Salginatobel Bridge
| Salginatobel Bridge | ||
|---|---|---|
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| use | Road bridge | |
| Crossing of | Salginabach | |
| place | Schiers , Schuders | |
| construction | Arched bridge made of reinforced concrete | |
| overall length | 132.30 m | |
| width | 3.80 m | |
| Number of openings | 1 | |
| Longest span | 90.04 m | |
| Arrow height | 12.98 m | |
| Arch thickness (vertex) | 0.20 m | |
| height | ~ 90 m | |
| Load capacity | 350 kg / m² | |
| start of building | 1929 | |
| completion | 1930 | |
| planner | Robert Maillart | |
| location | ||
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| Above sea level | 873 m above sea level M. | |
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The Salginatobel Bridge is a road bridge in the canton of Graubünden in Switzerland between Schiers and the 1250 m high Schuders .
The reinforced concrete bridge , designed by Robert Maillart in 1929 and completed in 1930, is considered a technical and architectural masterpiece of engineering and is now shown as a teaching object at technical universities around the world. It is an excellent example of an economical and at the same time architecturally elegant solution.
location
The Salginatobel bridge is located on the community road from Schiers, a place 654 m above sea level on the Landquart with around 2,600 inhabitants, to Schuders, a hamlet made up of a few houses at 1,250 m above sea level. The road runs high above the narrow valley of Schraubaches Schiers on the Weiler Montagna, angles, and sub-Pusserein Crausch to the bridge over the Salgina brook, the approximately 90 m below it in a narrow ravine flows to Schraubach. Since the bridge has become a destination for tourists and professionals, the community has created parking spaces and a circular path across the bridge on Schraubachstrasse in the valley floor.
description
The single-lane bridge crosses the ravine with a single concrete arch, which begins very slim on the almost vertical rock walls and slowly becomes stronger until it merges with the elevated bridge plate after about a quarter of the arch. The roadway slab is seamlessly connected to its boundary wall, which visually emphasizes the long straight line above the arch. At the eastern end, the rock is so steep that the carriageway slab only extends just over the arch, at the western end it is lengthened by six elevated fields over the less steep slope.
Up close it can be seen that the thin arched slab at the abutments is significantly wider than the carriageway slab and tapers towards the center in an elegant curve line until it reaches the same width as the carriageway slab at the apex and is connected to it in a striking block becomes. On the arched slab, but clearly separated from its edge, the two parallel longitudinal walls of the initially open hollow box are arranged, which is linear in plan and significantly narrower than the carriageway slab. These longitudinal walls rise over three bridges in a curved line until they reach the plate beam of the roadway and from there form a closed hollow box. Every six meters, a narrow transverse wall serves as an elevation for the roadway, with the transverse walls being reinforced at their ends to form pillars, the outer sides of which are seamlessly connected to the box girder walls. Only the first transverse wall on the arch base expands downwards so that it almost reaches the width of the arch plate, which is also wide there. In the second and third fields, a further pane is installed between the transverse walls, but it does not protrude beyond the open hollow box.
For the viewer, this results in a multitude of different lines that convey a varied and architecturally interesting image of a light bridge.
Technical details
The entire reinforced concrete bridge structure is 132.30 m long. At the apex of the arch, the road surface is 873.72 m above sea level. The clear height above the creek bed is (depending on the respective gravel location) about 90 m. The roadway has a gradient of 3% or 3.97 m in a westerly direction, so that there is a height difference of 3.97 m between the two ends of the structure.
The bridge is based on the system developed by Maillart of the three-hinged box girder and the stiffened bar arch.
The arch plate has a span of 90.04 m with an arrow height of 12.98 m; it is also on the slope, d. H. There is a height difference of 2.70 m between the fighting joints . The arch plate is 40 cm thick on the fighters, but only 20 cm thick under the closed box girder up to the apex. In the ground plan, the arch plate on the transoms is 6 m wide and tapers to 3.80 m at the top of the arch.
The 25 cm thick side walls of the box girder are only about 40 cm high at the transom joints, but quickly become larger in the three open areas of the gusset and reach around 3.60 m at the fourth pillar. From this pillar on, the walls are seamlessly connected to the beam of the deck. The resulting closed box girder is 26.80 m long and 2.58 m wide on both sides of the apex; it is divided by transverse panes into an 8.80 m long section, which is only 1 m high at the apex, and three further sections, each six meters long. The transverse panes of the closed hollow box are 10 cm thick. The transverse walls in the open gusset are 12 cm, 14 cm and 20 cm thick. They are delimited by pillars that are 60 cm wide, but the pillar on the base of the arch is 70 cm wide. The open box girder and the transverse walls including pillars are also 2.58 m wide.
The bridge plate is 3.80 m wide. 15 cm thick boundary walls stand on it, leaving a roadway width of 3.50 m. It is reinforced by two bars that are 18 cm wide and up to 80 cm deep. The bridge slab protrudes 61 cm on both sides over the box girder or the pillars, but meets at the top of the arch with the arch slab of the same width there.
The position of the reinforcing bars and the crown joint are shown in the reinforcement plan.
history
Before the bridge was built, Schuders could only be reached via a mule track . The construction of a road had only begun in 1928, although it should be noted that car traffic was prohibited in the canton of Graubünden until 1925. On July 12, 1928, the cantonal building authority published a tender for the construction of the Salginatobel Bridge. The offer from Florian Prader & Cie., Zurich / Geneva for a bridge designed by Robert Maillart at a flat rate of 135,000 francs turned out to be the cheapest of the 19 offers received.
The respected carpenter Richard Coray from Trin , who had already built the scaffolding for the Wiesen Viaduct , the Langwies Viaduct and the Gründjitobel Viaduct , was commissioned with the construction of the falsework at an additional flat rate of 45,000 francs . Since Maillart had planned a very thin arched shell, which itself took on a load-bearing function for the superstructure after concreting, Coray was able to provide a delicate and light falsework. The necessary wood was felled in the community forest and prepared by only six workers using a parts list with 1285 numbers, provided with holes, labeled, put together on a trial basis and finally brought to the construction site in horse-drawn vehicles. There the beams were lifted to their intended position with a small cable crane and installed by the carpenters.
Concrete work began in 1930 with the arched shell, which was installed without interruption in just 40 hours. The concrete had to be mixed by hand and wheelbarrows brought in equal parts to both sides of the arch. All the concrete work was completed in just three months. In mid-August 1930 the falsework was lowered and the bridge opened to traffic.
An explosive object was attached to the bridge during the Second World War .
In 1991, the Salginatobel Bridge was named an International Historic Civil Engineering Landmark by the American Society of Civil Engineers (ASCE) . In 1997/1998 the bridge was renovated and the parapet was renewed.
literature
- Andreas Kessler (ed.): From the wooden footbridge to the world monument. The history of the Salginatobel Bridge. International historical landmark of civil engineering. Verlag Buchdruckerei Schiers, Schiers 1996, ISBN 3-952096-31-8 .
- Andreas Kessler: Salginatobel Bridge, the development of a masterpiece. Verlag AG Buchdruckerei Schiers, Schiers 2011, ISBN 978-3-9522963-6-3 .
- Max Bill : Robert Maillart. Artemis, Zurich 1949.
- Peter Marti, Emil Honegger: Robert Maillart - concrete virtuoso . Ed .: Society for Civil Engineering. 3. Edition. VDF , Zurich 2007, ISBN 978-3-7281-3104-1 .
- Brochure World Monument Salginatobel Bridge. Published by the Schiers Salginatobel Bridge Association.
Web links
- The Salginatobel Bridge
- Salginatobel Bridge themed trail at www.praettigau.info
- Tom F. Peters: The Swiss engineer designing: Robert Maillart, Christian Menn and Jürg Conzett on baudenkmaeler.ch
- Salginatobel Bridge. In: Structurae
- A world monument: Salginatobel Bridge Website of the Grisons municipality of Schiers.
- Worldmonument: Salginatobel Bridge
Individual evidence
- ↑ Schiers local plan ( Memento of the original from December 20, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on the website of the municipality of Schiers
- ↑ Numbers and facts ( Memento of the original from April 13, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on the website of the municipality of Schiers
- ↑ Salginatobel Bridge at www.graubuendenkultur.ch .
- ↑ The local map of Schiers gives 873.72 m above sea level. M., but the plans show 875.72 m, cf. Overview plan of the bridge ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ Technical data of the bridge
- ↑ Maillart's side view image no. Hs_1085-1929-30-01-168-01 from the ETH-Bibliothek on e-pics image archive online (click on the map to enlarge it)
- ↑ The abutment in the subsoil widens to 7.80 m, which may be the origin of various figures.
- ↑ Maillart's reinforcement plan, image no. Hs_1085-1929-30-1-2A of the ETH library on e-pics image archive online (click on the plan to enlarge it)
- ↑ Daniel Imhof: Les ponts de Robert Maillart ( Memento of the original from March 29, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Jost Auf der Maur: What if Graubünden were car-free. In: NZZ Folio . 08/08.
- ↑ Announcement of the Salginatobel Bridge on www.bernd-nebel.de
- ↑ Falsework of the Salginatobel Bridge
- ↑ Salginatobel Bridge ( Memento of the original from October 13, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on the website of the municipality of Schiers
