After being the link between the mainland and the Outer Banks for decades, pieces of the dismantled Herbert C. Bonner Bridge, which was replaced in 2019 by the 2.8-mile Marc Basnight Bridge, are now used for different purposes. .

The beams were sent to NC State University in Raleigh for stress testing at the college’s built facility lab. The goal is to learn how an aged bridge exposed to half a century of extreme weather conditions can inform better bridge designs in the future, according to the North Carolina Department of Transportation, which is funding the project and has facilitated the recovery work of the beams. and test them.

“This is a very unique opportunity,” said Neil Mastin, who manages the research and development unit of NCDOT, in a statement. “It’s not often that you get a bridge in this extreme environment for almost 60 years that was intact enough that we could actually use it for testing.”

The researchers first subjected the beam to a low-level cyclic load in which a force is repeatedly applied, removed, and reapplied in a manner similar to the types of stresses a bridge experiences from passing vehicles. Then the beam was subjected to monotonous loading until it reached peak load levels, or continued pressure until it broke, NCDOT officials said.

It took more than 200,000 pounds to break the beam of the bridge, the weight of nearly three semi-trailers pressing down on the beam from one point. Sensors with cameras were used to observe how the beam reacts to loads, how it moves and where cracks form when pressure is added to the beam.

“What we’re really trying to study is the amount of prestressing in this structure,” said Giorgio T. Proestos, assistant professor at NC State who is leading the project. “Is this enough? Should there be more? Should there be less? And how does this preload change in 60 years? Based on the results of the experiment, there could be changes in the way things are done in the future. ”

NCDOT said it would publish the results once the project is completed. Mastin said the findings will likely inform bridge design and construction decisions nationwide, not just in North Carolina.