Crowned by a spectacular roof, the Sony Center is the heart of Potsdamer Platz

An innovative roof

The architect wanted the roof to cover the plaza like an umbrella. The plaza was not meant to be sealed, nor should it disconnect user from an outdoor experience.

The exceptional glass membrane roof rests on a ring beam weighting 500t. The alternating application of glass and fabric on a cable structure spans 102m. Structurally, the roof resembles a bicycle wheel in a horizontal position with a hanging central 42m-long kingpost creating a column-free plaza.

Prior to the detailed design of the roof, Arup conducted an environmental study that used wind tunnel tests, dynamic thermal modelling and computational fluid dynamics analysis to assess comfort levels within the space.

Daylight study

Arup carried out a daylight study using computer simulations. The Berlin building authority required rigorous proof that the plaza roof would meet Germany’s strict daylight requirements for the many offices and flats that faced the plaza under the roof.

The challenge was to precisely model the complex passage of natural light through the roof and by inter-reflection into the offices and flats. Daylight levels in individual rooms had to be predicted and compared with the code requirements.

Arup met this major challenge by applying innovative ray-tracing computer techniques to support established daylighting design experience. Our engineers developed a methodology that determined light levels in a few key rooms and from which conclusions could be drawn on the conditions in all other rooms in each building.

A highly detailed 3D computer simulation was generated, including the complex geometry of the roof and physically accurate modelling of the transmission and reflection of light from the roof and building façades.

The load-bearing system

A continuous ring beam was positioned along the edge of a tilted cut through a hyperbolic cone, resembling the rim in a bicycle wheel.

The two top cords of the triangulated ring beam follow the surface of the hyperbolic cone. The ring beam is elliptical in plan with spans of 102m in the main axis and 78m in the minor axis.

A 42.5m long kingpost was arranged in the tilted axle in the bicycle wheel. Two radial layers of cables connect the top and bottom of the kingpost with the ring beam. The top layer ridge and the valley cables create the folded surface of the roof. The bottom layer of the cables, the kingpost cables, suspends the kingpost over the plaza.

The whole system is prestressed to stabilise the surface created out of cables, fabric and glass. The ring beam is supported vertically at seven points on the top of the roofs of the buildings surrounding the plaza. Horizontally, the support configuration is structurally determined to avoid locking any forces from the roof acting into the buildings or vice versa.