EVENT DETAIL

Suspension bridges serve as iconic structures across the world and provide a vital link to the communities in which they serve. Today, there are approximately 147 major suspensions bridges around the globe with span lengths greater than 1,000 feet – with the U.S. home to nearly one-third.

The discovery of corrosion and cracked and broken wires within the main cables of many older suspension bridges and the consequent loss of strength has posed a serious problem for long-span bridge owners. Conventional corrosion protection systems, such as painting, oiling and wrapping, have been largely ineffective in preventing deterioration and loss of strength in main cables.

The largest contributing factor to the deterioration of the cables is – moisture. The ingress of moisture within the cables not only provides the catalyst for corrosion, but also provides the chemistry for the production of hydrogen as part of the cathodic reaction, which in its atomic form can diffuse into the high strength steel wires and can result in hydrogen induced stress corrosion cracking and brittle failures.

To combat the issue of moisture and its deleterious effects on the cable, main cable dehumidification was developed nearly 20 years ago in Japan to address deterioration found in bridge cables that were less than 10 years old. The premise of main cable dehumidification is to remove the moisture to a level where corrosion practically ceases and the driver for hydrogen embrittlement is reduced.

Since its inception, approximately 30 suspension bridges around the world have been dehumidified including the William Preston Lane, Jr. Memorial (Bay) Bridge in Maryland – the first of-its-kind project in North America. Since this time, additional main cable dehumidification projects are in planning, design or construction to include the Delaware Memorial Bridge (DE/NJ), S. 10th Street (Pittsburgh, PA), Anthony Wayne Bridge (Toledo, Ohio), Ben Franklin Bridge (Philadelphia, PA) and George Washington Bridge (New York, NY).

This presentation will describe the history of main cable dehumidification and provide details of the increasing application of the technology in the U.S. The presentation will also report on the success of dehumidification in arresting the further deterioration of suspension bridge cables where dehumidification systems have been installed.