The Olympic flame is expected to cross the new 2.25-kilometer Rion-Antirion Bridge on its way to the opening of the Athens games next month. Designed to withstand the pounding of an earthquake with a magnitude greater than 7.0, the bridge has pylons that sink 65 meters into the seabed between the Peloponnesus region and western Greece. Besides being big and tough, Rion-Antirion is quite intelligent, with about 300 sensors spread "almost everywhere" in the structure, says Gilles Hovhanessian, general manager of Advitam SA, Vélizy Cedex, France, the structural monitoring division of one of the builders.
These sensors include strain gauges on gussets to keep track of framework fatigue, displacement transducers in the stay cables that monitor how the bridge blows in the wind, and three-dimensional accelerometers in the bridge roadway to measure the impact of earthquakes. The sensors got an unexpected test when a small quake struck on the day the last stretch of the bridge was installed.
Four acquisition units, one in each pier, collect the sensor data. These linked units are also connected to a central office near the bridge and via the Internet to the operating company near Athens and Advitam's offices in France. Each of the four units can work independently if the connection between them breaks during an earthquake.