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 ...
which links the city of
Kobe
Kobe ( , ; officially , ) is the capital city of Hyōgo Prefecture Japan. With a population around 1.5 million, Kobe is Japan's seventh-largest city and the third-largest port city after Tokyo and Yokohama. It is located in Kansai region, whic ...
on the Japanese island of
Honshu
, historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separ ...
to Iwaya on
Awaji Island. It is part of the
Kobe-Awaji-Naruto Expressway
The is a tolled expressway that connects Hyōgo and Tokushima prefectures in Japan by crossings of the Akashi Strait and Naruto Strait. Built between 1970 and 1998, it is one of the three routes of the Honshu-Shikoku Bridge Expressway Company ...
, and crosses the busy and turbulent
Akashi Strait
The is a strait between the Japanese islands of Honshu and Awaji. The strait connects Seto Inland Sea and Osaka Bay. The width of the Akashi Strait is approximately 4 kilometers, and maximum depth is about 110 meters. The fastest tidal current ...
(''Akashi Kaikyō'' in Japanese). It was completed in 1998,
and has the
second longest central span of any suspension bridge in the world,
at , only behind the
1915 Çanakkale Bridge
The 1915 Çanakkale Bridge ( tr, 1915 Çanakkale Köprüsü), is a road suspension bridge in the province of Çanakkale in northwestern Turkey. Situated just south of the coastal towns of Lapseki and Gelibolu, the bridge spans the Dardanelles st ...
that was opened in March 2022.
It is one of the key links of the
Honshū–Shikoku Bridge Project, which created three routes across the
Inland Sea
An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland se ...
.
History
Background
The Akashi Kaikyo Bridge forms part of the
Kobe-Awaji-Naruto Expressway
The is a tolled expressway that connects Hyōgo and Tokushima prefectures in Japan by crossings of the Akashi Strait and Naruto Strait. Built between 1970 and 1998, it is one of the three routes of the Honshu-Shikoku Bridge Expressway Company ...
, the easternmost route of the
bridge system linking the islands of Honshu and Shikoku.
The bridge crosses the
Akashi Strait
The is a strait between the Japanese islands of Honshu and Awaji. The strait connects Seto Inland Sea and Osaka Bay. The width of the Akashi Strait is approximately 4 kilometers, and maximum depth is about 110 meters. The fastest tidal current ...
(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 on 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 of the largest bri ...
, which links Awaji Island to Ōge Island across the
Naruto Strait
is a strait between Awaji Island and Shikoku in Japan. It connects Harima Nada, the eastern part of the Inland Sea and the Kii Channel. A famous feature of the strait is the Naruto whirlpools. Ōnaruto Bridge, the southern part of the Kobe-A ...
.
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 gale, heavy rain, storms, and natural disasters.
The in 1945, which killed 304 people, first stirred public discussion on the possibility of a bridge over the span. In 1955, two ferries sank in the
Shiun Maru disaster
The was a ship collision in Japan on 11 May 1955, during a school field trip, killing 168 people.
The Shiun Maru ferry sank in the Seto Inland Sea after colliding with another Japanese National Railways (JNR) ferry, the ''Ukō Maru ()'', in ...
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 pref ...
jointly commissioned the
Japan Society of Civil Engineers
is a professional scientific nonprofit organization of the civil engineering field of Japan. It was established as an incorporated association in 1914 and its offices are located in Yotsuya, Shinjuku, Tokyo
Tokyo (; ja, 東京, , ), of ...
(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 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, Nishiseto, and Seto-Chūō expressways and their respective bridges between the islands of Honshu and Shikoku, Japan. It is headquartered in Chūō-ku, Kōb ...
) 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, the construction 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 , or Kobe earthquake, occurred on January 17, 1995, at 05:46:53 JST (January 16 at 20:46:53 UTC) in the southern part of Hyōgo Prefecture, Japan, including the region known as Hanshin. It measured 6.9 on the moment magnitude scale and had ...
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
Crown Prince Naruhito
is the current Emperor of Japan. He acceded to the Chrysanthemum Throne on 1 May 2019, beginning the Reiwa era, following the abdication of his father, Akihito. He is the 126th monarch according to Japan's traditional order of succession.
...
and his spouse
Crown Princess Masako
is as the consort of Emperor Naruhito, who ascended to the Chrysanthemum Throne in 2019. Masako, who was educated at Harvard and Oxford, had a prior career as a diplomat.
Early life and education
was born on 9 December 1963 at Toranomon H ...
of Japan along with Construction Minister Tsutomu Kawara.
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
Roller-compacted concrete (RCC) or rolled concrete (rollcrete) is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for Po ...
, 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 rip raps of 8 m thick.
Superstructures
![Akashi-Bridge-2](https://upload.wikimedia.org/wikipedia/commons/9/92/Akashi-Bridge-2.jpg)
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 , or Kobe earthquake, occurred on January 17, 1995, at 05:46:53 JST (January 16 at 20:46:53 UTC) in the southern part of Hyōgo Prefecture, Japan, including the region known as Hanshin. It measured 6.9 on the moment magnitude scale and had ...
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 damper
A tuned mass damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce mechanical vibrations, consisting of a mass mounted on one or more damped springs. Its oscillation frequency is tuned ...
s that are designed to operate at the
resonance frequency
Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...
of the bridge to dampen 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 tu ...
s in the colors red, green and blue are mounted on the main cables. The
RGB
The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three addi ...
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)
The is a suspension bridge crossing northern Tokyo Bay between Shibaura Pier and the Odaiba waterfront development in Minato, Tokyo, Japan.
It is named ''Tōkyō Kō Renrakukyō'' (東京港連絡橋) as the official name in Japanese.
It was ...
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. Its entries are user-generated content, contribu ...
{{DEFAULTSORT:Akashi-Kaikyo Bridge
1998 in Japan
Articles containing video clips
Bridges completed in 1998
Buildings and structures in Hyōgo Prefecture
Suspension bridges in Japan
Toll bridges in Japan
Tourist attractions in Hyōgo Prefecture