Bridge repair method cuts amount of time, money for bridge maintenance

The ConnDOT issued a request for proposals from researchers interested in testing the approach and selected a team led by Zaghi and Kay Wille, Ph.D., also an assistant professor in UConn’s civil and environmental engineering department. The ConnDOT, the U.S. Department of Transportation, and the U.S. Department of Homeland Security funded the first phase of the two-phase project. Industry collaborators-Lafarge North America, a global materials manufacturer based in Chicago; Parsons Brinckerhoff, an international engineering and construction firm headquartered in New York City; and Infra-Metals, a structural steel distributor in Wallingford, Connecticut-supported the project through material donations.

The researchers wanted to test an off-the-shelf UHPC that would be easy to use in the field. They selected Lafarge’s JC1212, which is designed to reach 12 ksi strength in twelve hours when used under the prescribed conditions. “Ultrahigh-performance concrete is a family of materials that gives you high strength but at the same time is very workable,” Zaghi explains. “It’s also extremely durable. So when you do a repair, you don’t have to worry about corrosion or the effect of the corrosive environment on the concrete itself.”

After selecting the concrete, the researchers began the first phase, which is meant to determine whether the concept is feasible. They used three one-third scale, rolled-steel bridge girders modeled after an actual bridge in Connecticut to examine the concrete’s performance under loading. The first girder was corrosion-free and served as a benchmark, the second girder had reduced web and flange thicknesses at its end, typical of a corroded beam, and the third girder had as much section reduction as the second but had been repaired by applying the concrete to the corroded end, near the bearing.

The researchers used a high-capacity loading frame, which they built in-house for the project, to apply point loading to all three girders and push each to failure. The first two girders failed at the bearing, while the third eventually failed but not at the bearing at which the repair had been made. In fact, the repaired girder had more bearing capacity than the undamaged girder. It supported up to approximately 225,000 lb, while the undamaged girder supported a maximum of 180,000 lb and the damaged girder supported just 43,000 lb.

“The repair made up for the entire capacity that was lost due to corrosion,” Zaghi says.

Now that the method has been validated, researchers are preparing to begin the second phase of the project this spring. Funded by the ConnDOT, this phase will include more extensive experiments to develop standards for using the method in the real world. “Although the results that we already have shown that the concept works, there are more details that we have to investigate further to gain more confidence,” Zaghi says. The ConnDOT is also considering a pilot application of UHPC on an actual bridge. “Bridges in the pipeline for beam-end repair are being screened for suitability,” Barakat said.

The method is expected to accelerate the process for repairing corroded bridge elements. Projects that have traditionally taken weeks to complete may be done in as little as a weekend with the UHPC application, Zaghi says. “By implementing this method, DOTs may repair a much larger number of bridges, with less hassle in terms of construction time, worker safety, paint removal, and lane closure,” he says. Other benefits include protection from future corrosion-induced damage. “It’s not just research for the sake of science,” Zaghi says. “We are very much looking at the application end of it, the benefits of which are significant. This study demonstrates how innovation may address the safety challenges of the nation’s infrastructure.”  

The release notes that the team hopes to publish the results of the study in technical journals. It also plans to widely disseminate guidelines for its use so that departments of transportation and engineers across the country can use them to implement the repair method in the field.

“Steel beam-end deterioration is not a problem unique to Connecticut,” Barakat noted. “Many state and local transportation agencies, especially those affected by winter weather, have similar challenges. Although each agency has to consider many factors-[for example] traffic volume, characteristics of original bridge construction, economy of construction-this technique may be appropriate for use by other agencies.”