igloo |
arch |
top 10 words in brain distribution (in article): build common house type form refer people line popular allow |
top 10 words in brain distribution (in article): build material wood structure form type state wall surface building |
top 10 words in brain distribution (not in article): plant state wear city horse fruit century grow power Unite |
top 10 words in brain distribution (not in article): city cell house store street town floor home design Unite |
times more probable under igloo 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under arch (words not in the model) | |
An igloo'" (Inuit language: "iglu", Inuktitut syllabics: ᐃᒡᓗ, "house", plural: "iglooit" or "igluit", but in English commonly "igloos"), translated sometimes as snowhouse'", is the Inuit word for house or habitation, and is not restricted exclusively to snowhouses but includes traditional tents, sod houses, homes constructed of driftwood and modern buildings. Igloo as a snowhouse. When referring to a snowhouse, igloos are shelters constructed from blocks of snow, generally in the form of a dome. Although igloos are usually associated with all Inuit, they were predominantly constructed by people of Canada's Central Arctic and Greenland's Thule area. Other Inuit people tended to use snow to insulate their houses which consisted of whalebone and hides. Snow was used because the air pockets trapped in it make it an insulator. On the outside, temperatures may be as low as, but on the inside the temperature may range from to when warmed by body heat alone. Traditional types. There were three traditional types of igloos, all of different sizes and all used for different purposes. The smallest was constructed as a temporary shelter, usually only used for one or two nights. These were built and used during hunting trips, often on open sea ice. Next in size was the semi-permanent, intermediate-sized family dwelling. This was usually a single room dwelling that housed one or two families. Often there were several of these in a small area, which formed an "Inuit village". The largest of the igloos was normally built in groups of two. One of the buildings was a temporary structure built for special occasions, the other built nearby for living. These might have had up to five rooms and housed up to 20 people. A large igloo might have been constructed from several smaller igloos attached by their tunnels, giving common access to the outside. These were used to hold community feasts and traditional dances. Modifications. The Central Inuit, especially those around the Davis Strait, lined the living area with skin, which could increase the temperature within from around 2 °C (36 °F) to 10-20 °C (50-68 °F). Construction. The snow used to build an igloo must have sufficient structural strength to be cut and stacked in the appropriate manner. The best snow to use for this purpose is snow which has been blown by wind, which can serve to compact and interlock the ice crystals. The hole left in the snow where the blocks are cut from is usually used as the lower half of the shelter. Sometimes, a short tunnel is constructed at the entrance to reduce wind and heat loss when the door is opened. Due to snow's excellent insulating properties, inhabited igloos are surprisingly comfortable and warm inside. In some cases a single block of ice is inserted to allow light into the igloo. Architecturally, the igloo is unique in that it is a dome that can be raised out of independent blocks leaning on each other and polished to fit without an additional supporting structure during construction. The igloo, if correctly built, will support the weight of a person standing on the roof. Also, in the traditional Inuit igloo the heat from the kulliq (stone lamp) causes the interior to melt slightly. This melting and refreezing builds up an ice sheet and contributes to the strength of the igloo. The sleeping platform is a raised area compared to where one enters the igloo. Because warmer air rises and cooler air settles, the entrance area will act as a cold trap whereas the sleeping area will hold whatever heat is generated by a stove, lamp or body heat. In popular use. In heraldry, the igloo appears as the crest in the coat of arms of Nunavut. "Nanook of the North". The 1922 documentary "Nanook of the North" contains the oldest surviving movie footage of an Inuit constructing an igloo. In the film, Nanook (real name Allakariallak) builds a large family igloo as well as a smaller igloo for sled pups. Nanook demonstrates the use of an ivory knife to cut and trim snow block, as well as the use of clear ice for a window. His igloo was built in about one hour, and was large enough for five people. The igloo was cross-sectioned for filmmaking, so interior shots could be made. See "External links" for video footage. | An arch'" is a structure that spans a space while supporting weight (e.g. a doorway in a stone wall). Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture, but their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures. History. Arches were known by the Mesopotamian, Urartian, Harappan, Egyptian, Babylonian, Greek and Assyrian civilizations, but their use was infrequent and mostly confined to underground structures such as drains where the problem of lateral thrust is greatly diminished. The ancient Romans learned the arch from the Etruscans, refined it and were the first builders to tap its full potential for above ground buildings: "The Romans were the first builders in Europe, perhaps the first in the world, fully to appreciate the advantages of the arch, the vault and the dome." Throughout the Roman empire, their engineers erected arch structures such as bridges, aqueducts, and gates. They also introduced the triumphal arch as a military monument. Vaults began to be used for roofing large interior spaces such as halls and temples, a function which was also assumed by domed structures from the 1st century BC onwards. The Roman arch is semicircular, and built from an odd number of arch bricks (called "voussoirs"). An odd number of bricks is required for there to be a "capstone" or "keystone", the topmost stone in the arch. The Roman arch's shape is the simplest to build, but not the strongest. There is a tendency for the sides to bulge outwards, which must be counteracted by an added weight of masonry to push them inwards. The Romans used this type of semicircular arch freely in many of their secular structures such as aqueducts, palaces and amphitheaters. The semicircular arch was followed in Europe by the pointed Gothic arch or ogive (derived from the Islamic pointed arch in Moorish Spain), whose centreline more closely followed the forces of compression and which was therefore stronger. The semicircular arch can be flattened to make an elliptical arch as in the Ponte Santa Trinita. The parabolic and catenary arches are now known to be the theoretically strongest forms. Parabolic arches were introduced in construction by the Spanish architect Antoni Gaudí, who admired the structural system of Gothic style, but for the buttresses, which he termed “architectural crutches”. The catenary and parabolic arches carry all horizontal thrust to the foundation and so do not need additional elements. The horseshoe arch is based on the semicircular arch, but its lower ends are extended further round the circle until they start to converge. The first examples known are carved into rock in India in the first century AD, while the first known built horseshoe arches are known from Aksum (modern day Ethiopia and Eritrea) from around the 3rd–4th century, around the same time as the earliest contemporary examples in Syria, suggesting either an Aksumite or Syrian origin for the type of arch. It was used in Spanish Visigothic architecture, Islamic architecture and mudéjar architecture, as in the Great Mosque of Damascus and in later Moorish buildings. It was used for decoration rather than for strength. Across the ocean in Mexico and Central America, Mesoamerican civilizations created various types of corbelled arches, such as with the interior tunnels in the Great Pyramid of Cholula and the many styles of corbelled arches built by the Mayan civilization. In Peru, the Inca civilization used a trapezoidal arch in their architecture. The arch is still used today in some modern structures such as bridges. Construction. An arch requires all of its elements to hold it together, raising the question of how an arch is constructed. One answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting. For an arch higher than head height, scaffolding would in any case be required by the builders, so the scaffolding can be combined with the arch support. Occasionally arches would fall down when the frame was removed if construction or planning had been incorrect. (The A85 bridge at Dalmally, Scotland suffered this fate on its first attempt, in the 1940s). The interior and lower line or curve of an arch is known as the "intrados". Old arches sometimes need reinforcement due to decay of the keystones, known as bald arch. The gallery shows arch forms displayed in roughly the order in which they were developed. Technical aspects. The arch is significant because, in theory at least, it provides a structure which eliminates tensile stresses in spanning an open space. All the forces are resolved into compressive stresses. This is useful because several of the available building materials such as stone, cast iron and concrete can strongly resist compression but are very weak when tension, shear or torsional stress is applied to them. By using the arch configuration, significant spans can be achieved. This is because all the compressive forces hold it together in a state of equilibrium. This even applies to frictionless surfaces. However, one downside is that an arch pushes outward at the base, and this needs to be restrained in some way, either with heavy sides and friction or angled cuts into bedrock or similar. This same principle holds when the force acting on the arch is not vertical such as in spanning a doorway, but horizontal, such as in arched retaining walls or dams. Even when using concrete, where the structure may be monolithic, the principle of the arch is used so as to benefit from the concrete's strength in resisting compressive stress. Where any other form of stress is raised, it has to be resisted by carefully placed reinforcement rods or fibres. (See Arch bridge.) Other types. The Delicate Arch, a natural arch in Moab, UtahA blind arch is an arch infilled with solid construction so it cannot function as a window, door, or passageway. A dome is a three-dimensional application of the arch, rotated about the center axis. Igloos are notable vernacular structures making use of domes. Natural rock formations may also be referred to as arches. These natural arches are formed by erosion rather than being carved or constructed by man. See Arches National Park for examples. A special form of the arch is the triumphal arch, usually built to celebrate a victory in war. A famous example is the Arc de Triomphe in Paris, France. A vault is an application of the arch extended horizontally in two dimensions; the groin vault is the intersection of two vaults. |