Bridges and overpasses
Designed to withstand time and the elements: cable-stayed bridges
19 June, 2019
Legendary bridges in excellent condition
After the collapse of the Genoa motorway bridge in the summer of 2018, the French Ministry of Transport published the results of a national survey conducted to establish the condition of road bridges in France. Two one-of-a-kind structures were found to be in excellent condition: the Millau viaduct and the Normandy bridge. The latter, built by VINCI Construction Grands Projets and Freyssinet in the early 1990s, was then the world's largest cable-stayed bridge, with a central span of 856 metres.
The Normandy bridge is the first example of a series of challenges successfully achieved by VINCI Construction and its subsidiaries. Michel Virlogeux, one of the greatest architects of cable-stayed bridges, recalls the technical difficulties that Freyssinet had to overcome when building his curving cable-stayed bridge at Térénez.
Cable-stayed bridges: linking geographies
From the Lewis and Clark Bridge across the Ohio River in the United States to the Atlantic Bridge over the Panama Canal, cable-stayed bridges span the longest distances with a visually elegant structure capable of resisting high winds, extreme temperatures, salt water, vehicle vibration and even earthquakes.
Each cable-stayed bridge has its own challenges
A cable-stayed bridge is distinctive for the high level of flexibility in the deck that forms its superstructure. Because it allows optimal use of the stays, this flexibility poses challenges to bridge builders that can be resolved only using the most advanced computer calculation methods. For example, the casting of segment 21 of the central span of the Atlantic Bridge imposed a new load of 250 tonnes at a distance of 170 metres from the pylon. At the time of casting on the basis of previous computer models, segment 20 of the central span had descended 75 cm, and the pylon had moved 38 cm longitudinally to the same side. But the use of sophisticated computer calculation systems made it possible to integrate the movements of the structure throughout the construction process, which meant that the decks laid from opposite banks met perfectly at the centre point of the 530-metre central span. This process of connecting the two deck sections by casting the keystone segment in-situ required the use of substantial temporary structures capable of supporting 2,000 tonnes in order to retain the deck sections longitudinally. Nevertheless, the extreme accuracy of the geometric checks carried out on the bridge and the flexibility of its deck made it possible to use only relatively limited resources to achieve perfect alignment of the deck sections vertically and horizontally.
Every project has its own goals. To ensure maximum stability for rail traffic, the central span of the Yavuz Sultan Selim bridge in Istanbul adds the advantages of a cable-stayed bridge to those of a suspension bridge. The cables and dampers for this structure were designed, supplied and installed by Freyssinet. On the Kosciuszko Bridge that links Queens to Brooklyn in New York City, the stays are fitted with innovative fire and explosion protection systems recently designed and introduced by Freyssinet.
Over the last two years, Sixense has monitored eight cable-stayed bridges around the world: from Vietnam (Cao Lanh Bridge) to Kentucky (ORB), Russia (Korabelny & Petrovsky) and Turkey (Bosphorus 3).
From design to maintenance, cable-stayed bridges are assured of their full lifespan now and going forward thanks to state-of-the-art technologies developed by VINCI Construction and its subsidiaries. Powerful geographic icons, cable-stayed bridges will continue to link riverbanks, regions and continents for a very long time.