Akashi Kaikyo Bridge

Honshu and Awaji, Japan

Year

1988-98

Duration

10 years

Cost

¥500bn

Location

Japan

Project achievements

Solved the problem

Replaced a ferry crossing that was vulnerable to severe sea storms

Used engineering skill

Uses two strong girder systems (structural supports) to make it resilient to earthquakes, typhoons and sea currents

Connected communities

Provides safe crossing between Honshu and Awaji Island

Building a suspension bridge that can withstand typhoons and earthquakes

The Akashi Kaikyo Bridge is a 3.9km-long suspension bridge connecting Kōbe, in mainland Honshu, and Iwaya, on Awaji Island, in west-central Japan.

When it first opened for use in 1998, it was the longest suspension bridge in the world.

The central span is 1991m long, with the end spans coming in at 960m each.

Forming part of the Honshu-Shikoku Highway, the six-lane road bridge crosses over the Akashi Strait, known for its rapid tidal current (4.2m/s) and high levels of sea traffic.

The strait is also located in an area vulnerable to seismic events and severe sea storms.

As such, the bridge has been built to withstand typhoons of 290kph and earthquakes with a magnitude of up to 8.5 on the Richter scale.

Meeting these challenges led to innovations in wind-tunnel and cable-fabrication technology.

Image credit: Shutterstock

Akashi Kaikyo Bridge

The bridge illuminated in rainbow lights at night.

Did you know …

The foundation depth of the bridge is the same as that of a 20-storey flat.
Due to heat, the bridge can expand and contract up to 2m in a single day.
The bridge is lit up by more than 1,700 lights. The view of the illuminated bridge at night has earned it the nickname of ‘Pearl Bridge’.

How the bridge was built

Engineers had to work around complicated building conditions.

A deep, soft layer had to be penetrated for the anchorage foundations, and they had to contend with water depth of 45m, tidal currents of 4m/s and strong winds of 80m/s.

To ensure the bridge could withstand the effects of typhoons and earthquakes, the engineers developed a ‘complex system of counterweights, pendulums, and steel-truss girders’.

The tower pier's foundation was built with the ability to transmit 181,400 tonnes of vertical force to the bed rock, approximately 60m below water.

This required a new laying down caisson (a boxlike retaining structure) method, where steel caissons were drawn onto the tower sites, submerged and set on the seabed.

The main cables of the bridge were placed using full-length prefabricated strands.

The main towers, coming in at 282.8m of height, were built by stacking approximately 30 prefabricated steel segments on top of each other.

In total, the project used 181,400 tonnes of steel.