with other weighty shoreline anchorages by a series of iron chains that replaced bamboo cables. Excavated only in 1989, these iron oxen were approximately 3.3 meters long, 1.5 meters high, and about 15 tons in weight, and were joined as well by life-size iron figures of men.
Each of the eight pairs of small shallow-draft boats is lashed together and connected with a stable pathway to form a pontoon bridge nearly 100 meters long in Pucheng county, Fujian. The intervening space between some of them is traversed merely by a series of parallel timbers that can be moved easily if a boat needs to pass.
Although rarely photographed, pontoon bridges of this type were created utilizing bamboo poles lashed together and then floated on the water. To ease passage on foot, a long mat made of thin slats of woven bamboo was laid across the floating slender bamboo poles.
In some ways, pontoon bridges are reminiscent of what takes shape in a Chinese tale of love regarding the Milky Way, which Chinese traditionally saw as a luminous “silver stream” in the heavens. On the seventh day of the seventh month each year, Niu Lang and Zhi Nu, a cowherd and a weaving girl, were allowed to meet when all the magpies on earth flew to heaven and formed a bridge over the galactic stream for them to cross and meet.
In this photograph taken in the 1930s somewhere in southern China, there is only one gap in the adjacent boats that can be opened for river traffic to pass through.
Cantilevered Beam Bridges
Simple wooden and stone beams have limits to the distances they can span, rarely reaching 10 meters. Each quarried stone or cut timber, the most common materials traditionally employed in cantilevered bridges, has an unspecified strength depending on the species and type. Even when they appear homogeneous, each usually contains invisible pockets of weakness. Downward pressures brought on by an increased live load can lead to unanticipated structural failure, the rapid breaking of the beam as it exceeds its ability to bend. It is not surprising then, that practical experience led to the doubling or tripling of beams in order to increase strength, and a sequenced layering in order to extend the range.
At the Chengyang Bridge in Ma’an village, Sanjiang, Guangxi, layers of protruding logs separated by transverse timbers provide cantilevered lifting for the covered bridge.
Chinese bridge builders began in the fourth century CE to employ the cantilever principle—the layering of counterbalanced beams with each set of segments supporting additional beams that reach out towards a midpoint—in order to extend the clear span. This approach involved projecting out horizontal arms of wood, then later stone beams from weighted abutments of piled stone or masonry. Since a gap usually still remained, this opening between them was then spanned with a beam or set of beams. Single-span cantilevered wooden bridges, usually using logs, were frequently built to cross relatively narrow ravines in Yunnan and Sichuan provinces as well as in remote areas of Tibet. In Gansu, even relatively shallow streams were bridged by structures that soared using a cantilevered superstructure.
Cantilevered stone beams are piled above the pier in order to lift the timber beams that support the corridor of the Dongguan (Eastern Pass) Bridge in Dongmei village, Dongguan township, Fujian.
The 33-meter-long Yongqing (Eternal Celebration) Bridge, built in 1797, is lifted by a single cut-stone pier with both stone and timber cantilevering. Above the central corridor is a substantial second storey used as a temple. Sankui township, Taishun county, Zhejiang.
Multiple spans of this type, each comprised of pairs of cantilevered supports, are found today in central and eastern China, especially in Fujian, Guangxi, Hunan, and Zhejiang provinces.
Among the most notable cantilevered wooden bridges in China are the “wind-and-rain” bridges or fengyu qiao of the Dong minority group in southern China. Although the most notable feature of fengyu qiao is the series of colorful pavilions lined along their continuous galleried superstructure, the support beneath is also outstanding since it is usually comprised of sets of massive cantilevered logs. The Chengyang Bridge is another good example. With a length of 77.76 meters and four 17.3-meter-wide openings set upon five piers, it was constructed between 1912 and 1924 in the Sanjiang region of the Guangxi Zhuang Autonomous Region. Three cantilevered layers of fir logs—a series of projecting horizontal beams 7–8 meters in length—are laid longitudinally across the top of each of the five stone piers. Between the four levels of cantilevered logs, which are held firm by tenoned timbers, are thin spacer logs that together stabilize the support and also provide some degree of flexibility. In this region, as elsewhere in southern China, when rebuilding of dilapidated cantilevered structures took place, the length of spans could be maintained by cantilevering more logs of shorter length than were originally used. The Lujiang Bridge in Hunan province, first built in the middle of the thirteenth century and rebuilt many times, at one point had ten layers of cantilevered logs to enable its span.
Activities along as well as in the water beneath an arch bridge crossing the Si River in Shandong province, are exhibited in this rubbing from an engraved brick of the Eastern Han period (CE 25–220).
Arch Bridges
Arches in many shapes and configurations, employing both stone and wood as materials, epitomize the superlative achievements of Chinese bridge building. Stone arch bridges are ubiquitous in China, but arches constructed of timbers, which are sometimes called “rainbow bridges,” are much more limited in their extent. Varying widely in form and in clear span, many arch bridges are merely functional and rather primitive, while others display not only astonishing design skills and techniques of construction but also express exquisite beauty. It is not known definitively when the first stone or timber arch bridges emerged in China but both forms developed independently of those in the West. Since arches are stronger than planks, whether the material is stone or wood, the evolution of arch forms made for the possibility of greater spans and heights. Arches are said to be in compression, pushing outward rather than transferring their weight downward as with planks, and as a result require substantial foundations.
Carved on the surface of a baked brick, this image depicts a horse-drawn carriage and a porter with a carrying pole crossing an arch bridge, which is reinforced with vertical supports beneath.
This tableaux of county scenes in Huizhou, found today in a temple near the Bei’an Bridge in southern Anhui province, includes a steep single-arch bridge with a pavilion atop it.
Although the scholars drinking in the wooded countryside are the main theme of Shitao’s early eighteenth-century Drunk in Autumn Woods, this virtuosic painting incorporates elements that could be found in a small park or garden, including a fine bridge, pavilions, and paths. ©The Metropolitan Museum of Art, New York.
