Woven Arch Bridge

Histories of Constructional Thoughts

LIU Yan

• Publisher: Routledge
• Year: 2020
• ISBN:
  9781000223446
• Edition: 1
• Topic: Architecture
• Subtopic: Architecture General

This book focuses on the woven arch bridge, an arch-shaped structure that is one of the most extraordinary timber building traditions of the world. The woven arch bridge exists widely in different cultures and its specific nature is conceptualized by the author as a kind of "universal uniqueness, " challenging widespread viewpoints on its origin and genealogy.

Taking this argument as its main thread, the book traces the histories of different woven-arch-bridge-cultures and investigates in particular the woven arch bridge in the mountains of Southeast of China from three angles, using both archaeological and anthropological methods. Resting upon these case studies, a definition of typology and a new theory of structural evolution are established, while the book also draws comparisons between western and eastern timber building cultures and offers new insights on the differences between East Asia and Europe.

The book also provides a large number of examples and illustrations of the bridge, and will be of great value and inspiration for architects and scholars studying the history of architecture, bridges, and construction, while also appealing to general readers interested in historical bridges and traditional construction technology.

Part I

Woven arch bridges

Three stories

1 From Caesar to Da Vinci

The woven structure’s Italian root

1.1Glory to Caesar!

1.1.1Caesar and his Rhine Bridge

From 58 to 50 bc, during his conquest of Gaul, Julius Caesar (100–44 bc) led his Roman legion into a series of wars to quell the threat posed by the hostile Gallic tribes and other neighbouring forces.

In 55 bc, as a reaction to the constant harassment by some German tribes at the boundary of Roman Gaul, Caesar decided to lead his legion across the Rhine.

A natural boundary between Gaul and the German tribes, the Rhine was known for its great depth, width, and the rapidity of its flow. Although crossing by boat would have been less of a problem, to Caesar this was unsafe and undignified. He determined to make the effort to build a bridge – only then could he frighten the reckless and combative barbarians.

The exact location of the bridge is not clear today; most suggestions point to the area between Andernach and Koblenz, in a comparatively open part of the Rhine Valley. Accordingly, the length of the bridge is speculated to have been between 200 and 400 metres.

The bridge was built in ten days including the collection of timbers. Caesar led his legion over the river, took his revenge on the Germanic villages and struck fear into the Germans. He then led the army back to Gaul and destroyed the bridge. The action was a great military success.

In his Commentarii de bello gallico (Gallic Wars), the report written by his own hand in third-person narration, Caesar described the construction of the bridge with an engineer’s precision and in great detail:

Rationem pontis hanc instituit: tigna bina sesquipedalia paulum ab imo praeacuta dimensa ad altitudinem fluminis intervallo pedum duorum inter se iungebat. Haec cum machinationibus immissa in flumen defixerat festuculisque adegerat, non sublicae modo derecte ad perpendiculum, sed prone ac fastigate, ut secundum naturam fluminis procumberent, his item contraria duo ad eundem modum iuncta intervallo pedum quadragenum ab inferiore parte contra vim atque impetum fluminis conversa statuebat. Haec utraque insuper bipedalibus trabibus immissis, quantum eorum tignorum iunctura distabat, binis utrimque fibulis ab extrema parte distinebantur. Quibus disclusis atque in contrariam partem revinctis tanta erat operis firmitudo atque ea rerum natura, ut, quo maior vis aquae se incitavisset, hoc artius inligata tenerentur. Haec derecta materia iniecta contexebantur ac longuriis cratibusque consternebantur. Ac nihilo setius sublicae et ad inferiorem partem fluminis oblique agebantur, quae pro ariete subiectae et cum omni opere coniunctae vim fluminis exciperent, et aliae item supra pontem mediocri spatio ut si arborum trunci sive naves deciendi operis causa essent a barbaris missae, his defensoribus earum rerum vis minueretur neu ponti nocerent.

(Caesar 1980, 195–8)

[He proceeded to construct a bridge on the following plan: He caused pairs of balks eighteen inches thick, sharpened a little way from the base and measured to suit the depths of the river, to be coupled together at an interval of two feet. These he lowered into the river by means of rafts, and set fast, and drove home by rammers; not, like piles, straight up and down, but leaning forward at a uniform slope, so that they inclined in the direction of the stream. Opposite to these, again, were planted two balks coupled in the same fashion, at a distance of forty feet from base to base of each pair, slanted against the force and onrush of the stream. These pairs of balks had two-foot transoms let into them atop, filling the interval at which they were coupled, and were kept apart by a pair of fibulis on the outer side at each end. So, as they were held apart and contrariwise clamped together, the stability of the structure was so great and its character such that, the greater the force and thrust of the water, the tighter were the balks held in lock. These trestles were interconnected by timber laid over at right angles, and floored with long poles and wattlework, And further, piles were driven in aslant on the side facing downstream, thrust out below like a buttress; and others likewise at a little distance above the bridge, so that if trunks of trees, or vessels, were launched by the natives to break down the structure, these fenders might lessen the force of such shocks, and prevent them from damaging the bridge.]

(Caesar 2006, 62)

In the text, Caesar described a form of trestle bridge with inclined posts in pairs on either side, holding a beam in between. Though written in a detailed and accurate manner, in places, the description is confusing to later readers. The most disturbing term is “fibulis” (plural of “fibulae” or “fibula”), which describes the elements used in pairs at the joints of the middle beam and the posts. Thanks to this particular device, the structure would be even more stable against the thrust of the river water.

There is no satisfactory contemporary definition of the word “fibulis.” A similar term, “fibula,” and its plural form “fibulae,” meaning brooch or pin for fastening garments, might be one of the closest definitions. In the legion, they may have symbolized specific ranks or positions in the Roman army.

Two millennia later, when modern scholars shone the spotlight on Caesar’s Rhine Bridge again, they raised a series of questions including the location of the bridge, the geological environment of the site, the bridge form, the construction process, etc. Among these questions, the structure of the bridge was the topic most focused on; thus the explanation on the form and function of the fibulis served as the key.¹

Although in the narration, Caesar is the bridge planner (“nationem pontis hanc instituit”/ “He proceeded to construct a bridge on the following plan”) this bridge is commonly attributed to Mamurra, his praefectus fabrum (officer in charge of engineering) at that time, a man who held this position from 58 to 54 bc (McDermott 1983, 292–307).

Our knowledge about Mamurra today mainly comes from the description by the poet Catullus: his great fortune from the spoils of wars, his extravagant and lascivious life and – probably just a rumour – his homosexual relationship with Caesar. Despite these bad reputations, Mamurra was considered “by all means the best military engineer of his day” (Frank 1928, 157–9). Among his genius inventions was also a new kind of ship which enabled Caesar’s second invasion of Britain.

There was some speculation as to whether Mamurra and Vitruvius were the same person (Thielscher 1961), although this opinion did not gain general acceptance (Ruffel and Soubiran 1962). The two do have some things in common. Vitruvius, the most well-known architect of antiquity, is the author of the first preserved architectural treatise – De Architectura (Ten Books on Architecture) –which is dedicated to his patron, the emperor Caesar Augustus. He also served in the Roman army as praefectus fabrum under Julius Caesar and was good at designing military constructions and machines. But among other factors that led to the refutation of identifying these two names as one man was the fact that Vitruvius apparently held a much less prominent position than Mamurra. Besides, the Rhine Bridge gives Vitruvius another “alibi.” In his De Architectura, in the tenth book he wrote on military architecture and engines, mainly derived from his experience with C...

Table of contents

• Cover
• Half Title
• Series Information
• Title Page
• Copyright Page
• Table of Contents
• List of Figures
• Introduction
• Part I Woven arch bridges: Three stories
• Part II Woven arch bridges in Southeast China
• Part III Conclusion
• Afterword
• List of referred historical MZ bridges
• Index