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Architecture, the practice of building design and its resulting products; customary usage refers only to those designs and structures that are culturally significant. Architecture is to building as literature is to the printed word. Vitruvius, a 1st-century BC Roman, wrote encyclopedically about architecture, and the English poet Sir Henry Wotton was quoting him in his charmingly phrased dictum: "Well building hath three conditions: Commoditie, Firmenes, and Delight." More prosaically, one would say today that architecture must satisfy its intended uses, must be technically sound, and must convey aesthetic meaning. But the best buildings are often so well constructed that they outlast their original use. They then survive not only as beautiful objects, but as documents of the history of cultures, achievements in architecture that testify to the nature of the society that produced them. These achievements are never wholly the work of individuals. Architecture is a social art.
Architectural form is inevitably influenced by the technologies applied, but building technology is conservative and knowledge about it is cumulative. Precast concrete, for instance, has not rendered brick obsolete. Although design and construction have become highly sophisticated and are often computer directed, this complex apparatus rests on preindustrial traditions inherited from millennia during which most structures were lived in by the people who erected them. The technical demands on building remain the elemental ones-to exclude enemies, to circumvent gravity, and to avoid discomforts caused by an excess of heat or cold or by the intrusion of rain, wind, or vermin. This is no trivial assignment even with the best modern technology.
Building Materials
The availability of suitable materials fostered the crafts to exploit them and influenced the shapes of buildings. Large areas of the world were once forested, and their inhabitants developed carpentry. Although it has become relatively scarce, timber remains an important building material.
Many kinds of stone lend themselves to building. Stone and marble were chosen for important monuments because they are incombustible and can be expected to endure. Stone is also a sculptural material; stone architecture was often integral with stone sculpture. The use of stone has declined, however, because a number of other materials are more amenable to industrial use and assembly.
Some regions lack both timber and stone; their peoples used the earth itself, tamping certain mixtures into walls or forming them into bricks to be dried in the sun. Later they baked these substances in kilns, producing a range of bricks and tiles with greater durability.
Thus, early cultures used substances occurring in their environment and invented the tools, skills, and technologies to exploit a variety of materials, creating a legacy that continues to inform more industrialized methods.
Building with stones or bricks is called masonry. The elements cohere through sheer gravity or the use of mortar, first composed of lime and sand. The Romans found a natural cement that, combined with inert substances, produced concrete. They usually faced this with materials that would give a better finish. In the early 19th century a truly waterproof cement was developed, the key ingredient of modern concrete.
In the 19th century also, steel suddenly became abundant; rolling mills turned out shapes that could make structural frames stronger than the traditional wooden frames. Moreover, steel rods could be positioned in wet concrete so as to greatly improve the versatility of that material, giving impetus early in the 20th century to new forms facilitated by reinforced concrete construction. The subsequent profusion of aluminum and its anodized coatings provided cladding (surfacing) material that was lightweight and virtually maintenance free. Glass was known in prehistory and is celebrated for its contributions to Gothic architecture. Its quality and availability have been enormously enhanced by industrial processing, which has revolutionized the exploitation of natural light and transparency.
Construction
When masonry materials are stacked vertically, they are very stable; every part is undergoing compression. The real problem of construction, however, is spanning. Ways must be found to connect walls so as to provide a roof. The two basic approaches to spanning are post-and-lintel construction and arch, vault, and dome construction. In post-and-lintel construction, lintels, or beams, are laid horizontally across the tops of posts, or columns; additional horizontals span from beam to beam, forming decks that can become roofs or be occupied as floors. In arch, vault, and dome construction, the spanning element is curved rather