of Bridge Integrity and Performance, the authors discuss a simple way to monitor bridge supports.
In the technology world there is an axiom that states before you can improve a system you first have to be able to measure the system. In order to measure a system you have to be able to instrument and monitor the system. One of the tragic lessons from the I-35W bridge collapse is that big building projects that do not start or include a retrofit with systems to consistently monitor the status of those projects can lead to disaster.