Wave of the Future
Learning Objectives - After this course, you should be able to:
- Discuss some of the legacy goals for the London 2012 Summer Olympics.
- Describe the structural systems deployed in several of the venues built for the London 2012 Games.
- Explain how these venues have been designed to ease post-Games adaptation or disassembly and the recycling or reuse of their constituent parts.
- Discuss the measures taken to make the structures as efficient as possible.
From the moment London won the bid in July 2005 to host this summer's Olympic Games, the organizers' chief goal was to use the massive athletic and media event as a catalyst for economic and social change in East London—a gritty and long-overlooked section of the city. For planners, the Olympics was an opportunity to remake a zone full of contaminated industrial sites, transforming it with amenities such as parkland, affordable housing, and improved public transport.
As part of this strategy, the London Organising Committee of the Olympics and Paralympic Games (LOCOG) mandated that the only permanent sports facilities that would be built were those for which there was a demonstrated long-term need. These would be designed so that they could easily shift from Olympics mode to community use. Other competition venues would be adaptable, or temporary in nature, with elements that are quickly demounted and the land freed for other uses. “At the end of the Games, we have to rapidly unpack the site and turn it into a real piece of the city,” says Jason Prior, chief executive of planning, design, and development for AECOM, the Olympic precinct's master planner.
One of the venues conceived to be unpacked or, more accurately, scaled back, is the main Olympic Stadium, designed by Populous. The building has been devised to shrink, through partial deconstruction, from an Olympic venue for 80,000 spectators to a post-Games stadium with less than one-third of that capacity. To facilitate this transformation, Populous developed a scheme that includes a partially below-grade, 25,000-seat stadium bowl intended to be permanent, and a 55,000-seat upper bowl designed with ease of dismantling in mind: It has a bolted-together wide-flange steel structure supporting precast concrete terrace units.
The project team, which included engineering firm Buro Happold, considered a stadium without a roof. However, computational fluid dynamics (CFD) analysis indicated a roof was needed to shield the field from wind. So designers developed a polyvinyl chloride (PVC) awning that extends over three-quarters of the stadium's seats. It has a bicycle-wheel-like structure made of bolted tubular-steel members, many of which were salvaged from a gas-pipeline project. The system, which is structurally independent of the seating bowls, comprises a perimeter-compression truss linked by cables to a tension ring at the roof's inside rim. Backward-leaning diagonal columns transfer the resulting forces to footings.
The strategy results in a structure requiring only about 11,000 tons of structural steel, making it the lightest Olympic Stadium to date, according to the Olympic Delivery Authority (ODA), the agency in charge of construction for the Games. By comparison, Herzog & de Meuron's “Bird's Nest” stadium, built for the 2008 Beijing Olympics, used almost 42,000 tons.
A decision to pull the concessions out from their usual location under the seating bowls contributes to the leanness. By housing vendors within temporary pods at the stadium's periphery, designers were able to reduce requirements for mechanical ventilation and for fire-suppression equipment.
This structural and planning efficiency translates into a stadium with a low embodied energy (the energy consumed by the processes associated with producing a building, including material extraction, product manufacturing, and construction, but excluding operations). According to some estimates, a stadium's embodied energy represents more than 60 percent of its lifetime energy load—a much higher proportion than for other building types. Because of its infrequent use, “the energy that goes into running a stadium is relatively small,” says Rod Sheard, Populous senior principal.
Part of the elegance of Populous's solution is that it allows removal of the roof without disturbing the seating bowls. It also permits the dismantling of the upper stands while leaving the lower ones in place. However, the current plans of the London Legacy Development Corporation (LLDC), the entity overseeing post-Games development, involve keeping both upper and lower bowls and the roof intact, while reducing the number of seats to about 60,000. The LLDC is now evaluating proposals from bidders who would operate the building as a multipurpose venue. The stadium is already committed as the setting for the 2017 World Athletic Championships.