A segmental arch is a type of arch with a circular arc of less than 180 degrees. It is sometimes also called a scheme arch. The segmental arch is one of the strongest arches because it is able to resist

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that sys ...

. To prevent failure, a segmental arch must have a rise 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. As far as is known, the ancient Romans were the first to develop the segmental arch. The closed-

spandrel A spandrel is a roughly triangular space, usually found in pairs, between the top of an arch and a rectangular frame; between the tops of two adjacent arches or one of the four spaces between a circle within a square. They are frequently fill ...

Pont-Saint-Martin bridge The Pont-Saint-Martin is a Roman bridge in the Aosta Valley in Italy dating to the 1st century BC. The span is according to recent research, but frequently stated to be 35.64 m or 36.65 m. Other extant Roman bridges in the Aosta vall ...

in the

Aosta Valley , Valdostan or Valdotainian it, Valdostano (man) it, Valdostana (woman)french: Valdôtain (man)french: Valdôtaine (woman) , population_note = , population_blank1_title = Official languages , population_blank1 = Italian French ...

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

dates to 25 BC. The first open-spandrel segmental

arch bridge An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct ...

is the Anji Bridge over the

Xiao River The Xiao River ( ) is the Main Stream of the upper Xiang River located in Yongzhou, Hunan. As of 2011 Water Census of China, it has a length of from the headwaters to the confluence in the Ping Island of Yongzhou with the Xiang River West Branch ...

Hebei Province Hebei or , (; alternately Hopeh) is a northern province of China. Hebei is China's sixth most populous province, with over 75 million people. Shijiazhuang is the capital city. The province is 96% Han Chinese, 3% Manchu, 0.8% Hui, and 0 ...

in China, which was built in 610 AD. Segmental arches are most commonly used in the 20th century in residential construction over doorways, fireplaces, and windows.

References

;Notes ;Citations {{reflist Arches and vaults