Lecture on Structural Design [Topic 3: Ancient Stone and Wood Structures] Lecture 8: Kintaikyo Bridge = The Marvel of Ancient Japanese Woodworking Technology 3
Kintaikyo Bridge: Structural beauty through the perfect manifestation of mechanics and mathematics
This is teaching material (partial) for the lecture "Architectural Structural Design" at the Department of Architecture, Faculty of Engineering, Tokyo University of Science.
Topic 3: Ancient Stone and Wood Structures
Lecture 1: Roman Arches and Domes: The Pantheon
Lecture 2: Truth and Beauty of Large Spaces through Innovative Technology
~Case studies: Hagia Sophia, Santa Maria del Fiore Cathedral, and the Taj Mahal~
Lecture 3: Truth, Beauty, and Ornamentation in Structural Mechanics
~Case studies: Notre-Dame Cathedral, Milan Cathedral, Cologne Cathedral, and St. Peter's Basilica~
Lecture 4: Summary: The Deep Relationship Between Gothic Architectural Ornamentation, Structure, and Mechanics
Lecture 5: Japanese Stonemasonry and Masonry Construction Techniques
Lecture 6: Japanese Wood Construction Techniques: Izumo Taisha
Lecture 7: Japanese Wood Construction Technology - Horyu-ji Five-Story Pagoda -
Lecture 8: Japanese Wood Construction Technology - Kintai Bridge - (Here)
Kintai Bridge
The Kintai Bridge, which spans the Nishiki River in Iwakuni City, Yamaguchi Prefecture, was built in 1673 by the lord of the Iwakuni Domain at the time.
The Kintai Bridge has been rebuilt many times due to flood damage.
The current foundation consists of 10-meter-deep caissons (box-shaped structures) with reinforced concrete platforms, finished with stone cladding.
This strengthens the foundation and structure while maintaining its original appearance.
In 2002, the main wooden framework was rebuilt.
The arch-shaped wooden structure can be seen in its entirety when looking up at the girders from the riverbank.
It is a captivating work of art in terms of woodworking technology.
The span of the five-arch set is approximately 35m, the rise is approximately 5m, and the width is approximately 5m.
The shape of the arch is a hyperbolic function.
When you hold both ends of a string, the shape it takes is a catenary.
It is a shape where self-weight and tensile force are in equilibrium; although it looks curved, only axial force is acting upon it.
The Kintai Bridge is shaped like an inverted catenary, so although it is curved, only compressive force acts upon it.
A structure freed from bending has less stress load and becomes a structure with high cross-sectional efficiency.
The shape of the Kintai Bridge can also be seen in modern architectural masterpieces.
You can see the challenges and examples of structural designers who created shapes using this principle, such as Antoni Gaudi's funicular experiments and their application to architecture, Heinz Isler's inverted hanging shells, and Eero Saarinen's Jefferson Memorial Arch.
These are also called catenary curves, funicular curves, or catenary curves.
At the Tokyo International Forum, structural systems based on catenary curves are effectively employed everywhere.
The roof of Makuhari Messe is also a catenary curve.
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Steel Structure Teaching Materials (E-book)
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