When a pedestrian bridge collapsed Thursday in Miami, Florida, several people were killed. The cause is being investigated, but we do know the bridge was constructed using a method referred to as “accelerated bridge construction.” The ABC method includes building portions or nearly the entire structure off-site, then putting it into place.
In North Carolina, the Department of Transportation says they have used some small-scale methods of ABC, but never built a whole bridge off-site like the one in Florida. Although, concern still surrounds the aging infrastructure across the state and in the Triad.
As a forensic engineer, Joel Howard looks at structure failures every day.
“The discoloration we’d say is consistent with corrosion of the steel,” he said referring to patches on the bridge on Freeman Mill Road over Spring Garden Street in Greensboro.
The American Society of Civil Engineers gives North Carolina’s bridges a grade of C-.
The North Carolina Department of Transportation is responsible for the safety of 13,500 bridges. Each bridge must be inspected every two years. Certified inspectors may find a bridge to be “structurally deficient.“
The designation of structurally deficient is still considered safe, but means some components are in poor condition due to deterioration. A bridge can also be considered structurally deficient if it has insufficient load-carrying capacity. Depending on the severity of the issue, the department may post a weight limit on the bridge, make immediate repairs or close the bridge completely until repairs can be made.
“They’re going to look for levels of corrosion, either on steel, you can also have it on concrete or portions of the concrete will be separating or falling off,” described Howard.
The bridge on Patton Avenue over I-40 was deemed structurally deficient along with about 10 percent of the bridges in Guilford County. But that’s less than the state-wide average of 13 percent.
For NCDOT to repair all of the state’s structurally deficient bridges, it says it would cost more than $3.8 billion.
Howard says you shouldn’t be afraid to drive over a structurally deficient bridge.
“I think it’s more something to be aware of. I think there’s typically enough checks and balances and I think the DOT does a pretty fair job with making sure bridges are safe for the general public,” he said.
Howard calls the road systems in Greensboro and Guilford County “vastly superior” to those in other parts of the state.
“They’re really unbelievable. They’re in pretty good shape,” he said.
The pedestrian bridge collapse in Florida is bringing back memories of a similar incident at the Charlotte Motor Speedway in 2000. More than 100 people were hurt when a pedestrian bridge collapsed there at the end of the All-Star Race.
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