ETH Zürich  |  DARCH  |  ITA  |  Structural Design  |  DOCTORAL THESES  |  TOKYO OLYMPIC STADIUM 
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Architectural and structural design: Pierluigi DʼAcunto, Lukas Ingold, Patrick Ole Ohlbrock

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A radically new structural solution has been developed for the new Tokyo 2020 Olympic Stadium that questions the layout conventionally used in stadium design. This proposal is part of an ongoing research project, which explores new structural concepts for large-scale infrastructures. Regarding the stands as the most important elements of a stadium, they are activated as loadbearing rings of a lightweight structure. Sequentially suspended one above the other, the two rings for the stands and the roof appear like floating elements in the air. Compared to the earlier proposals by Zaha Hadid Architects (2012) and Kengo Kuma and Associates (2015) for the same site, the developed solution drastically reduces the overall footprint of the stadium. The main parameters such as the structural requirements, the viewability of the spectators and the solar exposure of the pitch have been used to generate the final geometry of the stadium. This efficient and compact layout is able to accommodate 70í000 spectators and fully complies with the Olympic standards, including a 400m track and a standard soccer pitch. Owing to the innovative spatial arrangement of the stands and thanks to the tapered profile of the roof, the exposure of the pitch to direct natural sunlight is controlled and guaranteed throughout the whole year. The cable network used to support the floating rings generates a filter between the inside and the outside of the stadium working as a semi-open public square around the stands. Following a holistic approach to design, the accessibility to the stands is provided by stairs integrated into the cable network.

The structural concept consists in an innovative spatial scheme where solid rings made of lightweight composite materials hang from high-strength steel pre-stressed cables. Compared to Buckminster Fullerís Tensegrity and David Geigerís Cable Dome, where compressive struts are used to generate static height in order to redirect the tensile forces of the pre-stressed cables, in the present proposal the solid rings of the stands are designed to overtake this specific structural task. In order to maximize the compactness of the design, the rings have been arranged in a sequence of vertical levels, in such a way that each ring hangs from the subsequent lower one up to the main bowl located into the ground. This chaining effect leads to increased tensile forces at each level from top to bottom. In order to allow optimal viewability for all spectators, cables crossing the view lines are avoided and an alternative solution that takes advantage of the spatial potential of the stadiumís geometry is pursued. Hence, the necessary horizontal forces are transferred through tensile and compressive hoops, which are integrated within the sections of the stands. To avoid uplift, additional radial cables hold back the rings to the main bowl in the ground. Furthermore, in order to withstand horizontal loading such as wind or earthquake, the radial cables are crossed to increase their bracing effect. In this way, the rings act as multiple tuned mass dampers connected in series that are able to dampen out the oscillations that the structure would undergo during an earthquake. As such, the overall response of the structure to dynamic loading is a broad range of natural frequencies of vibration, which prevent the building from experiencing large and dangerous harmonic oscillating motions due to resonance effects.

The project has been selected among the winners of the IASS 2016 International Design Competition and has been presented to the public at IASS 2016 Symposium in Tokyo in September 2016.

last modified 23.9.2016