ArcelorMittal Europe provided steel for the construction of the new NATO headquarters in Brussels. The building was officially inaugurated on May 25, 2017 in the presence of NATO's heads of state.

A huge complex for 4,000 employees

Designed to resemble interlocking fingers, NATO's new headquarters symbolizes unity and cooperation.

The building includes:

• offices
• outdoor and indoor sports facilities
• a logistics area
• a conference centre with a capacity of 2,251 seats
• a restaurant for 600 people
• a car park for 3,331 vehicles

In total, this 254,000 m² site will welcome about 4,000 employees and 500 visitors per day.

Steel for the structure and the floors

ArcelorMittal, through the centres in Orense (Galicia) and Getafe, both within Distribution Iberia, supplied hot rolled steel sections and merchant bars for the structure of this huge construction project. ArcelorMittal Construction was another contributor, supplying flooring system Cofraplus® 77 and roof cladding Hacierco® 54 S and 74 S.

The construction of the new NATO headquarters started in June 2012 and was completed in 2016.

Since May 2017, around 260 NATO staff and contractors moved to work permanently in the new building, the bulk of the move is due to start later this year.

Text: ArcelorMittal Europe Communication
Pictures: ©SOM+ASSAR

For the Euro 2016 celebrated in France, the city of Bordeaux received a new stadium designed by the renowned Swiss architectural practice Herzog & de Meuron. ArcelorMittal supplied steel sections, tubes, cladding sheets and composite flooring profiles for this new building.

The new Bordeaux stadium is entirely made of steel and was completed in 2015. It is the new home of the Bordeaux Football Club Girondins and also one of the France's host stadiums for the Euro 2016.

For its structure, ArcelorMittal supplied 4.200 tonnes of steel sections in grades S275 and S355J0  and 500 tonnes of steel tubes, produced in the company's mills in Spain and Luxembourg. Furthermore, ArcelorMittal Construction France produced 70.000 m2 of Frequence undulating cladding sheets for the interiour cladding (partly with acoustic perforation) and 20.000 m2 of composite flooring profiles  (Cofraplus 60) for the new stadium.

The stadium's design

The Swiss architects Herzog & de Meuron are the authors of the new stadium's design. It is characterized by its light and open structure, covered with a square roof that is supported by slender, white columns. These columns resemble a forest, brought to life by the movements of the crowd.

Architecturally, it consists of three elements: the bowl resting on a plinth and the pitch, the concourse as a transitional element between the inside and the outer surroundings and its overall appearance.

The stadium provides seating for around 42.000 spectators, with optimal visibility for all thanks to  its geometry and organic shape. The bowl consists of two superposed tiers divided into four sectors and protected from the elements by the large rectangular roof.

The bowl rests on a compact base that integrates all the programmatic functions into a uniform and symmetrical volume. These include VIP areas, salons distributed east and west, and media areas adjacent to the spaces dedicated to the players.

The roof's structure is not visible from the underside in order to avoid possible distractions of the spectators. Its homogeneous surface guides the visitors' view towards the pitch.

The smooth flow of the spectators as well as easy orientation is guaranteed thanks to the simplicity and the pure lines of the architecture of the bowl and its base.

The new Geric supermarket and car park structure are really innovative structures for the French market. The construction techniques used for this project are applying the last innovations in term of structural calculation and fire engineering.

The structure of the commercial area will be the first reference of Angelina® beams calculated partially protected taking into account the membrane action of composite structures in case of fire.

The car park will be the first car park in France that will be built using unprotected ArcelorMittal Cellular Beams.

Another particularity of this project is that the ground floor will be devoted to the shopping centre and the 3 upper floors will be an open car park (first realization of this type of structure in France).

Description of the building

The owners of the commercial centre Geric decided to extend the commercial part of their building, but it was impossible for them to extend the size of their property. It means that this extension must be done taking the actual surface of their existing open air car park surface. As the number of parking places was already a problem, the new concept must not decrease the total amount of places.

It has been decided to add, on the top of the commercial extension, a multi storey open car park. So in the end, as this multi storey car park will have 3 floor levels, the final amount of parking places will be increased compared to the previous layout of the commercial centre.

The structure is composed of 4 floors with an approximate dimension of 70m x 70m.

Choice of the structural elements

The owners, the architects and the engineering office had in mind to optimise the structural system in order to achieve the most cost effective and environmentally friendly structure. Their choice was directly oriented on steel and composite construction.

For the slab between the ground floor and the car park, the architects have chosen Angelina® beams to have large openings in order to pass all the ventilation and piping system into the openings (Fig. 2).

For the car park levels, cellular beams were used in order to optimise the structural system but also for architectural reasons.

As the vertical part of the beam contains a lot of openings, the level of the ceiling will be perceived by the visitor as the level of the slab and not the level of the lower flange of the beam, so for the “human brain”, the beams will become transparent. It means that the sensation of freedom and safety will be highlighted.

For the durability, it was decided to galvanise the structure that will remain visible and not protected against fire.

For the slabs, the composite flooring system Cofraplus 60 was used. 

Fire engineering innovation

The French procedure for the calculation of unprotected car park structure has been followed. The three usual French fire scenarios were taken into account in the calculation (Fig. 4):

- 4 cars around a central column
- 7 cars in line at the corner of the car park
- 1 car in the circulation area

The innovation is that the structural calculation has been made for cellular beams using the models developed in the recent RFCS project FICEB+. In the past, it was not possible to perform such calculation taking into account the specificities of the cellular beams.

For the commercial area, the new calculation technique taking into account the membrane action of partially composite slab in case of fire has been used for the first time on the French market. This calculation technique is based on diverse research projects and has been implemented into the user-friendly software MACS+ ( available for free download on www.arcelormittal.com/sections or in Constructalia Software section). This technique allows saving about 50% of the fire protection, applying it only where it is really  necessary (Fig. 5).

Conclusion

This project will become a reference for unprotected open car park and shopping centre due to the global optimisation of the structural system and architecture. This new approach was only possible thanks to diverse R&D projects led by ArcelorMittal (Fire in Car Park, FRACOF, RFCS FICEB+ and RFCS MACS+).

Text: Olivier Vassart & L.G.Cajot, ArcelorMittal Long Carbon Europe