Graceful and very tall, GuangZhou’s new TV and Sightseeing Tower reached the dizzy heights of 612m earlier this year. Jessica Rowson reports on the structural form of this willowy wonder.

Television towers tend, by their nature, to be tall. Sticking out above the skyline, they can come to embody a city ?? think of the Telecom Tower in London, or the Fernsehturm in Berlin. The new TV and Sightseeing Tower in Guangzhou is no exception. With an elegant and unusual twisted lattice structure, it will act as a symbol for china’s third largest city.

A port on The Pearl River 120km north west of Hong Kong, Ghangzhou is the capital of Guangdong province. It has a population of 10M and cutting edge telecommunications are vital to the city’s developing prosperity. But more than that, having a TV tower that ranks among the most striking in the world is a matter of municipal pride.

Municipal pride

From a distance, Ghangzhou’s TV tower has a discernibly feminine form, growing from a broad elliptical base at ground level to a tapering waist and then widening slightly up to a second, smaller elipse at the main roof, 450m above. The 162m-long mast takes the final height of the tower to 612m. The shape was developed by imagining that the two ovals were connected by straight lines, forming a cylinder which narrowed, after which the ovals were twisted 35?? relative to each other.

“Hence the twisted lady look,” says Arup director Man Kang. Arup’s London office collaborated on the Ghangzhou project with Information Based Architecture (IBA) of Amsterdam, for which the tower is a first major project. The concept was developed by Arup and IBA in Amsterdam, after which an increasing amount of work was done by Arup’s chinese offices in association with the local design institute.

The tower’s geometry was refined using parametric associative software, which can generate geometrical and structural models based on a set of variable parameters and link the geometrical data to the analytical and drafting software. The result is a form that is both simple and complex.

The main load carrying elements of the tower’s structural lattice are its steel columns which taper as they climb and twist up the building. Infilled with concrete, these are 1.8m in diameter at the bottom reducing to 800mm at the top. Horizontal rings of steel attached inside the columns keep these in the right position and help balance the forces created by the fact that they effectively slope. Diagonal members then give the structure added rigidity.

“By creating a triangulated framework, the sloping columns are stabilised while their elegance is maintained,” explains Kang.

A matter which needed particular care was how the joints between the columns, rings and diagonals were treated as the connections affect the way in which the structure behaves. “For buckling, we needed to look at joint stiffness and for that we needed to look at adjoining members,” says Kang.

The waistline tightening caused by the rotation between the two ellipses makes the central portion of the tower very dense ?? the lattice structure being much more porous and spacious at the bottom and top of the tower.

There is an open-air staircase with views over the city in the waist area, where it does not make financial sense to build floors. “We’re not looking at a building here. It’s primarily a tower that has some floors,” says Kang.