One of OMA’s largest ever projects and first major in China, the CCTV Headquarters aim to revive as ‘loop’ skyscrapers which took about 10 years in construction in accommodating Offices, Production Facilities, TV Studios, and other technical services. CCTV Tower defines the Use of Headquarters and Cultural Centre. The ultimatum was to reach the height as it not only serves the purpose of a building that would contain the entire television making process but a landmark for the capital city of Beijing.
Location: Beijing, China
Architect: OMA Architects/ Rem Koolhaas
Engineer: Arup
Area: 437,000 m²
Completion Date: May 16, 2012
Floor Count: 51
Height: 234 m (768ft)
In 2002, when CCTV broadened its scope from 18 to 200 channels and an international medium to expand its network, a much-needed prototype building was required to accommodate the growing business. OMA’s proposal included a primary structure comprised of a continuous structural tube of columns, beams, and braces around the entire skin of the building. The CCTV Tower primarily combines administration and offices, news and broadcasting, program production and services- all in one ‘loop’ of four interconnected elements of the building- The nine-storey base, the two leaning towers (6° each), and nine to 13-storey ‘Overhang’, suspended 36 stories in the air.
The CCTV’s continuous loop aims to possess a truly 3 Dimensional experience. The common base serves the purpose of the Production Studio platform while each tower is serving the editing area and offices in one and news broadcasting in the other. The cantilever bridge is for Administration, the Overhang. This innovative structure is a result of the collaboration between European and Chinese engineers to achieve the breathtaking form. While observing the facade of the structure, a web of triangulated steel tubes- diagrids that rather than forming a regular diamond pattern, form a more complex geometry which is relatively asymmetrical. The spots with more stress can be identified with denser ‘diagrids’ and lesser stress would ultimately result in loose diagrids.
The self-supporting hybrid facade structure features a high-performance glass structure with a sun-shading of 70% open creating soft silver-grey color on the facade a subtle look in Beijing’s skyline. The 10,000 square meters main lobby is an atrium (Tower 1) stretching three floors underground and three floors above the ground. This area is also connected to Beijing’s subway line and also acts as departure and arrival hubs for almost 10,000 CCTV workers. Connected to the main lobby are 12 studios, performing the main function of the building- TV making. Restaurants and Cafe on the cantilevered connection look out to the spectacular views of the city. Observatory stands at 162.9 meters (534 ft). Tower 2 houses the hotel, visitor center, a large public theatre, and conference facilities & exhibition for 1,500 people.
The engineers had to face tremendous problems and challenges during the design of the CCTV Tower. The structure would attain instability due to its building form: the continuous loop, sloping tower, and cantilever overhung adding further complexity to the structure. Beijing is considered to be in the seismic zone which accounts for the instability in the site and thus resulting in redistributing load through the “pile cap” raft to engage the batteries enough to provide adequate strength and stiffness. The analysis would be repeated until the results were combined and all batteries were within allowable capacities. The hundreds of these tests and analyses resulted in a design of raft reinforcement. Shallow subsoil conditions and large underground water levels account for problems caused which the engineers found a solution to in their pile raft design.
- Total settlement estimated as less than 100 mm
- Differential settlement kept to 1:500
- Piles are the 1.2-meter diameter and 52 meters long
- Piled Raft is up to 7.5 meters thick and has a footprint greater than the towers
The diagrids frame consists of major layers on its facade which are sandwiched together to form a tightly enclosed structure. The first main layer constitutes the steel structure with reinforcement in a diamond form acting as a load-bearing element. An additional orthogonal steel structure was then made to support the existing structure; another layer of steel structure with reinforcements was then all made to create a close pack structure. To top it all, fine glazing and asymmetrical cladding would then conclude the structure.
Load transfer is primarily through the diagrids structure meanwhile lesser internal columns account for more interior space. Rings help to resist the buckling loads transforming the whole system into one big continuous tube. Due to this structure design, lesser material is used accounting for a 20% reduction in steel usage as compared to traditional steel design. Skyscraper structure failure has been minimized by this diagrids construction and better ability to distribute the load than a moment frame meaning failure of one portion wouldn’t result in a failure of the whole building.
The basement of the CCTV Tower serves four purposes: Water Storage, Air Exchange, Electrical, and Parking. This three-storey basement with retaining walls and with the help of piled raft resists the upward force of the water pressure that is created around the site. CCTV Headquarters serves as the perfect example of deconstructivism which has been a motivation to many other architects and locals. This building adds an identity to Beijing and its skyline and is considered to have not been singularly built by Chinese or Europeans but an amalgamation of both the teams.
