A bridge is defined as any structure that is built to move people or goods over an obstacle, like water, another road, or harsh terrain. Consequently there are hundreds of thousands of bridges all over the world that vary in design, function and size. The earliest bridges took the form of logs felled to cross a stream, or stones moved into place.
In a list of the world’s longest bridges, China, who loves world records, would dominate the list. Instead I’ve focused on a variety of categories including rail bridges, floating bridges, sea bridges and even inhabited bridges, to give a cross section of the longest.
The Longest Bridge in the world (of any sort)
The Danyang-Kunshan Grand Bridge in China, is the world’s longest, at 164.8 kilometres (102.4 miles) long; almost as far as London to Calais. It is a viaduct on the Beijing-Shanghai High-Speed Railway and is built over land characterised by the lowland rice paddies of the Yangtze River Delta, canals, rivers and lakes. The bridge opened in June 2011 when it jumped into the Guinness Book of Records, and was built in just 4 years, employing 10,000 workers, at a cost of about $8.5 million. The average height off the ground is about 100 feet (31 metres). Another part of the same rail line is the 114km (70.8 mile) Langfang-Qingxian viaduct.
The Longest Suspension Bridge Span
The relative lengths of suspension bridges are measured and compared using the unsupported distance between the bridge towers. For engineering reasons span distances are correlated to the height of their towers and the complexity of their design and construction.
The Akashi-Kaikyo Road Bridge in Japan, (also known as Pearl Bridge), has three spans, but the central one has a length of 6,532ft (almost 2km). This record-setting central span 65m above the sea, makes up over half of the bridge’s total length of almost 4km By comparison, the Golden Gate’s central span is only 1,280m. Before the structure was built over the Akashi Strait that separates Kobe from Iwaya, severe storms in the area would regularly sink the ferries that crossed it. This bridge has to withstand earthquakes (a 7.2 magnitude quake hit in 1995), strong tidal currents of around 9 knots and wind gusts of up to 179 mph, so with these forces in mind it was designed with a two-hinged stiffening girder system. It also contains tuned mass dampers, designed to operate at the resonance frequency of the bridge to dampen forces. The two main supporting towers rise to 282.8m above sea level and the bridge can expand by up to 2m over the course of a day, because of the heat. The steel cables have 300,000 km of wire; each cable is 112cm in diameter and contains 36,830 strands of wire. The bridge has a total of 1,737 illumination lights and its computer technology allows a variety of combinations of colour patterns which can be used for national holidays, memorial days or festivities. Its total cost has been estimated as 500 billion Japanese Yen or US $3.6 billion. It was intended to recoup the cost by charging drivers a toll to cross the bridge.
23,000 cars cross the structure every day. It was completed in 1998. Visitors can take a bridge tour to the top of one of the towers for a mind-blowing view.
The Longest Cross-Sea Bridge
China’s Jiaozhou Bay Bridge (or Qingdao Haiwan Bridge) is listed by Guinness World Records, as from 2012, as the world’s longest bridge over water (aggregate length) at 41.58km (25.84 miles). It stretches 5 miles further than the distance between Dover and Calais and links China’s eastern port city of Qingdao to the offshore island of Huangdao. The road bridge is 33.5m wide and cost nearly £1 billion to build. The design of the bridge is T-shaped and is intended to be able to withstand severe earthquakes, typhoons and collisions from ships. 450,000 tons of steel and 2.3 million cubic metres of concrete were used in its construction. It is supported by 5,238 concrete piles and it carryies 6 lanes with 2 shoulders.
Before this the record was held by the Lake Pontchartrain Causeway in Louisiana, a 4-lane, 5,189-pile, concrete trestle bridge, north of New Orleans. Many Pontchartrain loyalists disputed the decision to award China with the world record, arguing that the Jiaozhou Bay Bridge has only 16.1 miles that span the sea compared with 23.79 miles of Potchartrain that are over open water. Guiness compromised by conferring a new title on the 58 year old causeway: longest bridge over water (continuous).
The record is due to be smashed again next year when the Hong Kong-Zhuhai-Macau Bridge is opened. The project consists of a series of bridges and tunnels crossing the Lingdingyang channel and connecting Hong Kong, Macau and Zhuhai, three major cities on the Pearl River Delta in China. The longest bridge section will be 29.6 km (18.4 miles) and will include three cable-stayed spans between 280 and 460m. Construction began in 2009, with a proposed opening date in October 2016, but the project is running late and is now due to open in December 2017.
The Longest Inhabited Bridge
The fairy tale-like Kramerbrucke (or Merchant’s) Bridge in Erfurt, Germany, is a bit of European history that is almost bound to never lose its record status. After a series of fires destroyed previous attempts to build a span over the Breitstrom River in the 12th and 13th centuries, a stone arch of 79m. was built in 1325 and 62 half –timbered houses were added on top, 32 of which still survive and are home to shopkeepers and artisans.
The Longest Floating Bridge
Evergreen Point Bridge, Seattle, officially known as Governor Albert D. Rosellini Bridge (after the Washington statesman who oversaw its creation), is a section of State Route 520 and connects Seattle to its eastern suburbs. It is a roadway which floats on top of Lake Washington. The original bridge dating from 1963, had a length of 4,750m, 2,310m of which floated on huge pontoons. By 2012 it was deemed to be in poor condition and a large seismic risk, so construction for a replacement began and was opened in April 2016. This exceeded the original length by 39.6m and can accommodate a light rail system. The road is built on 21 longitudinal pontoons, each measuring 110m by 23m. From the beginning the replacement was plagued with errors and shoddy workmanship, causing delays and several of the pontoons to crack. One of the inspectors called it “a disaster waiting to happen”, adding that he would never be tempted to drive across it himself. In order to help fund the cost of the $6.5billion improvements to the SR 520, automatic tolling is in operation.
The Longest Masonry Arch Bridge Span
The beautiful 100 year old, Pont de la Liberation, spanning the Lot River in southwest France is built of brick and unreinforced concrete, unlike the modern arch bridges which are constructed using modern materials, such as steel. It is a road bridge located in Villeneuve-sur-Lot and is 96m in length. It was constructed from 1914 to 1919.
Longest Natural Bridge Span
Although bridges are supreme examples of human engineering, we can find spectacular instances in nature. They are usually caused by erosion and have probably provided inspiration for the early bridge builders.
Once again China dominates the records and is home to three of the longest natural bridge spans in the world. The holder of the record is the Fairy Bridge in Guangxi, China, which spans the Buliu River near the border of Vietnam. It is 122m long and is carved out of limestone karst, but it is an isolated structure and can only be reached by a 3 hour rafting trip.
There is no doubt in my mind that the technology of bridge building will continue to improve and evolve and that in a few decades we will see structures that defy belief. Even some of our existing bridges, although not holding records for their size, have incredible stories attached to them. Watch this space!