Footbridge Hirschen in Altendorf

<p>As part of the expansion project for the Churerstrasse between Altendorf and Lachen, a new pedestrian bridge is being built on the lake side of the existing road overpass at Hirschen. This serves to increase safety for non-motorised traffic.</p><p>The new bridge construction has a total length of around 60 metres and a usable width of 3.0 metres. It is being built as a three-hinged arch bridge in the style of the neighbouring twin bridges by Robert Maillart and complements the existing bridge ensemble in a considerate manner. These two separate bridges were built in 1940 as his last bridges. Due to excessive subsidence, they were each connected in 1953 with the help of a tension strip under the tracks and thus stabilised.</p><p>The materialisation of the new bridge was intensively examined together with the Canton of Schwyz, the SBB and the monument preservation authorities. UHFB (cement-bonded ultra-high-performance fibre building material) proved to be the ideal choice. This innovative material consists mainly of finegrained mineral aggregates (silica dust, quartz sand), cement and steel fibres. When mixed with water and a plasticiser, a concrete-like mass is achieved that enables the production of very thin components. Following the example of R. Maillart from 1940, the intention with this project was also to realise a structure that was as light and material-saving as possible.</p><p>The arch over the double track of the SBB with a span of 40 metres must be able to be built within two short night closures of the Zurich - Chur railway line. The bridge was therefore divided into four elements and prefabricated. The four components, each weighing approx. 25 tonnes, were assembled with the help of two mobile cranes in tandem lift.</p><p>The lightness of the bridge achieved with the use of UHFB - it weighs only a third of a normal concrete bridge - allows easier transport and assembly and also minimises the foundations in the existing poor subsoil.</p>