One decade down, nine to go.
The Arthur Ravenel Jr. bridge was built to last a century and was designed to withstand hurricanes, earthquakes and ship collisions. After its first 10 years in service, it has yet to weather such a serious test.
Instead, its challenges have come from far more minor corners, such as occasional icicles, protesters and a fuel truck spill.
Unlike its predecessor, the Grace Bridge, which was the world’s fifth longest cantilevered truss bridge when it opened in 1929, there are more than 50 longer cable-stayed bridges in the world.
Its main claim to fame — it held the title of longest cable-stayed bridge in North America — was lost with little fanfare in 2011, when the John James Audubon Bridge opened in Louisiana (its 1,583 span was about 38 feet longer than the Ravenel’s).
But the bridge is still considered an engineering marvel, not only for its durability and scale but also for the way it satisfied those concerned about the region’s environment, heritage and health, all while staying within budget and ahead of schedule.
The need for the new bridge was demonstrated by history. In 1886, a magnitude 7.3 earthquake rocked Charleston and was felt as far away as New York and Cuba. In 1946, a freighter ran into the Grace bridge and toppled a 240-foot-long section, killing a family of five that was driving across it. In 1989, Hurricane Hugo became the most devastating storm to batter the Lowcountry in modern times.
Timothy Mays is an associate professor of engineering at The Citadel and did some initial design work on the Ravenel Bridge project before a design-build team was chosen. He says the bridge is most impressive because of what it can withstand.
“I’m always touting this as the one location in the United States where it’s not just one hazard — it’s earthquakes and hurricanes,” he says. “To me, that’s kind of the big point. It’s designed for a multi-hazard environment like we have here in Charleston and it’s unique to Charleston.”
Bobby Clair, the Highway Department’s point person during the bridge’s construction, said the bridge is remarkable not only for its physical characteristics but also for the unique way it was designed and built as part of one contract. As construction began, engineers and architects were just beginning to figure out how it would be built.
“The most challenging part of the job was to referee the 500 experts who were working on the design of this thing, and the design review,” Clair said. “Because it was design-build in the agreement, we allowed the contractor to select a qualified engineering firm to design it. The DOT had the duty to check the design to make sure it was good.”
Clair’s job was to ensure the state’s feedback came on time, within two weeks tops, and that it was based on facts, not opinion.
“We had engineers on one side and engineers on the other side, and just like architects, there was a large amount of opinion about how things should look, how they should work,” he says. “To get to the bottom of that, we had meetings literally 14 hours a day, six, seven days a week, until we got through these issues. Most of the design was completed in 15 months, so that crunch time, that first 15-18 months, took a lot of effort, a lot of energy, a lot of travel, a lot of listening and a lot of refereeing. But that’s the only way we could keep the project moving.”
Clair agreed that the Lowcountry’s climate necessitated a uniquely complex design, and the greatest challenge was designing for an earthquake. Six seismic experts were brought into the project and held about eight meetings in Charleston, New York and San Francisco. Some knew foundations, some structure and some modeling.
The bridge’s key seismic feature is its oversized expansion joints on either end of the main towers, which are designed to accept up to five feet of movement, he said. If a big quake strikes, the hope is those damaged joints could be covered by steel plates and the bridge quickly reopened within a day.
The bridge’s 128 cables come down into damper systems designed to absorb the shock of the deck moving. “Like on the Bridge Run, you don’t feel a lot of movement like you might expect,” Clair said. “It feels like you’re driving down the interstate highway to me. I don’t feel anything.”
The rock islands around the base of each tower were a little easier, but not easy.
“As each of those were designed, it was put into a model and tested for stiffness, flexibility and shock collection.
The Danish Hydraulic Institute came up with the scheme to build rock islands that covered about five acres on the river bed and about one acre above the water. These islands, made from Newfoundland limestone, are designed to absorb the impact of any ship veering toward a tower.
“We went over and witnessed the test in Copenhagen and saw that it would work.” Clair said. Once that was confirmed, the 650,000 tons of limestone and 50,000 tons of dolomite were shipped to the site.
Clair, whose grandfather had helped build the Grace bridge in the early 20th century, said one of the greatest challenges was getting it out of the ground.
“The foundation work was tedious. That work went on 24-7, drilling these 10-foot diameter foundations, 240 feet deep, getting all that reinforcing steel cages made up and put down the shaft and pouring the concrete,” he said.
Sonar testing tubes showed that three shafts in Town Creek had bad concrete and needed to be drilled out and re-poured “It took about a year to fix those shafts in Town Creek. It took a long time, a lot of money,” Clair said. “It was all on the contractor and subcontractor that were doing that work to make that repair, and it cost about three times what it did to put the initial shaft in.”
As the state committed to build the bridge, it wasn’t initially sure it would have enough money to build a single eight-lane bridge, much less a pedestrian and bicycle lane or approach ramps from East Bay Street and Wingo Way.
Clair said he personally intervened to change the East Bay Street-Morrison Drive ramp from its initial route, which had it steeply ascending parallel to the bridge — entering downtown right near where Morrison’s tidal flooding is at its worst.
Elevating Morrison Drive would keep it dry but also would act as a dam that would flood the nearby public housing. Instead, Clair pushed for finding a way to thread the curving on-ramp under the existing Grace and Pearman bridges. “Looking at the alignment on East Bay and Morrison Drive, it works perfectly,” he said. “We had a very small margin during the process of what changes could be made, and I’m extremely proud of that. That change cost us about $5 million.”
And Clair said his other most satisfying day was when the two spans were joined.
“There were so many different factors that play into that, and we had about four different ways we were checking elevations and surveying the alignment of that bridge,” he said. “The towers would actually move left or right when the sun was coming up in the morning and going down in the afternoon, so to have everything perfect, you had to understand what the temperature was doing to those tall towers and all that concrete and steel.”
While the tight budget meant that some of the bridge’s piers and other features weren’t designed with any special flair, Clair said he is proud of the result.
“There are much longer bridges. There are much taller bridges, but there are a lot of bridges now that have been built and that are being built in the U.S. that are carbon copies of this,” he said. “I don’t know how it ranks, but I think the community likes it. That’s the most important thing.”
Reach Robert Behre at 937-5771.