On Mon, 19 Jul 1999 15:59:33 -0700 "Gina Miller" <firstname.lastname@example.org>
>Does any one here have any architectural insight to a question I have?
>If I>were to begin building a simple structure merely to achieve it's
>epitome of>height, what should it be built of, (not considering the
>nanotubes, but what could be used now) how high would it reach and how
>thick>would the structure have to be in width?
>Gina "Nanogirl" Miller
The tallest buildings use steel for structural strength. The tallest non-guyed buildings are the twin Petronas Towers in Kuala Lumpur, 1455 feet, I think. They are office buildings, possibly with some residential units. They are right next to each other and are connected by a catwalk about halfway up. The tallest guyed towers are for TV transmitting antennas and are as high as about 1400 to 2000 feet. I think the tallest one was in Poland, but it fell sometime in the 1980s.
Steel is used for very tall buildings because it the most economical material for that use. If cost is no object, other materials which have a higher strength to weight ratio than steel could be used, such as titanium or perhaps carbon fiber composites. Doubtless much taller buildings could be constructed using steel than already have been, and even taller using titanium, but there is no economic justification for it. As buildings get higher than about 1000 feet, they become increasingly hazardous to aircraft.
Beyond the issue of choice of materials, extraordinarily tall buildings need a good foundation. The reason why most very tall buildings in Manhattan are in Midtown is that the bedrock comes closer to the surface there, making it easier to drive foundation pilings down to bedrock.
All else being equal, for a non-guyed structure, a tapered design, like the Transamerica building in San Francisco, should allow for greater height. A practical problem with very tall office/residential buildings is that the overhead associated with servicing the upper floors takes up so much space on the lower floors, and costs so much, that the building becomes uneconomical. Many elevators must be provided, for example, to service a very tall building, as the occupants would not want to wait 40 minutes every time they want to take an elevator. The infrastructure of emergency stairs, water supply, fire protection, sewage service, electrical and communications cables, heating, air conditioning, ventilation, and maintenance service elevators takes up a lot of space. Water pumps, pressure tanks, electrical transformers, and emergency systems are needed throughout much of the building. It becomes overwhelming and the building chokes on its own infrastructure.
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