In Norway, This Wooden Bridge Was So Beautiful It Wasn’t Strong

A big scare, but fortunately no casualties when the Norwegian bridge at Tretten, in the Øre region in the south of the country, gave way due to the weight of a truck crossing. The driver of the truck and the driver of a car had to be rescued, none were injured. The accident occurred in August 2022, exactly 10 years after this glued-laminated wood and metal equipment was put into service. The Norwegian Security Investigations Authority (NSIA) recently published its findings, As reported by Dezeen, a site specializing in architecture,

“The investigation revealed that inadequate care was taken during the planning, design, inspection and approval of the Tryon Bridge to take into account the risk factors associated with its unconventional design”, the report says. He also condemns it “Strong concentration on the aesthetics of the work” Which, combined with the choice of materials and the conditions required for this project (rapid construction, re-use of columns and length of spans), led to disaster.

a weak diagonal

An old report pointed to the weakness of one of the wooden diagonals which had weakened over time before breaking. The Tratten Bridge was designed at a time when Norwegian building regulations were in transition from a national system to a European code. At that time, national standards could still be applied, although, unlike the European version, they did not take into account “block shear failure” which was fatal to the bridge.

The bridge, at the time of its grandeur. Photo credit: Jan-Tore Egge

Another bridge of similar design, the Percolo Bridge, had already collapsed in 2016. The designers of the work, the firm Plan Architektur and the engineering company Norconsult, nevertheless estimated their construction lifespan at a century. Asked by Dezeen, the architectural firm believes the collapse is due to “Imperfect Rules” Of time. “Aesthetics were determined by structural and compositional considerations, Architect Yngwie Artun explains. This was not a decisive issue for deciding on the structure in the planning process. Nevertheless, 4 bridges, similar to Tretten, will be rebuilt while 9 others are still closed or with restricted access.

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