London 2012 - Olympic Stadium
Ready, set, go: it’s London’s third time hosting the modern Olympics. The Olympic Stadium is naturally one of the essential stages for demonstrating Olympic excellence. Indications that the structure might be record-breaking were evident early on. What could be the most environmentally friendly modern Olympic Stadium ever is also the lightest, incorporating a total of 10,000 tonnes of steel. It was completed one year early within a construction period of only 1,000 days, and to top it all, under budget. No wonder that the project won prizes before the Games even began, despite criticism that optimization was restricted to functional aspects only.
Location: Olympic Park, Stratford, GB–E15 2HJ London
The Olympic Stadium is located on a 40-hectare, diamond-shaped island in the southern end of the Olympic Park. A far-sighted specification written in the early 1960s determined the development of the park right from the start, securing it as a "playground for Londoners against the background of London. This background – power stations, gas works, factories, railways, houses and flats – must be accepted and acknowledged in the landscape theme." Sporting venues were consequently designed as pavilions in the landscape – including the Olympic Stadium, which is surrounded by water on three sides and accessible via five bridges. The new stadium was designed by Populous, specialists in the design of sports venues, and Sir Peter Cook, former member of Archigram, acted as consultant to Populous.
As one would expect nowadays, sustainability also played a major role in the design of the Olympia Stadium. The weight of the structure was minimized by a reduction in the amount of steel and concrete used, which in turn led to a decrease in the associated grey energy. Large quantities of scrap metal were moreover used in the roof of the stadium – including 2,500 tonnes of steel tubing made using old gas pipelines and Metropolitan Police guns. Thanks to this pragmatism often maligned by critics, only one quarter of the steel required in the construction of Beijing's ‘Bird's Nest’ was used in London.
An intelligent concept was also developed for the period after Olympia: the original plan called for the stadium to be converted to an athletics stadium after the Games, which is why all the construction elements of the temporary upper steel structure were designed to allow partial disassembly. The idea was to turn the 80,000-seat stadium into an open arena with 25,000 seats in this way. In the meantime, economic issues have conflicted with the initial concept and two football clubs have expressed interest. A new round of bids after the Games is intended to decide on the future of the Olympic Stadium. The variability and adaptability explicitly realised in the building may in fact not even have to be made use of in the end.
To allow a post-Olympics conversion, the structure is composed of two parts: an elliptical sunken concrete bowl built into the ground accommodating the lower seating rows, and an independent structure comprising the upper tiers and roof, which was planned as a temporary construction. V-shaped steel supports act as bracing as well as carrying the steel truss structure that forms a compression ring. A delicate cable construction holds the lightweight roof membrane sections. Special features to allow simple demountability of the superstructure are also found in appropriately designed details, such as bolted rather than welded steel connections.
The Olympic Stadium is traditionally the venue for athletics competitions as well as the opening and closing ceremonies. Wind conditions in athletic sports stadia are important, not least because records achieved by athletes may be considered as invalid if the measured wind speed is found to exceed two metres per second in specific areas of the competition grounds. In order to minimize this risk, various roof geometries were examined by Populous in an earlier planning phase. Computer-aided flow simulation models showed that about two-thirds of the spectator seating has to be covered to ensure optimal wind flow conditions.
The stadium roof is composed of 112 membrane sections covering a total area of 24,500 m². Individual elements are made of a PVC-coated polyester fabric, with a thickness of approximately one millimetre and an area of up to 210 m². Detailed cutting plans allowed crease-free installation of the elements, exact positioning of openings for water pipes and service access points, as well as placement of electric cables for the lighting towers.
Lighting technology has to meet demanding requirements for TV transmission of athletics competitions. A total of 532 lights are organised into 14 towers to protect spectators and athletes from glare effects. These are situated 63 m above the field of play on the structural nodes of the inner tension ring. The lighting towers weighing 35 tonnes each are held in position by means of cables from the truss behind.
Critical voices have recently focussed on the decorative strips of material draping the stadium, which are intended to act as markers and direction signs for visitors. These retrospectively fitted panels are 2.5 metres wide and 25 metres high. The 'wraps' were manufactured by Dow Chemicals, a company that is also accused of environmentally irresponsible behaviour. Even the bright colours designed for the wraps by the artist Sophie Smallhorn cannot really detract from this controversy, especially in view of the fact that the 336 banners will be removed again after the Games – there goes the radical functional approach, with a good ecological balance thrown in for good measure.
The future use of the stadium is likely to be much debated even after the Olympic Games are over. A decision may be expected in October 2012 at the earliest. Whether an athletics world championship will take place here in five years, as initially planned, also depends on the flexibility of the future tenant.
Client: ODA, Olympic Delivery Authority
Structural and services engineers: Buro Happold
Main contractors: Sir Robert Mc Alpine
Construction period: May 2008 - March 2011
Opening: 5 May 2012
Cost: £ 498 million
Seats: 25,000 permanent and 55,000 temporary places
Dimensions: 310 x 260 m
Stadium height: 62.7 m
Pre-cast units in stadium bowl: 8,000
Reinforced pre-cast concrete within stadium bowl: 9,250 m³
Roof area: 24,500 m²
Length of cable in roof: 6,000 m
Weight of steel construction: 10,000 t
Stadium entrances: 56
Rooms and spaces in stadium: 700
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