Keeping tabs on the structural health of the Arthur Ravenel Jr. Bridge is an ongoing effort for the state Department of Transportation as it evaluates how the bridge is standing up to the weather and daily pounding of traffic.
As the longest cable-stayed bridge in North America approaches its fifth birthday in July, the DOT is busy keeping it looking good but more importantly taking stock of how the span is aging.
"We try to keep it clean. We try to keep it swept. It's an icon of the state," said Gary Kinard, assistant resident bridge maintenance engineer.
A 2-inch-thick layer of concrete mixed with latex forms the bridge driving surface. This week, the DOT will take some inch-wide plugs out of the road to see if salt has worked its way to concrete slabs below.
"We'll analyze it for salt-water intrusion over the deck to see how much salt is getting through the concrete," Kinard said.
Over the long term, salt could cause steel used to reinforce the slabs to rust, which weakens the metal. "We don't want the steel inside the deck to corrode so we test it for the salt level," he said.
Inspectors aren't expecting to find a problem since salting roads in icy conditions is rare here because winters are relatively mild, he said.
The work is done to maintain warranties for the roadway, bridge structure and foundation. As part of that process, cables supporting the bridge deck were checked last week.
All state bridges are inspected at least every two years. The DOT constantly monitors the condition of the Ravenel bridge. "We've got people on that bridge every day of the week," said James Law, the DOT Charleston district spokesman.
In the Upstate, routine DOT inspections recently uncovered cracks in some steel-plated girders supporting four Interstate 77 bridges. As a result, Transportation Secretary Buck Limehouse ordered inspection of 70 bridges statewide including 16 spans in the Lowcountry.
None of the Lowcountry bridges were found to have cracked steel. Investigators are still looking into why the metal on the I-77 bridges cracked. Increased traffic, heavier vehicles and putting salt and sand on the roadbed during hazardous winter driving conditions may have played a role, officials said.
Because of the cracked steel, DOT will replace the bridges on I-77 at Exit 62 in Chester County. DOT shored up the bridges and prepared two-lane exit and entrance ramps which will be used as detours when the bridges are closed. A $2.1 million bridge-replacement contract has been finalized with United Contractors, which has 60 days to complete the project. The project will be paid for from the DOT's budget.
The I-77 bridges over SC Route 901 in York County have been shored up for safe travel. The bridges are being evaluated to see whether the cracked beams found at that location can be repaired or will require a complete bridge replacement. Limehouse issued an emergency declaration for the bridges on May 12.
The Upstate bridges with cracked steel were built more than 30 years ago.