EDGE East Side Tower: (Still) Berlin's tallest skyscraper

When an architectural design from the Bjarke Ingels Group comes along, you recognise it: it looks playful, but from a structural point of view it is serious. The bold ideas of the Danes often give building contractors a headache, whilst spurring their inventive and tinkering spirit. The most recent example in Germany is the EDGE East Side Tower in Berlin. The terraced exterior cubature is visually striking and structurally challenging. And there were plenty of challenges beyond that: Lack of space, a tight schedule, limited crane capacity and the many semi- and prefabricated concrete parts around the core. The successful completion of the shell on time, despite all challenges, can be attributed in part to the strong partnership between Züblin construction company and Doka, which began during the early bidding phase.

Hybrid construction in the core shaft
The backbone of the EDGE East Side Tower is its reinforced concrete core, a hybrid of in-situ concrete and precast concrete components. Doka's technicians planned the formwork solution entirely in the BIM software Revit during the planning phase in order to identify and avoid possible disruptions and to ideally coordinate the formwork cycle with the site cycle. There were plenty of tricky tasks. One was to meet the high demands of the fair-faced concrete surface, while maintaining the tight schedule on the construction site. Perhaps the greatest challenge was the technical implementation of the hybrid solution. On the one hand, there was extremely little space to position the formwork – the site crane was located inside the shaft, where the core formwork was also moved hydraulically with the climbing system. On the other hand, the crane’s capacity was very limited. However, the crane was necessary to integrate the precast elements into the climbing formwork, among other things. For this reason, the site and Doka coordinated precisely in order to use the buffer times when the crane was not in use for placing the formwork and to thread the precast elements.

The support of Doka's formwork instructors and colleagues from the formwork pre-assembly department was vital for the delivery and assembly of the climbing formwork and protection shields. A representative from Züblin commented that progress was made safely and swiftly thanks to their experience. The hydraulic climbing system Xclimb 60 was used for the first time in monolithic construction (slab-wall method) to build the core, which was combined with the Top 50 core wall formwork.

Save and fine-tuned operations
At the outer edge of the slab, the site crew was protected by a crane-guided protective shield. By combining scaffolding tubes with coarse- and close-meshed nets, it was possible to reduce the shield's dead weight and its wind-attack surface to a minimum. The stair-like recesses on the façade were a particular challenge for Doka's engineers, as the usual anchoring points for the shield became inoperable. Doka's solution was to mount a telescopic strut on the protective shield. This meant that only one floor-slab support level was needed in height. The protective shield protruded over two storeys with a height of 8.84 m above the previous concreted slab. With this solution, the crane lifts could be reduced by half.

Due to the low slab thickness of 18 cm and the prefabricated construction method, close coordination between Doka, the site managers and the structural engineer was essential. The Doka statisticians, for example, checked the bearing loads on the respective floors and were thereby able to produce a detailed load specification for the structural engineer in order to ensure the safety of the load transfer inside the structure. In practice, the shields were installed by Doka's formwork pre-assembly team at an assembly site about 1 km away and hung on the structure on site just in time. The site managers worked with Doka to develop a special transport trestle that was mounted on a low-loader to meet the logistical challenge of transporting the fully assembled – and thus very large – elements from the assembly site to the site crane under a bridge.

The construction process went so smoothly that the shell was completed several weeks ahead of schedule. This strong cooperative partnership will be continued on the construction of the MYND Tower on Berlin's Alexanderplatz, for which Züblin and consequently Doka were able to secure the contract. Here, the partnership was underpinned in the bidding phase by the award of the shell construction work.

The EDGE East Side Tower is scheduled for completion this year. It has already been given its glass shell, and work is currently underway on the interior fittings. Amazon will be the largest tenant.