Mexico needs a new international airport. Its designers have come up with a radical approach.
Should all go according to plan, 2014 will be remembered by Mexicans as the year that a new era began for their country.
In a world where people are virtually and physically interconnected by data travelling at the speed of light and aircraft travelling at the speed of jets, airports have inevitably become a sort of 'presentation card' they're the first thing that visitors see when they arrive in a new country.
And first impressions count, judging by the number of governments investing billions of dollars into designing and building international airports that not only expand capacity but also look stunning.
Last September, as Mexico's President Enrique Pe'a Nieto was unveiling plans for a new airport in Mexico City, it became evident that the announced infrastructure project fell within this category. How could it not when it was being described as "the world's most futuristic and sustainable airport"?
Anticipating that a project of such magnitude would be inconceivable without the collaboration of international experts, the government set a key condition for entering the competition to design the new airport: while Mexican architects were to be involved in each proposed design, they had to partner with an international firm with proven experience of large-scale airport construction.
Celebrated British architect Lord Norman Foster was the 'foreign and qualified' ingredient in the winning team. As for the local flavour, it was provided by a young Mexican architect Fernando Romero, known in his native country for two facts: he is the son-in-'law of the world's richest man (Mexican telecoms billionaire Carlos Slim), and he designed the beautiful Soumaya Museum (owned by the Carlos Slim Foundation).
They have been working closely with Netherlands Airport Consultants (NACO), a renowned planning firm that has been involved in the construction of more than 500 international airports.
Challenging soil conditions
In principle, the brief from the government was simple. It called for a brand new international airport with two terminals. To be located on federal land adjacent to the existing Aeropuerto Internacional de la Ciudad de M'xico (AICM), the new airport needed to be large enough to overcome the capacity crunch affecting the current facility, which opened in 1931.
The basic specifications asked for a sustainable building which could be built on budget and be mindful of the peculiar characteristics of the designated site.
Once Foster and Romero went to the drawing board, they concluded that the brief was not as simple. In fact, they thought it was contradictory, and the government later proved it agreed by selecting their entry.
The contradiction in the brief was that while on the one hand it asked that the special characteristics of the site (unstable soil) be acknowledged by the design, on the other hand it specified the construction of two different terminals linked by a rail service (which is never recommended in unstable soil because tracks can bend/move, and tunnels are difficult to build). The government ended up selecting an entry that, unlike its original brief, proposed a single terminal instead of two, making the need for a rail link redundant.
Like the rest of Mexico City, the AICM is literally sinking - as much as 10cm a year in the case of its runways. In order to keep an even runway surface, airport operator ASA is forced to remove the rubber left by landing airplanes before adding a new layer of asphalt every six months.
Fortunately, technology has come a long way and the new airport will be able to avoid similar problems. Up to six runways are planned - three to be built from 2015 to 2020 and three for later completion. By applying a pile-based deep foundation technique combined with the use of light materials such as polystyrene for the 4km-long, concrete-topped embankments, engineers are confident that they can overcome the 'sinking runways' issue.
But while runways are an obvious must in airport infrastructure, railways aren't. Instead of proposing an alternative means of transport to move passengers from one terminal to the other, Romero and Foster had a radical idea. They set out to eliminate not only the train but also one of the terminals.
What emerged was a spectacular six million square feet (560,000m2) single terminal featuring one-third the mass and three times the span (170 metres at its maximum) of a typical airport. The building will initially be able to handle 50 million passengers a > < year - a 59 per cent capacity improvement over the current hub. When the six runways are operational, an expansion plan (based on projected air transportation traffic demand up to the year 2062) will see the same gigantic terminal able to'accommodate 120 million passengers a year.
Needless to say, the same difficult soil conditions that guided runway design were a key consideration for the terminal. "The site is located in an area that used to be a shallow lake," Lord Foster explains. "As a result, the soil has a high water content and has little capacity to support large loads. In addition, the area is seismic, and the effects of ground movement are magnified by the soil type in the area. Finally, the site is subject to substantial settlement over time, as the groundwater is extracted to provide the water supply for Mexico City."
Above all, the building needed to be very light. In a move that the architects and engineers claim will be a first in airport construction, they decided that the whole terminal would be enclosed within a continuous, lightweight gridshell that embraces the inner layers of the building and seamlessly acts as both its walls and roof. Combining both skin and structure in a single system, the shell stretches from the fixed boarding bridges to the top of the roof.
Lord Foster describes it as a series of interlocking shell structures that resist their loads through in-plane forces - rather than bending - and are, as a consequence, extremely lightweight. "This roof is constructed as a steel space frame, which lands at individual points," he says. "It is inherently flexible, which makes it more forgiving of ground movement than a more rigidly supported structure. The structural steel floor system is also lighter than a pure reinforced concrete alternative."
This thin membrane brings additional benefits: it does not require falsework or scaffolding (a prefabricated system is used to assemble the components at ground level), it can be erected much faster and more economically, it requires fewer materials and less energy than a cluster of buildings, and it produces incredibly spacious interiors.
And there's more. Think of any existing airport in the world. Think of the last one you used. Did you get to see any of the countless generators, air-conditioning exhaust vents or other pieces of heavy machinery necessary for the normal operation of the building? Chances are you didn't, unless you spotted them from the air while taking off or landing, as this type of equipment is usually located on the roof.
At the new Mexico City Airport, everything will be hidden beneath the building. It's a decision with added benefits. The thin roof/ceiling can adopt irregular shapes for aesthetically exciting spaces. Just as relevant, the roof/ceiling can now be transparent, allowing for natural light, great views and harvesting of solar energy.
As green as it gets
Environmental research groups and specialist engineers are advising project managers on their quest to obtain the Platinum LEED (Leadership in Energy and Environmental Design) certification.
The high-tech membrane - which will be built entirely in Mexico using local materials - will be used to collect rainwater to be stored for later use. It will also provide shade, redirect daylight and help meet stringent acoustic and thermal specifications.
The building will take advantage of the dry, temperate Mexican climate by redistributing fresh air throughout the terminal using a special displacement ventilation system.
"For nearly half of the year, we can work with the air-to-ambient temperature," Lord Foster explains. "For the rest of the year, minimum heating and cooling [will be required]. A mild air displacement system will be combined with other techniques, such as distributing air through pipes in slabs, insulation and harvesting energy.
"We've taken a holistic approach to the design," he says. "We show a model that will be an inspiration for future airports, which will be efficient, operationally flexible and, above all, beautiful and a great experience."
The large-span, lightweight, fast-to-build, inexpensive, environmentally friendly, single-building terminal may evolve into the template that other countries and cities will want for their very own presentation cards. *