Madrid Barajas Airport
The construction of the Barajas Airport terminal has been undertaken in three constructional layers – the basement which drops to as much as 20 metres (66 feet) below ground in some places, the three storey concrete frame above ground, and the steel-framed roof. The concrete work is in-situ, although special attention has been focused on areas where the concrete will be visible, such as the edge strips to the canyons in which steel shuttering has been used. In a bid to limit the height of the building, post-tensioned concrete beams restrict the depth of the beams to only 90 centimetres (three feet). The beams were cast in lengths of 72 metres (236 feet), with concrete planks used to span between them to create the 18 by 9 metre (60 by 30 foot) grid.
Above, the concrete tree trunks on the top floor provide fixed base points for setting out the roof steelwork. The structural system for the roof works outwards from the tree trunks where four inclined branches prop a pair of double-S modules. In this way, each pair of tubes plus the roof steel stabilise the roof structure in both directions.
The roof then passes over the cladding line at the edges of the building, emphasising the roof rather than the facade. To further reduce the visual impact of the facade, shading is not introduced at the cladding line but is hung from the roof overhang which is propped with elegant Y-shaped props at the ends of each module.
The facade structure is in the form of cable ‘kipper’ trusses at nine metre (30 feet) centres. A pair of cables begin at a common point at ground level, one arcing in and one out, held apart by compression struts that also support the horizontal glazing mullions. As the cables approach the roof they come back together, held by a V-bracket, making a fish outline, hence the name ‘kipper’ truss. A ‘jacking’ system was used between the roof and terminal floor during erection which when released ensures that adequate permanent tension was introduced in the cable trusses.
While no specific environmental criteria were stipulated in the brief, the design team set out to maximise natural daylight to all passenger areas and reduce dependence on artificial light, while providing views out and reducing solar gain with extensive external shading.
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