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, forming what is known as bald arch.
The gallery shows arch forms displayed in roughly the order in which they were developed.
Round arch or Semi-circular arch
Segmental arch or arch that is less than a semicircle
Unequal round arch or Rampant round arch
Equilateral pointed arch
Shouldered flat arch -see also jack arch
Three-foiled cusped arch
Reverse ogee arch
Read more about this topic: Arch
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Famous quotes containing the word construction:
“No construction stiff working overtime takes more stress and straining than we did just to stay high.”
—Gus Van Sant, U.S. screenwriter and director, and Dan Yost. Bob Hughes (Matt Dillon)
“The construction of life is at present in the power of facts far more than convictions.”
—Walter Benjamin (18921940)
“No real vital character in fiction is altogether a conscious construction of the author. On the contrary, it may be a sort of parasitic growth upon the authors personality, developing by internal necessity as much as by external addition.”
—T.S. (Thomas Stearns)