A temporary bridge to replace the collapsed wooden steel truss Tretten Bridge in Norway is expected to be open by the end of June.
The 148-m long temporary bridge will cross the Lågen River and the E6 highway at Tretten and be fixed on three foundations of the original bridge, as well as two new foundations.
In August last year, the 150m-long, 10m-wide Tretten Bridge – only a decade old – broke in two, collapsing into the river stranding two vehicles and their occupants. There were no casualties or injuries in the early morning accident on August 15, but one driver was airlifted to safety.
Late last year, a preliminary investigation by the Norwegian Safety Investigation Authority suggested that the cause of the Tretten collapse was “a break in one of the diagonals in the main span towards the western river foundation”. This could have caused overloading and unloading of other elements in the truss, leading to a failure.
Since the Tretten Bridge failure, the Norwegian Public Roads Administration, Statens Vegvesen, has been working hard to set up temporary bridges across more than a dozen structures similar to the Tretten Bridge while is carries out third-party safety checks. Some bridges have been reopened while others are having further tests.
The Tretten Bridge was a truss bridge with two lanes and asphalt pavement. The upper and lower girders and angle and cross braces were made of glulam, while the vertical rods were made of steel.
