Rapid cycle: building the 2012 Velodrome
Mike Taylor of Hopkins Architects and Andrew Weir of Expedition Engineering explain how collaboration was vital in the design and construction of the Velodrome for the London 2012 Olympics
How did you come to collaborate on the Velodrome project?
A design competition was held for the Velodrome in 2007 inviting multi-disciplinary teams to put forward their designs, so collaboration between the various disciplines was intrinsic from the very start of the project.
What particular engineering issues does a velodrome pose?
There are a number of issues. The complex geometry and steep gradient of the cycling track makes designing for good spectator sight lines very difficult on the steep banks and curves of the track. Creating the right environmental conditions for cyclists is also important so there is the challenge of balancing the Heating/Thermal Control/Daylighting systems to be sustainable yet also maintain the correct standards for competition. There is the challenge of designing the arena lighting to produce 2000 Lux needed for HD television coverage of the Games events, and creating the right acoustics to generate the best possible atmosphere. The track supporting structure itself also has very tight movement and construction tolerances.
What pre-requisites did the project have (ie, is there a specific size and shape an Olympic track has to be, or is there some leeway? Was the amount of space in the middle specified? How about audience capacity - and if not, how was this determined?)
Olympic Velodrome tracks are of a set length (250m) although the geometry can be varied by the track designer. The audience capacity is influenced by the Olympic requirements on spectator numbers and the 2012 Velodrome is being built with 6,000 permanent seats. There was an early plan for 3,000 of the seats to be temporary and removed after the Games but business modelling showed that a 6,000 seat Velodrome had a strong business case and could easily be reused for future cycling events so the decision was taken for all 6,000 seats to be permanent.
The Velodrome is a unique venue in the Olympic Park in that it replaces an existing sporting facility that used to be on the site – the Eastway cycle circuit. One of the clear pre-requisites of the project was for the original Eastway facilities to be replicated in legacy. So along with the Velodrome itself, after the Games the ODA will also build a one-mile road cycle circuit and 6km of mountain bike trails that loop round the outside of the Velodrome, reinstating the cycling facilities that once occupied the site before the Games.
How was the sport’s governing body involved in the design?
British Cycling has been involved throughout the duration of the project, in helping select the winning design team, through to helping advise on design and construction issues as the venue took shape to ensure the needs of cyclists will be met by the new facility. Olympic triple gold medallist Sir Chris Hoy was also part of the design jury that picked the winning design team and made a number of key points about the design and layout of the Velodrome facilities which were taken on board as their designs progressed.
What materials are used in the construction of the velodrome? How was this decided?
In terms of structure, we went for steel to form the upper bowl due to its strength and ease of forming the complex forms resulting in the interaction of the roof, external façade and upper seating tier. The lower floors, columns and foundations are in-situ concrete not only for their architectural merits but also they add mass which helps resist the overturning forces generated by the roof cables.
Given the tight programme, it was also of benefit to keep the first part in in-situ concrete and the remainder in steel, which has a longer lead-in period.
For ease of erection, structural and cost efficiency a cable net was used to support the roof which is formed from timber cassettes. Above that is approximately 300mm of glass fibre insulation from recycled glass and a mill finish standing seam aluminium roof.
What’s the most notable feature that grew out of engineering/architecture collaboration?
Our concept was for the venue was to evoke the geometry of the cycling track in the form of the building, which after much refinement resulted in the double-curved roof form (nicknamed the Pringle). We also wanted to match the efficiency of a bicycle in the design and construction, albeit at a completely different scale.
Like bike design we put great emphasis on reducing the weight and therefore the amount of materials used. In the case of construction, the weight savings don’t increase speed but do reduce its carbon footprint.
This is a clear collaboration between the architectural concept and the engineering solution of using a lightweight cable-net roof structure to form the distinct shape.
Only through the whole design team working in tandem was such an integrated design possible. The benefits of this approach are the leanness of the design: the efficient and appropriate use of the materials, a geometry that leaves no wasted spaces and the multi-functionality of elements.
In terms of the sport, is the idea to build the fastest track ever? Or are there different priorities?
Track cycling has different disciplines with sprint events and longer endurance events. Having the fastest possible track for sprint cyclists is important but has to be balanced against the needs of the endurance cyclists.
What factors come together to make a track fast?
The track geometry has to be right, with steep banks that sprint cyclists can use to build up speed as they enter the flat straights. This has to be balanced by the needs of the endurance event cyclists though who require slightly gentler angles on the banks of the track. The temperature and environmental conditions at track level are also essential, with a higher temperature helping rarefy the air allowing cyclists to pass through the air quicker. Crowd atmosphere is also important and the Velodrome is being built to have seating all the way round the track to create a continuous wall of noise.
Were cyclists actively involved in the design? If so, how?
As outlined above, Sir Chris Hoy was also part of the design jury that picked the winning design team and made a number of key points about the design and layout of the Velodrome facilities which the winning design team subsequently took on board as their designs progressed.
This included the importance of having seating all the way round the Velodrome track -many Velodromes do not have continuous seating all the way round the track, meaning that cyclists have the crowd behind them on the straights but hit silence when it comes to the bends which can be off-putting to cyclists.
It is also important to have key facilities within the Velodrome, such as changing rooms and toilets, close to the track and infield to minimisedisruption to cyclists and their pre-race preparations. With the track itself, the temperature is key with just a few degrees making the difference in creating record breaking conditions. Getting the track at the right temperature and maintaining it throughout events is essential. All of these points were taken on board and incorporated as the Velodrome designs moved forward.
How did the roof design evolve?
We originally anticipated that a cable net roof would be the most efficient but not until the Main Contractor ISG was on board could this be proved on a programme and cost basis. During design development we looked at all the options from steel sections to glulam to composite solutions. We had always aspired to use wooden panels to form the roof but the actual cassette design was the subject of much research and development.
Was any new technology developed for the velodrome? If so, where and under what circumstances could this be applied again?
It is one of the first times such a large cable-net roof structure has been used in the UK. Cable-net roof structures are commonly-used in Europe but not in the UK. It’s not so much constructing the cable net, it’s more the provision of large quantities of insulation (hence a need for rigid panels to support it) and topping it with the Aluminium that is the step forward, The technology from our side was the extremely in-depth analysis of the movements of the roof. The movements of the cable net require a sophisticated jointing system between the panels to ensure the integrity of the waterproofing layer.
What features are built into the velodrome to allow it to be used by paralympic athletes?
Ensuring accessibility to the Velodrome presented key design challenges. Most other indoor cycle tracks only offer limited accessibility because lifts can’t be built in the track centre as they block the internal views across the track. Disabled viewing areas are also difficult because seating areas have to be very steep to achieve reasonable sight lines since the track itself is so steeply banked.
The 2012 Velodrome design overcomes this by adding two ramps beneath the track area that access the infield, allowing accessible routes into the track areas. The 6,000 seats are also split above and below a fully accessible public concourse that runs around the perimeter of the trackside seating, allowing wheelchair access to the best viewing points.
How will the venue change after the Games, ie is there a ‘legacy configuration’?
The Velodrome itself stays largely the same, with all 6,000 seats remaining and only a few temporary fixtures and fittings removed. The BMX circuit is tweaked so that the levels and jumps are more manageable for riders of all abilities. After the Games, there is also then the installation of a 1 mile road-cycle circuit and 6km of mountain bike trails which will loop around the outside of the Velodrome. Together, the various cycling facilities will form a legacy VeloPark.
How much did the velodrome cost? Were there budget overruns? If so, at what stage were they encountered?
The budget for the entire VeloPark (both the Velodrome and the BMX circuit, plus the legacy cycle facilities) is £100m.