If a highway bridge fails, the results can be catastrophic.
Fortunately, bridge failure in the United States is the exception—with, on average, about 50 bridges each year failing. And to ensure bridge performance as much as possible, advanced diagnostic testing is needed to complement existing inspection methods to identify damage and deterioration that can compromise structural integrity.
In Iowa, such a diagnostic system, one that continuously and autonomously monitors the structural health of bridges in real time, is getting closer to mainstream use. The structural health monitoring (SHM) development project is a joint venture between the Bridge Engineering Center (BEC) at Iowa State University’s Institute for Transportation and the Iowa Department of Transportation. This work has resulted in a patent-pending system known as Bridge Engineering Condition Assessment System (BECAS).
The system differs from others because it provides immediate, autonomous data analysis and a much improved method for presenting the data so Iowa DOT engineers can readily use it and also access it later should the need arise.
“The monitoring takes place in real time with very, very little user interaction,” says Brent Phares, BEC director, who has been developing the system since 2005. “The system’s software applications run 24 hours a day, analyzing data collected 250 times per second and only alerts an engineer when needed.”
The fully automated SHM system, which uses sensors and software with several specially designed algorithms, was first tested on a U.S. Highway 30 bridge near Ames. Its success led to its yearlong use on the new U.S. 65 Iowa River arch bridge in Iowa Falls, where BEC engineers installed sensors during and after construction of the span. The system has since been installed at locations in Iowa, Illinois, and Wisconsin.
Implementation continues on several Interstate and high-traffic state highway bridges. Overall, Phares likes what he sees. “I’m really excited about its potential.”
Iowa started monitoring bridges in the early 2000s, but the new BEC monitoring system is a major step forward as a “complete and quantifiable bridge assessment tool,” Phares says. In addition to providing real-time alerts of a bridge overload or catastrophic event, it provides historical, quantifiable tracking of changes in a bridge’s structural condition.
Ahmad Abu-Hawash, chief structural engineer in the Iowa DOT Office of Bridges and Structures, says traditional inspections will continue to be the primary method for assessing the condition of Iowa bridges, but adds that additional tools are needed to improve efficiency and accuracy. “Continuous SHM systems will help us obtain real-time data and alert us of any unusual behavior due to unforeseen events.”
Another feature of the SHM, Abu-Hawash says, is its capability to determine a bridge’s true load-carrying capacity, something “that cannot be quantified by traditional analysis methods.”
Phares says the monitoring system provides continuous data that are easily accessible and readily and directly implementable by Iowa DOT staff for timely decision making. “The system can be implemented on basically any bridge type to evaluate general performance in addition to targeted, damage?prone structural areas,” he says.
Someday, he hopes, bridges on an entire major Iowa highway corridor will be equipped with the SHM system. “I’d love to see 100 regular bridges on Interstate 80 all self-reporting data every day.”
Bridge partnership between Iowa DOT, ISU’s Bridge Engineering Center benefits the state
Since 1996, InTrans has had a special relationship with its primary sponsor, the Iowa DOT, through ongoing agreements. This unique-in-the-nation relationship enables InTrans to conduct research, provide technical support, oversee statewide asset management programs, and partner in other ways for the Iowa DOT.
One of the partnership’s major cogs is between the Iowa DOT’s Office of Bridges and Structures and the ISU Bridge Engineering Center, which “is valuable to both organizations and the state of Iowa in general,” says Ahmad Abu-Hawash of the Iowa DOT.
“Iowa DOT benefits from having access to technical resources and expertise in structural engineering at BEC to address bridge engineering problems. It also benefits the researchers at ISU by getting input from practitioners at Iowa DOT and providing access to a large pool of highway structures.
“The result is safer highway infrastructure, innovative research, and improved efficiency, which may lead into improved livability and economic development in Iowa.”
From "InTrans En Route - July 2015 to June 2016" published by the Institute for Transportation.