IOC/IAKS Award für Beispielhafte Sport- und Freizeitanlagen und IPC/IAKS Auszeichnung für Barrierefreiheit 2013

THE VENUE
London will be the first city to host the Olympic Summer Games for a third time, and the
organising committee intends to showcase the city’s capability in hosting spectacular, efficient and innovative Olympic and Paralympics Games. Embedded in the London Games design parameters is the need to provide for the future, the Legacy of a major event, which requires transformation of the city and the venues – challenging the concept of building permanence.

To achieve a balance between the immediate needs of the large Games stadium against a long term, small scale venue, Populous have embraced the opportunity to develop the architectural language of venue design. We have progressed a new theory of ‘embracing the temporary’, by exploring form, materials, structure and operational systems to bring a structured palette of elements into a cohesive design. Simple legible forms develop, minimizing the physical weight, fabrication time and embodied energy of each component – bringing together a compact structure formed by demountable connections. This not only enables the overlay of theatre and spectacle in staging the Opening and Closing Ceremonies for the 80,000 capacity venue, but also promotes possibilities of transformation after the Games down to a minimum 25,000 seat venue form.

The London Olympic Stadium is sited on a diamond-shaped island between two existing waterways, located within the southern section of the new Olympic Park. The seating bowl is compact, bringing all 80, 000 spectators far closer to the event than previous Games venues. The design makes full use of the site’s island situation, providing a complete circuit of spectator podium concourse around the stadium, connected by bridges to the main park. This podium concourse promotes the carnival nature of the event with a perimeter array of spectator facilities, particularly retail and food service, distributed along the natural boundary of the water’s edge. During the three hours of an athletics event, spectators are free to move from their seat out onto the podium to visit these colourful clusters of concession pods, and view across the waterways the activities in the adjacent park and venues.

The key sustainability criteria of reduce, reuse and recycle were adopted to create a compact, flexible and lightweight design. The main Stadium structure is light and elegant, clearly expressed by the external diagonal articulation of the white tubular steel of the roof and the internal slender black steel supporting the temporary upper seating tier. Between these two frames lies the concourse façade, the full height ribbon sections of the fabric ‘wrap’. The black and white seats provide a neutral backdrop for the interior colour of the spectator facilities and pathways, and the animation that spectators will bring to the event.


THE ROOF
Athletics is a sport particularly sensitive to wind conditions. Should cross winds or head winds also be strong then it makes it harder for the athletes to reach their peak speeds. Furthermore, if the wind speed is to exceed a record high tailwind of 2m/s to be broken the IAAF cannot allow events to stand. Therefore, it is essential that the design of an athletics stadium reduce wind speeds to within this threshold as much as possible. In extreme adverse weather, it is common for athletics events to be postponed irrespective of the stadium design.

At an early design stage, computation fluid dynamic (CFD) modelling was undertaken on a number of roof coverage options to establish the optimum wind performance level, given obvious cost constraints. Physical wind tunnel testing was conducted to verify that the wind speed restrictions could be met. In comparison to previous years’ weather reports, the results suggest that the wind speeds at the recorded points will be below the threshold for the majority of the days of the athletic competition. From these results, the amount of roof cover was established resulting in approximately two thirds of the spectators’ seats being located under cover, which was deemed acceptable by the client.

To support this amount of roof, a number of design solutions were investigated including conventional cantilevered solutions. Typically cantilevered solutions are economically efficient up to a tipping point whereupon the amount of steel necessary becomes disproportionate. The amount of roof cover and the elliptical shape of the seating bowl allowed the design team to consider employing a ‘bicycle-wheel’ type roof, which can be extremely efficient both in terms of the materials employed and economically. The design developed with a truss around the perimeter of the stadium which is pulled into compression by a ring of cables at the inner edge of the roof, and radial cables which run between the compression truss and the inner ring, all of which are in tension. The overall ‘wheel’ of the roof is therefore in equilibrium and simply needs to be supported from below and any rotation resisted; which is why the columns that support the compression truss are angled both in section and elevation. This creates a self-stable structure, independent of the seating bowl to keep the dynamic forces of the two systems separate. The roof covering is a series of pre-shaped PVC-coated polyester fabric panels, approximately 1mm thick, which are clipped to the cables and tensioned into their final 3-dimensional form.


SPORTLIGHTS
The demands of televising the athletics results in very high light levels on the field of play in order to allow the coverage to include slow-motion high -definition TV. In order to prevent glare for the spectators and competitors and lens flare for the TV camera, the angle that the light falls on the field of play needs to be carefully controlled. Due to the compact design of the stadium and the amount of roof cover, the sports lights needed to be located above the inner edge of the roof. There are 14 lighting paddles (or rigs) placed on top of the tension ring to position the lights in the correct location. Their form reflects the other triangular geometries of the stadium design.

The efficiency of the design allows the embodied energy within the structure and fabric of the roof to be kept to an absolute minimum. It is therefore one of the most significant environmentally sustainable aspects of the stadium design.


SUSTAINABLE DESIGN
The aim of the Team was to design the most sustainable Olympic Stadium to date and reduce the amount of steel and concrete needed, making it one of the lightest stadia of modern era. The embodied energy was reduced by minimising physical weight, reduction of fabrication time and details which allowed for rapid erection and later dismantling. The design team adopted key sustainability criteria to reduce, reuse and recycle to create a compact, flexible and lightweight design that allowed for a cost-effective life cycle compared to similar building of this type and scale.

Possibly one of the most important factors that influenced the use of concrete was to manufacture it at a batching plant, located next to an existing rail link on site, guaranteeing high environmental targets were achieved. This enabled all materials to be delivered by rail in bulk rather than by road which kept thousands of lorries of the road system in London preventing possible congestion and pollution. Also having space for a precast yard on the Team Stadium site allowed for reduced transportation of several major building components. The ODA set up focus group to ensure that delivery of the targets set out in the brief were met by the design teams. With the use of materials including recycled aggregates, GGBS and PFA, the recycled content of the concrete was increased to achieve and improve the ODA requirements.



KEY FACTS
LOCATION: Olympic Park
CLIENT: The Olympic Delivery Authority
ARCHITECT: Populous
CAPACITY: 80,000 Olympic / 25,000 Legacy
EVENTS: Athletics / Opening and Closing Ceremonies