Kato Kiyomasa became the Load of Higo (northern half of Kumamoto prefecture) in 1588 and the development of Kumamoto city began from that period. Choroku bridge was constructed under the direction of Kato Kiyomasa and it is believed to be the first bridge over the Shirakawa river which runs across the Kumamoto city from east to west. Because of swift-moving waters of the Shirakawa during the rainy season, this wooden bridge was demolished and reconstructed repeatedly. From the second half of Meiji era, people wished eagerly for a strong steel bridge against the flood and the former Choroku bridge was realized in 1927 as the largest steel tied-arch of Japan.
This paper describes the design concept of the former Choroku bridge. The contextual meaning of the bridge site is discussed based on the research of documents and local news papers about the successive Choroku bridges and citezen's activities for the realization of the steel bridge. It is concluded that the understanding of regional sociological history as well as technological history are very important criteria for the evaluation for civil engineering structures
