In these days of stable growth of economy in Japan, proper operation and maintenance of existing structures which have been used for many years have become an important subject. Furthermore, making improvements in the study of this problem, it is pointed out that replacement plans of the structures based on life term prediction should be applied. However, as compared with operation and maintenance, life term prediction is much more difficult because of necessity of data base on material changes with the passage of time.
The purpose of this paper is to describe the investigation results of life term prediction techniques focusing on hydropower steel structures. They are composed of simplified data acquisition and structural analysis, data base, expert system and others. Especially expert system plays an important role among them.