World’s Longest Sea Bridge

World’s Longest Sea Bridge  
Filed under:
on 02/17/2010


Hangzhou Bay Bridge - World’s Longest Sea Bridge (Photo: ABC News Australia)Hangzhou Bay Bridge - World’s Longest Sea BridgeHangzhou Bay Bridge - World’s Longest Sea BridgeHangzhou Bay Bridge - World’s Longest Sea BridgeHangzhou Bay Bridge - World’s Longest Sea Bridge

The world’s longest sea bridge is the Hangzhou Bay Bridge, which was opened for public use in 2008. This fantastic bridge is a stayed cable bridge that offers an S shape and 6 lanes that go in both directions. The bridge connects Cixi county to Jiaxing, and is a total of 22 miles or 36 kilometers in length.

The distance between Shanghai and Ningbo is shortened by taking this route by almost 120 km. The bridge is believed to have a lifespan of about 100 years and cost over $1.7 billion to build, or 11.8 billion Yuan. There is a toll fee to cross the Hangzhou Bay Bridge, which is 80 Yuan for each vehicle, and the speed limit is 62 miles per hour or 100 km per hour.

When preparing for the construction of the bridge, almost 600 experts went to work on the design. The chief commander of the bridge project stated that the bridge was to be linked in 2007, but a year later after many tests the bridge was then opened due to safety issues. The Hangzhou Bay Bridge has only a portion that is cable stayed which is from the Hangzhou Bay into the eastern portions of China. This bridge is considered the longest to cover an ocean, but is not the longest cable stayed main span bridge; this title goes to the Lake Pontchartrain Causeway in the United States because it is almost 3 km longer.

The travel time between Ningbo and Shanghai was shortened by an hour and a half by using the bridge, and took off 120 km or 75 miles from the trip. In the center of the bridge, construction is in talks for a service center that will cover 10,000 square meters. This area will have a restaurant, rest area, gas station, conference area and a hotel with a lookout tower for tourists. This service center is believed to be in the works to be built on a small island and platform on top of piers in the Bay. On either side of the bridge, public parks are also in talks but there are no immediate plans.

The Hangzhou Bay Bridge was first conceived in 1994 and construction actually did not begin until 2003 and was finally opened to the public in 2008. The bridge is estimated to have carried a minimum of 50,000 vehicles a day from one section to the other. The chief director of the project is said to have thought that this bridge is one of the three largest on earth and is built in one of the worst sea environments for a bridge, since typhoons and sea soil are drastically different in this area of the world.

There were many investment partners in the bridge project, including a total of 59% of the money coming from loans from China’s regional banks and 35% of the money coming from private companies in the area of Ningbo. The main reason for the bridge’s construction was to help bring more development to the Yangtze river delta and increase the economic power China has. This bridge created not only a way for traffic networks to be combined in two areas, but also a way of creating relations between the two business districts on either end of the bridge.

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The bridge is built in the East China Sea gulf of Hnagzhou Bay, where the Qiantang River Tide makes large waves and extremely fast waters. This area is highly prone to typhoons, and all of these were reasons for concern when building and planning the project.

The cable stayed design was chosen because it is able to hold up under the conditions of weather that the area is known for, and has been created for seismic criterion so that it holds integrity in the event of an earthquake of up to a 7.0. Each of the 3 lanes going each direction measure a total of 3.75 km in width and the total width of the bridge spans 33 meters. The grade at the cross slope is only a 2% while there is a maximum of a 4% longitude slope. The speed limits are posted at 100 km per hour for the main drags, while land approaches have a speed limit of 120 lm per hour. The total height of the bridge is 62 meters, so that container ships are still able to pass through beneath regardless of water conditions. The total amount of cable used for the project was 32.2 km.

The construction mostly took place on land and was then moved into the water after completion. One of the many challenges while building the bridge was the fact that many eruptions of natural gas in shallow layers along the line of the bridge were taking place. A team of experts was brought in and they conducted experiments and found that they could release the gas before pile driving, therefore causing no disturbance to the soil and the ground would no longer collapse. In construction, floating cranes and anchors as well as launching gantries were used to ship and place the girders in the sea bed. The shore seen construction taking place on mudflats on the south shores and a temporary trestle was created for creating the piers. Bad water conditions caused problems with anchoring the barges and other construction ships. The bad tidal flow and typhoons caused flow currents from 2 to 3.3 m per second at the sites on either end of the would be bridge.

The entire Hangzhou Bay Bridge is constructed of 9 separate sections, with the first being a lead road to the north end approach. The north end approach lies on piers and is made up of many concrete girders and leads to the bridge. The most notable sight on the bridge at this time are the two diamond shaped towers that sit directly in the middle of the site. For GPS monitoring, the construction crew used te Trimble 5700 RTK system and is still set up where the bridge crosses the Hangzhou Bay.

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