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
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.
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.
Difference the bridge has made
Many technical innovations were trialled and employed in the bridge’s construction. These include:
- a new construction method for big, deep foundations
- a highly workable concrete with low-heat cement
- high-strength wires for the main cables
- construction of a large wind tunnel (including a full bridge model test)
The bridge has also provided safe passage between the islands.
Previously, a ferry service had to face frequent sea storms as it travelled across the strait.
These storms were so dangerous that in 1955, two crossing ferries sank, resulting in the deaths of 168 people.
This makes the bridge one of the civil engineering projects changing the world.