Sunday, June 23, 2013

Lifting the limits on buildings

Lifts and skyscrapers: The other mile-high club | The Economist:

'via Blog this'

Elevators have shaped our cities. Long story short, they allow for vastly greater population densities by making buildings five stories or higher practical to live and work in. While walking up ten flights of stairs might not be that big of a deal for those of us who are young or in good physical condition, it's a whole 'nother story if you're aging and need to carry your groceries up eight stories. Or if you need to routinely shift furniture or office supplies up sixty flights of stairs.

Apparently one of the major limiters on the size for present day buildings is the sheer weight of elevator cables. The steel rope needed to lift a small compartment up fifty or more stories is the heaviest part of the system, and anything beyond 500 meters (1500 ft) risks a cable that will snap because of its own weight. The solution to this limit is that favorite science fiction standby, carbon fibers. A Finish company has created a usable carbon fiber rope with a weight reduction of 90%, and the capability to function at twice the length of steel cables.

Now the questions is will elevators capable of servicing mile-high buildings lead to another great increase in human population densities? Or will things like lack of suitable foundation bedrock limit future construction waves. If you look at the skylines of cities like Manhattan or San Francisco, chances are the the clusters of tall, cloud scarping buildings you see correspond with solid, weight-bearing platforms of rock beneath.

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