Terminal 5, Heathrow Airport
One of the major differences between the original scheme and the final design is that the site area has been significantly reduced. The original scheme took up land virtually all the way out to the M25 London orbital motorway as well as some green-belt areas for parking and external services. The public enquiry insisted that the site should be compressed into a very compact area with no call at all on green land. While in many ways this was seen as a design advantage, it none the less presented a significant logistical challenge. The compact nature of the Terminal 5 plan is striking compared to other international airports, with its constrained footprint rather than being spread out across the landscape. The site, the same size as Hyde Park but jam-packed with construction and equipment, has been described as a cross between the Battle of the Somme and a well-considered chess-game, with site safety referees with red cards hovering.
Another major change is that the rail link has been moved from below the building to outside, where it has become part of the interchange piazza. This has resulted in the elimination of the configuration found at many other terminals, in which a forecourt with a pick-up and drop-off zone dominates the front of the building. At Terminal 5, a generous, welcoming area in front of the main terminal, in effect a ‘front garden’, was seen as a crucial element of the design. In this way, passengers will not arrive at the terminal and just walk off the kerb straight into the building. The interchange at Terminal 5 gives the building a great front door and a sense of welcome and departure, with some presence and quality. The interchange piazza will be planted with large trees, have high-quality finishes and forms, and act as a transition space between the building and the car parks. It is also a multiple interchange as the rail, buses, cars and taxis all flow through the same space.
Because the roof of the terminal building is such a prominent feature of the design, an understanding of local building technology and procurement methods were fundamental to the project’s success. A roof design team was assembled to take on the task and the design was simplified from the original concept to address crucial issues of cost, buildability and flexibility. The solution consists of a tied, or bowstring, arch supported high above the concourse on inclined structural columns to keep the interior space free of columns, maximising layout flexibility and is cost-effectiveness.
At its highest point, the roof towers 37 metres (120 feet) above the ground. However aircraft operations do not allow any structures above 39 metres (128 feet), effectively ruling out the use of cranes to put the structure in place. Rather than jack the arches individually, it was decided to assemble whole sections, consisting of two structural bays and one infill section, on the airport apron before raising them into position. This means that most of the work takes place on the ground, making assembly a relatively easy and safe procedure. In addition to the structure, the roof covering, delivered to the site as 3,000 pre-assembled cassettes, is also assembled on the apron and slotted into position prior to the roof lift. In all, five lifts of three bays each and one single bay (each bay being approximately the size of a football pitch) are planned, with each bay attached to the next with secondary steelwork. In effect, the structure of Terminal 5 is assembled like a meccano set with the whole structure held together by bolts.
The roof at Terminal 5 is just one instance of the complex systems of design, manufacturing and construction processes that are integrated and executed on a heroic scale – a development made possible through the use of advanced computer technology. The gains for the project in terms of economy and efficiency – given that this is one of the largest construction projects in Europe – are enormous.
Major landscaping was undertaken on and around the site to rehabilitate the Colne Valley area which included the preservation and enhancement of two rivers on the site. The buildings are energy efficient for their type and include louvres to shade the east, west and south facades, and laminated glass to insulate against aircraft noise.
The three key passenger zones within the building are treated as major public spaces beneath the large-span arched roof.
The client, design team and contractor teams have been co-located on site since the inception of the project to facilitate the high degree of collaboration necessary for the resolution of a project as complex as T5.
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