Segmental arch

A segmental arch is a type of arch with a circular arc of less than 180 degrees.^[1] It is sometimes also called a scheme arch.^[2]

A segmental arch.

The segmental arch is one of the strongest arches because it is able to resist thrust.^[3] To prevent failure, a segmental arch must have a rise^[a] that is equal to at least one-eighth the width of the span. Segmental arches with a rise that is less than one-eighth of the span width must have a permanent support or frame beneath the arch to prevent failure.^[3]

As far as is known, the ancient Romans were the first to develop the segmental arch. The closed-spandrel Pont-Saint-Martin bridge in the Aosta Valley in Italy dates to 25 BC.^[5] The first open-spandrel segmental arch bridge is the Anji Bridge over the Xiao River in Hebei Province in China, which was built in 610 AD.^[6]

Segmental arches are most commonly used in the 20th century in residential construction over doorways, fireplaces, and windows.^[3]

References

Notes

1. The "springing line" is the imaginary horizontal line drawn between the two points at which the arch's springer touches the impost. The "rise" is the distance from the springing line to the highest point of the "intrados" (bottom of the arch).^[4]

Citations

1. Harris, Cyril M. (1983). Illustrated Dictionary of Historic Architecture. New York: Dover Publications. p. 485. ISBN 9780486244440.
2. Smith, Percy Major (2015). Rivington's Building Construction. Abingdon, Oxfordshire, U.K.: Routledge. p. 6. ISBN 9781317742432.
3. Kreh, Richard T. (2015). Masonry Skills. Stamford, Conn.: Cengage Learning. p. 401. ISBN 9781285426839.
4. Auslander, Alfred (June 1910). "Lessons in Architectural Drawing for Beginners". The Building Age. p. 241. Retrieved June 4, 2017.
5. O'Connor, Colin (1993). Roman Bridges. Cambridge, U.K.: Cambridge University Press. p. 171. ISBN 9780521393263.
6. Temple, Robert K.G. (1986). China: Land of Discovery. Wellingborough, Northamptonshire, U.K.: Stephens. pp. 69–71. ISBN 9780850598582.