A year and a half after the I-35 bridge collapse in Minneapolis, the five-year project aims to create the ultimate infrastructure monitoring system and install it on several test bridges whose precise locations are not yet determined.
The monitoring system is envisioned to include several different types of surface and penetrating sensors to detect cracks, corrosion and other signs of weakness. The system would also measure the effects of heavy trucks on bridges, which is currently impossible. And through enhanced antennas and the Internet, the system would wirelessly relay the information it gathers to an inspector on site or in an office miles away.
Funded in large part by nearly $9 million from the National Institute of Standards and Technology's (NIST) Technology Innovation Program (TIP), the project involves 14 U-M researchers with the College of Engineering and the U-M Transportation Research Institute (UMTRI). In addition, engineers at five private firms in New York, California and Michigan are key team members. The remaining funding comes from cost-sharing among the entities involved and the Michigan Department of Transportation. MDOT has offered unfettered access to state bridges to serve as high-visibility test-beds showcasing the project technology.
"This project will accelerate the field of structural health monitoring and ultimately improve the safety of the nation's aging bridges and other infrastructures," said Jerome Lynch, principal investigator on the project and assistant professor in the Department of Civil and Environmental Engineering. "We want to develop new technologies to create a two-way conduit of information between the bridge official and the bridge. We are excited to collaborate on these transformative technologies with partners like MDOT who could use them immediately to improve bridge inspection processes."
Four types of sensors will contribute to gathering data. Victor Li, E. Benjamin Wylie Collegiate Professor of Civil and Environmental engineering, has developed a high-performance, fiber-reinforced, bendable concrete that's more durable than traditional concrete and also conducts electricity. Researchers would measure changes in conductivity, which would signal weaknesses in the bridge. On test bridges, the deck would be replaced with this concrete.
A carbon nanotube-based "sensing skin" that Lynch and a colleague in chemical engineering are developing would be glued or painted on to "hot spots" to detect cracks and corrosion invisible to the human eye. The skin's perimeter is lined with electrodes that run a current over the skin to read what's happening underneath based on changes in the electrical resistance.
Low-power, low-cost wireless nodes could look for classical damage responses like strain and changes in vibration. These nodes would harvest energy from vibrations on the bridge or even radio waves in the air. They are being developed by Dennis Sylvester, an associate professor in the Department of Electrical Engineering and Computer Science; and Khalil Najafi, Schlumberger Professor of Engineering, Arthur F. Thurnau Professor and chair of the Electrical and Computer Engineering division.
The fourth type of sensor would be housed in the vehicles that travel on the bridge. UMTRI researchers will outfit a test vehicle to measure the bridge's reaction to the strain the vehicle imposes. This information is not available today. But how vehicles, especially trucks, affect bridges is a critical piece of information that could help predict the structure's lifetime. Leading this effort is Research Professor Tim Gordon, head of UMTRI's Engineering Research Division.
Today, bridge inspectors rely mostly on their eyes to determine if a structure is sound.
"Our work will add to what is currently done, not replace it, Gordon said. "The infrastructure problem and the feasibility of new monitoring strategies are emerging at the same time. We believe we have ways of testing the performance of bridges as integrated structures, not just inspecting their components."
Other parts of the system will organize data into meaningful displays and communicate it from the sensors to the inspector. Vineet Kamat, assistant professor in civil and environmental engineering, will lead the human-infrastructure interaction effort.
"The technologies from this project could prove very beneficial to the citizens of Michigan in the longer lasting, smarter, safer and ultimately more sustainable roadways." said State Transportation Director Kirk Steudle. "Recognizing that our nation's infrastructure is the backbone of our economy, this type of innovative research is critical to the future of Michigan and the United States. MDOT is pleased to partner with the University of Michigan on this important engineering project."
Lynch says if this set-up were installed on all bridges, researchers could then make statistical comparisons among bridges. This would help them determine if, for example, all suspension bridges developed certain dangerous signs of wear after a certain age.
"The NIST TIP initiative is timely given the deteriorated state of our infrastructure today. The success of the University of Michigan team, led by Professor Lynch, exemplifies both the excellence of our faculty and how they are engaged in high impact research that solves the world's most challenging problems," said Nancy Love, chair of the Department of Civil and Environmental Engineering.
Additional U-M researchers include: from the Department of Electrical Engineering and Computer Science, associate professor Mingyan Liu, professor Amir Mortazawi, associate professor Michael Flynn, and professor Atul Prakash; from the Department of Materials Science and Engineering, professor Amit Ghosh; from UMTRI, senior research associate Steven Karamihas, research scientist Ralph Robinson, and business development manager Todd Anuskiewicz. Other engineering firms involved are: Weidlinger Associates of New York; SC Solutions of Santa Clara, Calif.; LFL Associates of Ann Arbor; Monarch Antenna of Ann Arbor, and Prospect Solutions of Albany, N.Y.
The University has taken steps to protect the intellectual property relating to this project thus far, and plans to find commercialization partners in order to bring the technology to market.
The University of Michigan College of Engineering is ranked among the top engineering schools in the country. At more than $130 million annually, its engineering research budget is one of largest of any public university. Michigan Engineering is home to 11 academic departments and a National Science Foundation Engineering Research Center. The college plays a leading role in the Michigan Memorial Phoenix Energy Institute and hosts the world class Lurie Nanofabrication Facility. Find out more at http://www.engin.umich.edu/.