Chinese Bridges. Ronald G. Knapp

of deformation without the bridge collapsing.

      Located on a canal to the southwest of Suzhou in the small town of Mudu, this triple-arch span had a roofed structure on it that served to collect tolls from pedestrians who crossed the bridge.

      At the end of the nineteenth century, countless arch bridges such as this one with its moon-shaped reflection, were found throughout the Jiangnan region around Suzhou.

      One of China’s most beautiful arch bridges is the Taiping (Heavenly Peace) Bridge along the canal between Hangzhou and Ningbo to the west of the city of Shaoxing, Zhejiang. Built first in 1620 and then again in 1858, it is well known for its exquisite carved balustrades.

      The lofty Wumen (Wu Gate) Bridge in Suzhou, Jiangsu, is located along the Grand Canal near the important Pan Gate. Said to date to the Song dynasty, it was rebuilt in the middle of the nineteenth century to a length of 63 meters.

      Chinese stonecutters clearly accumulated experience that led logically to the development of different styles of bridges. Relatively crude semicircular single-arch spans can be seen in many areas of southern China, some of which are quite old. Many, however, are of more recent origin, the handiwork of local artisans who gather stones from nearby streambeds in order to fashion serviceable work-aday bridges as others did for centuries before them. Semicircular arches of dressed stone dot the Chinese landscape in large numbers. Descriptive names such as “horse’s hoof,” “egg-shaped,” “pot bottom,” and “pointed” are suggestive of other variations of elliptical and parabolic shapes. Some arches are polygons comprised of interlocked rectangular stone beams. Arches of this type echo similar ones found in Chinese tombs as well as gates through city walls, and even the Great Wall. While permitting a greater span than simple beams, polygonal beam bridges are, however, structurally weaker than true arch bridges. On the other hand, as the number of inclined stone beam segments in a multisided polygonal bridge increases from three to as many as seven, the structure begins to function much like a true arch bridge.

      In the countryside of southern Huizhou, straddling the border between today’s Anhui and Jiangxi provinces, countless old stone arch bridges still serve today’s villagers. Although this bridge has a name, Qingjin (Celebrate Gold) Bridge, no information is available on its history.

      A small unnamed single-arch bridge along the canal east of Shaoxing, Zhejiang.

      Many stone arch bridges are infilled with earth and have seams between the cut stone that tends to allow dust to accumulate, filling the spaces so that, in time, seeds are able to germinate. As the roots of plants grow, they then have the capacity of loosening the stone blocks, shifting them sometimes to a point where gravity brings portions of the bridge down. It is not uncommon, even today, as can be seen in many photographs, for plants of all sorts to grow out from a bridge. In colder areas, moreover, these conditions are compounded because of the freezing and thawing of water that runs into or builds up in the seams, again with the means of dislodging the stone and leading to failure of the structure.

      The Zhaozhou Bridge figures prominently in woodblock print culture throughout northern China, probably because of the association with Lu Ban, the patron saint of carpenters and builders, who is said to have built the bridge. After the bridge was completed, legend says that the Eight Immortals decided to cross it in order to test its strength. Lu Ban, fearing that the bridge might not support their weight, jumped into the water beneath to prop up the span with his outstretched hands. Both the polychrome and black-and-white prints from different workshops show variations of this theme.

      Segmental Arch Stone Bridges

      Among the most remarkable achievements of Chinese bridge building—indeed an advancement unrivalled in the world—was the creation of a segmental arch bridge at the end of the sixth century and beginning of the seventh century. This innovation, which predated similar forms in the West by 800 years—repudiated the convention that a semicircular arch was necessary to transfer the weight of a bridge downwards to where the arch tangentially meets the pier. The celebrated Zhaozhou Bridge, China’s oldest standing bridge and the oldest open spandrel bridge in the world, seemingly flies forth from its abutments. The double pair of openings piercing both ends of the arch spandrel, which at once accentuate its lithe curvature, lighten the weight of the bridge and facilitate the diversion of flood waters by allowing them to pass through the auxiliary arches rather than pound against the spandrels.

      When this photograph was taken sometime before 1928, the Zhaozhou Bridge had been altered somewhat and there was sufficient water in the stream for vessels with sails to pass.

      Although built more than 1,400 years ago, the Zhaozhou Bridge in Hebei appears like a contemporary bridge because of its low line and open spandrels.

      Following the pattern of the Zhaozhou, also called Anji (Safe Passage) and Dashi (Great Stone), Bridge, no fewer than four were built in nearby areas of Hebei province where natural conditions were similar, while at least twenty others were constructed in northern China as well as in Guizhou and Guangxi. Until the middle of the twentieth century, the Zhaozhou Bridge was the longest single-arch span bridge in China. The restoration of the Zhaozhou to its original form and the building of similar bridges in recent times confirm that the Chinese recognize their early achievements in engineering technique and aesthetic expression. A masterpiece built almost 1,400 years ago, the Zhaozhou Bridge foreshadowed the elegance and scale of many contemporary bridges. In terms of economy of materials and aesthetic qualities, it is clearly the direct ancestor of the relatively light and lithe modern reinforced concrete bridges that dispense with stonework between the curvature of the arch and the flat deck above. As discussed on pages 123–7, the circumstances surrounding the construction of the Zhaozhou Bridge reveal the conscious attention to natural conditions, transportation requirements, and available materials, in addition to inspired creativity.

      As with the Zhaozhou Bridge, each of the double sets of openings that pierce the arch spandrel on both ends of the smaller Yongtong (Eternal Crossing) Bridge reduces the weight of the structure and eases the flow-through of water during flood.

      Multiple Arch Bridges

      Multiple arch bridges are widely found in China, compelling evidence of both the diffusion of designs throughout the empire and the innovative skills of local bridge builders. Surprisingly monumental structures in what are today backward villages stand as a testament to the vitality of road and river transport in centuries past, the same commercial energy that gave rise to the magnificent mansions of merchants and gentry in out-of-the-way places. As with multiple-span beam bridges, arches were linked together to bridge greater distances than was possible with a single arch. Almost always an odd number, ranging from as few as three to as many as seventy, the duplication of spans almost always invokes pleasing rhythm with its repeating elements. Arch bridges with three spans are especially common in Jiangsu and Zhejiang provinces in a region of a dense canal network. Soft alluvial soils in this low-lying region meant that bridges had to be relatively light. In addition, it was necessary for the bridges