Challenging Berne project for Wolff tower cranes

In Berne, Switzerland, contractor Estermann hired three Wolff tower cranes, two 6031.8s and a 6015.8, to help construct the BäreTower, Switzerland’s tallest residential building. Once complete, the building will be 100 metres high with 152 rental apartments, a hotel and a medical centre.

According to crane manufacturer Wolffkran intensive teamwork was needed early in the planning phase as the job site was near the Bern-Belp Airport and this impacted the cranes selected for the job.

Wolffkran said the planning team opted for its Clear Cranes due to their lower assembly heights and maximum overall heights.

Both the crane assembly and operation had to be reported to the Federal Office of Civil Aviation and the two highest cranes were equipped with obstruction lights and warning sleeves on the slewing part.

Due to the immediate proximity of the construction site to a rail line, all three cranes were also fitted with a working range limitation to comply with the safety requirements of the railroad.

The highest crane, a Wolff 6031.8 Clear, was initially assembled to a hook height of 81 metres, then climbed and tied to the building twice during the construction process to its final height of 126.5 metres. It used a foundation anchor as a base while the two lower cranes used cross frames.

“Due to the design of the facade elements, the tie-ins could not be attached to the floor slabs as is usual but had to pass through window and door openings to be fixed inside the building,” said Johannes Eckert, head of sales at Wolffkran Schweiz AG.

The attachment points of the tie-ins on the building and crane tower had to be determined prior to the crane assembly and the foundation of the Wolff 6031.8 Clear calculated accordingly. The facades are installed in one go as soon a floor is completed, which is typically every seven days, said Wolffkran.

Wolffkran explained that the order in which the facade components are installed is fixed and a later installation almost impossible. Door and window frames of the affected facade elements have therefore been modified to allow for an installation around the tie-ins.