Viaduc de Lavaur

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Coordinates: 43 ° 42 ′ 12 ″  N , 1 ° 49 ′ 26 ″  E

Viaduc de Lavaur
Viaduc de Lavaur
use Railway bridge
Crossing of Agout
place Lavaur (Tarn) , France
construction Stone arch bridge
overall length 123 m
Number of openings a
Longest span 61.50 m
completion 1884
planner Paul Séjourné
location
Viaduc de Lavaur (Occitania)
Viaduc de Lavaur

The Viaduc de Lavaur is a railway bridge over the deeply cut agout in Lavaur , Tarn , in the French region of Occitania , which connects Lavaur on the route from Saint-Sulpice-la-Pointe to Castres further to the southeast. The bridge is now used by the TER Midi-Pyrénées regional express trains . The Pont de Lavaur , a road bridge completed in 1791 around 200 m further south, is otherwise the only bridge that crosses the river in Lavaur.

description

The stone arch bridge crosses the agout with a single large and strikingly slender segment arch with a span of 61.50 m, the apex of which is around 21 m above the low water. Its design and the profiling of the arched cheeks are based on the neighboring Pont de Lavaur. The arch is pulled down almost to the slope floor, which is very stable here, in order to save particularly expensive abutments . On both halves of the arch there are three brick round arches with spans of 4.50 m, which support the bridge table emphasized by its own profile. This main arch is delimited on both sides by mighty pillars reaching as far as the bridge table, from which approach bridges with two brick round arches each with a span of 8 m lead to the edge of the valley. The bridge deck, which is 123.50 m long, is delimited by a balustrade above the main arch , and by small walls above the pillars and the approach bridges.

history

With the construction of the bridge of Le Castelet in the Ariège department in the Pyrenees , the Viaduc de Lavaur and the Pont Antoinette on the same railway line some 27 km further south-east in the years 1882–1884, the 33-year-old Paul Séjourné gained wide recognition for the further development of the construction of brick arched stone bridges.

In the case of bridges with increasing spans, the falsework , which is supposed to carry the weight of the complete arch , naturally becomes larger, more complex and more expensive. In order to keep this within limits, Séjourné used the method, which was already known to the Romans but had been forgotten again, of initially only building a thin layer of arches on a comparatively light falsework. This layer can then bear its own weight and that of the next arch layer and thus itself take on the function of the falsework. At the Viaduc de Lavaur, Séjourné had the main arch made from three superimposed arch layers.

Another innovation was the complete opening of the arch gussets . Séjourné mentions older models for this, in which the openings were rather narrow passages in order to reduce the lateral water pressure on the bridge during floods. A closed gusset filled with masonry adds little to the stability of the bridge, but adds a considerable amount to its weight, which is to be borne by the arch. Séjourné therefore replaced the walled gussets with three round arches each supported by narrow pillars. He created the model for many later arch bridges not only made of stone, but also of concrete .

Web links

Commons : Viaduc de Lavaur  - collection of images, videos and audio files