A four-storey ‘crown’ placed on top of a former office building in the north of Amsterdam has turned the tower into one of the city’s biggest attractions, without the installation of new foundations.

When Shell moved out of its campus in the northern part of Amsterdam, it left a 17-storey office tower in need of redevelopment. Visionary developer Lingotto, together with three people from the music industry, won the tender and, rather than convert it into a hotel or more offices, planned something much more visible and high profile.

The vision was to create a building with multiple functions, including creative space, music and dance studios. They also wanted to make the most of the stunning view provided from the top of the tower. To do that, the building needed to be higher – and this was the challenge for Royal HaskoningDHV’s structural engineers.

Research helps identify where there is additional structural capacity

Any additions to raise the height of the building needed to be supported by the existing foundations and structure. The plan was to add a club and a revolving restaurant for floors 18 and 19 and two observation decks on the storeys above, capped with a decorative crown. With these additions, a straightforward office block would become a very special tower.

Through research, our structural engineers located calculations made for the original building enabling them to identify exactly where there was additional capacity to support the new floors. They also investigated the concrete and discovered it was higher quality than had been specified, which further increased capacity. With this information and their own calculations, they designed a solution which made optimal use of the extra capacity and needed no additional reinforcement.

Structural calculations also needed for swings on building’s roof

The new section was constructed from steel to reduce weight and had to be hoisted into position by a special crane. Because the crane needed to be ordered nine months ahead, there was pressure for completion by that date. Then, within the space of just one week, the whole structure was in place on top of the building.

The building was completed in 2016 and has become one of Amsterdam’s biggest attractions, not just for the view, but also for the giant six-person swings at the top. “We also did calculations for these,” said Carla Mulder, Consulting Engineer and Registered Designer. “You can swing over the edge and see all of Amsterdam, but they create forces on the building, so we needed to take that into account. They are so popular that we have done further calculations and a third swing has been added.”

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