In a groundbreaking study, researchers at the University of Illinois Urbana-Champaign have developed a novel approach using shape memory alloys (SMAs) to mitigate damage to concrete railroad ties. Led by Bassem Andrawes, a professor in civil and environmental engineering, this innovative system adapts reinforcement in response to rail traffic, significantly enhancing safety.
Concrete rail ties serve a crucial role in maintaining the stability of railroad tracks, but they are prone to warping and cracking due to repeated use. These structural failures can pose serious safety risks, including the potential for derailments if left unaddressed. The research team found that SMAs, which are capable of returning to their original shape after deformation, could be the key to preventing such damage.
The researchers demonstrated that concrete ties subjected to simulated rail traffic could recover their original form through the activation of SMAs via induction heating. Their findings were published in the Journal of Transportation Engineering, Part A: Systems.
Andrawes expressed his enthusiasm for the project, stating, “We”re doing something that I think is unprecedented in rail transportation engineering. We”re collaborating with a commercial supplier of concrete rail ties to implement and test our designs. Our work has progressed beyond laboratory settings to meet rail industry standards, and we are eager to advance our industrial partnership to develop a practical design.”
Traditionally, concrete degradation has been countered through prestressing methods, which involve inserting pre-tensioned steel rods to counteract heavy loads. However, this method faces challenges as different sections of the tie experience varying degrees of stress. Moreover, the ties shift as the ballast—the gravel bed that distributes weight and drains water—settles under traffic.
Andrawes believes SMAs present an ideal solution, as they can be integrated into ties and independently controlled using self-contained heat sources. This adaptability allows reinforcement to respond to the specific stresses experienced at various points within the tie”s structure.
In collaboration with Ernesto Pérez-Claros, a graduate student in civil and environmental engineering, Andrawes employed induction heating to restore the SMAs” original shape without the need for electrical components inside the ties. The research was conducted in three phases: casting their design with Rocla Concrete Tie, Inc., conducting laboratory tests to assess different SMA lengths, and subjecting the ties to stress tests that simulated rail traffic. The prototypes not only met but exceeded the standards set by the American Railway Engineering and Maintenance-of-Way Association (AREMA).
Andrawes emphasized the importance of transitioning their work from the laboratory to real-world applications, stating, “Demonstrating that our design complies with and surpasses AREMA specifications ensures that it is viable for practical use by railroads. Our goal is to guide this technology towards widespread adoption.”
The research team plans to continue its collaboration with Rocla to commercialize this technology. Additionally, they intend to submit their prototypes for comprehensive testing under actual rail conditions at the Federal Railroad Administration Transportation Technology Center in Pueblo, Colorado. The study titled “Experimental Testing of Concrete Crossties Prestressed with Shape Memory Alloys” is publicly accessible online.
This research received support from the Transportation Research Board and the Transportation Infrastructure Precast Innovation Center, which operates under the University Transportation Center program of the U.S. Department of Transportation.
