The is a
suspension bridge
A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...
that links the city of
Kobe
Kobe ( ; , ), officially , is the capital city of Hyōgo Prefecture, Japan. With a population of around 1.5 million, Kobe is Japan's List of Japanese cities by population, seventh-largest city and the third-largest port city after Port of Toky ...
on the Japanese island of
Honshu
, historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...
and on
Awaji Island. It is part of the
Kobe-Awaji-Naruto Expressway, and crosses the busy and turbulent
Akashi Strait (''Akashi Kaikyō'' in Japanese). It was completed in 1998,
and at the time, was the
longest central span of any suspension bridge in the world,
at . Currently, it is the second-longest, behind the
1915 Çanakkale Bridge
The 1915 Çanakkale Bridge () is a road suspension bridge in the province of Çanakkale Province, Çanakkale in northwestern Turkey. Situated just south of the coastal towns of Lapseki and Gelibolu, the bridge spans the Dardanelles, about sout ...
in Turkey that was opened in March 2022.
The Akashi Kaikyo Bridge is one of the key links of the
Honshū–Shikoku Bridge Project, which created three routes across the
Seto Inland Sea
The , sometimes shortened to the Inland Sea, is the body of water separating Honshu, Shikoku, and Kyushu, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka Ba ...
.
History
Background
The Akashi Kaikyo Bridge forms part of the
Kobe-Awaji-Naruto Expressway, the easternmost route of the
bridge system linking the islands of Honshu and Shikoku.
The bridge crosses the
Akashi Strait (width 4 km) between Kobe on Honshu and Iwaya on
Awaji Island; the other major part of the crossing is completed by the
Ōnaruto Bridge
The is a suspension bridge that carries 4 lanes of the Kobe-Awaji-Naruto Expressway connecting Minamiawaji, Hyogo on Awaji Island with Naruto, Tokushima on Ōge Island, Japan. Completed in 1985, it has a main span of . Although it is one ...
, which links Awaji Island to Ōge Island across the
Naruto Strait.
Before the Akashi Kaikyo Bridge was built, ferries carried passengers across the Akashi Strait. A major passageway for shipping, it is also known for its gales, heavy rain, storms, and other natural disasters.
The in stormy weather in December 1945, while carrying more than three times its capacity of 100 passengers, killed 304 people, first stirring public discussion on the possibility of a bridge over the span. In 1955, two ferries sank in the
Shiun Maru disaster during a storm, killing 168 people. The ensuing shock and public outrage convinced the Japanese government to develop plans for a bridge to cross the strait.
Investigations
Investigations for a bridge across the strait were first conducted by the Kobe municipal government in 1957, followed by an evaluation by the national
Ministry of Construction in 1959. In 1961, the Ministry of Construction and
Japan National Railways
The , abbreviated JNR or , was the business entity that operated Japan's national railway network from 1949 to 1987.
Network Railways
As of June 1, 1949, the date of establishment of JNR, it operated of narrow gauge () railways in all 46 pre ...
jointly commissioned the
Japan Society of Civil Engineers (JSCE) to conduct a technical study, and the JSCE established a committee to investigate five potential routes between Honshu and Shikoku. In 1967, the committee compiled the results of the technical study, concluding that a bridge across the Akashi Strait would face "extremely severe design and construction conditions, which have no similar examples in the world's long-span bridges" and recommending an additional study.
In response to the report, the Honshu–Shikoku Bridge Authority (now the
Honshu-Shikoku Bridge Expressway Company
The , abbreviated as in Japanese or HSBE in English, operates the Kobe-Awaji-Naruto Expressway, Kobe-Awaji-Naruto, Nishiseto Expressway, Nishiseto, and Seto-Chūō Expressway, Seto-Chūō Expressways of Japan, expressways and Honshū-Shikoku Bri ...
) was established in 1970, which conducted extensive investigations, including sea trials to establish the construction method of a submarine foundation. In 1973, a bridge with a central span of 1,780 meters on the route was approved, but construction was halted due to poor economic conditions.
Construction

The original plan called for a mixed railway-road bridge, but when construction on the bridge began in April 1988, it was restricted to road only, with six lanes. Actual construction did not begin until May 1988 and involved more than 100 contractors.
The
Great Hanshin Earthquake
The Great Hanshin Earthquake (, ) occurred on January 17, 1995, at 05:46:53 JST in the southern part of Hyōgo Prefecture, Japan, including the region of Hanshin. It measured 6.9 on the moment magnitude scale and had a maximum intensity of 7 o ...
in January 1995 did not do substantial damage to the bridge due to anti-seismic building methods.
Construction was finished on time in September 1996.
The bridge was opened for traffic on April 5, 1998, in a ceremony officiated by the
then-Crown Prince Naruhito and his spouse
Crown Princess Masako of Japan along with Construction Minister Tsutomu Kawara.
The bridge was the last Japanese megaprojects of the 20th century.
Structure
Substructures
The bridge has four substructures: two main piers (located beneath the water) and two anchorages (on land). These are denoted 1A, 2P, 3P, and 4A in sequence from the Kobe side. 1A consists of an underground circular retaining wall filled with
roller-compacted concrete, 2P and 3P are circular underwater
spread-foundation caisson structures, and 4A is a rectangular direct foundation.
2P is located at the edge of the sea plateau at a level depth of 40–50 m and a bearing depth of 60 m, and 3P is located at the symmetrical point to 2P with respect to the bridge's center, at a level depth of 36–39 m and a bearing depth of 57 m.
The towers are located in an area of strong tidal currents where water velocity exceeds 7 knots (about 3.6 m/s). The selected scour protection measure includes the installation of a filtering layer with a thickness of 2 m in a range of 10 m around the caisson, covered with
riprap of 8 m thick.
Superstructures

The bridge has three
spans. The central span is ,
and the two other sections are each . The bridge is long overall. The two towers were originally apart, but the
Great Hanshin earthquake
The Great Hanshin Earthquake (, ) occurred on January 17, 1995, at 05:46:53 JST in the southern part of Hyōgo Prefecture, Japan, including the region of Hanshin. It measured 6.9 on the moment magnitude scale and had a maximum intensity of 7 o ...
on January 17, 1995 (magnitude 7.3, with epicenter 20 km west of Kobe) moved the towers (the only structures that had been erected at the time) such that the central span had to be increased by .
The central span was required to be greater than 1,500 m to accommodate maritime traffic; it was concluded before construction began that a larger span between 1950 and 2050 meters would minimize construction costs.
The bridge was designed with a dual-hinged stiffening girder system, allowing the structure to withstand winds of , earthquakes measuring up to magnitude 8.5, and harsh sea currents. The bridge also contains
tuned mass dampers that are designed to operate at the
resonance frequency of the bridge to damp forces. The two main supporting towers rise above sea level, and the bridge can expand because of heat by up to over the course of a day.
Each anchorage required of concrete. The steel cables have of wire: each cable is in diameter and contains 36,830 strands of wire.
The Akashi–Kaikyo bridge has a total of 1,737 illumination lights: 1,084 for the main cables, 116 for the main towers, 405 for the girders and 132 for the anchorages. Sets of three
high-intensity discharge lamp
High-intensity discharge lamps (HID lamps) are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc ...
s in the colors red, green and blue are mounted on the main cables. The
RGB color model and computer technology make for a variety of combinations. Twenty-eight patterns are used for occasions such as
national or regional holidays, memorial days or festivities.
Cost
The total cost is estimated at
¥500 billion or US$3.6 billion (per 1998 exchange rates).
It is expected to be repaid by charging drivers a toll to cross the bridge. The toll is 2,300 yen and the bridge is used by approximately 23,000 cars per day.
See also
*
Rainbow Bridge (Tokyo)
References
External links
Akashi Kaikyo Bridgeat
Structurae
Structurae is an online database containing pictures and information about structural engineering, structural and civil engineering works, and their associated engineers, architects, and builders.
Overview
Structurae was founded in 1998 by Nico ...
{{DEFAULTSORT:Akashi-Kaikyo Bridge
1998 establishments in Japan
Articles containing video clips
Bridges completed in 1998
Buildings and structures in Kobe
Buildings and structures in Awaji, Hyōgo
Transport in Kobe
Bridges in Hyōgo Prefecture
Suspension bridges in Japan
Toll bridges in Japan
Tourist attractions in Kobe
Cross-sea bridges in Asia