Wind studies to ensure the safety and stability of North America’s longest cable-stayed bridge
With a main centre span of 1,546 feet and a total span of 3,296 feet, the Cooper River Bridge is the longest cable-stayed bridge in North America and the third-longest in the Western Hemisphere.
In addition to spanning an unusually great distance, the Cooper River Bridge had to fulfill a number of key performance imperatives. Completed in 2005 to replace two obsolete truss bridges that no longer met Charleston’s shipping and transportation needs, the new bridge needed to:
- accommodate eight lanes of motor vehicle traffic (plus bicycles and pedestrians), with a broad, asymmetric deck 142 feet wide;
- be resilient to Charleston’s occasional hurricane conditions--capable of withstanding wind gusts over 160 miles per hour.
- provide adequate clearance (209 feet) for modern container ships on the busy shipping channel underneath;
Our work to support and inform the bridge’s design team began with extensive meteorological studies, including detailed site observations. Combined with our world-leading wind engineering expertise, our in-house climate and meteorology experts enable us to deliver exceptionally sound intelligence to bridge engineers working in hurricane-prone regions and other areas with extreme weather conditions.
After establishing a detailed picture of the conditions the bridge would face over time, we built and tested in our wind tunnel numerous configurations of the bridge’s unusually wide deck. This process helped to identify an optimal design.
To help the designers gain insight into the bridge’s stability with respect to vortex-shedding and flutter, we also tested aeroelastic models of the bridge at several critical constructed stages, as well as a 1:250 scale model of the completed structure.
In addition to studying the performance of the bridge’s deck across its exceptionally long span, we undertook additional wind tunnel studies to understand the stability and design wind loads of the bridge’s distinctive diamond-shaped towers, and to help the engineering team optimize the design and performance of the stay cables’ external damping system.
The Cooper River Bridge has been serving Charleston safely and successfully for over a decade, accommodating over half a million vehicles every week and withstanding numerous extreme weather events. The striking bridge has also become a well-loved feature of the local landscape, including as the site of a popular 10-kilometer foot race that attracts as many as 40,000 runners.