Olympic showpiece

In July 2001, Beijing won the competition to host the 2008 Olympic Games, beating off rival bids from Istanbul, Turkey, Osaka, Japan Paris, France and Toronto, Canada. It was a defining moment in China's emergence onto the world stage, and the country's status was further cemented in December of that year with its entry to the World Trade Organisation (WTO).

Only the soccer World Cup can rival the Olympics for the level of global interest they generate, attracting billions of TV viewers. Host nations therefore go to extraordinary lengths to present themselves in a good light, investing huge sums of money in new venues and infrastructure. In Beijing's case, a reported RMB 17.4 billion (US$ 2.15 billion) will be invested in venues for the 2008 Games, the centrepiece of which will be a new athletics stadium in the city's Northern suburbs.

The client body for the project is a specially incorporated entity called the National Stadium Company. Majority ownership (58%)lies with Beijing's Municipal Government, with the remaining equity being taken-up by a commercial consortium called China International Trust & Investment Corp (CITIC). This National Stadium Company will build and operate the venue on a 30 year franchise, after which ownership will revert to the city of Beijing.

CITIC comprises the contracting joint venture that is building the stadium and, rather confusingly, the US arm of a Beijing-based investment company, Golden State Holding Group (GSH). The general contracting group comprises three entities - Departments no. 1 and no. 4 of the Beijing Urban Construction Group (BUCG) and Zhongxing Guohua Construction Company.

Design

The competition to design the venue was won by Swiss architectural practice Herzog and de Meuron, working in partnership with the China Architecture & Design Research Group (CADREG), and engineering consultant Arup. A distinctive design, the stadium's façade comprises an apparently random network of criss-crossing columns and beams, reminiscent of a bird's nest.

Measuring 333 m long and 280 m wide, the stadium will have a gently undulating roof with a maximum height of 69.12 m. The original design included a retractable roof that would have completely enclosed the stadium, allowing games to continue in bad weather. However, a cost review in July 2004 resulted in this element being removed from the plans, which helped cut the budget from RMB 3.4 billion (US$ 420 million) to RMB 3.1 billion (US$ 383 million). The redesign also saw the seating capacity of the stadium reduced from 100000 to 80000.

Inside the stadium, the 80000 seats will be spread over three tiers, with the various spectator areas and facilities required to run the venue located underneath these. This entire internal structure is being built from cast in-situ concrete, starting with three levels of underground car parks.

Above ground there are seven floors under the tiered seating. The ground floor will largely be used to house plant and equipment to run the stadium, although there will also be a walkway around the venue's circumference at this level, between the concrete structure and the façade. The fourth floor will contain the VIP areas, while the third level will be filled with catering outlets.

Progress

When iC visited the site in late October, the final pours were being carried out on the concrete seating banks, which will have a maximum height of 51.1 m. According to a spokesman for BUCG, it was critical to get this milestone complete by the end of the month because the temperature in Beijing changes rapidly at that time of year. Late October is pleasantly warm, with mid-day high temperatures around the low 20 °C mark, but these fall to sub-zero levels in just a few weeks, with snow often making an appearance by mid-November.

The main tools for this stage of construction have been 14 tower cranes, dotted around the inside and outside of the stadium. The main suppliers for these are Chinese manufacturers Shenyang and SCM - the latter company is thought to be market leader in the Chinese tower crane sector. In addition, there was one Potain MC300, built at the parent company, Manitowoc's factory in Zhangjiagang, Jiangsu Province, China. Concrete was being poured with a combination of Schwing and Sany pumps and Schwing placing booms. In addition to this equipment, there were an estimated 5000 workers on site.

Completion is due at the end of 2007, and the emphasis over the next two years will be on building the 'bird's nest' structure. Unlike many stadiums, the outer skin will be a genuine façade, with no structural connections between it and the inner concrete bowl containing the seats.

The façade's main structural elements are 24 reinforced concrete columns spaced at regular intervals around the stadium's exterior. Aside from these, which will blend into the design, there are no other towers or cable supports to interrupt the stadium's lines.

The bird's nest effect will be created with the use of 36 km of steel elements, weighing a total of 45000 tonnes. Weather-proofing will be provided by a skin of Ethylene Tetrafluoroethylene (ETFE) - the same material used by Herzog & de Meuron for the outer shell of the 66000-seater Allianz Arena in Munich, Germany.

The inner skin of the façade will be a polytetraflouroehylene (PTFE) - or 'Teflon' - membrane, and the space between these two surfaces - 12 m in the ceiling sections of the stadium will be filled with inflated ETFE cushions. From a practical point of view, these will help keep sound inside the arena and enhance the atmosphere for spectators and competitors. In design terms, they will continue the bird's nest theme, mimicking the way birds stuff their twig nests with soft material for comfort and insulation.

In addition to the stadium itself the site, with an area of nearly 26 hectares, will be home to the Olympic aquatics centre as well as a secondary arena that will be used by athletes to warm-up prior to competing.

According to BUGC's spokesman, the project is running on schedule, and will be finished a good eight months before the opening ceremony on 8 August 2008.