Japan’s Akashi Kaikyō bridge is part of three crossings that connect the northern and southern shores of the Seto Inland Sea. It connects the city of Kobe with Iwaya on the island of Awaji. The suspension bridge has the longest central span in the world, at 1,991 metres (6,532 ft). Each of the two other sections measure 960 m (3,150 ft). Construction began in May of 1988, and was opened to traffic on April 5, 1998, but had been discussed for decades prior. The Akashi Strait, an important international shipping channel connecting the Pacific Ocean to the Sea of Japan, was only crossed by ferry up until the completion of the Akashi Kaikyō bridge and its Honshū-Shikoku Bridge Project counterparts. In 1955 two ferries collided and sank in a storm, killing 168 people. The ensuing public outrage at the disaster prompted the Japanese government into considering a suspension bridge to cross the strait. Originally the plans had included a rail as well as road crossing, but by the time they came to fruition, the railway was no longer included.
The bridge uses enough steel wire (300,000 kilometers, 190,000 miles) to encircle the world 7.5 times, and is suspended from two towers that rise 298 meters / 978 feet from sea level. The design of the bridge is intended to withstand winds of up to 286 kph / 178 mph and earthquakes up to 8.5 on the Richter scale. The latter was tested before the bridge was even completed – what became known as the Great Hanshin earthquake (or the Kobe earthquake outside Japan), struck January 17, 1995, resulting in the central span needing an extra 3.3 feet (1 meter) in length than the design originally called for. To aid the structure in such extreme forces of nature, each tower houses 20 pendulums or tuned mass dampers, which swing opposite to the wind direction to balance the bridge and cancel out the sway.
To learn more about civil engineering projects from around the world, visit the People and Projects section of the ASCE website.