From a distance, you might be forgiven for thinking that the 2012 handball arena looks dull. It certainly doesn’t have the curves of the Aquatics centre or the pomp of the main stadium. It is in essence, a box. However that is where its fundamental beauty lies.
What designer Make architects and consultant Arup have done is taken the space needed for the Games and built the structure around it, keeping the structure tight and efficient. Many ideas were explored but the fundamental idea of a box was returned to. "We won the job on the mandate: 'keep it simple'," says Arup associate director Andy Pye.
"We looked at a steel frame solution, portal frames, arches, masts – we looked at everything going. We worked up timber and steel solutions and looked at solutions not only from the economic but also the architectural point of view. Domes create a large internal volume and increase the roof area – they were going away from simplicity. We kept returning to the box."
However this is no cattle shed. It is a beautifully detailed project – the designers likened it to a jewellery box. The reinforced concrete base on a piled foundation is separated from the copper clad steel framed upper "floating" box by a band of glazing.
One of the challenges of the project was how to found the building on poor ground. "We are dealing with contaminated ground and difficult piling conditions," says Pye. "We have to pile down to the Thanet sands. Also there are two Channel Tunnel Rail Link tunnels within 10m of the building footprint which could affect our building. "We’re using continuous flight auger (CFA) piles as they disturb the contamination less and are better for the water course. We will be working at the limit at what CFA piling rigs can do. We will be drilling deep, 26m to 27m. For that we need a rig with high torque. By keeping the diameter down, we can reduce the torque on the rig."
Arup has managed to stick to its remit of keeping it simple by using one type of pile and altering the depth where needed. Also, it has tried to eliminate pile caps by allowing for just one pile per column. However, the final pile design will be by the to-be-appointed design and build contractor.
The first tier of seating is situated in the reinforced concrete base of the building. The seating is brightly coloured to give the arena a sense of "vibrancy" even when it is not being used, but what makes the seating special is that it is fully retractable. This maximises the playing area, when the demand for somewhere to play may be high, but the number of spectators less so. "The retractable seats are fundamental to the success in legacy," says Olympic Delivery Authority project sponsor Colin Naish. "The whole point is to maximise the field of play."
Reinforced concrete is used for the building up to concourse level. At this level, glazing gives views out across the Olympic Park and slender concrete "blade" columns are used to support an upper seating tier. The structure above is a steel frame with precast concrete members forming the seating and floor. The steel structure cantilevers out from the columns calling for a complicated moment connection. However by replicating the same connection a number of times, Arup was able to stick by its "keep it simple" principles.
Construction is expected to finish in 2011 in time for test events ahead of the Games.
The steel truss roof is the art of simplicity – standard purlin, with short spans.
"We are keeping the spans as short as possible to keep down the cost of the roof structure and the cost of the building," says Arup associate director Andy Pye. "We are dealing with spans of 65m in the short and 90m in the long."
Unusually the roof is designed as two way spanning. This design helps the buildability of the structure.
The six trusses which span in one direction can be put up initially and are self supporting until the two other long trusses are in place, when two way spanning action is achieved. The geometry of the trusses was chosen carefully so only four different truss types are needed. Also they were chosen so that the points where the trusses start to taper are in line with the start of the seating – the outline of the field of play is reflected in the ceiling plan.
The roof design looks simple – but it has been carefully co-ordinated with the architecture. "Light pipes, electric light clusters, speakers, HDTV lighting – we need to ensure all these things are co-ordinated in the ceiling so everything in the roof looks like it has its place," says Pye. "We want it to look considered."
The upper part of the building is clad in copper and the colour will develop as it ages. "Copper has a high recycled content – some people quote as high as 70%," says Make partner Stuart Fraser. "Afterwards it’s 100% recyclable."