Proceedings of ICE Civil Engineering 164 November 2011 Pages 51–58 Paper 11-00028 http://dx.doi.org/10.1680/cien.2011.164.6.51 Keywords buildings, structures & design; olympics; sustainability Delivering 2012: the

Richard Arnold The 6000-seat Velodrome is host venue for track cycling during BSc, MRICS is project sponsor at the Olympic the London 2012 Olympic Games and Paralympic Games Delivery Authority as well as the centrepiece for a velopark in legacy mode. As described in this paper, it is designed around optimal spectator and performance volumes, and every element was reduced to an absolute minimum so the structure and environmental services are as light as possible. This resulted in an innovative design, Chris Banister BA, BArch, RIBA including a lightweight cable-net roof that reduced the embodied is a partner at carbon dioxide content by 45% compared with a traditional steel structure and cut the construction period by 5 months. The energy performance of the building also maximises natural ventilation and use of daylight.

Andrew Weir MSc, CEng, MICE, MIStructE is an engineer at Expedition The Velodrome is one of the permanent added a 1·6 km road circuit and 7 km venues to be built for the London 2012 of mountain bike trails, which will Olympic and Paralympic Games and be owned and operated by Lee Val- is located in the north of the Olympic ley Regional Park Authority (Figure 1). Park in Stratford. After the games, the Schools, colleges, the general public and venue will become the centrepiece of a practising athletes alike will be able to new ‘velopark’ alongside a re-configured use the facilities for years to come. Olympic BMX track. To these will be A permanent velopark was a key Davendra Dabasia MSC, ICIOB is CLM project manager for the Velodrome

Dean Goodliffe BSc is principal contractor at ISG

Figure 1. The Velodrome will become the centrepiece of a new legacy velopark, with a reconfigured Olympic BMX track, 1·6 km road circuit and 7 km of mountain bike trails

CIVIL ENGINEERING 51 ARNOLD, BANISTER, WEIR, Dabasia and GOODLIFFE

promise of London’s bid for the 2012 tal conditions for record breaking and n To use manufacturing and construction games. The site was previously home highlighting the importance of dedicated expertise from the earliest opportunity. to Eastway Cycle Centre’s road circuit athletes’ toilets close to the track. n To have low embodied energy. and off-road trails course, so one of the At the heart of the delivery of the n To allow low in-use energy Olympic Delivery Authority’s (ODA’s) project, ODA was looking for a team of requirement – as an absolute minimum commitments was to replace and designers that would work in partnership to perform at least 15% better than enhance these facilities after the games. to deliver the highest quality in design, the Building Regulations 2006 part L. A competition for the design of the innovation and sustainability – ‘a team, n To connect to the park-wide district Velodrome and surrounding velopark not a scheme’. This led to a truly collabo- heat and power system. was launched in February 2007, result- rative effort. n To achieve a Breeam sustainability ing in over 100 entries. This led to the assessment of ‘excellent’. appointment of a design team compris- The key performance criteria n To treat the design and construction ing Hopkins as architect, Expedition as process as one single collaborative structural and civil engineer, BDSP as The key performance criteria for the exercise. service engineer and Grant Associates as Velodrome included the following. landscape architect. Track designer Ron The conceptual response Webb was appointed directly by ODA. n To be constructed on a site that ODA’s brief for the Velodrome was for partly overlies the disused West Ham The concept for the Velodrome was a 6000 seat venue that would provide refuse tip. inspired by its future role as a hub for all top-class cycling facilities both for the n To operate a 250 m long hand-laid forms of cycling within the Olympic Park. games and in legacy, and would be a timber track in a range of modes, from The conceptual challenge was how to venue to inspire generations today and in daily public practice sessions in winter form a symbolic and visual link between the future. To deliver these expectations, with very low overall occupancy to the indoor track and the range of external ODA ran a Royal Institute of British a full 6000-seat arena for televised forms of cycling that would be on offer Architects (Riba) design competition that events in summer with elite riders after the games including BMX, mountain included four-times Olympic gold medal- (such as London 2012). bike, cyclo-cross and road cycling. Not list on the jury. Hoy also pro- n To integrate fully into the London only did the team want to break down the vided subsequent input to the appointed 2012 master plan (games and legacy) barriers between the various disciplines design team from an athlete’s perspective providing a key architectural ‘anchor’ but it also wanted all of these activities as to what was important in creating a for the north of the park. to be immediately visible, including the state-of-the-art velodrome. His insights n To be easily convertible after the indoor track, from the legacy park. ranged from providing seating all the games into legacy mode. The formal response was very simple – way round and improving the intensity n To employ latest or first-principles the team split the 6000 seats in the brief of the atmosphere for the crowd and the design to maximise overall horizontally so that half were around athletes to creating the right environmen- performance. the perimeter of the track and the other

The concept for the Velodrome was inspired by its future role as a hub for all forms of cycling within the Figure 2. The design concept was for a concourse viewing gallery that links the internal cycling environment with the external cycling circuits Olympic Park

52 ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 issn 0965 089 X Delivering London 2012: the velodrome

half were raised into the roof space construction programme by 5–6 months collaborative approach of the whole design (Figure 2). By creating this separation, and jeopardised the March 2011 con- team working with specialist subcontrac- the team was able to introduce a band of struction completion date. tors occurred throughout the project, with glazing around the spectator concourse A study was commissioned into alterna- notable success on the tensioned cable forming a continuous ‘picture window’ tive roof systems, including a tensioned roof but also on the structural timber roof between the internal environment of cable-net, compressive steel arches, glu- cassettes, the Kalzip roof and the external the 250 m track and the external cycle lam timber arches and a cable–timber western red cedar cladding. circuits within the park. The resulting hybrid system. From this, the cable-net concourse is a viewing gallery, where it is roof emerged as the preferred option as, Structural concept possible to watch over all the disciplines despite its relatively high capital cost, this The pivotal design decision in the simultaneously. The architectural look of was offset by the much faster construction structure was to integrate the cable roof the Velodrome is of a minimal ‘shrink- programme. The virtual elimination of all structure fully with that of the grid shell wrapped void’ defined by an ethereal scaffolding and temporary works effective- of the seating bowl, rather than allow and transparent waistline. Working as an ly provided a cost-neutral, faster and less them to move relatively independently of integrated design team, the team pursued risky solution and was ultimately adopted. each other, as is usually the case for large an agenda of form following function. Overall, the programme was achieved in stadia. This decision allowed the curved Inspired by the dynamism and geom- 23 months and completed 8 weeks ahead seating bowl to receive roof forces direct- etry of the Siberian pine track and the of the construction completion date. ly, either to carry them in cantilever action engineering rigour of high-performance Importantly, the cable net also gave a or to share and distribute them around bikes, the team set out to design a build- 45% saving in total embodied carbon down to the substructure (Figure 4). ing that made no distinction between dioxide in the primary structural elements architecture and engineering. The aim over the steel-arch option. This was pri- was for the resulting form to be lean and marily achieved by the reduction in the efficient, and to perform at the highest roof steel weight from 1300 t to 160 t. sporting levels in terms of function. It is The contractor instigated a series of designed around the minimum specta- workshops that ran in parallel with the tor and performance volume, and every revised detailed design programme. The element was reduced to an absolute key to the success of the new roof scheme minimum so that the structure and the was having clarity on the lines of responsi- environmental services are as intrinsi- bility in relation to design and then allow- Figure 3. Cross-section of seating tiers – lean cally light as possible (Figure 3). ing the specialist input to be integrated into construction has resulted in an intrinsically light The upper bowl is an outward expres- the project at key strategic moments. This structure sion of the track since its geometry flows from the upper tier of seats that is, in turn, tightly wrapped around the track perimeter. The form of the build- ing therefore echoes the sporting action within and becomes a manifestation of the energy and gravity-defying dynamism of track racing. It is intended to inspire future generations of cyclists as well as architects, engineers and clients. Engineering design and analysis

Roof selection The key innovation incorporated on the project was the roof. The initial stage D design had a traditional steel roof. An alternative cable-net system was dis- counted early on as this was a relatively unused construction method in the UK and was therefore viewed as a construc- tion and cost risk. However, the contrac- tor, in conjunction with its specialist tier 2 supplier Pfeifer, suggested that the use Figure 4. Three-dimensional model depicting the cable-net roof construction – the roof is suspended directly of steelwork would have elongated the from the seating bowl, requiring only a planar ring truss issn 0965 089 X ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 53 ARNOLD, BANISTER, WEIR, Dabasia and GOODLIFFE

The concept removed the need for the conventionally very large ring beam or truss at the edge of the roof. As a result, the structure only needed a minimal ring truss flush with the edge of the roof that could be laid flat to follow the roof curvature, giving the possibility of using the planar ring truss as a construction walkway, making use of it as a safe jack- ing gangway, allowing its use directly as a broad rain gutter and leaving a very crisp, sharp architectural edge to the roof on the skyline. The cables forming the structure to the doubly curved roof are stressed against the perimeter ring truss, which is integral Figure 5. A whole-building analysis model was developed to assess the design forces and movements of the with the steel bowl forming the upper ring truss and seating bowl tiers. The roof is supported by pairs of spiral strand cables, each only 36 mm in diameter arranged in pairs at 3·6 m centres in both directions. The average weight of the cable-net roof system is Aluminium standing seam roof an extremely efficient 30 kg/m2, which 300 mm insulation providing overall U value includes cables, connections, end connec- of 0.15 W/m2K tion and also the minimal ring truss at Vapour barrier the top of the seating bowl. Timber roof cassette with birch-faced plywood soffit incorporating steel corner brackets Due to the integral nature of the roof, ring truss and steel bowl, a ‘whole-build- ing’ analysis model was developed and used extensively (Figure 5). A parametric

Fabricated steel powder-coated receiver brackets with approach was used to reflect the indeter- PTFE coating to underside minate nature of the structure, leading to a range of design forces and movements. Fabricated steel powder-coated connection plate with PTFE coating to top. Combination of fixed, slotted and Maximum cable tensions are estimated oversized holes varies with location as being approximately 650 kN per cable and all cables were prestressed to remain Steel powder-coated washers in tension under all loading conditions. Because of the integrated structure, Nut approximately 40% of the cable forces are resolved within the upper bowl and ring Galvanised forged steel top cable clamp truss, while 60% of the cable forces gener- ate large overturning moments in the sub- structure, which are resisted by the dead Galvanised forged steel middle cable clamp with paired weight of the foundations. In addition, the 36 mm diameter cables at 120 mm centres

Galvanised forged steel bottom cable clamp

Bolt-through cable assembly

Galvanised forged steel coverplate with connection for lighting containment

Figure 6. Components of the articulated connection between the cable-net nodes and structural timber infill panels – these had to allow for the flexibility of the cables but limit relative movements of the standing Figure 7. Roof connectors were attached to the seam roof covering cable-net nodes before it was lifted into position

54 ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 issn 0965 089 X Delivering London 2012: the velodrome

track-level slab behaves as a plate, setting disadvantages of increasing cost, construc- The large overturning moments from up a complete building system in equilib- tion time, size and embodied energy. the post-tensioned piers holding up the rium by distributing the horizontal forces seating bowl needed to be transferred from the seating bowl and roof system. Substructure and foundations out at ground level. The ground was not A major challenge involved designing The Velodrome is located on a brown- suited to tension piles and so the struc- the connection of the structural timber field site on top of the old West Ham ture has a ring of eccentrically placed roof panels, which infill the gaps between landfill site. The first 10 m is made ground, large pile caps to counter overturning the cables, to the cable net. These inher- which is underlain by alluvium, river ter- (Figure 8). ently inflexible panels had to adapt to race deposits, the Lambeth Group, Thanet the relatively flexible cable-net roof that Sand and, finally, chalk. Much of this area Construction sequence supported them, while keeping relative of London was heavily bombed during A detailed staged analysis covering movements of the delicate standing seam World War II so the risk of unexploded erection of the steel bowl, cable-net roof roof above within very tight range. In ordnance led to each of the approximately and roof cladding panels was carried out response, an articulated connection sys- 1000 pile locations being probed. and required close coordination across tem was developed (Figures 6 and 7). Approximately 600 of the piles are the design and construction team. Wind- precast (270 mm × 270 mm, low-load, tunnel testing of the construction stages Structural dynamics 9 m length), which removed the need for was commissioned from BMT to guard The dynamic performance of the Velo- disposal of contaminated arisings and against misbehaviour of the part-clad drome has been assessed using the latest suited the light loading requirements of roof under significant uplifts and local procedures and guidance from the Institu- the infield slab. The remaining piles are wind pressures. tion of Structural Engineers (IStructE, open-bored and cast in situ, of which The cable net was laid over the 2008). The lowest mode that mobilises there were around 70 of 750 mm diam- concrete seating bowl and jacked into the seating terraces of the upper bowl was eter and 300 of 450 mm diameter. They position from the ring truss (Figure 9). estimated as being approximately 2·3 Hz, were installed to around 24 m depth, Safety netting was suspended beneath, well below the 3·5 Hz threshold histori- giving a 3 m embedment into the Thanet ready for installation of the drop-in tim- cally seen as an acceptable lower bound. Sand. Sheet piles that were originally part ber roof cassettes. The IStructE methodology uses spring– of temporary works were incorporated A cable erection sequence for the cable mass–damper body units to represent into final basement wall design, bringing net was developed by Pfeifer in conjunc- the effects of crowd loading and human– cost and programme efficiencies. tion with ISG and Expedition. In gen- structure interaction. Using this method, Building on a brownfield site posed eral, the construction stage forces applied the design criterion is to limit the maxi- additional challenges. The 10 m deep old to the permanent structure were within mum vertical root mean square accelera- fill emits methane that, if concentrated the design forces, but in several loca- tion to 0·075g, which was easily achieved. inside the building, could be problematic. tions it was found necessary to increase It is notable that a side study showed The protection strategy was to wrap and the capacity or add a small amount of that several hundred tonnes of steel would seal the underside of the building in a kentledge. During erection of the roof, have needed to have been added to the gas membrane and channel gas though installation cable forces were measured structure to bring its stiffness up to the tra- passive venting to the side of the build- and compared against the analysis model ditional 3·5 Hz threshold, without tangible ing, where discreet gravel trenches dis- – good agreement was achieved with the benefit to the occupants and with the great perse the gas. theoretical values.

Figure 8. A ring of eccentrically placed large pile caps resists the large overturning moments from the post-tensioned piers holding up the seating Figure 9. Cable net being jacked into position from the conveniently flat ring truss – installation forces in the bowl and cable-net roof 16 km of cabling were close to those predicted

issn 0965 089 X ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 55 ARNOLD, BANISTER, WEIR, Dabasia and GOODLIFFE

Sustainability adhesives with low volatile organic com- and heat emitting, and there are restric- pounds contributed to the achievement tions on opening windows due to secu- Materials of the sustainability objectives. rity and safety concerns. The Velodrome design sought to opti- As with all Olympic venues, the Velo- Faced with these challenges, the pro- mise the use of materials and minimise drome was required to reduce potable ject team adopted a holistic design phi- the environmental and social impact of water demand by 40%. Half of this losophy of primarily minimising demand the materials that were specified. One amount was achieved by the use of for energy as far as possible through of the most visually apparent materials water-efficient fittings and half by rain- passive measures. The building services used, externally and internally, is tim- water harvesting to supply water to the engineering design focused on the needs ber – a natural, replenishable material toilets and landscape irrigation. On aver- of the Velodrome when in legacy mode that was 100% legally and responsibly age, approximately 550 m3/year of water while also meeting the more intensive sourced (Figure 10). will be harvested: to achieve this, a tank needs of the games. The lightweight cable-net roof is a of 25 m3 capacity has been provided. At Riba design stage E, the building significant sustainability achievement. It design was 35% better than part L significantly reduced the roof’s embodied Environmental and energy strategy of the 2006 Building Regulations (a 2 energy by 45% compared with a much Cyclists need calm air at track level building emission rate of 39 kgCO2/ m ), heavier traditional steel truss solution. and prefer higher temperatures (26– significantly exceeding ODA’s 15% Additionally, the use of 29% recycled 28°C) as a lower air density means they target and meeting the low-in-use energy content in the building (Figure 11), 98% can gain a few milliseconds and break objective. responsible sourcing of materials and the records. However, spectators want to be The arena will be heated in winter, use of ‘healthy’ materials such as water- much cooler. Furthermore, events light- initially by underfloor heating, and based paints and form-release agents and ing requirements are energy consuming supplemented by mechanical ventilation to achieve air temperatures applicable to use: typically 18°C for general use and 24–26°C at the track in training mode for professional cyclists. Whenever possible, external louvres set at high and low level in the facade will open to ventilate the arena naturally. Air recirculation will be used in periods of low occupancy (Figure 12). Computational fluid dynamics analyses were used to show that, using passive means only, internal air temperatures will not exceed 3°C above external temperature during a summer event. Windows and rooflights have been 2 Figure 10. The 5000 m external western cedar cladding was responsibly sourced using Forest Stewardship optimised to allow adequate daylight into Council (FSC) certified timber the field of play and also into administra-

Natural ventilation

Mechanical ventilation and heating Figure 11. Recycled aggregate from demolition in the Olympic Park was used in gabion walls, Figure 12. Heating and ventilation arrangements – whenever possible, external louvres set at high and low contributing to over 29% recycled content level in the facade will open to ventilate the arena naturally

56 ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 issn 0965 089 X Delivering London 2012: the velodrome

tion spaces, thus reducing dependency on Construction management needed to get the building substantially artificial lighting energy (Figure 13). Typ- Construction of the Velodrome was a watertight were installation of the cable ically, only 300 lux illumination is neces- testament to delivering an iconic venue net and roof cassettes. The cable net was sary for day-to-day use. Extensive studies in a lean way by incorporating innovative installed in 2 months. Compared with were carried out to optimise the area and solutions and maximising off-site fabrica- the proposed programme of 7–8 months arrangement of the rooflights in terms of tion. The critical path of the construction for a traditional steel structure, this was cost, weight, lux levels and uniformity. works ran through the structure, firstly a key component in ensuring the over- The high level of energy efficiency for weathertightness and then watertight- all build programme was achieved in was achieved by placing sustainability ness. As such, the key focus of the team 22 months. at the core of the design from the out- following substantial completion of the The cable-net installation was broadly set. A combination of energy-efficiency concrete works was completing the roof split into two distinct phases. The first measures work together as a complete, and cladding works. phase was laying the cable at ground integrated solution. The venue is on track The major elements of the roof work level while also attaching the roof cas- to achieve a Breeam sustainability assess- ment of ‘excellent’ in legacy, subject to some programme-wide initiatives being completed. Implementation

ISG was appointed as principal con- tractor for the Velodrome project in June 2008. The basis of the design and build contract was an NEC3 Engineering and Construction Contract option C (ICE, 2005). The procurement was done in two phases with an initial target price based on preliminaries, overheads and profits. The team then worked to get to a final target price at Riba stage F, at which point the design team was then novated to the contractor. In addition, incentive milestones were introduced to drive delivery. Good performance on the Velopark has resulted in an anticipated final cost of £102 million (including legacy transfor- mation) of which £93 million is funded by ODA and £9 million is from external Figure 13. Windows and rooflights have been optimised to allow natural daylight onto the track, reducing funding. dependency on artificial lighting energy The revised programme targeted a project start date of February 2009, completion of stage E/F in March 2009 and contract completion in January 2011. Subsequent extensions of time due to resilience and weather took this completion date to February 2011. ODA held a further 3 weeks of float against the construction completion milestone (i.e. handover to the London Organis- ing Committee for the Olympic Games (Locog)) on 11 March 2011. Performance against the schedule for the Velodrome delivery resulted in early completion of the building on 13 January 2011, 7 weeks ahead of the baseline and Figure 14. The £93 million Velopark, in which the Velodrome was completed 7 weeks ahead of schedule 18 months before games (Figure 14). issn 0965 089 X ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 57 ARNOLD, BANISTER, WEIR, Dabasia and GOODLIFFE

sette node connectors to minimise works Conversion for legacy mode everything else to see the light of day. If at high level. This took approximately such collaboration could be replicated as 5 weeks. The second phase was the lift- The essential requirements to create a a matter of course elsewhere, many other ing of the cable net into its final geom- venue for legacy are all contained within apparently intractable problems would etry, including all final connection and the initial concept. From the start, the perhaps turn out to be nothing of the testing works. This took approximately team considered it more appropriate that sort. The project has been well received 3 weeks. the building was conceived for legacy so far and was handed over to games Following successful completion of and ‘converted’ for the games rather operator Locog in February 2011. the cable-net installation, 1090 roof cas- than vice versa. For example, the team settes needed to be installed in approxi- included extensive rooflights to reduce Acknowledgements mately 3·5 months. To add a degree of whole-life lighting costs. complication, works had to progress Working closely with local cycle groups, The authors acknowledge the contribu- simultaneously on both sides so as not the team developed an intricate series of tions of Chris Wise (Expedition), Klaus to destabilise the structure. This chal- cycle circuits around the Velodrome and, Bode (BDSP) and Michael Taylor (Hop- lenge was overcome and, at peak, one where possible, included their construc- kins) to the preparation of this paper. prefabricated roof cassette was being tion in the base build. In the spirit of The principal participants in the design lifted from ground level and fixed into efficiency, one of the construction bridges and construction team were the node connectors every 10 minutes. across the River Lee was retained as part In addition to this, the underside of the of the road circuit. The final implementa- n ODA (client) roof was prefabricated off-site with the tion of these circuits is only possible when n CLM (delivery partner/project manager) finished birch-faced plywood. There- the games ‘overlay’ is removed and the n Hopkins Architects (architect) fore, with completion of the roof cas- legacy transformation can complete the n Expedition (structural engineer) settes, not only had the building been Lee Valley velopark in 2013. The velo- n BDSP Partnership (mechanical elec- made substantially weathertight but the park will then be taken forward through trical plumbing engineer) finished roof for around 13 300 m2 of the ownership and management of the n Ron Webb (track designer) the auditorium had also been achieved Lee Valley Regional Park Authority who n ISG (main contractor). (Figure 15). already have funding in place to subsidise The cladding panels followed a simi- the facility for the next 25 years. The key specialist suppliers were lar process to that of the roof cassettes. The added complication on these was Conclusion n Pfeifer with Schlaich Bergermann that almost all of the wall cassettes were (cable net) different and their installation needed While the project team might find it n Kalzip (roof covering) bespoke equipment due to the geometry tempting to celebrate its technical wiz- n Watsons (structural steel) of the Velodrome. This work was pro- ardry, aesthetic touch or environmental n Foundation Developments (concrete gressed over a period of 5 months to subtlety, its defining overriding success substructure and superstructure) ensure that the building was fully water- was really good collaboration. Often n Wood Newton (roof cassettes and tight, thereby taking the western red claimed but seldom achieved, this is the external timber cladding) cedar installation of the critical path. feature of the project that has allowed n Rock & Alluvium (piling).

References ICE (Institution of Civil Engineers)(2005) NEC3 Engineering and Construction Contract Option C. Thomas Telford, London, UK. IStructE (Institution of Structural Engineers) (2008) Dynamic Performance Requirements for Permanent Grandstands Subject to Crowd Action. IStructE, London.

What do you think? If you would like to comment on this paper, please email up to 200 words to the editor at [email protected]. If you would like to write a paper of 2000 to 3500 words about your own experience in this or any related area of civil engineering, the editor will be Figure 15. The 12 000 m2 roof is made from 1090 timber cassettes that had to be placed in just 3·5 months happy to provide any help or advice you need. to keep the build on programme

58 ProCeedings of the Institution of Civil Engineers – CIVIL ENGINEERING, 2011, 164, No. CE6 issn 0965 089 X