The Leaning Tower China

WHETHER YOU LIKE IT, HATE IT, OR ARE CONFUSED BY IT, Beijing’s China Central Television (CCTV) headquarters causes you to question your beliefs.

Buildings are not supposed to appear to be collapsing.

So, in Beijing’s seismic zone, two leaning towers linked by a 70m-long overhang 36 storeys above ground raise questions about not only what you take for granted, but also what China does.

Each of the 200m towers is tilted six degrees in opposite directions, resulting in a 13-story L-shaped overhang connecting the two.

When finished in 2009, the building will allow China Central Television, the state-run broadcaster, to expand its production from 13 channels to 200 worldwide.

The project team finished the race to clad the building before the Olympics begin this month. It was supposed to be ready for the opening ceremony, but China Central Television quickly realised that completing such a difficult project by the deadline was a pipe dream.

This isn’t about show.

The structure stands in the heart of China’s emerging central business district, dwarfing its predecessors not only in size but also in sheer arrogance.

Its aura does not convey the ‘what you see is what you get’ blandness of the nearby skyscrapers. It’s smarter than that.

CCTV appears to be running at you like a Transformer in mid-morph, but every angle reveals a new surprise.

Only upon closer inspection do you notice that the building is joined together by a nine-story base, and as you take in its entire character, you notice that it visually disassembles itself into three modest-sized buildings – the base and the two towers.

“We spent a lot of time and effort convincing ourselves, and then the Chinese authorities, that we could actually build this structure and build it economically,” says Arup director Chris Carroll.

Across the street from the construction site is Arup’s Beijing office, where Carroll has been present at key stages of the project.

He is a member of the project’s London team, which also includes Arup deputy chairman Cecil Balmond. Carroll was present at all peer review meetings in order to persuade state officials that CCTV could be built. He had to convince the authorities that CCTV was safe, despite having a Master’s degree in seismic engineering.

Despite being involved in nearly ten projects within a one-kilometer radius of its Beijing offices, including the Soho Shang Du, a 170,000m sq mixed-use development, and the China World Trade Center development, Carroll explains that CCTV has been a massive undertaking for Arup, absorbing 100 of its engineers at peak.

The one-of-a-kind design, created by the Office of Metropolitan Architecture (OMA), led by architect Rem Koolhaas, has sparked speculation about what inspired the design. The most significant of which is undoubtedly that the design somehow spells out Koolhaas’ name.

In fact, the concept is far less “out there,” being based on the evolution of the television process.

CCTV’s continuous loop ensures that all of the departments required to make television, such as managers, producers, editors, post-production teams, and lawyers, are housed in one building and communicate with one another in a single creative loop.

“The idea is to get a step change in terms of creativity,” Carroll says. “In this loop, you get all these forces racing past each other. When you look at other facilities of this type, you’ll notice that they’re very much horizontal distributions of programme, so there’ll be a production house here, a post-processing house there, and a studio somewhere else, all very disparate.”

When the CCTV system is completed, the 10,000 workers will be able to see much of the building in which they are working.

Breaking the law

The CCTV proposal came during a competition to design a new building on the 9/11 site.

Despite being concerned about the events of 9/11, Carroll claims that China would take a less emotional stance if a similar attack occurred in Beijing. “Their point of view was that that kind of incident couldn’t happen in China,” he says.

Nonetheless, in order to satisfy the peer group, Arup performed redundancy checks – removing columns and parts of the façade – to determine what damage would occur and whether it would result in a collapse.

The most difficult challenge in obtaining a building permit for CCTV was persuading Chinese authorities that the tower was structurally safe in the event of an earthquake – especially since CCTV violated the country’s prescriptive design codes.

“The way the Chinese building process works is that if your building is completely compliant, the Chinese government effectively takes liability for your building,” Carroll explains.

It took a year to persuade a state-appointed panel of university professors and eminent structural engineers that CCTV was a viable option.

Gravity’s Path

The main stability system is achieved by enclosing the building’s perimeter in a braced steel tube. As a result, the building’s skeleton is a diagonal grid of steel supports that zigzag across the entire perimeter of the structure to resist gravity and any lateral forces. A similar system is used by London’s Swiss Re tower, also known as the Gherkin.

“By combining the external tube of the entire structure, including the base, cantilever, and towers, you get a stabilising effect and spread the loads deeper into the foundations,” Carroll explains.

The 40m x 60m steel brace that covers the building is the same size as the tower’s footprint, making it a structurally efficient structure. Carroll adds that in a conventional building, if you used your core to stabilise it, which is often the central region of a skyscraper, it would be much smaller in section.

CCTV has a high degree of redundancy due to the nature of the building pattern. “You could fail any of those braces, or you could fail significant portions of the skin structure, and the load redistributes via the bracing around the damaged piece,” Carroll explains. “Any yielding, the structure can inherently redistribute loads around the point of yield.”

On December 26, 2007, the building was completed in two tower sections that were then joined to form a continuous loop. The main towers are supported by piled raft foundations. “We also bring the foundations out further than the base of the tower as a tow beneath the cantilever to further stabilise that so we distribute the forces better in the piles.”

How We Solved IT

This year marks the 20th anniversary of the collaboration between Koolhaas and Arup. In 1988, Cecil Balmond and Rem Koolhaas collaborated on their first major design, a competition entry for the Hague City Hall.

Internal Insulation

Koolhaas says that only 21st century computer power permitted CCTV to be both designed and built. Carroll adds that only five years ago it may not have been possible.

Tekla Structures software, also used for London’s Gherkin, aided the connection design and erection phases of CCTV.

Managing director Andrew Bellerby said the advances in software is giving architects more freedom with what they develop.

“I guess nowadays they are trying to out do each other,” he says. “The software is certainly helping push the boundaries – how much further they can take it I don’t know.”

Computer technology was also vital in analysing and convincing the authorities that CCTV was safe. The Arup team went into a laboratory with one of the Chinese universities and tested the large columns and braces to see what yielded first and what damage would occur.

“We made vast numbers of computer simulation models to test the structure in extreme levels of earthquake,” says Carroll. “We also built a 1:20 model of the whole building and put it on a shake table to see where the damaged occurred.”

Arup’s performance-based design approach had three objectives: no structural damage when subjected to a level one earthquake (an event likely to happen in 50 years); repairable structural damage when subjected to a level two earthquake (475 years); and severe structural damage permitted but collapse prevented when subjected to a level three earthquake (2,500 years).

“The building is designed for a 100-year lifespan,” says Carroll, “and even in that extreme event of a level three earthquake the building is designed not to collapse.”

CCTV’s ambition reflects China’s desire to become an elite superpower. In that sense, the Olympics and their attendant developments are a byproduct of its ambition.

After a brief pause, Carroll explains that China’s rise to dominance may have created an environment and opportunity that will be difficult to replicate in the near future.

“A building like [CCTV] can only really be built under a set of circumstances that I believe will only be available in China at this particular time,” he says.

A forest of 200, 250m-plus towers will be built in the business district over the next five to ten years to cement Beijing’s financial harbour.

CCTV was a once-in-a-lifetime opportunity for Carroll. “Anyone who tells you that designing the central television headquarters with Rem Koolhaas isn’t the pinnacle of their career is braver than me,” he says. “I don’t know what the next few years will bring, but being involved in a building like that is probably a once-in-a-lifetime opportunity.”

Last Updated on December 30, 2021


Author: Indra Gupta

Indra is an in-house writer with a love of Newcastle United and all things sustainable.

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