The Akashi Kaikyo Bridge in Japan is an engineering marvel and record-breaker. This impressive bridge is not only very long, but it has been designed to withstand earthquakes up to 8.5 on the Richter scale!
Here we explore why she was built, and see how engineers overcame the significant technical challenges needed to complete her. We'll also finish up with some handy takeaway facts about this incredibly long, and tall marvel of civil engineering.
What is the Akashi Kaikyo Bridge made out of?
Akashi Kaikyo Bridge also called the Akashi Strait bridge or Pearl Bridge is one of the world's longest suspension bridges across the Akash Strait in west-central Japan. When it first opened in 1998, it was the world's longest bridge at the time.
Before her completion, boats and ferries were used to transport passengers and vehicles across the Akashi Strait. This is an international waterway that is approximately 1,500 meters wide and is a busy shipping lane.
Prior to the bridge's construction, it was considered one of the world's most dangerous waterways. For example, in 1955 a severe storm caused two ferries to sink resulting in the deaths of 168 people.
As a result, the Japanese government decided the strait needed a suspension bridge to cross the strait. Originally, the plan was to construct a railway along with a road bridge. But the construction was finally restricted to a road bridge.
It is a substantial 6-lane road bridge that connects Kobe on the main island of Honshu with Iwyaya on the smaller Japanese island of Awaji. This, in turn, is linked to the island of Shikoku to the SW via the Ōnaruto Bridge over the Naruto Strait.
These two bridges, along with the Seto Great Bridge, between Kojima on Honshu and Sakaide on Shikoku, form the main parts of the Honshu-Shikoku Bridge Project across Japan’s Inland Sea.
The bridge is 3,911 meters long, has three spans supported by two main supporting towers that stand 297 meters apiece and a series of anchoring cables. This makes Akashi Kaikyo Bridge also one of the world's tallest.
The towers needed to be tall enough to anchor the cabling required to support the spans, but also tall enough to allow boat traffic pass unimpeded below her.
Her central span had originally been planned to be 1,900 meters long, but plans were revised following the 1995 Kobe earthquake forced the towers (that were under construction) apart by around 1 meter making it 1,991 meters today.
As the bridge stands in a seismically unstable part of the world, engineers needed to ensure her design would stand the test of time. To this end, her design includes a complex system of counterweights, pendulums, and steel-truss girders that allow the bridge to withstand wind speeds of up to 290 km/h. Yet despite her inherent strength, the bridge is also able to expand and contract several times a day.
"In addition, engineers placed 20 tuned mass dampers (TMDs) in each tower. The TMDs swing in the opposite direction of the wind sway. So when the wind blows the bridge in one direction, the TMDs sway in the opposite direction, effectively "balancing" the bridge and canceling out the sway. With this design, the Akashi Kaikyo can handle 180-mile-per-hour winds, and it can withstand an earthquake with a magnitude of up to 8.5 on the Richter scale." - PBS Online.
Why is the Akashi Kaikyo Bridge called the Pearl Bridge?
According to sites like Feel Kobe, The Akashi Kaikyo Bridge is called the 'Pearl Bridge' because of the 28 different patterns and various colors of lights used to illuminate her at night. To locals, this is reminiscent of the appearance of beautiful pearls on a necklace.
How much did the Akashi Kaikyo Bridge cost?
The Akashi Kaikyo Bridge cost an estimated 500 billion Japanese Yen (roughly $3.6 billion) to construct. The project started in 1988 and included over 100 different contractors to finally complete the suspension bridge.
It is estimated that it took over 2 million workers, 180,000 tonnes of steel and 1.4 million cubic meters of concrete to complete the bridge. This makes her one of the strongest, longest and most expensive suspension bridges ever conceived.
It took roughly ten years to complete and was designed by the Honshu Shikoku Bridge Authority.
What are the 5 longest suspension bridges in the world?
As impressive as the Akashi Kaikyo Bridge is, it is only one of the world's longest suspension bridges. Some of the other longest suspension bridges include, but are not limited to: -
- Akashi Kaikyo/Pearl Bridge in Japan.
- Golden Gate Bridge in California.
- George Washington Bridge in New York.
- Danyang-Kunshan Grand Bridge in China.
- Xihoumen Bridge in China.
7 takeaway facts about Akashi Kaikyo Bridge in Japan
1. The Akashi Kaikyo Bridge is both one of the longest and tallest bridges in the world.
2. Roughly 300,000 kilometers of cabling was used in the bridge's construction.
3. The bridge has been designed to withstand earthquakes and the harsh sea conditions of the area. Her resilience was tested before she was even completed when her incomplete structure survived the 1995 Kobe earthquake. The earthquake measured 6.9 on the Richter scale. Since she is built near the so-called "Ring of Fire", the Kobe earthquake is unlikely to be the last time the bridge will need to resist the forces of nature.
4. The bridge is used by around 25,000 cars everyday ad it has become a tourist attraction.
5. Construction began in the late 1980s, and took ten years, millions of workers and 180,000 tonnes of steel and 1.4 million cubic meters of concrete to complete.
6. Her central span was originally designed to be 1,990 meters long, but this needed to be amended by 1 meter following the 1995 Kobe earthquake.
7. Prior to the bridge's construction, the Akashi Strait was one of the most dangerous waterways in the world.