Abstract
Now, the deterioration of a structure built at period of high economic growth advances, and the number for diagnosis is increasing rapidly. The bridges is no exception, although the number of the 50-year progress bridges in Japan was approximately 15,000 of 9% of the whole in 2011, they are excepted to increase even to 44,000 which will be equivalent to 28% in 2021, and also 84,000 to be gone up also to 53% in ten years. Even among them, it is necessary to inspect the high power bolt used for the construction of the steel bridge in that regularly because the slack occurs with progress at time. We can carry out without being dangerous activity easily at low cost if we use hammering test. However, this method has a part depending on perception and the experience of the expert, and is insufficient of them. Therefore, we tried to evaluate quantitatively the atteacors that obtained from impact acoustics for the purpose of what even a engineers without enough experience can diagnose.
