CONTEXT
In December 2009, the city of Nice launched an international competition for the construction of a new 36,180-seat stadium capable of hosting large international competitions. The stadium would sit at the heart of the Eco Valley in the Plaine du Var, named an ‘Operation of National Interest’ (OIN) in March 2008, and was to be the first flagship project in the new district.
The competition programme – the product of a public-private partnership – included three projects to be built in a seismic zone, each with a different completion date: • a stadium with 36,180 seats, multi-purpose facilities (sports and concerts), UEFA approved, well-integrated with its urban environment, and in line with sustainable development principles • the Musée National du Sport (National Sports Museum) • a real estate development plan (PIA) including 29,000m² of retail space designed to animate the area The Wilmotte&Associés SA / VINCI Concessions team submitted their proposal on 10 September 2010, and the city of Nice awarded t hem the commission in October. In February 2011, the partnership contract was signed with the Nice Eco Stadium Company (a subsidiary of VINCI Concessions), the Caisse des Dépôtset Consignations, and SEIEF (South Europe Infrastructure Equity Finance), and an institutional investor. Nice Eco Stadium was responsible for the design, financing, and construction of the stadium, and will be in charge of operations and maintenance for 30 years.
STADIUM RELATED PROJECT
Real Estate Development Plan (PIA) The intervention included a development plan based on retail, leisure, and food service. This plan was designed to work symbiotically with the stadium to create a coherent complex able to generate urban synergy, use, and energy.
The plan provides more than 29,000m² of retail and leisure-related spaces on one side of the stadium. On the east side, there is a pedestrian mall with direct access to future tramway opening up to the future Eco Quarter.
The retail is mostly located at street level on the stadium concourse. There is a floor dedicated to the retail anchor stores.
The Eco Quarter
The Plaine du Var Eco Quarter, adjacent to the stadium, - spans over 10.6 hectares, 44% of this is designated as residential. This new quarter is inserted within the Plaine du Var landscape. Originating in the Alps and flowing to the Mediterranean, the Var River winds along the valley bottom.
The urban plan is reminiscent of the river’s meandering north to south course through the valley.
This is complemented by a swathe of greenery running from east to west. A ring around the central park creates a ripple in this green swathe, offering a breath of fresh air to the offices and residences that will integrate seamlessly with these green spaces in the years to come.
The Musée National du Sport
The Musée National du Sport is a place for discussing, sharing, and promoting France’s sporting heritage. It is one of the world’s greatest collections of sport-related materials, containing more than 100,000 artefacts and documents, the oldest dating back to the 16th Century. Located in the base of the Allianz Riviera beneath the concourse, the Musée National du Sport has opened in 2014.
URBAN INTEGRATION
Situated five kilometres north of the Nice Côte d’Azur airport in the Saint-IsidoreSud section of the Plaine du Var, the Allianz-Riviera Stadium occupies a strategic position within the Eco Valley project.
Responding to the programme’s first requirement – integration within the Eco Valley landscape - Wilmotte&Associés designed a stadium with an undulating form, evoking the flight of a bird.
With the goal of constructing a slice of the city, Wilmotte&Associés designed a compact, ‘cauldron-shaped’ stadium that would reinforce the urban plan. A network of public spaces and bike paths aligns with the existing urban fabric and roadways. The car parks are located beneath the building complex, leaving space for gardens and landscaping that connect the complex with the rest of the city.
A CONCOURSE IN DIALOGUE WITH THE CITY
Wilmotte&Associés wanted the Allianz Riviera Stadium to be a beacon for the Eco Valley - its crowning accomplishment – and a building that would embody the district’s identity. The complex has a range of integrated functions: leisure and culture for the stadium and the Musée National du Sport, retail for the development plan, and residences and offices for the neighbouring Eco Quarter. The concourse is the link between the city and the stadium. Connected to the ‘40-metre wide road’, it spans the Eco Quarter served by two tramway stops. This large public space opens onto the stadium, facilitating access. The concourse purposefully circumvents the residential quarter so as to not disturb locals. Thanks to its flexibility, the space can accommodate a diverse range of events all year long, and will serve as an everyday link to the Eco Quarter.
THE INTERPLAY BETWEEN OPENNESS AND TRANSPARENCY
Wilmotte&Associés paid special attention to the stadium’s ‘skin’ which animates both the interior and exterior of the building. The architectural parti was transparency: eliminating the distinction between inside and outside, providing views, and making the stadium glow at night. This concept is achieved with the space frame structure, clad with a transparent membrane (ETFE). By day this envelope brings in diffuse natural light, and by night it makes the stadium glow. The structure is visible from the exterior: there is a play of light and shadow between the ETFE and the wooden lattice. The lightweight, airy, and luminous silhouette of the building owes much to this membrane that is set off the structure by metal braces. Acting like a protective veil, the membrane sometimes shelters and sometimes opens the stadium up to its surroundings. From the motorway, the stadium’s closed facade accentuates the iconic presence of the impressive facility. The veil lifts slightly on two sides, opening onto the concourse to welcome the spectators.
This openness, reinforced on the building envelope by the numerous views framing the landscape, contributes to the spectator’s comfort and wellbeing: the relationship between inside and outside can be felt from every point of the stadium. Furthermore, the moment a visitor enters the stadium they are in visual contact with the pitch (or stage) even from the walkways: you don’t have to be in the stands to watch the show. The walkways are wide and generously scaled, allowing rapid evacuation of the stadium and ensuring spectator safety.
INNOVATIVE SYSTEM
Because the stadium is built in a level 4 seismic zone, Wilmotte&Associés designed a light and flexible building capable of absorbing differential expansion and movement in the case of an earthquake. Based on a system of layers, the stadium has a concrete base (including the car parks and stands) which supports the wood/steel structure, to which in turn the continuous transparent ETFE membrane is affixed.
The undulating space frame structure is a latticework of glued laminated timber on the lower surface (for the compressive loads) and a metallic skeleton on the upper surface (for the tensile loads). The attachment of the wood-metal structure to the concrete base creates 60 spans. Each of these terminates in a 46-metre cantilever which overhangs the stands at 30 metres above pitch level.
In order to manage movement in the metal, wood and concrete, and to ensure structural stability in the case of an earthquake, the concrete base is divided into 14 blocks on which the entire wood/metal structure is point loaded: at the top of the stands there is the ‘Carousel beam’. At the bottom of the stands the structure is supported and stabilised by the ‘Atlas beam’: this encircles the concrete base, picking up the compression and tensile loads experienced by the structure (due to snow, wind, and seismic shifts).
THE ONLY STRUCTURE OF ITS KIND IN THE WORLD
With 49,500 m² of covered space, the Allianz Riviera stadium’s structure is the largest wood-metal space frame structure ever built. The selection of wood for the structure was based on two fundamental criteria: its very low carbon footprint (which made a significant contribution to the project’s sustainability) and its optimal strength-to-weight ratio, particularly relevant in seismic zones.
The complex geometry of the structure deforms and undulates in the upper part between the grandstands, curves, and smaller stands. Elsewhere, the roof membrane lifts off the wood lattice in two places, not unlike the lifting of a skirt, to create two entrance lobbies. This geometry had to be rationalised and optimised to enable fabrication; yet despite the structural and financial constraints, the original organic concept of the wood
lattice structure was maintained, conserving its lightness, both physically and visually. During the design phase there were more than 14 different iterations of the latticework: numerous beam assembly mock-ups helped the architects develop the formal and technical solutions. The solution adopted, which combines lightness with solidity, was the diamond-shaped ‘interweaving’ of solid beams and box beams: this method halved the number of metal joints required, which are both heavy and costly. As a result, the structure was made significantly lighter. To maximise the purity of the lattice, the metal joints are concealed by the recessed assembly of the wooden beams.
ACCELERATED BUILDING CONSTRUCTION
Construction of the Allianz Riviera Stadium began on 1 August 2011 and was completed by 29 August 2013: just 25 months of construction for a project of such size and complexity. There were no fewer than 1,000 people onsite daily. 11 cranes, 9,000 tonnes of steel, and 80,000 m3 of concrete were required to construct this building.
There was a policy of sorting and recycling building waste on site. This eco-construction approach resulted in the recycling of 40% of inert and building waste and 200,000 m3 of material extracted from the site.
AN ENERGY PLUS STADIUM
The Allianz Riviera is one of the first energy plus stadiums to be built. Energy control is complex for a project of this type: energy needs are high and concentrated over short periods of time. Sports matches draw extremely high amounts of electricity (pitch lighting) and water (bathrooms, refreshment area, and food service). Wilmotte&Associés and its partners VINCI Construction France and Egis France have created a standard-setting project in terms of sustainable development and high performance technology, one which is principally based on the use of natural renewable resources.
Roof Photovoltaics
The Allianz Riviera is equipped with roof photovoltaics: 4,032 high-performance photovoltaic modules cover 7,500m² and produce 1,500MWh/year (equivalent to the annual use of 616 homes); this provides a large proportion of the building’s electrical needs. The installation and operation of the photovoltaic system is by EDF ENRS (Groupe EDF). The goal is to reach 25,110MWh from renewable sources between now and 2020.
Innovative and Unique Natural Ventilation System
Developed in collaboration with EGIS engineers, the natural ventilation system regulates ambient air flow using the prevailing winds of the Plaine du Var. In the shoulder seasons, this air is ‘stored’ in the stadium’s concrete structures, and then released into lounges via ‘ventilation stacks’. This technology, specifically designed for the Allianz Riviera stadium, significantly reduces energy use associated with interior cooling.
Geothermal
The geothermal system used in the stadium allows for the recovery and reuse of the cooler temperatures of the Var water table pumped from two 40-metre deep boreholes. This reduces the energy costs associated with producing the hot water and cold water used for heating and cooling the stadium spaces.
Reuse of Rainwater for Pitch Irrigation and Toilets
A rainwater collection system is installed on the stadium’s roof. The collected water is stored in four large retention basins on the car park level. These basins are also fed by discharge water from the heat pump. This water is then used as an autonomous way to irrigate the pitch and supply the toilets.
SPECIALLY DESIGNED SEATING FOR ALLIANZ RIVIERA BY WILMOTTE & INDUSTRIES SAS
The Wilmotte& Industries SAS studio designed the seating, fitting out the 24 kilometres of stands at the Allianz Riviera stadium with 35,600 seats. The compact design, complete with folding seats, facilitates building circulation. The W2® is a seat designed to withstand the wear and tear of heavy use both by sports fans and event spectators. Able to be base and wall mounted, the seats adapt to different stand heights. The W2® comes in several versions - with or without armrests, standard or cushioned seat and backrest - to respond to the different levels of comfort required in stadium locations (stands, VIP grandstands, press stands, etc.). The fabrication process was carefully studied by Wilmotte& Industries designers to rationalise and maximise the manufacturing process as much as possible. The backrest and seat are produced from one piece of polypropylene and reinforced with fibreglass. The material is also UV-resistant and self-extinguishing.
Wilmotte& Industries provided OGC Nice with a custom-designed seat bearing the club’s colours (red) on the back, giving the stadium character.
The W2® seat is made and assembled in France. It is marketed by the QuinetteGallaycompany.
ETFE
The stadium’s skin is composed of an ETFE polymer film (Ethylene tetrafluoroethylene) which is 0.25mm thick. Translucent - the film allows 90% of light to pass through - ETFE combines remarkable technical and environmental qualities. Much lighter than glass, its use renders the stadium structure considerably lighter.
The use of ETFE is part of a programme of sustainable development. Produced from a common mineral, fluorine, the amount of energy required to produce ETFE film is equivalent to about 10% of that consumed in the production of glass. ETFE is also 100% recyclable.
