The winning designer was the German architect Ingo Schrader from Berlin, who worked closely with the German structural engineers Bollinger + Grohmann. The draft included circular roofs with a diameter of about 82 ft, supported by pyramid-shaped columns. In August 2013, the roof construction was finished on the northern gate.
Roof Structure for Northern Gate
In the course of further planning, the circular shape was redesigned as an oval in order to adapt to the local conditions. Its size is 138 ft x 59 ft with a maximum lamella depth of 23 5⁄8 inches. The roof cantilevers up to 33 ft and is only 62 13⁄64 inches thick on its edge.
The four columns are placed in an irregular grid. Their pyramidal shapes visually represent the downward force distribution in the columns. Due to their triangular shape, they appear particularly slim and the roof gives the illusion of floating.
The roof supporting structure was generated and optimized by means of a computational model. One may have the impression that the axes of the load-bearing lamellas are randomly arranged. However, their arrangement is the result of a computer-based design process where structural, formal, and manufacturing boundary conditions were brought in line.
Then, the lamellas were optimized in height and width. In this optimization process, RSTAB was connected with the Rhinoceros design program using an individually created VBA script. A special algorithm iteratively reduced the cross‑section dimension of the flat steel lamellas on the basis of the occurring equivalent stresses.
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