Water Cube : balance between design and safety.

Delicate soap bubbles have been grouped into a cube surrounding the Aquatic Centre Beijing Olympics, or at least the image that they give. In fact, the National Aquatics Center, nicknamed Water Cube, is a robust all-steel structure built to comply with the most stringent seismic code requirements and can withstand snowstorms Beijing.

"When we first saw the design of the building, I thought, this will be fine, we are designing a swimming pool and not much in it that can burn, but then I learned it was not so. There are several positions consignees, both food and retail. Plus bars, nightclubs and restaurants. All are located along the main entrance and exit routes of the building, "says Dr. Marianne Foley, senior partner of Arup Fire in Sydney, Australia, who was responsible for the design of the fire protection system Water Cube.

" Besides, it's not only one of the venues of the Olympic Games. When the Olympics end , it becomes a recreation center for multiple purposes. During the development of the Olympic Games, there are 20,000 people inside the building , "he says . Then , the population drops to about 10,000.

Building measures are 400 by 250 feet ( 120 x 80 meters) and has a height of 100 feet (30 meters). To achieve the sight and feel of the design needed to create the Water Cube , Arup have had to design a building that does not meet the strict codes of prescriptive building force in China, both because it is a large structure not certified as fire resistant and built entirely of steel and also because of the unique construction materials were used to give a handmade format "bubbles" .

Handmade cube format

Since the structure is built entirely of steel, prescriptive building codes in force in China require you to be certified as fire resistant, which would have implied steel cover with fireproof materials .

" For steel, the options would be pulverized with a cementitious spray, and it would look just like a bowed or use intumescent paint . But there are 56 miles (90 kilometers ) of steel , so it would have been simply too expensive. So we knew from the beginning that what was wanted was a steel structure unprotected and that was fundamental to the whole building design , "said Dr . Foley.

Another component complicating the design of fire protection system Water Cube was the size of its fire compartments .

" The National Code of China to a building divided into small compartments of fire, as do most codes , but essentially to meet this meant that had concrete walls to the bottom in the middle of the pool. So there had to be a large single compartment on the pool deck . [ The second aspect to consider ] was the outflow , the travel distance to exits . Given the large number of people and size of the building, we exceeded travel distances [ required ] to an exit. Finally , due to the huge number of people, particularly during the development of the Olympic Games, the widths of our outings were lower than approve the code of China , "he says .

By implementing a performance-based design, Arup Fire began to consider those issues, one by one.

" [ Water Cube ] is fully protected by sprinklers , which has involved an interesting design challenge. Has [ systems ] smoke control so that fires are kept in small dimensions through suppression. We use smoke control systems to keep fumes away from the occupants and for our main roads remain viable conditions remain to allow occupants to evacuate , which might take quite a long time because they are not familiar with the building as it must travel a long way , "says Dr . Foley.

" We have an excellent system of detection, better than required in the code of China; again to compensate for long distances of travel , " he says.

It features smoke detection systems around the Water Cube , as well as systems that emit warning messages that will alert the occupants of the building on an emergency and instructs them on how to act .

"It's a smoke detection system that is standardized , in accordance with standards established by China in all areas of the building where there are combustible materials . The detection system is zoned based on smoke exhaust fans . Obviously , where we have smoke detection, we run the exhaust smoke and emit corresponding appropriate evacuation messages , "says Dr . Foley.

The parking of cars, located under the building, has a heat detection system . Arup also placed systems aspirating smoke detection in ceiling voids , in the spaces between walls of the main areas of the pool and in the lobby of multiple uses and below their ceilings , especially in all the high areas building , in order to provide early detection .

Fire hydrants around the building are connected to a large system of fixed water supply . Firefighters can connect hoses to the outlets of the hydrants and fire hoses available on spools viewers and fire brigades can be used , if necessary. The building is also equipped with a large amount of water guns for a more complete suppression of fires.

"The building is zoned for firefighters know which area should be addressed when they become aware of the existence of a fire. And part of the advantage of being so open, and have such a large space, at least in the vestibules of the pool is that it is almost obvious once you enter the place where they are going , "he says .

The exit is another aspect in which the Water Cube departs from the provisions of the codes of China. For a presence of 20,000 people in a building of this size , China code would require more than 328 feet (100 meters ) to the outputs.

" They will have 17,280 spectators during the Games time and 4,000 more, including officers, staff, athletes and others. [ In our analysis , we demonstrated that the Water Cube required only ] about 223 feet (68 meters ) to the width of the doors of the main input / output level , "says Dr . Foley.

During the development of the Olympic Games, the Water Cube seats will only consist of fixed stands. The biggest challenge was the design so that people would enter and would leave no accumulations occur in any sector along the route, which could cause oppression or inconvenience in moving the crowd.

"Also, because the people are sitting in a phased manner in these banks are at a certain height, so make sure to keep the product away from the high levels of the seats smoke while people are being evacuated [it became a priority]. This is achieved through two key elements, sprinkler systems to keep our size low fire and smoke exhaust systems, "he adds.

How bubbles are generated

The most distinctive design element of the Water Cube is one who from the beginning was an unsettling for China committee in charge of the design approval subject. Spread on top of the steel structure translucent plastic wrap made of ethylene tetrafluoroethylene (ETFE) is located. The ETFE is used in certain indoor areas and on the roof of the National Stadium (nicknamed Bird's Nest), too.

This material melts at a temperature of 520 ° F (270 ° C).

"It is an incombustible material is not a combustible material. It is somewhere in between. This makes it difficult to justify its use. For the stage, since such material is used in the roof, okay, because if a fire in the ceiling, the ETFE is fused, and is an open space. The smoke is released, and the space will become even safer, "says Dr. Ming Chun Luo, CTO of Arup Fire in Hong Kong.

"To the Water Cube, this material has been applied both in the walls and ceiling, which is correct. But among these, there are gaps that also use such material, and this is what causes a problem, because if a fire occurs, do not have a separation between the two spaces. Basically, we have a separation of fire in any of the indoor areas of these buildings, except for training rooms or offices. We have a separation of fire with public areas, "he says.

However, when Arup carried out the analysis of fire engineering, the company could demonstrate that the risk from the use of the material was of an acceptable standard.

"Obviously, since it is a plastic, has certain characteristics that are not particularly pleasant when burned, which is true for most materials. The advantage of ETFE is that the material is really thin, so that although the fire could cover a large area, not so much the material [that would be involved], "says Foley.

Building spaces are so wide that if a fire occurs in a place close enough to the front, ETFE melt, allowing ventilation of the building to the outside, he says.

The fire engineering analysis conducted by Arup demonstrated that it is possible to include interesting new heights in architectural design and that people can enjoy a unique experience in a safe environment fire.