Angers Bridge
Encyclopedia
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...
over the Maine River
Maine River
La Maine is a river , a tributary of the Loire, 12 km long, in the Maine-et-Loire département in France....
in Angers
Angers
Angers is the main city in the Maine-et-Loire department in western France about south-west of Paris. Angers is located in the French region known by its pre-revolutionary, provincial name, Anjou, and its inhabitants are called Angevins....
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. It was designed by Joseph Chaley
Joseph Chaley
Joseph Chaley was a French civil engineer and a pioneer designer of suspension bridges in the 19th century. He was a medical officer in the army before becoming a bridge designer....
and Bordillon, and built between 1836 and 1839. The bridge collapsed on April 16, 1850, while a battalion of French soldiers was marching
Marching
See also: Loaded marchMarching refers to the organized, uniformed, steady and rhythmic walking forward, usually associated with military troops.Marching is often performed to march music, and often associated with military parades....
across it, killing over 200 of them.
The bridge spanned 102 m, with two wire cables carrying a 7.2 m wide deck. Its towers consisted of cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
columns 5.47 m tall.
Collapse
Soldiers stationed in the region frequently used the bridge, and two battalions of the same regiment had crossed earlier that day. The third battalion arrived during a powerful thunderstorm when the wind was making the bridge oscillate. When the soldiers began to cross, they gave the wind still more purchase. Survivors reported that they had been walking as if drunk and could barely keep themselves from falling, first to one side and then to the other. As usual in crossing that bridge, the soldiers had been ordered to break step and to space themselves farther apart than normal. However, their efforts to match the swaying and keep their balance may have caused them to involuntarily march with the same cadence, contributing to the resonanceResonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
. In any case, the oscillation increased. At a point when the bridge was covered with 483 soldiers and four other people (though the police had prevented many curiosity seekers from joining the march), the upstream anchoring cable on the right bank broke in its concrete mooring, three to four meters underground, with a noise like "a badly done volley from a firing squad". The adjacent downstream cable broke a second later, and that end of the deck fell, making the deck slope very steeply and throwing soldiers into the river. Many of those who fell were saved by their fellow soldiers who had not yet crossed and by residents of Angers who came to the rescue, but a total of 226 people died.
The failure was attributed to a combination of dynamic load due to the storm and the soldiers, particularly as they seem to have been somewhat in step, and to corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
of the anchors for the main cables. The cable anchorages at Angers were found to be highly vulnerable, as they were surrounded by cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
, which was believed to rustproof
Rustproofing
Rustproofing is a condition of preservation or protection, by a process or treatment whereby the rate at which objects made of iron and/or steel begin to rust is reduced. The degradation in the long term can not be stopped completely, unless the rustproofing is periodically renewed...
them for the indefinite future. However, the wire strands separated from their cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
surrounds. This allowed water to penetrate and corrode the wires.
Related bridge failures
The Angers bridge was not the first suspension bridge to collapse. Previous failures included Dryburgh Abbey Bridge in 1818, The Royal Suspension Chain PierThe Royal Suspension Chain Pier
The Royal Suspension Chain Pier was the first major pier built in Brighton, England. Generally known as the Chain Pier, it was designed by Captain Samuel Brown and built in 1823. The pier was primarily intended as a landing stage for packet boats to Dieppe, Seine-Maritime, but it also featured a...
in Brighton
Brighton
Brighton is the major part of the city of Brighton and Hove in East Sussex, England on the south coast of Great Britain...
in 1836, and damage caused by winds to the Menai Suspension Bridge
Menai Suspension Bridge
The Menai Suspension Bridge is a suspension bridge between the island of Anglesey and the mainland of Wales. Designed by Thomas Telford and completed in 1826, it was the first modern suspension bridge in the world.-Construction:...
in 1825, 1836 and 1839. The Broughton Suspension Bridge
Broughton Suspension Bridge
Broughton Suspension Bridge was a suspended-deck suspension bridge built in 1826 to span the River Irwell between Broughton and Pendleton, now in Greater Manchester, England. It was one of the first suspension bridges constructed in Europe. On 12 April 1831 the bridge collapsed, reportedly owing...
had collapsed in 1831 when soldiers marched over it in step. Subsequent spectacular suspension bridge collapses caused by wind include the failure of the Tacoma Narrows Bridge
Tacoma Narrows Bridge (1940)
The 1940 Tacoma Narrows Bridge was the first incarnation of the Tacoma Narrows Bridge, a suspension bridge in the U.S. state of Washington that spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed...
in 1940. However, the Angers bridge failure caused by far the greatest number of casualties.
When the Millennium Bridge
Millennium Bridge (London)
The Millennium Bridge, officially known as the London Millennium Footbridge, is a steel suspension bridge for pedestrians crossing the River Thames in London, England, linking Bankside with the City. It is located between Southwark Bridge and Blackfriars Railway Bridge...
was opened in 2000, the motion of pedestrians caused it to vibrate, and they fell into step with the vibrations, increasing them. This is the mechanism that probably increased the vibrations of the Angers Bridge. The problem at the Millennium Bridge was corrected during the next two years.
Results
The disaster led France to abandon suspension bridges until 1870. There had been similar failures elsewhere, such as that at Yarmouth in England in May 1845, when 79 people were killed by the fall of the main deck. The fall of the Angers bridge raised serious questions about the integrity of suspension bridges, and some engineers (such as John A. RoeblingJohn A. Roebling
John Augustus Roebling was a German-born American civil engineer. He is famous for his wire rope suspension bridge designs, in particular, the design of the Brooklyn Bridge.-Early life:...
) used reinforced decks in future structures such as the Brooklyn bridge
Brooklyn Bridge
The Brooklyn Bridge is one of the oldest suspension bridges in the United States. Completed in 1883, it connects the New York City boroughs of Manhattan and Brooklyn by spanning the East River...
. Louis Vicat
Louis Vicat
Louis Vicat French engineer.He graduated from École Polytechnique 1804 and École des Ponts et Chaussées 1806....
reported in 1853 on the problems with the anchorages, and all other similar bridges in France had to be carefully inspected.
A new bridge was built on the same site in 1960, using reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
beams.
Further reading
- R.E.D. Bishop, Vibration, Cambridge University Press (1965) for a discussion of the engineering problems of unwanted vibrations.
- J.P. Den Hartog, Mechanical Vibrations, Dover Publications (1985)
External links
- "The Angers Bridge catastrophe" English translation of article originally in La Revue du Musée des arts et métiers
- Angers bridge collapse at Bridgemeister
- suspension bridge design
- Point of Collapse, Village Voice, August 27 - September 2, 2003, by Robert Julavits for problem on the Brooklyn bridge
- British 'Millenium' or 'Wobbly Bridge', built 2000