Complex installation of Nacka Bridge, Sweden
ALE has successfully installed Nacka Bridge, weighing 1,650t, in Sweden.
Nacka Bridge, a curved arch bridge measuring 140m long, was installed in several phases using SPMTs and barges to transport the bridge and jacking equipment for the final installation procedure.
ALE faced the initial challenge of transporting the bridge, which was built on a narrow construction site located on the slope of a hill. In order to transport the bridge, turntables were used on top of the SPMTs to manoeuvre the bridge through the limited space available.
ALE positioned 32 axle lines of SPMT at the back of the bridge and 48 axle lines of SPMT were positioned in the centre to move the bridge 100m. The SPMTs at the front were used to drive the first part of the concrete bridge, leaving a small clearance between the arch ends and the concrete bridge. The front arch was far enough for the first barge to be positioned under the arch.
The first barge was positioned underneath the bridge arch, where it supported 960t of bridge weight, using winches which were connected to anchor points at both sides of the riverbank. By ballasting and extending the jacks on top of the barge, the weight of the bridge was transferred from the front SPMTs to the barge. On the barge, two jacks were used to support the load and stabilise the barge in the transversal direction.
The SPMTs were then removed from underneath the bridge, using the driving capacity of the SPMTs at the rear and the winches to keep the barge in sideways alignment. As the barge moved to the other side of the river, this allowed sufficient space for a second barge to be positioned under the bridge.
The second barge was positioned under the bridge using winches on the same supporting point as the front SPMT during transportation. By ballasting the barge, the load of the first barge and part of the load from the SPMTs at the back were transferred until the 1,300t bridge weight was on the barge. Strands were installed from the bridge to strand jacks connected to the barge, to stabilise the barge in a transversal barge direction.
The first barge was then removed using the winches and a tugboat as the bridge continued to move using the driving capacity of the SPMTs positioned at the rear of the bridge, until it was in its final position.
The bridge, measuring 25m high, needed to be jacked down 3.5m in order to set down the bridge on the abutment. The bridge, which was constructed on two A-frames with two beams that were supported by eight climbing jack towers, was jacked down to its final elevation using strand jacks to keep it horizontal in a transversal direction.
Once the load was set down on the first abutment, the bridge was then set down on a temporary support of the client’s in order to remove the SPMTs.
For the bridge to be jacked down, jacking towers with 500t climbing jacks were built under the SPMT support points and once the client supports were removed the bridge could then be jacked down to its final elevation.