Day 362/365 of Steel – Akashi Kaikyo Bridge

Another world record in bridge engineering.

On April 5, 1998, the ribbon was cut to open the world’s longest suspension bridge, the Akashi Kaikyo Bridge in Japan. It has a world record main span of 1,991 meters. This bridge crosses the Akashi Straits, connecting the Kobe area of Honshu with Awaji Island, the sixth largest island in Japan. The bridge is 3,911 m long overall.

Akashi-Kaikyō Bridge, Japan
Fig 1: Akashi-Kaikyō Bridge, Japan
Photo: Public Domain

The bridge roadway surface is constructed on top of a 14-meter-deep by 35.5-meter-wide truss girder system suspended from main cables passing over two steel towers that rise 298 meters above main sea level. Approximately 181,400 metric tons of steel were used in the superstructure.

The bridge has three spans. The central span is 1,991 m and the two other sections are each 960 m. The Kobe earthquake on January 17, 1995 had its epicentre just between the two towers of the Akashi Kaikyo Bridge. The initial length was 1.990 meters planned for the main span, but the quake moved the towers 1 meter separating, when they had not started construction of the deck yet.

Akashi-Kaikyō Bridge, Japan
Fig 2: Akashi-Kaikyō Bridge, Japan
Photo: Kzaral

The bridge was designed with a dual-hinged stiffening girder system, allowing the structure to withstand winds of 286 kilometres per hour, earthquakes measuring up to magnitude 8.5, and harsh sea currents. The bridge deck is placed on a support frame formed by a complex network of triangular support below the road. The open network of triangles gives rigidity to the bridge and also allows the wind to pass through the structure.

The bridge also contains tuned mass dampers that are designed to operate at the resonance frequency of the bridge to dampen forces. The steel cables have 300,000 kilometres of wire: each cable is 112 centimetres in diameter and contains 36,830 strands of wire. Each main-tower height was erected by stacking 30 approximately 10-meter-high prefabricated steel segments on top of each other.

About the Author:

Bruno Dursin – Managing Director at Believe in Steel. Bruno has more than 30 years of experience in promoting steel & steel solutions. His clients benefit from his extensive network within the building industry.

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