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.

Brooklyn Bridge

Brief information

Location: Manhattan and Brooklyn, New York, USA

Completion Date: 1883

Cost: $18 million

Length: 3,460 feet

Type: Suspension

Purpose: Roadway

Materials: Steel, granite

Longest Single Span: 1,595 feet

Engineer(s): John A. Roebling, Washington A. Roebling

Considered a brilliant feat of 19th-century engineering, the Brooklyn Bridge was a bridge of many firsts. It was the first suspension bridge to use steel for its cable wire. It was the first bridge to use explosives in a dangerous underwater device called a caisson. At the time it was built, the 3,460-foot Brooklyn Bridge was also crowned the longest suspension bridge in the world. But the Brooklyn Bridge was plagued with its share of problems. Before construction even began, the bridge's chief engineer, John A. Roebling, died from tetanus. The project was taken over and seen to its completion by his son, Washington Roebling. Three years later, Roebling developed a crippling illness called caisson's disease, known today as "the bends." Bedridden but determined to stay in charge, Roebling used a telescope to keep watch over the bridge's progress. He dictated instructions to his wife, Emily, who passed on his orders to the workers. During this time, an unexpected blast wrecked one caisson, a fire damaged another, and a cable snapped from its anchorage and crashed into the river.

Despite these problems, construction continued at a feverish pace. By 1883, 14 years after it began, Roebling successfully guided the completion of one of the most famous bridges in the world -- without ever leaving his apartment.

Fast Facts:

1. Although he was physically able to leave his apartment, Washington Roebling refused to attend the opening celebration honoring his remarkable achievement.

2. The bridge opened to the public on May 24, 1883, at 2:00 p.m. A total of 150,300 people crossed the bridge on opening day. Each person was charged one cent to cross.

3. The bridge opened to vehicles on May 24, 1883, at 5:00 p.m. A total of 1,800 vehicles crossed on the first day. Vehicles were charged five cents to cross. Today, the Brooklyn Bridge is the second busiest bridge in New York City. One hundred forty-four thousand vehicles cross the bridge every day.