From water to ice, water cube "Metamorphosis"

This past New Year's Day was a big day for all those who were busy with the Venues of the Winter Olympics: all the venues of the Beijing Winter Olympics were fully completed by December 31, 2020.

The National Aquatics Center (Water Cube) is the first venue to be completed and renovated, and it is also the first time in the world to use intelligent technology to establish a pool conversion ice rink. Now, it has a new name – "Ice Cube".

Time back to July 31, 2015, the hosting rights of the 2022 Winter Olympics were spent in Beijing. According to the plan, the Water Cube will transform into the "Ice Cube" to undertake curling competitions – in the most famous venue in China, the crystal clear blue membrane structure, entertaining visitors from all over the world, everything seems to be perfect.

Unexpectedly, this preconceived decision put the fate of the Water Cube in a dilemma: the Curling Competition of the Winter Olympics has always been frozen on the concrete structure, and if it is to be held in the Water Cube, it can only completely abandon its original function and pour concrete in the pool.

As a result, the Water Cube will no longer have "water".

On the one hand, it is one of the important Olympic legacies of the Chinese people with special feelings, the "world's fastest swimming pool" that has created 24 world records; on the other hand, the strict standards of curling venues, the strict control of the International Olympic Committee and the solemn commitment of "scientific and technological winter Olympics, green winter Olympics".

Water or ice, summer or winter – this difficult proposition of choosing one or the other is in front of the Winter Olympic team.

Where does the Water Cube go from here?

"Without water, there is no soul"

Abandoning the swimming pool, Yang Qiyong, general manager of the National Aquatics Center affiliated to Beijing State-owned Assets Corporation, is the most unacceptable.

Since 2004, he has been working at the Water Cube. At that time, the Water Cube was still a vacant lot, and the "blue landmark" that would later be located on the west side of the central axis was still stuck on the drawings of the stadium design plan that had just won. Starting from a field engineer, Yang Qiyong personally experienced the rise of the venue, the 2008 Olympic event, and then thousands of days and nights of venue operation, countless people came to visit. To date, Water Cube has received 27 million visitors and hosted more than 1,600 events.

Joining the bidding team for the Winter Olympics, the unique temperament and influence of this venue have been unanimously loved by the International Winter Olympic Games and international curling organizations. "The bidding team asked us if it was okay to do curling competitions, we watched the video on the Internet, and felt that compared with ice hockey and speed skating, curling did not have much amplitude of movement, and should be easier." Yang Qiyong recalled.

The reality is very different. After determining the undertaking, everyone realized that the original curling competition was an extremely difficult "hard bone", which had extremely high technical requirements on the venue and required a solid concrete base.

This is also a clear requirement of the International Curling Organization. At the end of 2015, the International Curling Organization sent people to the Water Cube for the first time, and asked to pour concrete in the pool.

Once poured, the pool is abandoned, meaning abandoning the Water Cube's Summer Olympics function.

In the narration of Zheng Fang, the chief designer of the design and deputy chief architect of the Beijing Architectural Design and Research Institute, all kinds of reluctance can be felt.

"Guo Jingjing and others won the gold medal there." He pointed to the ten-meter platform in the distance, "The Chinese diving 'Dream Team' won all the gold medals except for the men's 10-meter platform." ”

The glory of the pool is like yesterday. "In 2008, athletes broke 21 world records 24 times in this pool. Phelps alone won 8 gold medals. "There's also a splash park over there, which children especially like, and there's even a baby pool." ”

"Water is the soul of this building," Mr. Zheng repeatedly said, "and all of its designs are related to water." Everyone came here to swim and play in the water. You see the bubbles on the roof above, the polygonal air pillows that wrap around the steel structure of this house like water molecules. Inside and out, from structure to function, it's all about water. Without water, the house has no soul. ”

For a decade, international swimming and diving competitions have been staged every year as scheduled, "when the audience arrives, it is broadcast on TV." Yang Qiyong said.

In addition to being "emotionally difficult to accept", he also has a real "economic account" in his hand: relying on the aura and pull of the Summer Olympic Games, as well as people's love for the Olympic heritage, Water Cube's tourism revenue reaches one-third of the total revenue, which is second to none in China. Once the track is demolished destructively, the equipment and machines invested in tens of millions of dollars in the background will be abandoned, and the cost is huge.

If you don't want to pour concrete, there is no other way. The preparation time flowed through everyone's unwillingness and contradictions.

Yang Qiyong knows that he can't wait for "death" and wants to save the pool!

At the beginning of 2016, the contradiction was already on the string. Two old friends who have been fighting side by side for years wander by the pool. In the meantime, a bold idea flashed: can you swim in the summer, skate in the winter, and turn the water cube into an "amphibious"?

"Water ice conversion", an unprecedented practice in the history of the Olympic Games, brings hope of breaking the game.

"Hard to get" ice

As the name suggests, "water ice conversion" is to add new ice functions on the basis of retaining water functions, and realize the interchange of water cubes and "ice cubes".

This is not the idea of the Flying Immortals. With many years of experience in construction engineering, structural engineer Yang Qiyong is confident of laying a detachable stable support structure in the swimming pool.

But up to the ice, there is no bottom.

Prior to that, there was only one Japanese swimming pool in the world that had laid a simple ice surface on the pool in the 1990s for people to skate and entertain, but the recreational nature of ordinary skating and Olympic-level curling competitions was as difficult as mud and clouds. What is even more frustrating is that at that time, the domestic research on the performance of the ice surface was still blank.

The "ice" of curling competitions is very exquisite.

If you've ever touched the track, you'll be surprised that it's not a smooth ice surface, but a myriad of tiny particles, varying in size and unevenness, which together make up about half of the ice rink. Curling glides quickly on a "cobblestone road" covered with ice points.

The ice layer, which is 45 meters long and 4.75 meters wide and has a thickness of 4 to 5 centimeters, is actually like a "cut cake", and the ice maker has to lay each layer of structure in order. From the bottom ice to the refrigeration pipeline, and then to the competition ice surface, each time the ice is made, the international top ice maker usually spends about 10 working days to pour the treated pure water dozens or hundreds of times with a thin water pipe, finely leveling, spraying water mist, forming a freezing point.

The curling track is also not an eternal horizontal ice surface, and the surface of the track changes subtly as curling slides on the track, the icemaker repeatedly fixes the ice, and even a slight change in the indoor environment.

In Zheng Fang's words, ice is very "sensitive."

Curling competition requires the humidity of the venue to be below 30%, the ice surface temperature is about minus 8 degrees Celsius, the air temperature of 1 meter above the ice surface is 10 degrees Celsius, and the temperature in the museum is within 16 degrees Celsius, which will directly affect the friction coefficient between curling and ice. The curling hall is filled with lights, cameras, and seats of varying numbers of spectators, who generate a lot of heat and have a variety of effects on the ice. In short, the air temperature, humidity, and distribution of the air flow field affect the quality of the track at all times.

Therefore, to hold a curling competition in the Water Cube, not only is it "frozen out of the standard ice", but the temperature, humidity, ventilation, energy saving and so on in the venue are facing a comprehensive transformation.

The "uncertain future" China solution

In April 2016, the International Curling Federation hosted the Men's Curling World Championships in Basel, Switzerland, and invited Yang Qiyong and Zheng Fang to watch the competition and learn from the experience. Yang Qiyong knew that the time had come for "short engagement". They took the Water Cube "Water Ice Conversion" scheme to Basel.

As soon as I entered the door, before I submitted a plan, the technical representative of the World Curling Federation first gave a page of paper and wrote 29 technical standards. That was the first time that Yang Qiyong and Zheng Fang had seen the world's universal standards of curling, and it was also the first time that they had experienced the severity of the situation: in contrast, the Water Cube was almost not satisfied.

The fifth article even clearly states that the World Curling Federation prefers to use concrete base layers, and other schemes should seek consent.

The concrete substratum is routine and secure. The "Water Ice Conversion" scheme envisages a standard curling field in the original pool track by building a convertible structure and installing a detachable ice making system. After the winter, the structure is removed and returned to the pool.

No one knows what the "Chinese plan" for the innovative use of this sports venue is.

"You can only go in, you can't retreat, there is no other choice." Yang Qiyong described the mood at that time, "We expressed our rejection of the cast-in-place concrete scheme and hoped to give the opportunity to do experiments on water ice conversion. If all the criteria are not met, there is unconditional obedience. ”

The military order was handed out, and the water cube temporarily "escaped a disaster."

"Ice and Water Double Heaven"

As the main water sports competition venue of the 2008 Beijing Olympic Games, the total construction area of the Water Cube is 65,000 to 80,000 square meters, and the construction area of the underground part is not less than 15,000 square meters, with multiple swimming pools, jumping platforms, and a water park that occupies half of the area.

From the high temperature and high humidity swimming pool environment to the low temperature and dry ice rink environment, it can be described as "ice and water double heaven", and the technical difficulty and engineering complexity of the transformation are far beyond imagination.

Building a conversion structure is the primary problem of transformation, focusing on fast, stable and high precision.

Curling competition on the ice surface flatness requirements are extremely high, per square meter in the case of bearing 150 kg of weight, the ice surface deformation can not exceed 1 mm, according to assistant ice maker Zhang Jinquan introduced: "We develop a customized detachable steel structure as the main structure under the ice, providing solid structural support for the curling track." ”

At the bottom of the track is the steel structure support system, followed by 10 cm light concrete prefabricated panels and two layers of insulation layers of 5 cm each, followed by PE moisture-proof isolation layer and non-woven fabric layer, on top of the 7 cm ice pipe and honeycomb bracket, is the real ice layer that athletes are exposed to.

As the foundation of the final ice surface, the height difference of the concrete plate within two meters cannot be greater than 3 mm, and the height difference of the whole site cannot be greater than 6 mm, which is the limit of the installation error of the assembly structure.

In the transformation, many of the original proud designs have become a problem to be solved at this moment. For example, the eye-catching "blue bubble exterior wall".

The blue membrane structure of the water cube is light and light-transmitting, but for the "squeamish" ice surface, the sunlight from morning to night is not friendly. According to Senior Technical Manager Shi Yuqiao, they covered a layer of PVC film under the membrane structure, and the water cube "closed the curtains" to avoid the impact of sunlight on ice. Wait until the Water Cube switches to "Summer Mode", and this dark film can also be removed.

Curling is known as the "roaring sport", curlers do not have amplification equipment, all rely on shouting, the sound environment of the venue is very demanding, for this reason, the team has conducted 5 simulated noise experiments to achieve 1.8 seconds reverberation effect.

Scientific and technological experts work together to break the "ice"

In 2019, the Ministry of Science and Technology, together with Beijing Municipality, Hebei Province and the Beijing Winter Olympic Organizing Committee, together with the Ministry of Education, the Ministry of Industry and Information Technology, the State General Administration of Sport and other departments, established the "Science and Technology Winter Olympics" leading group to coordinate the design of key tasks for the Winter Olympics in science and technology and provide scientific and technological support for the Beijing Winter Olympics and the Winter Paralympic Games.

Tsinghua University, Harbin Institute of Technology, Tongji University, China Construction First Bureau, SenseTime, etc., as well as the northeast agricultural university that volunteered to join, gathered together, under the deployment of the Ministry of Science and Technology, committed to seeking breakthroughs in the research of the internal performance and external effects of ice.

Among them, some of them study polar glaciers themselves, some study the impact of marine ice on drilling platforms, some specialize in thermo-mechanical, and study low-temperature air conditioning, all of which belong to the "edge ball" of sports ice research.

To some extent, they are "opening up the way" for domestic sports ice research.

In Yang Qiyong's view, although this is due to the needs of venue construction, it extends a more distant value.

As an imported product, curling was originally introduced under the Olympic strategy of winning glory, because it is more suitable for Asians to participate, in order to expand the gold medal of China's ice and snow projects. For more than a decade, there have been many climaxes and more flat valleys. Since there has been no systematic study of ice in China, no one has provided athletes with the basic and necessary ice surface information. In the world's top competitions, subtle changes in the ice surface will affect tactical choices at key moments, while Chinese athletes are weak in "reading ice".

In contrast, the old strong team has accumulated a lot of historical experience and can make better judgments by reading the ice surface. Domestic athletes are out of reach due to the lack of research information.

Through the pioneering of ice research, on the one hand, to solve the problem of uneven standards and imperfect ice surface, on the other hand, data and experience can also be accumulated. "If an athlete can know what might have changed on the ice when a match hits the fifth inning, he can definitely choose a better strategy and tactic in the huge computing system in his head." Yang Qiyong said, "We put a lot of effort into doing research, turned around and gave them the data, and became the 'helper' of the competition." ”

In addition, high-level ice makers, a rare profession in China, can also grow up in this process, providing a "work model" for China's future ice making work.

Use the "wisdom brain" to direct the transformation

At the end of 2019, Water Cube successfully completed the "water ice conversion" for the first time, which took nearly 60 days. In December 2020, the structure of the second "water ice conversion" was successfully completed, and it took only ten days to achieve the set goal of the key special project of the "Science and Technology Winter Olympics".

Behind the greatly accelerated "water to ice" is the blessing of intelligent transformation.

It is understood that the second conversion built a conversion structure composed of 2600 thin-walled H-shaped steel and 1570 lightweight concrete precast panels, each (block) steel beam and concrete precast panel has its own "digital identity", in the conversion construction, each component can be accurately and efficiently reset. During the construction process, the combination of motion capture technology and construction measurement technology greatly improves the installation accuracy.

"Curling tracks place extremely high demands on flatness. Last year, when the concrete slab was adjusted, for every 1 board leveled by the workers, 8 surrounding slabs were involved, and the measurement was very time-consuming. It is now equipped with 10 high-precision sensors to reflect the change in height in real time, and level it in place at one time. Yang Qiyong said that this technology will be more mature, and "water ice conversion" can also improve efficiency.

Traditional venues become "smart"

The change is not only happening in the pool, the water cube has turned into an ice cube, and the traditional venue has also been transformed into a truly intelligent venue.

Yang Qiyong said that the "water ice conversion" requires that the backstage machinery and equipment and control system of the venue have the ability to convert with the functional needs of the venue, and commercial activities must be undertaken during the period. This brings great challenges to the level of intelligent equipment and even property management of the venue.

In order to ensure that the indoor environmental conditions of the "Ice Cube" meet the requirements of the curling competition, the venue has set up a building equipment management system led by more than 4,000 sensors, which can monitor and control changes in temperature, humidity, PM2.5 concentration and so on in the venue. Under the precise control of this system, the ice surface temperature of the curling track reaches the requirement of minus 8.5 degrees Celsius, the temperature at a height of 1.5 meters on the ice surface is always maintained at 10 degrees Celsius, and the temperature of the spectator area in the stands is constant at 16 to 18 degrees Celsius, which truly achieves "different days in the same room".

Under the audience stage surrounding the ice rink, a long blue strip "cloth bag" with a diameter of 1 meter can be seen. This "duct" is a dehumidification air supply system, and the low-temperature and low-humidity air processed by the dehumidification system passes through it and is evenly blown over the site.

Underground of the venue, there is a 60-square-meter control room, and the large screen on the wall is the Water Cube intelligent building operation and maintenance management platform, which displays the operation of the ice system, dehumidification system, energy system, ticketing system, etc. in real time, and implements intelligent regulation of the equipment system of the venue. Visual energy control also effectively controls the energy consumption and carbon emissions of the venue.

Shi Yuqiao said that when it comes to the Winter Olympics, spectators can also enter and exit the venue through face recognition and smoothly pass through the four newly installed intelligent navigation screens.

"We're not gambling"

Think back to the "whimsical" plan, the difficult test, to the success of the first test "the strategy was basically recognized", and then to the winter Olympic standard "athletes did not complain". "We're not gambling." Along the way, Yang Qiyong said, "'Water ice conversion' from imagination to reality, inseparable from the support of China's scientific and technological forces." Looking at it now, we have not only completed the tasks that were 'impossible' in the past, but will be more exciting in the future. ”

On November 27, 2020, the renovation project of the Water Cube Curling Stadium successfully passed the completion acceptance. The curling venue that completed the second "water ice conversion" is being opened to the public, while the operation of the ice surface and electromechanical systems of the venue continues to be tested and debugged.

In Zheng Fang's view, if in 2008 we showed the achievements of scientific and technological innovation through "designing venues", then in 2022, we will use "transformation of venues" to continue this Chinese story of scientific and technological innovation.

He also remembers that in September 2018, Samaranch Jr., vice president of the International Olympic Committee and chairman of the Coordination Committee of the Beijing Winter Olympic Games, came to the Water Cube, and they demonstrated the transformation process of the Water Cube into the "Ice Cube" in the form of animation, and Samaranch Jr. was very happy after watching it, saying that "Beijing is hosting the Olympic Games in a smart way".

Today, they have delivered on their promises.

In February 2022, up to 4,600 spectators will sit in the "Ice Cube", in the graceful curves of curling, continuing the glory of the Water Cube in the middle of summer 2008.

Source: Science and Technology Daily