Editing Akashi Kaikyo Bridge

{{Short description|Suspension bridge in Kobe, Japan}}
{{Use mdy dates|date=September 2021}}

{{Infobox bridge
| bridge_name = Akashi Kaikyo Bridge
| native_name = {{nobold|明石海峡大橋}}
| native_name_lang = ja
| image = Akashi Bridge.JPG
| caption = Akashi Kaikyo Bridge from the air, December 2005
| also_known_as = Pearl Bridge<ref name="roadtraffic-technology.com">{{cite web |title=Akashi Kaikyo Bridge, Akashi Strait, Japan |url=http://www.roadtraffic-technology.com/projects/akashi-kaikyo-bridge-strait-japan/ |publisher=Road Traffic Technology |access-date=September 23, 2016 |archive-date=October 2, 2016 |archive-url=https://web.archive.org/web/20161002160336/http://www.roadtraffic-technology.com/projects/akashi-kaikyo-bridge-strait-japan |url-status=live }}</ref>
| carries = Six lanes of the [[File:JP Expressway E28.svg|25px|link=|alt=E28]] [[Kobe-Awaji-Naruto Expressway]] and four emergency lanes
| crosses = [[Akashi Strait]]<ref name=structurae/>
| locale = [[Awaji Island]] and [[Kobe]]<ref name=structurae />
| maint = [[Honshu-Shikoku Bridge Expressway Company|Honshu-Shikoku Bridge Expressway Company Limited]] (JB Honshi Kōsoku)
| id =
| design = [[Suspension bridge]]<ref name=structurae />
| designer = [[Satoshi Kashima]]
| mainspan = <span style="white-space:nowrap">{{convert|1991|m|ft}}</span><ref name=structurae />
| length = <span style="white-space:nowrap">{{convert|3911|m|ft }}</span>
| height ={{convert|282.8|m}} (pylons)<ref name=structurae />
| width =
| clearance =
| below = {{convert|65.72|m}}
| traffic =
| begin = 1988<ref name=structurae />
| complete =1998<ref name=structurae />
| open= April 5, 1998
| closed =
| toll = ¥2,300
| map_cue =
| map_image =
| map_text =
| map_width =
| coordinates = {{coord|34.6162|135.0205|region:JP_type:landmark|display=inline,title}}
}}

The {{nihongo|'''Akashi Kaikyo Bridge'''|明石海峡大橋|Akashi Kaikyō Ōhashi|lead=yes}} is a [[suspension bridge]] that links the city of [[Kobe]] on the Japanese island of [[Honshu]] and {{ill|Iwaya, Awaji|ja|岩屋町}} 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,<ref name=structurae /> and at the time, was the [[List of longest suspension bridge spans|longest central span of any suspension bridge]] in the world,<ref name=hsbe /> at {{convert|1991|m|ft}}. Currently, it is the second-longest, behind the [[1915 Çanakkale Bridge]] 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]].

==History==
===Background===

The Akashi Kaikyo Bridge forms part of the [[Kobe-Awaji-Naruto Expressway]], the easternmost route of the [[Honshū–Shikoku Bridge Project|bridge system linking the islands of Honshu and Shikoku]].<ref name=Ogihara /> The bridge crosses the [[Akashi Strait]] (width 4&nbsp;km) between Kobe on Honshu and Iwaya on [[Awaji Island]]; the other major part of the crossing is completed by the [[Ōnaruto Bridge]], which links Awaji Island to Ōge Island across the [[Naruto Strait]].<ref name=Ogihara />

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.<ref name=":1">{{cite web|access-date=July 29, 2021|title=BUILDING BIG: Databank: Akashi Kaikyo Bridge |url=https://www.pbs.org/wgbh/buildingbig/wonder/structure/akashi_kaikyo.html|website=www.pbs.org|archive-date=December 20, 2020 |archive-url=https://web.archive.org/web/20201220180910/http://www.pbs.org/wgbh/buildingbig/wonder/structure/akashi_kaikyo.html|url-status=live}}</ref> The {{ill|Sekirei Maru sinking|ja|せきれい丸沈没事故}} 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.<ref>{{Cite book |url=https://www.worldcat.org/oclc/674864414 |title=本州四国連絡橋のはなし : 長大橋を架ける |author=Hiroyuki Fujikawa |date=2003 |publisher=交通研究協会 |isbn=4-425-76111-1 |pages=2–5 |trans-title=The story of the Honshu-Shikoku Bridge Project: How the great spans were erected |oclc=674864414 |access-date=July 29, 2021 |archive-date=February 18, 2022 |archive-url=https://web.archive.org/web/20220218202205/https://www.worldcat.org/title/honshu-shikoku-renrakukyo-no-hanashi-chodaikyo-o-kakeru/oclc/674864414 |url-status=live }}</ref>

===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 (Japan)|Ministry of Construction]] in 1959. In 1961, the Ministry of Construction and [[Japan National Railways]] 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.<ref name="Yoshida">{{cite journal |last1=Yoshida |first1=Iwao |title=Basic Survey and Planning of Akashi Kaikyo Bridge |journal=Proceedings of the Japan Society of Civil Engineers |date=1990 |volume=418 |pages=1–15 |language=ja | issn=0289-7806 | doi=10.2208/jscej.1990.418_1 |doi-access=free }}</ref>

In response to the report, the Honshu–Shikoku Bridge Authority (now the [[Honshu-Shikoku Bridge Expressway Company]]<ref name=Ogihara>{{cite book |last1=Ogihara |first1=Katsuya |chapter=Akashi Kaikyo Bridge |editor1-last=Alampalli |editor1-first=Sreenivas |editor2-last=Moreau |editor2-first=William J. |title=Inspection, Evaluation and Maintenance of Suspension Bridges: Case Studies |date=2016 |publisher=CRC Press |location=Boca Raton |pages=40–58 |isbn=9781466596894 |chapter-url=https://books.google.com/books?id=5yXSCgAAQBAJ&pg=PA39 |access-date=September 28, 2021 |archive-date=September 28, 2021 |archive-url=https://web.archive.org/web/20210928060653/https://books.google.com/books?id=5yXSCgAAQBAJ&pg=PA39 |url-status=live }}</ref>) 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.<ref name="Yoshida" />

===Construction===
[[File:Akashi-Kaikyo Bridge h008.jpg|left|thumb|Akashi Kaikyo Bridge, under construction in December 1995]]
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.<ref name=":0" /> The [[Great Hanshin Earthquake]] in January 1995 did not do substantial damage to the bridge due to anti-seismic building methods.<ref name=Ogihara /> Construction was finished on time in September 1996.<ref name=":3">{{Cite journal|last1=Kashima|first1=Satoshi|last2=Kitagawa|first2=Makoto|date=1997|title=The Longest Suspension Bridge|url=https://www.jstor.org/stable/24996048|journal=[[Scientific American]]|volume=277|issue=6|pages=88–92B|doi=10.1038/scientificamerican1297-88|jstor=24996048|bibcode=1997SciAm.277f..88K|issn=0036-8733|access-date=September 29, 2021|archive-date=September 29, 2021|archive-url=https://web.archive.org/web/20210929003831/https://www.jstor.org/stable/24996048|url-status=live}}</ref><ref name="Kyodo News">{{cite web|access-date=July 29, 2021|title=World's longest suspension bridge marks 20 years since opening|url=https://english.kyodonews.net/news/2018/04/d161a56fc707-worlds-longest-suspension-bridge-marks-20-years-since-opening.html|website=Kyodo News+|archive-date=July 29, 2021|archive-url=https://web.archive.org/web/20210729010737/https://english.kyodonews.net/news/2018/04/d161a56fc707-worlds-longest-suspension-bridge-marks-20-years-since-opening.html|url-status=live}}</ref> The bridge was opened for traffic on April 5, 1998, in a ceremony officiated by the [[Naruhito|then-Crown Prince Naruhito]] and his spouse [[Masako, Crown Princess of Japan|Crown Princess Masako]] of Japan along with Construction Minister Tsutomu Kawara.<ref name=":0">{{cite web|last=Cooper|first=James D.|title=World's Longest Suspension Bridge Opens in Japan|url=https://highways.dot.gov/public-roads/julyaugust-1998/worlds-longest-suspension-bridge-opens-japan|work=United States Department of Transportation – Federal Highway Administration|access-date=February 14, 2012|archive-date=January 1, 2012|archive-url=https://web.archive.org/web/20120101152145/http://www.fhwa.dot.gov/publications/publicroads/98julaug/worlds.cfm|url-status=live}}</ref> The bridge was the last Japanese megaprojects of the 20th century.<ref name="longest">{{cite news |title=World's longest suspension bridge |url=https://eresources.nlb.gov.sg/newspapers/digitised/article/straitstimes19980406-1.2.24.4?qt=kaikyo,%20bridge&q=kaikyo%20bridge |work=The Straits Times |agency=AFP |date=April 6, 1998}}</ref>

==Structure==

===Substructures===
[[File:Akashi Kaikyo Bridge Maiko Hyogo Japan (19175872663).jpg|thumb|The illuminated Akashi Kaikyo Bridge as seen from [[Osaka]], 2006.]]
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 [[Shallow foundation|spread-foundation]] [[Caisson (engineering)|caisson]] structures, and 4A is a rectangular direct foundation.<ref name=Ogihara /> 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.<ref name=Ogihara />

[[File:Akashikaikyobridge-sunnyday-fromriver2013.ogv|thumbtime=5|thumb|Video of the bridge, as seen from a ship passing underneath]]

The towers are located in an area of strong tidal currents where water velocity exceeds 7 knots (about 3.6&nbsp;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.<ref name=":2">{{Cite journal|others=Satoshi Kashima, Mitsushige Sakamoto, Yukihiro Sano, Kozoo Higuchi|title=Construction of Akashi Kaikyo bridge foundation|url=https://dx.doi.org/10.5169/seals-59833|url-status=live|access-date=September 29, 2021|website=E-Periodica | publisher=IABSE |year=1998|doi=10.5169/seals-59833|archive-date=February 18, 2022|archive-url=https://web.archive.org/web/20220218202158/https://www.e-periodica.ch/digbib/view?pid=bse-re-003:1998:79::84}}</ref>

===Superstructures===

[[File:Akashi-Bridge-2.jpg|upright|thumb|Main supporting towers]]

The bridge has three [[Span (architecture)|spans]]. The central span is {{convert|1991|m|ft|abbr=on}},<ref name=structurae /> and the two other sections are each {{convert|960|m|ft |abbr=on}}. The bridge is {{convert|3911|m|ft |abbr=on}} long overall. The two towers were originally {{convert|1990|m|ft|abbr=on}} apart, but the [[Great Hanshin earthquake]] on January 17, 1995 (magnitude 7.3, with epicenter 20&nbsp;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 {{convert|1|m|ft|1|abbr=on}}.<ref name=structurae /> 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.<ref name=Ogihara />

The bridge was designed with a dual-hinged stiffening girder system, allowing the structure to withstand winds of {{convert|286|km/h|mph|0}}, earthquakes measuring up to magnitude 8.5, and harsh sea currents. The bridge also contains [[tuned mass damper]]s that are designed to operate at the [[resonance|resonance frequency]] of the bridge to damp forces. The two main supporting towers rise {{convert|282.8|m|ft|abbr=on}} above sea level, and the bridge can expand because of heat by up to {{convert|2|m|ft|abbr=on}} over the course of a day.<ref name=":1" /> Each anchorage required {{convert|350000|t}} of concrete. The steel cables have {{convert|300000|km}} of wire: each cable is {{convert|112|cm}} in diameter and contains 36,830 strands of wire.<ref name="structurae" /><ref name=":3" />

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]]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 [[Public holidays in Japan|national or regional holidays]], memorial days or festivities.<ref>{{cite web | url = http://www.roadtraffic-technology.com/projects/akashi-kaikyo-bridge-strait-japan/ | access-date = April 26, 2015 | title = Akashi Kaikyo Bridge, Akashi Strait, Japan | archive-date = April 20, 2015 | archive-url = https://web.archive.org/web/20150420105515/http://www.roadtraffic-technology.com/projects/akashi-kaikyo-bridge-strait-japan/ | url-status = live }}</ref>

{{Comparison_of_notable_bridges.svg|Note:=The Great Belt bridge in Denmark is missing from the interactive comparison, but it is the third longest in the world and the longest in Europe (1.6 km)}}

{{Clear|left}}

==Cost==
The total cost is estimated at [[Japanese yen|¥]]500 billion or US$3.6 billion (per 1998 exchange rates).<ref name=":0" /> 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.<ref name="roadtraffic-technology.com"/>

== See also ==
* [[Rainbow Bridge (Tokyo)]]

== References ==
{{Reflist|refs=
<ref name=structurae>[http://structurae.net/structures/akashi-kaikyo-bridge Akashi Kaikyo Bridge] {{Webarchive|url=https://web.archive.org/web/20150930173727/http://structurae.net/structures/akashi-kaikyo-bridge |date=September 30, 2015 }} at ''[[Structurae]]''<!--{{Structurae|id=20000001|name=Akashi Kaikyo Bridge}}--></ref>
<ref name=hsbe>[http://www.jb-honshi.co.jp/english/technology/akashi.html Akashi-Kaikyo Bridge] {{Webarchive|url=https://web.archive.org/web/20120630132040/http://www.jb-honshi.co.jp/english/technology/akashi.html |date=June 30, 2012 }} – HSBE</ref>
<!--<ref name=everything2>[http://everything2.com/title/Akashi%2520Kaikyo%2520Bridge Akashi Kaikyo Bridge] at [[everything2]]{{Self-published source|date=September 2014}}</ref>-->
}}

==External links==
{{Commons}}
* [http://structurae.net/structures/akashi-kaikyo-bridge Akashi Kaikyo Bridge] at [[Structurae]]<!--{{Structurae|id=20000001|name=Akashi Kaikyo Bridge}}-->

{{LongestBridge
| type = suspension
| start = 1998
| end = 2022
| previous = Humber Bridge
| current = Akashi Kaikyo Bridge
| next = 1915 Çanakkale Bridge
}}
{{Crossings navbox
|structure       = Crossings
|place           = [[Honshū-Shikoku Bridge Project#Kobe-Awaji-Naruto Expressway|Kobe–Awaji–Naruto Expressway]]
|bridge          = Akashi Kaikyo Bridge
|bridge signs    =
|upstream text   = North
|upstream        = [[Honshū]]
|upstream signs  =
|downstream text = South
|downstream      = [[Ōnaruto Bridge]]
|downstream signs =
}}

{{Authority control}}

{{DEFAULTSORT:Akashi-Kaikyo Bridge}}
[[Category:1998 establishments in Japan]]
[[Category:Articles containing video clips]]
[[Category:Bridges completed in 1998]]
[[Category:Buildings and structures in Kobe]]
[[Category:Buildings and structures in Awaji, Hyōgo]]
[[Category:Transport in Kobe]]
[[Category:Bridges in Hyōgo Prefecture]]
[[Category:Suspension bridges in Japan]]
[[Category:Toll bridges in Japan]]
[[Category:Tourist attractions in Kobe]]
[[Category:Cross-sea bridges in Asia]]