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Gallieni High School: sustainable construction with steel at its best
Flattened seven years ago by the explosion of the AZF chemical works, the former Gallieni high school was completely rebuilt and re-opened to students at the start of the 2008 school year. An outstanding achievement not only for its size but also for its symbolism, this project adopted a sustainable construction approach from the outset. The advantages of steel present in the structure, the floors and the roof have solved many technical, environmental and aesthetic issues faced by the project.
The advantages of steel
Extensively restored, the Gallieni high school in Toulouse offers a fine example of steel architecture, in an industrial philosophy, designed in accordance with an environmental approach.
Steel was chosen as the main construction material for the following reasons:
- Prefabrication and clean construction site
- Large spans and ease of use
- Thermal, acoustic and visual comfort
- Material savings and cost control
The use of steel construction firstly enabled a “clean” dry and short construction operation by using prefabrication and thus limiting any nuisance.
The advantages of steel were employed to achieve a building that is efficient in operation and provides appreciable benefits in service: the long spans in the workshops provide large volumes, the openwork structural elements make the perception of space more fluid, the generously glazed façades give priority to natural light, articulated sun breaker systems adjust to the degree of penetration of solar radiation, the lower face of the Cofradal 200 floors serves directly as a ceiling…
The choice of assembled rather than glued or sealed elements fulfils the requirement for ease of recycling at the end of the building’s life.
The architectural approach adopted and construction methods employed represent a compelling message following the disaster suffered by this part of Toulouse.
Located on the outskirts of Toulouse, the Gallieni high school was almost entirely flattened as a result of the explosion at the AZF plant in September 2001. A competition was organised for the rehabilitation and refurbishment of this general, technological and vocational high school dedicated to the transport and automotive engineering trades. It was the project proposing the most extensive renovation that won, giving the opportunity to make it a model from an environmental point of view and resulting in a state-of-the-art educational establishment that is both “compact and contemporary”.
The new school’s various buildings are spread over a vast 11-hectare campus that includes a landscaped park of 21,400 m² that is open to the neighbourhood. This campus, located close to Toulouse-Blagnac airport, is bordered to the west by the ring road and to the east by the river Garonne. The educational premises, including the restaurant and the Centre for Documentation and Information (CDI) are concentrated in the eastern portion of the plot, while the 14 staff accommodation units are situated alongside the road. The boarding accommodation for more than three hundred students is installed in the former Françoise high school, fully restored and converted. In total this represents 41,000 m² of gross floor area of which 15,000 m² are workshops.
Steel architecture at the service of the environment
Planned to accommodate more than 1400 students, the new high school was designed to fulfil the requirements of "high environmental quality” within a sustainable development strategy. Its steel structure contributes in particular to this objective, both in terms of the manufacture of modules and conduct of the construction operation as well as the operation of the building when in use.
In view of the school’s location, special attention was paid to acoustic and thermal comfort. Indeed, the proximity of the airport and the associated noise nuisance prompted the architects to consider how to minimise them. The heat and light inputs were carefully studied so as to be of an appreciable level and quality throughout the year. The orientation of the building, the organisation of the rooms and workshops, as well as the treatment of the facades and roofs reflect this quest. Finally, the use of renewable energy and rainwater recovery also contributes to significantly reducing consumption of fossil fuels and water.
The premises consist of two parts which correspond to the education offered – technical education and general education - organised on each side of a north-south circulation; they are complemented by a so-called "track" building situated alongside the test tracks, close to the river.
This 300-metre long circulation constitutes the backbone of the high school. On one side it serves the workshops and on the other the educational buildings, arranged in a comb formation, as well as the restaurant and the CDI.
The choice of a steel frame enables large spans in order to obtain uninterrupted volumes beneath the roof. These volumes are naturally and evenly illuminated through a system of sawtooth roofs – four to six depending on the workshops – whose north-facing upper parts are glazed. Peripheral mezzanines accommodate classrooms and studios.
From the outside, the workshops have the appearance of a series of bays, covered with panels made of metallic coated steel, enclosed on the southern gable and fully glazed on the north face overlooking a garden. Four gardens are interposed between the five workshops.
The structure of the workshops is of the column-beam type, combined with lightweight facades, glazed on the northern face and steel panels on the southern face, and a concrete wall along the main circulation. The steel roof structure consists of inclined lattice trusses with a 42-metre span and 4 metres in height. Each truss node supports a dual-curvature purlin with a 9-metre span. In an intentionally industrial approach, the entire structure is left visible. The uniformly light-filled ambience is similar to that of artists’ studios.
The high school’s principal circulation, it is also a key component of the project. It comprises three storeys to serve the workshops on one side and the classrooms on the other.
It is a link and a venue for functional and visual interaction. It is punctuated by the "windows" looking onto the patio gardens to the east and the climatic gardens to the west.
The glass roof that covers its entire length is equipped with 2000 m² of photovoltaic panels, which will produce the equivalent of the high school’s annual electricity consumption. It is supported by a series of steel half-portals with a span of 8.20 metres, made from IPE 600 beams with rectangular web cut-outs in order to lighten this structure both physically and visually.
A full-height strip of greenery, planted with bamboos, borders the workshops and reveals the three circulation levels. On the first floor, the circulation, resembling a footbridge, rests on one side on a row of circular columns and, on the other, is suspended from the concrete wall of the workshops by means of inclined steel tubes. On the second floor, the circulation is treated as a passageway and provides access to the general education buildings.
The vertical circulations – stairs, ramps, lifts - connect the various levels.
The general education buildings and administrative offices
Five in number, they consist of three floors (ground level plus two further storeys) and are organised around "climatic gardens".
They are all of the same design, with a steel column-beam structure and lightweight Cofradal 200 floors (steel decks, insulation and concrete slab). The structure is left exposed, the utilities are visible, the lower surface of the floors serves as the ceiling, the lighting is inset. The partition walls consist of Elco blocks assembled dry. There is no sandwich unit but assembled units that will be easier to recycle at end of life.
The gardens, covered by a glass roof, provide breathing spaces and enable control of the climate within the rooms. The glass roof rests principally on a 3.5 mm thick plate box girder rigidified by a lattice beam, with a 15-metre span and 1.4 metres in height. It contains a gutter in the upper part which enables rainwater recovery and provides access for maintenance personnel. Shaped like an asymmetrical V, it serves as a support for the two secondary roofing structures above the gardens: the upper one for the glazed surface, and the lower one for a lattice sunbreaker.
Vasconi Associés Architectes
Conseil régional Midi-Pyrénées
- Engineering Firm:
Iosis Sud-ouest and Patmo/Franck Boutté
Serin & fils and Acte 2 paysage
©Iosis, ©Vasconi and ©P.Engel