Alconétar viaduct
Coordinates: 39 ° 43 ′ 10 " N , 6 ° 24 ′ 38" W.
| Alconétar viaduct (Alcántara reservoir) |
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| Official name | Puente Arcos de Alconétar | |
| use | Highway bridge | |
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| Crossing of | Tajo (Alcántara reservoir) | |
| place | near Cáceres , Extremadura | |
| construction | 2 steel arch bridges | |
| overall length | 400 m | |
| width | 2 × 13.5 m | |
| Longest span | 220 m | |
| Arrow height | 42.5 m | |
| completion | 2006 | |
| planner | José Antonio Llombart | |
| location | ||
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The Alconétar Viaduct ( Spanish Puente Arcos de Alconétar ) is a motorway bridge on the Spanish A-66 - Autovía Ruta de la Plata .
location
The structure stands near Cáceres , Extremadura and bridges the Tajo or the arm of the Alcántara reservoir in which the river rises. About 2.8 km to the west is the Tajo railway bridge of the planned Lisbon – Madrid high-speed line and another 540 m to the west is the double-decker bridge for the N-630 and the railway . The Almonte viaduct of the A-66 over the Río Almonte arm of the reservoir is 12 km further south.
description
The Puente Arcos de Alconétar consists of two parallel, 400 m long steel arch bridges with an overhead carriageway and a span of 220 m. Each of the bridges has two lanes and a safety lane on both sides, which is also provided for maintenance personnel. There are no sidewalks. The motorway crosses the reservoir when it is full, at a height of around 60 m. All steel parts are made of Corten steel , whose rust-red color contrasts with the light concrete of the pillars and the strong blue of the railings.
The bridges are 13.5 m wide and are 10 m apart. The carriageway girders are a composite structure made of a prestressed concrete slab on two steel hollow boxes . They are mounted on the arches with steel supports with a rectangular hollow cross-section. Outside the arches, the road girders are placed on reinforced concrete pillars arranged in pairs , which are connected by a crossbar below the road girder. Bearings are arranged on the 48 m high pillars on the bank, which allow longitudinal movements of the deck girder, but which transfer lateral forces to the pillars. The pillars on the arches and the concrete piers have a uniform pillar spacing of 26 m, only at the two ends of the bridge it is 17.88 m.
The arches each consist of two steel box girders at a lateral distance of 6.50 m, which are connected to one another by diagonal cross braces. Aerodynamic baffles are attached to the outside of the box girders to prevent the arches from vibrating caused by the wind. The arches have a span of 220 m and an arrow height of 42.5 m. Its box girders are 1.20 m wide; their height of 3.20 m at the transom foundations is reduced to 2.20 m up to the apex.
Construction process
The bridge was designed by the engineering firm Estudio de Ingeniería y Proyectos (EIPSA) under the direction of José Antonio Llombart and executed by OHL - Obrascón Huarte Lain. It had to be taken into account that the reservoir was not allowed to be impaired by the construction work or the completed bridge.
Construction began with the reinforced concrete pillars and the 11 m wide, 14 m long and 10 m high transom foundations, which simultaneously served as the foundations for the large pillars on the bank and as an abutment for the steel arches. Adjustable steel joints were arranged on them to accommodate the steel arches.
The carriageway girders were manufactured using the incremental launching process, with the two longitudinal girders serving as runners with which they were pushed forward over the pier heads. Their distance from one another was adapted to the crawler track of the mobile crane used during assembly . For the first 22 m, the longitudinal girders did not yet carry a concrete slab and served as a front end . The advance ended at the last large pillar on the bank. The protruding first 13 m of the free longitudinal beams were then dismantled with the help of the mobile crane to make space for the assembly of the arch.
Each arch was divided into four approximately 60 m long and 200 t heavy segments. Two of the prefabricated segments were provided on the roadway on both sides of the valley. The first segment was pushed forward until it was tipped over the edge into a vertical position in an auxiliary frame and then lowered by strand jacks to the joint on the abutment and fastened there in a moveable manner. The second segment was then pushed forward and connected to the first segment fixed to the bridge by a joint. The mobile crane then, while slowly driving forward, raised the other end of the segment until it was in an almost vertical position. The last turn was carried out by hydraulic presses, with a rope guy preventing it from tipping over onto the valley side. Then the joint was blocked and the segments welded together so that they formed a 120 m high tower.
After the same assembly process had been carried out on the other side of the valley, the two halves of the arch were lowered using guy ropes attached to the track girder far behind them until they could be connected to each other with a special locking device in the apex. This temporarily created a three-hinged arch . Its position and height were adjusted using the sliding joints on the abutments. Finally, the crown joint was blocked with steel plates and the adjustable joints were concreted in on the abutments, so that a clamped arch was created.
On four days in January 2016, with a gentle wind of only 5.5 m / s (20 km / h), vertical vibrations (without torsional vibrations ) occurred on the arch , which reached a magnitude of +/- 80 cm and are clearly visible to the eye were visible. The phenomenon disappeared in stronger winds. Aerodynamic baffles were attached to the arch and the phenomenon was not repeated. Wind tunnel tests revealed Kármán vortex streets to be the cause, which were triggered by a very rare combination of arch shape and wind conditions. The guide plates attached based on empirical values only had to be changed slightly.
In the further course of the process, the steel supports were alternately lifted onto the arch with the mobile crane and installed, and the deck girder was advanced by a further 26 m. In order to load the arch as equally as possible, work was carried out from both sides of the valley at the same time. Nevertheless, this phase required extensive static calculations because of the changing loads.
The motorway section with the bridge was officially opened on July 27, 2006.
See also
Web links
- Alconétar viaduct. In: Structurae
- Tajo River Bridge on HighestBridges.com
-
Collective file on researchgate.net, pp. 1–122, with the following content:
- José Antonio Llombart Jaques, Jordi Revoltós Fort, Sergio Couto Wörner: Puente sobre el río Tajo, en el embalse de Alcántara ("Arcos de Alconétar"). In: Hormigón y Acero No. 242, 4th trimestre 2006, pp. 5–38 (in PDF pp. 1–34) (Spanish, English)
- Miguel Ángel Astiz Suárez: Estudio de las vibraciones de los arcos de Alconétar . P. 39–50 (in PDF P. 35–44)
- Vicente Puchol de Celis: Análisis experimental de las vibracionescausadas por el viento en el puente sobre el río Tajo (“Arcos de Alconétar”). In: Hormigón y Acero No. 243, 1st trimestre 2007, pp. 51–66 (in PDF pp. 45–60)
- Antonio Barrero Gil, Gustavo Alonso Rodrigo, José Meseguer Ruiz, Miguel Ángel Astiz Suárez: Ensayos en túnel de viento de un modeloa e roelástico del arco del puente sobre el río Tajo “Arcos de Alconétar”. In: Hormigón y Acero No. 245, 3.º Trimestre 2007, pp. 33–40 (in PDF pp. 61–68)
- Juan Carlos Lancha Fernández: Estudio del comportamiento aeroelástico del puente sobre el río Tajo en el embalse de Alcántara. In: Hormigón y Acero No. 247, 1st trimestre 2008, pp. 55–67 (in PDF pp. 69–81)
- José Antonio Llombart, Jordi Revoltós, Sergio Couto, Manuel Alpañés: Puente sobre el río Tajo, en el embalse de Alcántara. In: III Congreso de Ache de Puentes y Estructuras - Las Estructuras del siglo XXI - Sostenibilidad, innovación y retos del futur , pp. 1–9 (in PDF pp. 82–90)
- José Antonio Llombart Jaques, Miguel Ángel Astiz Suárez: Puente “Arcos de Alconétar” Vibraciones producidas por el viento durante la construcción y sistema aerodinámico de corrección. Without pagination (in PDF pp. 91-100)
- José Antonio Llombart Jaques, Jordi Revoltós Fort, Sergio Couto Wörner: Puente “Arcos de Alconétar” - Procedimientos especiales de construcción. Without pagination (in PDF pp. 101–110)
- José Antonio Llombart, Jordi Revoltós, Sergio Couto, Manuel Alpañés: La construcción del puente sobre el río Tajo, en el embalse de Alcántara. In: III Congreso de Ache de Puentes y Estructuras - Las Estructuras del siglo XXI - Sostenibilidad, innovación y retos del futur, pp. 1–12 (in PDF pp. 111–122)
- Pedro Plasencia Lozano: Alconétar, paisaje cultural de la ingeniería. Una propuesta de ordenación territorial. Pp. 1-19, on dialnet.unirioja.es
Individual evidence
- ↑ Unless otherwise stated, the information in this article is based on the publication by José Antonio Llombart Jaques, Jordi Revoltós Fort, Sergio Couto Wörner: Puente sobre el río Tajo, en el embalse de Alcántara ("Arcos de Alconétar"). In: Hormigón y Acero No. 242, 4th trimestre 2006, pp. 5–38 (Spanish, English)
- ↑ Alconetar Bridge on Alcantara Reservoir on jallombart.com
- ↑ EIPSA has since been taken over by SENER: Acquisition of special structures firm EIPSA by SENER
- ↑ Video of the swinging bow