Wave of the Future

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.

Aquatics Centre
Zaha Hadid Architects

Although the stadium now seems destined to be a long-term fixture in the Olympic Park, it was intended to be largely temporary. In contrast, the Aquatics Centre, designed by Zaha Hadid Architects (ZHA), from the outset was envisaged as a permanent icon—albeit one that would shed 85 percent of its 17,500 spectator seats after the Games. Within a concrete podium, and underneath a swooping roof inspired by the fluidity of water, the building houses two pools—one for swimming and one for diving competitions. A third pool, for athletes' warm-ups, is tucked below a bridge that will serve as the primary access to the center post-Olympics.

The facility has been criticized for the two winglike appendages that enclose 15,000 Olympics-mode seats. Their blocky shapes, at least from the exterior, obscure the Aquatics Centre's otherwise sinuous forms. But in order to convert the venue into a pool for community use, these wings will be “clipped” after the Games and replaced by glazed facades. As part of a PVC “take-back” policy established by the ODA, the wings' wrapping will be reclaimed by its supplier and either reused or recycled into a lesser grade of vinyl. The seats, which are leased, will be returned to the rental market. And the steel supporting the stands, made of bolted-together, standard wide-flange shapes, can be readily used in other construction projects.

Somewhat paradoxically, the sight-line requirements from the temporary stands determined the height and geometry of the 118,000-square-foot permanent roof. It sweeps in wavelike fashion from south to north over the column-free hall, dipping down between the diving pool and main pool, and tipping up at its east and west edges.

To support the doubly curved form, engineers from Arup devised a system of 10 fan trusses made up of mostly rectilinear members. The trusses span 390 feet between two transverse trusses—one bearing on a 90-foot-wide shear wall at the hall's south end, and another spanning two concrete cores 177 feet apart at the north. Purlins spanning the trusses' top and bottom chords provide attachment points for the aluminum cladding on the roof's upper surface and for red louro panels (solid in some locations and veneer-on-plywood in others) on the roof overhang and on the ceiling.

The complete truss assembly weighs about 3,500 tons. And even though a less sculptural shape might have resulted in a lighter roof, the roof members have been highly optimized for structural efficiency. According to the ODA, the realized roof scheme has a 95 percent utilization factor (a ratio of actual to permitted stress). “None of the sections is being lazy,” explains Glenn Moorley, ZHA project architect.

Basketball Arena
Wilkinson Eyre Architects

While the Aquatics Centre and Stadium were designed to be scaled down after the Games, officials took a much different approach for the Basketball Arena, developing a brief for a 12,000-seat temporary venue that could be completely disassembled with at least two-thirds of its components reused or recycled, or reerected elsewhere. In response, the design team, which included architect Wilkinson Eyre and structural engineer SKM, explored a number of schemes, such as a cable-net structure and a geodesic dome, evaluating these options on the basis of cost, ease of construction, and the ability to be disassembled and reused. They eventually settled on a steel-portal frame, but one with a shallow barrel roof, rather than the more typical pitched roof. The volume is covered with 215,000 square feet of PVC membrane, creating a building with a profile that Wilkinson Eyre associate director Sam Wright likens to a loaf of bread. “We didn't want to present a blunt, gabled end to the park,” he says.

The arena is far from plain white bread, however. It has plenty of surface articulation provided by sub-dividing its elevations into 19-foot-wide-by-80-foot-tall bays. These include a secondary frame of protruding radial steel arches arranged in three different combinations. The units are used both right side up and upside down, producing six modular variations and a seemingly random, undulating surface. These bays, which have fittings that allow the membrane to be “unzipped,” can be disassembled and then reerected or reconfigured, explains Jim Eyre, Wilkinson Eyre director.

The arena's remaining components have also been designed to facilitate their reuse, depending on many of the same strategies deployed in other venues. The structure supporting the seating, for example, is self standing and is bolted together rather than welded, as is the portal frame. And to keep the arena compact, the team relied on an approach similar to that used for the concessions at the main stadium: The arena's support services, including warm-up courts, areas for catering, and security, are housed in an adjacent modular building that Eyre refers to as a “bar of accommodation.”

One especially unusual aspect of the arena was the method used to procure it. The building was divided into six packages, each separately bid: the portal frame and the PVC envelope; the seating and the seating bowl; the interior fit-out; the mechanical and electrical work; and the foundations. The responsibility for reusing or recycling the elements within these packages lies with the contractors, making it hard to predict where the arena's individual pieces will eventually land. However, the textured shell and its portal frame could well be traveling to Brazil for the 2016 Games. According to LLDC, officials from Rio de Janeiro and the supplier of the membrane and its underlying structure have been discussing such a possibility.

If the Basketball Arena's envelope travels to Brazil, it will certainly help validate London's approach to planning the Games. But to more accurately gauge London's accomplishments, we will have to wait more than four years, watching all the while to see how well facilities like the pool, the stadium, and the park as a whole meet community needs, and if the hoped-for regeneration actually materializes. If the Olympic site transforms into “a real piece of the city,” as AECOM's Prior hopes, the 2012 Games will have been a true success.

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