Pont Albert-Louppe

from Wikipedia, the free encyclopedia

Coordinates: 48 ° 23 ′ 16 ″  N , 4 ° 24 ′ 0 ″  W.

Pont Albert-Louppe
Pont Albert-Louppe
use Pedestrians, cyclists
Crossing of Estuary of the Élorn into the Bay of Brest
place Plougastel-Daoulas and Relecq-Kerhuon , Finistère
construction Reinforced concrete - arch bridge
overall length 888 m
width 12 m
Number of openings three
Pillar spacing 186.40 m
Clear height 35.30 m above the NW
start of building 1926
opening 1930
planner Eugène Freyssinet
location
Pont Albert-Louppe (Finistère)
Pont Albert-Louppe

The Pont Albert-Louppe , originally called Pont de Plougastel , later called the premier Pont de Plougastel , is a bridge over the mouth of the river Élorn in the Bay of Brest . It connects the municipality of Plougastel-Daoulas with Relecq-Kerhuon , a suburb of Brest in Brittany . It was one of the first bridges in which Eugène Freyssinet applied the first ideas of the prestressed concrete method he later developed . When it was completed, the Pont de Plougastel had the largest span of any concrete bridge in the world.

use

The arch bridge was originally designed as a road and rail bridge, which was supposed to shorten the route from the south of the Finistère department to Brest. The next bridge over the Elorn was 13 km upstream in Landerneau . The planned railway line from Quimper to Brest was never built. When the bridge was no longer able to cope with the increasing traffic, a large cable-stayed bridge , the Pont de l'Iroise, was built right next to it between 1991 and 1994 . Since then, the Pont Albert-Louppe has only been used as a pedestrian and bicycle bridge.

Surname

The original name referred to the Plougastel peninsula in the south of the Élorn, which protruded into the Bay of Brest. The name was changed in 1994 to distinguish it from the second bridge. Finally, it was named after Albert Louppe (1856–1927), who was then President of the General Assembly of the Finistère department, who had a decisive influence on the construction of the bridge, but did not live to see its completion.

location

The position of the bridge over the mouth of the Élorn, which is 640 m wide at this point, was determined by two rock spurs in the bottom of the river bed, which served as a stable base for the two piers. The tide dependent current in the estuary can reach 4 knots , the tidal range 7.5 m. Storms occur with significantly more than wind force 12 . The banks rise relatively steeply on both sides to the higher flat land, so that the road over the bridge does not have to climb steeply despite its height.

description

The bridge is a series of three segment arches of the same size with an elevated truss structure , the lower chord of which can accommodate a railroad track, while the upper chord is designed as a slab for road traffic. The arches each consist of a reinforced concrete - concrete box , which is clamped into the cantilevered from the abutments and the piers arc approaches without joints. The hollow boxes are reinforced on the inside by two longitudinal walls each. They are only weakly armored, mostly across the course of the arch. The proportion of steel in the hollow boxes is around 23 kg per cubic meter of concrete. The in cantilever with ideas of later prestressed concrete procedure arc approaches made collar measured from the pillar axis, 15.60 m from. The bridge slab for the carriageway rests directly on the apex of the arches, while the railway line below runs through the arched and reinforced arches that are opened for this purpose. Although this half-timbered section runs the entire length of the actual bridge, it was only built in a short section under the approach bridges. The upper edge of the carriageway is 42.50 m above low water, the clear height is 35.30 m above low water and 27.80 m above the spring tide . The bridge, including the approach bridges, is 888 m long. Its carriageway was originally 8 m wide, including the two 1 m wide sidewalks, but between 1962 and 1966 it was widened to 12 m (9 m + 2 1.50 m walkways) together with the pillars.

Details of the construction process

Construction began with concreting the abutments on the banks in a circular construction pit made of reinforced concrete and with the construction of the approach bridges.

Two cable cranes running parallel across the river with a span of 680 m were installed on the banks , the ropes of which were carried by 55 m high wooden towers. Because of the often poor visibility and to enable precise unloading, a driver's cab was installed next to the two trolleys from which the crane could be controlled. For particularly heavy transports, the trolleys could run side by side, lift the load together and thereby increase the load capacity from two tons to four tons.

A reinforced concrete caisson was also made on the bank , with which the two pillars were built. Wooden flotation boxes were attached to its sides so that it could swim into the right place in the river. After building the first pillar, he was swum to the second pillar.

Falsework between the arches, above the cable cranes

At the same time, the largest 160 m long falsework that had ever been built up to that point was constructed on the bank, which was then used for all three arches. It consisted of two closely stacked shells, separated by a narrow framework, which were initially mounted on auxiliary supports. The ends of the wooden truss arches were braced together with a tension band consisting of adjustable steel cables, resulting in a stable structure weighing 300 tons. The ends of the falsework were supported by a 35 m long and 8 m wide barge, also made of reinforced concrete . With these barges and with the help of the rising tide, the falsework was floated to the intended place between the abutment and the first pillar and set down under the protruding arches. Only a few minutes were available for the lowering process at the beginning of the ebb, but all three positions of the falsework could be carried out without any problems.

The hollow boxes were concreted in different sections. First, the entire arch was divided into concreting sections in order to distribute the load as evenly as possible on the falsework. Then first the floor of the box with the connections for the vertical walls was concreted, then two walls each and finally the box ceiling. On the completed and largely hardened arch, the elevation for the bridge ceiling could then be started while the falsework was in use for the next arch.

history

The first ideas for a bridge over the Élorn were discussed as early as 1890. More concrete plans from 1904 failed because of resistance from the Landerneau municipality, who feared that a bridge would strengthen Brest's position and sideline itself. Various other projects were discussed, but could not be pursued further during the First World War .

On September 22nd, 1922, the general assembly of the Finistère department under its president Albert Louppe finally decided to have a bridge built. In the competition initiated in 1923, steel bridges as well as concrete bridges were offered, whereby the offer of Entreprises Limousin with the reinforced concrete bridge planned by Eugène Freyssinet with overlying carriageways for the railroad and road traffic at a price of 9.57 million francs by around 5 million francs below that of the competitors. Still, there were concerns as to whether the project of a concrete bridge never built of this size would offer the same level of security as a steel bridge. Ultimately, the influence of Albert Louppe overcame the doubts, so that the general assembly on January 21, 1924 placed the order for the offer from Limousin / Freyssinet.

The actual construction work on the bridge began in 1926 and ended on October 9, 1930 with its inauguration by the President of the Republic Gaston Doumergue .

On August 27, 1944, the withdrawing German troops blew up the northern arch, and part of the central arch was also destroyed. The approach bridges were damaged by Allied bombs . After the war, the bridge was rebuilt and opened to traffic on October 29, 1949.

Wind deflector on the Pont Albert-Louppe to protect the Pont de l'Iroise behind it

Between 1962 and 1966 the bridge was widened from 8 m to 12 m. In 1974 the idea of ​​a second bridge was discussed for the first time, which was then carried out between 1991 and 1994. Thereafter, traffic on the Pont Albert-Louppe was restricted to bicycles and pedestrians; the discussed idea of ​​tearing down the bridge could not prevail. In 2005 and 2006 the company Freyssinet carried out renovation work. The Pont Albert-Louppe was fitted with wind deflectors at the apex of the arch to protect the cable-stayed bridge standing close to it.

Web links

Commons : Pont Albert Louppe  - collection of images, videos and audio files

Individual evidence

  1. ↑ Leonardo Fernández Troyano: Bridge Engineering. A global perspective. Colegio de Ingenieros de Caminos, Canales y Puentes, Thomas Telford 2003, ISBN 0-7277-3215-3 , p. 78