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Supertall is a term that refers to a skyscraper exceeding 1000 feet or 300 meters. It also applies to proposed structures over 1 kilometer (1000m/3281ft) or 1 mile (5280ft/1609m) in height — designs which never advanced beyond the concept or planning stages.
Almost every current supertall structure is among the top 10 in a particular category of height. Conceptual supertall designs, such as The Illinois by Frank Lloyd Wright (image, right), X-Seed 4000, and Sky City 1000 are probably technologically and architecturally feasible, but are considered by some to be simply too tall to be of any particular use. Critics suggest that the current world economic situation does not require such a massive concentration of people and capital and, in the wake of the September 11, 2001 attacks, fear that such towers will almost certainly become terrorist targets.
Others, however, consider these designs to be bold and visionary, seeing them as portending a shift in the nature of urban living towards multilayered cities, and reflective of the natural human impulse to always build bigger or taller structures.
Requirements, advantages and disadvantages of supertall structures
Although building supertall structures is often a way of showing prestige, their erection can be sometimes throughout sensitive:
Supertall radio masts and towers for UHF-/VHF-transmission allow a wide area of reception. Because of reflections, which disturb reception, their erection is only sensitive in flatter areas. As one can see in List of masts and List of towers, nearly all high radio towers are situated in flat areas.
Supertall mast radiators, e.g. a half-wave radiator for longwave radio allow a larger area of fade-free reception. However, because nowadays the range of longwave transmitters is more greatly determined by other stations in the same channel, their usage brings fewer advantages. The only realized supertall mast radiator of this kind was the Warsaw Radio Mast. Nevertheless, supertall mast radiators and antenna structures are suitable for VLF transmissions.
Satisfactorily working VLF and LF transmitters can be built without the necessity for supertall towers; for instance the Kalundborg transmitter and SAQ in Grimeton, both using towers which are approximately 120 metres high.
Supertall chimneys improve the dispersion of gases from a factory. However, they do not eliminate toxic substances of the smoke, merely more widely distribute them. Due to pollution laws in most counties today, their usage is in most cases obsolete, but can be sensitive for power stations situated in valleys.
Conversely, solar chimneys have to be built as supertall structures, because this improves the efficiency of their facility.
A future use for supertall structures may be special towers with maglev tracks for launching spacecraft and space elevators.
Supertall skyscrapers save land. However, problems with fire safety and quick evacuation rapidly escalate the taller a building becomes. The more people there are in a supertall structure, the more difficult evacuation becomes in case of disaster. In addition, it becomes more difficult to deal with the matter of water supply and sewage as these factors increase.
Building supertall structures of any kind is expensive, because the erection costs do not grow in direct proportion to height of structure, but grow faster. So a 1000 ft (305 m) radio mast costs between $0.7 and $1.1 million to build, while a 2000 ft (610 m) radio mast costs $2.4 to $4 million to build (for free-standing structures the erection costs escalate almost exponentially with increasing height, unlike supported structures with guyed masts).
It must be also considered that supertall structures have to withstand greater wind forces than their smaller counterparts, requiring various structural engineering measures to be put in place to compensate, and that their construction site must also be tuned with flight safety authorities.
See also
"Supertall"