18 Liebherr cranes involved in one of Germany's largest bridge modernization projects

The Rader High Bridge spans the Kiel Canal along Germany's A7 motorway, the northbound high-speed link from Hamburg to Denmark. The bridge is to be replaced and widened over the next few years. For the job, 18 Liebherr cranes, ranging from the 65 K to the 150 EC-B, are taking care of the lifting work. Some of the cranes have been erected in the water.

The replacement of the Rader High Bridge in Schleswig-Holstein is one of the largest bridge modernization projects currently underway in Germany. The bridge, built back in 1972, spans the Kiel Canal and is part of the A7 motorway. Measuring just under 1,500 metres in length, it is Germany's second-longest steel road bridge and plays an important role in the flow of traffic to and from Denmark and the Scandinavian peninsula. The bridge is approaching the end of its useful life because of high volumes of traffic, meaning that a rebuild and simultaneous widening of lanes has become necessary.

Cranes operating on water and land

Support for this construction project is being provided by 18 Liebherr cranes from the rental fleet of Friedrich Niemann GmbH & Co. KG. Five fast-erecting cranes, two 65 Ks, and three 81 Ks are on site to assist with the foundations. The new bridge piers are being built with the help of six 125 EC-B and seven 150 EC-B flat-top cranes.

Conditions on site are responsible for some spectacular crane assemblies. The first crane to arrive on the construction site, a 125 EC-B, was assembled at the end of 2023. Assembly took place in the waters of Lake Borgstedt, where the crane stood on the first pier's pile cap secured by foundation anchors. This involved working with a Liebherr crawler crane from Austria. The 250-tonne LR 1250 crawler crane required for the assembly was positioned on a floating platform between the crane site and the ferry used for transporting parts. The flat-top crane reached a hook height of 44 metres. Three 125 EC-B cranes were also assembled using the 250-tonne crawler crane, from its floating platform on the water. The cranes were initially assembled at a height of 30 metres and then climbed to their final hook height of 50 metres using hydraulic climbing equipment. This allowed them to work some 15 metres above the height of the roadway.

A 150 EC-B 8 Litronic started off working on the bridge pier on land. However, the progression of the site required the crane to be moved to a new location. At the end of June 2024, it was time: the flat-top crane was moved from the north side of the bridge to the next bridge column and reassembled in the water. The disassembled crane was transported to its new location on a ferry and put back together again with the help of a 220-tonne crawler crane on a floating platform. Once assembled, it climbed to a hook height of around 50 metres and reached a jib length of 40 metres. The crane can lift up to eight tonnes.

Strategic planning proves successful

Precise planning was required in advance for the use of the cranes, and Liebherr's project department for large and special projects provided support. A major challenge lay in the cranes being assembled by the crawler crane on the floating platform. As the permissible hook height of the crawler crane on the floating platform was restricted, the assembly height had to be kept as low as possible. However, a certain tower height was also necessary so that the cranes could be climbed. Various options and tower systems were investigated in the run-up to the project to find the best solution.

The configuration of the tower combinations was another major issue before planning crane operations; it was essential to prevent the towers from colliding with the newly erected bridge piers and any potential tower deformations. Consequently, the fast-erecting cranes are only partly utilizing their maximum hook height. The two 65 K cranes are in use with their tower retracted as they slew under the bridge, and the three 81 K cranes are also assigned to work under the bridge and at maximum height above it. Of the 13 flat-top cranes are assembled in a free-standing position on crosses and foundation anchors, some are set in concrete in the water. They are working with a hook height of between 49 and 68 metres.

Weather conditions present an extra challenge during construction work. The Rader High Bridge is closed to empty lorries and cars with trailers from wind force nine onwards (storms with wind speeds of 75 to 88 km/h). If the wind picks up further, it can be closed to all vehicles over 7.5 tonnes. In the event of a hurricane (wind force 12), the bridge is closed completely. The wind conditions therefore had to be taken into account in the cranes' static calculations.

Built in two stages

The Rader High Bridge is located east of the town of Rensburg, approximately 30 kilometres from Kiel and around 65 kilometres from Flensburg. Traffic currently flows across the Kiel Canal, Rader Island, and Borgstedter Enge (part of Borgstedt Lake) on four lanes and two hard shoulders. The bridge's piers stand both on land and in the water. Three piers are being erected in the water and require a foundation of 40-metre-deep bored piles.

The new build is happening in two stages with traffic flowing along the existing bridge and the Kiel Canal. The eastern half of the bridge is being built first, next to the existing bridge, and is expected to be opened to traffic in 2026. Following this, the original bridge will close and be demolished, with the western bridge section being built in its place. The new structure is being widened to six lanes and should be finished in 2031.

The bridge piers for the eastern replacement structure are being erected first. Steel parts for the substructure arrive as four-metre-long components and are welded together on land to create elements up to 80 metres in length. These are then pushed along toward the next pier using the incremental launching method, with one increment being one bridge segment. To do this, the piers have to be erected in advance of the launching process. Work has started north of the bridge and is progressing southwards towards Lake Borgstedt and across Rader Island in the direction of the Kiel Canal. There is also work underway to the south of the bridge on the banks of the canal.

Segment reaches the first pier

The first bridge segment reached the first pier in June 2024. This particular segment is 56 metres long, 14 metres wide, and six metres high. Hydraulic presses moved the segment, which weighs several tonnes, at a speed of nine to ten metres per hour southwards towards the first pier. The replacement structure will consist of a total of 14 sections, with one advancement planned for every six to seven weeks.