|
Jettying (jetty, jutty, getee (obsolete) from Old French getee, jette)〔Oxford English Dictionary, 2nd ed. 1989. Jetty〕 is a building technique used in medieval timber-frame buildings in which an upper floor projects beyond the dimensions of the floor below. This has the advantage of increasing the available space in the building without obstructing the street. Jettied floors are also termed ''jetties''.〔(Illustration of a jettied house )〕〔(Techniques )〕 In the U.S. this style house became called a garrison house.〔Noble, Allen George, and M. Margaret Geib. Wood, brick, and stone: the North American settlement landscape. Amherst: University of Massachusetts Press, 1984. 22.〕 Most jetties are external, but some early Medieval houses were built with internal jetties.〔Alcock, N. A., Michael Laithwaite. "Medieval Houses in Devon and Their Modernization". ''Medieval Archaeology'' vol. 17 (1973), 100–125. http://archaeologydataservice.ac.uk/catalogue/adsdata/arch-769-1/dissemination/pdf/vol17/17_100_125.pdf accessed 01/08/2013〕 == Structure == A jetty is an upper floor that depends on a cantilever system in which a horizontal beam, the jetty bressummer, supports the wall above and projects forward beyond the floor below (a technique also called ''oversailing''). The bressummer (or breastsummer) itself rests on the ends of a row of jetty beams or joists which are supported by jetty plates. Jetty joists in their turn were slotted sideways into the diagonal dragon beams at angle of 45° by means of mortise and tenon joints. The overhanging corner posts are often reinforced by curved jetty brackets. The origins of jettying is unclear but some reasons put forward for their purpose are:〔Harris, Richard. Discovering timber-framed buildings. 2d ed. Aylesbury: Shire Publications, 1979. 55–57.〕 * To gain space. * The structural advantage of the jettied wall counteracting forces in the joists or tying a stone wall together * To shelter the lower walls of the house from the weather. * To simplify joinery. * Uses shorter timbers, a benefit due to timber shortages and difficult handling of long timbers especially in city streets. * As a status symbol〔Garvan, Anthony N. B., Architecture and Town Planning in Colonial Connectucut (New Haven: Yale University Press, 1957. 92.〕 or "...symbol of wealth and status."〔Harris, Richard. Discovering timber-framed buildings. 2d ed. Aylesbury: Shire Publications, 1979. 56.〕 Jetties were popular in the 16th century but banned in Rouen in 1520 relating to air circulation and the plague, and London in 1667 relating to the great fire. They are considered a Gothic style. Structurally, jetties are of several types: * Framed on multiple joists. * Framed on a few beams. * Framed on brackets added to the posts. * Hewn jetty also called a false jetty: Framed on projections of the posts rather than on cantilevered beams (or brackets).〔Davies, Nikolas, and Erkki Jokiniemi. Dictionary of architecture and building construction. Amsterdam: Elsevier/Architectural Press, 2008. 144. false jetty.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Jettying」の詳細全文を読む スポンサード リンク
|