கோளப்பரப்புக் குவிமாடம்

கட்டற்ற கலைக்களஞ்சியமான விக்கிப்பீடியாவில் இருந்து.
தாவிச் செல்லவும்: வழிசெலுத்தல், தேடல்

கோளப்பரப்புக் குவிமாடம் (geodesic dome) என்பது கோள மேற்பரப்பு ஒன்றின் பெரு வட்டங்களின் (great circle) மேல் கிடக்கும்படி ஒழுங்கமைக்கப்பட்ட, ஏறத்தாளக் கோளவடிவமான, உதைகால்களின் (struts) வலையமைப்பு ஆகும். இவ் வலையமைப்பில் ஒன்றையொன்று வெட்டுகின்ற பல பெரு வட்டங்களினால் உருவாக்கப்படும் முக்கோண அமைப்புகள் முழுக் கோள வடிவ அமைப்பினதும் உறுதிக்குப் பங்களிப்புச் செய்கின்றன. அளவு அதிகரிக்கும்போது மேலும் பலமுள்ளதாக அமையும், மனிதரால் உருவாக்கப்பட்ட ஒரே அமைப்பு இது என்று சொல்லப்படுகிறது.

மனிதரால் அறியப்பட்ட எல்லா அமைப்புக்களுடனும் ஒப்பிடும் போது கோள வடிவக் குவிமாடமே ஒரு குறிப்பிட்ட நிறைக்கான அதி உயர்ந்த கன அளவைத் தருகிறது. இவ்வமைப்பை உருவாக்கும் தனித்தனி உதைகால்களிலும் பார்க்க மொத்த அமைப்பாக நோக்கும்போது இக் குவிமாடங்கள் அதிக பலம் கொண்டவையாக விளங்குகின்றன.


வரலாறு[தொகு]

Buckminster Fuller developed and named the geodesic dome from field experiments with Kenneth Snelson at Black Mountain College in the late 1940's. Researchers have found antecedent experiments like the 1913 geodesic planetarium dome at the Carl Zeiss plant in Jena, Germany, but it was Fuller that exploited, patented, and developed the idea.

The geodesic dome appealed to Fuller because it was extremely strong for its weight, its "omnitriangulated" surface provided an inherently stable structure, and because a sphere encloses the greatest volume for the least surface area. Fuller had hopes that the geodesic dome would help address the postwar housing crisis. This was in line with his prior hopes for both versions of the Dymaxion House.

From an engineering perspective geodesic domes are far superior to traditional right-angle post-and-beam construction techniques, which are far less efficient, far heavier, inherently instable, and rely on gravity to stand up. But there were drawbacks.

While strong, domes react to external stresses in ways that confound traditional engineering. Some tensegrity structures will retain their shape and contract evenly when stressed on the outside, and some don't. One dome built at Princeton, New Jersey was hit by a snowplow, which popped the struts on the opposing side. To this day, the behavior of tension and compression forces in the different varieties of geodesic structures is not well understood. Traditionally trained structural engineers cannot guarantee their performance and safety.

The dome was successfully adopted for specialized industrial use, like the 1958 Union Tank Car Company dome near Baton Rouge, Louisiana and specialty buildings like the Henry Kaiser dome, auditoriums, weather observatories, and storage facilities. The dome was soon breaking records for covered surface, enclosed volume, and construction speed. Leveraging the geodesic dome's stability, the US Air Force experimented with helicopter-deliverable units. The dome was introduced to a wider audience at Expo '67 the Montreal, Canada World's Fair as part of the American Pavilion. The structure's covering later burned, but the structure itself still stands and, under the name Biosphère, currently houses an interpretive museum about the Saint Lawrence River.

In the "Climatron", built in 1960 at Missouri Botanical Gardens, the original plexiglass panels discolored and were replaced with glass.

Residential domes were less successful. Fuller himself lived in a geodesic dome in Carbondale, Illinois, at the corner of Forest and Cherry, but they never caught on to the extent that Fuller hoped.

குவிமாட வீடுகளின் சாதகமான அம்சங்கள்[தொகு]

They are very strong. The basic structure erects very quickly with a small crew, and light-weight pieces. Domes as large as fifty meters have been constructed in the wilderness from rough materials without a crane. The dome is also aerodynamic, so it withstands considerable wind loads, such as those created by hurricanes. Solar heating is possible by placing an arc of windows across the dome: the more heating needed the wider the arc should be, to encompass more of the year.

Many companies exist today that sell both dome plans and frame material with instruction designed simply enough for owners to build themselves, and many do to make the net cost lower than standard construction homes. Construction techniques have improved based on real world feedback over sixty years and many newer dome homes can resolve nearly all of the disadvantages below that were more true of the early dome homes.

குவிமாட வீடுகளின் பாதகமான அம்சங்கள்[தொகு]

However, as a housing system the dome has numerous drawbacks and problems:

The shape of a dome house makes it difficult to conform to code requirements for placement of sewer vents and chimneys. Off the shelf, all building materials come in rectangular shapes. Fire escapes are problematical; codes require them, and they’re expensive. Windows conforming to code can cost anywhere from five to fifteen times as much as windows in conventional houses. Scrap from cutting (i.e., waste) can run to a high proportion, driving costs up. Professional electrical wiring costs more because of increased labor time; but even owner-wired situations are costly, because more of certain materials is required with a dome versus conventional construction.

Domes have unique interior air-stratification and air-moisture-distribution characteristics. These tend to result in a lack of longevity if wood framing or interior paneling (in the upper portions) has been used, as is often the case with a residential dome. Privacy is compromised in a dome since a dome is difficult to partition satisfactorily, also since sounds circulate (ambience problems are mentioned below). The dome shape leaves the vast majority of the interior surface unusable because of the sharply sloping roof lines. For example, in a 20 foot tall dome, only the bottom 8 feet or so are really usable. This leaves a large volume that must be heated, yet cannot be lived in.

Dome builders find it hard to seal domes against rain. The most effective method with a wooden dome is to shingle the dome. Another method is to use a one-piece reinforced concrete or plastic dome. Some domes have been constructed from plastic or waxed cardboard triangles that overlapped in such a way as to shed water. Domes tend to develop leaks because the sun heats the dome during the daily cycle and the stresses are conveyed through the structure as the sun moves through the sky much as one might break the shell of a hard-boiled egg by simultaneously pressing and rolling.

On the other hand, in Bucky Works : Buckminster Fuller's Ideas for Today, Fuller's former student J. Baldwin states that there is no reason for a dome that is properly designed and constructed and uses proper materials to leak and that some designs cannot leak.

Sounds, smells and even reflected light tend to be conveyed through the entire structure. Lloyd Kahn, author of Domebook One, Domebook 2 and later, Shelter, became disillusioned with domes by 1973, and details many more problems with dome homes on his website[1] calling them smart but not wise. Kahn is the source of many of the criticisms listed above, in this article section, having gathered information widely.

Finally, the furnishing and fitting world is designed with flat surfaces in mind, and installing something as simple as a sofa results in a half-moon behind the sofa being wasted.

Methods of construction[தொகு]

Wooden domes drill a hole in the width of a strut. A stainless steel band locks the strut's hole to a circle of steel pipe. This method lets the struts be simply cut to the exact needed length. Triangles of exterior plywood are then nailed to the struts. The dome is wrapped with several stapled layers of tar paper, from the bottom to the top in order to shed water, and finished with shingles.

Temporary greenhouse domes have been constructed by stapling plastic sheeting onto a dome constructed from 1x1s. The result is warm, movable by hand in sizes less than 20 feet, and cheap. It should be staked to the ground, because it will fly away in strong wind.

Steel-framework domes can be easily constructed of electrical conduit. One flattens the end of a strut, and drills bolt holes at the needed length. A single bolt secures a vertex of struts. The nuts are usually set with removable locking compound, or if the dome is portable, have a castle nut with a cotter pin. This is the standard way to construct domes for jungle-gyms.

Concrete and foam plastic domes generally start with a steel framework dome, and then wrap it with chicken-wire and wire screen for reinforcement. The chicken wire and screen is tied to the framework with wire ties. The material is sprayed or molded onto the frame. Tests should be performed with small squares to achieve the correct consistency of concrete or plastic. Generally, several coats are necessary on the inside and outside. The last step is to saturate concrete or polyester domes with a thin layer of epoxy compound to shed water.

A CGI geodesic sphere rendered using freeware DOME Software and POV-Ray software

Some concrete domes have been constructed from prefabricated prestressed steel-reinforced concrete panels that can be bolted into place. The bolts are within raised receptacles covered with little concrete caps to shed water. The triangles overlap to shed water. The triangles in this method can be molded in forms patterned in sand with wooden patterns, but the concrete triangles are usually so heavy they must be placed with a crane. This construction is well-suited to domes because there is no place for water to pool on the concrete and leak through. The metal fasteners, joints and internal steel frames remain dry, preventing frost and corrosion damage. The concrete resists sun and weathering. Some form of internal flashing or caulking must be placed over the joints to prevent drafts. The 1963 Cinerama Dome was built from precast concrete hexagons and pentagons.

மிகப் பெரிய கோளப் பரப்புக் குவிமாட அமைப்புக்கள்[தொகு]

Many geodesic domes have been built and are in use. According to the Buckminster Fuller Institute Web site, the largest geodesic-dome structures (listed in descending order from largest diameter) are:

இவற்றையும் பார்க்கவும்[தொகு]

உசாத்துணை[தொகு]

  • Geodesic Math and How to Use It by Hugh Kenner, University of California Press (October 1, 2003) ISBN 0520239318
  • Bucky Works : Buckminster Fuller's Ideas for Today by J. Baldwin, John Wiley & Sons (March, 1996) ISBN 0471129534

வெளியிணைப்புகள்[தொகு]