Living Things) Bridge in Zhujiajiao watertown in the suburbs of Shanghai.
No multiple arch bridge in China is more illustrious than the Lugou (Reed Gulch) Bridge, which was built at the end of the twelfth century. Because tradition tells us that Marco Polo described the bridge in 1289 as “perhaps unequaled by any other in the world,” it also is often called the Marco Polo Bridge. Once a raging stream flowed under the bridge, but today the broad streambed is essentially dry.
Taken early in the twentieth century, this photograph shows the Shahe (Sandy River) Bridge, also called the Chao-zong (Facing the Ancestors) Bridge, being crossed by a pair of two-wheeled donkey carts. Built in 1447 to replace a wooden bridge, the stone bridge is 13.3 meters wide and has seven arches spanning a length of 130 meters.
In northern China, the celebrated Lugou (Reed Gulch) Bridge has similar renown to that of the Baodai Bridge in the Jiangnan region. Built between 1189 and 1192 during the Jin dynasty, the bridge, with a span of 266.5 meters, was visited in 1280 by Marco Polo, who described it as “perhaps unequaled by any other in the world.” Building the bridge presented distinct challenges due to the fact that the often shallow Yongding River, which it crossed, usually iced over during cold winters in its upper reaches, and then in early spring disgorged ice floes made up of enormous blocks. To counter this, massive stone piers as well as boat-shaped cutwaters on the upstream side of each pier were positioned to deflect or break up the ice as it passed through the eleven arches.
Like other northern bridges, the Lugou’s deck is quite flat to facilitate the passage of carts pulled by human beings, mules, donkeys, horses, and camels. The 485 small stone lions that sit atop the capitals along the balustrades on both sides of the Lugou Bridge are one of its special characteristics.
The Lugou or Marco Polo Bridge is renowned for the countless lions with different poses atop each of the posts along its side balustrades. The old uneven stone surface that caused discomfort to those riding in donkey carts has been preserved while new level paving has been added along the sides. In the distance is the Guandi Temple.
Timber Arch Rainbow Bridges
Rainbow bridges—ingenious arches using “woven” timbers as the underlying structure—until recently were believed to have been lost in the twelfth century. The image preserved in Zhang Zeduan’s twelfth-century Song painting Qingming shanghe tu, usually translated as “Going Up the River During the Qingming Festival,” portrays an interlocked arch of piled beams that allowed large vessels to pass beneath its humpbacked 18.5-meter-long arch. With a width of 9.4 meters, the bridge provided ample space for one of the bustling markets of Kaifeng, the Song imperial capital. In recent decades, reports emerged of bridges with a similar structure—but with the addition of covered corridors—in the remote mountains of Fujian and Zhejiang provinces.
It is noteworthy that more than a hundred variations of covered rainbow bridges have been recently “discovered.” But it is a strange fact that no uncovered bridge with an underlying timber frame, like that shown in Zhang Zeduan’s scroll, has ever been located and documented.
Local people refer to the bridges that seem to rear up abruptly from their abutments and then soar dramatically cross steep chasms as “centipede bridges” because of their resemblance to the arch-like rise of a long arthropod’s body as it crawls. From a distance, these bridges appear to be supported by a type of wooden arch, but in actual fact it is an illusionary “arch” that emerges from the interlinking of a series of logs—long tree trunks—that function as interwoven chords or segments of the “arch.” Chinese engineers refer to such a structure as a “woven timber arch,” “combined beam timber arch,” and “woven timber arch-beam” to underscore the use of straight timber members tied together. The basic components are quite simple: two pairs of two layered sets of inclined timbers, with one set embedded in opposite abutments, stretch upward toward the middle of the stream. To fill the gap between these inclined timber sets, two horizontally trending assemblages of timbers are attached. Transverse timbers tenoned to them and/or tied with rattan or rope hold each of the sets of timbers together. It is these warp and weft elements that give rise to the term “woven.”
The downward pressure of the heavy logs compresses all the components together into a tight and relatively stable composition with a significant bearing capacity, the equilibrium can be upset if forces from beneath—such as might come from torrential floods or typhoon winds—push upward. To further stabilize the underlying structure, additional weight is added by constructing an often elaborate building atop the bridge. Somewhat counter intuitively, the heavy timber columns, beams, balustrades, and roof tiles add a substantial dead load that actually increases stability. With the addition of wooden skirts along the side perimeter, the wooden members are then also protected from weathering and deterioration to create a covered bridge. In the West, the covering of a covered bridge is always described as being added in order to protect the underlying wooden structure from weather, and never as added weight to stabilize the structure.
No “rainbow bridge”is more famous than the one depicted in Zhang Zeduan’s twelfth-century celebrated Qingming shanghe tu scroll, a section of which portrays an interlocked arch of piled beams permitting even large vessels to pass beneath its humpbacked opening. Along the surface of the bridge as well as in nearby lanes are busy markets. © Palace Museum, Beijing.
In 1999, in Jinze, a watertown suburb of Shanghai, a modest “rainbow bridge”was built as part of the NOVA television series to re-create the wooden substructure of the famed twelfth-century Qingming shanghe tu using ”woven” timbers to form an arch-like interlocking structure.
In 1999, an American television crew associated with the science series NOVA worked with a team of Chinese scholars and timber craftsmen to design and build a Chinese bridge. Believed at the time to be attempting something unknown except in a twelfth-century painting, the project successfully completed a model bridge that still stands in Jinze, a canal town on the shores of Dianshang Lake in the western suburbs of Shanghai. Working without plans and increasingly aware of how difficult the tasks were, the team experimented with materials and techniques to create an interlaced superstructure of beams placed under and over girders that meta-morphosed from a beam to an arch structure. Their bridge is a modest one when compared with those still found in southern Zhejiang and northern Fujian or even the one depicted by Zhang Zeduan.
Far surpassing this modest effort to create a rainbow bridge reminiscent of the one in Kaifeng are the numerous covered bridges with similar structures in Zhejiang and Fujian provinces, details of which are given on pages 218–47. A fine example, not discussed there, is Xianju (Home of the Immortals) Bridge, about 20 kilometers from the Taishun county town. Built first in 1452 and then rebuilt in 1673, it has the longest span of any bridge of this type in Taishun—34.14 meters—and an overall length of 41.83 meters. The bridge was spared when the highway was improved with an adjacent modern bridge. Rising like a slithering centipede, the covered gallery of the Xianju Bridge utilizes eighty slender pillars to fashion its nineteen internal bays. The rooftop ornamentation is especially notable.
Rising high enough for motorized vessels to move beneath it, Jinze’s newly constructed timber “rainbow bridge”joins many very old stone bridges along the nearby canals.
Covered
