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The 'Zhaozhou Bridge' () is the world's oldest open-spandrel stone segmental arch bridge.^[1] Credited to a craftsman named Li Chun, the bridge was constructed in the years 595-605 during the Sui Dynasty. Located in the southern part of Hebei Province, it is the oldest standing bridge in China, although the Chinese had built bridges over waterways since the ancient Zhou Dynasty.

Contents

Name and location

Construction

Later history and reputation

Footnotes

External links

Name and location

The Zhaozhou Bridge is also known as the ''Safe Crossing Bridge'' (, englished as the ''Anji Bridge'') and the ''Great Stone Bridge'' (). It crosses the Xiao River (, ''Jiao He'') in Zhao County, approximately 40 km southeast of the provincial capital Shijiazhuang. It is named for the nearby Zhao County (趙縣), which was formerly known as Zhaozhou (趙州).

Construction

The Zhaozhou Bridge is about 50 m long with a central span of about 37 m. It stands 7.3 m tall and has a width of 9 m. The arch covers a circular segment less than a semicircle and has a rise-to-span ratio of approximately 1:5 (7.3 to 37 m). This is considerably smaller than the rise-to-span ratio of 1:2 of a semicircular arch bridge and subjects the abutments of the bridge to large forces.
The central arch is made of 28 thin, curved limestone slabs which are joined with iron dovetails. This allows the arch to adjust to shifts in its supports, and prevents the bridge from collapsing even when a segment of the arch breaks. The bridge has two small side arches on either side of the main arch. These side arches serve two important functions: First, they reduce the total weight of the bridge by about 15.3% or approximately 700 tons, which is vital because of the low rise-to-span ratio and the large forces on the abutments it creates. Second, when the bridge is submerged during a flood, they allow water to pass through, thereby reducing the forces on the structure of the bridge.
Li Chun's innovative spandrel-arch construction, while economising in materials, was also of considerable aesthetic merit. An inscription left on the bridge by Tang officials seventy years after its contruction reads:

Later history and reputation

In the next 1400 years, the bridge survived at least eight wars, ten major floods and numerous earthquakes, the nearest of which being the 7.2 degree Xingtai Earthquake in 1966. Yet, the support structure remains intact and the bridge is still in use. Only the ornamental railings have been replaced every few hundred years.
The intriguing design of the bridge has given rise to many legends. According to one legend, the bridge was built by a master architect named Lu Ban in a single night. In another story, the bridge was put to the test by two immortals who crossed it at the same time and Lu Ban saved it by wading into the water and supporting the structure.
Although Ming Dynasty authors compared the bridge to "a new moon rising above the clouds" and "a long rainbow hanging on a mountain waterfall", it later fell into obscurity. When Professor Liang Sicheng (梁思成) of Tsing Hua University rediscovered the bridge on a field exploration of ancient architecture in Hebei province, made detailed measurements, and published a report and drawing ("An Chi Ch'iao the Great Stone Bridge Chao Hsien, Hobei, Sui Dynasty AD 569-617, Li Chun Master Builder"), it became world famous.
Zhaozhou Bridge was dedicated as an International Historic Civil Engineering Landmark by the American Society of Civil Engineers in 1991. The Chinese authorities nominated it for incription on the World Heritage List as having "a very important place in the world bridge building history".[2]

Footnotes

1. Various Roman ''wooden'' bridges featured segmental arches as early as the 2nd century AD, among them Trajan's bridge, the longest bridge of the world to have been built for over a thousand years. However, the Roman segmental bridge at Alconétar (Province Cáceres, Spain) is older than Zhaozhou, also made of stone, but without open-spandrels.[1] This leaves the Zhaozhou bridge the title of "the oldest ''open-spandrel'' stone segmental arch bridge in the world".

External links

★ American Society of Civil Engineers

★ Asian Research