Complex math for Oosterdok Island

The new building includes 65,000 sq. ft. of offices, 42 luxury apartments, 1,500 sq. ft. of hospitality and commercial functions and 30,000 sq. ft. of parking. ODE is to become a fully integrated urban campus according to architect UN Studio, who created an extraordinarily complex design for a building site the size of the proverbial postage stamp. So plenty of challenges for contractor Züblin and structural engineer Aronsohn.

ODE stands together with a series of high-tech companies such as TomTom and Adyen in one of the most distinct and beautiful locations in Amsterdam: next to the station and with its feet almost in the IJ. Views guaranteed. Not surprisingly, UNStudio created a highly transparent design for this prime location. "But definitely not a simple design," says Paul Lagendijk, senior structural engineer for Aronsohn. "It contains numerous peculiarities, cantilevers, exciting structures, different floor types and a contractor and steel builder who come from Germany. Then you discover that (steel) construction at the eastern neighbors goes a little differently than in the Netherlands."

The diamond-shaped cassettes are made with Plexiglas in the formwork.

Parking garage

The building can be divided into three sections: the underground parking basement of 2 levels, the substructure that runs from level 0 to 4 and the superstructure that stands on several steel table structures at the 4th floor level. The apartment building stands on a lower table that is 10 meters above street level. Lagendijk: "Underground, an existing parking garage for 1,200 vehicles is combined with a new section for 400 cars and a bike shed that has room for 2,500 bikes. The existing garage has been there for 15 years and was built with a piece of foundation for a once intended building. UNStudio's current design no longer resembles this. In the existing basement, therefore, newly poured 4-meter-high massive piles were installed based on the existing pile positions to get the correct distribution of forces for the new structure; a fun puzzle. For the new basement and the building above it, 1,600 piles were driven into the ground and a 120-millimeter-thick basement floor was poured on top of them. We had designed a 500-millimeter floor and piles at the columns. Züblin wanted to simplify the excavation and concrete work and so a thick flat floor was created."    

The walkway runs diagonally through the atrium.

Table construction

Above ground, the puzzles only became more complex. Casimir Slui, responsible for BIM projects at Aronsohn and project manager for ODE: "The substructure of the office section has 4 open layers containing large tree columns made of steel that support the superstructure. These complex columns, composed of solid steel plates welded together, branch 2 times, have a hexagonal twisted shape, are angled and protrude through the floor fields. As a structural engineer you then think to put the nodal points at floor level and make a connection with the floors there, but the design did not allow that. Still, we managed to keep the image-defining tree columns pretty slim."

Welding

It is perhaps even more exciting along Oosterdoksstraat, where the office section protrudes 14 meters above street level, supported by a series of Y columns, and at the northeast corner cantilevers up to 23 meters. Lagendijk: "In the Netherlands we are used to working a lot with knots in steel structures, but in Germany it is different. Instead of lattice constructions, steel construction company Spann-verbund made 16-meter-long and storey-high elements for the cantilevers out of 10-centimeter-thick steel plates. We discovered that German steel builders in general and Spannverbund in particular are used to welding a lot on construction sites. Constructively the result is the same, in terms of weight it doesn't make much difference either, only you have to take it into account in the planning. Welding 10-centimeter-thick steel takes time: 2 men spend 10 days welding a wall beam."

German steel fabricators are used to welding on site.

Cassette ceilings

Very attractive are the cassette floors on the entrance side on the 1st and 2nd floors. Slui: "These are column-free spaces with cassette floors 45 to 60 centimeters thick. The diamond-shaped cassettes were made with Plexiglas in the formwork, creating a very smooth end result in clean-work concrete. The beams of the connecting, 5.5-meter cantilever balconies on the south side are incorporated into the ribs of the cassettes."

The substructure of the office section has 4 open layers containing large tree columns of steel that support the superstructure.

Footbridge

Another structural feat is the nearly 40-meter-long walkway that protrudes diagonally through the atrium. Lagendijk: "This has become a beautifully slender work. The bridge rises at an angle and is 1 meter high in the middle and 40 centimeters high at the supports. In the middle of the construction runs a hollow tube shape with steel confetti as ballast. This structural section, as well as the tree columns, are complex parts that BIM software cannot handle. For that we use parametric programs like SCIA Engineer to calculate, Rhinoceros with Grasshopper to model it and then Revit to integrate it into the BIM model."

From level 4, the offices have a grid of 8.4 meters by 8.4 meters.

Grid

Everything under the level 4 table structure and the table structure itself are complex and time-consuming to make. In the superstructure, however, time has again been saved. Offices in the superstructure are mostly straightforward with steel beams, concrete columns in a grid of 8.4 meters by 8.4 meters and floor-to-ceiling glass facades in the column-free facades. The floors are filled in with ComFlor 210 floors 0.6 meters wide with a span of 8.40 meters and a floor thickness of 300 millimeters. These lightweight metal floor elements are finished with reinforced concrete. Lagendijk: "This allows very fast construction and the system is also relatively light." Henk Prins, director of ComFlor supplier Dutch Engineering adds: "Despite being 25 to 40 percent slimmer and having a low own weight of 300 kg per square meter, they can handle a relatively high load. Also important for the contractor is the high construction speed you can achieve with them. In this case, some 30,000 square meters of this type were applied. Then you can grab quite a bit of time savings."

In conclusion, Slui points out another floor detail: "The edges are poured solid from all outer walls inward a meter deep because all floors are bevelled tapered. A typical UN Studio detail, but again with many consequences on all kinds of connections. It is also the details that make this work interesting, not just the eye-catching structures."