黑洞社区

Designing for reuse

The arena was designed as a kit of parts that can be sold or put to use individually or as a whole. The ODA will rent the venue, after which Barr Construction, which owns its structure, will dismantle it so it can be used elsewhere. It鈥檚 the same story for the other elements. The temporary seating, for example, is supplied by Slick Seating and will go back to the hire market, as will the portable court and concessions kiosks.

However, designing a structure of this size to be demountable is quite a task, and a bespoke solution was required. Amjad Ali, the project manager with the ODA, says the authority first spent a long time talking to the events industry about the best way to approach the build. 鈥淚t needed to be something that could be easily taken down and transported,鈥� he says. And although this is a temporary structure, it still had to comply with the 黑洞社区 Regulations, although it was exempt from Part L. The answer that was settled on was to develop a slender steel portal-frame structure, clad in a removable PVC membrane.

Preparing the ground and erecting the frame

When the arena is packed up and taken away, there will be no trace that a 10-storey structure ever stood here. No holes in the ground, anyway. Before construction started, the site was prepared using a special vibrating roller that compacted the top 3m of soil to provide a stable base.

鈥淚f you were designing a venue like this conventionally you would submerge it into the ground,鈥� says Snoddy. 鈥淗owever, removing tonnes of soil and then reinstating it after the event didn鈥檛 make sense.鈥�

The building鈥檚 structural frame is mounted on a perimeter ring beam made of reinforced concrete. This has been designed to use minimal material and varies in depth from 600mm to 1m and is about 2m wide. The beam itself sits on 800 vibro stone columns, which have been created by boring a hole, pouring in stone and compacting it.

About 3,000 tonnes of recycled ballast were used to create the columns. 鈥淭he good thing with this method is we don鈥檛 have to remove them afterwards; we simply remove the ring beam and recycle that,鈥� says Ali.

The 1,000-tonne steel structure was brought to site in 86 trucks. Sixteen massive portal frames, each with a span of 96m, were placed 6m apart to create the basic form. At the highest point these rise to 35m but to soften the building鈥檚 bulk, a hipped roof has been used that gives a continuous eaves-level all the way around.

The arched trusses, fabricated by Watson Steel in Bolton, were delivered in four sections along with the columns. A carefully choreographed installation procedure using four cranes then came into play. First, the trusses were assembled on the ground and placed on temporary supports while the two columns were craned into position. These were pinned to preinstalled base plates before the truss was lifted and dropped into place. Each frame took around a week to prepare, with the lifting procedure taking the best part of a day. 鈥淲hen you see the first truss go up it brings it home to you how slender they are,鈥� says Alan Howatson of Barr Construction. At their deepest point the trusses measure just 3.2m.

With the first frame erected, those on either side were slotted in and work could begin to bolt in place the steelwork that connects them, helping to stabilise the structure.

Installing the facade

A building of this scale with no windows and clad in the same material all the way around is unlikely to stir the emotions. To inject some interest, architect Wilkinson Eyre came up with a simple arrangement of curving steel tubes that bow outwards between each column of the portal frame. These are differently arranged to provide a constantly varying surface.

Stretched across these tubes is a skin of PVC. The facade is made up of 6m-wide sections that were hauled up a track mounted to the column and stretched across the tubes to clip into another track on the column opposite. Unlike other materials, like ETFE, PVC doesn鈥檛 have a 鈥渕emory鈥�: it springs back to its original shape when it is taken down, making it easier to reuse.

It was a similar story for the roof panels, although here a continuous 6m-wide sheet of PVC was clipped into tracks and then run across the roof in a single operation. 鈥淭he first roof panel took six hours to install,鈥� says Ali. 鈥淲e got it down to two hours by the end鈥�.

Fitting it out

Now the venue is enclosed, work is beginning on the fit-out. A concrete slab will be laid to support the seating scaffold and steel supports for the stairs, lifts and toilet blocks.

Just before the test event, the London Organising Committee of the Olympic Games (Locog) will lay a portable court that will be removed after the test and reinstalled just before the Games. 鈥淥ne of the issues is that this is not a conditioned building and the floor would warp if it was left in,鈥� says Ali.

In the event that 2012 brings a hot summer, portable air handling units connected to external chillers are placed under the raked seats. These will blow out cooled air that warms, rises and vents through high-level louvres. 鈥淚t鈥檚 a simple solution and avoids lots of ductwork,鈥� says Ali. The units will be commissioned in March 2011.

Currently, lighting designer United Visual Artists is working up an external lighting scheme to add more drama to the elevations. According to Snoddy, the idea is that the skin will be backlit from the inside and also have light projected onto it. He鈥檚 coy about the design but says it will go to planning soon.

After the Games

The question of end-use and sellability after the Games has been important throughout the arena鈥檚 design and construction. The design team rejected the option of a bespoke seating system for the arena as it might be harder to put back out into the hire market. But the sheer scale of the structure means that there is only a small market of potential users. According to Barr鈥檚 Alan Howatson, it鈥檚 only now that the structure is going up that people will fully appreciate its size and potential uses.

There鈥檚 nothing to stop it becoming a permanent venue on a different site, and Howatson suggests it would be ideal for a soccer academy. But it鈥檚 been designed and built as a flexible space and may have future as a relocatable building in its current size, made smaller by omitting some of the bays, or split up into individual elements. Whatever happens to it, the ODA won鈥檛 have to worry.

Three other temporary venues to watch

Water polo This 5,000-seat covered arena is next to the aquatics centre; the warm-up pool alongside is being designed by David Morley Architects.

Aquatics training As part of the Eton Manor complex in the north of the park there will be three Olympic-size swimming pools, a synchronised swimming pool and a water polo pool together with a 10,500-seat venue for the wheelchair tennis competition. Careys is the lead contractor.

Hockey centre This venue will be erected next to the international broadcast centre for the hockey games and seven-a-side and five-a-side Paralympics football. It will have two separate pitches: the main competition pitch will have a capacity of 15,000 and the second pitch 5,000. After the Games it will move to the the Eton Manor group of facilities.

Basketball arena in numbers

• 12,000 capacity
• 35m-high building - as tall as Tate Modern
• 115m-long, 1,000-tonne steel frame
• Frame will be wrapped in 20,000m2 of fabric