Under the heading of learning something new every day...one of the most iconic structures on our Georgia coast, the Talmadge Memorial Bridge in Savannah, connecting Georgia to South Carolina across the Savannah River is not a suspension bridge. Suspension bridges like the Golden Gate, Brooklyn Bridge, or famed London Bridge, have large cables connecting to massive load-bearing anchors at each end, as well as frequent piers underneath (anchored to the channel, river, or even ocean floor) or along the bridge span to assist with load bearing.
The Talmadge Bridge is a 'cable-stayed' bridge, with the high-tension cables supporting the roadway by pulling the bridge UP, versus via support and tension from underneath. Opened in 1991, the Talmadge Bridge is no longer quite high enough for the world's largest container ships to always make it underneath and into the Ports of Savannah, even at low tide and following the multi-year, multi-million deepening of the Savannah shipping channel.
The Port of Savannah's container ship market share for all of North America is roughly 11%, making it a leading port along the East Coast in tonnage and contributing an estimated $59 billion each year to Georgia's GDP as well as the direct and indirect employment of about 561,000 Georgians. Current traffic loads at the port make it the third busiest in North America. Though the lead time on building that next generation of cargo tankers is long, the current largest, when fully loaded, needs about 20 more feet of clearance, or what is known as airdraft in the bridge and shipping industries to cross under the Talmadge Bridge safely.
To do this, the Georgia Department of Transportation (GDOT), along with an engineering design firm based in Peachtree City, Georgia, Kiewit Infrastructure South, are going to attempt something that has never previously been done. They plan and intend to LIFT the highest portion of the 1100-foot span of the Talmadge Bridge an additional 20 feet higher. They will be doing this by replacing the bridge's high-tension support cables with new shorter cables, at an estimated cost of $ 189 million. This work is scheduled to begin in 2025 and is projected to be completed by 2028. The project will not raise the entire bridge span, but will in effect give the bridge a peak and a good bit more curvature, as well as increase the angle and elevation of the climb. Current grades and incline on the Talmadge Bridge are at 5.5%, making it among the top 10 steepest bridges in America.
Those making their first time drive or ride across the bridge often admit this can be a slightly intimidating trip. If successful in adding to that curvature, parts of that incline will reportedly be closer to 7%. Kiewit has previously replaced cables on other cable-stay bridges, including the first span to undergo such maintenance, the Hale Boggs Bridge which spans the Mississippi River in Louisiana. That project was completed in 2012. However, this will be the first cable-stay bridge replacement with purposefully shorter cables, to reshape and raise the bridge and increase its airdraft.
Eventually, though, the next generation of cargo ships, already in the planning stages, will require an entirely new bridge, at an estimated peak height of 230 feet above sea level, or a tunnel bored more than 100 feet below the sea bed, to allow for passage of those new cargo containers as well as the next generation of luxury max-super cruise liners, that would make the Titanic look like a slightly over-sized dingy. Either of those two options comes at a price tag in the $1-2 billion range at current estimates. Thankfully the shipping industry still gives long lifetimes to most of their sea-worthy vessels, and that next generation of ships are generally NOT constructed until they have already been financed.
Ironic that the last of America's original 13 colonies, and within line of sight of General James Edward Oglethorpe's originally planned colony of Savannah, will be home to a newly designed and reconfigured bridge rising even higher as it spans north to the Palmetto State of South Carolina. I will keep in mind there are a couple of other routes to St. Simons, Jekyll Island, and other points south, staying a bit inland than along I-95, and at least until those new shorter cable spans are fully in place, I will remain a bit in suspense to see if engineers can teach a slightly old bridge, new tricks.
http://accesswdun.com/article/2024/1/1222077/keeping-things-in-suspense