What is "skew arch"

Skew \Skew\, a. Turned or twisted to one side; situated obliquely; skewed; -- chiefly used in technical phrases. Skew arch, an oblique arch. See under Oblique. Skew back. (Civil Engin.)

1. The course of masonry, the stone, or the iron plate, having an inclined face, which forms the abutment for the voussoirs of a segmental arch.

2. A plate, cap, or shoe, having an inclined face to receive the nut of a diagonal brace, rod, or the end of an inclined strut, in a truss or frame.

   Skew bridge. See under Bridge, n.

   Skew curve (Geom.), a curve of double curvature, or a twisted curve. See Plane curve, under Curve.

   Skew gearing, or Skew bevel gearing (Mach.), toothed gearing, generally resembling bevel gearing, for connecting two shafts that are neither parallel nor intersecting, and in which the teeth slant across the faces of the gears.

   Skew surface (Geom.), a ruled surface such that in general two successive generating straight lines do not intersect; a warped surface; as, the helicoid is a skew surface.

   Skew symmetrical determinant (Alg.), a determinant in which the elements in each column of the matrix are equal to the elements of the corresponding row of the matrix with the signs changed, as in (1), below. [1913 Webster] (1) 0 2 -3-2 0 53 -5 0 (2) 4 -1 71 8 -2-7 2 1

   Note: This requires that the numbers in the diagonal from the upper left to lower right corner be zeros. A like determinant in which the numbers in the diagonal are not zeros is a skew determinant, as in (2), above.

n. an arch whose jambs are not at right angles with the face

A skew arch (also known as an oblique arch) is a method of construction that enables an arch bridge to span an obstacle at some angle other than a right angle. This results in the faces of the arch not being perpendicular to its abutments and its plan view being a parallelogram, rather than the rectangle that is the plan view of a regular, or "square" arch.

In the case of a masonry skew arch, the construction requires precise stonecutting, as the cuts do not form right angles, but once the principles were fully understood in the early 19th century, it became considerably easier and cheaper to build a skew arch of brick.

The problem of building skew arch masonry bridges was addressed by a number of early civil engineers and mathematicians, including William Chapman (1787), Benjamin Outram (1798), Peter Nicholson (1828), George Stephenson (1830), Edward Sang (1835), Charles Fox (1836), George W. Buck (1839) and William Froude (c. 1844).