Salginatobel Bridge

46.9816666666679.7183333333333873Koordinaten: 46 ° 58 ' 54 " N, 9 ° 43 ' 6" O; CH1903: 773421/205919

Salgina brook

The Salginatobelbrücke is a road bridge in the canton of Graubünden in Switzerland between Schiers and the 1,250 m high Schuders.

The Robert Maillart in 1929 designed and built in 1930 of reinforced concrete bridge has become a technical and architectural feat of engineering and is now shown at the technical universities around the world as a teaching object. It is an excellent example of an economical and at the same architecturally elegant solution.

Location

The Salginatobelbrücke lies in the wake of community road from Schiers, a point situated at 654 m altitude in the country fourth place with around 2,600 inhabitants, to Schuders, one consisting of a few houses in the hamlet of 1,250 meters above sea level. The road runs high above the narrow valley of the Schraubaches Schiers through the hamlets of Montagna, angle, sub - Pusserein and Crausch to the bridge over the Salgina brook, which flows about 90 m below her in a narrow ravine to Schraubach. Since the bridge has become a destination for tourists and professionals, the community has created parking and a trail on the bridge at the bottom of the valley Schraubachstrasse.

Description

The lane bridge crosses the ravine with a single concrete arch, the very slim begins at the almost vertical rock walls and gradually stronger until it merges after about a quarter of the arc with the elevated bridge plate. The carriageway is seamlessly connected with their boundary wall, making the long straight line is visually emphasized over the arch. At the eastern end of the rock is so steep that the deck slab extends just above the arch at the west end it is extended to the less steep slope at six elevated fields.

Up close, it can be seen that the thin sheet plate is much wider than the bridge deck to the abutments and tapers towards the center in an elegant curved line until it reaches the same width as the deck slab at the apex and connected thereto in a striking block will. On the bow plate, but clearly separated from its edge, the two parallel longitudinal walls of the first open the box girder are arranged, which is in plan straight and considerably narrower than the deck slab. This longitudinal walls rise over three spans in a curved line until they reach the plate beams of the road and from there form a closed hollow box. Every six meters is used as a narrow transverse wall elevation of the roadway, the transverse walls are reinforced at their ends to posts, of which the outer sides are connected smoothly with the walls of the hollow box. Only the first partition on the arc approach expands downwards so that it reaches almost the width of the plate there is also wide arc. In the second and third fields, respectively, a further plate is installed between the transverse walls, but does not extend beyond the open hollow box.

For the viewer, this results in a number of different lines that reflect a varied and architecturally interesting picture of a light bridge.

Technical details

The whole, executed in 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. M. The clearance height above the creek bed is ( depending on the particular gravel layer ) is about 90 m. The roadway has a slope of 3 % and 3,97 m in a westerly direction, so that there is a difference in height of 3.97 m between the two ends of the structure.

The bridge is based on the model developed by Maillart system of three-joint hollow box girder and the stiffened rod arc.

The bow plate has a wingspan of 90.04 m with a rising height of 12.98 m; also it is in the gap, that is, between the fighters joints, there is a difference in height of 2.70 m. The bow plate is strong on the fighters 40 cm, under the closed hollow box up to the top but only 20 cm. In plan, the arc plate is 6 m wide at the fighters and tapers towards the bow apex to 3.80 m.

The 25 cm thick sidewalls of the hollow box are the fighters joints only about 40 cm high, in the three open fields of gore but enlarges rapidly, and reached the fourth pillar of approximately 3.60 m. From this pillar of the walls are seamlessly connected to the beam of the deck. The resulting closed box girder is on both sides of the apex of each 26.80 m long and 2.58 m wide; it is divided by transverse slices in a 8.80 m long section, which is at the apex only 1 m high, and in three more, each six meters long sections. The transverse slices of the closed hollow box are 10 cm thick. The transverse walls in an open crotch 12 cm, 14 cm and 20 cm thick. They are limited by pillars which are 60 cm wide, with the pillar on the sheet approach, however, is 70 cm wide. The open box girder and the transverse walls along with pillar are also 2.58 m wide.

The bridge plate is 3.80 m wide. On it are 15 cm thick boundary walls, so that a lane width of 3.50 m remains. It is enhanced by two bars that are 18 inches wide and as deep as 80 cm. The bridge plate extends beyond each side 61 cm above the box girder and the piers, meets in the arch apex but with the same width there arc plate.

In reinforcement plan the location of the reinforcing bars and the apex joint is presented.

History

Before the construction of the bridge Schuders could only be reached via a bridle path. With the construction of a road had begun only in 1928, bearing in mind that in the canton of Grisons automobile traffic was banned until 1925. On 12 July 1928 the cantonal building department issued a tender for the construction of Salginatobelbrücke. The company's offerings Florian Prader. & Cie., Zurich / Geneva for one designed by Robert Maillart bridge for a flat fee of CHF 135,000 was found to be the cheapest of offers received 19.

The construction of the falsework to another package price of 45,000 francs, the respected carpenter Richard Coray was commissioned from Trin, who had already created the frameworks of Reported viaduct, the viaduct and the Langwieser Gründjitobel viaduct. As Maillart had planned a very thin sheet tray, which took over a supporting function for the superstructure after concreting itself, Coray could provide a delicate, light falsework. The required wood was harvested in the community forest and prepared by only six workers on the basis of a bill of 1285 numbers, provided with holes, labeled, trial together and finally brought by horse and cart to the site. There, the beams were lifted with a small cable crane to its intended position and installed by the carpenters.

The concrete work began in 1930 with the sheet tray that has been einbebaut without interruption in only 40 hours. Here, the concrete had to be mixed by hand and put on both sides of the sheet with wheelbarrows in equal parts. In just three months, the entire concrete work was completed. In mid-August 1930, the falsework was lowered and the bridge opened to traffic.

1991 Salginatobelbrücke by the American Society of Civil Engineers ( ASCE ) for International Historic Civil Engineering Landmark ( milestone in civil engineering ) has been appointed. 1997/1998, the bridge was renovated and it renews the parapet.