The new girder with sinusoidal openings combines aesthetic requirements with sustainable architecture: Angelina® enables large spans, planning liberties and the guarantee of an easier and more flexible conversion.

Claude Vasconi, one of the most important contemporary architects in France and ArcelorMittal have jointly developed an innovative ceiling girder system in steel which sets new standards – the AngelinaTM beam. In less than a year, a building product with a new architectural dimension has been developed from its first sketches (Fig.2) and concept to receiving the 2007 Design Prize at the Batimat in Paris.

Vasconi’s architecture is typified by the noble and clear aesthetics which are supplemented by the accuracy of the detail and strength of materials.

AngelinaTM beam: aesthetic & economical

An attractive shape, a clear geometry with large sinusoidal openings, a large support spans and the efficient use of material make the Angelina® beam one of the most particular and innovative steel products on the market, that encounter the aesthetic and economic aspects of nowadays construction.

Angelina® allows the optimisation of the headroom, the reduction in the number of girders and supports, as well as the reduction of the foundation dimensions. Therefore, Angelina® enables the steel insert weight of the roofing construction to be reduced to less than 30 kg/m². With composite flooring (e.g. Cofrastra) as a composite solution, a wonderful combination is achieved through structuring, aesthetics and construction costs.

Lightness & Flexibility

Starting from a base profile, a 1.4 up to 1.7 times larger statistical girder height is obtained through the innovative production process (Fig. 3).

This means that a larger support span can be achieved with the same weight (base profile). The production of hybrid girders with different profiles and / or various steel qualities is possible through the special manufacturing procedures and it has a particularly economic effect on the overall costs because with their material properties, the girders can be optimally adapted to the required statistical cut lengths.

A construction built with this type of beam is lighter and more transparent than usual, and this means also a full flexibility and maximization of dimensions of the space.
In this way, even rectangular ventilation ducts with large dimensions (0.7 x 0.4) can be simply and quickly assembled through the large sinusoidal openings.

The multitude of possible variations gives architects the opportunity to create flexible design possibilities open in relation to sustainable building optimisation.

A Sustainable Answer to Changing Requirements

Since the 1980’s or at least since the discussion on global warming, sustainability, ecological construction and reduction of energy consumption have become the most important issues in architecture. Therefore, the use of resource-conserving materials and procedures is of great significance.

For example, the manufacturing of hot rolled Angelina® girders shows an energy balance which fulfils the criteria of a sustainable development because the Angelina® girders at ArcelorMittal solely consist of hot rolled profiles which are manufactured from almost 100% recycled steel-scrap in the electro-oven procedure. Even the resulting rolled girder or Angelina® is 100% recyclable at any time.

Furthermore, sustainable planning and construction also requires a balanced consideration of the social and cultural effects of the building project. Apart from urban development and countryside integration, it is also functional, creative and anthropological aspects affecting people which have relevant significance.

Through the use of sustainable products – such as the Angelina® girder – ArcelorMittal is taking charge of the implementation of principles for sustainable development in man-made environment. With the Angelina® girder, ArcelorMittal has succeeded with a building product for highly aesthetic requirements that combines the elementary aims of sustainable architecture with the practical demands of the construction industry.  Aesthetics, easiness, cost effectiveness and flexibility guarantee a product with almost unlimited degrees of freedom for planning.

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