Hesiod and the Muse

Wednesday, January 5, 2011

A City of The Future: The Bionic Tower

The Bionic Tower, as proposed

The Idea: "The Bionic Tower" is a vertical city being proposed in Hong Kong. Yes you read correctly- a vertical city, as in the tower will be a city within itself, containing more than 10 neighbourhoods. As the Jeffersons sang it, "We're moving on up to the East Side, to a deluxe apartment in the sky-y-y!"

The Architectural Trend: The tower will follow the recent (or not so recent for the nit-picky) storm of futuristic plans that promote sustainable architecture, as well as ideas for a future city which can account for the Eastern world's superfluous populations. Namely Hong Kong, the city's future developments are driven largely by its growing population, which is is quoted to reach a predicted 9 million, nearly of Canada's population. And so, the Bionic Tower at this point looks like a pretty viable option as a more sustainable future city than the conventional horizontal city.

Hong Kong's 2030 Planning Vision and Strategy Document found on the Hong Kong government's website shows that the city would like:

•Closer links with the Mainland
•More sustainable use of land resource
•More jobs closer to homes

The Bionic Tower would very likely ensure all of the above desires for the city's residents. The debate is now spurring on how to make a city such as this more palatable to the rest of the world in terms of human social and physical occupation and integration.

Project Planning: Construction due to start in 2015, and end around 2025 thus taking 10+ years for completion and occupation. Currently, Shanghai is also showing interest in the project making the location of this proposed tower somewhat elusive at this point.

Specs: The building will be all inclusive of: offices, residences, perhaps multiple hotels, an university, kindergarten schools, primary/elementary schools, libraries, cinemas, eco-friendly spaces and even a casino. In height, it will ascend until 1228 m, and span an area of 2 000 000 square meters. The tower-city, built on micro-structured high strength concrete, will be able to host up to 100 000 residents in various neighbourhoods, each of which will get its resources by 92 upright columns.

Structural Considerations:

A tall building requires attention from several different physics aspects. The vertical downward force of gravity is not the only thing that affects a tall building. A structure such as the Bionic Tower must have state of art systems which endure horizontal winds ramming against the structure, aswell as absorb earthquake tremors. Most tall structures, for example the CN Tower in Toronto which stands at 553 m, can sway horizontally and is in fact built for flexibility. The highest point of the CN tower which is the Antenna, when subject to strong winds can move up to 1.07 m! The sky-pod in the tower is able to move almost 0.5 m from the centre. The fact that the tower can move so far and wide is all good and dandy— however, the main problem with wind-effects on tall standing structures is how the motion affects the people who reside inside. An easy solution for medium sized buildings is to simply tighten up the connection from the foundation and upwards so that the building moves as a whole system, rather than separate portions moving on their own. Generally, these buildings are “Type I” lateral load resisting systems, and consist of horizontal and vertical trusses that make up a semi-rigid to a rigid frame. However just doesn't cut it for super-tall structures which require a strong central core that is fortified with steel truss, and diagonal beams which criss cross each other all the way up from the base to the top. This type of use of diagonal tubes is what ensures strong fortification of a super-tall building, making it a “Type IV”. The other “Types” in between I and IV include other truss design forms in the structure’s skeleton.
Image Courtesy of Thornton Tomasetti

The fascinating part here, is that the Bionic Tower will push the extents of modern engineering, and will assume a “floating” foundation, rather than a vertical one. This means that the base of system will resemble something like the roots of a tree that will yield thousands of branches that keep the whole central structure afloat. Going back to what this means in terms of lateral movements and wind effects, the maximum sway of the Bionic Tower would be around 2.45 meters.
Image Courtesy of Eloy Celaya, Spanish Architect of the Bionic Tower.
A general approach to understand the stability of a building is to consider the aspect ratio, or the ratio between the building’s height and base width. So a good ratio between height and base is generally around 6 or 7. For the Bionic Tower, which would stand at around 1228 m, the base width would need to be some where around a fifth of a kilometre or around 180 m, in order to attain a safe aspect ratio of 7.

The drag coefficient, C, that is created by winds ramming against a vertical structure, also depends on the geometric form of the structure. A square-ish structure would have a relatively higher C, whereas the lovely phallic looking Bionic Tower would have a much lower C. To put some numbers into context, the Type 4 Eiffel Tower has a C of 1.8; a Formula One Race Car has C of 0.7; a bullet has a C of 0.7.

A Shift in Urban Planning- "Vertical Cities":Ofcourse, there are a myriad of other considerations which the structure’s engineering and architectural teams will have to nit-pick and fine-tune that are beyond the scope of this article. If this tower is to be built, and the project is finalized, within our generation we will surely see a new paradigm shift in urban living, where not only will people be sleeping and residing in these homes, but perhaps they will also be socializing, going to school, working, playing all within the vicinity of one or two vertical upward city their entire lives— a stark and perhaps even a horrific contrast to our conventional horizontal cities today.

This article was inspired by a pod-cast released by HowStuffWorks.com which talks about the many new advances and visions of futuristic cities and urban planning.

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