Ancient Bridges
China is a great country with a written history of about 5000 years. She has a vast territory, topographically higher in the northwest and lower in the southeast. Networked with rivers, she has the best-known valleys of the Yangtze River, the Yellow River and the Pearl River, which are the cradle of the Chinese nation and her brilliant culture. Throughout history, the Chinese nation has erected thousands of bridges, which form an important part of her culture.
Ancient Chinese bridges are universally acknowledged and have enjoyed high prestige in the bridge history of both the East and the West.
Ancient Chinese bridges can be classified under four categories: the beam, arch, cable suspension and floating bridges.
I. Beam Bridges
The earliest reference to the beam bridge in Chinese history is the Ju Bridge dating from the Shang Dynasty (16th-11th century B.C.). King Wu of the Zhou Dynasty launched a campaign against King Zhou (Zhou Wang), and having captured Zhaoge -capital of the Shang Dynasty (now northeast to Quzhou County, Hebei Province), at the Ju Bridge, he ordered a hoard of millet distributed to the relief of the poor. From the Zhou Dynasty through to the Qin and Han Dynasties, bridges with timber beams and stone piers were predominant.
During the Song Dynasty, a large number of stone-pier and stone-beam bridges were constructed. In Quanzhou alone, as recorded in ancient books, 110 bridges were erected during the two centuries, including ten well-known ones. For example, the 362-span Anping Bridge (Fig. 1) was known for its length of 5 li (2223m), a national record for over 700 years, and so gained the other name Five Li Bridge. It is now 2100m long. Its construction lasted 16 years, from the 8th year (A.D. 1138) to the 21st year (A.D. 1151) of the reign of Shaoxing of the Song Dynasty. Another famous one is the 47-span Wan'an Bridge, situated at the outlet of the Luoyang River to the sea, better known as Luoyang Bridge (Fig.2). It is about 890m long and 3.7m wide. The construction began in the 5th year of the reign of Huangyou (A.D. 1053) and ended in the 4th year of the reign of Jiayu (A.D. 1059) of the Song Dynasty. Both bridges are included in the list of major cultural relics under state protection.
The Jiangdong Bridge in Zhangzhou, Fujian Province boasts the largest stone beams. In the first year of the reign of Jiaxi (A.D. 1237) of the Song Dynasty, the timber beams of this bridge were replaced by stone ones. The bridge had 15 spans, each consisting of 3 slices of stone beams. But today only 5 spans remain. The largest stone beam, 23.7m in length, 1.7m in width and 1.9m in height, weighs 2000 kN (200 tons). It seems incredible that such an arduous task could be performed then as there was no heavy-duty craning equipment to quarry the stone and to haul to the site and set in position such enormous stone beams.
To elongate the span, either the timber beams or the stone ones were placed horizontally on top of each other, the upper layer cantilevering over the lower one, thus supporting the simple beam in the middle. That kind of stone beam is called Diese (overlapping beam), which, however, could not extend long; while the timber cantilever beam, called "flying bridge" or "extended arm bridge", could reach as far as 20m. The earliest record of the timber cantilever beam dates as far back as the 4th century B.C. The extant single-span timber cantilever bridge, the Yinping Bridge at Wenxian, Gansu Province, which was rebuilt in the Qing Dynasty, has a span of more than 60m with covered housings on it.
It was common practice to build bridge housings or galleries on timber beam bridges, and a case in point is the fengyu bridge (all-weather bridge) built by the Dong people. Situated at Sanjiang Dong Autonomous County, Guangxi Zhuangzu Autonomous Region, the Chengyang Bridge across the Yongji River (Fig. 3), built in 1916, is a 644m 4-span timber cantilever covered bridge. Each of its 5 piers is crowned by a pavilion and the decks are roofed by a spacious gallery, which joins the pavilions. The pavilions not only perform the function of balance, but have added to the charm and elegance of the bridge as well.
II. Arch Bridges
There are different views on the origin of arches. Some believe the first arch was a natural formation over the caverns, others claim that it was brought into being by the piling of the collapsed stones, and still others hold that it was evolved from the "false arch" which was formed by the openings in the walls. However, a study of the tombs and the extant old arches in China indicates that the joint of the beam and sides evolved gradually into isometric trilateral, pentalateral and septilateral arches and finally into semicircular arch. The span, too, was gradually elongated, from 2m or 3m up to 37.02m (clear span). And it has kept the world record for more than a thousand years.
The oldest arch bridge in China, which is still surviving and well-preserved, is the Anji Bridge, also known as the Zhaozhou Bridge, at Zhouxian, Hebei Province, built in the Sui Dynasty (Fig. 4). It is a single segmental stone arch, composed of 28 individual arches bonded transversely, 37.02m in span and rising 7.23m above the chord line. Narrower in the upper part and wider in the lower, the bridge averages 9m in width. The main arch ring is 1.03m thick with protective arch stones on it. Each of its spandrels is perforated by two small
arches, 3.8m and 2.85m respectively in clear span, so that flood water can be drained and the bridge weight is lightened as well. The Anji Bridge has a segmental deck and the parapets are engraved with dragons and other animals. Its construction started in the 15th year of the reign of Kaihuang (A.D. 595) and was completed in the 1st year of Daye's reign (A.D. 605) of the Sui Dynasty. Up to now it has survived for 1387 years. The bridge, exquisite in workmanship, unique in structure, well-proportioned and graceful in shape, and meticulous yet lively in engraving, has been regarded as one of the greatest achievements in China. Great attention and protection have been given to it through successive dynasties. In 1991, the Anji Bridge was
named among the world cultural relics.
Stone arches in China vary in structure in accordance with different land transport as well as different natures between the north and south waterways. In the north, what prevails is the flat-deck bridge with solid spandrels, thick piers and arch rings, whereas in the south crisscrossed with rivers, the hump-shaped bridge with thin piers and shell arches prevails.
The Lugou Bridge (Fig. 5) across the Youngding River is located at Wanping County, 30 li away from Guanganmen, Beijing. The project began in the 28th year of the reign of Dading (A.D. 1188)and was completed in the 3rd year of the reign of Mingchang (A. D. 1192) of the Jin Dynasty. 212.2m long, 9.3m wide, it has 11 semicircular arches, ranging from 11.4m to 13.45 m in span. The piers are from 6.5m to 7.9m wide; their pointed cutwaters upstream are inlaid with triangular iron bars, while the downstream sides are square in shape butwithout two angles. The parapets are divided into 269 sections with columns in-between, each column crowned with a carved lion. When the bridge was first erected in the Jin Dynasty, all the lions were alike and very simple, but through the ages they were replaced each time by better ones, more delicately carved and different in style. Now, each lion has its individual posture. And more fascinating are the lion cubs. They are playing around their parents, clinging to the breast, squatting on the shoulder, nestling at the feet, or licking the face. These exquisite sculptures on the bridge and on the ornamental columns, which show the practical application of the aesthetic principle of unity and variation, have become a scene of attraction. The bridge has long since been included in the historical relics under state protection.
In the southern part of China, say, Jiangsu and Zhejiang Provinces, networked with navigable rivers, boats were the main means of transportation. As bridges were to be built over tidal waters and their foundations laid in soft soil, even the stone arch bridge had to be built with thin piers and shell arches in order that its weight could be lessened as much as possible. The spans ranged in number from one to as many as 85. For example, the Chuihong Bridge in Wujiang, Jiangsu Province. But the bridge has collapsed and now only 8 ruined spans remain.
The thinnest arch ring is merely 1/66.7th the span, whereas for an average arch the ring is 1/20th the span. The extant Feng Bridge (the Maple Bridge) (built in the Qing Dynasty), mentioned in the well-known poem "A Night Mooring Near the Maple Bridge" by Zhang Ji of the Tang Dynasty, is characterized by its shell arch.
The thin pier is so thin that the arch stones of the neighboring arch rings meet on it. A special reference should be made here to the thin-pier bridge with 3 joint spans, a large middle span and two small side ones. There are steps on both approaches for pedestrians to ascend the bridge. It is hump-shaped and looks graceful. The Gongchen Bridge (Fig. 6) in Hangzhou, Zhejiang Province is a typical example. The bridge was built in the 4th year of Chongzhen's reign (A.D. 1631) of the Ming Dynasty and reconstructed in the 11th year of the reign of Guangxu (A.D. 1885) of the Qing Dynasty. The middle arch is 15.8m long in clear span, while the two side ones, 11.9m each. The arch ring stone is 30cm thick, 1/52.7 and 1/39.7 of the corresponding span. The middle pier is around 1m thick, 1/15.8 of the middle span. The longest surviving joint multi-span bridge with shell arches and thin piers is the Baodai Bridge (Fig. 7) in Suzhou, Jiangsu Province. Built in the Tang Dynasty and having undergone a series of renovations in successive dynasties, the bridge is now 316.8m long, 4.1m wide and has 53 spans in all, the three central arches higher than the rest for boats to pass through. Both ends of the bridge are ornamented with lions, or pavilions and towers, all of stone.
The bridge in classical Chinese gardens not only serves as a passage, but is an integral part of the garden scenery, either as a highlight or a setoff. One masterpiece of this kind is the Wuting (Five Pavilions) Bridge (Fig. 8), also known as the Lianhua (Lotus Flower) Bridge in the Shouxi Lake in Yangzhou,Jiangsu Province.
The timber arch bridge in China dates back to the Song Dynasty. In the panorama "Riverside Scene on Qingming Festival" by Zhang Zheduan of the Song Dynasty, there is portrayed a timber arch bridge, known as the Hong Bridge (the Rainbow Bridge) (Fig. 9) spanning the Bian River in Bianjing, capital of the Song Dynasty (now Kaifeng, Henan Province). It was built following the pattern of guanmu (the interlocking of logs), put forward by a prison guard during the reign of Mingdao (A.D. 1032- 1033) of the Song Dynasty. Planks were interdigitated to form a kind of arch, thus obviating the necessity for piers which would usually get in the way of navigation. The span of this bridge was around 18.5m in length, 4.2m in height above the chord line, and the deck averaged 9.6m in width. See Fig.10a for its structural pattern. The Hong Bridge fell into ruin between the Jin and Yuan Dynasties. For hundreds of years it had been considered to be peerless. However, investigations during the recent decades have shown that in the mountain areas of Zhejiang and Fujian Provinces, there were found dozens of ancient timber arch bridges, similar to the Hong Bridge in structure, but with some improvements, their spans as long as 35m or so. Fig.10b illustrates the structural perspective and construction pattern of the Meichong Bridge in Yunhe, Zhejiang Province, which was built in the 7th year of Jiaqing's reign (A.D.1802) of the Qing Dynasty. Another example is the Xidong Bridge spanning the Sixi Stream at Taishun County, Zhejiang Province (Fig. 11). The bridge is 41.7m long, 4.86m wide, with a 25.7m span rising 5.85m above the chord line. On the deck there is an exquisite gallery, both sides of which are panelled with overlapping boards for protection. It was constructed in the 4th year of the reign of Longqing (A.D. 1570) of the Ming Dynasty. Amazingly enough, the Yeshuyang Bridge, another of this kind in the same county, has survived for 511 years.
The timber arch of such bridges as the Hong Bridge is a unique achievement of ancient China. Besides, there are still other kinds of peculiar structures, like bamboo arch bridges, which are also unparalleled in the world.
III. Cable Suspension Bridges
Cable suspension bridges vary in kind according to the material of which the cables are made: rattan, bamboo, leather and iron chain. According to historical records, 285 B.C. saw the zha bridge (bamboo cable bridge). Li Bin of the Qin State, who guarded Shu (256 -251 B.C.), superintended the establishment of 7 bridges in Gaizhou (now Chengdu, Sichuan Province), one of which was built of bamboo cables.
The iron-chain bridge is said to date as far back as the early time of the Western Han Dynasty. Senior General Fan Kuai superintended the construction of the Fanhe Bridge (206 B.C.) on the ancient plank road in Maocheng County (now Liuba County), Shanxi Province; and the bridge is believed to be of iron chain. In historical records there is a clear reference to the iron chains across the Yangtze River. In A.D. 280, the army of Kingdom Wu, when attacked by the Western Jin, threw several iron chains across the mouth of the Xilin Gorge, one of the three gorges of the Yangtze River, to block away the enemy ships.
The Jihong Bridge (Fig. 12) at Yongping County, Yunnan Province, is the oldest and broadest bridge with the most iron chains in China today. Spanning the Lanchang River, it is 113.4m long, 4.1 m wide and 57.3m in clear span. There are 16 bottom chains and a hand rail chain on each side. The bridge is situated -on the ancient road leading to India and Burma.
The Luding Iron-chain Bridge (Fig. 13) in Sichuan Province, the most exquisite of the extant bridges of the same type, spans the Dadu River and has served as an important link between Sichuan Province and Tibet. The bridge was believed to be set up by Tianquanzhou bridge-builders who were noted for making iron chains. Its erection began in the 4th year of the reign of Kangxi (A.D. 1705) of the Qing Dynasty and was completed in the following year. It is 100m in clear span, 2.8m in width, with boards laid on the bottom chains. There are 9 bottom chains, each about 128 meters long, and 2 hand-rail chains on each side. On each bank, there is a stone abutment, whose dead weight balances the pulling force of the iron chains. The Luding Bridge is included in the first group of major cultural relics under state protection.
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