Brendan McGetrick
Recent works and current obsessions

Tan Xiaochun, Builder

For the tenth installment in the 2009 Domus interview series, Li Hua and I met with Tan Xiaochun, Chief Party Secretary of Beijing Urban Construction Group and chief of construction for the National Stadium. Over a career spanning decades, Tan has overseen some of China’s most ambitious and perilous urban projects, including the construction of the Line 1, Beijing’s oldest, longest, and busiest subway line. We talked about the many challenges of constructing the Stadium, the extraordinary transnational collaboration it required, and the need for architects and contractors to improve each other.

In this interview series, we ‘re talking to people who work with architects to try to understand their experience and get a better sense of of how architectural collaboration works. You’ve served as head contractor for several highly complex construction projects here in China, so I’m very curious to hear about your experience.

As you know, I’m the chief of construction for the National Stadium or “Bird’s Nest”, so I’ll start by talking about the construction phase of that project.

We began in 2003, when it was still a village here. On the 24th of December 2003, after the removal of all previously existing structures, the Bird’s Nest and the National Aquatics Center, or “Water Cube”, had their ground-breaking, marking the starting point of construction for the Olympics. Jia Qinlin, a member of the Standing Committee of the Political Bureau of the CPC Central Committee, attended the ground-breaking ceremony. China chose the Bird’s Nest as the main stadium because of its impressive appearance and, as the name suggests, it agrees with our traditional philosophy that man should return to nature.

My first challenge in constructing the Bird’s Nest was its heavy duty steel structure, which is unlike the light steel structure of National Grand Theater. We wanted to localize the fabrication of the tens of thousands of tons of steel required, but were we capable? Do you see the 110 millimeter-thick plate steel used for the main columns out there? It’s Q460 high-tensile steel.Very few countries could make it, and China did not have the technique at that time. So first [we had to learn how to produce] the material, then how to bend and twist it like a Tianjin fried dough twist.

Second, in the process of production and butt connection of the steel structures, we had to face the problem of final gap closing and unloading. The whole structure was divided into six parts, with gaps in between, and we could only get them fully welded and make the separated pieces become one when it came to the final gap-closing. After that, we had to unload the Bird’s Nest from its previous support system of 78 pillars, let it stand on its own and deform evenly. These techniques posed problems that would be difficult to solve anywhere in the world.

Based on these challenges, how the was construction process organized?

The Bird’s Nest took five years to build, and the construction phase could be divided into the following stages. The first stage was to make a concrete, bowl-like grandstand of 91,000 seats. We started from pilings, and then built a bearing platform, on which we eventually built the stands. It took us eight months altogether, and was finished on November 10th 2005, before the Beijing winter.

At the same time, we had stage two – manufacturing steel structures. We chose to do it in Yangzi River Delta region, the biggest steel structure production base in China, where there are many large factories serving the ship-building industry and the iron and steel industry. After the 44,000 tons of steel structures were made there, they would then have to travel over 1300 kilometers, crossing five provinces and three municipalities, to get to the Bird’s Nest to be assembled and installed. Don’t you think it was a miracle? The distance was similar to crossing several European countries.

The difficulty of manufacturing was in the so-called bend-torsion components. We developed a new machine called “Dieless Multipoint Forming Bend Torsion Component Builder”. With this, the steel plates would come out as we designed. This was something remarkable, since the plate bending rolls previously could only make circular shapes, but this one could accommodate bend and torsion.

After manufacturing, we had to pre-assemble the structures in the factories to see if they are OK. Our engineers would check the quality, fabrication precision, etc., and confirm everything on the site of the pre-assembly. Then we would take the structures apart for transportation, and install them here. Otherwise, if there was a mistake, we would not be able to correct anything in Beijing.

Stage three – butt connection and installation. It was technically difficult to butt connect components in mid-air. In some places we had fourteen components converging on the same point, and the deviation could not be more than three millimeters in any direction. There were three factors that might result in error: temperature, production process, and measuring devices. Even so we still succeeded in controlling the errors, which showed that in China we had a high level in production precision.

It sounds like a combination of huge scale and incredible detail…

The Bird’s Nest used more than 910 welders; the weld was about 300 kilometers in total, almost equal to traveling roundtrip between Beijing and Tianjin. The welding material weighed more than 2000 tons, unique in the world. The welders came across the nation from ship-building or other industries, and had to pass an exam to work here. The welding records were saved in our computers, including the time, the name of the welder and the inspector, so that every weld was taken responsibility for, and the whole quality was ensured.

I kept asking Herzog & de Meuron why they didn’t use this approach in their own country, and their answer was that labor was too expensive in western countries – in China, a welder’s monthly salary is only about 4000 RMB and, what’s more, how could they find so many welders there? I asked the same question to some British architects, and they said their Parliament wouldn’t allow such big budget if something like the Bird’s Nest were proposed for their 2012 Olympic Games. In all, China was the only one to make the Bird’s Nest: on one hand, our national power and production standard had improved a lot with [our economy’s] reform and opening-up; on the other, due to our cheap labor, this project could work economically. Imagine, there were more than 7000 workers on site when building the grandstand, more than 3000 when doing the steel structures; and we summoned many excellent domestic enterprises to collaborate on this project.

That covers phases one through three.

Stage four was the final gap-closing, in which temperature was the key factor. Before that, the Bird ‘s Nest was “breathing” all the time: heated in the day, it began expanding; cooled at night, it contracted. We used all of Beijing’s meteorological data to figure out the ideal temperature for the final gap-closing: 19° (±4° Celcius). In July 2006, all the welds had been completed except for the six closure lines, and we began to wait for that temperature. You can’t imagine how anxious we were, since every day counts on a construction site and it had been more than a month, but the temperature still didn’t come. Finally in August 23rd 2006, the weather forecast said it would drop to 22°℃ at night. We waited. At about 11 or 12, it was 23 degrees℃, and then at one in the morning, it finally reached 22℃°! We summoned about 200 welders who worked continuously for more than ten hours and completed two closure lines. On the 29th and 30th, the temperature reached the necessary point again. We did the final gap-closing in these three days, and the Bird’s Nest became one unity.

Then it came to stage five: unloading. The Bird’s Nest had to learn to stand with her own 24 columns and the stress from her own heavy duty steel truss, after the removal of the previous support system of 78 pillars. Whether the resulting deformation would exceed the acceptable value was key to evaluating the design of the Bird’s Nest. Our engineers gave a theoretical value of 286 millimeters, but such deformation had no reference in the world. After drilling on September 12th, we worked day and night for five days, going through seven major steps which were comprised of thirty-five minor steps, and had the Bird’s Nest unloaded. The unloading process was broadcast live by four major Chinese TV networks: CCTV, Phoenix, BTV, and Dragon TV. The final deformation value, detected by two companies, was between 217 millimeters and 276 millimeters, lower than the theoretical one. With the success of unloading, there would not be anymore subversive problems to Bird’s Nest’s steel structure; in other words, the final success was almost a sure thing. People cheered and tears ran down my face: what a reward for years of hard work! This great breakthrough proved that we China are surely first-class in every aspect in steel structure production.

After the unloading on September 17th, I asked Herzog & de Meuron how they felt about it. They checked it all over and said it was “impeccable”; with planned organization, we Chinese realized a miracle of steel structure, a dream that couldn’t come true in their own country. That National Day, our General Secretary, Hu Jintao, came here, listened to my one-hour report, and highly valued my work. The President of the International Olympic Committee, Dr. Jacques Rogge, and UN Secretary-General, Ban Ki-moon, agreed that the Bird’s Nest was a great achievement in architecture and structure. The construction that I led won world recognition.

That’s a truly heroic story. Could you explain some more about the innovations required to construct the Bird’s Nest?

Fifty-one innovations were developed for the Bird’s Nest. For instance, testing the standards of construction quality: the Bird’s Nest was a unique structure, and there weren’t any relating national standards then, so we set new standards during construction. The production of the steel structure needed innovation, too. Though China had the world’s biggest steel and iron industry, we weren’t capable of producing 110mm-thick steel plates, which had to be imported from Luxemburg and Japan. But we aspiring Chinese wanted to make it on our own. Wuyang Steel experimented for three months: furnace by furnace, they smelt, ground, and rolled. As soon as the steel came out, it got transported to Harbin, to test its physical properties and welding performance under -15°℃ conditions. By the seventh furnace, they succeed in producing Q460E, which was used for the columns, and we no longer needed to import. Experience was also accumulated here for the devastating Z-shaped, highly-stressed structure of the CCTV headquarters.

The Bird’s Nest’s entire structure has a span of 333 meters, a height of 69.4 meters at the highest point, with 258,000 m2 of floor area. The biggest rod section is 1.2m x 1.2m, although they seem quite thin in photos. After completing the steel structure, we went on to machinery installations, decorations and membrane structures. The construction of the Bird’s Nest was open, just like China: the membrane went to Covertex, from Germany; intelligent control went to Honeywell, from the USA; cranes were from Mammoet, from the Netherlands, for we had a lot to hoist – up to 360 tons. We also invited Bouygues, from France, as our technical supervisor. Under my command, our Chinese staff learned from all the collaborators to make things better. You see my white hairs here? That’s the duty of five years.

So how did you organize so many workers, and provide so much training on new building methods?

I had quite some experience in organizing big projects. I was vice-commander of Beijing subway Line 1 from Fuxingmen to Batong, one of the main leaders in the construction of the China Millenium Monument, and commander of the temporary hospital in Xiaotangshan during SARS.

In terms of this particular project, I am thankful for help from all over China: when we said we needed help for building the Bird’s Nest, all the domestic companies were so supportive, for it was a one-hundred-year-old dream of us Chinese! We had eight major domestic factories to produce only the steel structures: Anshan, Baoshan, Wuyang, Beijing… During transportation, all provinces along the route opened their highways at night especially for our trucks.

Which I think supports the idea that you mentioned earlier that it required the special qualities of China at the moment to realize a project like this. I couldn’t happen elsewhere. I’m still very curious about how you provide oversight in a project like this. I realize that you have a background in doing complex projects like the construction of a subway line or projects with extreme time pressures like the construction of a SARS hospital, but an effort like the Bird’s Nest, where there are so many vulnerabilities and no real precedent seems that much more difficult. How do you maintain control and maintain confidence in a situation like that?

I depended on “technique solution package programs”. We collected programs from eight countries including Australia, Singapore, and Japan. In all, there were three kinds of methods: piece-by-piece connection, which we used, to butt connect pieces in the air; sliding, where you fabricate the structures aside first and then slide them to the right place to put them together; and integral jacking, where you lift the whole structure after integral fabrication. According to my experience and China’s reality, I chose piece-by-piece connection for its precision in fabrication. Steel structure wasn’t my major in college; I studied railway construction such as tunnels and bridges. It was so lucky that we had a terrific team, including more than 100 Chinese engineers and some state-sponsored research teams that provided expert support in every particular aspect. To summarize, the key of organizing the construction was program demonstration: only with a detailed program could we make it.

Everyone held different responsibilities when carrying out the program: one of my assistants took care of steel structures, the other the butt connection, and another the supervision in factories… We had good division of labor, so it was easy to monitor. With model simulation, our tens of thousands of components were sequenced according to the timeline of fabrication, hoisting and butt connection, and the types of workers in every step. We worked according to this schedule, so everyone knew when to do what. At the construction headquarters office, we made a big model which was colored with red, green, blue, and black, and marked with numbers to represent the sequence of construction. We also had a huge construction schedule there on the wall, so everyone knew their responsibility and timelines.

I also think it’s interesting that you mention this project raised the level of production and construction quality in China. Techniques from around the world were learned in order to make the stadium and in the process China became world class. Now that this has been achieved, has your company been approached to do construction outside of China?

Now there are a lot of tourists here every day, up to 80,000 people a day, but there have been very few academic exchanges. The Bird’s Nest does have high touristic value, but, for its structural challenges, it should have high academic value as well.

Time magazine and Business Week acknowledged it among the greatest contemporary architecture, and the British Museum has included it in their exhibitions. 45 of our 51 technical innovations were the first in the world: beside bend torsion of high tensile steel and membrane structures, we also pioneered a concrete jacking technique, which was, when building the grandstand, to jack the concrete to 60 meters or 70 meters high and let it form naturally.

Steel structures are preferred in construction now, especially in big public projects and high-rises. So the Bird’s Nest will be an important reference for heavy duty steel structure construction in the world of the future, including the construction of the new CCTV headquarters. If you are asking whether I’m able to lead another construction of a big sports facility abroad, I would say, “No problem!”

I want to ask a general question: architects often say that contractors affect the design, because they influence many things like material choice, construction techniques, etc. I’m curious: how do you view the relationship between contracting and architectural design?

In terms of material and technique, architects always think of the best effects, but in the real market, such things sometimes don’t even exist, so we must ask them to modify the design. For example, the red walls of the Bird’s Nest were designed to use glossy paint, which would reflect too much light and be really offending to the eye. Then we suggested flat paint, and built a sample room to let the architects see the real effect. We also proposed to put more lights, since there weren’t enough in the original design. Our experience and the architects’ concepts should collaborate, so we have to communicate in order to make things better for the client.

Sometimes architects are just experimenting with new materials and techniques and, in this case, we have to build a sample room before further construction to see if some technical data should be modified. Data from the books sometimes doesn’t work on site, then we have to negotiate with architects and tell them what are the best possible solutions in China.
We once corrected a mistake in the Bird’s Nest’s design. As you know, the Bird’s Nest is an open building and wind can blow in. But in the original design, the walls of the first and second floor were interior walls, and the strength of the keels and surface board would not be able to resist the wind. So I pointed that out. But, on the other hand, architects help us a lot with introducing the most advanced materials and techniques. So we make up for each other.

One last question: now that the stadium is completed and the Olympics are over, why are you still working here in this office at the bottom of the Bird’s Nest?

Well, first, our company is one of the stakeholders here, with an investment of more than 400 million RMB. Second, the Bird’s Nest should have some functions after the Olympics, like tourism, conferences, shopping, performances, and dining, so some small modifications are needed for future use. I’m the man who knows how the stadium was made, so naturally it would be my job again. The modifications need to be discussed with architects. For example, the black stone used in the original design does not suit the Chinese preference for bright colors, so we changed it in some rooms. And we felt the lights weren’t enough, so we added more.

Are Herzog & de Meuron involved in that?

Their Chinese colleagues [China Architectural Design & Research Group] would be enough, for the modifications won’t affect the exterior appearance. Think about it: at least 20,000 people come here every day… Where can they eat? How do they amuse their kids? We must provide services for them. You can see now that we are preparing facilities for an F1 race here. I think the Bird’s Nest is one of the best examples of post-Olympic economic returns. It’s absolutely a new tourist spot, standing at the Fourth Ring [Road], with all the Chinese population, let alone the world population, as potential visitors. We’ve received more than 300 million RMB solely from the ticket sales over 10 million visitors. Its benefits are emerging.

Originally published in Domus China 40 (November 2009); republished in Who is Architecture? (Timezone 8, 2010)