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Corrosion Blamed for SC Bridge Cable Failure

Tuesday, June 5, 2018

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The James B. Edwards Bridge, in Charleston, South Carolina, reopened Saturday (June 2) after more than two weeks of work stemming from what officials now say was a cable failure caused by corrosion.

The bridge, which carries Interstate 526 over the Wando River, was closed by the South Carolina Department of Transportation May 14 after a routine inspection uncovered a severed cable inside the westbound span of the twin-span concrete box-girder bridge. It was the second time in less than two years that a cable was found to have been damaged inside the structure.

James B. Edwards Bridge
Images courtesy of SCDOT

The James B. Edwards Bridge, in Charleston, reopened to westbound traffic Saturday after cable damaged caused by corrosion. 

SCDOT had a new cable installed to replace the damaged one, and fabricated and installed an additional cable for the sake of redundancy in case of any future cable problems.

Officials had previously predicted the bridge would reopen June 11; the repair beat that time estimate by more than a week.

Corrosion to Blame

SCDOT said late last week that an investigation had determined that corrosion caused by moisture intrusion had caused the cable failure, and that corrosion had also been to blame for the failure of another cable in the same span in 2016.

The agency wrote in a letter to state Rep. Nancy Mace, R-Daniel Island, that the cable that broke last month was being monitored as part of the bridge’s regular weekly inspections and “was actually tested, with good results, at a location less than two feet from where it failed.”

Snapped cable

One of the main cables of the bridge was found to have snapped completely as a result of corrosion.

Moisture intrusion has been a known issue on the bridge since long before the 2016 incident. In 2011, a paper authored by a group of Clemson University engineers used the bridge as a case study, noting that SCDOT had identified problems including “improper grouting of ducts, leaky joints, debris in the box void, clogged drain holes (3/4-inch-diameter) and cracks in the piers.”

History of Issues

The bridge was built between 1989 and 1991 at a cost of $34 million and was designed by FIGG; the post-tensioned segmental box-girder spans each include eight main cables running the length of the bridge and another 84 cables embedded in the concrete of the structure. Each of the main cables consists of 19 strands, and each strand is made up of seven wires.

SCDOT told Mace that it estimates the agency has spent at least $6.5 million in repairs on the bridge prior to this month’s incident; that includes $1.8 million to repair the cable that ruptured in 2016 and an additional $2.5 million in testing and investigations related to the tendon issues.

The agency says testing was performed last year on seven of the main cables in the westbound span—not including the one installed just last year—but results are still pending in that investigation. “Preliminary information” indicates corrosion areas were found on two of the cables, the agency says.


Tagged categories: Bridge cables; Bridges; concrete; Corrosion; NA; North America; Quality Control; Roads/Highways

Comment from Thomas Van Hooser, (6/5/2018, 8:51 AM)

Basic engineering principle: Design for inspection and maintenance.

Comment from luiz de miranda, (6/5/2018, 2:23 PM)

Britlle or fragile rupture? By photos we can see fractures at 90 degree but it s not clear if this one come from cut or mechanical failure.

Comment from Michael Halliwell, (6/6/2018, 11:17 AM)

Luiz, a few have white ends (like a brittle fracture), some have necking down (overstressed - tensile failure)...I'm only armchair quarterbacking here, but something reduced the capacity and then the rest went pretty quickly. Combining the corrosion reports, perhaps the cable was weakened by corrosion (reducing the tensile strength of the cable) and then snapped at the highest stress location.

Comment from luiz de miranda, (6/6/2018, 4:31 PM)

Michael, yes, I agree with your comments, however the possible pitting occurrence induces tension's concentration and the failure occurs perpendicular to tension axis. My questions is on the possibility of this phenomenum, viz a viz the pictures showed

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