Text 3: Akashi Kaikyo Bridge

Lead-in:

1. What can the Akashi Kaikyo Bridge be famous for?

2. What is the purpose of the bridge?

3. What country does it present?

Brief information

Location: Kobe and Awaji-shima, Japan

Completion Date: 1998

Cost: $4.3 billion

Length: 12,828 feet

Type: Suspension

Purpose: Roadway

Materials: Steel

Longest Single Span: 6,527 feet

Engineer(s): Honshu-Shikoku Bridge Authority

In 1998, Japanese engineers stretched the limits of bridge engineering with the completion of the Akashi Kaikyo Bridge. Currently the longest spanning suspension bridge in the world, the Akashi Kaiko Bridge stretches 12,828 feet across the Akashi Strait to link the city of Kobe with Awaji-shima Island. It would take four Brooklyn Bridges to span the same distance! The Akashi Kaikyo Bridge isn't just long -- it's also extremely tall. Its two towers, at 928 feet, soar higher than any other bridge towers in the world. The Akashi Strait is a busy shipping port, so engineers had to design a bridge that would not block shipping traffic. They also had to consider the weather. Japan experiences some of the worst weather on the planet. Gale winds whip through the Strait. Rain pours down at a rate of 57 inches per year. Hurricanes, tsunamis, and earthquakes rattle and thrash the island almost annually. How did the Japanese engineers get around these problems? They supported their bridge with a truss, or complex network of triangular braces, beneath the roadway. The open network of triangles makes the bridge very rigid, but it also allows the wind to blow right through the structure. 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!

Fast Facts:

1. The bridge is so long, it would take eight Sears Towers laid end to end to span the same distance.

2. The length of the cables used in the bridge totals 300,000 kilometers. That's enough to circle the earth 7.5 times!

3. The bridge was originally designed to be 12,825 feet. But on January 17, 1995, the Great Hanshin Earthquake stretched the bridge an additional three feet.

4. The bridge holds three records: it is the longest, tallest, and most expensive suspension bridge ever built.

COMPREHENSION CHECK:

I. Decide whether the following statements are true or false according to the text:

1. The Akashi Kaiko Bridge is the longest spanning cable-stayed bridge in the world.

2. The Akashi Kaiko Bridge being the longest blocks shipping traffic sometimes.

3. A complex network of triangular braces doesn’t let the wind to blow through the structure.

4. The bridge is supported with a truss.

5. The TMDs help balancing the bridge.

6. Being the longest and the highest the Akashi Kaiko Bridge can’t resist an earthquake

II. Answer the following questions:

1.What records does the Akashi Kaiko Bridge hold? Prove it with numbers.

2. What did engineers have to consider building the bridge?

3. How did engineers cope with problems they encountered?

4. What are tuned mass dampers? How do they work?

5. How strong is the bridge?