South Carolina highways and railroads cross several rivers, harbors and lakes. Over the course of two centuries bridges in South Carolina have evolved into intricate and durable engineering feats comparable to any around the world. South Carolina bridges range from the very modern cable-stayed Ravenel Bridge in Charleston to wood-supported bridges carrying light traffic on less traveled roads. Most bridges in South Carolina, however, are designed for carrying either very heavy highway traffic or railroad trains weighing thousands of tons.
South Carolina is a low-lying area with moderate hilly terrain to the west. There are no open valleys or canyons traversed by large bridges. South Carolina, however, has several multiple lane interstate highways crossing large rivers and lakes. Concrete pile bridges span these waterways. The concrete pile bridge is a series of concrete columns driven deep into the bedrock supporting the connecting concrete or steel girders of the roadbed. These bridges are on Interstate 95 over Lake Marion, U.S. Hwy 17 over Winyah Bay between Georgetown and Myrtle Beach and across several rivers.
The same construction method is used on hundreds of interstate and highway viaducts throughout South Carolina. The difference with these smaller bridges, however, is steel pilings are driven into the ground and vertical concrete supports are poured around the steel foundations.
Railroads in South Carolina use many steel-truss bridges for crossing rivers and lakes. Steel bridges provide strong platforms for tracks while being relatively light on the concrete bridge piers rising from the water. The light steel reduces the stress on the bridge structure when the tremendous weight of locomotives and loaded freight cars cross the bridge.
Steel bridges are still used in coastal areas of South Carolina for carrying roads across navigable passages such as the Inland Coastal Waterway. Steel drawbridges and "swing" bridges (bridges with rotating platforms to open for large boats) cross both the ICW and some inland rivers near the coast.
South Carolina has two cable-stayed bridges for crossing large rivers at a great height. The Ravenel Bridge between Charleston and Mount Pleasant crosses Charleston Harbor near the mouths of the Cooper and Wando Rivers. Also, the Talmadge Bridge connects South Carolina and Savannah, Georgia over the Savannah River.
These two cable-stayed bridges are constructed mostly of concrete with large cable-supported arches. These arches provide wide open channels for large ship traffic on the rivers. These two bridges have clearances of 185 feet for the Talmadge bridge and 186 feet under the Ravenel bridge.
The cable-stayed bridge design provides the strength of concrete while remaining relatively light and reducing the strain on the bridge supports. Each bridge has an expected lifespan of well over 100 years.
