[Slide Show] "Smart" Bridges Harness Technology to Stay Safe
Engineers are deploying sensors to monitor the condition of some of the world's most famous bridges
![[Slide Show]](https://static.scientificamerican.com/sciam/cache/file/AABE95E0-0B99-4913-A352317FC83B1D95.jpg?w=590&h=393)
[Slide Show] "Smart" Bridges Harness Technology to Stay Safe
- TSING MA BRIDGE, HONG KONG, CHINA The Tsing Ma Bridge in Hong Kong—the world's seventh longest suspension bridge, with two decks carrying both road and rail traffic—is one of the most heavily monitored bridges in the world. The Tsing Ma Bridge has the most loaded cables of any bridge in the world and is located in an area susceptible to tropical typhoons. As such, it is designed to sway and bend and can handle wind speeds up to 212 miles (341 kilometers) per hour. GPS sensors mounted on the towers and cables measure wind speed. About 100 photonic sensors are used to monitor the strain on the bridge’s cables. The bridge has a complete structural health monitoring system. © MINGHONG/ WIKIMEDIA COMMONS
- RIO-ANTIRIO CHARILAOS TRIKOUPIS BRIDGE, GREECE The six-lane Charilaos Trikoupis Bridge in Greece links the town of Rio to the mainland, across the Gulf of Corinth. The two-mile (three-kilometer) bridge has roughly 300 sensors that monitor its condition and alert operators if an earthquake or high winds warrant shutting it down to traffic. Soon after opening in August 2004, the sensors detected abnormal vibrations in the cables holding the bridge, which led engineers to install additional weight to dampen the cables. © GUILLAUME PIOLLE/ WIKIMEDIA COMMONS
- KAP SHUI MUN BRIDGE, HONG KONG, CHINA The Kap Shui Mun Bridge is the second longest cable-stayed bridge in the world. Like the Tsing Ma Bridge, it has two decks and is heavily monitored using sensors, including accelerometers, strain gauges, anemometers, weigh-in-motion and temperature sensors. © MINGHONG/ WIKIMEDIA COMMONS
- ST ANTHONY'S FALLS I-35 BRIDGE, MINNEAPOLIS, USA The St. Anthony's Falls Bridge, the new I-35 bridge that replaced the bridge that collapsed in Minneapolis in 2007, has an embedded early warning system made up of 323 networked sensors—wire and fiber optic strain and displacement gauges, accelerometers, potentiometers, and corrosion sensors. They are built into the span and monitor it for structural weakness such as corroded concrete and overly strained joints. Temperature sensors embedded in the roadway set off an anti-icing system that sprays potassium acetate on the surface when the weather turns cold. A traffic monitoring system alerts the Minnesota transportation department to reroute traffic over the 10-lane bridge in case of an accident or overcrowding on the span. The cost for all the electronics and technology was about $1 million, a small fraction of the bridge's $234 million pricetag. © MINNESOTA DEPARTMENT OF TRANSPORTATION
- THE GOLDEN GATE BRIDGE, CALIFORNIA, USA The Golden Gate Bridge spans the opening of San Francisco Bay into the Pacific Ocean. The San Andreas Fault runs close by, and the area is susceptible to major earthquakes. While the Golden Gate Bridge does not have an overall sensor-based health monitoring system like the new I-35 Anthony Falls Bridge in Minneapolis, it does have earthquake sensors. It is also currently being seismically retrofitted, with a planned completion date in 2012. © ANITA DIKINME/ WIKIMEDIA COMMONS
- GI-LU CABLE STAY BRIDGE, TAIWAN The Gi-Lu Cable-Stay Bridge in Taiwan has wireless sensors and accelerometers that monitor its structural health. It spans the Juo Sheui, the longest river in Taiwan, and features a single concrete pylon rising 190 feet (58 meters) above the deck supporting 68 steel cables. The bridge is 787 feet (240 meters) long with the pylon in the center of the main span. The structural health monitoring is done by an international group of researchers led by C. H. Loh of National Taiwan University. © C.H. LOH, NATIONAL TAIWAN UNIVERSITY AND JEROME LYNCH, UNIVERSITY OF MICHIGAN AT ANN ARBOR
- THE BROOKLYN BRIDGE, NEW YORK, USA The Brooklyn Bridge, opened to traffic in 1883, is one of New York City's iconic bridges and connects lower Manhattan to Brooklyn. The 126-year-old bridge now has fiber optic sensors that measure displacement and temperature, says Bojidar Yanev, executive director of bridge inspection and bridge management, New York City Department of Transportation. © BOJIDAR YANEV, NEW YORK CITY DEPARTMENT OF TRANSPORTATION
