A 148 meter long bridge collapsed in Norway when a truck drove over it.
Tretten. A truss bridge called Tretten collapsed in southern Norway in August 2022.
The plywood and steel truss bridge at Tretten in Norway collapsed and fell into the Gudbrandsdalslågen river in August 2022. The bridge had only been in use for ten years, but was designed to last a hundred years.
The 148-meter-long and 10-meter-wide bridge collapsed when a fully loaded truck drove over it. The bridge’s longest span was 70 meters.
According to the research report that has just been completed, the bridge most likely collapsed as a result of a splitting fracture.
According to the research report, sufficient caution was not observed in the design, inspection and approval of the bridge. Short construction time, span lengths and reuse of the existing foundation were risk factors that were not sufficiently taken into account.
A “strong aesthetic emphasis” was also seen as one of the reasons for the collapse. The report says that the bridge was designed by architects.
Tretten Bridge was designed at a time when Norway was moving from old regulations to new Eurocodes, i.e. from national standards to European structural design standards.
A spalling fracture is the type of fracture that caused the roof of the exhibition hall in Jyväskylä to collapse in 2003.
In Jyväskylä, the collapse was caused by the fact that there were only 7 dowels in one joint in the roof truss, when there should have been 33. The collapse started here, but it progressed further due to a splitting fracture.
Split fracture refers to the tearing of the joint area from the wood along the outer rows of the dowel group, as described in the accident investigation report.
Not closed. Faults were noticed on the bridge, but the bridge was not closed. NICE
However, the splitting fracture was not treated in the Norwegian standard, based on which the Tretten bridge was designed in 2009–2011, the report from Norway says.
Tretten was not the first bridge to collapse in Norway. In 2016, a bridge called Perkolo collapsed in the country, which had a similar lattice structure to the one in Tretten.
After Perkolo collapsed, new calculations were made for the Tretten bridge. Clear errors were noticed on the bridge, based on which, however, sufficient measures were not taken. The Norwegian safety authority’s view is that the bridge should have been either closed immediately or weight restrictions placed on it.
“An important basis for risk management is that the precautionary principle should be applied when the consequences can be extensive and there is insufficient information on the matter,” the report says.
The story was originally published in Tekniikka&Taloude.
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