ISABEL RUBIO ARROYO | Tungsteno
There is a new bridge linking Europe and Asia. Around 5,000 workers and 600 engineers have been involved in the construction of this gigantic, suspended structure, which has taken four years. Among the challenges to be taken into account in its design and construction were high winds, seismic activity and the huge container ships that sail through Turkish waters. We look at the construction of this and other suspension bridges, the longest on the planet.
1915 Canakkale Bridge
The 1915 Canakkale Bridge, also known as the Dardanelles Bridge, was built by Turkish and South Korean companies with an investment of 2.5 billion euros. Its construction, which began in March 2017, involved more than 5,000 workers. This mega-structure, in addition to connecting the European and Asian coasts of northwest Turkey, has the longest main span of all suspension bridges in the world. The average distance between the support towers or piers is the measure commonly used to compare suspension bridges. In this case, the main span is 2,023 metres, a figure that also refers to the centenary of the Republic of Turkey in 2023.
The total length of the bridge is 4.6 kilometres, including the approach viaducts. Between the towers, which measure 318 metres in height, 288 steel cables are strung. Mega-blocks weighing 700 tonnes and measuring 48 metres long and 45 metres wide have been used for the construction of the bridge deck. The potential impacts of the bridge on birds and marine animals have also been studied and minimised. In addition, the bridge successfully completed various wind tests and both the structure and soil have been strengthened to withstand the impacts of ships and possible earthquakes.
This infrastructure was officially inaugurated by President Erdoğan on 18 March 2022. With this project, he aims to put the “country ahead in investment, workforce and exports.” Until now, vehicles travelling between Anatolia and the Gallipoli peninsula had to cross the Dardanelles on a one-hour ferry ride, which with waiting time could take up to five hours. The journey now takes only about six minutes.
The bridge was built thanks to an investment of 2.5 billion euros and the efforts of 5,000 workers. Credit: 1915 Canakkale
Akashi Kaikyo Bridge
Akashi Kaikyo was the longest suspension bridge in the world when it opened on 5 April 1998, until it was surpassed by the 1915 Canakkale Bridge. Nicknamed the Akashi Strait Bridge or Pearl Bridge, it connects the Japanese city of Kobe on the main island of Honshu to Iwaya on Awaji Island. The six-lane bridge carries nearly 23,000 cars every day. It measures 3,911 metres long overall and has three sections: a 1,991-metre-long central section and two 960-metre-long side sections. In addition to its length, it is also notable for its height: the two main towers stand 297 metres above the surface of the water.
Construction of the mega-structure, which began in 1988, required some 181,000 tonnes of steel and 1.4 million cubic metres of concrete. Like the 1915 Canakkale Bridge, the Akashi Kaikyo Bridge is located in a seismically unstable region that also experiences severe storms. Engineers used a complex system of counterweights, pendulums and steel girders to enable the bridge to withstand winds of up to 290 kilometres per hour, earthquakes and strong ocean currents. It is a highly adaptable structure, as it can also expand and contract up to two metres in a single day depending on the temperature.
Akashi Kaikyo, also known as Akashi Strait Bridge or Pearl Bridge, is 3,911 metres long and has three spans. Credit: Tysto.
The Yangsigang Bridge in China, which crosses the Yangtze River in Wuhan, is the longest double-decker suspension bridge with the longest main span in the world. The average distance between the towers is 1,700 metres, which also makes it the third longest suspension bridge in the world. In total, this engineering marvel measures 4.13 kilometres. The main structure of the bridge deck has 49 steel girders that are each 36 metres long, 32.5 metres wide and 10 metres high.
“The Yangsigang Yangtze River Bridge is the world’s longest-spanning double-deck suspension bridge,” boasted Xu Gongyi, chief designer of the structure, at its opening in October 2019. Its two decks each have six lanes. While the upper deck is designed for speeds of 80 kph, the lower one is engineered for 60 kph. Lin Chi, vice president of Wuhan Urban Construction Investment and Development Group, says the aim of the bridge is to help ease traffic congestion and promote more balanced urban development.
The Yangsigang is the double-decker suspension bridge with the longest main span in the world. Credit: Wikimedia Commons.
Among the longest bridges on the planet is also the Nansha Bridge, which crosses the Pearl River in Guangdong Province in southern China and whose construction began in 2014. Opened to traffic in 2019, the Nansha Bridge comprises two cross-river mega-span suspension bridges and has a total length of 12.9 kilometres. The longer of the two suspension bridges, called the Nizhou Waterway Bridge, has an average span of 1,688 metres. But this mega-structure stands out for something else: its 40.5-metre width and eight traffic lanes make it the widest steel box girder bridge on the planet.
Some 50,000 vehicles passed over the Nansha Bridge on the first day of its opening, representing 18% of the total daily traffic volume across the Pearl River’s estuary. The bridge, with an estimated lifespan of 100 years, is designed to allow vehicles to travel at a speed of about 100 kph. Thanks to this structure, it is possible to shorten the travel distance between the Chinese cities of Guangzhou and Dongguan by about 10 kilometres and save about half an hour's travel time.
At 40.5 metres wide and with eight lanes of traffic, the Nansha is the world’s widest steel box girder suspension bridge on the planet. Credit: Mageba Group.
The 1915 Canakkale Bridge, the Akashi Kaikyo, the Yangsigang, the Nansha and other suspension bridges are usually erected to link two places separated by water, for example, a bay or a river. Their construction is often complex, requiring the loads from the cables and anchors that support them to be properly distributed. These mega-structures are also notable because they can span longer distances than any other form of bridge. Although these types of bridges were built by primitive peoples using, for example, plaited bamboo cables, in recent decades they have incorporated all kinds of innovations to reach greater distances and withstand strong winds, sea currents and earthquakes.
· — —
Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.