Maria Pia Bridge
| Maria Pia Bridge | |
|---|---|
 |
|
| Carries | railway |
| Crosses | river Douro |
| Locale | Porto, Portugal |
| Heritage status | yes |
| Characteristics | |
| Material | wrought iron |
| Total length | 353 metres (1,158 ft) |
| Height | 60 metres |
| Longest span | 160 m (520 ft) |
| History | |
| Architect | Théophile Seyrig, Gustave Eiffel |
| Construction begin | 5 January 1876 |
| Construction end | 1 October 1877 |
| Inaugurated | 4 November 1877 |
| Closed | 1991 |
The Maria Pia bridge (Ponte Maria Pia), commonly known as Ponte Dona Maria, is a railway bridge built in 1877 by Gustave Eiffel in Porto, Portugal. Built of wrought iron, its two-hinged crescent arch used to carry the railway to Lisbon for 353 metres (1,158 ft) across the River Douro at a height of 60 m (200 ft) above the river. When constructed it was the longest single-arch span in the world. It is no longer in use as a rail bridge, a modern replacement having been constructed in 1991.
In 1875 the Royal Portuguese Railway Company announced a competition for a bridge to carry the Lisbon to Porto railway across the river Douro. This was very technically demanding. The river was fast-flowing, its depth could be as much as 20 m (66 ft) when in flood and the river bed was made up of a deep layer of gravel. These factors ruled out the construction of piers in the river, so that the bridge would have to have a central span of 160 m (520 ft). At the time the longest bridge span was the 156 m (512 ft) of the bridge built by James B. Eads over the Mississippi at St Louis.
Eiffel & Cie's design, priced at 965,000 French francs, was the least expensive of the four designs considered, around two thirds of the cost of the nearest competitor. Since the company was relatively inexperienced, a commission was appointed to report on their suitability to undertake the work. Their report was favorable, although it did emphasise the difficulty of the project:
"The complete study of a structure of this size presents great difficulties. The methods of calculation known up until now can only be applied in practise with the aid of hypotheses which depart from established fact to a greater or lesser extent, and thus render the projected results uncertain."
Responsibility for the actual design is difficult to attribute, but it is probable that a large part was played by Théophile Seyrig, Eiffel's business partner, who presented a paper on the bridge to the Société des Ingénieurs Civils in 1878. Eiffel, in his account of the bridge which accompanied the 1:50 scale model exhibited at the 1878 World's Fair, credited Seyrig, along with Henry de Dion, with work on the calculations and drawings.
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