Steel superstructure for Alfred Nakache Sports Centre: A solution for weak ground and a confined construction site

Detailed information

The local sports centre & its design

The dual aim of this ambitous project was to manage the facility’s impact on the external environment and to create a healthy and comfortable internal environment. The stainless steel swimming pool liners, the first of their kind in Paris, and the steel superstructure are among the choices that were key to achieving these objectives.

Opened in April 2009, the sports centre was eagerly awaited by the residents of Belleville.  A building of great architectural and civic quality, it remedies an obvious dearth of amenities of this type in a very densely populated district with a young population that extends across four of the capital’s arrondissements.

Constructed in line with the other buildings and as an extension of the existing building outlines, the centre comprises an aquatics centre with three pools – a 25-metre sports pool, a teaching pool, and a paddling pool - and four studios, each 150 m² in size.

Wishing to provide a high degree of readability for the users, the architects determined a very clear scheme layout.

The compact, rectangular building occupies the length of the walkway, perpendicular to the street, of which almost a quarter of the area is landscaped as a garden accessible from the pool. In plan, it is divided into two longitudinal bays bordered to the south by a garden. The first is devoted to the changing rooms, showers, and a sauna, while the second is occupied by the sports facilities, which are superimposed. Only the paddling pool escapes this division and breaks with the building’s sleek lines: its flowing form is housed in a single-storey water pavilion located in the garden. The entrance lobby and horizontal and vertical circulations connect the bays.

Thus, in section, the ground floor is occupied by the 'water hall' with its three pools.  It is visible from the street through the entrance lobby. Architect Patrick Berger explained that the water surface and the urban street almost merge, and so the activity of swimming comes into the city.  Above this hall, the dance, bodybuilding, and fitness studios succeed one another.  Out of respect for the neighbourhood, no studio looks directly onto the outside world.  However, they are all illuminated with indirect daylight through the circulation that serves them along the garden facade.

On the third and final floor, the dojo (a martial arts room) looks out onto a vast terrace overlooking the block’s rear plots.  Access is via an outdoor walkway.

The swimming pool changing rooms are located in the first basement level, along the pool footprint and on the first floor, which exists only in the services bay - the pool bay and the entrance lobby being double-height. On the upper floors, the changing rooms and showers are adjacent to the studios. Stairs and lifts serve the various levels, the building being fully accessible to those with reduced mobility.

Outside, the fibreglass cladding, with its vertical yellow panels that are also found in the interior, distinguishes the building. The regular pattern thus given to the facade signposts the natural airflows that ventilate the interior spaces at the same time as it creates a depth allowing the sporting activities upstairs to be glimpsed without revealing them.

Architectural design and constructional rationale

The functional organisation has a corresponding constructional rationale devised at the project design stage.  This approach was particularly necessary in this area of lower Belleville consisting of small narrow streets providing difficult access for construction equipment and materials and often decrepit and dilapidated buildings, making any work very problematic.

"The architectural assignment therefore took account of the construction operation from the outset: the major provisions of the general arrangement drawings arose out of this forward thinking regarding the execution," emphasises Patrick Berger.

Thus, the siting of the pools in the central bay, in the middle of the plot, made it possible to locate the bulk of loadings arising from this new facility at a distance from the adjoining buildings and to avoid weakening them. The choice of stainless steel pool liners - as will be seen below – helps to minimise the load on the ground, similarly to that of a steel superstructure that also made it possible to limit the amount of work on site and to free up the volume necessary for the sport and teaching pools over a span of 18.6 metres.

Finally, before being planted, the garden space served as a construction zone.

Two structural principles

The general design of the structure is essentially based on two distinct principles:

• The two infrastructure levels and the ground floor up to the upper floor of the swimming pool are built of reinforced concrete.
• The upper storeys combine a column-beam steel frame with steel and concrete composite floors.

The loads are distributed to the ground by means of steel micropiles and concrete piles driven to depths of up to 30 metres.

The connection between the metal structure of the upper storeys and the supporting concrete structure is effected at the level of the second-floor slab, above the pools. This transfer slab consists of a thick composite complex that also provides thermal insulation for the wet area. It consists of a 30-cm thick concrete slab connected by studs to the steel beamwork comprised of HEA 650 sections. The sections are reinforced on the lower flange by 6 cm thick flat bars. Tied to the 2.24-m grid of the south facade overlooking the garden, they span 18.6 m above the pools and the entrance lobby.

Based on the same grid, the beamwork of the third-floor slab is made of HEB 600 sections and HEB 400 for the terrace area as it supports a 20-cm concrete slab. The lighter structure of this final storey, using HEB 300 sections, supports the steel roof deck covered with a green roof system.

Thus, the entire steel superstructure was built with standard sections: HEB 300 in the case of the columns, selected on the basis of the loads and stresses to be withstood and transmitted in the case of the beams.

Assembled by bolting, it is entirely shotblasted and, where visible, protected by intumescent paint.

Stainless steel pools

The swimming pool area is the most innovative, with its three stainless steel pools. Desptie the fact that this construction system is very common in Germany and Austria and has been for 40 years, this is the first of this type of construction system in Paris. It has several advantages, especially significant in that they satisfy the henceforth obligatory environmental requirements. In the case of the Alfred Nakache sports centre, reducing the weight and footprint in comparison with a traditional solution was particularly beneficial.

Sustainable construction

Within the framework of the French green building standard HQE® (Haute Qualité Environnementale) procedure, particular attention was paid to the following points:

• the position and the integration of the building into its environment
• the structural decisions, which make it possible to minimise the weight of the building on the ground
• the durability of the materials, their excellent hygienic qualities, and low environmental impact
• the quality of the water, air, and hygiene, facilitated by the choice of stainless steel pools, involving: water treatment by ozonation and filtration and post-chlorination giving a chloramine level of less than 0.2 ppm
• management of energy consumption: consumption is limited due to high-performance insulation, an energy recovery system to preheat fresh air, solar panels placed on the roof to heat the pool water, and washroom water
• thermal comfort achieved by insulating the building, a heating system connected to the city’s steam network and, during very hot weather, through-ventilation (including nighttime)
• acoustic comfort achieved in the swimming pool by means of a suspended ceiling
• visual comfort: natural light is present in all of the sports studios, and views are designed to maintain an ongoing relationship between interior and exterior to achieve the best integration of the building with its environment
• during the construction operation, waste was sorted and, wherever possible, recycled, and the use of prefabrication made it possible to limit noisy work on site
• reducing the maintenance required by the premises: the choice of coatings, investigation into compatibility between the various materials, the stainless steel pools, etc. contribute to this