Arch

=Arch =

===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 and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures. The arch can be called a curved lintel. Early masonry builders could span only narrow openings because of the necessary shortness and weight of monolithic stone lintels. With the invention of the arch, two problems were solved: (1) wide openings could be spanned with small, light blocks in brick as well as stone, which were easy to transport and to handle; and (2) the arch was bent upward to resist and to conduct into its supports the loads that tended to bend the lintel downward. Because the arch is curved, the upper edge has a greater circumference than the lower, so that each of its blocks must be cut in wedge shapes that press firmly against the whole surface of neighboring blocks and conduct loads uniformly. ===


 * 


 * A **__//Roman//__** arch is a strong, rounded arch that forms a semi-circle. Often made of masonry, Roman arches still stand in the Coliseum.
 * A **__//Syrian, or segmental//__**, arch forms a partial curve, or eyebrow, over a door or window. This arch has a slight rise and is semi-elliptical across the top.
 * **__//Tudor//__** arches are often described as "flattened" Gothic arches. They feature a point at the crown, but the span is much wider than the Gothic style.
 * A __//**Flat**//__ arch, also known as jack or straight arch, extends straight across an opening with no curvature, creating a horizontal emphasis.
 * A narrow, pointed opening is the hallmark of a **__//Gothic//__** arch. The Gothic arch developed as a more sinuous and elegant successor to the Roman arch and was widely used in cathedrals of the Middle Ages such as Notre Dame in Paris.
 * A __//**Moorish, or horseshoe**//__ arch, extends beyond a semi-circle. The top of the arch is rounded and then curves in slightly before descending.



__//Arch evolution//__
===Arches were known in Egypt and Greece but were considered unsuitable for monumental architecture. In Roman times the arch was fully exploited in bridges, aqueducts, and large-scale architecture. New forms and uses were found in medieval and particularly Gothic architecture (flying buttress, pointed arch), and Boroque architects developed a vocabulary of noncircular forms for expressive reasons. Steel, concrete, and laminated-wood arches of the 20th century have changed the concept and the mechanics of arches. Their components are completely different from wedge-shaped blocks; they may be made entirely rigid so as to require only vertical support ; they may be of hinged intersections that work independently, or they may be thin slabs or members (in reinforce concrete) in which stresses are so distributed that they add the advantages of lintels to those of arches, requiring only light supports. These inventions provide a great freedom of design and a means of covering great spans without a massive substructure. ===



media type="youtube" key="UYtIFM1ek_M" height="385" width="480"