Hølen Viaduct

Historie

The Hølen Viaduct is a disused iron railway viaduct situated at Hølen in Vestfold, Norway. The iron carried a single track of the Østfold Line over the river Såna and the valley where the village of Hølen is located. The viaduct was the first pendulum pillar bridge in the world, and was designed by the principle's inventor, Axel Jacob Petersson. It is 130.6m long.The viaduct was built as part of the Østfold Line and opened on 2 January 1879. It was structurally strengthened through a pillar replacement program in 1914. From 1931 Hobøl Station was situated on its north end. A new section of Østfold Line opened on 21 September 1996, resulting in the viaduct and the old line being closed. Hølen Viaduct is still standing, but not in use.SpecificationsThe Hølen Viaduct is an iron pendulum pillar bridge which crosses Såna. It is 130.6m long and consists of fourteen spans supported by thirteen pillars. Two spans measure 8.9m, while twelve measure 9.4m. The bridge carried the single-tracked Østfold Line's and was situated 46.90km from Oslo Central Station. The entire viaduct was built on a curve with a curve radius of 470m.HistoryThe Østfold Line was the first railway in Norway to use iron as the main construction material for its bridges. This allowed the line to be built with several larger viaducts, the most prominent being the Ljan Viaduct. The design was placed under the construction- and bridgeoffice, which was led by Axel Jacob Petersson. During the design process, he devised the pendulum pillar principle. This method allowed for smaller pillars which could be prefabricated and then mounted easily at the cite, reducing costs significantly. The lower costs allowed for several viaducts to be built, which again allowed for less gradients, as embankments would be prohibitively expensive.