Krúsrak bridge over N7 moved to temporary work site

The fifteen-meter-high bridges named Krúsrak and Duvelsrak are constructed of accoya wood and were inaugurated in 2008. Straight lines cannot be found in the unusual, organic design. As a result, over the years they became an important part of the local Frisian landscape. However, problems with the protective coating, moisture intrusion and cracking forced RWS to take early action. To preserve the bridges, the woodwork and structural joints had to be thoroughly inspected, refurbished and given a new protective coating. "On site, that causes long-term inconvenience, by moving the object you limit that enormously," says Joris van der Zwaan, sales manager Infra at Wagenborg Nedlift, which also put the bridges in place in 2008.

Winning trajectory

Wagenborg Nedlift performs the relocation together with contractor CT deBoer, which itself takes care of the emergency bridge over the N7, the temporary bridge at the renovation site and the preparation of this work site. As a temporary bridge, CT deBoer constructed a steel emergency bridge to the work site in anticipation of the bridge change, resting on a number of heavy piles. Van der Zwaan: "But the first plan preparations began at our site as early as mid-2024. That led to winning the tender at the end of that year, together with CT deBoer. Our route was partly decisive in this. That starts with the over-the-road approach of a support system on two SPMTs, each traveling on a roadway. Under the bridge, this setup turns a quarter turn after which the bridge can be jacked off its foundation and driven out. It then turns back a quarter turn, travels several hundred meters along the N7 and then turns left to reach the work site via a temporary bridge over a ditch. The temporary bridge is then ready and will be transported and placed in reverse order to the clearing across the N7."

Unknown weight

On May 10, the relocation operation, prepared in detail, was successfully carried out: in one day the bridge change was completed. Because it cannot be determined how much moisture was drawn into the wood structure over the years, the weight of the bridge was not known in advance. Therefore, calculations were made with wider margins. More exciting still may be the condition of the bridge itself and what is found during the inspection. Then RWS can decide what to do with the other bridge. Should no insurmountable problems be encountered during the bridge renovation, Wagenborg Nedlift will put the Krúsrak back in place at the end of this year. The renovation work will be carried out by the combination Hupkes Wijma - Koninklijke Oosterhof Holman.