At three-and-one-half-miles-long, Charleston, S.C.'s Arthur Ravenel Jr. Bridge, which spans the Cooper River, is the longest cable-stayed bridge in North America.
Replacing two outdated truss bridges, the new bridge's eight lanes cross a main span of 1,546 feet, and include two 572-foot high diamond-shaped concrete towers, high-level approaches, 15 ramps and two interchanges. Completed in only four years, one year ahead of schedule, the project saved the South Carolina Department of Transportation an estimated $150 million. In addition to improving ease and safety in crossing the river, the bridge's 1,546-foot-wide main span allows for a 1,000-foot-wide navigation channel, enabling Charleston, the fourth busiest port in the U.S., to be more competitive.
Designed to meet extreme wind, ship collision and earthquake conditions while maintaining safety and mobility for the traveling public and preserving the area's scenic, aesthetic, historic and environmental resources, the bridge is the first major design-build project in the U.S. It also incorporated significant community outreach, educational and job training programs before, during and after construction, including training for socially and economically disadvantaged individuals and pairing high school and college students with transportation organizations for on-the-job training. In addition, the bridge has received praise from numerous agencies, including the U.S. Fish and Wildlife Service, for its resolution of environmental issues, including its use of demolished bridge material for artificial offshore reefs, its impact on less than one acre of surrounding wetlands and its protection of natural habitat for migratory birds and the Loggerhead Sea Turtle.
Opened on July 16, 2005, the bridge's innovative structural engineering solutions included offset stay cable anchors to reduce main span tower moments, very long, continuous approach spans that minimized the overall number of bearings and joints and the use of large-diameter drilled shafts framed directly into pier columns to eliminate nearly all of the pile caps. High capacity drilled-shaft foundations were also selected due to their overall economy in difficult subsurface conditions. The site is overlaid with up to 50 feet of soft soil, requiring drilled shafts up to 240-feet-deep to obtain adequate resistance in the clay layer below. Though pile driving would have been possible in some areas, it was avoided to many instances to decrease noise for nearby residents.
Due to the project's size, its construction was spilt into five jobs—two interchanges, two approaches and the main span. One of the keys to its successful construction management was the project team's innovative and flexible approach to sequencing. For example, the main span team began building the bridge deck before completion of the towers. Also, to achieve an affordable solution, the design team used hollow rectangular main pier towers—which provided ductility and simplified construction—and continuous high-level approach spans to provide a flexible and cost-competitive structure that could withstand seismic demands and minimize future maintenance.
The project was selected by ASCE as a finalist for the 2006 Outstanding Civil Engineering Achievement (OCEA) Award.