One design, two buildings: steel car parks in Toulouse

For the construction of these two identical multi-storey steel car parks at the Toulouse Metro stations Argoulets and Balma Gramont the latest technologies were applied. Fire protection, cost- efficiency and sustainability were optimized to a maximum. Steel structure, composite flooring and perforated façade cladding supplied by ArcelorMittal contribute not only to functionality but also to its architectural design.

Detailed information

In 2006, the public-transport administration of the city of Toulouse called for a design contest for two new multi-storey car parks in order to increase the capacity of parking spaces in the ground-level car parks at the metro stations Argoulets and Balma Gramont built a few years previously in the course of the extension of  the Metro line A. Two identical car parks were built on different locations although not very far from each other.

A modern, efficient steel car park

The steel solution for the structures, floors, and façades proved to be successful, as it responded to all these project requirements. It is innovative, not only in architectural aspects, but also from an engineering point of view, as it takes advantage of the new safety assurance methods in the case of fire in accordance with European regulations.

The use of steel in multi-storey car parks offers many advantages: optimum availability of spaces for users thanks to the wide spans and reduced overall dimensions of the load-bearing structures, economy and speed of execution thanks to the lightness and prefabrication of the components, and the possibility of formal choices adding an air of architectural elegance.

An "open" façade system (that is, with at least half of the external shell being air-permeable) guarantees ample natural ventilation, which is essential to safety in the event of fire in the building: recently, it has been proven that with the advanced structural design methods provided for by the Eurocodes, it is possible to guarantee structural safety in the event of fire, thus eliminating or limiting the expensive fire-protection systems of metal structures.

This is an important result of the European research programme in the scope of structural engineering, which provides for the performance of fire tests on a real scale. In France, structural fire-safety regulations were recently updated in light of the European regulations, which reinforces the logic of "provision" and "prescription", thus making it possible to build multi-storey car parks with unprotected structural steel (i.e. without intumescent paints, sprinklers, and so on), and actually opening up the door to the innovations offered by steel solutions. Nowadays, in France, one out of two car parks is built using steel because of its benefits regarding construction costs and time.

Steel structure & composite flooring

The volume of the car park is simple, in line with its functional aims and the urban surroundings. It takes the form of a parallelepiped marked by the section of its structure, made up of steel columns and beams. The whole structural framework is 15 x 10 m in plan view, with the main beams composed of rolled-steel profiles with a section 500 mm high (HEA500). The secondary beams (IPE500) have a span of 15 m and an interaxial of 3.3 m. The columns are composed of slender steel tubes with a diameter of 400 mm filled in with reinforced concrete. The wide spans make it easy for users to manoeuvre and create an open and well-lit interior.

The floors are composed of corrugated steel decking (Arval Cofraplus - ArcelorMittal Construction) cast with composite concrete and work in collaboration; the surface-finish layer of the floors is composed of an anti-slip resin. The steel structures were prefabricated in factory, galvanised for protection against corrosion, and transported to the site on a "just-in-time" basis. Both car parks contain 564 parking spaces on four storeys plus 50 bicycle spaces on the ground floor, with their own access separate to the flow of cars.

The vertical connections for pedestrians are composed of stair and lift compartments in reinforced concrete and the fire escape stairs located at distances stipulated by regulations; the pedestrian walkways are appropriately marked. Traffic inside the car park is organized in a one-way system and has been designed to make it easier to find free spaces, assisted by an electronic indicating system and dynamic space counter, and to make it easier to exit quickly.

The spiral ramps for access to the car park floors are also constructed using structural steel. The front volume of the ramps and the pedestrian access is composed of three supported cylinders, distinct from the geometric rigour of the main body.

Ventilated steel façade with a metallic spangle

The car park’s façade is composed of wave-patterned, perforated shading elements (Mascaret from the Arval range - ArcelorMittal Construction), made of Kristal® coated stel, with an aesthetic metallic surface coating with a thin layer of aluminium and zinc  guaranteeing optimum corrosion resistance.

The modular panels are supported by a secondary galvanised structure, leaving some space between façade and body of the building.

The micro perforation and waves of the cladding profile give the building a varying appearance according to the lighting conditions: whereas during the day the building appears opaque and reflects the light, at night-time it is transformed into a kind of magical lantern, rendering its outer shell almost transparent. The main front area is characterised by the sinuous progression of the cladding, while the other faces are interspersed with folding elements that open out to enrich the visual exchanges between the interior and exterior.

Project Information

  • Toulouse
  • France
  • Architects:
    Azéma Architectes, Architecte associé: Michel Turbine - Toulouse
  • 2008
  • Client:
    Tisseo SMTC
  • Engineering Office:
    Technip TPS
  • Contractor:
    Metal structure: Baudin Chateauneuf
  • Photograph:
    ©ArcelorMittal - ©Azéma Architectes