Salginatobel Bridge
Encyclopedia
Salginatobel Bridge is a reinforced concrete
arch
bridge
designed by renowned Swiss civil engineer
Robert Maillart
. It was constructed across an alpine valley in Schiers, Switzerland between 1929 and 1930. In 1991, it was declared an International Historic Civil Engineering Landmark, the thirteenth such structure and the first concrete bridge so designated.
As with his Schwandbach Bridge
and Vessy Bridge, the structure's fame among civil engineers is a consequence of the techniques involved and the elegance of its design rather than its prominent location: it serves a town of about 2,500 people but has become a site of pilgrimage for designers.
in 1904. In the 51 metres (167.3 ft) span Tavanasa bridge, the arch is thinnest at its crown and springing points, thickening in between to reflect the shape of its bending moment
diagram. This bridge was destroyed by an avalanche in September 1927. Although Maillart didn't win the contract for a replacement bridge, he entered a competition the following year for the bridge at Salginatobel, with a three-hinged arch spanning 90 metres (295.3 ft) that used the same overall form as at Tavanasa. In conjunction with builder Florian Frader, Maillart's design was the least expensive of nineteen entries.
The Salginatobel bridge arch is 133 metres (436.4 ft) long in total, and its main element is a hollow concrete box girder
over the central part of the arch. It carries a roadway 3.5 metres (11.5 ft) wide, supported on reinforced concrete pillars above the ends of the arches.
The bridge was officially opened on August 18, 1930. Although regarded as a pioneering work, several aspects of its construction lacked durability, such as the absence of bridge deck waterproofing
, low concrete cover
and poor drainage. In 1975 and 1976 it was extensively repaired, the parapet
s were modified, and waterproofing was added. However, by 1991, deterioration had continued, with the parapets becoming unsafe. The waterproofing and drainage were replaced and amended, and most of the existing concrete surface removed and replaced by shotcrete
. The parapets were completely rebuilt. Completed in 1998, this repair work cost 1.3 million US dollars.
The bridge has received widespread attention since its innovative design and construction, including considerable praise from other bridge engineers, architects and architectural historians. Writing in 2000, Heinrich Figi said:
David P. Billington has been particularly enthusiastic about the bridge:
The German bridge engineer Fritz Leonhardt
has suggested that:
Maillart was not entirely satisfied with the bridge, writing after its completion that its soffit
should have been a pointed rather than a pure curved arch, if it were properly to match his structural analysis:
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
arch
Arch bridge
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...
bridge
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
designed by renowned Swiss civil engineer
Civil engineer
A civil engineer is a person who practices civil engineering; the application of planning, designing, constructing, maintaining, and operating infrastructures while protecting the public and environmental health, as well as improving existing infrastructures that have been neglected.Originally, a...
Robert Maillart
Robert Maillart
Robert Maillart was a Swiss civil engineer who revolutionized the use of structural reinforced concrete with such designs as the three-hinged arch and the deck-stiffened arch for bridges, and the beamless floor slab and mushroom ceiling for industrial buildings...
. It was constructed across an alpine valley in Schiers, Switzerland between 1929 and 1930. In 1991, it was declared an International Historic Civil Engineering Landmark, the thirteenth such structure and the first concrete bridge so designated.
As with his Schwandbach Bridge
Schwandbach Bridge
The Schwandbach Bridge is a deck-stiffened reinforced concrete arch bridge near Berne in Switzerland, designed by Robert Maillart and completed in 1933.- Design :...
and Vessy Bridge, the structure's fame among civil engineers is a consequence of the techniques involved and the elegance of its design rather than its prominent location: it serves a town of about 2,500 people but has become a site of pilgrimage for designers.
Design and history
Maillart had previously designed a three-hinged arch bridge over the Rhine at TavanasaTavanasa
Tavanasa lies in the municipality of Breil/Brigels, Graubünden, Switzerland. It has a station on the Disentis - Reichenau line of the Rhätische Bahn railway....
in 1904. In the 51 metres (167.3 ft) span Tavanasa bridge, the arch is thinnest at its crown and springing points, thickening in between to reflect the shape of its bending moment
Bending Moment
A bending moment exists in a structural element when a moment is applied to the element so that the element bends. Moments and torques are measured as a force multiplied by a distance so they have as unit newton-metres , or pound-foot or foot-pound...
diagram. This bridge was destroyed by an avalanche in September 1927. Although Maillart didn't win the contract for a replacement bridge, he entered a competition the following year for the bridge at Salginatobel, with a three-hinged arch spanning 90 metres (295.3 ft) that used the same overall form as at Tavanasa. In conjunction with builder Florian Frader, Maillart's design was the least expensive of nineteen entries.
The Salginatobel bridge arch is 133 metres (436.4 ft) long in total, and its main element is a hollow concrete box girder
Box girder bridge
A box girder bridge is a bridge in which the main beams comprise girders in the shape of a hollow box. The box girder normally comprises either prestressed concrete, structural steel, or a composite of steel and reinforced concrete. The box is typically rectangular or trapezoidal in cross-section...
over the central part of the arch. It carries a roadway 3.5 metres (11.5 ft) wide, supported on reinforced concrete pillars above the ends of the arches.
The bridge was officially opened on August 18, 1930. Although regarded as a pioneering work, several aspects of its construction lacked durability, such as the absence of bridge deck waterproofing
Waterproofing
Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...
, low concrete cover
Concrete cover
Concrete cover, in reinforced concrete, is the least distance between the surface of embedded reinforcement and the outer surface of the concrete...
and poor drainage. In 1975 and 1976 it was extensively repaired, the parapet
Parapet
A parapet is a wall-like barrier at the edge of a roof, terrace, balcony or other structure. Where extending above a roof, it may simply be the portion of an exterior wall that continues above the line of the roof surface, or may be a continuation of a vertical feature beneath the roof such as a...
s were modified, and waterproofing was added. However, by 1991, deterioration had continued, with the parapets becoming unsafe. The waterproofing and drainage were replaced and amended, and most of the existing concrete surface removed and replaced by shotcrete
Shotcrete
Shotcrete is concrete conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique....
. The parapets were completely rebuilt. Completed in 1998, this repair work cost 1.3 million US dollars.
Praise and criticism
- 1947, the bridge was featured with other of Maillart's works in a four-month exhibit at the Museum of Modern ArtMuseum of Modern ArtThe Museum of Modern Art is an art museum in Midtown Manhattan in New York City, on 53rd Street, between Fifth and Sixth Avenues. It has been important in developing and collecting modernist art, and is often identified as the most influential museum of modern art in the world...
, New York - Salginatobel Bridge was designated a Swiss heritage site of national significanceSwiss Inventory of Cultural Property of National and Regional SignificanceThe Swiss Inventory of Cultural Property of National and Regional Significance is a register of some 8,300 items of cultural property in Switzerland...
. - 1991, it was designated an International Historic Civil Engineering Landmark by the American Society of Civil Engineers
The bridge has received widespread attention since its innovative design and construction, including considerable praise from other bridge engineers, architects and architectural historians. Writing in 2000, Heinrich Figi said:
David P. Billington has been particularly enthusiastic about the bridge:
The German bridge engineer Fritz Leonhardt
Fritz Leonhardt
Fritz Leonhardt was a German structural engineer who made major contributions to 20th century bridge engineering, especially in the development of cable-stayed bridges...
has suggested that:
Maillart was not entirely satisfied with the bridge, writing after its completion that its soffit
Soffit
Soffit , in architecture, describes the underside of any construction element...
should have been a pointed rather than a pure curved arch, if it were properly to match his structural analysis: