Zhaozhou Bridge

Zhaozhou Bridge
The Zhaozhou Bridge, still standing after 1400 years
Official name	趙州橋
Crosses	Xiao River
Locale	Zhao County in Hebei Province, China
Design	Open-spandrel stone segmental arch bridge
Longest span	37.37 metres (123 ft)
Total length	50.82 metres (167 ft)
Width	9.6 metres (31 ft)
Height	7.3 metres (24 ft)
Beginning date of construction	595
Completion date	605
Coordinates	37°43′12.6″N, 114°45′47.7″ECoordinates: 37°43′12.6″N, 114°45′47.7″E

The Zhaozhou Bridge (traditional Chinese: 趙州橋; simplified Chinese: 赵州桥; pinyin: Zhàozhōu Qiáo) is the world's oldest and largest open-spandrel stone segmental arch bridge.^[1] Credited to the design of a craftsman named Li Chun, the bridge was constructed in the years 595-605 during the Sui Dynasty (581–618). Located in the southern part of Hebei Province, it is the oldest standing bridge in China.

Name and location

The Zhaozhou Bridge is also known as the Safe Crossing Bridge (traditional Chinese: 安濟橋; simplified Chinese: 安济桥; pinyin: An Ji Qiáo, englished as the Anji Bridge) and the Great Stone Bridge (Chinese: 大石桥; pinyin: Dà Shí Qiáo). It crosses the Xiao River (traditional Chinese: ; simplified Chinese: 洨河; pinyin: Xiào Hé, 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 37.37 m. It stands 7.3 m tall and has a width of 9 m. The arch covers a circular segment less than half of a semicircle (84°)and with a radius of 27.27 m, has a rise-to-span ratio of approximately 0.192 (7.3 to 37 m). This is considerably smaller than the rise-to-span ratio of 0.5 of a semicircular arch bridge and slightly smaller than the rise-to-span ratio of 0.207 of a quarter circle. The arch length to span ratio is 1.1, less than the arch-to-span ratio of 1.57 of a semicircle arch bridge by 43%, thus the saving in material is about 40%, making the bridge lighter in weight. The elevation of the arch is about 45°[2], thus subjects the abutments of the bridge to downward force and sideway force.

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 Dynasty officials seventy years after its construction 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 Zhaozhou Bridge influenced the design of later Chinese bridge structures, such as the similar Yongtong Bridge near Zhaoxian in Hebei. The Yongtong Bridge is a 26 m (85 ft) long stone segmental-arch bridge built in 1130 by the Song structural engineer Pou Qianer.^[3]

The intriguing design of the Zhaozhou 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 (1368–1644) authors compared the bridge to "a new moon rising above the clouds" and "a long rainbow hanging on a mountain waterfall"^[2], 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".[3]

Footnotes

External links

• American Society of Civil Engineers: History and Heritage of Civil Engineering (select "Landmark Projects", then "Zhaoahou Bridge")
• Asian Research
• Chinaculture.org Site sponsored by the Ministry of Culture of the People's Republic of Chinade:Anji-Brücke

es:Puente Zhaozhou fr:Pont de Zhaozhou ru:Мост Аньцзи