Inside Beijing's National Swimming Center

A multidisciplinary design team employed an innovative digital process to produce a surprising, highly integrated envelope-and-structure combination

The $100 million National Swimming Center in Beijing is clad in pillows of ETFE, a lightweight material akin to Teflon. LEDs are integrated into the pillow frames. Getty Images

by Joann Gonchar, AIA

The building's honeycomb exterior was designed to invoke the spirit of water. Getty Images

Cool air is pumped through an underseat system to keep spectators cool and dry. Solar energy heats the pools and the building and lights its interior. Getty Images

Story Tools

• post a comment
• e-mail this story
• print this story
• order a reprint
• suggest a story
• digg this
• save to del.icio.us

Of course, a facility meant to host the swimming and diving events for the 2008 Summer Olympics in Beijing should be all about water. But realizing such a concept in bricks and mortar is far from straightforward, and more challenging still if the designers intend to create more than a container, but hope to capture the "spirit" of water. "We wanted the building to dematerialize, to change moods, to react to changes in the environment around it," says Min Wang, a design principal with China Construction Design International (CCDI), a state-run design institute that worked on the project.

But despite the difficulty of realizing such an abstract goal, the National Swimming Center's international and multidisciplinary design team, composed of the Australian architecture firm PTW, engineers from the Sydney office of Arup, and a group from CCDI, managed to pull it off. They created a building that not only embodies some of the elusive characteristics of water, but one that tightly integrates skin, structure, and the performance requirements of an Olympic-level sports venue.

Naturally, the designers didn't use bricks and mortar for the $100 million, boxlike structure known as the Water Cube. The consortium, which was awarded the project through a competition in mid-2003, chose steel and a space-age plastic, ethylene tetrafluoroethylene (ETFE). The material, a cousin of Teflon, which the team used to create translucent pillows for the building's cladding, is strong and resistant to degradation from ultraviolet light and air pollution. By electing to envelop the building in it, the design team could treat the Swimming Center as an insulated greenhouse, capturing the energy from the sun for heating and lighting. ETFE was more appropriate for such a use than glass, the design team reasoned, because of better acoustic and insulating properties, and it is lightweight, which eliminated the need for a secondary structure to support the skin.

In order to create a building structure and ETFE enclosure with the desired references to liquid, the team members explored the geometry of soap bubbles, studying the work of Irish physicists Denis Weaire and Robert Phelan. In 1993, the pair proposed a solution to the so-called Kelvin problem (named after late 19th-century British mathematician William Thomson Kelvin) that asks how to divide space into an equal number of cells with the least surface area between them. Weaire and Phelan's "foam" is made up of a combination of polyhedra with either 14 or 12 faces. Despite its regularity, the honeycomblike structure was well suited to the team's goals because "when viewed at an arbitrary angle, it appears totally random and organic," says Tristram Carfrae, leader of the group of engineers from Arup.

Although Weaire and Phelan's foam forms the basis of the structure, there is only one spot in the building where their "pure" geometry is clearly recognizable—the second-floor Bubble Bar. Here, a collection of ETFE-clad polyhedra encloses a room where visitors can sip champagne.

Elsewhere in the building, the underlying geometry is hard to discern because of the team's form-finding process. In order to develop a building structure from the theoretical foam structure, the designers from CCDI wrote a script that would allow them to assemble an infinite array of the Weaire-Phelan units, rotate it in three dimensions, and then slice the packed cells to create a box 584 feet square in plan and 102 feet tall. They then removed three interior volumes for halls devoted to swimming and diving competitions, the pool for water polo, and the leisure center. From the foam left behind after this virtual cutting and deconstruction process, they created a space frame by replacing the edges of the polyhedra with steel tubes that meet at spherical nodes. They decided to encapsulate the space frame in 4,000 bubblelike, air-filled ETFE pillows to create a vented cavity 12 feet wide within the walls and one that is 25 feet deep within the roof, protecting the steel structure from the corrosive humidity of the pool environment.