Sarp Bridge ( or ) is a series of bridges which span across Sarpefossen, a waterfall of the river Glomma in Sarpsborg, Norway. In the current arrangement, one bridge carries a pathway, one carries a single track of the Østfold Line and one carries two lanes of National Road 118. The road and pathway bridges are about long, while the railway bridge is .
The first bridge at the site was a brick suspension bridge opened on 25 February 1854. It was rebuilt as a multilayer bridge and opened with rail tracks on an upper truss level on 2 January 1879. In order to strengthen the railway, a new steel truss railway bridge opened on 9 May 1931. The former bridge was then rebuilt as a wider road bridge. An accident on 15 April 1940 caused the fire department to blow away one of the pillars, collapsing the superstructure. A new road bridge was completed in 1943. The two were supplemented with a separate pathway bridge in 1977. There are plans to replace the existing bridges with a four-land road and three-track railway bridge, scheduled for no later than 2030.
Specifications
There are three current bridges which cross over Sarpefossen, which is also referred to as Sarpsfossen. Upstream is a pathway bridge for bicycles and pedestrians. In the middle is a railway bridge and furthest downstream is a road bridge.
The railway bridge is officially named Bridge over Glomma at Sarpsfossen (). The steel truss bridge carries a single track of the Østfold Line, with the western end of the bridge situated from Oslo Central Station. It has an overall length of , including viaducts on both sides of the bridge proper. The main span is , with two side spans measuring . The total truss length is . Just east of the bridge the Eastern Østfold Line branches off at the now disused Hafslund Station.
Original bridge
The first bridge was a suspension bridge with two brick pillars. The original road bridge was long between the landfall. The main span measured , while the smaller ones measured . There were four cables each made up of wrought iron. The bridge was dimensioned to withstand a load of 320 kilograms per deck-meter. The bridge had an overall weight of about 360 tonnes.
The railway component made the original bridge into a multilevel structure. The bridge then had four brick pillars, which carried three truss spans. The tracks were above the roadbed. With viaducts the railway bridge reach a length of .
History
First road bridge
At the start of the 19th century the King's Road through Østfold passed through Hafslund and then continued along the southeastern bank of the river to Fredrikstad. A ferry service was offered at Sandesund, near the current location of the Sannesund Bridge. The ferry service was both expensive and dangerous, and it was not uncommon for there to be lethal accidents. The new Highway Act of 28 July 1824 stipulated that the road from Torsbekken to Tune Church did not have sufficient standard, and the town magistrate demanded in 1841 that a new road be built. It was in relation to this that the first demands for a bridge across Glomma was proposed, initially between Buene and Dombergodden. Soon a counterproposal was made, to place the bridge over the falls. An argument against this was that the bridge could be damaged if a lock burst further up along Glomma and there came an uncontrolled rush of lumber. However, the bridge across Sarpefossen would give shorter access from the areas east of the town, and it would be shorter, cheaper have better carrying capacity.
Proposals for state funding were issued by the municipality in 1844. Not until five years later was a detailed design of a bridge made, by Christian Vilhelm Bergh. The Engineering Brigade protested and wanted the entire bridge between landfalls to be built with a single span. This was rejected by the road authorities as it would more than double the construction costs. It was estimated to cost 36,000 Norwegian speciedaler, of which 25,000 was for the bridge and the rest for the auxiliary roads and administration. State grants were approved on 30 June 1851.