Sensors can provide safer reopening

Cautus Geo recommends sensor technology when reopening closed truss bridges after the Tretten collapse on 15 August. "Closed bridges can be instrumented and contribute to a controlled reopening," says Lars Krangnes.

- "If closed truss bridges show signs of abnormal behaviour, they can be closed at short notice with automatic and continuous monitoring," says Lars Krangnes in an interview with Avisa Valdres.

The Øyer bridge in Gudbrandsdalen collapsed on Monday 15 August. The following day, 14 wooden truss bridges were closed. Tveit bridge on the E16 in Valdres is one of the bridges that was urgently closed.

Instrumentation

Avisa Valdres has put the spotlight on possible instrumentation to ensure the safety of road users. Krangnes tells the newspaper that the bridge can be instrumented within a couple of days.

- Instrumentation can reveal whether bridges exhibit abnormal behaviour. If the movements deviate from normal, they can be closed at short notice," he says.

Cautus Geo has experience in bridge instrumentation. On 15 April last year, the Nore Bridge on County Road 120 near Moss was closed due to the risk of collapse. A few days later, it was reopened. By then, Cautus Geo had instrumented the bridge and the surrounding ground conditions.

- The sensors we would use are used for similar monitoring of bridges in other countries," says Krangnes, technology and development manager at Cautus Geo.

Sensors

- "We can install sensors at various points on the bridge and measure how traffic affects stability. If there are any abnormal changes, they will be detected automatically and the bridge can be closed at short notice," says Krangnes to Avisa Valdres.

The Norwegian Public Roads Administration is working to replace the closed bridges with steel bridges that are partially built over the closed bridges. At the same time, extensive inspections have been initiated. Øyer bridge was inspected this summer, but collapsed a few weeks later.

Cautus Geo uses technology and methods that are also used to monitor bridges and structures in other countries.

- It is an established and well-documented measurement technology that is used to a much greater extent in other countries. We believe the closed bridges can be reopened faster and in a more controlled manner with instrumentation," says Kranges.