Chinese Bridges. Ronald G. Knapp

widely in many areas of northern and northwestern China.

      This rubbing from a carved brick from the Eastern Han period (CE 25–220) shows a horse-drawn carriage passing over a stone and slab wood bridge.

      Just outside the imposing gate of the walled city, as depicted in Zhang Zeduan’s twelfth-century painting, Qingming shanghe tu, is a moat crossed by a broad bridge. Probably made of stone and wood beams, it clearly had sufficient strength and width to accommodate throngs of animals, humans, and carts. © Palace Museum, Beijing.

      Shrouded in a misty atmosphere, this landscape painting titled Waters Rise in Spring by Shitao (1642–1707) features a common beam bridge using a trestle-like structure of slim poles and crosspieces. © Shanghai Museum.

      Constructed of modular sets of supporting legs, cross-pieces, and wooden planks, long trestle bridges of this type are common in the villages of southern Anhui and northern Jiangxi.

      Timber plank trestle bridges called zhandao have long been common in western Sichuan. Their construction involves sinking wooden substructures into nearly vertical cliffs in order to support the plank paths laid on them.

      Not all wooden beam bridges spanned streams. Indeed, some snaked their way as timber trestle structures through inhospitable topography using building practices that improved upon those employed in shorter wooden beam bridges. Unrivalled in the world is the elevated timber plank bridge-road system that linked the cradle of Chinese civilization in the Wei He River valley of Shaanxi province in the northwest with the fertile Sichuan Basin in the southwest. Well known in Chinese history as the Shudao or “Road to Sichuan” and built at least as early as the Han period (206 BCE–CE 220), the wooden plank trestle bridge served as a channel of administrative, military, and cultural communication as well as trade for some 2,000 years across the formidable barrier of the Qinling and Daba ranges. Although the road fell into decay in the nineteenth century, portions of it are still used by local mountain dwellers to pass from one watershed to another and to avoid swiftly moving streams in narrow river gorges.

      About a third of the 700-kilometer-long Linking Cloud Road, which forms a significant portion of the Shudao as it threads its way through the rugged Qinling Range, is actually comprised of wooden trestle shelves built out from canyon sides or astride streambeds. Termed gedao and zhandao, literally “hanging” bridges, timber plankways involved sinking wooden substructures into nearly vertical cliffs in order to support the plank paths. Herold J. Wiens, a geographer who studied the Shudao, explains that repairs and reconstruction taking three years during the Later Han period (CE 25–220) required the conscripted labor of 766,800 men working some 23 million man-days. During the Tang dynasty (618–907), the celebrated Buddhist monk Xuan Zang, accompanied by the Monkey King, wrote of zhandao as well as rope bridges, iron chains, and wooden ladders necessary to traverse the dangerous precipices of the region on his pilgrimage west. Structurally daring and indeed sometimes dangerous, trestle frameworks—with horizontal, vertical, and slanted supports—have even been employed in the building of imaginative temple structures on the sides of high precipices, such as the celebrated Hanging Temple at Datong in northern Shanxi province.

      Stone beam bridges—most short but many comprising multiple spans—eventually became the most common and permanent bridge form in southern China. Resting atop piers of piled carved stone placed parallel to the flow of the stream, many stone beam bridges are quite simple, while many also are quite complex in that they are supported by massive pier structures built up within midstream cofferdams. Even a cursory examination reveals that stone beam bridges require more substantial abutments and piers than bridges built using timbers. Cantilevering the beams, as discussed below, made it possible to extend the span. The engineer Fugl-Meyer critiqued building in stone with his observation that “the Chinese bridge builder taxes his material to the utmost without allowing for any margin of safety. When a stone has a hidden fault... or when it is overloaded, it collapses without causing any surprise, and is replaced by a new stone of the same dimensions” (1937: 59–60). Metamorphosed granite, which varies in hues of gray and is rather coarse in texture, is the most widely used material for stone beam bridges.

      The sprawling painting titled Emperor Minghuang’s Journey to Shichuan, a Ming copy after an original by Qiu Ying (1494– 1552), details the flight of Emperor Xuanzong and the imperial concubine Yang Guifei from Chang’an, today’s Xi’an, southward along the Shudao or “Road to Sichuan” in order to escape the An Lushan Rebellion of 755. © Freer Gallery of Art, Smithsonian Institution, Washington, DC.

      This view is from atop the Bazi (Character Eight) Bridge, today covered in vines, towards a canalside neighborhood of low-rise dwellings that retains much of its traditional life.

      Rather complex in terms of its scale and ingenious construction, the Bazi Bridge nonetheless is essentially a bridge constructed of long beams and smaller blocks of granite in carefully assembled stacks.

      Perhaps the longest multiple-span stone beam bridge—one extant single segment has 150 spans with a total length of some 390 meters—is actually the remnant of a 1–2 kilometer-long towpath, called qiandao in Chinese. Overall, there are some 7.5 kilometers of stone paths still standing, a fraction of what once existed. These towpaths were constructed between 1862 and 1874 along the Xiaoshan-Shaoxing Canal in Zhejiang province to extend canal transport beyond the terminus of the Grand Canal at Hangzhou eastward to the seaport at Ningbo. The towpath thus served as a passageway for trackers who were needed to pull the heavily laden boats along. While the canal boats were usually propelled by sails or by sculling, sometimes it was necessary to tow them when strong seasonal winds made sailing difficult.

      The gradual incline of a set of steps makes it possible for two adjacent canals to be connected.

      As this model clearly reveals, the Bazi Bridge is actually a combination of two bridges juxtaposed so that it connects multiple lanes while facilitating canal traffic.

      Some portions of the towpath were built immediately adjacent to land; indeed, at some locations trackers actually moved on land before reaching another stone pathway, but in others the towpath was very much like a bridge as stone beams supported by stone piers rose a meter or so above the water. In terms of materials used and techniques of construction, tow-paths differed little from common stone beam bridges that crossed streams. Each of the piers supporting the towpath is composed of a stack of granite blocks approximately 1.5 meters thick. Each span between them is made up of three or more rough-cut stone beams that exceed 2 meters in length and have a width of 3 meters. At intervals along the towpath, a section is elevated to permit the passage of small boats plying the intricate canal network of this region.

      An outstanding and complex stone beam bridge with many components is the Bazi (Character Eight) Bridge in the southeastern section of Shaoxing, Zhejiang, a city that had in 1903 some 229 fine bridges along its 29 canals. The oldest extant urban bridge in China, the Bazi was constructed in 1256 during the later Song dynasty. Located to meet the needs of foot and water traffic at the junction of three canals and three lanes, the structure is actually made up of two juxtaposed bridges that are reminiscent of the