North Carolina DOT conducting research on demolished Bonner Bridge

The North Carolina Department of Transportation (NCDOT) is partnering with North Carolina State University (NCSU) on a research project related to pieces from the Herbert C. Bonner Bridge.

Girders from the now-demolished Bonner Bridge have been sent to NCSU in Raleigh to undergo stress testing at the college’s Constructed Facilities Lab. The goal is to use lessons learned about how an aged bridge exposed to a half-century of extreme weather conditions can inform better bridge designs in the future, according to a press release.

NCDOT is funding the project and facilitated the work to salvage the girders and test them in Raleigh.

“This is a very unique opportunity,” Neil Mastin, who manages NCDOT’s Research and Development unit, said in a statement. “It’s not often you get a bridge in that extreme environment for nearly 60 years that was intact enough that we can actually use it for testing.”

According to NCDOT, the test consisted of two parts. First, the girder was subjected to low-level cyclic loading in which force is applied, removed, and reapplied repeatedly in a manner similar to the kinds of stresses a bridge takes on from passing vehicles. Then, it was subjected to monotonic loading until reaching peak load levels—essentially pressing on it continuously until it breaks. NCDOT says it took more than 200,000 lb of force to break the bridge girder.

Sensors with cameras were used to observe how the beam responds to loads, how it moves and where cracks form when pressure is added to the girder.

The Bonner Bridge once served as a transportation lifeline for people headed to the Outer Banks until it was dismantled a few years ago to make way for a new bridge. ​It was replaced by the Marc Basnight Bridge, which finished work in February 2019 and was named the #2 bridge of the year on Roads & Bridges’ Top 10 Bridges of 2019.