Design and periodic inspection of the kintai-kyo wooden arch bridge

The Kintai-kyo Bridge is a unique, five-span wooden bridge with three arches across the Nishiki River, the largest river of the Yamaguchi Prefecture, Japan. The central wooden rib arch is very rare in the world. The bridge has become a famous landmark because of its elegant structure and its aesthetic appearance that is in harmony with the surrounding picturesque landscape. It is a popular historical site and attracts many tourists. The wooden bridge has been rebuilt several times since its inauguration in 1673. The latest rebuilding was done in 2004 which was almost 50 years after the previous one. The original span length of the Kintai-kyo Bridge was close to the limit allowed for construction of wooden bridges during that time. In order to strengthen the bridge against floods, the best combination of wood and stone was used. Arch structure was adopted for the superstructure, and hollow stone piers of spindle-shaped cross-section were adopted in the substructure. This paper studies the origin of the arch structure of the Kintai-kyo Bridge because this arch is unique and different from the voussoir arch or the corbel arch, and its resulting elegant appearance. In addition, as a unique feature, periodical inspections of the Kintai-kyo Bridge have been conducted by the Waseda University every 5 years since 1953, where the weight of local high-school students is used as the load for testing.