As the reseach object，the railway bridges and other structures along the former Japan National Railwayu27s Kamishihoro line were of good design and harmonize well with the surrounding environment. These structures were constructed in Taisetsu National Park and are in within the eastern section of the Taisetsu mountain range in the interior of Hokkaido island after 1936. Campaigns to preserve certain of the structures are in progress. The purpose of this study is to investigate and evaluate these concrete that have given so many structures that have given so many years of service. As noted， the object structures are railway structures in an inland, cold environment. The characteristics of their deterioration and the influence of freezing and thawing are investigated. The following conclusion can be drawn. 0n the judgement results of soundness shown,the whole average condition is period of increasing deterioration rate as an example Daisanotofuke bridge. 0n the judgement results of difficulty of repair and reinforcement， the condition are slight repair necessary or almost complete repair. Regarding the balance between the repairing cost and the dismantling cost， the almost bridges are advantageous to repair and preserve than dismantling.
展开▼
