Fluid dynamics


Aiming to set a new standard for air transport, the dramatic curves of ZHA’s first airport are as much the result of a need to provide maximum throughput, as aesthetic aspiration. The project’s lead architect tells Jack Wooler how the team explored the evolving role of architecture on the project

The new terminal for China’s capital, Beijing Daxing International Airport – designed by Zaha Hadid Architects (ZHA) in collaboration with French planners ADPI is a triumph of highly functional design which demonstrates the value of architectural involvement throughout major infrastructure projects.

Despite the striking forms achieved by the practice working with Buro Happold and a range of other consultant firms, the design was above all else, a product of the Government’s desire to ‘process’ passengers as quickly as possible, in the smallest footprint practicable.

This high throughput requirement, briefed to ZHA via the Chinese Government’s Local Design Institute, led to the practice producing a relatively compact, radial configuration. This would mean passengers on foot could reach the farthest boarding gate in less than eight minutes from the central terminal area.

Opening in 2019 after less than five years of construction, the terminal (which forms part of a £50bn airport project) is intended to be seen as an example of sustainable, functional design, and to serve as proof of concept that when architects and designers are involved throughout an entire project, good design means not only beautiful aesthetics, but dramatic savings of time and money for clients and users alike.

Flowing forms
Having been nicknamed ‘the starfish,’ which it resembles viewed in plan, the airport consists of a central hub, where four stacked levels provide the typical terminal functions of a modern airport, and five piers extend to the apron, and surrounding taxiways beyond. Three of the piers have aircraft stands on both sides, the remaining two – those closest to the main entrance which faces a major road, have stands only on their rear sides.

A further covered ‘leg’ extends northwards landside of the hub, providing circulation to the car park, rail station and a landscaped public realm on the other side of the major road abutting the airport’s frontage.

Covering the entire structure is a vaulted ‘shell-action’ roof with the long sweeping curves and flowing organic shapes that are a hallmark of ZHA projects.

Inside, huge sculptural columns (eight in total, with six arranged in a circle and two closer to the entrance) hold up the space frame structure and bring natural light in, thanks to skylights forming the roof of their hollow, C-shaped forms. These are complemented by linear skylights running from the central dome along the piers, augmenting the daylighting levels and providing an intuitive, simple aid to navigation throughout the building, guiding passengers to and from the central courtyard.

Intended to echo traditional Chinese architecture – which often has interconnected spaces organised around a central courtyard – the terminal’s design offers generous public spaces created by the roof’s huge structural spans – up to 100 metres – providing a high degree of flexibility for any future internal reconfiguration.

Furthermore, by separating and stacking each subset of the airport’s functions vertically – with departures, international and domestic arrivals each placed on their own floor – convenience for passengers and flexibility in operations has been maximised. In addition, the overall central processor footprint has been kept as compact as possible as a result.

Thanks to this design, as well as the integration of a transportation hub in the basement levels, Beijing Daxing has reportedly saved 1.6 million hours for nearly 30 million passengers every year since opening, compared with previous provision.

The tale grew in the telling
Taking things back to the very beginning, however, to explain how the concept became reality Cristiano Ceccato uses the adage, “the tale grew in the telling.”

The spark of the project was first ignited through the exponential growth of aircraft usage in China, he says, particularly around Beijing.

The existing airport in Beijing hosted over 100 million travellers last year, believed to only be surpassed globally by Hartsfield-Jackson Airport in Georgia, US. Because of air traffic and congestion in the skies, however, there was only so much throughput available in the existing airport, “so it made sense to start from scratch.”

While these embers burned among the Chinese air transport authorities, ZHA was already busy working on other developments in the centre of Beijing.

The Government was reportedly impressed, and asked the practice if it would participate in the design shortlist for a new Beijing airport.

With part of Ceccato’s personal remit being to expand ZHA into other sectors it hadn’t yet established itself in, he says the practice pulled out all the stops to win the project, and gain a foothold in the aviation space.

The team saw it not just as a chance to contribute to a “new national gateway,” he says, and thus attain a high profile in the sector, they also had a strong affinity with the project due to the practice’s highly international nature, and therefore familiarity for regular global air travel, meaning they knew the issues to resolve for passengers.

“Air travel is a unifying and democratising experience, one that all at ZHA have a connection to,” says the architect. “Unless you’re using a private jet, everyone who travels in this manner goes through the airport together – and we wanted to change this experience for the better.”

Zaha herself was intimately involved for the same reasons, he tells me:

“She really cared about this project – when we entered the competition, she personally came to Beijing and presented it herself, with all its technicalities and functionality. It really is one of her legacy works.”

The client was impressed with her efforts, and with a masterplan from Netherlands Airport Consultants (NACO) already commissioned the previous year before, the practice was asked to merge with another competitor, French team ADPI, and produce a full design submission. With ZHA leading the architectural design integrating ADPI’s planning principles, the partnership would work alongside the Chinese Local Design Institutes (BIAD and CACC) to realise the project’s aims.

ZHA, from this point on, was involved at different stages of the design process, working on the interior fit out as well as the exterior, retail planning and other facets of the project, through a series of different agreements.

Ceccato believes this deep partnership, with the architects being involved essentially from the ground up, helped to create a “truly unified” vision with what he says was a “very generous and visionary” client.

A clean slate
The client had acquired a large, empty greenfield site in Daxing District, south of Beijing, for the project, providing a “clean slate,” says the architect.

Unlike at Beijing’s existing main airport – and most urban infrastructure developments – they were not overly restricted by space, though it remained a goal for the project design to remain compact for ease of passenger navigation and efficient aircraft operations.

As a result of the compact nature of the terminal, instead of designing something long and thin to fit alongside the necessarily lengthy strip of land needed for runways, here the team could design a system of branching runways from a central hub of taxiways. This was the pragmatic key to forming the splayed “hand”-like shape of the building, which Ceccato prefers to ‘starfish,’ – having five wide-spaced ‘fingers.’

“We came upon this hand shape very intentionally,” says Ceccato. “The way you start looking at the morphology of a terminal is dominated by runway spacing; the greater surface area you have between the ‘fingers,’ the more aircraft you can park.”

With more aircraft able to park relatively close to the centre of the terminal without excessively long piers, passenger walking time across the building is minimal. This eliminates the need for automated trains to each gate, an idea the client was particularly keen on.

Such transport is expensive to build, to maintain, and, “most importantly,” says Ceccato, “it becomes the weakest link in the chain.”

And, past removing the need for such transports, the hand shape enabled the team to improve the airport experience in the most appreciated way possible – by increasing the speed of user navigation.

Stacked functions
In order to further increase the speed of navigation, it was vital that the airport’s many functions be arranged carefully.

As such, instead of placing the airport’s functions on a horizontal plane as in many airports, at Beijing Daxing they are stacked on top of each other, with vertical connectivity where necessary.

The uppermost Level 4 is the conventional departure level, including the check-in island and bag drop off. Level 3 is a higher throughput departure level from which frequent and domestic fliers can pass through security faster using smart, ‘self-processing’ gates with digital boarding pass technology. Level 2 is for domestic arrivals, Level 1 for international arrivals, and below that is a basement level for regional bus, taxi and rail transport entrances, and a further level below with the railway station and platforms.

Due to the stacked approach, “functions all come together as a layer cake, speed around the building is increased, and the walking distance becomes much less,” explains Ceccato.

Tempered & tailored
The project is the largest single building the practice has ever taken on before (and could be for some time), in a location of climatic extremes – Beijing’s continental climate going from -20 degrees in the winter to 40 degrees in the summer.

For these reasons alone, realising the team’s design aims was no easy task. While ZHA had already built several projects in China and “knew how Chinese contracting worked,” the architect says there were many challenges working in this location.

Though working so closely with the client proved beneficial in the long run, Ceccato says it proved difficult to meet the speed of programme they desired, to navigate national politics, and to ensure continued authorship and design fidelity throughout the project.

“In any country, while the work needs to have a hallmark and identification of your practice, you must always temper and tailor your project to the capabilities and desires of that location,” notes the architect, explaining the methodology used to address these challenges.

First, a risk management procedure was undertaken to identify buildability with the technological capabilities and budget that would be available, as well as produce a realistic project time frame “on the assumption that the entire shell and core would be procured on the Chinese construction market,” says Ceccato.

Then, the entire building was designed and modelled in 3D, starting with physical study models of different court areas and buildings, and eventually moving to full BIM construction models by the local partners which could be directly executed by contractors.

Once completed, this allowed every contractor, all the way down to earth movement simulations for groundworks, to work together off a single model, ensuring their “unified vision” was executed as designed, and allowing the project to be constructed at pace.

To achieve the project goals, it was necessary to prioritise use of materials most readily available to the team – largely concrete and steel.

The roof is perhaps the most impressive and challenging aspect of the design and construction, specified as a large scale steel frame built out of “cannon ball style” welded spheres.

Covering over 350,000 m2, this large-span structure is a complex hyperboloid steel grid containing more than 170,000 steel members, and supported by the C-shaped columns which seamlessly connect with the roof curvature.

Refining the design in conjunction with Buro Happold’s structural engineers, the team studied the structural configuration, loading, vertical support system reactions, and the deflection and displacement, in painstaking detail. In total, 38 different cross section sizes were eventually employed in the superstructure.

Sustainable example
Amplifying the pressure on this high-profile project still further, Ceccato says the client wanted to use the airport in part as a “showcase example of China’s achievements in sustainability.”

As such, the project had to be designed and built to the China 3 Star environmental rating, which is the highest possible sustainability accreditation in China.

To enact this, PVs are installed on the airport’s roof to provide a minimum capacity of at least 10 MW, and centralised heating with waste heat recovery is supported by a composite ground-source heat pump system incorporating a concentrated energy supply area of nearly 2.5 million square metres.

Complementing this, the airport also utilises a rainwater collection and a water management system that employs the natural storage, natural permeation and natural purification of up to 2.8 million cubic metres of water in new wetlands, lakes and streams. This not only prevents flooding, but also counters the summer ‘heat island’ effect on the local microclimate.

In addition to these added measures, the terminal’s design in itself benefits sustainability, by the “simple fact it is walkable,” says its lead architect. Efficient aircraft operations and reduced taxi times further contribute by reducing the amount of time planes consume fuel on the ground.

“In this manner, the project truly lives up to our and the Government’s ambitions to set an example,” says Ceccato. “Our practice is very committed to environmental performance and safeguarding the environment, so we are very pleased that the completed project has been performing as desired.”

Finished product
Despite the complexities and demanding goals, after only four years, the team landed a successful result in Daxing.

The airport opened on 25 September 2019, six days before the 70th anniversary of the People’s Republic of China, in a ceremony attended by Chinese president Xi Jinping.

Now in full operation, the project is expected to host 72 million passengers a year by 2025 with an additional satellite pier. It has been widely praised since its inception for its functional and practical design, and is deemed likely to set a benchmark for airports worldwide.

Ceccato fondly remembers the fact that following the opening ceremony, British Airways were the first international airline to fly into the new terminal. This memory has no doubt gained some poignancy given ongoing restrictions on air travel.

“The somewhat intentional symbolic connection with the project’s British architects made the client very happy, as did the entire finished product,” he says. “Everyone was thrilled; the project had been a huge success.”

Architecture in collaboration
Looking back on this success, the architect believes the key was a deep collaboration across teams, plus a holistic role for architects throughout the project.

“It’s important to remember that the role of architecture has evolved,” explains Ceccato. “Architects may sometimes do some planning and their bit of a contract and move on, and if they’re lucky, that might result in something that simply looks nice – but I don’t think this is good enough.”

Instead, he proposes, by working tightly together with the client from start to finish, as was the case at Beijing Daxing, architecture can play a major role in “functionality and perception” also.

“Rather than only looking at what you’re contracted for,” he continues, “working in this way encourages you to take on a wider social contract and really help change the place you’re creating for the better.”

“If that gets remembered, as it was here,” Ceccato concludes, “architecture can go so much further than aesthetics.”