Salginatobel Bridge

The Salginatobel bridge, which spans a valley in Schiers, a municipality in Canton Graubunden, Switzerland, was designed by well-known Swiss civil engineer, Robert Maillart. The reinforced concrete arched bridge, constructed in 1929/1930, was designated an International Historic Engineering Landmark by the American Society of Civil Engineers in 1990. The total length of the arch is 133 metres, with the main structural element a hollow concrete box girder over the centre. The road across the bridge is supported by reinforced-concrete pillars in the places where the arch dips at each end of the structure. In 1904, Maillart designed a three-hinged arched bridge over the River Rhine in Tavanasa, also in Graubunden. This was swept away by an avalanche in 1927 but Maillart was not chosen to design the replacement. However, in the following year, he won first place among 19 entries for the design of the new Salginatobel bridge, based on the same type of construction as that at Tavanasa. Although the Salginatobel bridge was regarded as a pioneering masterpiece, it was lacking in some basic aspects of construction, especially in terms of waterproofing, thickness of concrete cover over the reinforcement and efficient drainage. The bridge underwent extensive renovations in 1975/1976 but by 1991 had further deteriorated and become unsafe. Much of the concrete surface was replaced with Shotcrete and parts of the bridge were also completely replaced. Well over one million dollars was invested in the work, which was completed in 1998.