Pont de l’Alma: Construction and Opening to Traffic

The original Pont de l’Alma linked newly opened roads in the Chaillot district on the Seine’s right bank with the Invalides area on the left. The bridge had to connect with roads and embankments on both sides as well as cross the river. Approach levels, carriageway width and riverside connections were all parts of the undertaking.

The ministry’s engineering description prepared for the Paris Universal Exhibition of 1867 records construction beginning on 8 November 1854 and formal opening on 2 April 1856. The roads and bridges engineers responsible were Michal, de Lagallisserie and Darcel. Total expenditure, including embankment approaches on both banks, was 2,075,759.98 francs, shared equally by the city of Paris and the state.

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The old bridge was twenty meters wide between parapets: twelve meters for the carriageway and eight meters for the two footways combined. Three elliptical masonry arches crossed the river. The central opening spanned forty-three meters with an 8.20-meter rise; the side openings each spanned 38.50 meters with a 7.50-meter rise. The arches were 1.50 meters thick at the crown. The deck served both vehicles and pedestrians, while the broad openings provided river passage below.

The two river piers were about five meters thick and rested on piles. Jules Dupuit’s bridge treatise records dredging at the pier sites before pile driving, followed by rock fill between the piles. The left and right piers used 212 and 263 piles respectively. The left abutment stood directly on natural ground; the right used another 128 piles. The outer faces were built of dressed stone, the arch interiors of worked millstone material, and the masonry was bonded with Roman cement mortar.

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The roadway opened early during construction of the masonry arches. Dupuit records that the millstone masonry of the arches, fill above them and walls supporting the footways were complete on 13 August 1855, when traffic was admitted. Workers then finished stone facings and other parts across the full width; the arches were completed on 14 September.

Problems emerged when the centering was removed. Beginning on 29 October, workers lowered it by about 1.5 to two centimeters every twenty-four hours. After a total lowering of ten centimeters, they observed that the piers were sinking too. The roadway, fill and footway supporting walls were removed to unload the piers before work continued. Initial opening and the permanent structure’s assumption of the full load were distinct stages.

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The contractors injected the rock fill between the foundation piles with a mixture of Portland cement and hydraulic lime. Hollow-brick relieving arches supported the roadway and footways with less weight than the original fill. The bridge reopened on 2 April 1856, a date subsequently used as its formal opening.

Settlement did not immediately cease. By 13 April, total sinking was about thirty-seven centimeters at the left pier and fifty-one at the right. Workers then reduced masonry above the arches while retaining ribs supporting the relieving arches. According to the treatise, this removed 327 cubic meters of masonry, approximately 600 tonnes, from the load on each pier. Settlement slowed when river levels rose during construction, providing another observation for engineers assessing unloading. Continued use depended on repeated measurement and structural adjustment.

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Four statues of French soldiers stood above the piers’ cutwaters. The Zouave statue later became a familiar marker by which Parisians observed rises in the Seine. Commemorative decoration and transport structure together made the bridge recognizable in the cityscape.

Nineteenth-century unloading did not resolve the long-term foundation problem. In his 2006 engineering retrospective, Thierry Kerisel notes that by 1970 settlement at the downstream side of the right-bank pier approached ninety centimeters. The bridge was too narrow for growing road traffic and pushed barge convoys and obstructed flood discharge. These demands, together with foundation problems, led to rebuilding.

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The replacement opened in 1974 with a width of forty-two meters. It used four steel box girders and a deck of concrete over steel plating, with unequal spans of 110 and 31.50 meters and just one river pier. The longer span crossed the left-bank expressway and navigation channel, changing the way the old three-arch bridge divided the river.

Jean Kerisel contributed to the new foundations, recommending diaphragm walls reaching chalk about thirty-eight meters below the riverbed. The Zouave statue was reinstalled on the new pier. Deep foundations and a single-pier steel superstructure expanded both road and navigation space, allowing the bridge to carry more traffic at the same crossing.

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