The Secrets of "Water Cube"

After more than four years of construction, the Water Cube was made available on January 28, in time to host the "Good Luck Beijing" Swimming China Open.

Beijing This Month has tracked the building of the Water Cube since its inception. Below are some of the features of this magnificent wonder.

Cost-Effective Bubbles

This is the first time that ETFE membranes have been used as the surface of a building in China: a rare practice anywhere in the world. When the membrane concept was chosen for the building’s cover, there were some who worried that it could be fragile and might not look appealing.

“In the beginning we thought about the ETFE membrane because it saves money and effort,” said Zhao Xiaojun, one of the Chinese designers of the Water Cube. “We wanted this light membrane to replace the often-used glass to allow natural light to enter the building. Had we used it, glass would be much heavier, and we would have had to strengthen the steel structure, which would have increased the costs.”

“Besides, glass is difficult to install and maintain; many more scaffolds would have been needed during construction if it had been used. Instead, the membrane is so light that it only takes two people a short time to put up a bubble covering nine square metres.”

A German company used to sell the membrane material at between 400 euros and 500 euros per square metre. With its manufacture in China, however, the price was reduced to no more than 2,000 yuan (200 euros) per square metre. If glass had been used instead, the cost would have been about 100 euros per square metre more.

Strong Cushions

The roof and the walls of the Water Cube are made of 3,000 "bubbles” with air-filled layers of the ETFE membrane. The membrane looks fragile, but a cushion can resist the weight of a car and be stretched to three or four times its size.

However, the bubbles can be damaged by sharp instruments: even birds’ beaks and talons.

“The building is semi-transparent, so birds seldom want to land on it; but we still have a net of very thin iron wires installed so that birds will not hurt it when they fly by,” said Zheng Fang, another Chinese designer and a chief architect at the China Construction Design International.

“The membrane is not easily pierced,” Zheng said. “Actually, any damage with an area of below one square centimetre will not collapse a bubble. Computers follow changes of air pressure in every bubble and refill them with air when needed. In addition, air pressures inside and out are about the same, so the air will not press outward. Minor damage can be repaired by simply applying a special sticky tape to it.”

Breathing Building

The Water Cube is warm inside during a freezing winter with fans installed on the roof and ventilation openings at the foot of walls. “In winter the openings are fully or partially closed so that the warm air inside will not leak out and in summer the building will not be like a green house: hot and stuffy inside,” said Zheng.

Temperature monitoring facilities in the corridors transmit information to the computer that controls the ventilation openings.

House with Sun Shade

Beams of light can penetrate the nearly transparent ETFE membrane. “The trick is that sunlight should come in as much as possible in winter, but only as much as needed in summer,” said designer Zheng Fang. “There are about 100 million plating points on the surface, which separate and reflect light like a sun shade. Extra light and heat is kept out.”

There are fewer plating points on the northern side of the building where there is less sunshine, and more points on the eastern and western sides where the sunshine is strong. In total, the points cover less than 50 percent of the surface on the southern side of the building, and about 60 percent on the western side where more than 70 percent of the sunshine is kept out.

Fire Resistant

The ETFE membrane is flame retardant and self extinguishing, said designer Zheng. Its melting point is about 275 degrees Celsius. When the temperature nears this point, there will be many small holes on the surface of the membrane and the air in the “bubbles” will be allowed out. As a result, the trapped air will not become so hot that the membrane catches fire.

Even when it burns, the membrane is so light that its remains will be blown away by the hot air instead of falling onto the ground.

The Theory of Foam-Physics

Designers created the steel framework of the Water Cube based on the "foam-physics" idea, which was established by renowned British physician Lord Kelvin at the end of the 19th century. When designers of the National Aquatics Center decided to put this theory into practice, they attracted great attention among the world’s leading architects. Actually, almost everyone who has studied “foam-physics” came to visit the construction site on the Olympic Green.

Zheng Fang said the framework had no precedents, no criteria and no standards to follow in its design and construction. It even didn’t have an official name.

Steel rods had to be welded into either a 12-faced or a 14-faced structure and a steel ball welded onto it so as to make a “water molecule.” There are more than 20,000 such metal rods and 10,000 balls in the framework of the Water Cube. Construction workers found it difficult to piece them together.

“If we had not thought of a new way, the work would not have been finished before 2010,” said Kang Wei, president of the National Aquatics Center Company Limited.

After many attempts, engineers decided that a “matchstick” would be made first by welding a steel rod and a ball together. Then the many “matchsticks” would be assembled. In this way things became easy and construction continued to progress.

When the steel framework was completed, more than one month ahead of schedule, it finally was given a name, “Three-dimensional Multi-faced Durable Steel Casting,” and the practice has now become an industry standard.

When all of the scaffolds were dismantled, the overall framework sank by 81 millimetres, about one-third of the expected 240 millimetres. It was hailed as a “masterpiece of theoretical physics” by The Guardian of London.

Other Features

Long Life: The designed durability of the ETFE membrane is 30 years. Afterwards the bubbles can be restored rather than replaced.

Self-Cleaning: Rainwater can be used to clean the surface when the “bubbles” collect dust. The accumulated water will flow down off the roof and the bubbles.

Changing Colours: The Water Cube can even change colours. According to designer Zhao Xiaojun, LED lights will be installed in every “bubble” and the building can be all red when the Olympic flame is ignited at the Games’ Opening Ceremony. Screens can be set up inside the “bubbles” to give a live show of competitions inside.

Sanitized by Ozone: To ensure that the quality of water in the Water Cube meets the latest standards of the International Swimming Federation (FINA), the water in the swimming pools will be disinfected using ozone so that it will not emit odours or cause harm to a swimmer's skin. Recirculation of the pool’s water is controlled using a computer that also reduces the amount of water used by more than 50 percent compared with other facilities.

Recycled Bathwater: Bathwater will be sanitized and recycled for use in flushing toilets, cleaning garage floors and watering lawns. Nearly 70,000 cubic metres of water is expected to be saved every year. The lawns outside the Water Cube will be watered only at night when evaporation is least likely to occur.

Rainwater Collection: The Water Cube has a 29,000-square-metre surface that is capable of collecting rainwater; about 10,500 cubic metres of rainwater is expected to be captured and used.

Clean Moat: The moat around the Water Cube is treated so that the water will remain clean and free of algae: it is recycled every eight hours.

User-Friendly Facilities

“Visitors and athletes will feel completely comfortable in the Water Cube, besides being amazed at its look,” said Kang.

The user-friendly facilities also feature:

Amenable Temperatures: The temperature of the swimming pools is set at 27 degrees Celsius, and that of seats of the audience at 18–20 degrees Celsius. The humidity in air is kept at between 50 percent and 60 percent. In this way the athletes and the spectators will be comfortable regardless of the season.

Warm Floor: Athletes who walk bare-footed will not feel that the surface of the floor is too cold or slippery because special tiles have been used with heating systems installed beneath them.

More Toilet Seats for Ladies: There are 67 toilets in the Water Cube and women's restrooms have 10 percent to 15 percent more seats than the men’s. Each toilet has a separate entrance and an exit; the air from the toilets is directed away from the competition area.

Barrier-Free Lifts: Doors of elevators close much more slowly than those elsewhere. This will assist wheelchair users who can also stop for rest at some specially designed areas in corridors.

Standard Swimming Lanes: The length of 10 swimming lanes in the Water Cube has an allowance of two millimetres, much less than the one centimetre that is the international standard. The error of the 10-metre diving platform is just two centimetres, when an error of 10 centimetres is allowed internationally.

Bubble Bar for Bubble Lovers: A moat has been dug around the exterior of the Water Cube so that people are kept away from the facades’ bubbles. Inside the building’s public areas, spaces separate sports fans from the bubbles. But visitors can go to the Bubble Bar, the only place where they can touch the “bubbles.”

Post-Olympic Plans

What will happen to the Water Cube after 2008?

Kang said post-Olympic uses of the Water Cube were considered throughout its design and construction. It will be turned into a full-service water park where people can enjoy themselves.

Zhao Xiaojun wants the Water Cube to be “the most lucrative house in China.”

About 11,000 of its 17,000 seats will be dismantled after the 2008 Olympics, and two five-storey buildings will be constructed at the site for use as restaurants, clubs and gyms. There will also be a skating field as well as a “business corridor” for shops selling a variety of goods in the Water Cube.

The Water Cube will sell tickets at affordable prices. It will also serve as a training venue for professional athletes and sports lovers.

What People Say about the Water Cube

On the evening of January 31, the "Good Luck Beijing" Swimming China Open kicked off at the National Aquatics Center. Being one of the landmark buildings of the 2008 Olympics in Beijing, the Water Cube drew accolades from both sports officials and athletes from around the world. Foreign media also lavished good words on this beautiful building.

"This is an excellent facility and the finest aquatics centre I've seen at an Olympic Games,” said Kevan Gosper, the International Olympic Committee (IOC) Press Commission chairman after watching the first event of the test tournament on the evening of February 1. He said he thought the athletes would find it “awe-inspiring.” “The pool is out of this world, it seems like it's from another planet.”

Camillo Cametti, chairman of the Press Commission of the International Swimming Federation (FINA), also had high praise for the Water Cube. They fit in with standards of both the IOC and FINA, he said, adding that he is confident about the both the capability of BOCOG and the success of the Beijing Olympics.

About The Water Cube

The National Aquatics Center, or Water Cube, lies in the west of the B Zone of the Olympic Green. It is 177 metres long, 177 metres wide and 31 metres tall. It has two floors underground and four floors above ground.

During the Beijing 2008 Olympics, it will serve three disciplines: swimming, diving and synchronized swimming. Forty-two gold medals will be awarded there, trailing only the National Stadium (Olympic Stadium) where 47 gold medals will be awarded.

The Water Cube cost about 1 billion yuan. That it was funded with donations from overseas Chinese makes it unique among all other Olympic venues.

So far, donations of more than 900 million yuan have been received from more than 350,000 overseas Chinese in 102 countries and regions. All donors will have their names honoured in a garden beside the Water Cube, and large donors will be honoured with sculptures.