Narrow bridges

Norway installs temporary crossings after 14 wooden road bridges closed following collapse

The Norwegian Public Roads Administration is installing a number of temporary bridges in the country after taking the decision to close 14 wooden structures following the catastrophic collapse of the Tretten Bridge on Monday.

A car plunged into the river while a lorry got stuck when the Tretten Bridge in the Gudbrandsdalen Valley broke on Monday morning as two vehicles drove across it. Although no conductors were injured in the incident, the 150m structure was not built until 2012, raising questions about why the wooden and steel truss bridge failed so spectacularly.

As a result, the Norwegian Public Roads Administration took the decision to close 14 timber truss bridges while the cause of the bridge collapse was determined.

Of the 14 timber truss bridges, eight are located in Viken County, five in Innlandet County and one in Nordland County. Two of the road bridges were built in the mid-1990s, while the other 12 were all built in this century.

To help ease the disruption caused by the closures, the Norwegian Public Roads Administration has started installing temporary crossings at two sites; the Tveit bridge on the E16 at Vang in Valdres and the Moumbekken bridge on the national road 22 in Fredrikstad,

Collapsed Tretten Bridge

Norwegian Public Roads Administration Director Cato Løkken also confirmed that the department is “looking into the possibility” of another temporary structure near the Norsenga Bridge on the E16 in Kongsvinger. However, Løkken admitted that this might not be possible due to the length of the crossing and that it passes over a railway line.

Preparations for the installation of the temporary bridges are underway and the bridges should be in place within about a week.

The National Bridge Emergency Service of the Norwegian Public Roads Administration delivers the temporary bridges.

Temporary bridges will have the same bearing capacity as permanent bridges, but will be narrower and therefore have somewhat reduced accessibility.

After the Tretten Bridge collapsed, Arup Global Timber Specialist Andrew Lawrence said that everything at this stage was just speculation, the wooden parts of the bridge appeared to have been exposed to rain, which meant they were in danger of breaking down, and its primary load path was through wood tension bonds.

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