Water Cube – National Aquatics Centre, China
In July 2003, Australian-based architects PTW and engineering firm Ove Arup won the contract to design and build the 2008 Olympic National Swimming Centre in Beijing.
Construction of the $140m landmark project, nicknamed the "Water Cube", began in December 2003, and was completed in January 2008. The 80,000m² site is situated opposite the main stadium in the Olympic Green Precinct, which lies at the northernmost end of Beijing's north-south axis.
The design of the project associates water, as a structural and thematic leitmotiv, with the square, important in Chinese tradition and mythology. In daytime, the Water Cube shines as a blue transparent spectacle, while after sunset it is a crystal piece of architecture with LED-lit bubbles.
Conceptually the square box and the interior spaces are carved out of an undefined cluster of foam bubbles, symbolising a condition of nature that is transformed into a condition of culture. The overall appearance of the aquatic centre is a cube of water molecules.
Water Cube design history
Architects PTW and engineering group Ove Arup, both based in Sydney, designed the Water Cube in partnership with the China State Construction Engineering Corporation (CSCEC) and the CSCEC Shenzhen Design Institute (CSCEC+DESIGN).
As well as providing a multifunctional aquatics centre, the brief required extensive use of digital technology, energy-reduction and water-saving methods, as well as the incorporation of new construction materials.
With proposals from ten countries, including China, the US, Japan, the UK and Germany, three designs were shortlisted for the design competition. These were submitted by Chinese architects, Shanghai Xian Dai Architectural Design, Rafael Vinoly Architects from the US and the subsequent collaborative Chinese-Australian winning design.
The winning Water Cube, the focal point of the swimming centre grounds, measures 176m on each side, rising to a height of 31m. It holds 6,000 permanent seats with capacity for an additional 11,000 temporary seats to accommodate Olympic Games spectators.
The Ove Arup / PTW design plays on the geometry of water bubbles within a square form. The structure's shape is specifically designed to work in harmony with the circular main Olympic stadium by the Swiss architectural team of Herzog & de Meuron Architekten with China Architecture Design and Research Group and Arup Sport London, known as the "Bird's Nest", giving the area a visual "yin and yang" balance.
The square form was also used in acknowledgement of its significance in Chinese culture, architecture and town planning.
There are two parts to the Water Cube's structural framework – internal and external. The external structure forms the actual roof, ceiling and walls and comprises a flat web of rectangular boxed sections. These sections are then clad with the inflatable material transparent "teflon" material known as ethylene tetrafluoroethylene (ETFE).
The internal steel frame is based on the unique geometry of biological cells or soap bubbles. Ove Arup and PTW based this "soap bubbles" structural concept on a solution from two Irish professors of physics at Trinity College, Dublin, known as the Weaire-Phelan structure, whereby a recurring pattern of polyhedrons is packed together to occupy a three dimensional space in the most efficient way possible.
Over 22,000 stainless steel members form the sides of these "bubbles", which are welded at the joints to more than 12,000 spherical steel nodes. The benefit of this frame design, as well as resembling water bubbles, is that it is ideally suited to the seismic conditions found in Beijing.
Water Cube challenges
One of the challenges encountered by the designers was convincing Chinese authorities of the value of ETFE.
There were a lot of myths about the use of ETFE, regarding the material growing mould and being ineffective in muting external noise, which had to be dispelled. PTW managing director John Bilmon and his team put the claims to bed by conducting extensive tests and making some adjustments to the material that would reduce the acoustic impact of outside noise. The material was also shown to be superior in terms of lighting and thermal efficiency, and will protect the internal steel members from exposure to the harsh chlorinated aquatic environment – preventing their corrosion.
The use of ETFE will help the building last for about 100 years. The transmission of light and strength of the ETFE membrane deteriorates far less than other materials. The membrane is resistant to fire and severe heat, and possesses ductility and crushing resistance. It is self-cleaning in nature as the friction coefficient of the material prevents the dust from forming a layer on the material and rain can easily clear away the dust.
The building's envelope required 100,000m² of ETFE, making it the largest ETFE structure in the world. The ETFE used was produced by Vector-Foiltec of Germany and Yuanda Group of Shengyang, China.
The venue's design as an enclosed swimming gymnasium could have led to high humidity. This was addressed by taking a new approach to the air conditioning system. A stringent temperature and humidity control system, and a recycled hot water system were incorporated into the design. These help to air-condition the public area and the swimming pool. Indoor and outdoor air recycling systems, solar energy systems and deck ventilation systems maintain a comfortable climate and humidity of 50%-60% in the venue.
The designers also had to prevent dewdrop from the ceiling, which could affect the swimmers in the pool or divers on the springboard. The ETFE and air conditioning systems have partially helped to prevent dew dropping. Moreover, the building's air supply, return inlets and exhaust outlets improve the ventilation in the upper spaces of the building.
Where swimming pool systems usually pump water into the local wastewater networks as they backwash their filtration systems, the Beijing scheme runs the backwash water through a two-stage filtration system before returning it back to the swimming pools. This system is highly water efficient in the face of Beijing's sporadic rainfall patterns and potential low water levels.
The equipment used for the water system was not the specific equipment originally suggested by the designers. Locally manufactured hydraulic equipment that met design requirements was used in its place.
The ETFE cladding lets in solar heat, reducing energy costs by up to 30%. The design of the Water Cube allows 140,000t of recycled water to be saved a year.
The space between the air-pillow walls has been completely sealed off creating a layer of insulation. During summer, a 1m-high vent regulates the indoor temperature of the building through heat exchange by drawing out the inside warm air and letting in the outside cool air. The vent is sealed off during winter maintaining the warm temperature inside the venue.
At the time of design, PTW and Ove Arup envisaged the highly detailed structural members to be manufactured offsite and bolted together onsite, however a more traditional construction approach was taken by partners CSCEC.
The roof and walls were constructed in east-west strips on site, which were then moved into position. This enabled work to proceed on the building and roof construction simultaneously while preventing the need for any cranes or scaffolding within the pool halls, which may have damaged the pool structures and finishes, but the approach, says Bilmon, may have contributed to the delayed completion date.
The landmark building has been used since the Games as a multipurpose leisure and swimming centre that, as well as swimming pools, includes a gym, ice-skating facilities and a cinema.
The Water Cube hosted the swimming, diving and synchronised swimming events during the Beijing Summer Olympics 2008. The Beijing Olympics saw 25 world records broken in the Aquatics Centre. The Water Cube hosted sound and light shows in summer 2009 and became a ballet theatre to host Swan Lake. It was closed to the public for renovations from 15 October 2009.