Clemson study: DOT knew of Wando bridge damage in 2012; similar bridges had cables fail
CHARLESTON, S.C. (WCIV) - As repairs are made to broken support cables that forced the closure of the James B. Edwards Bridge on Interstate 526 westbound, a report suggests the South Carolina Department of Transportation was aware of and documenting problems with the Wando bridge at least six years prior.
A study by Clemson University's civil engineering department published in January 2012 cites several reported problems with the Wando bridge listed in SCDOT inspection reports. ABC News 4 has requested copies of the inspection reports from the study authors.
Clemson's report was part of a case study on ways to improve risk assessments and identify causes of failures in "post-tensioned segmental concrete box girder bridges" such as the James B. Edwards Bridge.
In the report, Clemson engineers said research showed 21 concrete bridges like the Wando bridge had failed between 1950 and 2009. The leading cause of failures was structural deterioration related to water leakage, corrosion from water and de-icing salts, and overall poor bridge maintenance.
Specifically, Clemson researchers said studies show water and de-icing salts once inside the bridge structure can damage support cables on the bridge, also known as tendons. The tendons are anchored into the bridge's structure, and provide tension to stabilize the bridge deck, DOT says.
DOT engineers have said there are eight main support tendons that run directly beneath the Wando bridge deck, and another 84 secondary cables embedded within the concrete structure of the bridge. Each tendon consists of seven 19-strand steel cables welded together, which are then sealed in ducts filled with protective grout.
According to the Clemson study, water and de-icing salts once inside the bridge structure can reach the tendons through splits in the duct sleeves, unsealed duct joints and unsealed holes through which the ducts were filled with grout. The water and salt then degrade the grout and eventually corrode the tendons.
The 2012 Clemson report says one significant problem with the Wando bridge noted in past DOT inspections was improper grouting of the ducts that encase the tendons. Additionally, Clemson engineers said in their 2012 study that DOT inspections had shown:
- Leaky bridge joints
- Clogged drainage holes
- Cracks in the piers that support the bridge
- Debris in the voids of the concrete foundation boxes under the bridge deck where the main cables are housed
In October 2016, four years after Clemson's study was published, DOT says it found one of the eight main support tendons on the James B. Edwards Bridge was damaged, leading to weekly inspections of the bridge after repairs were completed.
On May 14, 2018, more than six years after Clemson's study was published, DOT said another of the main tendons under the bridge had ruptured, and that a secondary cable broke, as well. A third cable was also found to be damaged.
Officials have shut down the westbound side of the bridge to replace and repair the tendons. DOT still has not given an official cause for what led to the cable failures, but said there was evidence within the bridge structure of corrosion and water intrusion.
Christy Hall, secretary of transportation for South Carolina, said Wednesday she expects to have a report detailing the cause for the snapped cable next week. Copies of the Clemson report have been handed over to Hall for review by a task force she formed to investigate the failure of the James B. Edwards Bridge.
Hall has stressed to members of her bridge review task force the importance of matching up inspection records with documentation of the corrective actions taken in the past, DOT spokesman Pete Poore said Thursday.
"The public deserves and will get detailed answers from SCDOT on the maintenance, repairs and structural integrity of the bridge," Poore said.
While the forensic report on what led to the failures is being compiled, SCDOT head engineer Leland Colvin says inspectors have identified a problem at five of 51 areas on the surface of the bridge where water is getting into the structure.
The problem areas for water intrusion are where the pier columns meet the bridge, Colvin says.
DOT crews are fabricating on site the new tendons that will replace the broken and damaged ones found during the May 14 inspection. The bridge is expected to reopen June 11.