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Infrastructure Technology Institute

SGR Through SHM: Ensuring Transit Infrastructure


A sensor installed by the ITI REG on a railway bridge retrofit.

Federal Transit Administrator (FTA)Peter Rogoff, recently addressing the National Summit on the Future of Transit, underscored the importance of keeping our urban transit systems in a state of good repair – SGR – if they are not only to be safe, but if they are also to meet national goals for congestion reduction, energy efficiency, and greenhouse gas emission reductions. 1 He noted that the FTA study on the condition of our transit systems estimates that $78 billion is needed to bring all systems to SGR, of which $50 billion is required for the rail transit component alone.

There are several obstacles to filling this gap. The most obvious is lack of revenues, particularly at the state and local levels, where there is heavy dependence on sales taxes that have been hard hit by the economic downturn. This makes it especially important to set investment priorities wisely. While there is natural appeal to the public and their leadership to invest in new transit systems and extend existing ones, Administrator Rogoff pointedly ask how communities would support ever larger systems if they could not, or would not, maintain current systems in a state of good repair.

While a political commitment to achieving and maintaining SGR for transit is a first step, guiding investments in rehabilitation and renewal in a time of scarce resources – and it is always a time of scare resources for transit – requires good information. That information includes timely characterization of the physical condition of infrastructure and rolling stock, as well as measures of service utilization (to indicate importance of facilities and services to communities).

Condition information typically comes from hands-on inspections, and while we should never relax the diligent use of “eyeballs,” costs, comprehensiveness, and reliability of manual methods are problematic. The opportunities and advantages for automated structural health monitoring (SHM) in transit are abundant. Appropriately deployed, automated monitoring can target critical infrastructure elements, identify evolving problems, and signal emergent conditions that might not be detected in a timely fashion with manual methods.

SHM systems can keep computerized eyes on key infrastructure components, provide long-term data streams to track critical trends, and call for help when problems become critical. Such information can provide the objective guidance for setting rehabilitation priorities to assure that we get the most transportation value out of scarce resources.

In this issue of Field Notes, the description of ITI’s collaboration with the Chicago Transit Authority to monitor deteriorating concrete bridges provides a good example of efficient use of innovative SHM methods to transit infrastructure. The description of our efforts to model SHM data from a highway bridge in Wisconsin illustrate approaches to long term structural monitoring and analysis. Together these show how ITI’s SHM work on can contribute importantly to keeping our transportation infrastructure in SGR.

1. As quoted in C. Kenneth Orksi’s newletter, “Innovation NewsBriefs,” Volume 21, Number 10, May 26, 2010.